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The water pump is a crucial component that ensures the engine operates at an optimum temperature continuously. It prevents the engine from overheating by circulating the coolant between the engine and radiator. It is necessary to use a durable and efficient water pump in heavy-duty vehicles due to high temperatures and long-term use. VADEN ORIGINAL offers high-quality and long-lasting water pumps for heavy-duty engines.
Understanding motors and their workings requires an in-depth knowledge of their components; one of the significant components of an engine is the water pump. In simple terms, a water pump is a device that pumps coolant from the radiator into the engine and back to the radiator. Untold problems can arise when a water pump becomes defective. A water pump that has a leak, worn bearings, or defective seals can result in serious engine problems. In fact, if a defective pump is not replaced, the sealing area between the engine and the water pump can be so badly eroded that a new water pump will not fit correctly.
The water pump works very hard, especially compared to the rest of the cooling system. The water pump rotates thousands of times an hour but is turning very hot coolant, and this can be only partially cooled by the radiator while the engine is running. So it is designed to last for many miles, but it is subjected to a very extreme environment that can wear it out prematurely. It has to tolerate very high temperatures, and can be subjected to dirt, debris, and even the wrong coolant. In modern vehicles, it's not uncommon at all for a water pump to wear out long before its expected lifespan. That is one of the reasons why mechanics will recommend replacing many engine parts as a set when they fail; doing it at the same time can help avoid repeated labor charges and high-cost repairs. For example, if you're getting a new timing belt, it's a good idea to replace the water pump at the same time. The coolant can actually get very dirty and abrasive too, and that can literally grind down the pump vanes.
Water pumps are responsible for cooling the engine. In a normal setup, the radiator cools the coolant while it passes through the radiator. The cool coolant passes through the engine and absorbs the engine heat and carries it back to the top of the radiator. In order to maintain this flow, a water pump is needed. The water pump pushes the warm coolant from the engine back to the radiator and creates a vacuum or suction at the outlet side. The coolant is drawn into the water pump to be pushed back into the radiator. This cycle continues as long as the engine runs. Water pumps are typically either mechanical or electric.
Mechanical water pumps are driven by the engine via a belt and pulley system. Water flow is directly related to engine speed. If the engine is cold and running at idle speed, the water pump will move only a small quantity of coolant. If the engine is hot, steam will build up, pressurizing the system and preventing circulation until the water is boiling. If you overheat a fraction of the engine so it produces steam while the rest is working fine, it won't be able to get rid of that heat. That's why, on some competition engines, people use an adjustable water pump drive to increase flow when the water is too hot and reduce flow at idle speed.
Electric water pumps are controlled directly by the engine temperature so that water circulation is at its maximum at all times, which prevents localized overheating of the cylinder head area, even at idle speed. The downside is that, on some applications, they can draw a lot of current and if installed on a race engine, they rely on the battery. If the battery dies, the pump stops, and you'll be left with an overheating engine.
Water pumps have been used in internal combustion engines for many years to provide cooling to engine components. Water pumps can be mechanical or electrical. For most of automotive history, mechanical pumps were the first choice. The development of smaller and more efficient electric motors as well as electrical networks with higher carrying capacities has made virtually the entire control of automobile functions possible. In spite of this, the mechanical pump is still used in most models. In fact, mechanical pumps are started and driven directly from the crankshaft pulley through a belt. As the engine speed increases, so does the speed of the water pump. Thus, at high engine speeds the capacity of the mechanical water pump is increased just when it is needed.
The water circulation system of the automobile was the first automotive system to use an accessory belt to drive it. The first cooling systems used belt driven mechanical pumps. A few years later, when the offset crankshaft became popular, it was not convenient to mount the pump on the block. The pump was driven from a pulley mounted on the end of the crankshaft, over a large belt driven from the crankshaft pulley. The development of small, efficient electric motors made the development of electric water pumps relatively simple. While several electric pump designs were tried, only the small motor mounted under the bumper has become popular.
Mechanical water pumps are commercially available as standard, high flow, high temperature, heavy duty racing, light weight racing, and electric water pumps. Most of the water pumps on sale for street use mount where the radiator upper hose enter the intake manifold. Standard water pumps are offered for 1100-2,200cc engines. Leading engines of worldwide manufacture generally have oversquare cylinder characteristics.
Electric water pumps are autonomous components. They do not need to be driven by the crankshaft pulley by means of a belt. Their rotation speed is electronically controlled with an open/closed loop control. This allows their performance to be matched to different hydraulic demands. Since they can be switched off at times of low coolant flow demand, they are contributing to fuel consumption savings. Electric water pumps are especially advantageous on hybrids, which require the electric pump to keep running while the internal combustion engine is off. Vehicle manufacturers have developed new strategies to use electric water pumps in combination with mechanical pumps. For example, at high vehicle speeds, the electric pump, operated at high rpm, can supply the increased coolant demand, reducing the size of the mechanical pump and the weight, which is a positive for the entire vehicle mass. This strategy is applied to hybrids craving for mass reduction.
In the area of conventional combustion engine vehicles, the electric pumps reduce the size of the mechanical pumps, optimize the pulley ratio, reduce the weight, reduce the mechanical power losses. The demand for electric water pumps will continue increasing, not only in conventional vehicles, but also in electric and hybrid vehicles. The range of application of electric water pumps will increase, as for example in direct injected gasoline engines cooling during extreme heating operation, bypass cooling.
In the automotive industry, the conventional water pump is still one of the most reliable hardware components of an engine cooling system. However, as fuel consumption and emissions become more stringent, manufacturers are trying to reduce accessory load during cruising to improve brake thermal efficiency. Conventional constant speed water pumps are able to maintain coolant temperature only during engine warming up. The water circulation rate that is determined by pump characteristic curves and pressure loss curves does not always make a corresponding contribution to engine cooling performance. Under warmed-up engine conditions, which takes most of the engine operations, it is sometimes too large or too small for vehicle cooling, in particular at low speed inertia on one hand and engine overheating due to exhaust gas heat generation during high load operations on the other.
For conventional mechanical water pumps, the flow-rate pattern is determined by the pump design specification. It is very difficult to alter this pattern during mechanical pump operation because mechanical pumps are simple hydraulic devices. To overcome this limitation, variable speed water pumps and various devices are proposed. Among these, the impact of variable speed electric water pumps, electronically controlled mechanical bypass water pumps and mechanical pumps with a variable flow-rate mechanism on fuel consumption, exhaust emissions and engine cooling capability has been investigated. The throttle or nozzle incorporated into an engine cooling water circuit has a great influence on engine cooling performance and shows both advantages and disadvantages. Moreover, the electronically actuated water valve provided in the heater circuit forces the engine cooling system to reach operating conditions faster than conventional systems. The control strategy of a heating system using this valve is investigated to minimize fuel consumption during heating.
To manufacture a water pump, nontoxic, anticorrosive materials (which don’t affect fluid positivity) are required. The elements are produced especially from a light-melting alloy, which is poured at high temperature in a specific mold with a form adopted for each pump element. It uses a magnesium or an aluminum alloy. In automotive applications, housing (or pump body) and cover (or back cover) materials use typically combinations of metal with composite materials.
The internal cavity communicates with the vehicle engine via specific holes (or internal waterways) or the combustion products flow along the cavity walls, cooling them by high thermal conductivity of the water, around 1.1 W/mºC. This ensures the necessary circulation and exchange of liquid. The number and volume of these holes are determined by using appropriate software.
A water pump impeller can be of various designs. Its form and the positioning of its preshaped blades influence the pump yield on the right engine revolutions. Different applications require different numbers and layouts of preshaped blades; for some applications, the use of pumps for indirect propulsion is required. In automotive applications, impeller disc materials are usually a polymer or plastic, whereas blades can be of different combinations of composites, magnesite alloy, aluminum alloy, plastic-filled polymers, or polymer mass. Another alternative solution is an injected thermosetting polymer without any fillers, which is also popular especially for diesel engine applications. Even if a bushing bearing is rarely used, pumps are possible with it. In most cases, sealed hydrodynamic profiles of the bushes ensure the low hydraulic losses, which modify fluid flow on a journal surface. Additionally, the volume of the excess lost heat is less and temperatures lower, which allows pump operation with reduced ice within a microfilm.
3.1. Pump Housing Materials Vehicle cooling systems are subject to an interplay of many different design considerations, all of which affect the selection of coolant pump housing materials. These considerations include design life, resistance to corrosion, erosion, cavitation, and galling. The housing material also affects performance, definition of the pump housing package, thermal conductivity, stiffness, and weight. The housing package is defined as the pump housing including any internal ribs or brackets to permit bolt and water seal mounting of the pump to the block or to the engine front accessory drive housing. Construction of the pump housing directly affects initial coolant flow and flow stability at the inference of vehicle speed and load applied to the engine. The material for the pump housing described in this chapter is assumed to be the pump housing only and must include both its internal flat surfaces that form the pump housing and its outer flanges, brackets, or ribs that apply to due mounting bolt holes.
Other considerations include effects of end-use markets, final functionality, and cooling system performance. Employee skills, manufacturing cycle, tooling, and quality assurance procedures can also be part of the final material selection key decision process. The various primary materials used to fabricate coolant pump housings are gray cast iron, aluminum alloys, zinc die-cast alloys, and polymeric composites and resins, plastic metallized coatings. Several aluminum/cast materials, bonding coatings, various plastic bond coatings, and other thermoplastic adhesives and interface treating coating solutions have also been or are being utilized experimentally to adapt plastic pump housing easily onto the pump housing engine block portals. Each of these materials has advantages and disadvantages that affect their practical use in any one engine's coolant pump or in most vehicle cooling systems in general.
The flow of coolant through the engine cooling system must be uniform and thorough, leading to the assessment of the ability of the pump to generate adequate flow, over a wide range of speeds. The impeller has a major influence on pump performance. Consideration of its design and adaptability for various types of engine cooling systems begins with a description of coolant flow through the pump. The draining of fluid from the cylinder heads drags subcooled fluid from the pump inlet and forces it to flow through the impeller vanes. When flow reaches the tip of the vanes, it must change direction and travel radially outward, exiting the impeller vanes into the space enclosed by the pump casing. The pressure in this space, known as the rim radius, is positive so that work is performed on the fluid, raising its pressure at constant volume.
The speed at which the impeller rotates must move the fluid toward the rim radius and through the pump, compensating for this slip induced by pressure differences. The energy loss in the past two processes as compared to the energy put into the fluid in exiting the impeller raises questions as to whether or not the impeller vanes should efficiently transport the fluid from inside the pump to the casing. The latter raises the issue of how successful a high dam, or design with a high hub radius/impeller radius ratio might be in forcing fluid through the pump without slip. Since centrifugal pump design evolved in a fluid driven by vapor pressure, high hub ratios are not feasible for centrifugal engine water pumps.
An internal combustion engine needs to operate at an optimum temperature because both excessively high and excessively low engine temperatures can be harmful. An efficiently functioning cooling system is necessary to regulate engine temperature and promote engine longevity. The major components of a cooling system include the coolant, water pump, radiator, thermostat, hoses, and engine block passages. The two most commonly used cooling systems are liquid and air. A liquid cooling system employs a coolant, usually a mixture of water and antifreeze, to absorb heat from the engine. This heat is dissipated into the atmosphere through a radiator. The liquid cooling system is more effective than air cooling. However, the cost of a liquid cooling system is more than that of an air cooling system, and the design is more complicated. Moreover, liquid cooling systems can leak, which may cause engine damage. Air cooled engines are also modified with ducts or fan systems to help cool the engine. They are generally smaller, more efficient, and lighter than liquid cooled engines. They are mostly used for small utility engines, motorcycles, and some automotive engines.
The purpose of the cooling system is to remove heat from the engine cylinder and cylinder head, combustion chamber, intake manifold, exhaust manifold, valve springs, and piston. The combustion of fuel to produce power generates a lot of heat. Some of this heat escapes through the exhaust gases. The rest of the heat is absorbed by the engine, and if not removed, the engine components would melt and fail. The cooling system maintains the engine temperature in the range of 200–225 °F for efficient operation. Additionally, engine temperature is maintained within the normal operating range during startup. The cooling system circulates the engine oil, lubricating the bearings, piston, and valve train.
When internal combustion engines work, they produce heat. However, if this heat dissipation is disrupted, the engine's performance will plummet. The cooling system's goal is to maintain the temperature of the engine as close to the optimal temperature as possible, within the limits indicated by the manufacturer.
Engine components such as the cylinders, pistons, and valves burn fuel, creating heat at high temperatures. If it isn't eliminated, it could cause the melting of pistons and valves, seal destruction, excessive wear, and consequently, the loss of functioning of some engine components. However, not all of the heat is eliminated. About 25% of the heat generated retains in the oil, also essential for the wear control of the moving engine components.
The heat that is insoluble to the lubricant oil has to be eliminated by the fluid that is in the channels of the block and cylinder heads and that circulates rapidly throughout the engine. This fluid is the water (or water mixed with antifreeze) that is in the cooling system of the vehicle. Other components also have to act, such as the oil, when in these localizations, as the cylinder head and valve seats, the temperature can preclude the combustion process and the cooling system oil - water mixture, which is mainly responsible for exchanging heat.
In addition, thermostats and shunt valves control the fluid flows in the internal engine cooling channels, so the coolest water can be used for draining the excess heat from the cylinder heads, where the operating temperatures are greater.
The power generated in an internal combustion engine is primarily converted into heat. While some amount of thermal energy is dissipated into the surrounding atmosphere by means of exhaust gases, a majority of the heat flows into engine components. Such heat transfer to engine parts raises their temperature to unacceptable levels, which can cause damage and reduce engine life. In order to maintain satisfactory operating temperatures, the heat flowing into engine parts must be continuously removed. The power transferred away by the cooling system can then be multiplied by the combustion time frequency to obtain the power produced which has to be removed. As the combustion time frequency is usually approximately 70 times the engine speed, the capacity of the cooling system must be large enough to deal with the high energy removal requirements of the vehicular engine.
The major components of the cooling system are the coolant pump, which forces the coolant to circulate, the radiator which dissipates heat into the atmosphere, the coolant, either air or liquid which transfers heat from the engine to the radiator, the hoses which transport the coolant, and the thermostats which control the flow of the coolant. For most automobile engines, the liquid is water or a water-antifreeze mixture with the antifreeze used to prevent freezing and also to reduce corrosion. In large vehicle engines, air is commonly the coolant.
5.1. Pump Activation Mechanisms
It is by now sarcasm to state that coolant temperature variations depend primarily on the thermal load conditions of the ICE. However, in order to understand coolant flow rate dynamics, it is necessary to go into more detail concerning the causes of the activation and variations in the cooling circuit thermal loads. Today, the basic mechanism for activating the water pump is the micro-vibration of the engine crankshaft resulting from the firing; the thermal load on the circuit is activated and may increase during the acceleration phase and reach a maximum at full load. It is clear that coupling the flow rate and thermal load conditions cannot take any particular shape, but can only be defined at the limit. Other occasional peaks of smaller flow rate duration may occur during the normal ICE running levels. However, these must always be evaluated to determine whether they compensate for the tonally higher flow rates associated with micro-vibrations.
5.2. Flow Rate Dynamics
At the microvariation engine speed of less than ten times per second, the pump, with an acceleration head generally of the order of two times and more the pneumatic head, will not create greater pressure losses in the engine circuit and therefore neither greater increased coolant flow nor pumping losses in the engine idle circuit. The relative dynamic combined with the elastohydrodynamic that occurs during the variation of the outlet connections determines, for a defined operating point of the crankshaft, a maximum value of the elasticity thus defined. Up to the low-speed driving areas with low or zero flow demand, the pump with negative incidence behaves as an inverted mechanical work turbine. The gas exchange will be more and more effective for air–coolant heat exchange during activation time.
The system that drives the pump can be classified as follows. – Mechanical Activation: The mechanical drive of the pump is composed of a mechanical belt and a gear to distribute the power coming from the engine. In this type of system, the flow generated by the pump is somehow related to the engine speed; in fact, the higher the engine speed, the higher the flow pumped at any operating condition. – Electro-Mechanical Activation: The advantage of this type of system is that it is possible to control the pump flow according to the engine’s real thermal and operative requests. In this type of flow control with the pump, the power during transitory is need to be modulated, generating a programmed increase or decrease without exceeding a predetermined value. This allows avoiding blockage dynamic increase or any induced thermal anisotropy without losses attributed to now cooling normalized conditions. Mechanically, all the solutions proposed are based on two different families: – The solution rotates toward the variation of the internal elastically stressed or modal motion itself of the pump; – The solution rotates toward the variation in the distance between the driving shaft and the terminal shaft of the pump. – Hydraulic Activation: The drive of the pump flow is controlled by the hydraulic differential pressure between the flow going into the pump and the flow coming out of the pump. In this type of system which enables the modulation of the pump flow at any thermal request or power requested by the engine, a big potentiality depends on how the valve is controlled for the variation of the differential hydraulic pressure.
The volumetric flow rate of engine coolant through the pump and used to cool the engine depends both upon pump design and performance, as well as that of the overall engine cooling circuit. On the design side, the total area of flow passage through the pump is small, which limits maximum flow rate for a given pressure difference across the pump. Speed of the engine generally defines maximum flow rate. Pump performance, and hence the volumetric flow rate at the engine cooling circuit demand, is essentially a characteristic of the pump. To provide satisfactory cooling, the pump must increase flow in a nearly proportional manner with an increase in engine cooling load, but cannot be allowed to exceed flow dependence of the engine cooling load. If pump flow exceeds cooling load demand, then the heat transfer will not be enhanced and ineffective circulation losses will occur.
This flow development is determined by the flow area and speed of the pump, and circuits depend upon the cooling load and thermal characteristics of the overall cooling system. The pressure drop across the pump encompasses the resistance to flow due to the speed of the liquid entering the pump, as well as the resistance across the pump and pipe itself. The control volume enclosed generally includes the entire pump and pipe to the radiator inlet. The energy balance consists of specific heat from the inlet to pump discharge temperature, as well as the compressibility and kinetic energy terms. Use of the zero kinetic energy approximation eliminates the kinetic energy term from the right-hand side; however, it can be evaluated while iterating on the location of outlet temperature.
Only with an efficient operation of the engine temperature can the engine be exposed to the possible working conditions and meet the required performance. The cooling system is responsible for a good temperature regulation of the engine. Distant from that objective, the engine will neither meet the working conditions nor perform with good efficiency. The engine cooling system meets both conditions of long engine life and good performance of the motor vehicle, reflecting a big impact on engine performance. Both conditions are interdependent. An excessive engine temperature increases wear in the cylinder-head and inhibits the clearance between components, leading to excessive load, increased wear, and a quick decline of efficiency, along with high specific fuel consumption. In opposition to that, a reduced engine temperature increases the viscosity of the oil and fuel, leading to a decline in the oil lubricating properties and incomplete burning of the fuel-injected. Both problems could increase smoke emission.
Due to the importance of controlling engine temperature, many studies utilize different simulation methods to analyze the impact of the cooling system on engine performance. A procedure based on a thermal network analysis was developed to predict the impact of the cooling water circuit layout on steady-state engine temperature, operational stability, and heat flow rate from the cylinder head and engine block. The results show the importance of optimizing the cooling system layout to prevent excessive temperature. Also, consistent with the study shown, it was demonstrated that tight tolerances at the boundaries between the cylinder head and block, as well as a simpler design of the cylinder head may be important to allow the thermal flow pattern of the cooling system to promote lowering mean engine temperatures. On the other hand, a model was developed to investigate the impact of the cooling system outlet flow and heat rejection load on engine performance, showing that higher heat rejection values would increase fuel consumption.
There are many reasons to cool the engine and run it at a certain temperature: it permits the combustion of low-grade fuel, it prevents excessive emissivity at the cylinder walls, it increases engine efficiency, it increases the engine lifespan, it allows the use of light engine-weight materials as alloyed aluminum for engine blocks and cylinder liners. However, to be fully compliant with health and emissions regulations, engines have to run as hot as possible. It is a heavy industry cycling from burning temperatures to chilling shock. The cyclengine, in a controlled way, creates energies and flows that decrease component temperatures and exhaust gases while increasing combustion gases. Coolant pumps take a bunch of those gases — and they are a minor number normally — to clean the act.
The cooling system is composed of the following subsystems: Fan: operates within the system or is driven by the vehicle’s movement. Fan Belt: connects and transmits the engine motion to the fan. Radiator: dissipates the heat into the atmosphere. Coolant Reservoir: regulates the coolant system pressure. Water Pump: carries the coolant into the engine. Thermostat Valve: regulates the coolant valve into the engine. Hoses: transport the liquid coolant between the pump, radiator, and engine. Pressure Cap: seals the forced-circulation whole system and controls the coolant pressure. Temperature Sensor: monitors coolant temperature and sends the engine data to the user. Thermostat Valves: regulate bypass cooling liquid flow, thus regulating the time the engine takes to reach operating temperature. By-pass tube: takes the cooling liquid around the radiator on cold-start.
The automobile has undergone a significant transformation over the past century, changing the face of the world as we know it today. Engine cooling is one of the widest fields of the internal combustion engine. The internal combustion engine's performance has always been dependent on the balance between heat losses and the recoverable work produced. Decreasing engine heat losses is aimed at decreasing the risk of overheating engine commercial versions during their long usage at high ambient temperatures. Working condition at high engine temperature worries not only cooling efficiency, but also requires an increase in the volumetric compression ratio and examination of combustion instability. At fuel economy, higher compression ratio reduces the fuel amount burned during the time of combustion. But it increases the combustion temperature, and consequently, increases also engine pollution – oxides of nitrogen and soot. The higher working pressure causes engine component wear, reducing engine efficiency, which induces shortening of the mileage before causing average consumption. The air fuel burned during one period may be expressed in terms of air fuel ratio and the amount of air from the equation of ideal gas. Mixture R with the value of around 14 to 15 increases engine efficiency, which requires further decreasing pollution as a cause of engine cooling. Decreasing the internal and external heat exchanges must decrease those losses to increase engine efficiency.
Vehicle cooling system problems are commonly linked to the following water pump concerns: leaks, bearing failures, and impeller damage. While the primary task of a water pump is to move coolant throughout the cooling system to prevent engine overheating, they are designed to operate under very strict parameters. Failures of such magnitude that would bring the water pump to a halt are unusual to contemplate but actively cause some of the engine's most devastating and expensive concerns. Water pump leakage problems may be external, with fluid dripping off the mounting bracket, or internal, allowing coolant to flow through the water pump's bearings and mingle with the engine oil. Given the relatively low cost of replacing water pumps whenever replacing a timing belt, it is generally advisable to inspect the water pump's ease of movement and tendency to leak, or have it replaced, whenever any major engine service is performed. Forcing high speed coolant through the water pump when the thermostat is open, and for long periods through a clean system once the engine is warm, may help dislodge debris affecting the water pump's performance.
Water pump failings are implicated when there is no coolant flow apparent in the radiator after testing the thermostat and there is no external leak present. Bearing wear is generally a function of the water pump's internal design, the quality of the part used, belt tensioning, and the amount of wear on the water pump's shaft. Creep through the water pump gasket surface is an indication of probable bearing wear, perhaps exacerbated by lack of appropriate quality lubricant in the oil system, especially on engines that have a history of excessive idling. Debris inside the coolant system or physical abuse may lead to impeller wear, especially on non-slip nylon impellers.
Cooling system leakage can occur at various points in the system, among them the radiator, heater core or hoses. When leakage occurs in the areas of the water pump, sufficient pressure is no longer present to push the coolant through the system, thereby allowing the water pump to leak coolant externally through the weep hole. Consequently with a loss of coolant and resulting build-up of heat, accompanied by a loss of pressure, the possibility of volumetric inefficiency due to cavitation occurs. Additionally, the closed system is designed to operate at increasingly higher coolant pressures, making gasket and hose integrity an important aspect of operation and coolant pump design.
Powered by compression seals and gaskets, the latter maintain pressure by circumferentially hugging the installed component to the appropriate surface, utilizing a compressible material or special fabric + rubber coating interfaces. The amount of leak-free eccentricity is limited, such that when this clearance exceeds approximately 0.001 in., leakage can occur. Leaking water pumps are a fact of life. Hence, the need for devices to contain that leakage is essential, either in the form of a road draft to prevent pollutant entry to the circulating air, disposal to the atmosphere, disposal to a drain pan under the vehicle or collection of the pollutant in either in the form of a one-way valve that drains to the atmosphere in a controlled manner or returns the fluid to the cooling system to repeat the cycle.
The bearings used in engine water pumps are both small and numerous. In some designs, the bearings are pressed into the housing, while in others the bearings and seal assemblies are sold in lube-encased cartridges. When the lube fails or the carousel is pushed beyond its threshold of hardness because of excessive speeds or road stresses, the components and shaft typically begin to wobble. As they do, whatever or whoever is in proximity will begin to suffer from the vibrations; typically it is the supporting housing that develops a crack, allowing coolant to escape. But before external leakage occurs, the normal flow of fluid across the seal area may be misguided, allowing some leaking to develop.
The wobbling motion, as in the unavailability of support, will produce uneven contact between the bearing surfaces, resulting in localized heating and premature metal-to-metal wear. Additionally, when uneven motion occurs on two surfaces, some friction is incurred, generating heat. With the lube, that is, coolant, eventually lost, there is no system to remove that heat, and it will continue to rise until ultimately the metal is soft-melted because of the temperature, mechanical loads, and time.
Unlike failed ball bearings with circular traces on the shaft, or worse with steel rolling away damaging everything in close vicinity, water pumps have soft mechanical components limited in size and hardness due to duties defined by the engine's thermal and physical limitations. Instead, with water pumps you are essentially talking rubber bands, based on the lube system, stretched on a type of bearing over relatively small areas. As more stress is allowed to accumulate, the rubber band continues to stretch, resulting in ever more severe deflections and size reductions until the rubber band fractures, with or without the shaft being damaged or the pump mounting location cracking.
The most common form of pump impeller damage is cavitation. Palette or slot cavitation occurs where the differences between pressure inside the pump and pressure at the inlet to the pump are greatest, frequently at the shutter blades and front supports of the impeller. Pump slots are usually most badly pitted and eroded at a point about two-thirds of the way out from the center of the impeller. Although this is a sign of cavitation, the pump itself is most likely operating correctly. It is usually a consequence of poor radiator airflow and/or air leaks at the pressure side.
The next type of impeller damage is circumferential erosion on the pressure side of the inlet fins, or vanes, or blades of the pump wheel or impeller. During operation, any abrasive dirt or contaminants in the coolant are flung against the flow channel through the impeller, causing a gradual erosion of the material. Most variable-pitch or twin-pitch wheels suffer this type of damage because, with their wide, open flow channels, there is less clearance for dirt to escape and therefore less cleaning action by the flow. Another form of erosion is abrasive wear on the back face of the wheel, which may also be a sign of a worn water-pump shaft or a misaligned shaft.
Another sign that coolant contaminants are not being filtered out is a buildup of blisters or pitting of the non-pressure side of the impeller blades, or on the machining face, or inside diameter of the boss of non-metal impellers. This type of impeller damage, which is also called bio-deterioration, is caused by an accumulation of organic foreign matter, which is then attacked by microorganisms present in impermeable polymeric materials. These microorganisms cause localized damage, but can also reduce the adhesive bonds, which is several elastic polymers or composites have been of concern in several industries.
An overheating engine, coolant leaks, and unusual noises can signal the failure of your engine's water pump. If your vehicle heats up on a regular drive or gets hotter than normal, you may have a water pump problem. You may naturally assume it is just a bad thermostat, but don't be fooled. A faulty thermostat can close the water passages to the radiator and cause the engine to overheat, but the water passages are still open to the engine. Because the pump may or may not be circulating the coolant, a faulty thermostat is not giving a true diagnosis of temperature. So a proper diagnosis is to replace the thermostat and see if the thermostat corrects the problem. If it doesn't, then one of the reasons the engine is overheating is because the water pump is not pumping. One way to discover this is to touch the heater hoses after the engine is warmed up. If the water pump is pumping, the heater hoses will be hot; if the heater hoses are cold, the water pump is not pumping.
Coolant leaking from the water pump weep hole on the engine's underside or from the gasket mount leads to another sign of water pump failure. The weep hole is intentionally made to allow coolant to come out so the driver can detect that the pump seal is bad, the oil is leaking from the oil pan and into the water, or the oil is leaking from the water passages and into the crankcase. If the oil is leaking and the level in the radiator is low, the oil is leaking externally. If the oil is leaking, and the two levels are rising and falling on the opposite side, then the oil is leaking internally. If oil is leaking internally and is mixing with coolant, the symptoms are an engine smoke screen, and, very shortly, from a fuel consumption standpoint, an emissions check failure.
Unusual noises including a squeal or squeak are also possible signs of pump failure. The squeal may indicate that the pump bearings are bad and the bearings are screaming to be replaced or, even worse, tightened. The squeak can usually be identified by a mechanic's stethoscope to isolate it to the pump; one of the other engine accessories if the noise is a squeal.
An overheating engine is a sign that either a failure has already occurred in the coolant transfer system, or that the system is in a very borderline situation. When the engine heats up correctly, the heat of the block walls is transferred to the coolant – which, in turn, passes heat through the radiator to the ambient air. If the pumping function stops, the coolant is totally stagnant; it doesn’t carry any heat to the radiator. The block walls will overheat, but the coolant will reach boiling temperature. At that point, however, most of the heat is being transferred to the coolant, causing it to vaporize. Once the vaporization phenomenon starts, a closed circuit is formed, since the vapor collects above the level of the liquid mass. Near the walls, where the boiling point is reached, vapor produces little energy transfer; at centerline, where the gas can have a significant flow velocity, it will bring cooled gas to revive the heat transfer in vaporization, to totally uncharge it. The engine will heat a small amount of liquid, and if this effect is significant enough, the melding temperature will never be reached. If the effect is not significant enough, then the block will overheat; it could even distort and crack or melt at the hottest spots.
In extreme conditions, the flow through the block is large enough to avoid the vaporization phenomenon. In these extreme cases, the block material can be insufficient to absorb such a large amount of flow quickly enough; in this case, the problem is not the heat transfer in the circuit, but the effect of the pumped heat and the effect of the absorbed heat in proximity of the walls.
A leaking water pump (or cooling system) can be easier to diagnose than an overheating engine. If you see a puddle under the front of a vehicle after it is parked, this indicates a leaking water pump (or cooling system). Before dismissing it, however, check the location of the leak. If it is dripping from the front of the engine or soaking the inner fender shield, a leaking water pump (or cooling system) is indicated. If the liquid is coming from the area between the rear side of the engine and the bell housing area, it may actually be transmission fluid leaking from the torque converter area.
Water pumps are either driven by a mechanical belt, or are located in an engine designed with a belt driven water pump. Both designs utilize seals and gaskets to retain the coolant fluid in the drain pan. If either should fail, water can leak out into the drain pan. Ordinarily, this is a rare occurrence with a properly maintained vehicle. If you suspect this has happened, or you can see the puddle, have it checked out by your repair professional. If the water pump (or cooling system) leaks, heat exchange will be lost, and engine performance will be affected.
Most often, the water will come from between the engine and the water pump, indicating that the main seal has failed. If this should happen, the water will wind up in the oil system, and the engine will likely be lost. If you allow the oil and fuel system to fill with coolant very long, you will cause severe damage. If your engine requires a water pump replacement, replace the pump and seal and flush the engine before restarting. On very low hours, travel, or miles, you can bond the area with a quality sealant, however, the best solution is replacement.
It seems intuitive, but an operational pump may make several different sounds, from moderate humming to loudly grinding noises. Often, these sounds are indications of any of a number of problems. A loud whining sound is a signal that the pump is operating at a dangerously high speed or that it has inadequate bearings. It may be delivering an inadequate flow or no flow at all. If cooling has been lost, this condition can quickly lead to pump damage, causing vibration and the potential for the casing to seek. Sudden restrictor plate noise from a positive displacement pump may warn that flow control problems have caused momentary thermal damage.
Either a pump or prime mover that emits a high-frequency screech is sending a signal that should not be ignored. The sound is a sign of either mechanical failure in the pump casing or inertia wheel or that a shaft has been geared for too high a speed. A whacking sound coming from the drive motor may signal a coupling or babbash failure, especially if it is associated with excessive vibration in the main motor supports and/or excessive vibration levels in the bearings.
Pump and prime mover units are subjected to vibrations of varying frequencies. Distortion of the supporting structure causes large quantities of high-frequency vibrations. Melodization or periodic changes in the vibration signal can be caused by misalignment, excessive loss of pump capacity, an unbalanced rotating assembly, faulty bearings, or looseness in the foundation or mounting base. Low-frequency vibration can result from a defective electric motor or from mechanical problems associated with the driver, such as electrical unbalance or misalignment.
Because water pump use is generally problem free, basic maintenance consists of waiting for a problem to develop. Water pump failure can lead to overheating, blown gaskets, or worse damage by having hot coolant leak, spray, or spatter onto engine parts. Leaking water pumps, looseness, and noise are the most common symptoms. Water pump inspection is simple. Check for leaks around the shaft seal or seep holes, looseness at the mounting bolts, and noise while the engine is running. Use caution when checking for noise since the engine drive belt can be dangerous while running. Use an automatic tachometer to measure shaft speed and detect a problem if the pump does not turn up to speed. Remove the drive belt while checking for noise, looseness, and palpation. Inspect for leaking hoses at the ends and dampness in the drainage wells. Check for old and brittle belts with hardened edges. Check for misalignment when a belt has worn on one side. Clean and tighten hose comply; near the pump or radiator. Clean and straighten any bent radiator fins. Do not push the fins with your fingers; this can collapse the tubes. Check thermostat action by removing it from the engine. Heat it up at a temperature controlled sub-boiling point container and observe opening flow. Most coolant problems during regular maintenance involve the same few issues as with the cooling system. These issues are physical damage and leakage, fouling, scaling, and corrosion. Coolant should be replaced approximately every 48,000 km. The coolant system needs maintenance when the antifreeze concentration drops. This can be tested with lathe equipment. Corrosion build-up on the inside or outside of the system parts can cause efficient operation problems. The automatic transmission oil cooler can leak at its interfaces with the cooling system. When drained or serviced, check coolant and the oil quality for contamination.
Like most accessories affixed to an engine, an engine water pump must be inspected regularly for soundness and proper functionality. During light duty applications, driving thousands of miles yearly without inspection is dangerous and may lead to negligence damage. If a water pump develops a small external coolant leak, the leak can often be repaired by simply tightening the pump cover bolts. However, if the leak persists and a large quantity of anti-freeze drips or oozes out, the porous metal content of the cover or even the core of the pump may be defective, necessitating replacement of the pumps. In most heavy duty applications, the water pump, along with the radiator, should be inspected during any scheduled service interval. A light spray of water or air from a pressure washer on the front side of the pump can also alert an operator to a coolant leak otherwise undetected. Particular attention should be paid to any excess coolant on the area around the pump shaft, as it would indicate seepage from between the bearings and seals. Periodically inspecting the water temperature on the gauge mounted in the instrument panel can warn of pending problems with the water pump. If there is leakage past the pump shaft or into the bearings via a defective seal, the temperature will be much higher on the opposite side than on the inlet side of the pumps. During any service to the cooling system, the water pump should be inspected closely. Check the coolant condition, ensuring anti-freeze content and pH balance meets service replace criteria. Look for any oily residue in the coolant, indicating pump failure, and inspect the pulley for free play indicating bad bearings. Be sure to lubricate the accessory drive as specified.
The water pump core function is to circulate the engine coolant through the system to remove heat from the engine and release it at the radiator. The coolant absorbs dirt particles as it flows through the passage surrounding the engine. It may react chemically with the engine or water pump. Additives in the coolant help reduce deposits and control pH by neutralizing acids and preventing rust of these metals. Gradually, the additives get consumed as they react with the dirt, heat, and other chemicals in the coolant. If the engine is not using any additives, including those already in the coolant, the coolant gets acidic and no longer prevents rust formation or deposition of contaminants. At this point, the dirty and contaminated coolant can no longer protect the water pump. Inside of the pump begins to deteriorate, and the bearings may also fail. As no lubricant is available, the seals in both ends of the bearing get dry, and the pump starts leaking.
Most vehicle manufacturers specify a coolant replacement interval of every 40,000 to 50,000 miles, but some recommend it at longer intervals. If you plan to keep the vehicle, a reasonable guideline is to use a good quality pre-mixed inorganic acid coolant from a reputable company and replace it every two years. Organic acid technology coolants last longer and can be replaced every four years or 50,000 miles. However, do not confuse premixed organic acid technology engine coolants with that premixed inorganic acid coolant. Some car companies allow an extended interval; follow their recommendation. If you use inorganic acid or organic acid technology coolant, remember to have it changed sooner if the vehicle is used under severe conditions, such as excessive stop-and-go driving or towing.
The water pump is preset to work for the lifetime of the vehicle. Nothing requires draining and cleaning inside or outside since there are no wear parts exposed, but practically nobody would want to drive a car whose engine comfort temperature was 85°C or more. Group Housing with its bearings and cover is also cooled by the coolant being pumped through, which indicates that the rest of the cooling system need to be kept in good condition. But overheating can be caused by the water pump-bearing failure, physical breakage of the pump or if the pump is "frozen" where the coolant is in contact with the pump housing that is dished inward and not "shining". Similarly as with drive belt tensioners, the water pump overheats only in extreme conditions, and the pump is ordinarily replaced together with the timing belt as a precaution. While the timing belt is off, this is the best moment to observe how the water pump is doing.
Since pumps return hot fluid to a high atmosphere-temperature zone, enough energy is collected to produce noise waves that can be detected in the cabin. Most serious manufacturers recommend periodic checking the noise produced by installed water pumps and its replacement in case it exceeds specified values.
Water pumps have been constantly improving year after year, but they might be malfunctioning any time like any motion machines are. The main signs are:
- Visible leakage of coolant outside the pump. - Presence of play in the bearings (very slight axial play is acceptable). - Failure of seals in contact with the pump shaft. - Failure of any of the pump or related parts. - Causative symptoms of overheated coolant in the engine.
When to Replace
Usually when the timing belt is due for replacement, a vehicle will have many more miles on it when a water pump replacement is necessary. Consult your shop for guidelines to see what is best for your particular vehicle. There are indications like bearing noise or play, gasket leaks or water pump failures that require immediate replacement. Additionally, check coolant condition and hoses, which might impact timing belt overheating are possible during periodic service or inspection.
Usually water pumps do not burn out and they either "freeze", or the bearings allow so much play that rotation causes wear of the attachment holes which disturbs the fluid seal, or they do not comply with the cooling system operation mode, or mechanical problems disturb operation. In any of those cases external leaks would be shown via oval, ugly, followed by macro-cracks appearance on the housing or cover. In the last case, "squeezing" one or more cracks and absence of leakage while the pump is running, putting a band aid on the initial end of the crack while running or retaining liquid used for metal repair might temporarily solve the problem. Crack-checking could be done with cold scratches and visible particles.
The engine water pump is a part that, like many others, has a service life. Accumulated shop time and the aging of its components, especially the seals and ball bearings, will conspire to force a replacement. Although the water pump is a little more difficult to access than most other components in the belt system, it is not prohibitively difficult to include in a belt replacement, and it is smart money to do so. Depending on the engine, belt changes come around every 60,000 - 100,000 miles, and water pump service is normally in that same zone. Changing the pump at that time simply eliminates the potential of further work down the road that, still again depending on the engine, could be significantly more expensive due to more labor time, as well as the cost of cooling system components, coolant, and the possibility of engine overheating damage.
Of course, a pump may fail in between service intervals, and there are signs of trouble to look for if the pump is original or if it is in a non-service replacement interval. As an initial point, if age, mileage, and a history of pump replacement do not indicate a near-term replacement, yet the pump shows these signs, this is enough ground for replacement. The means of failure of a water pump are either internal or external. Both types of failure may be indicated by a coolant leak, shown as a stain on the pump exterior, a drip, or a pool under the pump. The pump is considered to have an external leak if a thin stream of cooling fluid is coming out of the weep hole, and the pump bearings are failing due to worn seals left to leak over time.
The water pump replacement job must be considered carefully. If the pump is underground, it is advisable to check the gaskets and the casing of the whole system. If the pump is above ground, while the pressure is removed from the whole circuit, check the pump bolts to see whether they are loose or missing. Check too the bolt’s tightness of the pump’s casing. In a general context, the upper part will be checked visibly, where a lack of tightness is easily seen. From below, where a little water has dripped, there will be no doubting either. If it is leak-riddled, it will need changing. If the pump, idle during the summer, has produced cracks when starting up the machine at low temperatures, there will be no signs from above, and you will have to take a chance, testing low-pressure tightness on the circuit.
Generally, a pump that has had water filtering through and has been enjoying five or six years’ service should be replaced to stop the next driver arriving in tow. We won’t just bemuse “trusting luck”, we’ll also check - when driving with the water’s boiling point not at all near, either with a water thermometer or feeling with our fingers because we get burnt - whether the radiator is hotter than the pump. The pump should drag the water into the engine, and the hotter side should be the engine’s. If at low speed, and the levies of the thermostat are at the appropriate positions, if we notice that the probe or fingers are hotter at the inlet — the one entering from the cylinder block — this shows that there is boiling in the intake area. We cannot be crossed with only one vehicle in this long mission, if we suffer a leak from the junction of the pump to the iron casing, it’s a bad idea to resort to mastic or sealant to solve this little thing. When repairing, it should always be replaced by new rubber gaskets.
Increased fuel costs affecting our lives so much are likely to fuel, in addition to prices on all goods and services, an increasing demand for better fuel economy in some markets. Warnings on fuel costs are becoming the order of the day. This situation is pushing the auto industry toward ever better fuel economy. One of the means for improving fuel economy is the optimization of every vehicle component. By optimizing the water pump in a vehicle engine, a large effect on vehicle fuel economy can be obtained for very little additional cost in both item cost and assembly cost, as either of these is now not increased. Research indicates that every one-horsepower reduction in hydraulic horsepower losses results in a 2 percent improvement in fuel economy. In addition, hydraulic losses have been attributed to be 4 percent of the low-speed fuel consumption for medium-duty diesels. It is believed that similar hydraulic losses and fuel economy influence exist for light-duty engines.
The water pump is driven by the engine, and frictional and hydraulic losses result. Because the water pump creates a negative pressure in the engine cooling system, actual horsepower losses large enough to influence fuel economy are generated by the braking effect of the viscous shear forces in the water pump at the low engine speeds. Viscosity is temperature dependent: The greater the oil temperature, the lower the viscosity. At high temperatures, the energy required for pumping decreases to a value less than that for the respective diesel or gasoline engine. It is this action that gives potential fuel economy savings with the other engines.
A water pump is a device incorporated in all water-cooled internal combustion engines, being responsible for transporting the cooling liquid through the engine circuits, allowing it to reach the right temperature as soon as possible, and maintaining it in such conditions. This mandatory use of the water pump influences fuel combustion in two ways. The first is directly related to the water pump when its performance is not appropriate or proper because of some fault. Such failure could consist of the presence of defective bearings, excessive or low tightness of the impeller in relation to the pump cover, cavitations caused by the low cooling liquid flow rate or poor water pump capacity due to wear or corrosion of the impeller. Such failures would lead to a high increase in fuel consumption, from 3 to 30% or more, depending on the speed, load, and air-fuel mixture rich relation, which means high thermal stress and cooling liquid temperature difference in the inlet and outlet of the engine circuits. Such increase in fuel consumption would occur due to poor engine efficiency, since operating conditions where the failure occurred would be inappropriate for the compression ratio of the mixture. System losses are, however, a secondary cause, since it consists of internal losses associated with too low performance of the water pump. Such losses have an opposite effect on fuel consumption: they would decrease it. This behavior occurs in the most favorable condition for the engine cooling system, i.e. when the temperature difference between intake and outlet of the engine cooling circuits is the lowest. In this situation, the vehicles with water-cooled engines would have their performance increased compared to those with air-cooled engines.
The pumping power also follows a trend with engine power; however, potential conflict exists, as fuel consumption can be improved by reducing pump speed. During the evaporative phase, more latent heat of vaporization has to be removed from the pumped water and recycled to the engine to achieve better performance. This means that a minimum orifice pump volume must be maintained against an increasing vehicle speed; otherwise, additional pressure energy has to be supplied again to the pumping circuit to safeguard adequate cooling at high pumping power ratios. During the cooling operation, this is implemented by valves in a fixed or temporary circuit splitting of the installer, as we also learned with regard to the reduced need for vehicle cabin heating in warm climate zones. Then pressure drops must be allowed to exceed a defined threshold corresponding to a minimum cooling effect needed.
Such phase-corrected splitting can also function in the opposite direction. Optimizing control of cooling circuits in terms of fuel consumption is an essential topic, although we cannot suggest a practical solution that balances heat and flow rates to ensure the correct timer not too long, with the circulation by excess heat, especially of fuel-rich mixtures given away. Its change with the increasing exhaust or engine block wood temperature, when it would have cooled could be interesting and sensibly proposed. Modern advanced driving assistance systems influence the time structure of PTC operation, as they can anticipate the vehicle speed as a function of time taking into account the previously selected navigation route. This allows smoothing and optimizing the load distribution to pump-free and difficult conditions such as estate driving that can lead to short-load phase overheating.
The internal design of engine water pumps has changed little over the years. What have changed recently are the external designs. There are a number of innovations on and in the disi engine's belt driven water pump that have recently crossed over from the world of passenger vehicles. Some of these are now being fitted to light and heavy commercial vehicles, utility vehicles and heavy earth moving equipment. They are worth mentioning because they address some of the present and future water pump downsides presently faced by vehicle makers.
The first trend is in what has become known as smart pumps. Basically, an electric motor drives the impeller. The water pump is controlled entirely by the engine management system. This leads to two additional benefits. One is that there is less stress on the engine. The other is that the pump can be used to provide cabin heat on a cold day and for some other auxiliary heating on a hot day. The electric drive motor can connect directly to the car's main battery or to an auxiliary battery that's being recharged by the vehicle's charging system.
Another recent trend is the integration of the water pump with the engine management system. Engineers from software makers and pump manufacturers are working together on algorithms aimed at improving coolant flow rates and decreasing parasitic losses, often by matching pump flow to the cooling system's real-time requirements. These multi-company alliances are also developing new designs and operating strategies for the pumps found in conventional cars and light-truck fuel-efficient gasoline engines, as well as for gasoline and diesel engines found in commercial and industrial machinery.
Advancements in ICT and mechanical adequacy have made possible the development of smart products for several applications. Smart Water Pumps (SWPs) are equipped with sensors that monitor temperature, flow rate, pressure, and vibrations, sending data to a cloud platform that processes fault-alerting information allowing predictive maintenance. The SWPs are actuators integrated into the vehicle thermal model application and vehicle power management and load point prediction systems. In their control strategy, their water flow and exit water temperature are controlled instead of a more energy-efficient temperature based on the thermal model. SWPs can take into account cooling capacity ensuring a maintained engine temperature and also validate water temperature estimations made by the vehicle model.
The main-plumber SWPs work mechanism to provide flow for a determined water pressure is the mechanical belt transmission from the engine crankshaft speed. Their operational features are highly sensitive to the operational conditions due to the vehicle’s variable speed of movement: When the engine is running at idle and at low car speed in heavy city traffic, the speed ratio is very important, the cooling capacity and heat reduction are very small, while for the external environment conditions may be very critical; On the other hand, when the car speed and the engine speed increase, the ratio is far below the one-variation, even negative, which can lead at high cooling capacity or even thermal shock to engine parts due to sudden occurs of the coolant temperature. The control strategy of the usual main-plumber Water Pumps is not adapted for the variation of the vehicle thermal model parameters.
The external controllers used in the majority of the smart water pumps currently available in the market use a Time and Voltage Control command signal onset from the car battery. These controllers are primarily designed for testing in the lab/initial validation phases by the pump manufacturers. Such external controllers are not compliant and manufacturers have shown a great interest in developing their pumps with integrated Electronic Speed Controller supplied from inside the car. Such an approach would allow the pump manufacturers to build a new range of intelligent pumps able to regulate and optimize the flow conditions according to the vehicle conditions. Moreover, the used generally in the manufacturing industry for Electric Water Pumps are chunky and expensive architectures that increase both the complexity and the cost of the solution. This chapter presents Case Study 1: The EWP HiTech developed by a company that conforms to the state of the art external controller solution.
The pump will be used and, as such, need to be powered in a more intelligent way. The next section of this chapter presents Case Study 2; the EWP Nauta that integrates and integrates the pump’s control. The pump is a smart pump able to offer two flow algorithms: the first one supersedes the problem of the pump being used outside its range of flow conditions and contradicts its water-to-water temperature difference. The second algorithm offers a temperature difference regulation based on the feedback coming from and the conduction command signals outcoming. Both algorithms are selected by an integrated circuit mainly designed for the automotive market that provides several means of connection between the state of the art component and the internal Electronic Control Unit.
This paper presented various experimental studies that were designed to explore the potential of using electric water pumps for the coolant circulation in vehicle thermal management concepts. Depending on the electric water pump type, different operating modes were evaluated for the water circuit thermal management concept. First, performance evaluations were performed in a PC vehicle in repeated driving cycles to assess current consumption and have access to early indications for possible fuel consumption reduction. The advantages were shown for a particular range of test conditions, supported by further temperature sensor measurements in critical cooling system locations. Then, to move further up to operational temperatures, a fuel consumption analysis was performed with an early prototype for a PHEV City Car. Different thermal management concepts were again tested based on a particular electric water pump configuration, and promises were revealed for the more complex active thermal management concept, considering the early integration into the new car.
Long-term subject to sign-off, additional experimental studies were performed to validate the concept at prototype and preproduction EWPs for a mild-hybrid application in a luxury car. Here, different vehicle designs launched in the market were compared in a long-term operational analysis regarding condensation monitoring. Significant advantages were explained by the observed differences in condensation time circuits. The more powerful electric water pumps allow for much better system tuning, leading to lower condensation time and better components reliability.
Performance analysis of the EWP system was observed in a test vehicle and special development vehicles. EWP was first implemented and tested in a small, lightweight, 2.8L engine, front wheel drive vehicle. Subsequent to this initial trial, the EWP system was later installed in a vehicle equipped with a 4.0L V6 and 5.0L V8 engine. With the truck EWP system being made available for use. Test procedures and results from previous systems have been briefed with more detail included in the following sections. As expected, the performance gain with the EWP system is much greater with the small 4-banger than the large and heavy trucks, somewhat offsetting the performance dropoff developing into the extremes of EWP control. The reduced performance of the EWP system in heavy vehicle duty is minimized when the EWP operation is allowed to fade longer for EWP control set, as with the truck system and this control philosophy is acceptable.
Electric water pumps were developed as thermal engine development became faster paced and additional function outputs were added to production roadmap efforts. The electric water pump is key in success of advanced engine programs allowing short duration engine tests yet meeting critical emissions requirements. Another important performance aspect of EWP in vehicles was to support transient tests on WOT operation above stoichiometric with a fast acting, short duration catalytic converter bypass. Care was taken to develop blowdown designs that would not restrict FGT even with electric water pump shutoff. With reliability concerns during vehicle life, EWP is not envisioned for beyond 250,000 mile applications.
While laboratory and short-term testing can show data trends and correlations, long-term and field studies provide a much richer set of data points that cover different operational envelopes, dynamic loadings, failure modes, and repair intervals. Therefore, there has been an investment in long-term field testing not just to gather data but to build reliability models that include the fluid properties, the engine configuration, and the operational characteristics. Engine fuel and coolant systems contamination, pumps and seals blow-off testing, shaft, bearing, seal, impeller, and casing failure mode analysis are some of the activities done to build and validate the system model with manufacturers. There has also been collaboration with component manufacturers to increase critical component performance.
The test trucks involved in the performance recorded study the operating profile and inlet temperature. The comparison pump set was built with on-the-shelf components, but the pump would be customized to meet the test truck duty cycle. The long-term natural gas consumption would be recorded and used in conjunction with fuel costs and comparisons for annualized total operating cost. Trucks used in the study are typically affected by high failure rates of some pump components, in particular, the seals and bearings. But over the course of testing, other failure modes can also occur, such as broken impeller blades or cavitation on the pump casing. The travel routes are typically a combination of highway and on-road driving. Because the study was typically done on experimental trucks that were otherwise still monitored for emissions with high uncertainty, no attempt was made to relate emissions to fuel consumption. Regular laboratory tests on similar trucks, made by large manufacturers for internal studies, make this comparison more complicated.
A variety of vehicle systems and accessories currently use electric pumps to circulate coolant through their cooling systems and deliver liquids to their actuators. The principal applications are the engine water pump, turbocharger coolant pump, intercooler pump, engine oil cooler pump, refrigerant pump for heat pump applications, and fuel pump for powered two-wheelers. Electric pumps provide on-demand performance, freeing cooling system design engineers from constraints imposed by the mechanical pump drive when optimizing the performance of the engine, its auxiliary systems, and other vehicle components, thereby improving fuel economy and enhancing comfort and safety.
Weaknesses of the electric water pump include the potential difficulty of optimizing reliability, durability, and packaging in the vehicle. Internal combustion engine cooling systems require metered coolant flow when the engine is cold and reduced flow once the engine reaches operating temperature. The innovative electronic and mechanical controls used to separately address system demand at different operating conditions, and to monitor pump performance, are complicated and expensive. Such challenges have hindered the increase in electric water pump application rates that would be expected with the expansion of electric system architectures and their loads in vehicles utilizing internal combustion engines.
The growing challenges of pursuing ever stricter vehicle fuel economy regulations and improving driver experience and comfort, meanwhile, should motivate OEMs to focus on the on-demand benefits of such pumps in optimizing their vehicle platforms and the systems acting on their performance. In conclusion, while the number of applications powered by electric water pumps is presently limited, their advantages in on-demand capability should lead to growth in the variety and volume of their applications in the vehicles of the near future.
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