Combined aftercooler system with shared fans

A cooling system including an intake air cooling subsystem and a liquid cooling subsystem for controlling intake air temperatures in a supercharged internal combustion diesel locomotive engine. The intake air cooling subsystem includes an air-to-water aftercooler and an air-to-air aftercooler having intake air sides connected to receive intake air flow in series between a supercharger and an engine. The liquid cooling subsystem includes at least one liquid cooling loop having a pump, a radiator and a water coolant side of the air-to-water aftercooler. At least one shared fan circulates air flow to the cooling air sides of the air-to-air aftercooler and the radiator. An optional air distribution control selectively directs circulated air flow between the air-to-air aftercooler, the radiator and other optional components of the cooling system.

TECHNICAL FIELD

This invention relates to diesel electric locomotives and, more particularly, to cooling systems for cooling engine coolant and intake air in supercharged diesel engines.

BACKGROUND OF THE INVENTION

Diesel locomotive engines may utilize one or more superchargers to increase engine power by compressing ambient air to reduce its volume and increase its density. As the intake air is compressed by the supercharger, the air is heated to high temperatures. In order to reduce the temperature of the intake air and increase its density, an aftercooler is positioned downstream from the supercharger.

Tier 2 emission guidelines promulgated by the Environmental Protection Agency (EPA) set forth stringent emission standards for diesel locomotive engines. A preferred method of complying with the Tier 2 emission guidelines is to reduce intake air temperatures and thereby reduce the formation of NOx and other emissions during combustion.

Conventional locomotive cooling systems commonly use air-to-water aftercoolers, which reduce intake air temperatures only to around 180° Fahrenheit. In order to further reduce intake air temperatures, additional fans and substantially larger heat exchangers (aftercoolers and radiators) could be utilized. However, due to cost and space limitations, on locomotives, additional fans and larger heat exchangers are undesirable.

Accordingly, smaller and more efficient cooling systems capable of reducing intake air temperatures to meet EPA emission control requirements are desired.

SUMMARY OF THE INVENTION

The present invention provides simplified efficient locomotive cooling systems for significantly reducing supercharged diesel engine intake air temperatures.

In an exemplary embodiment, an air-to-water aftercooler and an air-to-air aftercooler are connected to receive intake air in series between a supercharger and an engine air box or an air intake manifold.

The air-to-water aftercooler is normally cooled by liquid engine coolant passed through a radiator for cooling. At least one shared fan circulates air flow through the air-to-air aftercooler and the radiator to transfer heat from the liquid coolant within the radiator and the intake air within the air-to-air aftercooler to the surrounding atmosphere.

If desired, a dynamic brake grid may be positioned in parallel or in series with the radiator and the air-to-air aftercooler to receive air flow from the shared fan. An optional air distribution control may be used to selectively alter circulated air flow between the air-to-air aftercooler, the radiator and the dynamic brake grid.

As the air-to-water aftercooler receives pressurized high temperature intake air from the supercharger, heat is transferred from the intake air to the liquid coolant flowing through the air-to-water aftercooler. The liquid coolant is then cooled by the radiator, which transfers heat from the liquid coolant to the surrounding atmosphere.

The intake air cooled by the air-to-water aftercooler is then directed to the air-to-air aftercooler where heat from the intake air is transferred to air circulated through the air-to-air aftercooler by the shared fan. The intake air cooled by the air-to-air aftercooler is then directed to an air box or an intake manifold of the engine.

The temperature of the liquid coolant and the heat discharged to the air-to-air aftercooler may be controlled by the shared fan which directs air flow through the air-to-air aftercooler and the radiator. Preferably, the air-to-air aftercooler and the radiator are positioned in series so that air is directed from the shared fan through the air-to-air aftercooler and then through the radiator. Alternatively, the air-to-air aftercooler and the radiator may be arranged in parallel so that air flow directed from the shared fan is split between the air-to-air aftercooler and the radiator by an air distribution control.

These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following description, like numerals indicate like parts or features throughout the various figures of the drawings.

Referring first toFIG. 1of the drawings in detail, numeral10generally indicates an engine cooling system for a supercharged internal combustion diesel locomotive engine11. The engine11receives compressed intake air from a supercharger12through an intake air cooling subsystem14including intake air sides of an air-to-water aftercooler16and an air-to-air aftercooler18. The aftercoolers16,18are positioned with their intake air sides in series in the air stream from the supercharger12to the engine11.

The cooling system10also includes a liquid cooling subsystem22having first and second overlapping liquid cooling loops24,26. The first liquid cooling loop24includes a coolant pump28, the diesel engine11, the water sides of one or more water radiators30, a water (coolant) tank32and an optional oil cooler34. The second liquid cooling loop26includes the water side of the air-to-water aftercooler16as well as the coolant pump28, the radiator30, the water tank32, and the optional oil cooler34of the first cooling loop24. Thus, the engine11and the air-to-water aftercooler16are connected in parallel in the liquid cooling subsystem22.

Cooling system10further includes one or more shared fans38having an ambient air intake and parallel cooling air discharge connections to cooling air sides of the air-to-air aftercooler18and the radiators30.

In operation, the supercharger, driven mechanically and/or by engine exhaust gases, provides compressed intake air to the engine for burning in the cylinders, not shown. Compression of the air increases its temperature in excess of 300° F., which is subsequently reduced by passing through the aftercoolers16,18. Preferably, the air-to-water aftercooler reduces the temperature of the intake air to between 200° F. and 220° F. and the air-to-air aftercooler further reduces the temperature of the intake air to between 100° F. and 130° F. This increases the charge density before the intake air enters the engine cylinders. The reduced charge temperature significantly reduces the nitrogen oxides (NOx) and particulate emissions formed during combustion while at the same time improving engine efficiency and durability. To this end the cooling system10operates to provide the desired cooling of the intake air as well as to maintain necessary cooling of the cylinders and other components of the engine.

In the liquid cooling subsystem22, the water tank32provides storage for excess coolant and a pressure head on the inlet of the coolant pump28. The pump discharges coolant to both cooling loops24,26.

In the first loop24, coolant from the pump first passes through the engine11where excess heat is transferred to the coolant.

In the parallel second loop26, coolant passes through the water side of the air-to-water aftercooler16where excess heat from the intake air is transferred to the coolant. Thereafter, the loops24,26are joined so that the coolant passes through the radiators30where the coolant is cooled by cooling air flow. The coolant then flows through the oil cooler34, for cooling the engine oil, and returns to the pump inlet.

The shared fans38circulate ambient air in parallel through cooling air discharge connections to cooling air sides of the air-to-air aftercooler18and the radiators30to transfer excess heat from the intake air and the liquid coolant to the circulated air. Sharing the fans38reduces the amount of space required for the engine cooling system10and also reduce the manufacturing costs of the cooling system.

FIG. 2illustrates an alternative embodiment of cooling system40similar to system10. In this embodiment, the cooling air sides of the air-to-air aftercooler18and the radiator30are positioned to receive circulated air flow from the shared fans38in series. Preferably, the cooling air passes to the air-to-air aftercooler18first and to the radiator30second to provide the coolest air to the aftercooler and obtain the lowest possible intake air temperature.

In operation, cooling system40is similar to cooling system10in that system40maintains the operating temperature of the engine11and reduces the intake air temperatures to improve fuel economy and reduce NOx and particulate emissions. The shared fan38circulates air to the cooling air side of the air-to-air aftercooler18to draw heat from the intake air to the circulated air. The circulated air is then passed through the cooling air side of the radiator30to draw heat from the liquid coolant to the circulated air.

FIG. 3illustrates another alternative embodiment of cooling system50similar to system10. In this embodiment, the cooling air sides of the radiator30and air-to-air aftercooler18are positioned to receive circulated air flow in parallel. The shared fan38circulates air to an air distribution control52, which selectively controls the amount of circulated air flow through the cooling air sides of the air-to-air aftercooler18and the radiator30. Optional temperature sensors54may be used to detect the temperature of the intake air and the liquid coolant and relay the temperature information to the distribution control52.

In operation, cooling system50is similar to system10in that cooling system50maintains the operating temperature of the engine11and reduces intake air temperature. As the engine11operates, intake air and liquid coolant temperatures are monitored by the sensors54and the temperature information is relayed to the air distribution control52. The air distribution control52then selectively divides circulated air flow between the cooling air sides of the radiator30and the air-to-air aftercooler18to maintain desired intake air and the liquid coolant temperatures. Ambient conditions may also be considered by the air distribution control52, to determine optimal circulated air flow ratios between the cooling air sides of the air-to-air aftercooler18and the radiator to maintain optimal intake air and liquid coolant temperatures.

FIG. 4shows yet another alternative embodiment of cooling system60similar to the cooling system50ofFIG. 3. System60also includes a dynamic brake62operative to transform kinetic energy of the train into electric energy. The electric energy created during dynamic braking is fed into a dynamic brake grid64, which converts the electric energy into heat that is dissipated into surrounding air. The shared fan38circulates air flow to a distribution control52, which adjusts the air flow between the dynamic brake grid64and the cooling air sides of the air-to-air aftercooler18and the radiator30. The dynamic brake grid64and the cooling air sides of the air-to-air aftercooler18and the radiator30may be positioned to receive air flow from the distribution control52in parallel or in series.

In operation, during acceleration and powered train operation, the distribution control52directs a majority of the circulated air flow to the cooling air sides of the radiator30and the air-to-air aftercooler18to maintain optimal liquid coolant and engine intake air temperatures. During dynamic braking, heat is generated by the dynamic brake grid64, while engine power and boost are dramatically reduced. As a result, the cooling air sides of the air-to-air aftercooler and the radiator require less air flow to maintain optimal intake air and the liquid coolant temperatures. In order to increase the cooling capacity of the brake grid64, the distribution control52diverts a majority of the circulated air flow from the cooling air sides of the air-to-air aftercooler18and the radiator30to the to brake grid64, resulting in improved heat transfer from the brake grid to the circulated air. As needed, air may be redirected to the cooling sides of the radiator30and the air-to-air aftercooler18to maintain the desired liquid coolant and intake air temperatures during dynamic braking.

Another alternative embodiment of a cooling system70is illustrated inFIG. 5. Cooling system70includes an intake air cooling subsystem14and separate first and second cooling loops71,72connected by a linking valve74and the water tank82. The first cooling loop71includes a main pump76, the engine11, an optional temperature sensor84, an engine radiator78, an oil cooler80, and a water tank82. The second liquid cooling loop72includes an aftercooler pump86, an optional temperature sensor84, the water side of the air-to-water aftercooler16, an aftercooler radiator88, and the water tank82. Cooling air sides of an air-to-air aftercooler18, the engine radiator78and the aftercooler radiator88are positioned to receive air flow in series from shared fans38.

In operation, the pumps76,86circulate liquid coolant through the cooling loops71,72. As the liquid coolant circulates through the loops, the temperature sensors84monitor the temperature of the liquid coolant. Based upon the temperatures of the liquid coolant in each of the cooling loops71,72, the linking valve74diverts liquid coolant between the loops, as needed, to maintain optimal intake air and liquid coolant operating temperatures.

During engine operation in low ambient temperatures, a portion of the liquid coolant, heated by the engine, in the first liquid cooling loop71may be diverted into the second liquid cooling loop72to increase the temperature of the liquid coolant in the second liquid cooling loop and thereby prevent overcooling of the intake air.

During engine operation in high ambient temperatures, a portion of the liquid, heated by the air-to-water aftercooler16, in the second liquid cooling loop72may be diverted to the first liquid cooling loop71to reduce the temperature of the liquid coolant in the first liquid cooling loop and thereby reduce engine operating temperatures.

Heat is removed from the cooling system70by circulated air generated by the shared fans38. Preferably, the shared fans38circulate air through the cooling air side of the air-to-air aftercooler18first to provide maximum cooling to the intake air. The circulated air is then passed through the cooling air sides of the aftercooler radiator88in the second cooling loop and the engine radiator78in the first cooling loop71to provide preferred cooling to the aftercooler.

FIG. 6shows another embodiment of cooling system90, similar to the cooling system70ofFIG. 5. In system90, shared fans38circulate air flow to the cooling air sides of an air-to-air aftercooler18, an engine radiator78and an aftercooler radiator88. Preferably, the cooling air side of the air-to-air aftercooler18is positioned to receive circulated air flow in parallel with the cooling air sides of the aftercooler radiator88and the engine radiator78, which receive circulated air flow in series.

In operation, the cooling system90operates similarly to cooling system70ofFIG. 5, in that the cooling system90maintains liquid coolant temperatures within cooling loops71,72and maintains intake air temperatures to provide intake air the engine11at optimal temperatures.

In still another alternative embodiment, illustrated inFIG. 7, a cooling system100includes an intake air cooling subsystem14and first and second partially overlapping parallel cooling loops101,102. The first cooling loop101includes a pump103, an engine11, a main radiator104, an oil cooler105and a water tank106. The second cooling loop102includes the pump103and the main radiator104, together with a supplemental low temperature radiator107, and the water side of an air-to-water aftercooler16.

The cooling system100further includes shared fans38, which circulate air through the cooling air side of the air-to-air aftercooler, in parallel with the low temperature radiator107and the main radiator104in series.

The pump103discharges liquid coolant through both cooling loops101,102. The liquid coolant is initially circulated from the pump103through the water side of the engine11where excess heat from the engine is transferred to the liquid coolant. The liquid coolant, heated by the engine11, is then directed to the main radiator104for cooling. Liquid coolant passing through the first loop101from the main radiator104then enters the oil cooler105and finally returns to the pump103. Liquid coolant directed through the second loop102, from the main radiator104, is subcooled in the low temperature radiator107and then circulated through the water side of the air-to-water aftercooler16where excess heat in the intake air is transferred to the liquid coolant. The liquid coolant in the second loop102is returned to the pump103to be recirculated through the cooling system.

The shared fans38circulate air flow between the cooling air sides of the air-to-air aftercooler18, the low temperature radiator107, and the main radiator104to exchange heat from the intake air and the liquid coolant to the circulated air.

In yet another alternative embodiment, illustrated inFIG. 8, an intake air aftercooling system110includes an intake air cooling subsystem14and a liquid cooling subsystem111. The liquid cooling subsystem111includes a pump114, an optional oil cooler116, a thermostat118, a radiator120and the water side of an air-to-water aftercooler16. The thermostat connects with a radiator bypass122to control the coolant at a desired minimum operating temperature. Shared fans38circulate ambient air in parallel through the cooling air sides of the radiator120and an air-to-air aftercooler18to control the temperature of the liquid coolant and the intake air.

In the liquid cooling subsystem111, coolant is discharged from the pump114to the oil cooler where excess heat is transferred from engine oil to the liquid coolant. When the temperature of the liquid coolant is below an optimal temperature, the thermostat directs liquid coolant partially or fully from the oil cooler, through the bypass122to the air-to-water aftercooler where heat is transferred from the intake air to the liquid coolant. The liquid coolant is then finally returned to the pump to be recirculated. When the temperature of the liquid coolant reaches a desired minimum, the thermostat directs liquid coolant, to the radiator120which discharges heat in the liquid coolant to the circulated air provided by the shared fans38. The liquid coolant is then directed to the air-to-water aftercooler and finally back to the pump to be recirculated.

The shared fans38circulate air flow through the radiator120and the air-to-air aftercooler18to exchange heat from the intake air and the liquid coolant to the circulated air.