Patent Application
20140150738
The present disclosure relates generally to a cooling system and, more particularly, to a cooling system having a shock reducing valve.
Engines, including diesel engines, gasoline engines, and gaseous fuel-powered engines are used to generate mechanical, hydraulic, or electrical power. In order to accomplish this power generation, an engine typically combusts a fuel/air mixture. With the purpose of ensuring optimum combustion of the fuel/air mixture and protecting components of the engine from extreme temperatures, the temperature of the engine must be tightly controlled.
An internal combustion engine is generally fluidly connected to one or more heat exchangers to cool liquids circulated throughout the engine. These heat exchangers are often located close together, and/or close to the engine, to conserve space on the machine. An engine-driven fan may be disposed in front of the engine and heat exchanger to blow air across the heat exchanger and the engine. Alternatively, the engine-driven fan may be disposed between the engine and heat exchanger to draw air past the exchangers and blow air past the engine. The airflow removes heat from the heat exchangers and the engine.
In current engine cooling systems, a thermostat having a temperature-sensitive flow control element may be used to regulate the flow of coolant from the engine to the heat exchanger. For example, when the temperature of the engine exceeds a threshold of the thermostat, the flow control element expands to open a valve, thereby allowing communication between the engine and the heat exchanger. Since the hot coolant from the engine typically has a much higher temperature than the heat exchanger, the coolant suddenly entering the heat exchanger can cause a thermal shock that induces a strain on the heat exchanger. This strain can result in cracking of the heat exchanger, thereby shortening the lifespan of the heat exchanger and/or compromising the effectiveness of the heat exchanger.
An exemplary cooling system is described in U.S. Pat. No. 4,964,371 (the '371 patent) issued to Maeda et al. on Oct. 23, 1990. The '371 patent describes an engine cooling system comprising two temperature-regulated valves that selectively open or close a bypass passage based on coolant temperature. This mechanism allows coolant to either flow through a heat exchanger or to flow back to the engine without travelling to the heat exchanger. The opening and closing of one of the valves is additionally regulated by changes in air pressure, which vary based on changes in engine load conditions. This valve is controlled so that it closes at low engine loads regardless of temperature. In this manner, an amount of coolant passing through the heat exchanger can be varied based on engine loading.
Although the '371 patent discusses varying coolant flow dependent on changing engine load conditions, it may not adequately reduce thermal strain at all loading conditions. Specifically, the system taught in the '371 patent may still allow hot coolant returning from the engine to suddenly flow through the two valves to the heat exchanger at high engine load. Accordingly, shock loading can be experienced by the heat exchanger during operation of the engine.
The disclosed cooling system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.
In one aspect, the present disclosure is directed to a cooling system for an engine. The cooling system includes a pump driven by the engine and configured to circulate coolant through the engine. The cooling system also includes a heat exchanger configured to receive coolant from the engine and to reduce a temperature of the coolant. The cooling system further includes a theiniostat fluidly connected to the engine and the heat exchanger. The thermostat is configured to selectively direct coolant from the engine to the heat exchanger when a temperature of the coolant is greater than a temperature threshold of the thermostat. The thermostat is also configured to substantially block coolant from passing to the heat exchanger when the temperature of the coolant is less than or equal to the temperature threshold. The cooling system also includes a valve fluidly connected to the engine and the heat exchanger, and connected in parallel with the thermostat. The valve is configured to direct a portion of the coolant exiting the engine to the heat exchanger during a first operating condition. During the first operating condition, a pressure of the coolant exiting the engine is greater than a pressure threshold of the valve.
In another aspect, the present disclosure is directed to a cooling system for an engine. The cooling system includes a pump driven by the engine and configured to circulate coolant through the engine. The cooling system also includes a heat exchanger configured to receive coolant from the engine and to reduce a temperature of the coolant. The cooling system further includes a thermostat fluidly connected to the engine, the pump, and the heat exchanger. The thermostat is configured to simultaneously direct coolant from the engine to the heat exchanger, while substantially blocking passage of coolant from the engine to the pump when a temperature of the coolant is greater than a temperature threshold of the thermostat. The cooling system also includes a valve fluidly connected to the engine and the heat exchanger, and connected in parallel with the thermostat. The valve is configured to direct a portion of the coolant exiting the engine to the heat exchanger when a pressure of the coolant is greater than a pressure threshold of the valve. The valve is also configured to substantially block passage of coolant to the heat exchanger when the pressure of the coolant is less than or equal to the pressure threshold.
In yet another aspect, the present disclosure is directed to a method of cooling an engine. The method includes receiving heated coolant from the engine. The method also includes directing a portion of the coolant from the engine to a heat exchanger during a first operating condition, in response to a pressure of the coolant being greater than a threshold pressure. The method further includes directing a remainder of the coolant to a pump during the first operating condition, in response to a temperature of the coolant being less than or equal to a threshold temperature.
In the disclosed embodiment, machine 2 may include a frame 4 that supports an engine 10 and a cooling system 12 within an enclosure 6. Enclosure 6 may embody a removable cowling having one or more air inlets that allow air flow through at least a portion of enclosure 6 for cooling purposes.
Engine 10 may include multiple components that cooperate to produce a power output. In particular, the engine 10 may include an engine block that defines a plurality of cylinders, a piston slidably disposed within each cylinder, and a cylinder head associated with each cylinder (not shown). One skilled in the art will recognize that the engine 10 may be any type of internal combustion engine such as, for example, a two- or four-stroke diesel, gasoline, or gaseous fuel-powered engine. The combination of a cylinder, associated piston, and associated cylinder head may form a combustion chamber. In one embodiment, the engine 10 may include four combustion chambers. However, it is contemplated that the engine 10 may include any number of combustion chambers and that the combustion chambers may be disposed in an “in-line” configuration, a “V” configuration, or any other suitable configuration.
As shown in
Additionally, the cooling system 12 may include an inlet passage 33 fluidly connected with the engine 10, and configured to receive heated coolant from the engine 10. In exemplary embodiments, inlet passage 33 may comprise a fluid channel, manifold, and/or other like fluid handling component, and the thermostat 26 may be disposed within and/or otherwise fluidly connected to inlet passage 33. In exemplary embodiments, the fluid connection between inlet passage 33 and thermostat 26 may enable thermostat 26 to at least partially control fluid communication between engine 10 and other downstream components of cooling system 12. For example, as will be described in greater detail below, thermostat 26 may be configured to at least partially control fluid communication between engine 10, via inlet passage 33, and at least one of pump 18 and heat exchanger 22.
The cooling system 12 may further include a shock reducing valve 28 fluidly connected to inlet passage 33. As shown in
Thermostat 26 may be configured to direct a heated flow of coolant from the engine 10 to the heat exchanger 22. In exemplary embodiments, the thermostat 26 may be configured to selectively fluidly connect the engine 10 and the heat exchanger 22 based on a temperature of the coolant received from the engine 10. For example, as will be described in greater detail below, when a temperature of the coolant received from the engine 10 is less than or equal to a threshold temperature of the thermostat 26, such coolant may be prohibited from passing from inlet passage 33 into flow passage 32 by way of the thermostat 26. Such a configuration is shown in
As shown in
In exemplary embodiments, thermostat 26 may comprise a variable flow control valve and/or other like variable flow control device. In such embodiments, thermostat 26 may be configured to achieve and/or maintain any number of intermediate positions between the first and second flow-blocking positions described above. In such intermediate positions, flow element 46 may be disposed at any position along pin 56 to increase, decrease and/or otherwise variably control fluid communication between inlet passage 33, and passages 44, 32. It is understood that, in some configurations of thermostat 26, fluid communication between inlet passage 33, and passages 44, 32 may be simultaneously controlled by movement of flow element 46. In such embodiments, for example, an increase in flow from inlet passage 33 to flow passage 32 via thermostat 26 may result in a corresponding and simultaneous decrease in flow from inlet passage 33 to bypass passage 44 via thermostat 26. Alternatively, in further exemplary embodiments, thermostat 26 may comprise a non-variable, on/off-type flow control valve and/or other like flow control device. In such embodiments, thermostat 26 may be configured to transition between the first and second flow-blocking positions described above substantially instantaneously, without maintaining any of the intermediate positions described above. It is contemplated that the threshold temperature of the thermostat 26 may comprise a melting point of pellet 48, and may be any desired temperature commonly achieved by engine coolant. For example, such a threshold temperature may be between approximately 50 degrees Celsius and approximately 100 degrees Celsius. In still further embodiments, such a threshold temperature may be between approximately 80 degrees Celsius and approximately 90 degrees Celsius.
With continued reference to
Pump 18 may be an engine-driven centrifugal pump configured to pressurize coolant within the cooling system 12. For example, pump 18 may be configured to direct pressurized coolant into the engine 10 via a returning passage 16 fluidly connected to pump 18 and engine 10. In exemplary embodiments, pump 18 may include one or more impellers (not shown) disposed within a volute housing (not shown). Such impellers may be configured to selectively draw in coolant from the heat exchanger 22, via flow passage 14, and to pressurize the coolant received from the heat exchanger 22. The pump 18 may also be configured to receive additional coolant from the shunt line 42 and/or the bypass passage 44, and to pressurize such coolant. As coolant enters pump 18 via first inlet 15, second inlet 19, and/or third inlet 25, blades of the impeller may be rotated by operation of engine 10 to push against the coolant, thereby pressurizing the coolant. An input torque imparted by engine 10 to pump 18 may be related to a resulting pressure of the coolant, while a speed at which pump 18 is driven by engine 10 may be related to a resulting flow rate of the coolant. The speed at which pump 18 is driven may also be related to a resulting temperature of the coolant. For example, in one embodiment, pump speed may be directly proportional to the absolute temperature of the coolant exiting pump 18 and passing through returning passage 16. In such an embodiment, for example, a relatively high pump speed may limit the dwell time of coolant within heat exchanger 22, and thus, may limit the reduction in coolant temperature affected by heat exchanger 22. It is contemplated that pump 18 may alternatively embody a piston-type pump, if desired, and may have a variable or constant displacement.
With continued reference to
As shown in
Shunt valve 40 may comprise a check valve, a diaphragm valve, and/or any other like flow control device. In a first exemplary embodiment, shunt valve 40 may be biased, via a spring and/or other like resistance component, in a closed position. In such embodiments, shunt valve 40 may remain in the closed position until pressure within shunt tank exceeds a pressure threshold of shunt valve 40. Upon reaching such a pressure threshold, shunt valve 40 may transition to an open position and, for example, air collected and/or stored within shunt tank 38 may be released from shunt system 39 via shunt valve 40. In further exemplary embodiments, one or more additional vapor-liquid separators may be fluidly connected to shunt valve 40 and/or shunt tank 38 to assist in separating entrained air from the coolant stored therein. Such additional vapor-liquid separators may be configured to assist shunt valve 40 in releasing air collected and/or stored within shunt tank 38. In this manner, the shunt valve 40 may be configured to assist in regulating fluid pressure of the cooling system 12, and may be configured to prevent excessive pressures that would otherwise damage the heat exchanger 22 and/or other cooling system components. Additionally, by maintaining the coolant at an elevated pressure less than the pressure threshold of the shunt valve 40, the shunt valve 40 may assist in raising the boiling point of the coolant and may allow for more efficient operation of the engine 10. In exemplary embodiments, the pressure threshold of shunt valve 40 may be between approximately 10 psi and approximately 40 psi, and in further exemplary embodiments, such a threshold pressure may be between approximately 15 psi and approximately 20 psi.
Shunt line 42 may be a conduit similar to flow passage 14, bypass passage 44, returning passage 16, flow passage 32, and/or engine vent line 34 described above, and may be configured to transport deaerated coolant from shunt tank 38, at an elevated pressure, to the third inlet 25 of pump 18. The flow of coolant from shunt tank 38, through shunt line 42, into pump 18 may help to prevent pump cavitation by maintaining a positive pressure head of coolant at the pump 18. Cavitation of pump 18 may occur if, for example, a net inlet pressure in the pump 18 drops below a vapor pressure of the coolant. Providing a flow of pressurized coolant to pump 18 via shunt line 42 may increase the net inlet pressure of pump 18, and may thereby minimize such cavitation.
The shock-reducing valve 28 may be configured to minimize and/or substantially eliminate thermal shock caused by a sudden flow of relatively high temperature coolant from engine 10 to heat exchanger 22 via thermostat 26. As shown in
Shock-reducing valve 28 may include, among other things, a valve element 160, a seat 170, and a valve spring 166 configured to apply a biasing force to valve element 160. In exemplary embodiments, the biasing force applied by valve spring 166 may be sufficient to hold valve element 160 against seat 170, and to thereby substantially prohibit fluid from passing through an opening 161 in seat 170. For example, as shown in
Shock-reducing valve 28 may further include one or more passages 168 fluidly connected to opening 161 and to flow passage 31. As shown in
The flow of coolant directed to heat exchanger 22 by way of shock-reducing valve 28 may comprise a relatively small percentage of the total amount of coolant directed to inlet passage 33 from engine 10, and such a flow may be referred to herein as a “reduced” flow of coolant and/or a “portion” of the flow of coolant. In exemplary embodiments, the reduced flow of coolant may comprise between approximately 1 percent and approximately 20 percent of the total flow of coolant entering inlet passage 33 from engine 10. In further exemplary embodiments, the reduced flow of coolant may comprise between approximately 1 percent and approximately 5 percent of the total flow of coolant entering inlet passage 33 from engine 10. While thermostat 26 is in the first flow-blocking position, the reduced flow of coolant directed to heat exchanger 22 by shock-reducing valve 28 may be at an elevated temperature relative to coolant within the heat exchanger 22. Thus, the reduced flow of coolant directed by the shock-reducing valve 28 to the heat exchanger 22 may moderately increase the temperature of and/or otherwise condition the heat exchanger 22 before a remainder of the coolant exiting engine 10 via inlet passage 33 passes to the heat exchanger 22 via the thermostat 26 (in the second flow-blocking position). In exemplary embodiments, the shock-reducing valve 28 may be configured to facilitate a more gradual temperature increase of the heat exchanger 22 as compared to a relatively sudden temperature increase that may occur if coolant were only provided to the heat exchanger 22 via the thermostat 26 in the second flow-blocking position. In exemplary embodiments, the shock-reducing valve 28 may be may be connected in parallel with the thermostat 26, and as shown in
Shock-reducing valve 28 may also be configured to allow passage of air to shunt system 39 while obstructing the passage of coolant thereto. In such embodiments, shock-reducing valve 28 may include one or more air passages 162 fluidly connecting inlet passage 33 with flow passage 31 and/or engine vent line 34. Such air passages 162 may be configured to permit passage of air to shunt system 39 in relatively low-pressure and/or low coolant flow conditions, such as when the fluid pressure of coolant entering inlet passage 33 from engine 10 is less than or equal to the pressure threshold of shock-reducing valve 28. In exemplary embodiments, air passages 162 may include respective check valves (not shown) and/or other like flow control devices configured to permit flow in a first direction while prohibiting flow in a second direction opposite the first. For example, such check valves may permit the flow of air from inlet passage 33 to flow passage 31, but may prohibit the flow of liquid coolant from flow passage 31 to inlet passage 33. For example, in the flow-blocking position of shock-reducing valve 28 shown in
As shown in
The disclosed cooling system 12 may be used in any machine or power system application in which it is beneficial to tightly control engine temperatures. The disclosed cooling system 12 may be used for land-based applications such as construction, farming, mining, drilling, and/or general transportation and marine applications, in which water from the marine environment may used for cooling purposes. The disclosed cooling system 12 may provide cooling of both air and coolant that enters or bypasses the engine 10. The disclosed cooling system 12 may provide an effective solution to engine cooling while minimizing thermal strain on the heat exchanger 22. Such a reduction in thermal strain may extend the useful life of the heat exchanger 22 and the various components of the cooling system 12 fluidly connected thereto. The operation of cooling system 12 will now be described with respect to
During and/or shortly after startup of engine 10, the temperature of coolant disposed in heat exchanger 22 and/or exiting the engine 10 may be approximately equal to ambient temperature. Additionally during and/or shortly after startup, the fluid pressure of coolant exiting engine 10 may be relatively low. For example, in such conditions, the temperature of the coolant entering inlet passage 33 from the engine 10 may be less than or equal to the threshold temperature of thermostat 26, and the fluid pressure of such coolant may be less than or equal to the threshold pressure of shock-reducing valve 28. Such an operating condition of the cooling system 12 is illustrated in
In such a low pressure, low temperature operating condition, substantially all of the coolant exiting engine 10 may be directed to the bypass line 44, and such coolant may pass to pump 18 via the second inlet 19. Such coolant may be pressurized by the pump 18, and may be returned to the engine 10 via the returning passage 16. As the coolant cycles through the engine 10, the coolant may assist in reducing the temperature of relatively high-temperature components of the engine 10 by absorbing heat therefrom. For example, coolant cycled through the engine 10 may assist in absorbing heat from and/or otherwise cooling the engine block, the external walls of the cylinders, the cylinder heads of engine 10, and/or other such components, through known convective heat transfer processes.
Due to, among other things, operation of the pump 18, the fluid pressure of the coolant cycling through engine 10 may increase over time. Additionally, as heat is transferred to such coolant, the temperature of the coolant may increase. In an exemplary embodiment, the fluid pressure of the coolant may exceed the pressure threshold of the shock-reducing valve 28 before the temperature of the coolant exceeds the temperature threshold of thermostat 26. For example, the pressure threshold of the shock-reducing valve 28 may be exceeded at elevated engine speeds. Such engine speeds may be between, for example, approximately 1500 rpm and approximately 8000 rpm, and such speeds may depend upon, among other things, the size, type, and/or configuration of the engine 10. Such an operating condition of the cooling system 12 is illustrated in
As coolant continues to circulate through the engine 10 and absorb heat, the coolant may eventually exceed the threshold temperature of the thermostat 26. Such an elevation in temperature may cause expansion of the pellet 48 of the thermostat 26, and such expansion may result in the thermostat 26 transitioning from the first flow-blocking position to the second flow-blocking position. In particular, expansion of the pellet 48 may cause flow element 46 to move away from top 58, and in a direction toward the inlet 35 of the bypass passage 44. As described above, in the second flow-blocking position, the flow element 46 may substantially block fluid communication between the bypass passage 44 and the inlet passage 33. At the same time, the flow element 46 may permit fluid communication between the flow passage 32 and the inlet passage 33 via, for example, the one or more openings 54 of the thermostat 26. Such an operating condition of the cooling system 12 is illustrated in
In the event that the fluid pressure of the coolant entering inlet passage 33 from the engine 10 falls below the pressure threshold of shock-reducing valve 28 and the coolant temperature remains above the temperature threshold of thermostat 26, the shock-reducing valve 28 may transition to the flow-blocking position while the thermostat 26 may remain in the second flow-blocking position. During such a “low pressure, high temperature” operating condition, substantially all of the coolant entering inlet passage 33 from the engine 10 may be directed to the flow passage 32 via the thermostat 26. In such an operating condition of the cooling system 12, the thermostat 26 may substantially prohibit the flow of coolant from entering the bypass passage 44, and the shock-reducing valve 28 may substantially prohibit the flow of coolant from entering the flow passage 31.
Additionally, in operating conditions in which the ambient temperature is relatively high, it is contemplated that the temperature of the coolant entering the inlet passage 33 may exceed the temperature threshold of the thermostat 26 before the fluid pressure of the coolant entering the inlet passage 33 exceeds the pressure threshold of the shock-reducing valve 28. Such operating conditions may exist, for example, at relatively low engine speeds, and during such operating conditions, prewarming of the heat exchanger 22 by way of the reduced flow may not occur. In such operating conditions, the thermal strain on the heat exchanger 22, and thus the need for prewarming, may be minimized because the difference between the ambient temperature and the temperature of the coolant and/or the heat exchanger 22 may be relatively small.
As a result of thermal expansion of the coolant, some of the coolant in the heat exchanger 22 and/or other components of the cooling system 12 may be diverted from the flow passage 32 into the shunt tank 38 via the shunt inlet 36. For example, if the capacity of the heat exchanger 22 is exceeded due to thermal expansion of the coolant, such excess coolant may be directed to the shunt tank 38 for storage. Additionally, during any of the operating conditions described herein, air that may have accumulated in the coolant due to turbulent flow may be stored and/or separated in the shunt tank 38. When the coolant pressure in the shunt tank 38 reaches the shunt tank threshold, the air may be vented out of cooling system 12 via shunt valve 40. As a result, deaerated coolant in the shunt tank 38 may circulate to the third pump inlet 25 of pump 18 via shunt line 42.
The cooling system 12 disclosed herein provides prewarming to the heat exchanger 22 to minimize or prevent thermal strain on the heat exchanger 22. This may be accomplished by directing the reduced flow of coolant to the heat exchanger 22 to condition the heat exchanger 22 before directing a full flow of hot coolant to the heat exchanger 22. In this manner, heat provided by the reduced flow of coolant may result in a more gradual temperature change at the heat exchanger 22 compared to the sudden temperature change that may occur in the absence of prewarming in prior art systems. As described above, this gradual temperature change may extend the useful life of the heat exchanger 22 and/or other components of the cooling system 12.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed cooling system without departing from the scope of the disclosure. Other embodiments of the cooling system will be apparent to those skilled in the art from consideration of the specification and practice of the cooling system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.
