Patent Publication Number: US-8522691-B1

Title: Apparatus and method for supplemental cooling

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a cooling system, and more particularly, to a supplemental cooling system for use in connection with a combustion engine fueled by a liquefied fuel gas, such as liquefied natural gas (LNG), for use in abnormal operating conditions. 
     BACKGROUND 
     In response to the diminishing availability of petroleum based liquid fuels, such as gasoline, diesel fuel, jet fuel, etc., as well as for other reasons, liquefied fuel gasses, such as LNG, have seen increased use as alternative fuels for combustion engines. Simultaneously, combustion engines have been developed, and are currently being developed, which can efficiently utilize these alternative fuels. As such, the manufacturers and users of locomotives, over-the-road trucks, off-the-road trucks, boats, etc., as well as others, are continuously investigating combustion engines that efficiently utilize liquefied fuel gas as a combustion fuel. 
     These types of liquefied fuel gas combustion engines often operate in environments that can change dramatically within a relatively short period of time, particularly if such engines are used in mobile applications. For example, during a single trip between destinations, a locomotive can operate in an open environment and, at select times during the trip, in a closed environment (such as in a tunnel). When the locomotive operates in an open environment, it is generally provided with an adequate amount of relatively cool ambient air that may be used for both combustion and for cooling the combustion engine, as well as other heat-sensitive components, such as electronics, of the locomotive. However, when the locomotive operates in a more closed environment, such as a tunnel, the amount of available air useful for cooling purposes may be considerably reduced. Further, since the temperature of that air can be considerably higher than standard ambient air, the thermal capacity of that air for cooling purposes can be decreased significantly over “standard” ambient air. For this reason, in such closed environments, performance of a mobile machine, such as a locomotive, can be severely affected. Examples of issues that can arise include overheating of the engine and/or related electronics and/or other heat-sensitive equipment. Alternatively, a mobile machine may have to be de-rated from its actual “standard” operating capabilities in order to account for the diminished capabilities of that machine in the closed environments that may only account for a very small amount of actual operating time of that locomotive. 
     One attempt to improve cooling of a mobile machine having a combustion engine utilizing a liquefied fuel gas is described in U.S. Pat. No. 5,375,580 (“the &#39;580 patent”) of Stolz et al. that issued on Dec. 27, 1994. The &#39;580 patent describes a combustion engine that is either supercharged or turbocharged, potentially in stages. Specifically, the &#39;580 patent discusses the use of a liquefied fuel gas in an internal combustion engine to which compressed intake combustion air is supplied using, for example, a supercharger or turbocharger, and which is fueled with a liquefied fuel gas, such as, for example, liquefied natural gas (LNG), wherein the cold revaporized fuel gas is heat exchanged with the compressed intake combustion air to cool the compressed intake combustion air to improve efficiency and performance of the engine. This heat interchange between the heated intake air and the cold liquefied fuel gas warms the liquefied fuel gas from its cold state to a temperature that permits operation of the internal combustion engine and, simultaneously, cools the compressed intake air to a temperature that improves engine efficiency. However, the cooling system disclosed in the &#39;580 patent is not necessarily useful in all situations, and particularly, situations such as those described herein wherein additional supplemental cooling is necessary due to the combustion engine utilizing a liquefied fuel gas being subject to temporary abnormal operating conditions. 
     Specifically, the cooling system described in the &#39;580 patent is related to a cooling system for a combustion air charging system or after cooler for a turbocharger or supercharger. It does not deal with direct engine cooling, supplemental cooling, or cooling of heat-sensitive components such as electronics. Furthermore, the cooling system described in the &#39;580 patent does not deal with specific instances of operation of the combustion engine wherein the standard operating conditions for the combustion engine, that the engine is generally rated for, change, due to, for example, the combustion engine travelling through a tunnel. As such, the cooling system described in the &#39;580 patent may not be used to provide supplemental, although needed, cooling to cool the engine of a combustion engine when it encounters unusual ambient air conditions, such as when the combustion engine is being utilized in a locomotive travelling through a tunnel Finally, since the cooling system described in the &#39;580 patent describes a system for cooling the air either entering a supercharger or turbocharger, between stages thereof, or as an aftercooler prior to the air entering the combustion chamber of the internal combustion engine, it does not disclose a method or an apparatus for use of the cooling capacity of a liquefied fuel gas to the components of the engine itself, or of other heat-sensitive components, much less to provide supplemental cooling when the combustion engine is being subjected to unusual or temporary ambient operating conditions. 
     SUMMARY 
     In one aspect, the disclosure is directed to a cooling system for a combustion engine utilizing a liquefied fuel gas, such as, for example, liquefied natural gas (LNG), liquefied petroleum gas (LPG), liquefied propane (LP), refrigerated liquid methane (RLM), etc. that may be subject to unusual and/or temporary ambient operating conditions. In such an aspect, the cooling system may include a heat exchanger in the combustion engine, a radiator configured to receive coolant from the combustion engine heat exchanger and transfer heat to ambient air passing through and/or over the radiator, a supplemental heat exchanger configured to receive coolant from the radiator and transfer heat to the liquefied fuel gas prior to the liquefied fuel gas entering an accumulator and/or the combustion engine for combustion, and a bypass loop. The cooling system may further include a first temperature sensor configured to generate a first signal indicative of a temperature of ambient air, and a controller in communication with a balance valve between the radiator and the supplemental heat exchanger and connected to the bypass loop to control the amount of coolant that is diverted through the supplemental heat exchanger versus being bypassed directly back to the combustion engine heat exchanger in order to achieve a desired coolant temperature prior to the coolant being recirculated back through the cooling system. 
     In another aspect, the disclosure is directed to a method of cooling a heat-sensitive component on a mobile machine having a combustion engine fueled by a liquefied fuel gas. The method may include circulating coolant from the main coolant loop through a heat-sensitive component of the mobile machine, and directing coolant from the heat-sensitive component through a radiator and a supplemental heat exchanger. The method may also include activating a balance valve between the supplemental heat exchanger and the radiator in order to regulate the temperature of the coolant as it flows through the coolant loop including the heat-sensitive component, the radiator, the bypass loop, and the supplemental heat exchanger. 
     In another aspect, the disclosure is directed to a method of cooling a heat-sensitive component on a mobile machine having a combustion engine fueled by a liquefied fuel gas. The method may include circulating coolant through a main coolant loop through a heat-sensitive component of the mobile machine, and directing coolant from the heat-sensitive component through a radiator and a supplemental heat exchanger. The method may also include directing a controller to empty a gas accumulator for storing a liquefied fuel gas in gaseous form after it has passed through a supplemental heat exchanger and directing a controller on a pump for pumping liquefied fuel gas in liquid form from a storage tank through the supplemental heat exchanger and to the accumulator at an increased rate. 
     In another aspect, the disclosure is directed to providing supplemental cooling to a heat-sensitive component and/or a combustion engine on a locomotive fueled by a liquefied fuel gas in anticipation of the locomotive passing through a tunnel. In accordance with such an aspect, the locomotive may include a tunnel indicator that initiates a tunnel operation, whereby a controller may direct a pump and/or valve operably connected to a supplemental heat exchanger for the combustion engine and/or heat-sensitive component cooling system to provide higher than normal cooling fluid flow to the supplemental heat exchanger, and thus, higher than normal cooling of the combustion engine and/or heat-sensitive component prior to the locomotive entering the tunnel. Specifically, in such an aspect, the controller may activate a balance valve for a bypass loop between a radiator and a supplemental heat exchanger to achieve a desired coolant temperature generally lower than “standard” operating temperature and, or in connection therewith, the controller (or another controller) may direct the emptying of a gas accumulator for storing a liquefied fuel gas in gaseous form after it has passed through the supplemental heat exchanger while simultaneously directing a pump for pumping liquefied fuel gas in liquid form from a storage tank through the supplemental heat exchanger to the accumulator at a higher than “standard” rate. Regardless, in such an aspect, the pre-cooling of the combustion engine and/or heat-sensitive component serves to effectively increase the tolerance of the combustion engine and/or heat-sensitive component to thermal overload prior to actual temperature increase created by the tunnel thus preventing potential adverse consequences created thereby. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a pictorial illustration of an exemplary embodiment of a cooling system in accordance with an aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an exemplary embodiment of a cooling system  6  in accordance with an aspect of the present disclosure as utilized in a mobile machine  10 , such as a locomotive, that includes a car body  12  supported at opposing ends by a plurality of trucks  14 . Each truck  14  may be configured to engage a track  16  via a plurality of wheels  17 . In the exemplary embodiment shown in  FIG. 1 , mobile machine  10  includes at least a first internal combustion engine  20  configured to combust a liquefied fuel gas having a heat exchanger  21  therein. Mobile machine  10  may also include power electronics  28  operatively supported by and included in the mobile machine  10 . 
     As shown in  FIG. 1 , the cooling system  6  may generally include a radiator  30  located in and/or on the car body  12  so that it is in thermal contact with the ambient air, a supplemental heat exchanger  32 , a bypass loop  34  and a balance valve  36 , all of which are in coolant fluid communication with the heat exchanger  21  for the combustion engine  20 . Additionally, in an aspect in accordance with the disclosure, the car body  12  may include a gas accumulator  40  for supplying gas fuel to the combustion engine  20  controlled by control valve  41  having controller  43 . In such an aspect of the disclosure, cooling system  6  may utilize coolant such as water, glycol, a water/glycol mixture, a blended air mixture, or any other heat transferring fluid as known to those of ordinary skill in the art which may be pumped through the cooling system  6  by coolant pump  7  having controller  8 . As will be apparent to a person of ordinary skill in the art, coolant pump  7  may be located practically anywhere in cooling system  6 . In at least one aspect of the present disclosure, liquefied fuel gas  42 , such as liquefied natural gas (LNG), may be stored in a storage tank  44  located on a tender car  46 . The LNG may, in such an aspect, be stored cryogenically in the storage tank  44  and may be pumped to the supplemental heat exchanger  32  by a liquefied fuel gas pump  48  powered by a motor  50  having a controller  52 . 
     In one aspect of the disclosure, balance valve  36  may be a proportional type valve having a valve element movable to regulate a flow of coolant and may be controlled by a controller  37 . The valve element of balance valve  36  may be solenoid-operable to move between maximum cooling and bypass positions, as well as any number of positions in-between. In a maximum cooling position, balance valve  36  may permit substantially all of the coolant to flow through supplemental heat exchanger  32  prior to being diverted to the combustion engine  20  heat exchanger  21 . In the bypass position, balance valve  36  may divert substantially all of the coolant flow away from the supplemental heat exchanger  32  directly to the combustion engine  20  heat exchanger  21  via bypass loop  34 . Balance valve  36  may also include any number of non-discriminate intermediate positions between the maximum cooling position and the bypass condition. While balance valve  36  is described as being a proportional-type valve, a plurality of throttle-type valves (not shown) may alternatively be utilized as would be apparent to a person of ordinary skill in the art. 
     In use, in an aspect of the disclosure, an LNG fueled mobile machine  10  is normally cooled by radiator  30  by rejecting about 2400 KW of heat to the ambient air. When the mobile machine  10  encounters an abnormal, temporary increase in ambient air temperature, such as a tunnel, the radiator  30  is no longer able to reject heat to the atmosphere at that rate. Accordingly, a combustion engine  20  that might be rated at a certain level for normal operation must be de-rated to a level consistent with operation that would allow safe operation in abnormal, temporary conditions, such as tunnel operation. Thus, when a mobile machine  10 , such as a locomotive, approaches an abnormal ambient air condition, the controller  52  controlling the motor  50  driving the liquefied fuel gas pump  48  (in liquid form) may slow the rate of pumping of liquefied fuel gas based upon the amount of fuel gas (in gaseous form) currently being stored in accumulator  40 . Specifically, if the accumulator  40  is full (or more than half full) as the locomotive approaches the tunnel, the controller  52  will direct the motor  50  to slow or stop pump  48  so that the accumulator  40  will be evacuated by valve  41  prior to the locomotive entering the tunnel. Then, upon entering the tunnel, the controller  52  can direct motor  50  to a higher speed or “overload” rating, thereby providing the desired additional cooling through supplemental heat exchanger  32  increasing the cooling rate (e.g. 10× for 100% jacket water cooling) through the evaporation of the liquefied natural gas (in liquid form) in the supplemental heat exchanger  32 . 
     Conversely, if upon approaching the tunnel, accumulator  40  is empty (or less than half full), then it may not be necessary to empty accumulator  40  prior to the locomotive entering the tunnel. In such a situation, as with above, the controller  52  controlling the motor  50  driving the liquefied fuel gas pump  48  (in liquid form) may go to a higher rating whenever the additional cooling from the supplemental heat exchanger  32  is needed. In either instance, in accordance therewith, balance valve  36  may be employed to balance the flow of coolant between the radiator  30  and combustion engine  20  heat exchanger  21  (through the bypass loop  34 ) and the supplemental heat exchanger  32 . After cooling the coolant, the excess LNG fuel  42 , now in gaseous form, may be stored in accumulator  40  for use in normal operation of mobile machine  10  combustion engine  20 . 
     In another aspect of the disclosure, mobile machine  10  may be equipped with a cooling system  6  that is configured to cool another heat sensitive device, such as power electronics  28  of mobile machine  10 . In additional aspects of the disclosure, controllers  8 ,  37 ,  43 , and  52  may be single microprocessors or multiple microprocessors that include mechanisms for controlling an operation of cooling system  6 , an in particular, operations of the coolant pump  7 , valve  36 , valve  41 , and/or liquefied fuel gas pump  48 . Numerous commercially available microprocessors can be configured to perform the functions of controllers  8 ,  37 ,  43 , and  52 . It should be appreciated that controllers  8 ,  37 ,  43 , and  52  could readily be embodied in a general engine or machine microprocessor capable of controlling numerous engine and/or machine functions. Controllers  8 ,  37 ,  43 , and  52  may include memories, secondary storage devices, processors, and any other components necessary for running an application as is known by those of ordinary skill in the art. Various other circuits may be associated with controllers  8 ,  37 ,  43 , and  52  such as power supply circuitry, sensor circuitry, signal conditioning circuitry, solenoid driver circuitry, and other types of circuitry. 
     Controllers  8 ,  37 ,  43 , and  52  may rely on input from one or more sensors during regulation of cooling system  6 . In at least one aspect of the disclosure herein, controllers  8 ,  37 ,  43 , and  52  may rely on at least one sensor  54  configured to measure an ambient air temperature outside of mobile machine  10 , at least one sensor  56  configured to measure a temperature of coolant flowing from the combustion engine  20  heat exchanger  21 , at least one sensor  58  configured to measure the temperature of coolant fluid flowing from radiator  30  to bypass loop  34  and/or supplemental heat exchanger  32 , and at least one sensor  60  configured to measure the temperature of the liquefied fuel gas  42  after it has left supplemental heat exchanger  32 , although any number and types of sensors may be utilized. Sensors  54 ,  56 ,  58 , and  60  may embody, for example, temperature sensors configured to generate signals indicative of temperature and may direct corresponding signals to controllers  8 ,  37 ,  43 , and  52  as is known to those of ordinary skill in the art. 
     In another aspect of the disclosure, the mobile machine  10  may be equipped with a tunnel indicator  62  that initiates a tunnel operation, for example one or two miles prior to the locomotive entering the tunnel. Consistent with that aspect of the disclosure, upon receiving indication of an upcoming tunnel, controller  43  may direct valve  41  to empty accumulator  40 . In accordance therewith, controller  52  may direct motor  50  operably connected to liquefied fuel gas pump  48  to increase the flow of liquefied fuel gas  42  through supplemental heat exchanger  32  to accumulator  40 . Also in accordance therewith, controller  37  may direct balance valve  36  to direct additional coolant flow through supplemental heat exchanger  32  thereby providing additional cooling to combustion engine  20  through heat exchanger  21  and/or power electronics  28  prior to the tunnel being reached. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure relates to an internal combustion engine  20  which is fueled with a liquefied fuel gas (LFG)  42 , such as, for example, liquefied petroleum gas (LPG), liquefied propane (LP), refrigerated liquid methane (RLM), or liquefied natural gas (LNG). The present disclosure is generally applicable to combustion engines utilizing any gaseous fuel that can be stored as a liquid at pressures at or below about 200 psig (14 bar-g) and which can achieve adiabatic expansion temperatures of below about 50.degree. F. (10.degree. C.) from such storage pressures. Such internal combustion engines may be used in powering many devices, either stationary or moving. Commonly, such internal combustion engines are used also for locomotive power for transport vehicles such as cars, trucks, buses, railroad locomotives, and ship propulsion. Such internal combustion engines may also be used with stationary power plants, such as emergency power generators. 
     Specifically, this disclosure relates to a method and apparatus for providing supplemental cooling to an internal combustion engine  20  through heat exchanger  21  and/or other heat-sensitive equipment, such as power electronics  28 , wherein the internal combustion engine  20  is fueled with a liquefied fuel gas  42  as discussed above. Specifically, the present disclosure is particularly useful in supplying such supplemental cooling wherein the internal combustion engine  20  occasionally encounters unusual and/or temporary conditions where the ambient air temperature and/or intake air temperature is higher than the ambient air temperature the combustion engine generally experiences and/or is rated for. Specifically, the disclosed cooling system  6  may use supplemental cooling capabilities provided by cryogenically stored liquefied fuel gas  42  through the use of a supplemental heat exchanger  32  wherein the cooling system  6  is activated in response to an abnormal ambient air condition, such as is caused by a locomotive entering a tunnel. In another aspect, the disclosure is directed to providing supplemental cooling to a heat-sensitive component and/or a combustion engine  20  on a locomotive fueled by a liquefied fuel gas  42  in anticipation of the combustion engine  20  and/or heat-sensitive component encountering an abnormal, temporary, higher-than-normal, ambient air condition, such as a locomotive passing through a tunnel. 
     In accordance with an aspect of the disclosure, the supplemental cooling provided by the disclosed supplemental cooling system and method may be 160 KW or more. As will be apparent to those of ordinary skill in the art, the amount of supplemental cooling achievable consistent with an aspect of the disclosure is determined by size of the motor  50  and liquefied fuel gas pump  48  combination, as well as the size of the accumulator  40 . More specifically, it is within the scope of the disclosure that two pumps  48  and motors  50  be utilized, for redundancy purposes, and, if both were run in tandem, that supplemental cooling could be doubled to 320 KW or more. Of course, depending on the fuel needs of the internal combustion engine  20 , the size of the accumulator  40  may become the limiting parameter for additional supplemental cooling. In such an architecture, and presuming the LFG  42  is stored at approximately 500 bar, every minute of supplemental cooling in accordance with the disclosure should require approximately 8.5 gallons of accumulator  40  space. Accordingly, in order to provide supplemental cooling at a rate of approximately 160 KW for 10 minutes of combustion engine  20  running time, an approximately 85 gallon accumulator  40  would be needed. Similarly, to provide cooling for 20 minutes at approximately the same rate, an approximately 170 gallon accumulator  40  would be needed. As such, as should be apparent to a person of ordinary skill in the art, accumulator  40  size may be manipulated (as well as liquefied fuel gas pump  48  and motor  50  size) in order to achieve the desired amount of available supplemental cooling (subject to the fueling needs of the internal combustion engine  20 ). 
     The disclosed cooling system  6  may provide an efficient mechanism for providing supplemental cooling of a mobile machine  10  during temporary environmental extremes. For example, the disclosed cooling system  6  may provide more effective cooling during tunnel conditions by reducing heat increases and thus allowing lower-rated locomotives to be generally used thereby resulting in cost savings. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed cooling system  6  without departing from the scope of the disclosure. Other embodiments of the cooling system  6  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