Abstract:
A system and method for maintaining a supply of compressed air on a locomotive. In one embodiment of the invention a compressed air system for a railroad locomotive comprises: a first air compressor; a second air compressor; a layover heater for maintaining the temperature of engine coolant; and a control system, wherein the first air compressor, the second air compressor, the layover heater, and the control package can be powered by at least one of the following power sources: an onboard electrical power source; or an offboard power source, wherein the layover heater can utilize heat generated by the first air compressor and the second air compressor to maintain the temperature of engine coolant, and wherein the control system operating the compressed air system utilizes a first logic when the power source is the onboard electrical power source and a second logic when the power source is the off board power source.

Description:
TECHNICAL FIELD 
       [0001]    The present invention is in the field of locomotive diesel engines and compressed air systems. More particularly, the present invention is in the technical field of air compressor systems for diesel locomotive engines utilizing multiple air compressors, control and power circuits, and a layover heating system. 
       BACKGROUND OF THE INVENTION 
       [0002]    Air compressor systems for internal combustion engines, such as those powering locomotives, are known in the art for the purpose of generating compressed air to be used in the braking and auxiliary systems of the locomotive. For example, a prior art air compressor system may include a multi-cylinder air compressor with a pair of low pressure cylinders and a high pressure cylinder mounted on and supported by a crankcase. Generally, the air compressor is powered by the locomotive engine and is unavailable for use while the locomotive is shut down. 
         [0003]    Layover heater systems for internal combustion engines are also known in the art. These layover heater systems generally maintain engine coolant above certain temperatures when ambient temperatures are not sufficient to maintain the engine coolant. Keeping the engine coolant above certain temperatures enables idling locomotives to be shut down and easily restarted, even after days sitting in freezing weather. Equipping a locomotive with a layover heater helps to prevent problems associated with engine idling including wasted fuel and oil, wet-stacking, emissions, noise and engine wear. 
         [0004]    The traditional air compressor systems of the prior art have a disadvantage because they can not be powered when the locomotive engine is shut down. This lack of a constant supply of air pressure can delay the locomotive&#39;s departure by prolonging the brake departure test protocol. Further, the heat generated by the air compressor is not utilized and is instead considered waste heat. 
         [0005]    The disclosed multiple air compressor system and method is directed to overcoming one or more of the disadvantages listed above. 
       SUMMARY OF THE INVENTION 
       [0006]    In one aspect, the present invention disclosed herein is directed to a compressed air system for a railroad locomotive comprising: a first air compressor; a second air compressor; a layover heater for maintaining the temperature of engine coolant; and a control system, wherein the first air compressor, the second air compressor, the layover heater, and the control package can be powered by at least one of the following power sources: an onboard electrical power source; or an offboard power source, wherein the layover heater can utilize heat generated by the first air compressor and the second air compressor to maintain the temperature of engine coolant, and wherein the control system operating the compressed air system utilizes a first logic when the power source is the onboard electrical power source and a second logic when the power source is the off board power source. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a diagram of a multiple air compressor system for a diesel locomotive engine according to one embodiment the present invention. 
           [0008]      FIG. 2A  is a flowchart of a method for operating an air compressor system on a diesel locomotive engine according to an embodiment of the present invention. 
           [0009]      FIG. 2B  is a flowchart of a method for operating an air compressor system on a diesel locomotive engine according to another embodiment of the present invention. 
           [0010]      FIG. 3  is a flowchart of a method for operating an air compressor system on a diesel locomotive engine according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    The present application is directed toward the technical field of compressor systems for diesel engines utilizing multiple air compressors, control and power circuits, and a layover heating system. 
         [0012]    Referring to  FIG. 1 , one embodiment of the present invention is depicted. Multiple compressor system  100  may include at least two air compressors  102 , a layover heater  106 , and a control system  104 . 
         [0013]    Each air compressor  102  may be a rotary screw type air compressor, or any other type of air compressor known in the art. Each air compressor  102  may be rated at 60-80% of the minimum industry specified capacity for generating compressed air for locomotive breaking and auxiliary systems. Unlike traditional locomotive air compressor arrangements, air compressors  102  may be powered by shore power in addition to the electrical current generated by the onboard locomotive systems. Shore power may include 440 volt alternating current supplied from the commercial power grid, or any other type of commercially available power. An appropriate power plug and cord may be plugged into the locomotive from ground level to provide the shore power when the internal combustion engine is shut down or not operating at full capacity. 
         [0014]    Layover heater  106  may include an electrical heating system for maintaining the temperature of the engine coolant system above a certain temperature in freezing weather. Unlike traditional locomotive layover heater systems, in one mode of operation, layover heater  106  may include an electric heating element powered by shore power in addition to the electrical current generated by the onboard locomotive systems. Shore power may include 440 volt alternating current supplied from the commercial power grid, or any other type of commercially available power. An appropriate power plug and cord may be plugged into the locomotive from ground level to provide the shore power when the internal combustion engine is shut down or not operating at full capacity. Alternatively, or in cooperation with the electric heating element, layover heater  106  may utilize the heat generated by the air compressors  102  to warm engine coolant  122 , minimizing the need to operate the layover heater  106 . 
         [0015]    The control system  104  may include a microprocessor  105 . Control system  104  may be operatively connected  110  to air compressors  102 . Control system  104  may communicate with air compressors  102  along operative connection  110 , and may also receive status signals from air compressors  102  along operative connection  110 . 
         [0016]    Additionally, control system  104  may be operatively connected  112  to a layover heater  106 . Control system  104  may communicate with layover heater  106  along operative connection  112 , and may also receive status signals from layover heater  106  along operative connection  112 . Via operative connections  110  and  112 , control system  104  may monitor data such as the demand for power by the air compressors  102  and layover heater  106 , prioritizing the need for both systems and allocating current flow to maintain the desired level of compressed air and desired coolant temperature. 
         [0017]    As used in  FIG. 1  and the following figures and descriptions, operative connection or operative communication includes any type of wired or wireless communication. In a preferred embodiment, operative connections  110 ,  112  may comprise a wired data connection. 
         [0018]    Multiple compressor system  100  may also include a heat exchanger  120  which may be a heat exchanger device of any type used in the art of heat transfer systems. As the engine coolant  122  flows through the heat exchanger  120  and the layover heater  106 , it may be heated by the waste heat from air compressors  102  carried via oil  124  and transmitted through heat exchanger  120  and/or heat from the layover heater  106 . As the engine coolant  122  accumulates more energy, it will return to a higher temperature. As the engine coolant  122  exits the heat exchange device, it may be directed back into the locomotive engine. 
         [0019]    Control system  104  will monitor the engine coolant  122  and attempt to maintain the engine coolant  122  within a predetermined temperature range. In one embodiment, the predetermined temperature range may be between 13° F. and 185° F. When only one air compressor  102  is energized and operating, the layover heater  106  may also be energized to provide heat to the engine coolant  122 . If system air pressure demand requires the operation of both air compressors  102 , the layover heater  106  will be deenergized as long as both air compressors  102  are energized. Additionally, in one embodiment, shore power will not be utilized unless the locomotive is shutdown and will automatically de-energize and sound an alarm should the engine start running while shore power is energized. 
         [0020]    The control system  104  will monitor the engine coolant  122  and activate an alarm should the heating operation be requested with insufficient engine coolant  122  available. In another embodiment, there will be a mode of operation to run only the layover heater and not either of the air compressors  102 . 
         [0021]    By maintaining the engine coolant  122  at or above a certain temperature, the present invention may enable a railroad locomotive to be maintained at fully prepared status for deployment with no local emissions from an internal diesel engine. Because commercial power may be generated more efficiently at large generating stations, emissions in the form of greenhouse gases and particulate matter may be reduced by the present invention. Further, the present invention may also eliminate or reduce the noise associated with engine idling to produce compressed air and avoid the freezing of engine water. Further, multiple air compressor system  100  offers the advantage of redundancy for locomotive reliability and additional capacity for peak short term demand for compressed air. 
         [0022]    The present invention provides the ability to apply compressed air to the cars of a train when the train is parked in a stationary position without idling the locomotive&#39;s internal combustion engine to generate electrical power or compressed air. Maintaining a reliable and constant supply of compressed air to the cars and systems of the attached train offers the advantage of a more expeditious brake departure test protocol prior to dispatching the train. 
         [0023]    Multiple compressor system  100  includes at least two unique modes of operation. The first mode of operation may correspond to when the locomotive engine is running. The second mode of operation may correspond to when the locomotive engine is shutdown and another source of power is used, such as shore power as described above. 
         [0024]    Referring now to  FIG. 2A , a flowchart of one embodiment of the present invention is depicted. When the diesel engine of the locomotive is running, as at  210 , the following logic would be used to govern the operation of the multiple air compressor system  100 . At  220 , based upon a time interval, one compressor would be favored for operation over the other. If air pressure remains above a predetermined amount at  230 , one air compressor will continue to be used to satisfy the air demand, if the system air pressure falls below the predetermined amount at  230 , the control system  104  will energize both air compressors  102  to satisfy the air demand, as at  240 . 
         [0025]    Once an air compressor  102  is energized, it will be run until the temperature of air compressors oil  124  is at a predetermined level. If the current locomotive air demand is satisfied, the air compressor  102  will be run unloaded until the oil  124  reaches the predetermined temperature. 
         [0026]    Once the locomotive air demand is satisfied, the energized air compressor(s)  102  will be unloaded for a predetermined time period. During this predetermined time period, air pressure throughout the system may be monitored by the control system  104  to determine if it is falling at a rate which would require an air compressor  102  to be reenergized within a determined interval of shutdown. If this condition is met, the energized air compressor(s)  102  will continue to operate in an unloaded state until the locomotive air demand necessitates further air pressure. For example, if the air pressure is falling at such a rate that an air compressor  102  will need to be energized within ten minutes of shutting down, the control system  104  will instead direct air compressor  102  to operate in an unloaded state rather than to shut down air compressor  102  only to reenergize it less than ten minutes later. 
         [0027]    Each air compressor  102  will be monitored by the control system  104 . If an air compressor  102  fails to energize, run, or operate in any manner, a fault signal will be returned to the control system  104  via operative connection  110  and the other air compressor  102  may be utilized to satisfy current demand. 
         [0028]    The air compressor&#39;s oil  124  shares a heat exchanger  120  with the locomotive&#39;s engine coolant  122 , thus providing cooling for the air compressor&#39;s oil  124  while providing heating for the engine coolant  122 . 
         [0029]    Referring now to  FIG. 2B , a flowchart of another embodiment of the present invention is depicted. At  250 , when the diesel engine of the locomotive is not running, a shore power connection may be made at  260 . Once the shore power is connected, the following logic may be used to govern the operation of the multiple air compressor system  100 . 
         [0030]    Initially, at  270 , one air compressor  102  will be energized and utilized to provide air pressure to the multiple air compressor system  100 . The energized air compressor  102  will be determined, for example, according to a time schedule, with one air compressor  102  alternatively being favored over another air compressor  102 , on a rotating basis, balancing their duty cycle. Only one air compressor  102  will be maintained in the “hot and ready” state. 
         [0031]    At  280 , as long as the air pressure is maintained above a predetermined amount, one air compressor  102  will be utilized, as shown at  270 . However, at  280 , when air pressure falls below this predetermined amount, both air compressors  102  will be energized to satisfy the air demand, at  290 . 
         [0032]    Referring now to  FIG. 3 , a flowchart of another aspect of the present invention is depicted. At  300 , when the diesel engine of the locomotive is not running, a shore power connection may be made at  310 . Once the shore power is connected, the following logic may be used to govern the operation of the multiple air compressor system  100 . 
         [0033]    Initially, at  320 , one air compressor  102  will be energized and utilized to provide air pressure to the multiple air compressor system  100 . The energized air compressor  102  will be determined, for example, according to a time schedule, with one air compressor  102  alternatively being favored over another air compressor  102 , on a rotating basis, balancing their duty cycle. Only one air compressor  102  will be maintained in the “hot and ready” state. 
         [0034]    At  330 , when air pressure falls below a predetermined amount, both air compressors  102  will be energized to satisfy the air demand, at  340 . But as long as the air pressure is maintained above a predetermined amount, the process proceeds to the next step at  350 . At  350 , as long as the engine coolant temperature remains above a predetermined temperature, one compressor  102  will continue to be energized and utilized to provide air pressure to the multiple air compressor system  100 . However, if at  350  the coolant temperature falls below the predetermined temperature, at  360  layover heater  106  may be energized as described above to provide heat to the engine coolant. The process may then begin again at  320 , with one compressor providing air pressure. 
         [0035]    Also, another embodiment (not pictured) of the present invention may include a mode of operation to run only the layover heater  106  and not either of the air compressors  102 . This mode may be preferred when the locomotive is scheduled to be shutdown and a constant air supply is not needed, but it is still desirable to maintain the engine coolant at a certain temperature. 
         [0036]    The embodiments described above are given as illustrative examples only. It will be readily appreciated by those skilled in the art that many deviations may be made from the specific embodiments disclosed in this specification without departing from the invention. Accordingly, the scope of the invention is to be determined by the claims below rather than being limited to the specifically described embodiments above.