Abstract:
Automatic control of the temperature of the inlet air being supplied to the engine ( 12 ) of a locomotive ( 10 ) in order to optimize the performance of the engine ( 12 ) under a variety of ambient air temperatures and pressures. One or more valves ( 38 ) is utilized to control the flow of warm air from the engine compartment ( 14 ) into the air inlet path ( 20 ). The position of valve ( 38 ) is controlled by controller ( 42 ) in response to at least one of an ambient air temperature signal T A , an ambient atmospheric pressure signal P A , and an inlet air temperature signal T I . The temperature of the air flowing through the warm air flow path  28  may be controlled by selecting from among a plurality of possible inlets ( 30, 32, 50 ). By varying the volume and temperature of the air flowing through the warm air flow path ( 28 ), the temperature and density of the air supplied at the engine inlet ( 18 ) may be moderated across a broad range of ambient air temperatures and pressures.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of internal combustion engines and, more particularly, to the control of an internal combustion engine of a locomotive to reduce the adverse effects of ambient air temperature changes on the performance of the engine. 
     Locomotives operated in the far north and south regions of the globe are subject to severe winter weather conditions, including cold temperatures, and blowing and drifting snow. It is known that snow may be drawn into the air inlet ducts of a locomotive and may accumulate in sufficient quantities to obstruct the passage of air through the ducts. It is not uncommon for snow to accumulate on air filters disposed in the air inlet pathway of a locomotive. Such accumulations of snow may reduce the power output of the engine or cause it to cease from operating completely. 
     It is known to provide summer/winter doors in a locomotive which function to connect the air inlet duct with a source of warm air so that the cold ambient air is mixed with relatively warmer air prior to passing through the final air filters. If the temperature of the inlet air mixture can be maintained above the freezing point, any snow that may be deposited on the filters or ductwork will melt rather than accumulating to the point of restricting intake air. The name “summer/winter” has been applied to these doors because in the prior art they were manually operated using a simple rule of thumb, such as open in the winter and close in the summer. Warm air is available in the engine compartment of a locomotive because radiant and convected heat from the engine tends to raise the air temperature around the engine. Because of the need to protect components such as wires, hoses and fuel lines from high temperatures, locomotive engine compartments are normally ventilated. It is known to pass the exhaust air from an equipment cabinet of the locomotive into the engine compartment to provide such ventilation. The exhaust from an equipment cabinet contains filtered and slightly pressurized air from an equipment blower, and it passes out of the equipment cabinet at a relatively low temperature. This air is exhausted through the engine compartment and into the combustion air intake ductwork through the summer/winter doors. 
     It is known to increase the flow of warm air from the engine compartment to the inlet air supply ductwork by at least partially restricting the ambient air inlet openings when the summer/winter doors are opened. By simultaneously restricting the inlet of cold ambient air when the winter/summer doors are opened, the percentage of warm air drawn into the engine is increased. The use of such doors also helps to maintain the original air velocity through any upstream inertial filters. By maintaining the air velocity through the inertial filters, the efficiency of the inertial filters in removing snow from the intake air is maintained. 
     There is a continued demand for improved performance of locomotive engines, in terms of fuel economy, component loading, power output and reduced emissions. To achieve such optimized performance, the conditions of combustion within the internal combustion engine needs to be controlled. However, engine designs are limited because of the extremes of environmental conditions under which a locomotive must operate. For example, cylinder peak firing pressure may become too high as the engine is operating during cold days when the inlet air temperature is very low, thus generating excessive stress on engine components. Alternatively, cylinder exhaust temperatures may become too high as the engine is operating during hot days when the inlet air temperature is very high, thus causing turbocharger damage due to overheating and overspeed. Very high inlet air temperature may also increase engine exhaust emissions such as smoke, carbon monoxide (CO), and particulate matter (PM). 
     BRIEF SUMMARY OF THE INVENTION 
     Thus, there is a need to provide a locomotive having a reduced sensitivity to the wide range of environmental conditions under which it must operate. There is further a need for a method of operating a locomotive that makes it less sensitive to changes in ambient environmental conditions. 
     Disclosed herein is an apparatus and a method for reducing the sensitivity of a locomotive engine to changes in the ambient air temperature and pressure. A method for controlling a locomotive engine is described having the steps of: providing a warm air flow path between the engine compartment and the air inlet path; providing a valve for controlling the flow of warm air through the warm air flow path; measuring the ambient air temperature; and controlling the position of the valve in response to the ambient air temperature. The method may include the further steps of: measuring the ambient atmospheric pressure; and controlling the position of the valve in response to the ambient air temperature and the ambient atmospheric pressure. 
     A locomotive is described herein including: an engine disposed in an engine compartment and operable to burn fuel with air to produce power for the locomotive; an air inlet path for directing air to the engine; a warm air flow path connected between the engine compartment and the air inlet path; a valve disposed in the warm air flow path; sensors operable to produce an ambient air temperature signal responsive to the ambient air temperature and an ambient air pressure signal responsive to the ambient air atmospheric pressure; and a controller having the ambient air temperature signal as an input and operable to produce a valve position signal responsive to the ambient air temperature signal and optionally the ambient air pressure signal, wherein the valve is responsive to the valve position signal to control the flow of warm air through the warm air flow path. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The features and advantages of the present invention will become apparent from the following detailed description of the invention when read with the accompanying drawing, in which a locomotive is illustrated having an automatic apparatus for regulating the temperature of the inlet air supplied to the engine. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The FIGURE is a schematic illustration of a locomotive  10  powered by an internal combustion engine  12  located within an engine compartment  14  of the locomotive  10 . The engine  12  may be naturally aspirated or may be a turbo-charged diesel engine provided with combustion air by compressor  16  as shown in the FIGURE. The term “combustion air” is used herein to refer to the air entering the engine cylinders, downstream of any turbocharger or supercharger. The term “air used for combustion” as used herein is meant to include the air at any point of its path, from the ambient environment outside the locomotive inlet, through the inlet air ductwork, through the turbocharger, if any, and into the engine cylinders. An engine inlet  18  for air is in fluid communication with an air inlet path  20  including ductwork  22 , a plurality of inertial filters  24 , and final air filters  26 . Ambient air is drawn through the inertial filters  24  and is directed by the ductwork  22  through the final air filters  26  to the engine inlet  18 . Air may be provided to the engine  12  from the engine compartment  14  through a warm air flow path  28 . The term “warm air flow path” is used herein, however, air provided there through could be conditioned to a temperature lower than the ambient air temperature. Such a cooled air flow path embodiment is not being implemented by the assignee of the present invention at the present time. The warm air flow path  28  may be as simple as an opening in the air inlet ductwork  22 , or it may include a separate arrangement of ductwork  29  for selectively drawing conditioned air from predetermined locations within the engine compartment  14 . Valve  38  is disposed within the warm air flow path  28  and is operable to control the flow of warm air through the warm air flow path  28 . Valve  38  may be a moveable door formed in ductwork  22 , or it may be some form of butterfly, ball or gate valve or other such device operable alternatively to permit and to restrict air flow. The geometric type, size and flow area of the valve  38  are selected to be suitable for the air flow performance and capacity required for a particular application. Valve  38  may include one or a plurality of individual valves. The open/close position of valve  38  is controlled by an actuator  40  operable to move valve  38  from a first position wherein no warm air is provided to the combustion air inlet path  20 , to a second open position wherein warm air is permitted to flow through the warm air flow path  28  to the engine inlet  18 . Valve actuator  40  may be any such device known in the art, such as for example an electrical solenoid, a motor driven actuator, a hydraulic or a pneumatic actuator. 
     The warm air flow path  28  may include inlets located at more than one location within the engine compartment  14 . For example, one inlet  30  for warm air flow path  28  may be located proximate an exhaust pipe of engine  12  in order to draw air warmed to a very high temperature. A second inlet  32  may be located away from the hottest parts of engine  12  in order to draw air warmed to a lesser degree. The distribution of air flowing from inlets  30 ,  32  may be controlled by the positioning of valves  34 ,  36 , respectively. 
     The positioning of valve  38  by actuator  40  is controlled by controller  42 . Controller  42  may be any such device known in the art, such as a computer or microprocessor, a programmed logic controller, or a simple electromechanical device. Controller  42  may include a set of programmed logic instructions for the control of the temperature and/or density of the combustion air. Controller  42  may receive as input one or more of the following input signals: an ambient air temperature signal T A , an ambient atmospheric pressure signal P A , an inlet air temperature signal T I , and an inlet air pressure signal P I . An ambient temperature sensor  44  is operable to sense the temperature of the ambient air being drawn into locomotive  10  and to generate signal T A  in response to that air temperature. Ambient temperature sensor  44  may be any such device known in the art, such as for example a resistance temperature detector (RTD). Similarly, ambient atmospheric pressure sensor  46  is operable to generate signal P A  responsive to the ambient barometric pressure surrounding the locomotive  10 . Ambient atmospheric pressure sensor  46  may be any such devise known in the art. Inlet air temperature sensor  48  is located proximate the inlet  18  of engine  12 , in order to sense the temperature of the air being drawn into engine  12 . Inlet air temperature sensor  48  may be an RTD or other known device. The inlet air temperature is directly related to the ambient air temperature and to the position of valve  38 , therefore, inlet air temperature signal T I  is an indirect measure of the ambient temperature, Inlet air pressure sensor  58  senses the pressure of the inlet air at a location downstream of final air filters  26 . 
     Controller  42  is operable to generate a valve position signal V operable to control valve actuator  40  to position valve  38  to a desired position. The performance of internal combustion engine  12  may depend upon the density of the air supplied to the engine  12 . Once an inlet air density range for preferred operation of engine  12  is established by the engine designer, a corresponding inlet air temperature range may be determined based upon the relationship of air temperature and air pressure to air density. In one embodiment, controller  42  is programmed to provide an appropriate valve position signal V in response to the single variable of the measured ambient air temperature T A . In this manner, the inlet air temperature being supplied to the engine  12  may be maintained within the calculated inlet air temperature range corresponding to the preferred inlet air density range. For example, when the ambient air temperature T A  drops below a predetermined value, valve position signal V may be provided to the valve actuator  40  to open valve  38 , thereby providing warm air to mix with the ambient air within the combustion air inlet path  20 . 
     Because the density of the inlet air may vary depending upon the altitude and weather conditions encountered by the locomotive  10 , it may be desired to adjust the determined inlet air temperature range to take into account the actual ambient atmospheric pressure. Controller  42  may include logic for utilizing signal P A  when generating valve control signal V. Such logic may function to somewhat increase the temperature of the inlet air when the locomotive encounters a relatively high ambient atmospheric pressure. 
     In a further embodiment, controller  42  may utilize signal T I  as a direct indication of the temperature of the inlet air, and may generate valve control signal V in response to the inlet air temperature signal T I . A simple logic that may be implemented in controller  42  is to provide a valve position signal V to open valve  38  when the temperature of the inlet air T I  is below a predetermined value, and to close valve  38  when T I  is above a predetermined value. The predetermined value may be a fixed parameter, or it may be a calculated number corresponding to a measured ambient atmospheric pressure signal P A . The predetermined values for opening valve  38  and for closing valve  38  may be different numbers in order to avoid unnecessary cycling of the valve. 
     The specific logic utilized in controller  42  for the control of the inlet air temperature may vary depending upon the specific requirements of a particular application. For a typical locomotive engine  12 , it may be sufficient to control valve  38  to only two alternative positions, fully open and fully closed. Alternatively, valve  38  may have a plurality of discrete intermediate positions between a fully open position and a fully closed position, or an infinitely variable range of motion there between. If more than one valve  38  is provided, controller  42  may generate a corresponding plurality of valve control signals to open the individual valves in sequence, thereby providing a finer degree of control. Furthermore, controller  42  may also be programmed to generate control signals V 34  and/or V 36  to control the position of valves  34 ,  36  to further affect the temperature of the warm air passing through the warm air flow path  28 . By individually or jointly controlling the positions of valves  34 ,  36 ,  38 , a wide ranger of ambient air temperatures may be moderated to achieve a preferred range of temperatures for the air provided at inlet  18 . 
     With valve  38  in the closed position, the air pressure and density in ductwork  22  is slightly lower than in the ambient air due to the restriction imposed by the inertial filters  24 . As valve  38  is opened to admit hotter and less dense air from the engine compartment at a pressure slightly above ambient air pressure, the pressure in ductwork  22  will rise slightly, thereby offsetting to some extent the desired reduction in inlet density afforded by the warm engine compartment air mixing with the cold ambient air. Because the pressure differential across the inertial filters  24  is now reduced, it is known that their filtering performance may be degraded also. And as long as the pressure in ductwork  22  is below ambient air pressure, there will continue to be some cold, dense air coming through the inertial filters  24 , thus limiting how high the inlet air temperature can be raised (and the inlet air density lowered) by opening valve  38 . To improve the performance of this system, there may also be provided a means for restricting the flow of ambient air through one or more of the plurality of inertial filters  24  during periods when valve  38  is positioned to permit the flow of air through warm air flow path  28 . One such means may be a door  56  operable in conjunction with valve  38  to block the flow of air through one or more of the inertial filters  24  when valve  38  moves away from a fully closed position. Door  56  may have a separate actuator or may be moved in conjunction with valve  38  by actuator  40 . Other means for restricting the flow of air through filters  24  may include flow control valves associated with one or more of the individual inertial filters  24 . By decreasing the total flow area through the inertial filters  24  when air is being supplied through the warm air flow path  28 , the pressure in ductwork  22  may be maintained at a level sufficiently below ambient pressure such that the air velocity in, and the filtering performance of, the remaining inertial filter(s)  24  may be maintained. Decreasing the flow area through the inertial filters  24  will also induce a higher percentage of the inlet air to be drawn through the warm air flow path  28 , and by this means will increase the extent to which the temperature of the inlet air may be raised (and the inlet air density lowered). Finally, because the pressure in the inlet ductwork  22  is lowered by decreasing the flow area through the inertial filters  24 , the closing of door  56  may be used to prevent, at least to an extent, the inlet ductwork  22  pressure from rising when valve  38  is partially or fully opened. 
     A pressure sensor  58  measures the pressure of the air within inlet air path  22  downstream of final air filters  26 . Pressure sensor  58  provides a signal P I  corresponding to that pressure to controller  42 . In the prior art it is known to monitor the pressure differential across air filters and to restrict the power output of engine  12  if that difference exceeds a predetermined value. The pressure differential across the final air filters may be measured indirectly by comparing the ambient air pressure and the pressure of the air within duct  22  downstream of final air filters  26 . This protection scheme prevents adverse effects on the engine  12  due to clogged filters, and it provided an indication to the operator that maintenance was needed on the filters  26 . A build-up of snow and/or ice on the final air filters  26  could also result in the pressure differential set point being exceeded. To alleviate this situation, in one embodiment of the present invention, controller  42  may provide a signal to open, or to more fully open, valve  38  when the pressure differential across the filters exceeds a predetermined value at times when the ambient temperature is below a predetermined value, such as the freezing temperature of water. Similarly, that signal may be used to control door  56  to fully restrict the flow of air through its associated inertial filters  24 . This control scheme is designed to avoid any reduction in engine power resulting from accumulated snow or ice. Controller  42  would included programmed logic operative to compare the signals from ambient pressure sensor  46  and inlet air pressure sensor  58 , and when the indicated pressure differential exceeds a predetermined value and the ambient temperature as measured by sensor  44  is below a predetermined value, to issue a valve position control signal V to more fully open valve  38  and/or to close door  56 . The set point for this valve opening action is preferably a differential pressure value less than the pressure differential resulting in a reduction in the power output of the engine  12 , 
     While the preferred embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those of skill in the art without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.