Abstract:
A method and apparatus of operating a turbo-charged diesel locomotive engine to facilitate controlling pressure in an engine cylinder is provided. The method includes determining an allowable peak firing pressure for the turbo-charged diesel engine, determining an actual peak firing pressure, and comparing the allowable peak firing pressure to actual peak firing pressure to control the operation of the turbocharger for controlling peak firing pressure. The apparatus includes a diesel engine including an intake manifold, an exhaust manifold, an electronic fuel controller, a turbo-charger, and a motor-generator coupled to the turbocharger and operable to at least one of increase turbocharger rotational speed, decrease turbocharger rotational speed, and maintain turbocharger rotational speed, and a controller including a first input corresponding intake manifold air pressure and a second input corresponding to fuel injection timing for the engine and including as an output a motor-generator configuration signal.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of rail locomotives, and more particularly to methods and apparatus for controlling a turbo-charged diesel locomotive engine. 
     Excessively high pressure in an operating cylinder of an internal combustion engine may cause damage to the engine pistons, cylinder heads, and other components. Peak firing pressure (PFP) is affected by the combustion process and the conditions of the incoming combustion air. In addition, the operation of a turbo-charger increases peak firing pressure by increasing the temperature and pressure of the incoming air. 
     Locomotives encounter a variety of operational conditions ranging from extreme cold at sea level to hot temperatures at high altitudes. These conditions may induce various engine parameters to exceed designed engine limits, for example, peak firing pressure (PFP), turbocharger speed (TS), and preturbine temperature (PTT). More specifically, the parameters are more susceptible to being exceeded when the engine is running at full load at extreme ambient temperature and/or altitude conditions. 
     There is also a continued demand for improved performance of locomotive engines, in terms of fuel economy, component loading, power output and reduced emissions. To facilitate optimized engine performance, conditions of combustion within the internal combustion engine should be controlled. However, engine designs are limited because of the extremes of environmental conditions under which a locomotive must operate. For example, cylinder PFP may become too high when an engine is operating during cold days and when the inlet air temperature is low, thus generating excessive stress on engine components. Alternatively, cylinder exhaust temperatures may become too high when the engine is operated during hot days and when the inlet air temperature is very high, thus causing turbocharger damage due to overheating and overspeed. 
     To facilitate controlling PFP, TS and PTT the engine may be operated with a power derate such that the engine is operated at lower than rated horsepower. However, derated engine operation is undesirable because it unnecessarily limits the operational capability of the locomotive. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a method of operating a turbo-charged diesel locomotive engine to facilitate controlling pressure in an engine cylinder is described. The method includes determining an allowable peak firing pressure for the turbo-charged diesel engine, determining an actual peak firing pressure, and comparing the allowable peak firing pressure to actual peak firing pressure to control operation of the turbocharger for controlling peak firing pressure. 
     In another aspect, a method of operating a turbo-charged diesel locomotive engine to facilitate preventing damage from turbocharger failure is described. The method includes determining an allowable turbine speed for the turbocharger, determining an actual turbine speed, and comparing the allowable turbine speed to actual turbine speed to control operation of the turbocharger for controlling turbocharger speed. 
     In yet another aspect, a method of operating a turbo-charged diesel locomotive engine is described. The engine includes a turbo-charger for providing compressed air to an intake manifold of the engine, a motor-generator coupled to the turbocharger shaft, and an electronic controller receiving inputs from engine components. The method includes determining at least one of an allowable peak firing pressure for an engine cylinder, an allowable turbine speed for the turbocharger, an allowable preturbine temperature, an actual peak firing pressure as a function of at least one of an intake manifold air pressure, a manifold air temperature, and a timing of fuel injection into the cylinder, an actual turbine speed, and an actual preturbine temperature, using the electronic controller to compare at least one of the allowable peak firing pressure to the actual peak firing pressure, the allowable turbine speed to actual turbine speed, and the allowable preturbine temperature to the actual preturbine temperature, using the electronic controller to control the motor-generator, and operating the motor-generator to at least one of increase power input to the turbocharger shaft to increase the turbocharger rotational speed, decrease power input to the turbocharger shaft to decrease the turbocharger rotational speed, and maintain turbocharger rotational speed. 
     In still another aspect, a locomotive power unit is described. The power unit includes a diesel engine including an intake manifold for receiving compressed air, an exhaust manifold for removing exhaust, and an electronic fuel controller receiving inputs from engine components, a turbo-charger including a turbine section connected to the exhaust manifold and a compressor section including an outlet connected to the intake manifold, the turbo-charger operable to provide compressed air to the intake manifold at an intake manifold air pressure, a motor-generator coupled to the turbocharger and operable to at least one of increase turbocharger rotational speed, decrease turbocharger rotational speed, and maintain turbocharger rotational speed; and a controller including a first input corresponding intake manifold air pressure and a second input corresponding to fuel injection timing for the engine and including as an output a motor-generator configuration signal, the output being responsive to the first input and the second input; and the motor generator being responsive to motor-generator configuration signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front-side isometric view of a compression ignition diesel engine. 
     FIG. 2 is a schematic illustration of a locomotive power unit. 
     FIG. 3 is a schematic diagram of peak firing pressure logic. 
     FIG. 4 is a schematic diagram of turbocharger turbine speed and preturbine temperature logic. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a front-side isometric view of a compression ignition diesel engine  10  and-includes a turbo charger  12  and a plurality of power cylinders  14 . For example, a twelve-cylinder engine  10  has twelve power cylinders  14  while a sixteen-cylinder engine  10  has sixteen power cylinders  14 . Engine  10  also includes an air intake manifold  16 , a fuel supply line  18  for supplying fuel to each power cylinder  14 , a water inlet manifold  20  used in cooling engine  10 , a lube oil pump  22  and a water pump  24 . An intercooler  26  connected to turbo charger  12  facilitates cooling turbo-charged air before it enters respective power cylinder  14 . In an alternative embodiment, engine  10  is a V-type engine, wherein power cylinders  14  are arranged in an offset angle from adjacent power cylinders  14 . 
     FIG. 2 is a schematic illustration of a locomotive power unit  110 . Power unit  110  includes a diesel engine  112  including an intake manifold  114  and an exhaust manifold  116 . A turbo-charger  118  including a compressor section  120  and a turbine section  122  is operable to provide a supply of compressed air  124  to intake manifold  114  for combustion within engine  112 . Turbine section  122  is connected to exhaust manifold  116  for extracting energy from exhaust gases  126  for rotating a turbocharger shaft  128  that is connected to compressor section  120 . Compressor section  120  draws ambient air  130  through a filter  132  and provides compressed air  124  through an outlet  134  connected to a heat exchanger  136 , and then to intake manifold  114 . Compressed air  124  is heated to an elevated temperature by compression, and is passed through heat exchanger  136  such that the temperature of air  124  is reduced prior to delivery into engine  112 . In an exemplary embodiment, heat exchanger  136  is an air-to-water heat exchanger which utilizes engine coolant to facilitate removing heat from compressed air  124 . In an alternative embodiment, heat exchanger  136  is an air-to-air heat exchanger which utilizes ambient air to facilitate removing heat from compressed air  124 . 
     Power unit  110  also includes a controller  138 . In the exemplary embodiment, controller  138  is an electronic fuel injection controller for engine  112 . In an alternative embodiment, controller  138  is an electronic logic controller that is programmable by a user. Controller  138  receives a throttle setting signal  140  from an operator controlled throttle  142 , and includes circuitry  143  operable to produce timing signal  144  for controlling the operation of fuel injector  145  for injecting fuel into a plurality of cylinders  146  of engine  112 . A piston  147  is slidingly disposed in each cylinder  146  and reciprocates between a top dead center position and a bottom dead center position. Controller  138  also receives an intake manifold air pressure signal  148  generated by a pressure transducer  150 , an intake manifold air temperature signal  152  generated by a temperature sensor  154 , and a preturbine temperature signal  155  generated by a temperature sensor  156 . 
     Power unit  110  also includes an electric motor-generator (MG)  157  for facilitating controlling the peak pressure in cylinder  146  of engine  112 . MG  157  is mechanically coupled to turbocharger shaft  128  and receives an electrical control signal  158  from controller  138 . MG  157  is operable to supply power to shaft  128  or remove power from shaft  128 . When MG  157  is operated as a motor, power is supplied to turbocharger shaft  128 , in addition to power supplied from turbine section  122 , which increases turbocharger  118  speed and forces additional air into cylinders  146 . Conversely, when MG  157  is operated as a generator, MG  157  is an additional load induced to turbocharger  118 , which decreases turbocharger  118  speed and reduces the amount of combustion air entering into cylinders  146 . By reducing the amount of compressed air  124  being provided to engine  112 , MG  157  functions to reduce intake manifold air pressure, and to therefore reduce the peak pressure in cylinder  146 . In addition, the heat demand on heat exchanger  136  is also reduced when MG  157  is operating in a generator configuration. The operational configuration of MG  157  is controlled by controller  138 . A turbocharger speed sensor  159  is responsive to a speed of turbocharger  118  and sends a turbocharger speed signal  160  to controller  138 . 
     FIG. 3 is a schematic diagram of peak firing pressure logic  250  that may be embodied within controller  138  as hardware, software, or firmware for controlling PFP. Controller  138  receives inputs MAP  148 , MAT  152  and timing signal  144  that is representative of the timing of the operation of fuel injectors  145 . Each input&#39;s contribution to a rise in cylinder pressure is calculated, and an actual peak firing pressure is determined and compared to an allowable peak firing pressure. Based on the result of these calculations, controller  138  changes the operating configuration of MG  157 . 
     A rise in pressure due to the compression effect of the piston moving upward in the cylinder, also called the polytropic pressure rise, can also be determined. The pressure rise is a function of MAT  152 , and a relationship between MAT  152  and a rise in cylinder pressure is an engine-specific function that is determined through modeling and/or empirical techniques. The relationship between MAT  152  and a rise in cylinder pressure is programmed into controller  138  such that the polytropic pressure rise in cylinder  146  over the intake air manifold pressure is determined  260  as a function of MAT  152 . 
     A pressure rise in cylinder  146  over the polytropic pressure rise that results from combustion of fuel in cylinder  146  is also calculated or measured. This pressure rise is a function of a timing of fuel injection into cylinder  146 . This relationship is also programmed into controller  138  so that the combustion pressure rise is calculated  262  as a function of timing. 
     The actual intake manifold air pressure also has an effect on the rise in pressure in cylinder  146 . MAP signal  148  is input  264  and is the base from which the polytropic rise in pressure contributions from MAT  152  and timing  144  are calculated. 
     An allowable peak firing pressure is determined for an engine design based upon design parameters of the engine. The allowable pressure is a fixed maximum value or is a target range providing a desired level of engine performance. Allowable peak firing pressure is determined  266  as a fixed value, or is calculated as a function of throttle setting signal  140 , since in some applications the desired allowable pressure may vary during different engine operating conditions. In an alternative embodiment, the allowable peak firing pressure is a desired peak firing pressure, which may be the same or a different value from allowable peak firing pressure depending on for, example, operation needs of the engine. 
     An actual peak firing pressure is calculated  268  by combining the results of steps  260 ,  262  and  264 . In an alternative embodiment, actual PFP is measured using a sensor in communication with cylinders  146 . 
     The allowable PFP from step  266 , and actual PFP from step  268  are compared  270 . If the result of comparison  270  shows actual PFP to be greater in magnitude than allowable PFP, controller  138  sends  271  signal  158  to MG  157  to configure MG  157  as a generator to remove power from shaft  128  and reduce a speed of turbocharger  118 . Reducing turbocharger  118  speed facilitates reducing MAP  148  and MAT  152 . Such reductions in MAP  148  and MAT  152  are used in step  268  and a lower actual PFP is calculated. The lower actual PFP is again compared  270  to allowable PFP. Controller  138  is programmed to periodically repeat logic  250  to readjust the configuration of MG  157  in response to changes in throttle position  142 , ambient air temperature, or pressure, or other interrelated variables. MG  157  is controlled to change its configuration in a single step, in incremental steps, or in a fully proportional manner, depending upon the system design requirements and the capabilities of MG  157 . Logic  250  is repeated until actual PFP is not greater than allowable PFP wherein actual PFP is compared  272  to allowable PFP. If actual PFP is lesser in magnitude than allowable PFP, controller  138  sends  274  signal  158  to MG  157  to configure MG  157  to freewheel, meaning to allow turbine section  122  to control the speed of turbocharger  118 . If controller  138  was already commanding MG  157  to freewheel, controller issues a signal  158  to MG  157  to configure MG  157  as a motor to add power to shaft  128  and increase the speed of turbocharger  118 . The sequence continues until at step  270 , actual PFP is determined to be not greater than allowable PFP and at step  272 , actual PFP is determined to be not less than allowable PFP controller  138  commands  276  MG  157  to maintain the speed of turbocharger  118 . The above sequence describes a closed loop control scheme that maintains actual PFP at the allowable PFP value over a wide range of operations of engine  10 . 
     FIG. 4 is a schematic diagram that illustrates logic  300 , which may be embodied within controller  138  as hardware, software, or firmware for controlling the speed of turbocharger  118  and for controlling preturbine temperature  155 . Design limits of turbocharger  118  determine a maximum speed turbocharger  118  is allowed to rotate. Exceeding such limits may cause failure of a blade or other rotating components within turbocharger  118 . PTT is limited to prevent exceeding a maximum allowable temperature of components located within turbocharger  118 . Turbocharger  118  components are subjected to corrosive gases, high temperature, and intense stress due to rotational forces. Design limits on these parameters reduce a probability of failure of turbocharger  118 . 
     Inputs MAP  148 , timing  144 , and PTT  155  are used determine  300  actual turbocharger speed. In an alternative embodiment, actual turbine speed is measured directly. An allowable turbocharger speed is determined  366 , which may be a fixed value. In an alternative embodiment, allowable charger speed is determined  366  based on MAP  148 , PTT  155 , and other interrelated variables. For example, at lower PTT  155  temperature ranges, where a temperature stress on components in turbine section are less than at higher temperatures, it may be possible to extend the allowable turbine speed to higher values before total stress on the components of turbine section  122  become excessive. An allowable preturbine temperature is determined  367 . Allowable preturbine temperature may also be a fixed value or may be determined  367  as a function of interrelated variables. 
     PTT  155  is compared  370  to allowable preturbine temperature as determined  367  and actual turbine speed as determined  368  is compared to allowable turbine speed as determined in step  366 . If actual PTT  155  is greater than allowable PTT or actual turbine speed is greater than allowable turbine speed, controller  138  sends  371  signal  158  to MG  157  to configure MG  157  as a generator to remove power from shaft  128  and reduce a speed of turbocharger  118 . If actual PTT  155  is not greater than allowable PTT and actual turbine speed is not greater than allowable turbine speed, controller  138  sends  376  signal  158  to MG  157  to configure MG  157  to freewheel and allow turbine section  122  alone to control a speed of turbocharger  118 . Controller  138  is programmed to periodically repeat the steps of FIG. 4 to readjust the configuration of MG  157  in response to changes in throttle position  142 , ambient air temperature, or pressure, or other interrelated variables. 
     In the exemplary embodiment, controller  138  is embodied within an existing electronic fuel injection controller of a locomotive. Such fuel injection controllers include logic and calculation capability, and may be embodied as a programmed logic controller, microprocessor, or personal computer. Electronic fuel injection controller  138  has inputs for intake manifold air pressure  148  and temperature signals  152 , and for a throttle setting signal  140  and includes a fuel injection timing signal  144  as an output. Therefore, the additional logic necessary to produce a MG configuration signal  158  is included by additional programming of software or firmware within controller  138 . MG configuration signal  158  may be programmed to be responsive to the intake manifold air pressure signal  148  and the timing signal  144 . MG configuration signal  158  may further be programmed to be responsive to the intake manifold air temperature signal  152 , and/or the throttle position signal  140 . Controller  138  may be programmed to provide a default signal to freewheel MG  157  in the event of any system malfunction, such as a bad sensor or broken wire, etc. 
     While the present invention is described in the context of a locomotive, it is recognized that the benefits of the invention accrue to other applications of diesel engines. Therefore, this embodiment of the invention is intended solely for illustrative and exemplary purposes and is in no way intended to limit the scope of application of the invention. 
     The above-described diesel engine fuel injection systems are cost-effective and highly reliable. Each system includes an injector that injects fuel into a diesel engine combustion air volume such that a homogeneous fuel/air mixture results early in the engine cycle. Such injection facilitates complete burning of the fuel at lower temperatures resulting in less particulate emissions being formed and less NOx being generated. As a result, the fuel injection system facilitates reducing engine emissions in a cost-effective and reliable manner. 
     Exemplary embodiments of diesel engine fuel injection systems are described above in detail. The systems are not limited to the specific embodiments described herein, but rather, components of each system may be utilized independently and separately from other components described herein. Each diesel engine fuel injection systems component can also be used in combination with other diesel engine fuel injection systems components. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.