Abstract:
Methods and apparatus for controlling an engine having a first maximum power rating based on at least a first predetermined operating condition of the engine. A first sensor transmits a first signal as a function of the engine operating at a predetermined operating condition other than the first predetermined operating condition. A control device receives the first signal and transmits a power signal to the engine as a function of the first signal. The power signal may, by itself, or in conjunction with other signals, cause the engine to produce a quantity of power in excess of the first maximum power rating.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates generally to an engine having a predetermined set maximum power rating based on less than ideal site and ambient conditions, and more specifically to controlling the engine to produce a quantity of power in excess of the predetermined set maximum power rating as a function of engine operating conditions.  
         BACKGROUND  
         [0002]    Many engines are coupled with generators to produce electrical power. These engines are typically configured during manufacture to produce up to a predetermined set power rating. More specifically, an engine controller is normally configured to command the engine to produce up to and no more than the predetermined maximum power rating.  
           [0003]    The predetermined maximum power rating of a particular engine is often calculated using worst case operating conditions for the engine. This is because the amount of power that the engine is capable of producing is usually limited by its operating conditions. For example, if the ambient temperature is very warm, e.g., 43 degrees Celsius, the temperature of the air or air/fuel mixture being sent to the combustion chamber cannot be as cool as a day when a substantially cooler ambient air temperature exists. Within a fairly wide range, the temperature of the air or air/fuel mixture being sent to the combustion chamber has a direct impact on engine power capability.  
           [0004]    The example in the paragraph above generally covers an operating condition where cooler water to the aftercooler (aftercooler water temperature) results in a power increase because the inlet manifold temperature is reduced. Similarly, other engine operating conditions, such as jacket water temperature, inlet manifold pressure, humidity, and whether detonation is occurring during ignition may all affect combustion, and therefore power production.  
           [0005]    Further, many engine controllers limit the power production of an engine to a predetermined set maximum power rating. Thus, even when an engine is operating in better than worst case operating conditions, the engine controller may still use predetermined worst case conditions for calculating the power output. In this instance, the engine typically produces less power than it could, with the additional power producing capabilities of the engine remaining unused.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention provides methods and apparatus for controlling an engine having a first maximum power rating based on at least a first predetermined operating condition of the engine. A first sensor transmits a first signal as a function of the engine operating at a predetermined operating condition other than the first predetermined operating condition. A control device receives the first signal and transmits a power signal to the engine as a function of the first signal. The power signal causes the engine to produce a quantity of power in excess of the first maximum power rating. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 shows a block diagram of an engine system according to one embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0008]    [0008]FIG. 1 shows a block diagram of an engine system  10  according to one embodiment of the invention. The engine system  10  will be discussed in terms of a natural gas engine, although other types of internal combustion engines, including turbines and diesels could also be used. The engine system  10  typically includes an air delivery system (not shown) that delivers air (e.g., either ambient air or air and some other combustible gas) to an air/fuel mixing device, such as a carburetor  12  or electronic fuel valve. Other types of air/fuel mixing devices known to those skilled in the art could also be used in appropriate embodiments.  
         [0009]    A fuel delivery system (not shown) also delivers fuel, e.g., natural gas, to the carburetor  12  by ways known to those skilled in the art. The carburetor  12  mixes the air and fuel, forming an air/fuel mixture.  
         [0010]    The air/fuel mixture passes through a restricting device, such as a throttle plate  14 . The throttle plate  14  controls the volume of the air/fuel mixture that passes by ways known to those skilled in the art. In embodiments of the invention, the throttle plate  14  location may be varied from what is shown in FIG. 1. For example, it may be after, rather than before an aftercooler.  
         [0011]    In embodiments of the invention that include an aftercooler  16 , such as a separate circuit aftercooler (“SCAC”), the combustion air/fuel mixture may be cooled, such as by: 1) passing the air/fuel mixture through the inside of a heater exchanger and ambient air passing over the outside (shown in FIG. 1); or 2) a cooled water passing through the inside of the heat exchanger and the contained air/fuel mixture passing over the outside of the heat exchanger core. Either system typically has a thermostat  18  to control the air/fuel mixture temperature to the engine. For SCAC system  1  (generally referred to as Air-to-Air Aftercooler (although for gaseous fueled low pressure units it should be more properly be called Air-to-Air/Fuel Mixture Aftercooler), the first thermostat  18  diverts none, some, or all of the air/fuel mixture through the aftercooler for cooling depending on the temperature of the air/fuel mixture at the first thermostat  18 . In one embodiment of the invention, the first thermostat  18  is set for 43 degrees Celsius.  
         [0012]    In other words, the first thermostat  18  will send all of the air/fuel mixture through the aftercooler  16  if the temperature of the air/fuel mixture is greater than 43 degrees Celsius. If the temperature of the air/fuel mixture is less than 43 degrees Celsius, the first thermostat  18  will cause at least some of, and more typically all of the air/fuel mixture to bypass the aftercooler  16 , through a first bypass path  20 .  
         [0013]    In other embodiments of the invention there are variations of this type of aftercooler  16  that are not thermostatically controlled and generally do not vary engine power based on ambient conditions.  
         [0014]    Both the air/fuel mixture from the aftercooler  16  and the first bypass path  20  typically enter an inlet manifold  22  and a combustion chamber (not shown) of an engine  24 . As mentioned above, the engine  24  may be any of a variety of engines known to those skilled in the art, including and not limited to natural gas, turbines, diesel, and gasoline engines.  
         [0015]    The second SCAC system described above may operate similarly except the cooling water circuit to the aftercooler  16  is thermostatically controlled. In this embodiment, the air/fuel mixture is not controlled or diverted through the first bypass path  20 .  
         [0016]    The end result in many prior art engines is that the temperature of the air/fuel mixture to the inlet manifold  22  has been predetermined to a relatively high amount based on generally a worst case expected ambient condition. This method “mechanically” restricts the engine to a less than true maximum power output.  
         [0017]    After combustion, the exhaust air and other combustion products exit the engine  24  via an exhaust path  26  by ways known to those skilled in the art.  
         [0018]    In embodiments of the invention, a heat exchanger, such as a radiator  28 , may be coupled with the engine to reduce the temperature of the engine  24 . Other types of heat exchangers known to those skilled in the art may also be used.  
         [0019]    Typically water, e.g., jacket water, or a mixture of water and other temperature conductive fluids, are flowed through a jacket (not shown) of the engine  24  via a pump  30 . A second thermostat  32  is typically used to make the jacket water bypass the radiator  28  via a second bypass path  34  when the jacket water temperature is below some predetermined temperature, such as 90 degrees Celsius. Other temperatures may be selected as appropriate.  
         [0020]    In some embodiments of the invention, the radiator  28  may include portions of the aftercooler  16  by ways known to those skilled in the art. Alternately, the aftercooler  16  may use a separate heat exchanger (not shown, but described above as SCAC system  2 ).  
         [0021]    A throttle plate control system  36  typically controls the volume of the air/fuel mixture that the throttle plate  14  allows to pass, e.g., via the position of the throttle plate  14 . In some embodiments of the invention, the throttle plate control system  36  may include an ambient air temperature sensor  38  that determines, e.g., calculates or measures, the ambient air temperature, and transmits a temperature signal TEMP indicative of the ambient air temperature.  
         [0022]    In embodiments of the invention the throttle plate control system  36  may include a humidity sensor  40  that determines the relative or specific humidity of the ambient air and transmits a humidity signal HUMIDITY indicative of the humidity.  
         [0023]    In embodiments of the invention the throttle plate control system  36  may include an inlet manifold pressure sensor  42  that determines the pressure of the air in the inlet manifold  22  and transmits an inlet manifold pressure signal IMPRESS indicative of the pressure.  
         [0024]    In embodiments of the invention the throttle plate control system  36  may include an inlet manifold temperature sensor  44  that determines the temperature of the air or air/fuel mixture in the inlet manifold and transmits a temperature signal IMTEMP indicative of the temperature.  
         [0025]    In embodiments of the invention the throttle plate control system  36  may include a detonation sensor  46  that determines when a detonation condition occurs during an ignition of the engine, and transmits a detonation signal DET indicative of the detonation. The detonation sensor  46  may, for example, detect vibrations of the engine, with detonation typically causing different vibration characteristics in the engine than normal ignition events do.  
         [0026]    In embodiments of the invention the throttle plate control system  36  may include a jacket water temperature sensor  48  that determines the temperature of the jacket water and transmits a jacket water temperature signal JWTEMP indicative of the jacket water temperature.  
         [0027]    A control device, such as a microcontroller or microprocessor  50  may be coupled with one, some, or all of the above sensors to receive their respective signals. The microprocessor  50  processes the respective signals and transmits a throttle position signal THROTTLE to the throttle plate as a function of the one, some, or all of the signals from the sensors. The throttle position signal THROTTLE controls the position of the throttle by ways known to those skilled in the art.  
         [0028]    Generally, more power may be produced by the engine  24  when one, some, or all of the following operating conditions exist: jacket water temperature is low; inlet manifold temperature is low; inlet manifold pressure is high; detonation is not occurring; ambient temperature is low; humidity is high; and aftercooler temperature is low. Often these operating conditions will be better than the worst case operating conditions, and therefore allow for more power to be produced than the otherwise predetermined set maximum power rating of the engine  24 .  
         [0029]    However, many conventional natural gas engines do not take advantage of these better than worst case conditions, and continue to command a throttle position THROTTLE as if the worst case operating conditions did exist, thereby resulting in the delivery of less power from the engine than it is capable of. Further, many conventional natural gas engines have a thermostat for the aftercooler and radiator that prevents the combustion air/fuel mixture temperature or the jacket water from being as low as they could be. For example, a unit with a 54 degrees Celsius thermostat installed in the SCAC aftercooler circuit (version 2 SCAC system) may provide on the order of 60 C inlet manifold air temperature.  
         [0030]    However on cooler days the water temperature from the SCAC radiator (part of  28 ) could be lower than 54 C. A lower water temperature in the aftercooler circuit would reduce the inlet manifold air temperature and could increase engine power capability. In this example, however, even if the ambient conditions could cool the aftercooler water to a lower temperature the aftercooler thermostat  18  would still send 54 C water through the aftercooler core and thus the inlet manifold air temperature would not change.  
         [0031]    Similarly, for version 1 of the SCAC system in a prior art system, if the temperature of the air/fuel mixture is below the rating for the first thermostat  18 , the air/fuel mixture may bypass the aftercooler  16 , even if the ambient conditions would allow the aftercooler  16  to cool the air/fuel mixture below the rating of the first thermostat  18 .  
         [0032]    This lost cooling equates to lost power. By selecting a lower temperature thermostat, such as a 32 degrees Celsius, the aftercooler temperature may use this additional cooling capability. Other temperature thermostats may be used as appropriate. The thermostat  32  for the radiator may be selected similarly.  
         [0033]    When the microprocessor  50  detects operating conditions that are better than worst case, as indicated by the various signals from the sensors, the microprocessor  50  commands the throttle position to a more open position, thereby allowing the engine  24  to produce power in excess of its otherwise worst case maximum power rating.  
         [0034]    Further, with many natural gas engines, the throttle plate  14  is never commanded beyond 90-95% for its worst case maximum power. Thus, typically an extra 5-10% of the air/fuel mixture can be made available to the combustion chamber of the engine  24 . This 5-10% may now be used due to the further opening of the throttle plate  14 .  
       INDUSTRIAL APPLICABILITY  
       [0035]    In operation, the respective sensors determine the operating conditions of the engine  24 . The microprocessor  50  processes the respective signals from the sensors. The microprocessor  50  may signal the equipment that is powered by the engine  24 , e.g., the driven equipment, that more power is available. The driven equipment may then request the higher power capability and the microprocessor  50  then commands the throttle  14  to a position as a function of the signals from the sensors and the driven equipment. Unlike many conventional throttle plate control systems, the throttle plate control system  36  may command the throttle position to full (100%) open, or as close thereto as is appropriate when the engine operating conditions are better than worst case. This may result in additional power being available from the engine  24 . Further, additional cooling of the air/fuel mixture may be achieved by appropriate selection of the thermostats for the aftercooler  16 .  
         [0036]    From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.