Abstract:
A method for detecting and responding to fugitive fueling of an internal combustion engine uses monitoring of the variability of at least one fuel-linked engine operating parameter to determine that fugitive fueling is occurring. Once fugitive fueling is detected, mitigation will be implemented so as to shut the engine down without consequential damage.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   None. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The subject matter disclosed herein relates to the detection and response of unwanted fueling of an internal combustion engine. 
   2. Discussion of the Prior Art 
   As used herein, the term “fugitive fueling” means a phenomenon in which an engine receives fuel in excess of that which a fuel controller intends to deliver, either by injectors or by another fuel delivery device. Fugitive fueling may occur in a variety of situations. For example, if an engine is operated in a hydrocarbon-contaminated atmosphere such as could occur in the event of a spill at a petroleum transfer terminal or a recycling facility, sufficient unwanted or fugitive hydrocarbons may be inducted by the air system of an engine to cause overspeed and severe engine damage. A mishap such as a vehicular accident or train wreck may create a fugitive fueling situation, too. 
   Another type of fugitive fueling occurs due to a leak in an engine lubrication system. Such a leak may occur in a turbocharger or other component connected with the engine&#39;s air inlet system. Those skilled in the art will appreciate that engines, particularly diesel engines, are capable of operating quite well on lubricating oil, including lubricating oil aspirated into the engine&#39;s cylinders as a result of leaking turbocharger seals, or failed turbocharger bearings, or as a result of damage inflicted by dropped poppet valves, or yet other sorts of internal leak paths which result in oil being inducted into the engine&#39;s air inlet system. Yet another type of fugitive fueling may occur if a fuel injector is severely impaired, so that the injector either flows more than it is directed to flow, or simply leaks. 
   A need exists for a system and method for detecting and responding to fugitive fueling prior to overspeeding, thereby allowing an engine to be stopped before uncontrolled operation occurs. 
   BRIEF DESCRIPTION OF THE INVENTION 
   According to an aspect of the invention, a method for detecting and responding to fugitive fueling of an internal combustion engine includes monitoring the time-related variability of a fuel-linked engine operating parameter and comparing the monitored variability of the operating parameter with a maximum permissible value for the variability of the operating parameter. If the monitored variability exceeds the maximum permissible value, steps are taken to mitigate improper engine operation resulting from fugitive fueling. In other words, if variability exceeds the maximum permissible value, it is concluded that fugitive fueling is occurring, and mitigation then ensues. 
   According to another aspect of the present invention, a system for detecting and responding to fugitive fueling of an internal combustion engine includes a controller for monitoring the variability of a fuel-linked engine operating parameter, with a controller including at least one sensor for measuring the value of the fuel-linked operating parameter, and a processor for calculating the variability of the measured operating parameter. A comparator compares the calculated variability of the measured operating parameter with a maximum permissible value for the variability. The controller sets a fugitive fueling flag if the result of the comparison indicates that fugitive fueling is present. Then, at least one engine shut down device, connected with the controller and activated in response to the fugitive fueling flag, stops the engine, notwithstanding the presence of fugitive fueling. 
   It is an advantage of the present method and system that fugitive fueling may be detected by means of sensors which are currently used with most internal combustion engines having advanced fuel systems. 
   It is yet another advantage of the present method and system that fugitive fueling may be detected before serious engine damage occurs. 
   Other advantages, as well as features of the present invention will become apparent to the reader of this specification. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic representation of an engine having a system for detecting fugitive fueling according to an aspect of the present invention. 
       FIG. 2  is a block diagram showing various components of the engine illustrated in  FIG. 1 . 
       FIG. 3  is a plot of engine operating parameters indicating fuel-linked parameters which may be monitored to detect fugitive fueling. 
       FIG. 4  is a flow diagram illustrating a method according to an aspect of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As shown in  FIGS. 1 and 2 , engine  10  has a crankshaft,  14 , which is coupled to an alternator,  64 . This type of arrangement is used in many pieces of engine-driven equipment, such as locomotives and open pit mining trucks and other devices such as stationary power generation systems. Engine  10  has exhaust manifold  18 , which provides exhaust to turbocharger  22 . Exhaust entering turbocharger  22  passes through exhaust turbine  26  and then through exhaust pipe  27 . Turbocharger  22  also includes compressor section  30 , which compresses air entering engine  10  through air inlet  32 , and then sends the compressed air through intercooler  36  and engine air inlet  45  to intake manifold  40 . 
   Turbocharger  22  is provided with lubricating oil by means of turbo oil supply line  23 . Oil having lubricated turbocharger  22  is sent back to engine  10  by means of return oil line  25 . 
   Engine  10  includes emergency shutdown devices such as air shutter  44  and inert gas tank  48 . Air shutter  44  cuts off intake air to engine  10  when an emergency shutdown is desired. Inert gas tank  48  fumigates, or infuses, inert gas into the engine&#39;s air inlet system through valve  50 , which is controlled by controller  52 . The inert gas may be such gases as carbon dioxide, argon, or even spent exhaust gas. 
     FIG. 2  shows additional items of hardware connected with engine  10 . Fuel system  60 , which is operated by controller  52 , may include a number of fuel injectors, with an injector typically being dedicated to each cylinder. A number of sensors,  56 , including such sensors as engine oil pressure, charge air temperature, engine speed, fuel delivery, and other types of sensors known to those skilled in the art and suggested by this disclosure, are connected with controller  52  and provide controller  52  with data needed to operate fuel system  60 . Controller  52  is also attached to battery  72 , which in the case of an engine driving an alternator, is usually an integral part of a traction device, such as a locomotive or other electrodrive vehicle. Alternator  64  is attached to a number of loads  68 , which may include a self-load capability including resistive elements which have sufficient capacity to absorb the full rated output of alternator  64 . 
     FIG. 3  is a plot illustrating fuel-linked engine operating parameters as a function of time. Specifically,  FIG. 3  illustrates engine speed, fuel delivered with fuel system  60  (Fuel Value) and engine horsepower output (GHP). The maximum permissible fueling variation is shown as being in the range of about plus or minus 10%, for a total of about 20% of the desired value of the operating parameter. This is the case with engine speed as well. The precise magnitude of the permissible variability is, however, a function of the particular operating parameter being monitored. 
   It is noted from  FIG. 3  that excessive variation is occurring in the fuel delivery and horsepower output of the engine, and these variations, which are more than 500% of the desired variation, are sufficiently egregious to compel the conclusion that fugitive fueling is occurring within the engine. In essence, controller  52  operates fuel system  60  to deliver an amount of fuel required to maintain the desired engine power output. And, with a properly operating engine which is not suffering from fugitive fueling, the variation of the fuel delivery or the resulting horsepower, should never exceed a very small fraction of the variation shown in  FIG. 3 . The uppermost plot of  FIG. 3  shows an outcome of the fugitive fueling as an overspeed condition which occurs at the maximum time of the plot and which occurs even after the engine has been initially brought to a lower speed at a reduced throttle setting. Prior to onset of the overspeed condition, however, the excessive variability of the engine speed is itself a sufficient indicator that fugitive fueling is present to permit mitigation to be implemented. 
     FIG. 4  shows a method according to the present invention, which begins with a start block at  100 . Controller  52  moves to block  104  wherein the time-related variability of at least one fuel-linked engine operating parameter is monitored. As noted above, the fuel-linked operating parameters may include such parameters as fuel delivery to the engine, engine horsepower output, or engine speed. What is important is that the measure or monitored engine operating parameter have a direct link to the fuel provided to the engine. At block  108 , controller  52  compares the variability of a fuel-linked operating parameter with a threshold value which is a maximum permissible value for the variability of the operating parameter. If the variability is less than the threshold value at block  108 , the routine continues with block  104 . If, however, the variability is greater than the threshold value at block  108 , the routine moves to block  112 , wherein the effect of the fugitive fueling is mitigated. This mitigation may begin with the setting of a fugitive fueling flag to alert an operator, whether it be a human operator or controller  52 , that fugitive fueling is occurring; the conclusion that fugitive fueling is occurring is followed by the employment of a mitigation device such as air shutter  44 , or inert gas from tank  48 , or the connection of engine  10  through alternator  64  with at least one self-load resistive element included as one of loads  68 . Normal fueling may also be cut off by an appropriate command to fuel system  60 . In any event, engine  10  will be stopped, or at least decelerated and speed-limited, before damage occurs. 
   Fuel delivery rate and its variability, and engine horsepower and its variability, may be measured either directly, in the case of fuel injectors, by noting the injector pulse width or the rack setting of the injectors. Horsepower may be determined by measuring the output of alternator  64  or by using a model running in controller  52 . Such techniques are known to those skilled in the art and are beyond the scope of the present invention. 
   The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and fall within the scope of the invention. Accordingly the scope of legal protection afforded this invention can only be determined by studying the following claims.