Abstract:
A method and system for rapidly shutting down an engine uses a rotating machine coupled to the engine as a dynamometer for stopping the engine. The rotating machine is controlled adaptively to maximize the power absorbed from the engine, thereby minimizing the amount of time needed to stop the engine.

Description:
FIELD OF THE INVENTION 
   The field of the invention relates to a system and method for rapidly shutting down an internal combustion engine in the event of an abnormal operating condition. 
   BACKGROUND OF THE INVENTION 
   The need for emergency shutdown of an internal combustion engine may arise in a variety of situations. Fugitive fueling is one such situation. As used herein, the term “fugitive fueling” means the 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, hydrocarbon 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 may occur 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 even worn valve guides. Yet another type of fugitive fueling may occur if a fuel system injector is severely impaired such that the injector either flows more than it is intended to flow, or simply leaks. These sorts of impairment will most likely occur with an unthrottled engine having fuel injection, but could occur with a carbureted engine as well. 
   U.S. Pat. Nos. 6,429,540 and 6,522,439, which are assigned to the assignee of the present invention, address methods for responding to an engine overspeed condition resulting from ingestion of lube oil into an engine&#39;s cylinders. 
   Emergency shutdown may be indicated for reasons other than fugitive fueling. For example, engine overspeeding due to a loss of governor control, or excessive vibration resulting from mechanical faults, or overtemperature, or loss of oil pressure due to leaks or oil pump impairment, all militate in favor of emergency shutdown. 
   A need therefore exists for a system employing a direct-coupled rotating electrical machine to rapidly stop an engine if an emergency condition occurs. 
   BRIEF DESCRIPTION OF THE INVENTION 
   The various embodiments of the present quick shutdown system are useful for responding to fugitive fueling of an internal combustion engine. In a first embodiment, a controller, which is operatively connected with the engine&#39;s fuel supply system and with an engine output measuring device, predicts the quantity of fuel which the engine should consume during a period of time, based upon the engine&#39;s work output. The controller compares either the actual, or an estimated quantity of fuel furnished by the fuel supply system during the predetermined period of time with the engine&#39;s work output during the same period of time. The controller sets a fugitive fueling flag if the furnished quantity of fuel is less than the predicted quantity of fuel. The controller preferably directs the fuel supply system to shut off fuel to the engine if the fugitive fueling flag is set. 
   According to another embodiment of the invention, in a diagnostic sequence, a controller periodically commands the engine&#39;s fuel supply system to change the fuel rate, while determining the engine&#39;s resulting change in work output, so as to determine the engine&#39;s responsiveness to changes in fuel rate. The controller sets a fugitive fueling flag if the engine&#39;s work output does not change in accord with the commanded change in the fuel rate. As an alternative embodiment, the controller may use engine load changes which inherently occur as a basis for determining the presence, if any, of fugitive fueling. 
   According to another embodiment, the controller directs the fuel supply system to shut off fuel if the fugitive fueling flag is set; the controller thereafter engages an emergency shutdown system if the engine does not stop when the fuel is shut off. The emergency shutdown system includes a rotating electrical machine coupled to the engine, with the rotating electrical machine having sufficient power absorbing capacity to stop the engine. 
   According to yet another embodiment, an engine output measuring device includes a rotating electrical machine coupled to the engine, with the rotating electrical machine coupled to a variable and controllable load, such that the rotating electrical machine is operated as a dynamometer. This load may be used to bring the engine speed down in case of uncontrolled fugitive fueling, in order to eliminate damage due to either overspeeding or to other internal engine system impairment. 
   According to another aspect of the present invention, the engine&#39;s fuel supply system further includes at least one sensor for directly or indirectly measuring the fuel consumed by the engine during a period of time, with the sensor being coupled to an engine controller. 
   In another embodiment, a method for detecting and responding to fugitive fueling of a reciprocating internal combustion engine is useful for triggering rapid engine shutdown. This method includes measuring fuel consumed by the engine during a period of time, and determining the engine&#39;s work output during the period of time. Then, the method predicts the quantity of fuel which the engine should have consumed during the predetermined period of time, based upon the engine&#39;s work output. The actual quantity of fuel consumed during the period of time is compared with predicted fuel consumption, and a fugitive fueling response is initiated the event that the actual quantity of fuel consumed is less than the predicted quantity of fuel. The fugitive fueling response includes the steps of commanding the engine&#39;s fuel system either to shut off, or to greatly reduce, the flow of fuel to the engine, and to engage an emergency shutdown system in the event that the engine does not stop in response to the reduction of fuel quantity. 
   According to another embodiment, if an engine having the present system is coupled to a rotating electrical machine, the engine may be loaded by means by the rotating electrical machine, commonly an alternator, if a command to shut off the fuel does not result in engine shutdown. In such case, a method of loading the engine with an electrical machine may include controlling the field current of the alternator, as well as imposing additional normal and/or auxiliary loads to maintain an increased level of power absorption as the speed of the engine decreases, and placing an adaptive load upon the alternator by means of a traction load. Additional active power absorbing/producing systems could also be used. A traction motor system may be used to control the link voltage applied to the passive load and to at least one traction motor. The alternator field current may be supplied by a bank of continuously firing rectifiers connected with a multi-phase input source. Alternatively, the alternator field current may be supplied by a direct current source. The traction motor may be operated either as a brake or as a motor so as to load the engine and thereby bring it to a stop. This method may also include controlling the alternator field current asynchronously. 
   According to another aspect of the present invention, a method for operating a reciprocating internal combustion engine having a crankshaft coupled to a traction alternator and at least one traction motor, includes monitoring a plurality of engine operating parameters, and comparing the value of each of said monitored engine operating parameters with a predetermined acceptable range of values. In the event that at least one of the monitored operating parameters falls outside of the acceptable range of values, the traction alternator will be operated with a control voltage provided by a traction motor drive to stop the engine. 
   The monitored operating parameters useful with the present method include, without limitation, engine coolant temperature; engine lubricating oil temperature; engine lubricating oil pressure; engine lubricating oil level; engine speed; engine vibration level; engine turbocharger speed; engine noise; and engine exhaust emission level. 
   It is advantage of a system and method according to the present invention that potentially destructive engine operation may be contained before the engine reaches a runaway speed or other damaging condition. 
   It is a further advantage of a system and method according to the present invention that the inventive system may be implemented without the need of additional hardware in an engine, such as an over-speed governor. 
   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 suitable for use with an emergency shutdown system according to an aspect of the present invention. 
       FIG. 2  is a block diagram representing a complete engine system according to an aspect of the present invention. 
       FIG. 3  is a flow diagram illustrating a diagnostic method useful for triggering operation of an emergency shutdown system according to an embodiment of the present invention. 
       FIG. 4  illustrates a typical traction drive which is useful in an emergency shutdown system according to one aspect of the present invention. 
       FIG. 5  is similar to  FIG. 4 , but shows a DC source for an alternator field current control according to an aspect of the present invention. 
       FIG. 6  illustrates another embodiment for using an alternator to load an engine during an emergency shutdown. 
       FIG. 7  illustrates use of a traction inverter to regulate dc link voltage according to another aspect of the present invention. 
       FIG. 8  illustrates several of the operating characteristics of an alternator useful for practicing certain aspects of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As shown in the embodiment of  FIG. 1 , engine  10  has a crankshaft,  14 , which is coupled with a load, such as alternator  64  shown in  FIG. 2 . Engine  10  has an exhaust-driven power adder embodied as turbocharger  22 . Exhaust leaving engine  10  through exhaust manifold  18  flows past turbine  26 , which drives compressor section  30 . Air drawn through air inlet  32  is compressed and flows through aftercooler  36  and then into intake manifold  40 . Lubricating oil flows to turbocharger  22  through line  23  and returns to the engine through line  25 . 
     FIG. 2  shows an embodiment of engine fuel system  60 , which is operated by controller  52 . Fuel system  60  may include either a common rail injection setup, or camshaft-driven unit injectors, or yet other types of fuel systems known to those skilled in the art and suggested by this disclosure. Controller  52  is also connected with battery  72 , which, in the case of a locomotive, may be either a traction battery, or other type of battery such as a starting battery or control system battery. Engine  10  powers alternator  64  in the present example, such as would be the case where engine  10  is installed in a diesel-electric locomotive. Alternator  64  has a number of loads,  68 , attached thereto, which may include traction motors, dynamic brake grids, or other devices. Sensors  56  include sensors for various operating parameters such as engine speed, turbocharger speed, fuel flow, engine temperature, various system current flow rates and voltages, and other operating parameters known to those skilled in the art and suggested by this disclosure. 
     FIG. 3  illustrates an embodiment of a method useful for triggering the present control scheme. Beginning at block  100  with a start command, the method moves to block  102 , wherein the fueling rate of the engine  10  is determined. Fuel rate is known from fuel system  60 , which normally includes at least one fuel injector for furnishing fuel to the engine. More probably, a separate fuel injector will be employed for each cylinder, with the precise quantity of fuel per injector stroke being controlled by controller  52 . Because controller  52  is operatively connected with fuel system  60 , controller  52  is well-suited to determine the exact amount of fuel being delivered to engine  10  at any particular period of time. 
   The determination of fuel quantity delivered to the engine&#39;s cylinders by the fuel system could also be done by using an estimate based on injector opening time, as well as upon the shape of the injector map. Speed regulator controller effort could also be employed for this purpose. The precision of the estimated fuel consumption value may be improved by correcting for ambient air pressure and temperature according to the formula 1/(((0.0005386*T)+0.96768)*(14.135/P) 0.093 , where T is the temperature is degrees F., and P is the absolute pressure in pounds per square inch. Additional compensation could be based on the energy content of the fuel. 
   After block  102 , the method continues with block  104 , wherein power output is predicted as a function of the previously determined fuel rate. The power output is predicted according to models or by a lookup table, or yet other methods known to those skilled in the art and suggested by this disclosure. Such lookup tables or analytical methods may include various factors such as trending/history (prior performance of the system at the same or comparable operating conditions) or operation of similarly designed systems. 
   After determining the predicted power output at block  104 , the method moves to block  106 , wherein the actual power output of engine  10  is determined. To do this, alternator  64  may be operated as a virtual dynamometer. In other words, knowing the operating parameters of alternator  64 , such as rotational speed and alternator field current, it is possible for controller  52  to determine the precise power output of the engine  10 . Another option is to monitor the output power by measuring the output voltage and current. Of course, power and work are related by time, and work output of engine  10  is merely time integrated sum of its power output. 
   At block  108 , the method compares the actual output of engine  10  with the predicted output of the engine. In the event that the actual power output, or work, is not greater than the predicted output, the routine recycles to block  102 . If, however, the actual output is greater than the predicted output at block  108 , the routine moves to block  110 , wherein a fugitive fueling flag is set and controller  52  commands fuel system  60  to shut off fuel to the engine. The comparison at block  108  may include thresholds or tolerances to account for inaccuracies in the data underlying the comparison. Moreover, transient capability could be part of the comparison. In essence, at block  108  the method determines whether fugitive fueling is present. 
   The method looks to see whether engine  10  has stopped at block  112 . If engine  10  did stop, the method concludes at block  116 . If, however, engine  10  is not stopped at block  112 , the method moves to block  114 , where emergency shutdown procedures are initiated in response to the fugitive fueling flag. With certain engines, it may be desirable at block  110  to reduce fuel flow to an idle value, rather than to cut off the flow altogether. With other engines, emergency shut down procedures may be initiated simultaneously with the fuel shut off command. 
   Those skilled in the art will appreciate in view of this disclosure that the method disclosed in  FIG. 3  is merely exemplary of a class of methods in which an engine operating parameter is compared with a predetermined range, with emergency shutdown being ordered in the event that the measured parameter lies outside of the desired range. For example, if engine temperature exceeds a predetermined threshold, or if engine oil pressure is less than a predetermined threshold, immediate engine shutdown may be indicated. 
   In the event that an emergency stop is indicated, engine  10  is loaded with alternator  64  to quickly bring the engine to a halt by controlling the field current of alternator  64 , as well as the load imposed upon the alternator, adaptively, so as to maintain power absorption at a high level as the speed of engine  10  decreases. The adaptive load is placed on the alternator by using both a passive load and a traction motor system. A traction motor drive may be employed to control the link voltage, which is applied to the passive load and to the traction motor. The alternator field current may be supplied by a bank of continuously firing rectifiers connected with a multi-phase input source, or with a direct current source. If this mode of emergency shutdown is used, traction motors, such as in a diesel electric locomotive or other large electrodrive vehicle, may be employed as either a brake or a motor. 
     FIG. 4  shows a typical traction drive used in heavy haul applications such as locomotives and mining equipment. Alternator  200  is directly driven by engine  10  (not shown). The alternator field is controlled by phase controlled rectifiers (AC to DC converters)  202 . The output of alternator  200 , which is rectified by rectifiers  204 , supplies DC bus  206 . Resistor bank  208 , connected to bus  206 , is used to dissipate braking energy. A traction motor drive, including AC motor  210 , is also connected to DC bus  206 . 
     FIG. 8  illustrates various alternator system operating characteristics. Voltage/current characteristics for different alternator field currents (if 1 , if 2  . . . if 9 ) are shown. A constant power line is also shown. In the example of  FIG. 8 , the maximum power can be transmitted when the DC link voltage is at level v 1 , for a given field current of if 6 . If the voltage is above or below this level, the power delivered by the alternator, and therefore, the torque applied to bring the engine speed down, is reduced. Various methods can be used to control the power. The first method is by controlling the alternator field current. Generally, the higher the field current, the greater the power transfer. In general, this method has a slower response characteristic due to the large inductance typically present in the field. Moreover, the phase controlled rectifier control generally loses synchronization if the input frequency changes too fast. This generally happens if the engine is slowing down quickly. Therefore, in the emergency shutdown mode, SCRs  202  are continuously fired (without regard to synchronization) until the maximum field current is produced. The power transfer is maximized by optimizing the DC link voltage. Resistor bank  208  is connected to DC bus  206 . 
   The DC link voltage can be controlled by choppers (not shown). Typically, however, choppers are not used because a DC signal is available to control the link voltage. In such case, and even if choppers are used, the traction inverters are used to control the maximum power transfer. For example, when resistor bank  208  and traction motor  210  are connected, if the operating point is at v 2  in  FIG. 8 , then traction motor drives S 1 -S 6  (shown at  212  in  FIG. 4 ) are controlled so that motor  210  transiently produces more motoring torque, so as to bring the DC link voltage from v 2  to v 1 . Because the time required to bring the engine speed to an acceptable level is less than a few seconds and may be even fraction of second, the effect of transient traction load is minimal. On the other hand, if the operating voltage is v 3 , then the traction load is reduced so as to bring the voltage to v 1  from v 3 . In some cases, traction motor  210  may have to be driven even into braking. In this case, resistor bank  208  will dissipate the power from the engine driving alternator  200 , as well as the power from the traction motor. 
     FIG. 5  shows a similar system to that of  FIG. 4 , except that the field control is replaced by a DC source,  214 . Although a battery is shown, any DC source could be used. 
     FIG. 6  shows another method for controlling the power transfer through an alternator/traction motor system. In this case, unlike  FIGS. 4 and 5 , the alternator output is connected to a controlled rectifier (either step down—using a phase controlled rectifier if the DC link voltage needs to be brought down or a 3 phase pulse width modulated rectifier if the DC link voltage needs to be increased). In this case, when the DC link voltage is changed, the power consumed by the resistor bank  208  and the power flow from alternator  200  is also changed. In this configuration, resistor bank  208  and its control, the traction motor drive, the alternator output rectifier and the alternator field current could all be controlled to get the maximum power transfer from alternator  200  so as to bring the engine speed down as fast as possible. The engine can be brought down to very low speeds and can even be driven in the opposite direction. 
   As the engine speed comes down, the traction inverter, or any other AC source, such as another inverter, could be used to regulate the DC link voltage through a circuit represented by resistor  218  and inductor  220 , with the alternator inverter being controlled to produce the maximum torque. This operation is very similar to engine cranking operation as described in U.S. Pat. Nos. 4,585,983 and 6,023,137. This type of control, as shown in  FIG. 7 , can be used to generate and control high torques at low speeds. This can also be used to bring the engine speed to 0. 
   The quick shutdown capability afforded by alternator  200 , either with or without assistance from traction motor  210 , may be used in case of engine impairment, or abnormal operating conditions other than fugitive fueling. Such impairment, as well as unwanted operating conditions having the potential for causing engine damage could be detected by monitoring such engine operating parameters as turbocharger speed, turbocharger inlet temperature, intake manifold temperature, intake manifold pressure, exhaust temperature, oil pressure and/or temperature and/or flow, fuel pump operation, fuel pressure/flow, fuel injector and control operation, engine speed, crankcase pressure, coolant flow, coolant temperature, vibration, and other operating parameters. Each monitored parameter may be compared with a predetermined acceptable range, as disclosed in the method of  FIG. 3 , with the rapid stopping procedure being initiated in the event that the monitored parameter, or group of parameters, falls outside an established range. 
   While particular embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.