Abstract:
A power generating set includes an engine operable in response to a flow of fuel to produce a flow of exhaust gas, a generator coupled to the engine and operable in response to operation of the engine to produce a total electrical power, and a primary load electrically connected to the generator to receive a portion of the total electrical power, the primary load having a cyclical pattern. A battery bank is selectively connected to the generator to receive a portion of the total electrical power and an insulated-gate bipolar transistor (IGBT) is positioned to selectively transition between a connected state and a disconnected state. The battery bank is connected to the generator to charge the battery bank when the IGBT is in the connected state and is disconnected from the generator when the IGBT is in the disconnected state.

Description:
RELATED APPLICATION DATA 
       [0001]    This application is a continuation of U.S. application Ser. No. 14/267,975 filed May 2, 2014, now U.S. Pat. No. X,XXX,XXX, which claims priority to U.S. Provisional Application No. 61/818,532 filed May 2, 2013, the entire contents of each are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to the arrangement and operation of a diesel engine system. More particularly, the invention relates to the arrangement and operation of a diesel engine system that powers a highly cyclic load. 
         [0003]    Diesel engines are often used to provide an efficient and compact source of power. Diesel engines can be used in mobile applications, such as in a truck, a locomotive, a ship, or other vehicle. In addition, diesel engines are often used to provide power in stationary applications such as portable or standby generators, air compressors, pumps, and the like. 
         [0004]    Diesel engines are known to produce particulate emissions (soot) during operation under certain conditions. In some applications, filters are employed to capture the soot and reduce the particulate emissions of the engine. 
       SUMMARY 
       [0005]    In one construction, the invention provides a diesel engine that includes a particulate filter in the emission stream of the diesel engine. The engine is arranged to drive a cyclic load and an auxiliary load. The auxiliary load is variable to maintain the total load on the diesel engine above a predetermined load point for 100 percent of the operating cycle of the load or to maintain the total load on the diesel engine above a second load point for between 10 percent and 40 percent of the cycle of the cyclic load. The second load point is higher than the first load point. In preferred constructions, the second load point is maintained for between 15 percent and 30 percent of the cycle of the cyclic load. 
         [0006]    In one construction, the invention provides a power generating set that includes an engine operable in response to a flow of fuel to produce a flow of exhaust gas. A generator is coupled to the engine and is operable in response to operation of the engine to produce a total electrical power, a primary load is electrically connected to the generator to receive a portion of the total electrical power, and a secondary load is selectively connected to the generator to receive a portion of the total electrical power. An insulated-gate bipolar transistor (IGBT) is positioned to selectively transition between a connected state and a disconnected state. The secondary load is connected to the generator when the IGBT is in the connected state and is disconnected from the generator when the IGBT is in the disconnected state. 
         [0007]    In another construction, the invention provides a power generating set that includes a generator operable to produce a total electrical power, an engine operable in response to a flow of fuel to drive the generator and to produce a flow of exhaust gas having an exhaust gas temperature, and a particulate filter positioned to receive the flow of exhaust gas from the engine and to filter particulate matter from the exhaust gas. A primary load is electrically connected to the generator to receive a portion of the total electrical power, the primary load being cyclical in nature. A secondary load is selectively connected to the generator to selectively receive a portion of the total electrical power and a switching element is operable to selectively transition between a connected state and a disconnected state. The secondary load is connected to the generator when the switching element is in the connected state and is disconnected from the generator when the switching element is in the disconnected state. A controller is operable to vary the state of the switching element to maintain an engine parameter above a predetermined value for a predetermined portion of each cycle of the primary load to regenerate the particulate filter. 
         [0008]    In yet another construction, the invention provides a method of operating a power generating set. The method includes operating an engine to drive a generator, generating a total electrical power during generator operation, and switching a switching element between a connected state and a disconnected state to selectively direct a portion of the total electrical power to a secondary load when the switching element is in the connected state. The method also includes directing the remaining total electrical power to a primary load, the primary load being cyclical in nature and regenerating a particulate filter by moving the switching element between the connected state and the disconnected state to maintain an engine parameter above a predetermined value for a predetermined portion of each cycle of the primary load. 
         [0009]    In another construction, a power generating set includes an engine operable in response to a flow of fuel to produce a flow of exhaust gas, a generator coupled to the engine and operable in response to operation of the engine to produce a total electrical power, and a primary load electrically connected to the generator to receive a portion of the total electrical power, the primary load having a cyclical pattern. A battery bank is selectively connected to the generator to receive a portion of the total electrical power and an insulated-gate bipolar transistor (IGBT) is positioned to selectively transition between a connected state and a disconnected state. The battery bank is connected to the generator to charge the battery bank when the IGBT is in the connected state and is disconnected from the generator when the IGBT is in the disconnected state. 
         [0010]    In yet another construction, a power generating set includes a generator operable to produce electrical power, an engine operable in response to a flow of fuel to drive the generator and to produce a flow of exhaust gas having an exhaust gas temperature, and a particulate filter positioned to receive the flow of exhaust gas from the engine and to filter particulate matter from the exhaust gas. A primary load is electrically connected to the generator to draw a first portion of electrical power from the generator, the primary load having a cyclical pattern and a battery bank is selectively connected to the generator to selectively draw a second portion of electrical power. A switching element is operable to selectively transition between a connected state and a disconnected state, wherein the battery bank is connected to the generator when the switching element is in the connected state and is disconnected from the generator when the switching element is in the disconnected state. A controller is operable to vary the state of the switching element to maintain the sum of the first portion of electrical power and the second portion of electrical power above a predetermined value for a predetermined portion of each cycle of the primary load such that the heat from the flow of exhaust is sufficient to one of passively regenerate or actively regenerate the particulate filter. 
         [0011]    In still another construction, a power generating set includes a generator operable to produce a total electrical power, an engine operable in response to a flow of fuel to drive the generator and to produce a flow of exhaust gas having an exhaust gas temperature, a particulate filter positioned to receive the flow of exhaust gas from the engine and to filter particulate matter from the exhaust gas, and a primary load electrically connected to the generator to receive a first portion of the total electrical power that varies in a series of cycles between a maximum that is above a predetermined value and a minimum that is below a predetermined value. A battery bank is electrically connected to the generator to receive a second portion of the total electrical power, and a switching element is operable to selectively transition between a connected state and a disconnected state, wherein the battery bank is connected to the generator when the switching element is in the connected state and is disconnected from the generator when the switching element is in the disconnected state. A controller is operable to vary the state of the switching element to maintain the sum of the first portion of the total electrical power and the second portion of the total electric power above the predetermined value for a portion of each cycle, the portion of each cycle being sufficient to one of passively regenerate or actively regenerate the particulate filter. 
         [0012]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a schematic illustration of a diesel powered generator system; 
           [0014]      FIG. 2  is a flow chart illustrating a control scheme for the diesel powered generator system of  FIG. 1 ; 
           [0015]      FIG. 3  is a flow chart illustrating another control scheme for the diesel powered generator system of  FIG. 1 ; 
           [0016]      FIG. 4  is a graphical representation of a cyclic load and two possible auxiliary loads; 
           [0017]      FIG. 5  is a schematic illustration of another diesel powered generator system; and 
           [0018]      FIG. 6  is a graphical representation of the predetermined value for active regeneration versus ambient temperature. 
       
    
    
       [0019]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
       DETAILED DESCRIPTION 
       [0020]      FIG. 1  illustrates a system  10  that includes a diesel engine  15  that drives a generator  20 . In the illustrated construction, the generator  20  is a three-phase AC generator  20  that is rotated at a desired speed to provide a three-phase current at a desired voltage (e.g., 480 volts) and a desired frequency (e.g., 60 Hz). In other constructions, asynchronous generators, synchronous generators, single-phase AC and DC generators or any other type of generator is powered by the diesel engine  15 . 
         [0021]    The diesel engine  15  includes a fuel tank  25  and a particulate filter  30  positioned in an exhaust stream  35  of the diesel engine  15 . The fuel tank  25  contains a fuel supply that is directed to the engine  15  and combusted with a flow of air  40  to produce shaft power and the exhaust stream  35 . The exhaust stream  35  includes a quantity of particulate matter (sometimes referred to as soot) that is preferably filtered rather than being emitted into the atmosphere. The quantity of particulate matter emitted is a function of the operating temperature of the engine  15 , and in particular the exhaust temperature of the engine  15 , with higher operating temperatures significantly reducing the amount of soot produced by the engine  15 . The load on the engine  15 , the generator  20 , and the exhaust temperature of the engine  15  are closely related in this example and are used interchangeably herein. Thus, as described in this application, the diesel engine  15  is at a high temperature when operated at a high generator load and is at a low temperature when operated at a low load. 
         [0022]    The particulate filter  30  includes any type of commonly used in-flow particulate filters for use with diesel engines  15 . For example, the particulate filter  30  may include filters made using cordierite, silicon carbide, other ceramic fibers, or metal fibers that are arranged or woven to capture particles as the exhaust stream  35  flows through the filter. The particulate filter  30  may include a catalytic material that aids in the regeneration of the filter  30 . Preferably, the filter  30  is capable of both passive and active regeneration. 
         [0023]    Passive filter regeneration occurs when the load on the diesel engine  15  and therefore the exhaust temperature exceeds a temperature threshold  45 . Above this level, sufficient energy is present within the filter  30  to oxidize the soot and other particulate matter collected. The duration required above the temperature threshold  45  is a function of the quantity of soot captured in the filter  30 . Through extensive testing, it has been discovered that when powering a highly cyclic load such as the pump jack example described below, exceeding the threshold for between 10 percent and 30 percent of each cycle is sufficient to regenerate the filter  30  and remove the soot collected during the prior cycle. In a preferred condition, the temperature threshold  45  must be exceeded for only 20 percent of the total cycle. Thus, each cycle can regenerate the filter  30  and remove any soot collected during the prior cycle. 
         [0024]    Active regeneration occurs and must be used when the engine  15  is operated at a load or exhaust temperature that remains below a level where passive regeneration can occur. During active regeneration, fuel is passed to the particulate filter  30  to increase the available energy and therefore the temperature within the filter  30  to aid in the combustion of the soot particles. While some regeneration occurs when the load or exhaust temperature is above a predetermined level  50 , testing has shown that regeneration is not effective if performed below the predetermined level  50 . In fact, when powering a highly cyclic load such as the pump jack described below, testing has shown that the load or temperature must remain above the predetermined level  50  for all or substantially all (greater than 90 percent) of the operating cycle of the load applied to the engine  15  in order for active regeneration to be effective. 
         [0025]    In the construction of  FIG. 2 , the three phase power produced by the generator  20  is directed to a voltage selector switch  54  and then to a main circuit breaker  55  that can be manually controlled, automatically controlled, or both and is operable to separate the generator  20  from a total load  60  that is connected to an output side of the main breaker  55 . The voltage selector switch allows the user to select the output voltage of the generator  20 . 
         [0026]    As illustrated in  FIG. 1 , the total load  60  is divided into a main load  65  and an auxiliary load  70 . While the generator  20  is capable of driving virtually any electrical load, the invention is particularly advantageous when the main load  65  is highly cyclical. For example, generator systems of the type illustrated in  FIG. 1  are often used to provide electrical power to motor driven pump jacks. In these arrangements, the motor is often the sole load or virtually the sole load such that the main load  65  follows a cyclic pattern. 
         [0027]    As illustrated in  FIG. 1 , the auxiliary load  70  is applied to the generator  20  in parallel with the main load  65 . As illustrated in  FIGS. 2 and 3 , the auxiliary load  70  includes one or more switching elements  75  connected to an electrical load  80 . In the illustrated construction, the switching elements  75  include a single insulated-gate bipolar transistor (IGBT) that facilitates rapid switching to direct power to the electrical load  80  or to inhibit the flow of power to the electrical load  80 . In the illustrated construction, the electrical load  80  includes one or more resistors that can be switched on and off individually or in groups. Thus, the illustrated arrangement provides fine control of the size of the auxiliary load  70  and can provide rapid and smooth changes in that size as will be discussed in greater detail. 
         [0028]      FIG. 2  illustrates a three phase DC power supply  82  positioned between the main circuit breaker  55  and the switching elements  75 . In the preferred construction, the switching element is an IGBT  75  that operates using DC power. Thus, the power supply  82  operates to convert the three phase AC power produced by the generator  20  to a single phase DC supply usable by the IGBT  75 . In other constructions, AC switching elements may be employed, thereby eliminating the need for the DC power supply  82 . 
         [0029]    As noted above, the generator  20  produces a three phase output of electrical current at a desired voltage. An engine control system  85  operates to maintain the engine speed at the speed required to drive the generator  20  at the desired speed. In a direct drive arrangement, the diesel engine  15  rotates at the same speed as the generator  20 . In some arrangements, a transmission is positioned between the generator  20  and the engine  15  to either step up or step down the speed of the generator  20  with respect to the engine  15 . 
         [0030]    With reference to  FIG. 2 , a controller  90  is coupled to the IGBT  75  and is operable to control the state of the IGBT  75  to control the level of the auxiliary load  70 . The controller  90  adjusts the auxiliary load  70  via the IGBT  75  to maintain a level total load  60  on the generator  20  or to produce a peak load on the generator  20  as will be discussed with regard to  FIG. 4 . In a preferred construction, the controller  90  applies a pulse width modulation signal to the single IGBT  75  to turn it on for a predetermined portion of a period of time. When on, the full auxiliary load  80  is electrically connected to the generator  20 . By pulsing the IGBT  75  on and off, the controller  90  is able to precisely control the average power consumed during the period of time to provide very fine control of the size of the auxiliary load  80 . For example, if during a given time period (e.g., 1 second), a total resistive load  80  is applied via the IGBT  75  for half of the time period, the total resistive load applied to the generator  20  will effectively be half the load&#39;s actual size. 
         [0031]    In another construction, the IGBT  75  is replaced by a number of switching elements and the load  80  includes a plurality of individual loads each switchable via one of the switching elements. During operation, select switching elements are switched to connect a respective load to achieve a desired auxiliary load level. 
         [0032]    In the construction illustrated in  FIG. 2  the engine electronic control module (ECM)  85  senses the speed or the load of the engine  15  and controls a fuel throttle valve to adjust the speed or load of the engine  15  as is known in the art. In addition, the ECM  85  provides one or more inputs to the controller  90  for use in setting the auxiliary load level  70 . For example, in one construction the ECM  85  determines a total load on the engine  15  and sends a signal indicative of that load to the controller  90 . The controller  90  then adjusts the auxiliary load level  70  until the engine load is above a predetermined level. In other constructions, other parameters (e.g., exhaust temperature, engine temperature, fuel flow rate, exhaust pressure, inlet pressure, etc.) are used to control the auxiliary load level. For example, yet another construction measures the current and voltage of the generator output to determine the total electrical power generated. The auxiliary load level  70  is easily measured, thereby allowing for a direct calculation of the main load level. 
         [0033]    In addition, some parameters collected by the ECM  85  can be used to verify that the filter regeneration is effective. For example, one construction monitors the pressure drop across the filter  30  and adjusts the temperature, the time, the engine load, or other parameters of the operation in response to the measured pressure. In one arrangement, if the pressure drop exceeds a predetermined threshold, the time above the temperature threshold  45  is increased during passive regeneration and/or the predetermined level  50  for active regeneration is increased until the pressure drop returns to normal. 
         [0034]      FIG. 3  illustrates another system that is similar to the system of  FIG. 2  but includes a current sensor  95 . The current sensor  95  does not replace the ECM  85  of  FIG. 2  but rather is used to collect data that is then delivered to the controller  90  to control the IGBT  75 . In the arrangement of  FIG. 3 , the current sensor  95  senses the level of power flowing to the main load  65  and feeds that information to the controller  90 . The controller  90  then adjusts the pulse width to the IGBT  75  as required to achieve the desired level of total power  60  consumed. In still another construction, a temperature probe is placed in the engine exhaust flow  35  to measure the exhaust gas temperature. The temperature signal is then delivered to the controller  90  and the IGBT  75  is adjusted to raise or lower the auxiliary load  70  and the temperature as desired. 
         [0035]    With reference to  FIG. 4 , the operation of the diesel driven generator system  10  for use in powering a highly cyclic load, in this example a pump jack, will be described.  FIG. 4  is a graph of percent engine/generator load or percent exhaust temperature (with 0% being room temperature and 100% being the maximum exhaust temperature) versus time. The vertical broken lines identify the start  100  of and the end  105  of one pump jack cycle. A first horizontal broken line marks the lower threshold for passive regeneration  45  and a second horizontal line indicates the predetermined value for active regeneration  50 . 
         [0036]    As illustrated in  FIG. 4 , pump jacks rotate through a cycle that includes a first portion that requires a large power input followed by a second portion during which little or no power is required. During this first portion of the cycle, the motor is heavily loaded and thus draws a significant load from the generator  20 . However, during the second portion of the cycle, very little electrical current is required. Thus, the pump jack consumes an average amount of power during its cycle. The motor and generator  20  powering these pump jacks are often sized to deliver significantly more than the average power level to assure that the components are capable of providing the power required in the first portion of the cycle. Because the pump jack is virtually the entire load on the generator  20 , the diesel engine power output follows the pump jack curve and moves through a cycle with a short-time high-load peak followed by a low-load portion where the diesel engine  15  virtually coasts. 
         [0037]    As can be seen, the pump jack cycle includes a short spike (about  20  percent of the cycle) that exceeds the predetermined level  50  for active regeneration but falls short of the threshold value  45  for passive regeneration. The load then drops below the predetermined level  50  for the remainder of the cycle. As discussed above, this cycle does not allow for passive regeneration, nor does it allow for effective active regeneration. 
         [0038]    The controller  90  can be programmed to achieve either passive regeneration, active regeneration or both using the auxiliary load  70 . To achieve passive generation, the controller  90  signals the IGBT  75  to add auxiliary load  70  during the peak load of the cycle. The added load, indicated by the first cross-hatched region  110  of  FIG. 4  assures that the total load  60  on the diesel engine  15  exceeds the threshold level  45  for the necessary time or portion of the cycle to achieve passive regeneration. The auxiliary load  70  is then smoothly switched off and the total load  60  is allowed to drop to the lower level. 
         [0039]    To achieve active regeneration, the controller  90  monitors the total load  60  on the generator  20  or the engine  15  and signals the IGBT  75  to add auxiliary load  70 , shown as the second cross-hatched region  115 , where needed to assure that the minimum total load  60  always remains above the predetermined level  50 . The engine operation is also modified to assure that some fuel passes to the particulate filter  30  as is required for active regeneration. 
         [0040]    In some constructions, the controller  90  uses both active and passive regeneration by adding load as necessary and as described with regard to the individual modes of regeneration. In addition, the engine control module can be used to determine when and how frequently regeneration must occur as well as which type of regeneration to perform if desired. 
         [0041]      FIG. 6  graphically illustrates how ambient temperature can effect regeneration and specifically the value or percent load of the predetermined value  50  for active regeneration. Typically, filter manufacturers recommend operation above a predetermined value  50  for active regeneration that is based on the lowest possible ambient temperature. However, in warmer ambient conditions, this can be a significant and excessive load on the engine  15 . Thus, some constructions will vary the predetermined value  50  for active regeneration as illustrated in  FIG. 6  based on a measured ambient temperature. 
         [0042]    It should be noted that other types of loads  80  as well as other switching elements  75  could be employed if desired. For example, batteries could be used in place of resistors to provide a load. 
         [0043]      FIG. 5  illustrates an alternative construction  117  in which the large generator  20  is replaced by the load which is mechanically driven by the diesel engine  15 . For example, the load may be the transmission or drive system of a vehicle. A smaller generator  120  is simultaneously driven by the diesel engine  15 , via a belt, gear, chain, or other interconnecting arrangement to provide an electrical current to an auxiliary load  70  that is similar to that described above. The auxiliary load  70  is switched in and out as described with regard to  FIG. 4  to achieve the desired regeneration. 
         [0044]    As discussed above, the auxiliary load  70  is used to increase the total load  60  on the engine  15  as required to achieve either passive or active regeneration. Regeneration is largely a function of the temperature of the exhaust gas  35  entering the filter  30 . Thus, while the invention controls engine load and may measure various different engine or system parameters, those parameters are related to the engine exhaust temperature. In one construction, the performance of the system is further enhanced by placing the resistive load  80  directly in the exhaust flow stream  35  or adjacent the exhaust flow stream  35  to allow the heat produced by the resistors  80  to directly or indirectly heat the exhaust flow  35 , thereby reducing the amount of auxiliary load  70  required to reach the predetermined level  50  or the temperature threshold  45 . 
         [0045]    Various features and advantages of the invention are set forth in the following claims.