Patent Publication Number: US-2007119146-A1

Title: Retarding and filter cleaning method and system

Description:
TECHNICAL FIELD  
      The present disclosure relates generally to a retarding and filter cleaning method and system and, more particularly, to a work machine having a gas turbine engine and employing a retarding and filter cleaning method and system.  
     BACKGROUND  
      Work machines such as, for example, on-highway and off-road haulage vehicles, wheeled tractors, track type tractors, and various construction work machines, may receive motive power from any one of a number of different types of engines. For example, a work machine may be powered by a gasoline engine, a diesel engine, or a gas turbine engine. Work machines powered by a gas turbine engine may use the gas turbine engine to drive a mechanism that may be used to transfer the engine power output into work machine propulsion or other work machine operations.  
      Work machines may require various retarders to aid braking. When descending slopes, for example, work machines may use retarding systems in order to dissipate kinetic energy so as to maintain a safe speed. For example, heavy work machines may use the momentum of the machine when moving down a slope to drive the engine. The engine, in the case of a piston engine such as, for example, a diesel engine, then operates as a compressor, dissipates kinetic energy, and retards the motion of the work machine.  
      Work machines may operate in environments characterized by dirt particles, dust, mud, rock particles, and other substances that may be detrimental to engine operation. The nature of a gas turbine engine dictates that it uses a large quantity of air. For example, a gas turbine engine may require as much as four time the air flow of a diesel engine comparable in power. Suitable filtering structure may be provided for precluding contaminants from reaching and damaging the engine. For example, in a work machine powered by a gas turbine engine, the intake air flow for the engine may be provided with one or more filters to ensure that the rather large flow of air directed to the gas turbine engine is reasonably free from contaminants that may harm the engine components.  
      Because of the rather large flow of air required by a gas turbine engine, and because the engine may operate in dusty, dirty conditions, air filters for gas turbine engines may require frequent cleaning or replacement. Frequent cleaning or replacement may require frequent down-time periods for the gas turbine engine and for the work machine.  
      It would be useful to provide a system, structure, and method whereby air filters for a gas turbine engine may be efficiently and effectively cleaned. Additionally, it would be useful if provision could be made for cleaning air filters for a gas turbine engine with only limited compromising of space constraints. Moreover, it would be particularly helpful if cleaning of the air filters could be accomplished effectively as a by-product of another work machine operation, such as work machine retarding, without experiencing work machine down time.  
      One method of cleaning an air filter for a gas turbine engine is described in U.S. Pat. No. 5,401,285 (the &#39;285 patent) issued to Gillingham, et al. on Mar. 28, 1995. The &#39;285 patent describes an air filter system that may be used in the gas turbine engine powered M1 tank. The &#39;285 patent provides a pulse jet arrangement to direct air backward through the filter to regenerate it periodically between times of filter replacement. A compressed air tank is provided as a supply of compressed air for the pulse jets. The compressed air tank is supplied with compressed air by a bleed conduit from the turbine.  
      Although the method described in the &#39;285 patent may recognize the need for frequent cleaning of air filters for a gas turbine engine, the &#39;285 patent employs a separate system to do so. Rather than using an existing operation to directly facilitate filter cleaning, the &#39;285 patent requires a system of compressed air tanks and “pulse jets,” as well as the space necessary for these components. Moreover, there is no recognition in the &#39;285 patent that filter cleaning may be accomplished in association with a retarding function.  
      The disclosed retarding and filter cleaning method is directed to overcoming one or more of the problems outlined above with respect to existing technology.  
     SUMMARY OF THE INVENTION  
      In one aspect, the present disclosure includes a filter cleaning system for a gas turbine engine. The gas turbine engine includes a compressor section and a combustor section. A mechanism is operatively connected to the gas turbine engine and is configured to be driven by the gas turbine engine in a first mode and configured to drive the gas turbine engine in a second mode. A first flow path is provided for delivering air to the compressor section. At least one air filter is in the first flow path for filtering the air to be delivered to the compressor section. A second flow path is provided for delivering compressed air from the compressor section to the combustor section during the first mode. A third flow path is provided for delivering compressed air from the compressor section to the at least one air filter during the second mode.  
      In another aspect, the present disclosure includes a method of cleaning a filter for a gas turbine engine. In a first mode, a gas turbine engine including a compressor section and a combustor section drives a mechanism. Air is passed through at least one air filter and delivered to the compressor section. During the first mode, compressed air from the compressor section is delivered to the combustor section. During a second mode, the compressor section is driven by the mechanism. During the second mode, compressed air from the compressor section is delivered to clean the at least one air filter.  
      It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a highly diagrammatic and schematic illustration of an embodiment of a work machine powered by a gas turbine engine and having a filtering system;  
       FIG. 2  is a diagram of an embodiment of a gas turbine engine and filtering system shown in a mode for cleaning a first filter; and  
       FIG. 3  is a diagram similar to  FIG. 2  and showing an embodiment of a gas turbine engine and filtering system in a mode for cleaning a second filter. 
    
    
     DETAILED DESCRIPTION  
       FIG. 1  diagrammatically illustrates an exemplary work machine  10 . Work machine  10  includes a chassis (generally designated by the rectangular outline) and may be, for example, a track-type tractor, a track-type loader, a hydraulic excavator, a mining truck, a wheel loader, an off-road haulage vehicle, an on-highway truck, or another work machine known to those skilled in the art. The particular type of work machine involved is generally incidental to the system disclosed. Those having skill in the art will readily be able to apply the disclosed system and method to various types of work machines once apprised of the embodiments disclosed herein. Work machine  10  may include a gas turbine engine  12  as its prime mover. Gas turbine engine  12  may include a compressor section  14  configured to draw in a relatively large amount of intake air during operation and configured to compress the air drawn in. Gas turbine engine  12  may also include a combustor section  16  and a turbine section  18 .  
      Work machine  10  may include an air flow system generally indicated at  20 . Air flow system  20  may include various conduits and valves, the arrangement and purpose of which will be explained in due course. Air flow system  20  may also include one or more air filters  22 ,  24  configured to substantially reduce the amount of dust, dirt particles, rocks, and various other contaminants drawn into gas turbine engine  12 . It will be understood that the work machine may include only a single air filter, or it may include a plurality of air filters. To illustrate the disclosed system and method with reasonable simplicity, two filters are shown in  FIGS. 1-3 .  
      Gas turbine engine  12  may include a recuperator  26  configured to heat compressed air received from compressor section  14 . The recuperator  26  may derive heat from turbine section  18  exhaust as the exhaust passes through the recuperator  26  on its way to the atmosphere. Combustor section  16  may be configured to receive heated, compressed air from the recuperator  26 . The combustor section  16  may be provided with fuel from, for example, a fuel injection device schematically shown at  28 . Ignition and burning of the heated, compressed air and fuel creates an exhaust gas with high energy. Turbine section  18  of gas turbine engine  12  is configured to convert energy from the exhaust gas into mechanical energy when the exhaust gas passes through turbine section  18 . Turbine section  18  is operably coupled to a power shaft  30  configured to be rotated by turbine section  18 .  
      Work machine  10  may further include a mechanism  32  operably coupled to power shaft  30 . A drive connection, such as shaft  36  between compressor section  14  and mechanism  32 , for example, may couple power shaft  30  to mechanism  32 . Mechanism  32  is diagrammatically shown in  FIGS. 1-3  since the particular mechanism to be driven by gas turbine engine  12  may vary with the type of work machine and with the type of drive system employed on a given type of work machine. Mechanism  32  may be mechanical, hydraulic, electrical, or any other mechanism useful to convert the output of gas turbine engine  12  to propulsion for a work machine.  
      Mechanism  32  may be, for example, the lower power train of a work machine, including gearing mechanically coupled to wheels (not shown) and/or ground engaging tracks (not shown). Mechanism  32  may alternatively be a generator configured to convert mechanical energy developed by gas turbine engine  12  into electric energy for use as a power source to power, for example, one or more electric motors, such as electric motor  34 , shown in  FIG. 1 , configured to propel work machine  10 . Mechanism  32  may be configured to deliver power back to and drive gas turbine engine  12  to retard work machine  10  when work machine  10  is descending a slope, for example.  
      The various conduits and valves of air intake system  20  are illustrated in  FIGS. 1-3 . The illustrated valving is designed to permit flow or air between filters  22 ,  24  and compressor section  14  in opposite directions. It will be understood that the simplified arrangement of conduits and valves shown in  FIGS. 1-3  is for purposes of illustration only. It will be apparent to those having skill in the art that, once the disclosed embodiment has been revealed, other suitable expedients for permitting the flow of air in opposite directions, in the manner to be shortly explained, will become apparent.  
      A conduit  38  may enable the flow of air between air filter  22  and compressor section  14  while a conduit  40  may extend between air filter  24  and a suitable connection to conduit  38  to enable the flow of air from air filter  24  to compressor section  14 . Valve  42  may be positioned in conduit  38  between air filter  22  and the location where conduit  40  connects to conduit  38 . Valve  44  may be positioned in conduit  40 . Valves  42  and  44  may be selectively controlled to permit the flow of air from a respective air filter  22 ,  24  in a first position of the valve, or to preclude the flow of air from a respective air filter  22 ,  24  in a second position of the valve.  
      A conduit  46  may enable the flow of compressed air from compressor section  14  into recuperator  26 . Valve  48  may be mounted in conduit  46 . Conduit  50  may extend between valve  48  and air filter  22  and enable flow of air from compressor section  14  to air filter  22 . Conduit  52  may extend from conduit  50  to air filter  24  and enable flow of compressed air from compressor section  14  to air filter  24 . Valve  54  may be situated in conduit  50  at a location between valve  48  and air filter  22 . Conduit  52  may connect to conduit  50  at a location between valve  54  and valve  48 . Valve  56  may be situated in conduit  52 .  
      Valve  48  may be selectively controlled to permit the flow of compressed air along conduit  46  to recuperator  26 , while precluding the flow of compressed air into conduit  50  or conduit  52 . Valve  48  may also be selectively controlled to permit the flow of compressed air into conduit  50  while precluding the flow of compressed air into recuperator  26 . Valves  54  and  56  may be selectively controlled to permit the flow of compressed air from compressor section  14  to a respective air filter  22 ,  24  in a first position of the valve, or to preclude the flow of compressed air from compressor section  14  to a respective air filter  22 ,  24  in a second position of the valve.  
      Air flow system  20  may be characterized as embodying different flow paths. For example, conduits  38  and  40 , leading from air filters  22 ,  24  to compressor section  14  may be characterized as a first flow path  58  for delivering filtered air to compressor section  14 . Conduit  46  may be characterized as a second flow path  60  for delivering compressed air from compressor section  14  to combustor  14 .  FIGS. 1-3  diagrammatically show the connection of conduit  46  to recuperator  26  and the flow line in recuperator  26  ultimately leading to combustor section  16 . Conduit  50  leading from valve  48  to air filter  22  along with conduit  52  and the portion of conduit  46  between compressor section  14  and valve  48  may be characterized as a third flow path  62 .  
      It will be apparent that second flow path  60  is at least partly coextensive with third flow path  62 . It will also be apparent that first flow path  58  includes two branches, one of which, in the exemplary embodiment, is conduit  40  leading from air filter  24 , and the other of which is the portion of conduit  38  leading from air filter  22  up to the location where conduit  40  connects to conduit  38 . Further, it will be apparent that third flow path  62  includes two branches, one of which, in the exemplary embodiment, is conduit  52  leading to air filter  24 , and the other of which is the portion of conduit  50  leading from the location where conduit  52  connects to conduit  50  up to air filter  22 .  
     INDUSTRIAL APPLICABILITY  
      In the exemplary work machine  10  schematically depicted in  FIG. 1 , gas turbine engine  12  provides mechanical power for work machine  10 . Compressor section  14  draws in and compresses a relatively large amount of intake air, which may be filtered by one or more air filters  22 ,  24  to substantially prevent dust, dirt particles, rocks, and other contaminants from being drawn into compressor section  14 .  
      Once compressed in compressor section  14 , compressed air enters recuperator  26 , where the compressed air may be heated by hot gases exhausted from turbine section  18 . Following heating, the compressed air may be fed into combustor section  16 , which may receive fuel from fuel injection device  28 . Combustor section  16  ignites the compressed air and fuel, thereby creating a heated, high energy exhaust gas.  
      The heated exhaust gas may be passed through turbine section  18 , which converts energy in the heated exhaust gas into mechanical energy as the heated exhaust gases pass through turbine section  18 . Once it passes through turbine section  18 , the exhaust gas may be fed into recuperator  26  to heat compressed air entering recuperator  26  from compressor section  14 . The exhaust gases may thereafter be exhausted to the atmosphere.  
      Turbine section  18  may be operably coupled to power shaft  30 , for example, via direct connection, such that when turbine section  18  rotates in response to the flow of the heated exhaust gas, power shaft  30  is also rotated. Power shaft  30  is operably coupled to compressor section  14  so that compressor section  14  may continue to compress air drawn in through, for example, air filter  22  and/or air filter  24 . In addition to being operably coupled to compressor section  14 , power shaft  30  may be operably coupled to mechanism  32  through, for example, shaft  36 .  
      Mechanism  32  converts the energy output of gas turbine engine  12  into propulsion for work machine  10 . In the embodiment of  FIG. 1 , for example, mechanism  32  may be a generator which converts mechanical energy developed by gas turbine engine  12  into electric energy for use as a power source to power, for example, one or more electric motors  34  configured to propel work machine  10 , for example, via ground engaging members such as wheels and/or a pair of ground engaging tracks. The mode of operation in which compressor section  14  delivers compressed air to combustor section  16  and in which gas turbine engine  12  drives mechanism  32  may conveniently be referred to as a first mode of operation.  
      Work machine  10  may be provided with a retarding system to supplement a braking system. For example, during downhill motion of the work machine, energy from the work machine is directed back through mechanism  32  to drive the gas turbine engine. For example, referring to  FIG. 1 , the one or more electric motors  34  may, during downhill motion of the work machine, be configured to act as generators providing electric current to the generator  32  which, in turn, may be configured to act as a motor. Thus, generator  32  may be converted to a “motoring” mode in which it may drive compressor section  14  of gas turbine engine  12 . This mode of operation wherein the gas turbine engine is driven by way of mechanism  32  may conveniently be referred to as a second mode of operation. During this second mode of operation, fuel injection device  28  may be substantially inhibited from supplying fuel to combustor  16 . In this way, instead of being driven by turbine section  18  and combustor section  16 , compressor section  14  of gas turbine engine  12  is driven by the mechanism  32 .  
      The second mode of operation is illustrated in  FIGS. 2 and 3 . During this second mode of operation, the work machine motion is being retarded since energy of work machine motion is being dissipated through the driving of compressor section  14  and connected turbine section  18 . At this time, valve  48  may be positioned to preclude the flow of compressed air along flow path  60  to combustor section  16  and to direct compressed air exiting compressor section  14  along flow path  62 . At the same time, one of valves  54  and  56  is open to permit the flow of compressed air while the other of valves  54  and  56  is closed to preclude the flow of compressed air. Also at the same time, one of valves  42  and  44  is open to permit the flow of filtered air to compressor section  14  along flow path  58  while the other of valves  42  and  44  is closed to preclude the flow of filtered air to compressor section  14 .  
      Filtered air may be supplied to compressor section  14  and compressed air may be delivered to at least one of the filters to clean the filter during the second, retarding mode. In order to permit both flow of filtered air to compressor section  14  and flow of compressed air to at least one of the air filters  22 ,  24 , valves  42 ,  44 ,  54 , and  56  may be coordinated in operation.  FIG. 2  is an embodiment illustrating the situation where air filter  24  is being cleaned during the retarding mode while filtered air is being provided to compressor section  14  by way of air filter  22 . In this situation, valve  56  is in an open position while valve  54  is closed. In a similar manner, valve  42  is in an open position while valve  44  is closed.  FIG. 3  is an embodiment illustrating the situation where air filter  22  is being cleaned during the second, retarding mode while filtered air is being provided to compressor section  14  by way of air filter  24 . In this situation, valve  54  is in an open position while valve  56  is closed. In a similar manner, valve  44  is in an open position while valve  42  is closed.  
      It can readily be seen that the disclosed embodiments provide for the more frequent cleaning of air filters that may be necessary with the use of a gas turbine engine, particularly during operation in an environment that produces substantial dust, dirt, and other contaminants that may be harmful to the engine. Instead of an entirely separate system for cleaning the filters, such as filters  22 ,  24 , advantage is taken of an engine and work machine retarding function. Where the engine is not used to drive the mechanism  32  and provide power to the work machine, the work machine may be permitted to dissipate energy through driving mechanism  32 . Where mechanism  32  is a generator, “motoring” the generator may drive the compressor section  14  of gas turbine engine  12  and simultaneously clean one or more of air filters  22 ,  24  with the compressed air output from compressor section  14 .  
      For purposes of illustration, a particular arrangement of conduits and valves has been shown and described to diagrammatically depict the system and method disclosed. However, it will be understood by those skilled in the art that various arrangements of conduits and valves may be employed to create flow paths for delivering filtered air to the compressor section, for delivering compressed air to the combustor section, and for delivering compressed air to clean the air filters. The disclosure is not to be limited by the particular embodiments diagrammatically illustrated and described herein.  
      It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed turbine retarding and filter cleaning method and system. For example, while the system has been disclosed primarily in connection with retarding the motion of a work machine, it will be apparent that the method and system could be employed in a stationary system wherein a gas turbine engine drives a generator which in turn provides electric power. In such a situation, suitable circuitry could be provided by those skilled in the art for periodically driving the generator to drive the compressor section and enable filter cleaning. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed method and system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.