HYDRAULIC ASSIST TURBOCHARGER SYSTEM

Abstract: A turbocharger system for supplying charge air to a combustion engine includes a non-ventilated hydraulic turbine mounted directly on the turbocharger shaft, and an auxiliary combustor mounted in-line between the engine and the turbocharger. The non-ventilated hydraulic tur­ bine is selectively driven by a high pressure hydraulic fluid to drive the turbocharger for supplying air to the auxiliary combustor, which in turn supplementally drives the turbo­ charger throughout a broad range of engine operation to provide additional air flow to the engine when required.

Description: HYDRAULIC ASSIST TURBOCHARGER SYSTEM This invention relates to turbocharger systems for supplying charge air to a combustion engine comprising a turbocharger including a turbine driven by engine exhaust gases and driving a compressor. Such systems are highly advantageous in that relatively dense air is supplied to the engine but under some conditions of engine operation, for example at low speed and full load or during low speed acceleration, the exhaust gases do not have enough energy to provide sufficient charge air Many proposals are known for boosting or supplementing the normal charge air output. The present Applicant's co-pending European Application 80302380.3 (Case 300) describes a number of arrangements in which the shaft of the exhaust-driven turbine and the compressor also carries a non-ventilated hydraulic turbine wheel to which high pressure liquid is supplied under certain conditions of operation An object of the present invention is to provide a further arrangement that may be advantageous under other conditions, for example when starting the engine, at which time it will be appreciated that no exhaust gases are available. According to one aspect of the present invention a turbocharger system for supplying charge air to a combustion engine comprises a turbocharger including a turbine driven by engine exhaust gases, a hydraulic turbine, a compressor driven alternatively by the exhaust gas turbine and/or the hydraulic turbine to supply charge air to the engine, a combuster in the conduit between the engine exhaust and the exhaust gas turbine, means for supplying high pressure liquid to the hydraulic turbine to drive the compressor to provide a supply of charge air, means for by-passing at least someof the said charge air to flow through the combuster and exhaust gas turbine (without passing through the engine), and means for supplying fuel to the combuster under certain engine operating conditions (e.g. before starting). As in the specification referred to above the hydraulic turbine is preferably non-ventilated to prevent frothing or foaming of the liquid at the high speeds that may be reached, for example of the order of 100,000 r.p.m. or more. Conveniently the engine has a hydraulic system including means for supplying hydraulic fluid to the turbocharger for lubrication, and the liquid employed for driving the hydraulic turbine comprises a portion of the liquid in the said hydraulic system. Thus the system may include a low pressure pump supplying liquid for lubrication and a high pressure pump for supplying liquid to drive the hydraulic turbine. Preferably the means for by-passing charge air is controlled in response to engine operating conditions. In particular it may by-pass charge air prior to starting of the engine but close such supply when the turbocharger reaches self-sustaining operation. Similarly the means for supplying fuel to the combuster may be dependent upon engine operating conditions. For example the means for supplying fuel to the combuster may be arranged to do so generally in inverse proportion to engine speed. In one form of the invention the by-pass conduit is controlled by a valve responsive to engine operating conditions to close for at least some conditions of engine operation. In another form of the invention the turbocharger is sized to provide charge air flow generally matching engine air flow consumption requirments at relatively high speed engine operation whereby the charge air for by-passing through the by-pass means is unavailable due to engine consumption when the engine is operated at relatively high speed, a check valve being provided for preventing the flow of exhaust gases through it. According to another aspect of the invention, a method of operating a turbocharger system including a turbocharger for supplying charge air to a combustion engine comprising a turbocharger including a turbine driven by engine exhaust gases, a hydraulic turbine, and a compressor driven alternatively by the exhaust gas turbine and/or the hydraulic turbine to supply charge air to the engine, and a hydraulic system including means for supplying liquid at relatively low pressure to the turbocharger for lubrication thereof, includes supplying a portion of the liquid at a relatively high pressure from the hydraulic system to the hydraulic turbine prior to starting of the engine to drive the compressor and provide a charge air output supplying at least part of the said charge air output to a combuster interposed between the engine exhaust and the exhaust driven turbine, supplying fuel to the combuster to produce combustion with the charge air to provide high energy exhaust gases, supplying the said gases to the exhaust gas turbine for accelerating it to self sustaining operation, and starting the engine. The method may include by-passing a portion of the charge air flow around the engine to the combuster at relatively low-speed engine operating conditions to supplement the energy level of gases flowing through the combuster. Further features and details of the inventin will be apparent from the following description of one specific embodiment, given by way of example, with reference to the accompanying drawings, in which:- the single figure is a schemtic diagram of a turbocharger system embodying the invention. The hydraulic assist turbocharger system 10 shown in the drawing is basically similar to those described in co-pending European Application No 80302380.3 (filed 15th JULY0, 1980 and published 21st JANUARY, 1981 under PUB.NO. 022678A1) and like parts bear corresponding reference numerals. It comprises a turbocharger 12 for supplying relatively high density charge air to a combustion engine 14, such as a two-cycle or a four-cycle internal combustion engine. More specifically, the turbocharger 12 includes a turbine wheel 15 and a compressor wheel 18 respectively received within turbine and compressor housings 20 and 22. The turbine and compressor housing 20 and 22 are interconnected by a centre housing 24 including bearings 26 such as suitable journal and thrust bearings for rotatably supporting a shaft 28 to which the turbine wheel 16 and the compressor wheel 18 are commonly connected. The turbocharger turbine wheel 16 is rotatably driven by exhaust gases from the engine 14 which are supplied to the turbine wheel via an exhaust manifold 29 and an exhaust conduit 30. If desired, the turbocharger turbine housing 20 and the exhaust manifold 29 and conduit 30 may be adapted for divided, pulse-type operation such as that shown and described in U.S. Patent No. 3,294,364. The rotating turbine wheel 16 rotatably drives the shaft 28 and the compressor wheel 18 whereby the compressor wheel 18 draws in and compresses ambient air. This compressed ambient air comprises charge or boost air for the engine 14, and is supplied to the intake manifold 32 of the engine via a charge air conduit 34. Conveniently, as shown, a charge air coler heat exchanger 36 may be provided along the conduit 34 to cool the compressed charge air so as to reduce the total heat load of the engine and to further densify the charge air. The relatively high density charge air thus supplied to the engine 14 enables the engine to operate at a relatively high performance and efficiency level. The engine 14 includes an hydraulic fluid system 38 which is coupled to provide shared hydraulic fluid to the turbocharger for lubrication of the turbocharger bearings 26. In a preferred embodiment of the invention, the engine hydraulic fluid system 38 comprises an engine oil system, although other types of engine-driven hydraulic system for other purposes are contemplated. As embodied in an engine oil system as shown in the drawing, the hydraulic system 38 includes a reservoir 40 of hydraulic fluid or oil within the engine, and a relatively conventional low pressure oil pump 42 for pumping oil from the reservoir 40 to the engine 14 and the turbocharger 12. More specifically, the oil is pumped through an oil filter 44 and an oil cooler 46, and further to engine components requiring lubrication as indicated by conduit 48. The oil is also coupled through a supply conduit 50 to the centre housing 24 of the turbocharger 12 for supply to the turbocharger bearings 26 via a network of internal passages (not shown) formed in the centre housing. The oil passes through the bearings 26, typically as by a gravity drain system and is returned to the engine oil reservoir 40 as by a return conduit 54. Accordingly, the bearings 26 of the turbocharger 12 share the hydraulic system 38 with the engine 14 to assure that the turbocharger bearings 26 are properly lubricated at all times. As described in European Patent Application No 80.3023803, the turbocharger system 10 includes a non-ventilated hydraulic turbine 56 for supplementally driving the turbocharger compressor wheel 18 during certain modes of engine operation. Thus during some conditions of engine operation, the engine exhaust gases are incapable of rotatably driving the turbine wheel 16 at a speed sufficient to drive the compressor wheel 18 to supply the engine 14 with sufficient charge air. For example, such engine operating conditions may include relatively low speed, full load conditions wherein the available energy in the exhaust gases is relatively low or relatively low speed acceleration conditions wherein there is insufficient excess charge air available to accommodate rapid transient operating conditions. To assure that the compressor wheel is sufficiently driven to supply the engine with sufficient quantities of charge air, the turbocharger system includes the non-ventilated hydraulic turbine 56 for selectively and controllably supplementally driving the compressor wheel 18. The non-ventilated hydraulic turbine 56 is mounted within the centre housing 24 directly upon the turbocharger shaft 28 between the sets of bearings 26 rotatably supporting the shaft. The non- ventilated hydraulic turbine 56 is hydraulically driven by high pressure fluid or oil shared from the engine hydraulic system 38. That is, the hydraulic system 38 includes a high pressure pump 58 which may be suitably driven to provide a source of high pressure fluid. The high pressure pump 58 has its inlet communicating directly with the oil reservoir 40 of the engine hydraulic fluid system 38, and is suitably driven as by electrical means (not shown) or the like for pumping oil at a relatively high pressure through a high pressure supply conduit 60 to a control valve 262. The control valve 262 is suitably operated to couple the high pressure oil flow to the non-ventilated hydraulic turbine 56 via a line 64, or alternatively, to return the output of the high pressure pump 58 to the engine hydraulic system 38 via the bearing supply conduit 50 tosubstantially unload the pump 58. As shown, the output of the high pressure pump 58 is returned to the hydraulic system 38 by means of a by-pass return conduit 66 coupled to the bearing supply conduit 50. A one-way relief valve (not shown) may be connected between the high pressure supply conduit 60 and the bearing supply conduit 50 to prevent excessive system oil pressures. The control valve 262 is controlled in response to operating parameters of the turbocharger system 10 to control the operation of the hydraulic turbine 56. One control scheme for the control valve 62 comprises connection of the valve 262 with the output or discharge pressure of the turbocharger compressor wheel 18 by means (not shown) . When compressor discharge pressure is at or above a predetermined minimum threshold, the control valve 262 responds to the pressure to return the output of the high pressure pump 58 to the hydraulic system via the by-pass return conduit 66. In this event, sufficient oil back pressure corresponding with the discharge pressure of the low pressure pump 42 is available in the turbocharger bearing supply conduit 50 to maintain a relatively small oil flow, say on the order of about one gallon per minute, to the turbocharger bearings 26 for lubrication purposes. This bearing lubricating oil circulates through the centre housing 24 in communication with the bearings 26 and then returns to the engine oil system 38 via the main return conduit 54. When compressor discharge pressure falls below the predetermined threshold value, the control valve 262, automatically in response to the pressure, shifts position to couple directly the output of the high pressure pump 58 to the non-ventilated hydraulic turbine 56. That is, high pressure oil is fed into the high pressure supply line 64 which couples the oil to the centre housing 24 for driving supply to the non-ventilated hydraulic turbine 56. The high pressure oil rapidly accelerates the non-ventilated hydraulic turbine 56 correspondingly to accelerate rapidly the turbocharger shaft 28. In this manner, the compressor wheel 18 is rapidly accelerated to increase subsantially the pressure level of the compressor discharge charge air. This effectively provides the engine 14 with additional or supplemental charge air to maintain the engine 14 in a high power load carrying state in spite of the inability of the engine exhaust gases to drive adequately the turbocharger turbine wheel 16. The high pressure oil is circulated through the non-ventilated hydraulic turbine 56 at a relatively high flow rate and pressure, say on the order of up to about twelve gallons per minute and up to about 1600 p.s.i. This high pressure oil is separated within the centre housing 24 from direct communication with air to prevent foaming. The high pressure oil is also maintained separate from the bearing circulation path to prevent flooding of the bearings 26, and to allow the high pressure oil to flow into communication with the hydraulic turbine 56 at a relatively high flow rate. The oil drains from the non-ventilated hydraulic turbine 56 through a one-way check valve 70 and a drain conduit 72 to the turbocharger bearing supply conduit 50. With this configuration, the oil flow returning to the engine hydraulic system 38 via the conduit 50 is maintained at a sufficient back pressure to assure a relatively small flow through the bearing oil supply network within the centre housing 24 to maintain bearing lubrication. Of course, the check valve 70 prevents bearing supply flow from communicating with the non-ventilated hydraulic turbine 56 when the turbine 56 is not supplementally driven by high pressure oil. The construction of the turbocharger centre housing 24 and the mounting of the non-ventilated hydraulic turbine 56 therein are shown in detail in FIGURES 2-8 of Application No 80302380.3. As another embodiment of the invention in that application is shown in FIGURE 9. Those figures and disclosures can be deemed to be a part of this specification. In accordance with the present invention, an auxiliary combuster 181 is included in the exhaust conduit 30 and the control valve 262 is controlled for supplying high pressure oil to the non-ventilated hydraulic turbine 56 whenever it is desired to start the combustion engine 14. That is, for starting of the engine 14, the control valve 262 couples the high pressure oil to the hydraulic turbine 56 to initiate rotation of the turbine 56, and the turbocharger turbine wheel 16 and compressor wheel 18. If desired, the control valve 262 may include means for simultaneously initiating operation of the high pressure pump 58. Alternatively high pressure oil for starting purposes may be obtained from a high pressure oil accumulator. The hydraulically driven turbocharger 12 supplies compressed air, or charge air, from the compressor wheel 18 to the charge air conduit 34 for supply of charge air to the intake manifold 32 of the engine 14. However, prior to starting of the engine 14, flow of the charge air through the engine for combustion purposes is not possible. In this pre-starting condition, the charge air is supplied through a bypass conduit 180 directly to the engine exhaust conduit 30 upstream of the turbocharger turbine wheel 16 and the auxiliary combustor 181. The auxiliary combustor 181 is supplied with fuel from a fuel supply 182 through a scheduling fuel control 183 via a fuel line 184. The fuel and the by-pass charge air are ignited within the combustor 181 by suitable ignition means (not shown) to yield a substantial and continuous combustor flame for supplying substantial high energy exhaust gases for rotatably driving the turbine wheel 16 of the turbocharger 12. The specific construction details of the combustor 181 and fuel injector means therefor, and the fuel control 183 are not described in detail herein, but components generally as described and shown in West German Patent Application No. 2849945 published 5th july, 1979 (Case 266) can be used. In operation, the auxiliary combustor 181 is supplied with fuel appropriately to accelerate the turbine wheel 16 to a substantial rotational speed. This correspondingly accelerates the compressor wheel 18 to a relatively high rotational speed for supply.of a substantial quantity of charge air to the auxiliary combustor 181 for combustion. As soon as a desired minimum charge air pressure level is reached, the engine 14 may be started. Starting of the engine ingests a portion of the charge air for ignition with fuel to provide exhaust gases for passage through the exhaust conduit 30 and the combustor 181 for rotatably driving the turbine wheel 16. As can be seen the hydraulically driven turbine wheel 56 together with the auxiliary combustor 181 provide means for making available charge air at sufficient quantity and pressure for starting the engine 14. This system is particularly suited for use with a low compression engine wherein charge air at elevated pressure is a pre-requisite for the engine to reach self-sustaining operation upon starting. The high pressure control valve 262 is operated to cease supply of high pressure oil to the hydraulic turbine 56 as soon as the auxiliary combustor 181 accelerates te turbocharger turbine wheel 16 to a speed sufficient to supply the combustor 181 with sufficient charge air for self-sustained operation. If desired, the high pressure oil is then available for driving an hydraulic motor for operating a fan for use in cooling the charge air in a charge air heat exchanger. However, this arrangement is not specifically included in the drawing for purposes of clarity. Once the engine 14 is started, the auxiliary combustor 181 may be shut down by virtue of discontinuing fuel supply thereto, whereupon the engine 14 will operate as a conventional turbocharged engine with exhaust gases therefrom flowing freely through the combustor. However, if desired, the auxiliary combustor 181 may be suitably controlled to supplementally drive the turbocharger 12 at relatively low speed engine operating conditions to maintain the engine in a relatively high load-carrying state. That is, the fuel control 183 may be suitably scheduled in accordance with engine operating conditions as by a charge air pressure conduit 185 coupled to the charge air supply conduit 34. The fuel control 183 responds to this parameter to provide a relatively high fuel flow to the combustor 181 at relatively low engine speed, and to reduce progressively the fuel flow with increases in engine speed to supplement the energy level of gases supplied to the turbine wheel 16 in accordance with engine load-carrying requirements The by-pass conduit 180 includes by-pass valve means 186 comprising a check valve for the preventing reverse flow from the exhaust conduit 30 to the charge air supply conduit 34. The by-pass valve means 186 also includes a closure valve for selectively closing the bypass conduit 180 to charge air flow. This closure valve is opened by a suitable valve operator 187 for supply of charge air to the combustor 181 for initiation of combustor combustion. The closure valve is also retained open throughout relatively low speed engine operation to allow a portion of the charge air to by-pass to the combustor 181 for use in supplementing the energy level of gases supplied to the turbocharger. However, at relatively high engine speed, the closure valve is closed to prevent by-pass of charge air to the combustor 181 whereby all of the air is supplied to the engine. Importantly, at high engine speed,supplemental driving of the turbocharger is not required, and the oxygen content of engine exhaust gases is sufficient to maintain when desired, a pilot flame in the combustor 181. The valve operator 187 may be manually controlled, or may be automatically controlled in response to engine operating parameters such as charge air pressure, etc. Alternatively, if desired, the valve operator 187 and the closure valve may be omitted by appropriately sizing the turbocharger 12 to match engine air flow consumption requirements. That is, the volumetric intake requirments of the engine are proportional to engine speed. With a turbocharger designed generally to match engine air intake flow requirements at relatively high engine speed, by-pass air becomes unavailable for bypass flow directly-to the combustor 181 at relatively high engine speed by virtue of the engine ingesting all of the supplied charged air. However, at lower engine speeds, the engine fails to ingest or require the total volume of supplied charge air flow, whereby an excess portion of the charge air flow becomes available for bypass to the combustor 181. Importantly, the combustion system using either the closure valve or requiring a matching of the turbocharger to engine air flow requirements is discussed in more detail in German Application Serial No. 2849945 referred to above. Various modifications and improvements to the invention set forth herein are believed to be possible within the scope of the art. For example, a variety of control schemes for the control valve 262 are possible, including the electronic systems and the like responsive to one or more engine and/or turbocharger operating parameters. Moreover, the invention is adaptable for use with conventional four-cycle internal combustion engine, or with. two-cycle internal combustion engine. With two-cycle engines, the control scheme for the control valve 262 may be designed so as to supplementally drive the turbocharger in a manner allowing elimination of the conventional scavenging blower. Further the control valve 262 may be adapted also to couple the high presure oil directly to the bearing supply conduit 50 via the line 66, whereby the control valve 262 is capable of three-position operation to effect a) driving of the non-ventilated hydraulic turbine 56,. b) driving of a fan for cooling the charge air, or c) unloading of the high pressure oil pump 58.

Claims: CLAIMS 1. A turbocharger system for supplying charge air to a combustion engine comprising a turbocharger including a turbine driven by engine exhaust gases, a hyudraulic turbine, a compressor driven alternatively by the exhaust gas turbine and/or the hydraulic turbine to supply charge air to the engine, a combustor in the conduit between the engine exhaust and the exhaust gas turbine, means for supplying high pressure liquid to the hydraulic turbine to drive the compressor to provide a supply of charge air, means for by-passing at least some of the said charge air to flow through the combustor and exhaust gas turbine (without passing through the engine), and mens for supplying fuel to the combustor under certain engine operating conditions (e.g. before starting). 2. A system as claimed in Claim 1 in which the hydraulic turbine is non-ventilated. 3. A system as claimed in Claim 1 or Claim 2 in which the engine has a hydraulic system including means for supplying hydraulic fluid to the turbocharger for lubrication and the liquid employed for driving the hydraulic turbine comprises a portion of the liquid in the said hydraulic system. 4. A system as claimed in Claim 3 including a low pressure pump supplying liquid for lubrication and a high pressure pump for supplying liquid to drive the hydraulic turbine. 5. A system as claimed in Claim 4 including valve means for selectively opening and closing the supply of liquid from the high pressure pump to the hydraulic turbine. 6. A system as claimed in any one of the preceding claims in which the means for by-passing charge air is controlled in response to engine operating conditions. 7. A system as claimed in Claim 6 including means for by-passing charge air to the combustor prior to starting of the engine and for closing such supply when the turbocharger reaches self sustaining operation. 8. A system as claimed in any one of the preceding claims in which the means for supplying fuel to the combustor is dependent upon engine operating conditions. 9. A system as claimed in Claim 8 in which the means for supplying fuel to the combuster is arranged to do so generally in inverse proportion to engine speed. 10 A system as claimed in any one of the preceding claims including a charge air heat exchanger for cooling the charge air between the compressr and the engine 11. A system as claimed in Claim 10 including a fan for forcing ambient air through the heat exchanger and a hydraulic motor driving the fan, the valve means controlling the supply of fluid alternatively to the hydraulic turbine or the said hydraulic motor. 12. A system as claimed in any one of the preceding claims in which the exhaust gas turbine, the hydraulic turbine and the compressor are mounted on a common shaft. 13. A system as claimed in Claim 12 in which the turbine wheel is mounted within a turbine housing, the compressor wheel is mounted within a compressor housing, and between the turbine housing and the compressor housing there is a central housing including bearings supporting the shaft, the hydraulic system serving to lubricate the said bearings. 14. A system as claimed in Claim 12 or Claim 13 in which the central housing includes a turbine flow chamber having an inlet port communicating with the liquid supply and an outlet port communicating with the bearings so as to apply a back pressure to the said flow chamber to cause substantially immediate flooding of the flow chamber with fluid when high pressure fluid is supplied to drive the hydraulic turbine so that the latter operates in the non-ventilated environment. 15. A system as claimed in any one of Claims 12-14 including means on the shaft for pumping air from the flow chamber when high pressure fluid is supplied thereto and for pumping liquid from the flow chamber when supply thereof ceases. 16. A system as claimed in any one of the preceding claims in which the by-pass conduit is controlled by a valve responsive to engine operating conditions to close for at least some conditions of engine operation. 17. A system as claimed in any one of Claims 1-15 in which the turbocharger is sized to provide charge air flow generally matching engine air flow consumption requirments at relatively high speed engine operation whereby the charge air for by-passing through the by-pass means is unavailable due to engine consumption when the engine is operated at relatively high speed, a check valve being provided for preventing the flow of exhaust gases through it. 18. A method of operating a turbocharger system including a turbocharger for supplying charge air to a combustion engine and including a turbine driven by engine exhaust gases, a hydraulic turbine, and a compressor driven alternatively by the exhaust gas turbine and/or the hydraulic turbine to supply charge air to the engine, which method includes supplying liquid at a relatively high pressure from a hydraulic system to the hydraulic turbine prior to starting of the engine to drive the compressor and provide a charge air output supplying at least part of the said charge air output to a combustor interposed between the engine exhaust and the exhaust driven turbine supplying fuel to the combustor to produce combustion with the charge air to provide high energy exhaust gases, and supplying the said gases to the exhaust gas turbine for accelerating it to self-sustaining operation and starting the engine. 19. A method as claimed in Claim 18 which includes by-passing a portion of the charge air flow around the engine to the combustor at relatively low-speed engine operating conditions to supplement the energy level of gases flowing through the combustor. 20. A method as claimed in Claim 19 which includes controlling the by-passed charge air flow with a bypass valve, and closing the said by-pass valve at relatively high speed engine operating conditions. 21. A method as claimed in Claim 19 in which the by-passing¯step comprises sizing the turbocharger generally to match the engine charge air flow consumption requirements at relatively high speed engine operation, whereby by-pass flow is unavailable at the said high operating speed 22. A method as claimed in any one of Claims 18-21 which includes ceasing to supply high pressure liquid from the hydraulic system to the hydraulic turbine when the combustor and turbocharger reach self-sustaining operation. 23. A method as claimed in Claim 22 which includes supplying the high pressure liquid to operate a fan for forcing ambient air across a charge air heat exchanger to cool the charge air prior to its supply to the engine. 24. A method as claimed in any of Claims 18-23 in which the hydraulic system includes means which supply liquid at relatively low pressure for lubrication of the turbocharger.

Inventors: BYRNE, JOE L., KOBAYASHI, ROBERT J., NANCARROW, JAMES H.
Applicants: THE GARRETT CORPORATION
Application year: 1981
Main classification: F02B37
IPC codes: F02B37, F02B29, F02B39