CA1060220A

CA1060220A - Rankine cycle turbocharger drive

Info

Publication number: CA1060220A
Application number: CA283,153A
Authority: CA
Inventors: Adell W. Brecheisen
Original assignee: Deere and Co
Current assignee: Deere and Co
Priority date: 1976-07-30
Filing date: 1977-07-20
Publication date: 1979-08-14
Also published as: DE2729998A1; AU506129B2; FR2359974B1; MX144884A; AR219498A1; IT1079983B; FR2359974A1; GB1534668A; ES461134A1; AU2470877A

Abstract

RANKINE CYCLE TURBOCHARGER DRIVE

Abstract of the Disclosure A Rankine cycle engine driven by heat from the exhaust, oil and coolant of a turbocharged internal combustion engine is coupled to assist in the driving of the turbocharger to compen-sate for the decrease in engine torque and torque response due to poor turbocharger efficiency at low speeds. The Rankine cycle engine includes a working fluid such as Freon which is pumped through a preheater for heating by the oil and coolant and through a vapor generator for vaporization in response to heat from the engine exhaust. The vaporized working fluid is applied to an expansion device such as a turbine for producing mechanical motion prior to being condensed for recirculation. The turbine or other expansion device is coupled to the turbocharger by a clutch which engages to assist in driving the turbocharger when the speed of the turbocharger drops below a nominal value.
Alternatively, the turbine or other expansion device is coupled to drive a compressor for generating pressurized air which is combined with the pressurized air from the turbocharger.

Description

The present invention relates to turbocharged engines, and more particularly to turbocharged internal combustion engines.
Turbochargers have proven to be useful devices in improving the performance of internal combustion engines, particularly high load, high performance diesel engines. Such turbochargers are typically comprised of a radial inflow gas turbine and a radial compressor with their rotating components mounted on a common shaft. The hot exhaust from the engine is directed onto the gas turbine to produce rotation of the shaft and the included com-pressor impeller. The rotating impeller produces a pressurized supply of cool air which is introduced into the cylinders of the engine to improve efficiency and performance.
One problem found in most turbochargers is a pronounced reduction in performance which occurs at low speeds. Turbo-chargers capable of producing large quantities of pressurized cool air at rotational speeds on the order of 40,000-50,000 rpm or greater frequently become rather ineffective at lower speeds, largely due to loss in efficiency. The narrow operating range is a direct result of the characteristics of both the turbine and compressor components of the turbocharger. The net result is that torque drops off rapidly at engine speeds lower than the peak torque speed. In addition when a turbocharged engine, initially operating at low speed and torque, is required to accelerate and start a load, the response is slow due to a lag between the time at the demand for power and the time at which the power becomes available. This lag is due to the rotational inertia of the rotating components of the turbocharger.
The low speed torque and torque response characteristics of a turbocharged engine are particularly important in certain applications of the internal combustion engine such as in farm machinery. In a tractor, for example, the engine may be driven ... ' , . : ' , ~ ' . :

~060Z20 1 at a fixed gear ratio under a variety of different loading condi-tions which may cause the speed of the engine to vary sub-stantially. Also a tractox is expected to be able to start a load in the gear at which it will be operated. Ideally, the engine should experience no significant loss in the torque as engine speeds vary between high and low values.
It is known to provide a power boost for an internal combus-tion engine using a Rankine cycle engine operating in response to heat from the internal combustion engine. Examples of such systems are described in an article entitled "Bottoming-Cycle Engines" by E. F. Lindsley, Popular Science, January, 1976. The Lindsley article describes several different applications where heat from the exhaust, oil and coolant of an internal combustion engine is transferred to a working fluid. The heated fluid is used to produce rotational motion which is imparted directly to the drive shaft of the internal combustion engine. This is accomplished through use of a chain coupled between gears of appropriate ratio on the drive shaft of the internal combustion engine and on the rotatable shaft of an expansion unit within the Rankine cycle engine.
The arrangements disclosed in the Lindsley article do not confront the problem of the drop off in torque and tor~ue response of a turbocharger at low speeds of operation. Rather, the Lindsley arrangements are concerned with conserving heat energy from the internal combustion engine which would otherwise be wasted and of returning a portion of that heat energy in the form of mechanical motion directly to the drive shaft of the internal combustion engine. The problem is defined as one of providing power assist to the internal combustion engine at all speeds, particularly in the case of high performance diesel engines, and accordingly, the Rankine cycle engine is directly coupled to the drive shaft of the internal combustion engine or 1 to the transmission such as by a chain drive to provide a con-tinuous source of supplemental power.
Accordingly, it would be desirable to be able to correct or compensate for the poor torque characteristics of turbocharged engines at low speeds.
It would furthermore be desirable to improve the performance of a turbocharger at low engine speeds using existing energy from an internal combustion engine associated with the turbocharger.
It would furthermore be desirable to be able to employ a closed cycle engine such as a Rankine cycle engine powered at least in part by heat from an internal combustion engine for improving the operation of a turbocharger coupled to the internal combustion engine.
Summary of the Invention Engine arrangements according to the invention employ an auxiliary engine powered by wasted or excess energy from a main engine to improve the performance of a turbocharger associated with the main engine. The auxiliary engine preferably comprises a closed cycle engine such as a Rankine cycle engine powered by heat from the main engine. Where the main engine comprises an internal combustion engine, heat is transferred from the exhaust, oil and coolant of the internal combust~on engine to a working fluid which is vaporized to produce mechanical motion in the Rankine cycle engine. The mechanical motion may be coupled to the turbocharger through a clutch whlch is selectively engageable to provide the mechanical motion to the turbocharger at low speeds. Alternatively, the mechanical motion may be used to drive a device such as a compressor or auxiliary turbocharger for providing a supply of pressurized air to the main turbocharger.

' Brief Description of the Drawings - The foreging and other objects, features and advantages of the invention will be apparent from the following more particular ~060220 1 description of preferred embodiments of the invention, as illus-trated in the accompanying drawings, in which:
Fig. 1 is a basic block diagram of an engine arrangement in accordance with the invention;
Fig. 2 is a detailed block diagram of the engine arrangement of Fig. 1 illustrating one arrangement for coupling the Rankine cycle engine to the turbocharger;
Fig. 3 is a detailed block diagram illustrating a different arrangement for coupling the Rankine cycle engine to the turbo-charger; and Fig. 4 is a detailed block diagram of a preferred embodimentof a Rankine cycle engine for use in the engine arrangement of Fig. 1.
Description of the Preferred Embodiment Fig. 1 illustrates an engine arrangement 10 in accordance with the invention. The engine arrangement 10 includes a main engine in the form of an internal combustion engine 12 and an associated turbocharger 14. The turbocharger 14 is of conven-tional design and may include a turbine driven by the exhaust from the internal combustion engine 12 and an impeller or com-pressor coupled to the turbine via a common shaft for providing a source of pressurized cool air to the internal combustion engine 12. The pressurized cool air is typically introduced direc*ly into the cylinders of the internal combustion engine 12, providing for combustion of more fuel and enabling the engine to run hotter and more efficiently.
As previously noted, turbocharged engines typically experi-ence a pronounced reduction in torque and torque response when the operating speed thereof drops below a certain level. This occurs at speeds below about 40,000-50,000 rpm in the case of conventional turbochargers. In accordance with the invention the torque characteristics of the engine 12 are significantly 1 improved by use of a closed cycle engine in the form of a Rankine cycle engine 16. The Rankine cycle engine 16 is powered by the excess or waste heat from the internal combustion engine 12. The Rankine cycle engine 16, in turn, is coupled to drive the turbo-charger 14 either through direct mechanical linkage as in the case of Fig. 2 or via a compressor or auxiliary turbocharger which provides pressurized air to the turbocharger 14 as in the case of Fig. 3.
Fig. 2 shows the engine arrangement 10 of Fig. 1 in consider-ably greater detail. AS seen in Fig. 2 the turbocharger 14 includes a turbine 18 and a compressor 20 coupled together via a common shaft 22. The exhaust from the internal combustion engine 12 is applied to the turbine 18, producing rotation of the shaft 22 and the compressor 20. The compressor 20 forces cool air into the internal combustion engine 12. After passing through the turbine 18 the exhaust is applied to a vapor generator 24 forming a part of the Rankine cycle engine 16. At the same time the oil and coolant from the internal combustion engine 12 are circulated through a preheater 26 within the Rankine cycle engine 16.
The vapor generator 24 and the preheater 26 form part of a closed loop 28 for a working fluid within the Rankine cycle engine 16. The closed loop 28 also includes a pump 30 at the input of the preheater 26, an expansion device 32 at the output of the vapor generator 24 and a condenser 34 at the output of the expansion device 32. The pump 30 pumps the working fluid to the preheater 26 where the fluid is heated by the oil and coolant from the internal combustion engine 12. Thereafter, the working fluid is passed to the vapor generator 24 where it is heated by the exhaust from the internal combustion engine 12 to cause vaporization of the working fluid. The vaporized working fluid is passed to an expansion device 32 where the energy of the fluid is converted into mechanical motion in the form of rotation of a 1 shaft 36. The working fluid is then condensed by the condenser 34 and advanced to the pump 30 for recycling through the closed loop 28 of the Rankine cycle engine 16.
The shaft 36 is coupled to the shaft 22 through a clutch 38 and a shaft 40. The expansion device 32 produces rotation of the shaft 36, so that when the clutch 38 is engaged the turbocharger 14 is driven by the Rankine cycle engine 16. Since the need for improvement of the torque and torque response of the engine 12 occurs at low speeds, the clutch 38 is preferably a one-way clutch such as of the concentric shaft type. This provides for automatic uncoupling of the Rankine cycle engine 16 from the turbocharger 14 when the turbocharger is rotating at high enough speeds for satisfactory performance. However, when reduction in the exhaust from the internal combustion engine 12 is such that the inertia and efficiency of the turbine 18 and the compressor 20 would otherwise seriously impair the performance of the turbo-charger 14, the clutch 38 automatically couples the turbocharger 14 to the Rankine cycle engine 16 to restore the speed of the turbocharger 14 to an optimum level.
In some situations it is desirable that the turbocharger 14 provide a high pressure charge of cool air to the internal combustion engine 12 at all times. In such situations the alter-native arrangement shown in Fig. 3 may be used to couple the expansion device 32 of the Rankine cycle engine 16 to the turbo-charger 14. In the arrangement of Fig. 3 the mechanical motion produced by the expansion device 32 is used to turn a compressor 50. The compressor 50 which may be of any appropriate conven-tional design and which may comprise the compressor portion of an auxiliary turbocharger responds by generating pressurized cool air which is supplied to the turbocharger 14 in the region of the compressor 20. The air from the compressor 50 combines with the pressurized air from the compressor 20 to provide a high pressure charge of cool air to the internal combustion engine 12.

.

1~60Z20 1 The details of a preferred arrangement of the Rankine cycle engine 16 are shown in Fig. 4. The pump 30 in the arrangement of Fig. 4 can comprise any positive displacement type pump such as those typically used in refrigeration systems. For example, the pump 30 may be of the type in which pistons arranged around the pump are operated by movement of a swash plate. The closed loop 28 is comprised of any appropriate conduit material for carrying the working fluid under high pressure and temperature. Examples of conduit material which can be used include hydraulic hose and metal tubing or pipe. The working fluid may comprise an appro-priate material such as one of the fluorocarbon refrigerants.
In the arrangement of Fig. 4 the preheater 26 comprises a heat exchanger 52 of the liquid-liquid type having three differ-ent circuits. A first circuit of the heat exchanger 52 is coupled to receive the hot oil from the internal combustion engine 12. A second circuit is coupled to receive hot coolant from the radiator of the internal combustion engine 12. A third circuit receives the working fluid from the pump 30. The heat exchanger 52 is designed to maximize transfer of heat from the oil and coolant to the working fluid prior to recirculating the oil and coolant back to the internal combustion engine 12 and the radiator therefor. The vapor generator 24 comprises a heat exchanger 54 of the gas-liquid type in the arrangement of Fig. 4.
The heat exchanger 54 is coupled to receive the hot exhaust gases from the turbine 18 of the turbocharger 14 and to maximize the transfer of heat from the exhaust gases to the working fluid.
rrhis vaporizes the working fluid which is then circulated to the expansion device 32. In the arrangement of Fig. 4 the expansion device 32 comprises a turbine 56 coupled to rotate the shaft 36 in response to the vaporized working fluid. The rotating shaft 36 may be used to drive the turbocharger 14 via the clutch 38 as shown in the arrangement of Fig. 2, or it may be used to drive ~060Z~0 1 the compressor 50 in the arrangement of Fig. 3. The vaporized working fluid passing the turbine 56 is condensed in the con-denser 34 which comprises a heat exchanger 58 of the gas-liquid type in the arrangement of Fig. 4. The vaporized working fluid is condensed into a liquid by cool air which receives the heat from the working fluid to enable the working fluid to condense.
The condensed working fluid is then circulated to the pump 30.
Where desired, the heat exchanger 58 may comprise a portion of the radiator of the internal combustion engine 12 with the cool air being provided by the radiator fan.
While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims

The embodiments of the invention in which an exclusive property or privileged is claimed are defined as follows:

1. An engine arrangement comprising the combination of an internal combustion engine having exhaust, oil and coolant, a turbocharger driven at least in part by the exhaust for providing pressurized gas to the internal combustion engine, a Rankine cycle engine for assisting in the driving of the turbocharger when the speed of the turbocharger is below a selected level, the Rankine cycle engine including a working fluid, means for trans-ferring heat from the exhaust, oil and coolant of the internal combustion engine to the working fluid to heat the working fluid and means for undergoing mechanical motion in response to the heated working fluid, and means responsive to the speed of the turbocharger for coupling the means for undergoing mechanical motion to drive the turbocharger whenever the speed of the turbo-charger is below the selected level.

2. The invention defined in claim 1, wherein the means for transferring heat from the exhaust, oil and coolant includes first heat exchanger means for transferring heat from the oil and coolant of the internal combustion engine to the working fluid to initially heat the working fluid and second heat exchanger means for thereafter transferring heat from the exhaust of the internal combustion engine to the initially heated working fluid to further heat the working fluid.

3. The invention defined in claim 2, wherein the second heat exchanger means vaporizes the working fluid and the means for undergoing mechanical motion is responsive to the vaporized working fluid, and wherein the Rankine cycle engine further includes means for condensing the vaporized working fluid and means for pumping the condensed working fluid.

4. The invention defined in claim 1, wherein the working fluid comprises a fluorocarbon refrigerant.

5. The invention defined in claim 1, wherein the means for undergoing mechanical motion includes a rotatable element, and the means for coupling comprises clutch means coupled between the means for undergoing mechanical motion and the turbocharger.

6. An engine arrangement comprising the combination of an internal combustion engine having exhaust, and having oil and coolant flowing through defined paths therefor, a turbocharger driven at least in part by the exhaust for providing pressurized gas to the internal combustion engine, an auxiliary engine com-prising a closed loop system containing a working fluid, pumping means in the closed loop system for pumping the working fluid in a given direction in the closed loop system, a first heat exchanger in the closed loop system downstream of the pumping means and coupled in the paths of the oil and coolant of the internal combustion engine, the first heat exchanger being opera-tive to transfer heat from the oil and coolant to the working fluid to initially heat the working fluid, a second heat exchanger in the closed loop system downstream of the first heat exchanger and coupled to receive the exhaust from the turbocharger, the second heat exchanger being operative to transfer heat from the exhaust to the initially heated working fluid to vaporize the working fluid, a mechanical motion device coupled to the closed loop system downstream of the second heat exchanger and operative to undergo mechanical motion in response to the vaporized working fluid, means coupled in the closed loop system between the mechan-ical motion device and the pumping means for condensing the vaporized working fluid from the mechanical motion device, and a clutch disposed between and operative to couple the mechanical motion device to drive the turbocharger whenever the speed of the turbocharger is below a predetermined level.