Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
10602Z0
1 RANKINE CYCLE TURBOCHARGER DRIVE
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
1060ZZ0
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
10602Z0
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
1060ZZ0
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.
