US3250068A - Multiple turbocharger system - Google Patents

Description

MULTIPLE TURBOCHARGER SYSTEM Filed Dec. 23, 1963 4 Sheets-Sheet 1 I nventor NICHOLAS MART/IV FEL/X VULU/IMY B 3 M agul A ttorneys,

May 10, 1966 vu 3,250,068

7 MULTIPLE TURBOCHARGER SYSTEM Filed Dec. 23, 1963 4 Sheets-Sheet 2 Inventor N/CHULA-S MART/N Ffl/X VUZU/JMY Attorneys.

May 10, 1966 N. M. F. VULLIAMY MULTIPLE TURBOCHARGER SYSTEM 4 Sheets-Sheet 3 Filed Dec. 25, 1965 5 z mam 55 50+ Inventor NICHOLAS MAPT/N Ffl/X Vl/ZZ/AM) :2 J04"! Altorneys.

May 10, 1966 N. M. F. VULLIAMY MULTIPLE TURBOCHARGER SYSTEM 4 Sheets-Sheet 4 Filed Dec. 25, 1963 a [m 5 m A \A/ m ,M w [w P a r x m 7 M ab t J0 A V FM/ W 5 MA W W WW. l I W f j 5 r /i/ 4D N tlorneys.

United States Patent 3,250,068 MULTHLE TURBOCHARGER SYSTEM Nicholas Martin Felix Vulliamy, Broadway Gardens, Peterborough, England, assignor to F. Perkins Limited, London, England, a British company Filed Dec. 23, 1963, Scr. N 0. 332,581 Claims priority, application Great Britain, Dec. 21, 1962, 48,346/62 '7 Claims. (Cl. 60-43) This invention relates to a pressure charging system for internal combustion engines and more particularly to a pressure charging system for compression ignition reciprocating engines in which the energy of exhaust gas from the engine is used to pressurize air entering the engine.

Devices used topressurize air fed into an internal combustion engine are generally known as superchargers while those using the energy of exhaust gases. of internal combustion reciprocating engines to pressurize air fed to the engine are commonly known as turbine-compressor units or turbo-chargers and usually comprise a turbine driven by exhaust gases and driving a compressor.

The use of superchargers both turbine driven and direct driven to increase the mean effective pressure and hence torque of internal combustion engines is well known.

This increased torque is generally available only at relatively high engine speeds and thus provides increased horsepower at high speeds while having little effect of the horsepower output of the engine at lower and medium speeds.

By providing increased pressure charging at low speeds and decreasing the charging at higher speeds it is possible to not only provide an engine system having a relatively constant power output through a wide speed range but one requiring a minimum of torque multiplication ratio changes by mechanical or hydraulic transmissions used to transmit the engine power to the engine load. The same increased charging at low speeds coupled with high charging at higher speeds should provide a system having increasing horsepower with speed increase.

It is therefore an object of the present invention to provide an engine pressure charging system that will provide a relatively great mass fiow of air at low speeds and a lesser flow at higher speeds.

Another object of the invention is to provide a charging system having a plurality of turbine-compressor units with means for varying the overall pressure ratio between the inlet air the air entering the engine.

It is still another object to provide a charging system. having aplurality of turbine-compressor units with means FIG. 3 is a plan view of a third embodiment which is a modification of the FlG. 1 embodiment,

FIG. 4 is a plan view of a fourth embodiment which is a modification of FIG. 2,

FIG. 5 is a plan view of a fifth embodiment which is v a further modification of FIG. 4, and

for varying the mass flow to the engine in accordance with engine conditions so as to provide a relatively large mass flow at low speeds and a relatively smaller mass fiow at higher speeds.

Still another object is to provide a charging system that will give an engine increased torque output over a wide range of speeds.

A further object is to provide a pressure charging system for an engine wherein the torque characteristics of -FIGS.,6 and 7 are performance graphs.

The present invention utilizes a pressure charging system for an internal combustion engine that comprises at least first and second turbine compressor units arranged so that exhaust gas from the engine passes through the turbine of the first unit, and exhaust gas control means positioned downstream of the turbine of the first unit so that selectively variable quantities of engine exhaust gas may be passed to the turbine of the second unit.

Preferably air control means is provided between the compressors of the first and second units, so that all of the air supplied to the engine passes through one of the compressors, and selectively variable quantities of this air maybe passed through the other of said compressors.

More specifically, each compressor has an inlet and an outlet, duct means connecting the outlet of said one compressor to the inlet of said other compressor, and further duct means connecting the outlet of said other compressor to the engine intake, said air flow control means being disposed in the duct means between said compressors and being controllable so that air supplied to the engine may be supplied to the other compressor in selectively variable quantities, and the total air supplied to the engine passes through said one compressor. The air control valve means may be closed, so that air flow is completely shut off to said other compressor.

Further, according to the present invention I provide a pressure charging system in an internal combustion engine comprising air inlet duct means connected tothe air intake manifold of the engine, exhaust gas outlet duct means connected to the exhaust gas manifold of the engine, two air compressors in said inlet duct means, two turbines in said outlet duct means, driving connections between the turbines and compressors, by which they form turbine compressor units, an inlet for external air to said inlet duct means, an outlet to atmosphere in said outlet duct means, and valve means for selectively apportioning the gas ejected by one turbine between said outlet and the other turbine, so that, selectively, "both compressors may be driven so as to provide first and second stage compression.

The control means may comprise valves which are of the on/olf type or are capable of metering the flow between the on and off positions. The control means may be actuated by a connection to the throttle or in response to engine or load speed or pressure signals or combinations of these signals.

Referring now to the drawings in which the arrows indicate the direction of flow of air and exhaust gas, FIG.

, '1 shows an engine :1 with an intake manifold 2 and an exhaust manifold '3. A first stage compressor 4 draws in air through an inlet filter 5 and passes it to a duct 6 which becomes the inlet for a second stage compressor 7. The latter then delivers air to the intake manifold 2 and engine *1. Exhaust gas from the engine exhaust manifold 3 passes through a first stage turbine 8 whichdrives the second stage compressor 7 through a shaft 9. The exhaust gas leaving the first stage turbine 8 flows through a duct 10 to a flow control valve 11 which apportions the total flow into ducts 12 and 13A. The duct ".12 leads to a second stage turbine 14 that exhausts to atmosphere through a duct 13 to which the pipe 13A is also connected. A shaft 15 transmits drive from the second stage turbine 14 to the first stage compressor4.

FIG. 2 shows a second embodiment in which parts corresponding to those in FIG. 1 are indicated by the same reference numerals with the addition of the letter A. In this embodiment, the compressor 7A is the first stage compressor and is connected to inlet filter A, and the compressor 4A is the second stage compressor and is connected to the duct 2A leading to the engine intake manifold.

FIG. 3 shows a third embodiment, in which parts corresponding to those in FIG. 1 are indicated by the same numerals with the addition of the letter B. In FIG. 3 there is a by-pass duct '18 extending between the intake filter 5B and the inlet duct 63 for compressor 7B. A valve '19 is located between the ducts '18 and 612 that is similar to the valve 11A of the FIG. 2 embodiment for apportioning the incoming air flow between the compressor 4B and the by-pass duct 18. Flow to the compressor 4B may thus be metered, proportioned or stopped as desired.

FIG. 4 shows a fourth embodiment, in which parts corresponding to those in FIG. 2 are indicated by the same numeral and the letter C instead of A. In this embodiment, the second stage compressor 4C may be partially by-passed by a valve 20 located in a duct 19 joining the duct 6C with the engine intake manifold 2C. This does not effect a complete stoppage of flow to the compressor 4C.

FIG. 5 shows a fifth embodiment in which parts corresponding to FIG. 4 are indicated by the same numerals and the letter D instead of C. In this embodiment, additional valves 21 and 22 are inserted in the duct 6D and engine intake 2D respectively, and may be used to isolate completely the compressor 4D.

With regards to the five embodiments described, the valve 11 of the FIG. 1 embodiment, and the corresponding valve in the other embodiments on the exhaust side of the engine can be arranged to never completely shut off flow to the turbine 14 or the corresponding turbine in the other embodiments. The turbine may then run at a low speed so that its compressor does not obstruct the flow of arr.

It will be seen that the principal advantage to be gained from the use of the present invention is an improved torque characteristic in middle to higher engine speeds of a diesel engine. Curve NA shown in FIG. 6 shows a torque versus engine speed characteristic for a typical normally aspirated diesel engine. It will be seen that peak torque occurs at approximately 40 percent of maximum engine speedand between this point and maximum speed the torque falls off gradually. This type of torque curve between 40 percent and 100 percent maximum speed enables a vehicle having a diesel engine, travelling at maximum speed say to reach equilibrium at a lower speed with an additionally applied load arising for instance from an increase in road gradient. This as sumes that the load is not so great as to be beyond the maximum torque capabilities of the engine in the chosen transmission gear ratio.

The lower portion of FIG. 6 shows a graph in which the pressure ratio across the compressors and the torque which corresponds to brake mean effective pressures are drawn against percentage of maximum permissible enginespeed. The curve AB represents a pressure ratio curve for a single turbo-charger and such a turbo-charger when associated with an engine and using the energy of the engine exhaust gas could give rise to the curve ST in the upper torque part of the graph. It will be seen that the peak torque developed by the engine served by a single turbo-charger occurs at about 65 percent maximum speed and so the gears of the vehicle would need to be changed at a higher speed than with the normally aspirated engine (curve NA) where the maximum torque developed is at approximately 40 percent of maximum speed.

Referring to the invention as embodied in the FIG. 1 example, the valve 11 is controlled to be fully open to the turbine 14 until roughly 40 percent of maximum engine speed is attained, in which case both turbines 4, '7 are driven, and a high torque is developed (curve TT FIG. 6). The valve 11 is then controlled to close progressively to the turbine 14 and exhaust through the duct 13A as the engine speed increases until its maximum speed is reached, at which point the valve 11 is almost closed, allowing only sufiicient exhaust gas to pass to the turbine 14 to turn it so as to keep the compressor 4 from obstructing air flow to the engine. The pressure ratios across compressors 4 and 7 of FIG. 1 are shown by curves C DE and A 3 respectively and this overall pressure ratio is shown by curve CFB. This is obtained by multiplying ordinates of the pressure ratios of the curves C DE and NB. Since the pressure ratio across the compressors is a measure of the mass flow through the engine and the variation of the mass flow is an approximate measure of the variation of power developed by the engine it follows that the CFB curve will indicate a substantially constant horsepower between the speed at peak torque and the maximum engine speed. This is advantageous in that a high horsepower can be developed at low speed thus opening the possibility of reducing the number of gear changes or eliminating them altogether. It will be seen that by comparing the curves NA and T1 that the peak torque is obtained at substantially the same percentage of engine speed and by this means the flexibility of the engine is maintained while improving the torque characteristic.

.FIG. 7 shows a diagram similar to FIG. 6 but in this case the system is arranged to give rather less peak torque (curve TT than before while the valve 11 is progressively opened to a degree short of fully open. The embodiment of FIG. 4 will provide a torque curve of this type and enables the torque at maximum speed to be greater than with the single turbo-charger layout illusstrated by curve ST and the second turbine 14 is always providing some pressure increase.

The particular use requirements such as power and fuel consumption as well as maximum torque requirements have to be taken into consideration, and it is not necessarily always desirable that the torque should be the maximum obtainable. Hence the particular form of the system employing the invention will be dictated by these requirements.

The invention extends, therefore, to the speed range over which turbo-charging is effective and efiicient, and therefore offers considerable advantages from the point of view of performance and economy.

It will be understood that the valves 11, 11B, 19, 2t), 20D and 21 can be controlled by any desired means responsive to given changes in engine operating conditions, load conditions or demand. For example these valves could be controlled in accordance with engine speed, torque or pressure, with throttle position, with load or load speed.

The use of three or more turbo-chargers may give further gains over a twin turbo-charger arrangement, but the cost of further units may not be justified by the advantage to be gained.

Changes and modifications will be apparent to those skilled in the art as will other applications of the invention. These changes and applications are within the scope of the invention which is limited only by the following claims.

I claim:

1. A pressure charging system for an internal combustion engine operable between a minimum and a maximum speed and wherein said charging system causes said engine to provide predetermined torque and horsepower outputs at various speeds, said system including a pair of exhaust turbine-compressor units connected in operative series, one of said units providing a first stage of compression of inlet air to said engine and the other of said units providing a second stage of compression of said inlet air prior to intake by the engine, means responsive to engine speed for controlling the effectiveness of one of said units, said means being operable above a predetermined percent of the maximum engine speed to gradually reduce the amount of compression of said inlet air by said one unit so that below said predetermined percent of said maximum engine speed both units are fully efiective to provide maximum engine torque and at speeds above said predetermined percent of said maximum engine speed said first unit decreases in efiectiveness to provide a relatively large decrease in engine torque as the engine speed increases to the maximum speed.

2. The pressure charging system of claim 1 wherein said engine speed responsive means begins to reduce the effectiveness of said one unit at approximately 40% of said maximum engine speed.- I

3. The pressure charging system of claim 2 wherein said engine speed responsive means fully reduces the efiectiveness of said one unit at approximately said maximum speed.

4. The pressure charging system of claim 1 wherein said engine speed means is responsive to control said one unit to provide a rapidly increasing overall total pressure ratio of the pair of units with increase of engine speed from the minimum speed to said predetermined percent of maximum speed and to control said one unit to provide a gradually decreasing overall total pressure ratio of the pair of units with increase of engine speed from said predeter-mined percent of maximum speed up to said maximum speed.

5. The pressure charging system of claim 1 wherein said means responsive to engine speed for controlling the effectiveness of one of said units comprises a control valve between the turbines of said units, said control valve being operable to vary the quantity of inlet air passing through the turbine of said one unit.

6. The pressure charging system of claim 1 wherein said means responsive to engine speed for controlling the effectiveness of one of said units comprises a control valve between the compressor of said units, said control valve being operable to vary the quantity of air passing through the compressor of said one unit.

7. The pressure charging system of claim 1 wherein said means responsive to engine speed for controlling the effectiveness of one of said units comprises a pair of control valve between said turbines and between said compressors, one of said valves being operable to vary the quantity of air passing through the turbine of said one unit and theother of said valves being operable to vary the quantity of air passing through the compressors of said one unit.

References Cited by the Examiner UNITED STATES PATENTS 1,856,024 4/1932 Buchi 60-13 1,860,449 5/1932 Buchi 60-13 2,173,595 9/1939 Schutte 60-13 2,306,277 12/1942 Oswald 60-13 2,380,777 7/1945 Moss 60-13 2,391,486 12/1945 Smith 230- X 2,585,968 2/1952 Schneider -13 2,780,053 2/1957 Cowland -1 60-13 MARK NEWMAN, Priniary Examiner.

KARL J. ALBRECHT, DONLEY J. STOCKING,

Examiners.

L. M. GOODRIDGE, Assistant Examiner.

Claims (1)

1. A PRESSURE CHARGING SYSTEM FOR AN INTERAL COMBUSTION ENGING OPERABLE BETWEEN A MINIMUM AND A MAXIMUM SPEED AND WHEREIN SAID CHARGING SYSTEM CAUSES SAID ENGING TO PROVIDE PREDETERMINED TORQUE AND HORSEPOWER OUTPUTS AT VARIOUS SPEEDS, SAID SYSTEM INCLUDING A PAIR OF EXHAUST TURBINE-COMPRESSOR UNITS CONNECTED IN OPERATIVE SERIES, ONE OF SAID UNITS PROVIDING A FIRST STAGE OF COMPRESSION OF INLET AIR TO SAID ENGINE AND THE OTHER OF SAID UNITS PROVIDING A SECOND STAGE OF COMPRESSION OF SAID INLET AIR PRIOR TO INTAKE BY THE ENGINE, MEANS RESPONSIVE TO ENGINE SPEED FOR CONTROLLING THE EFFECTIVENESS OF ONE OF SAID UNITS, SAID MEANS BEING OPERABLE ABOVE A PREDETERMINED PERCENT OF THE MAXIMUM ENGINE SPEED TO GRADUALLY REDUCE THE AMOUNT OF COMPRESSION OF SAID INLET AIR BY SAID ONE UNIT SO THAT BELOW SAID PREDETERMINED PERCENT OF SAID MAXIMUM ENGINE SPEED BOTH UNITS ARE FULLY EFFECTIVE TO PROVIDE MAXIMUM ENGINE TORQUE AND AT SPEEDS ABOVE SAID PREDETERMINED PERCENT OF SAID MAXIMUM ENGINE SPEED SAID FIRST UNIT DECREASES IN EFFECTIVENESS TO PROVIDE A RELATIVELY LARGE DECREASE IN ENGINE TORQUE AS THE ENGINE SPEED IN CREASES TO THE MAXIMUM SPEED.

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