GB2490106A

GB2490106A - Forced induction for internal combustion engines

Info

Publication number: GB2490106A
Application number: GB1106260.1A
Authority: GB
Inventors: Scott Bredda; Roger Valler
Original assignee: GE Precision Engineering Ltd
Current assignee: GE Precision Engineering Ltd
Priority date: 2011-04-13
Filing date: 2011-04-13
Publication date: 2012-10-24
Also published as: GB201106260D0

Abstract

A forced induction system for an internal combustion engine 60, comprising a piston and cylinder air compressor 40. Preferably the air compressor is driven directly from the engine at a fixed ratio and the air compressor can be partially or completely unloaded using a disengageable clutch, where dead volume unloading is possible. The speed at which the compressor is driven may vary relative to the speed of the engine, the compressor may be driveable by an electric motor or by a continuously variable transmission. The system may also comprise a turbocharger and at least one control valve provided after the turbocharger. A method of supercharging an internal combustion engine is also claimed.

Description

I

Forced Induction for 1.0. Engines

Description of invention

This invention relates to internal combustion (IC) engines, and more particularly to a method of and system for providing for forced induction of air or an air/fuel mixture into an engine.

Current trends in engine design, particularly for motor vehicles, are focused on downsizing. The main reason for downsizing is emissions legislation and to some extent social perception and awareness for the environment, as well as rising fuel costs. The benefit is perceived as being an improvement in fuel economy and the associated reduction in CO2 emissions. The obvious problem of downsizing or replacing a large capacity engine with a small one is the loss of power, which typically can be overcome by use of forced induction.

Forced induction is a well-known concept, with two main technologies used to achieve the effect; so-called turbocharging and supercharging. ln both, an engine is supercharged in that the mass air flow rate into the engine is increased, above that which is achievable by natural aspiration, by use of what effectively is an air pump to provide air for combustion at a raised pressure.

The term supercharger is generally reserved for a device driven directly mechanically, or possibly indirectly e.g. electrically from the engine, thereby making use of a small proportion of the engine's brake power. Turbochargers utilise an exhaust gas-driven turbine to power a centrifugal air compressor.

However, each of these has significant disadvantages.

Turbochargers usually require an oil feed and drain, and are usually made of exotic materials such as nickel alloys, ceramics, titanium, and high-grade stainless steels. Due to the high speed at which they run, turbochargers must be made to a precise tolerance, which results in increased production costs.

Similarly, superchargers often contain exotic materials and are built to a precise tolerance. There are different types of supercharger, principally positive displacement types or dynamic types, but there are disadvantages assodated with both.

The focus of the invention is to provide a forced induction system which addresses the disadvantages of known turbochargers and superchargers.

According to the first aspect of the invention, we provide a forced induction system for an internal combustion engine comprising a piston and cylinder air compressor.

Piston and cylinder air compressors are well known, comprising a structure affording one or more cylinders in which a respective piston is reciprocable, driven from a crankshaft by way of a respective connecting rod. The air compressor operates on a 2strokeJ cycle, with air being drawn into the or each cylinder on an induction stroke then compressed and delivered therefrom on a compression stroke. The flow of the air into and out of the cylinder is controlled by valves which may be of the automatically-operating type responsive to a pressure differential across the valve, e.g. reed valves.

Such air compressors have the advantages of being relatively simple and efficient, delivering air at a relatively low temperature, readily achieving pressure and volume outputs suitable for forced induction in engines, and not requiring exotic materials for their construction.

The air compressor may have a chamber which is in fluid communication with the cylinder, with a valve provided to control flow between the two. In an energy-saving mode, it would be possible to open the chamber during the compression stroke so that compressed air enters, and close the valve so that the compressed air is stored. The compressed air may then be released during the induction stroke, which would force piston down and thus recover some of the compression energy. Such an arrangement is known as "dead volume" unloading.

The air compressor may be designed in such a way as to not require lubrication, e.g. by utilising anti-friction coatings or materials on cooperating sliding surfaces such as those of the piston(s) and cylinder(s), and rolling-element bearings (which may be the sealed type incorporating a lubricant supply) for rotating parts.

The air compressor may be driven directly from the engine at a fixed drive ratio.

The air compressor may be provided by a method of unloading the compressor when it is not required.

The unloading method may be dead volume unloading.

The unloading method may be through the use of a clutch system, and/or the air compressor may be driven at a rate variable relative to the rate of the engine. Such driving may be achieved directly from the engine by use of a variable-ratio transmission, e.g. a continuously variable transmission, or indirectly from the engine by use of an electric or other variable-speed motor to drive the air compressor.

The air compressor may be driven by an electric motor.

The air compressor may be used in addition to another forced induction device.

The additional forced induction device may be a turbocharger.

There may be at least one control valve after the turbocharger.

The invention will now be described by way of example with reference to the accompanying drawings, Figures 1 and 2 thereof being schematic depictions of two forced induction engine arrangements according to the invention.

Referring now to figure 1, a piston and cylinder air compressor unit is indicated generally at 40. Atmospheric air A enters through a passage 10 and is drawn past a reed valve 12 into a cylinder space 14, (which is defined by a cylinder wall 16), by the downward stroke of a piston 18. Piston 18 is connected to a crankshaft 48 by a connecting rod 20 which is mounted on a connecting rod journal 49, and as the crankshaft 48 rotates and the connecting rod journal 49 reaches its bottom dead centre (B DC) position, the piston finishes its downward stroke and the reed valve 12 closes. The piston 18 begins its upward stroke as the crankshaft rotates further, and the air inside chamber 14 is compressed. As the air is compressed it increases in pressure, and when the pressure passes the activation threshold of a reed valve 22 the compressed air is released into a chamber 24, which is in fluid communication with an outlet passage 42.

The timing of a second piston 34 is such that as piston 18 is on its upward stroke, the piston 34 is on its downward stroke. Piston 34 is mounted in a cylinder space 30 defined by a cylinder wall 32, and it is connected to crankshaft 48 by a connecting rod 36 which is mounted on a connecting rod journal 51, and reciprocates relative to the crankshaft 48 in the same way that piston 18 does. Atmospheric air A is drawn from a chamber 26 (which is in fluid communication with passage 10) past a reed valve 28 during the downward stroke of piston 34, and is compressed during the upward stroke of piston 34. When the pressure of the compressed air passes the activation threshold of reed valve 38, the reed valve 38 opens and the compressed air passes out into passage 42.

The compressed air released into passage 42 from cylinder spaces 14 and 30 passes through an intercooler 50, into a passage 52, which joins an inlet manifold 54 of an engine 60.

It is envisaged that the air compressor in the invention could have one or more cylinders in any convenient configuration, and that the air may be compressed more than once, e.g. in a "compound" arrangement where the compressed air from one cylinder enters another cylinder for further compression.

The engine indicated generally at 60 is an inline three cylinder four-stroke engine, and draws air in from the inlet manifold 54 through inlet runners 56 into three cylinder volumes indicated at 61. The fuel may be injected towards the end of the inlet runners 56 in a £port injection format, or it may be directly injected into cylinder volumes 61. The combustion of the air-fuel mixture results in reciprocation of the pistons in the engine in the known manner of a four-stroke engine operating according to the Otto cycle. This results in both the rotational motion of a crankshaft 58, and the production of exhaust gas, which is released through exhaust runners 62. These runners join an exhaust manifold 64, which provide fluid communication to an appropriate exhaust outlet.

The rotational motion of the engine 60 drives the air compressor either directly or indirectly; for example there could be a belt extending from an engine crankshaft pulley 55 to an air compressor crankshaft pulley 45. Alternatively, the engine crankshaft pulley 55 may be linked to a generator that charges a battery, and the stored energy is used to drive an electric motor which is driveably linked to air compressor crankshaft 48. There is also the possibility that the engine 60 may be directly linked to air compressor crankshaft pulley at a variable ratio, through the use of a variable ratio belt drive, for

example.

Referring now to flgure 2, a similar system is shown, with the addition of a turbocharger generally indicated at 90. The parts which are also shown in figure 1 are shown with the corresponding reference number.

The turbocharger 90 operates in a manner well-known to those skilled in the art; the exhaust gas from the exhaust manifold 64 passes through a passage 66 and turns an impeflor in the exhaust side 70, and exits through outlet 71, indicated by arrow B. A wastegate valve 68 can allow exhaust gases to bypass the exhaust impellor to avoid it turning faster than is required, for example when a predetermined inlet manifold pressure has been reached, and the wastegate valve 68 may be controlled mechanically or electronically. The turning motion of the exhaust impellor is transmitted by a driveshaft 72 to the inlet impellor housed inside inlet side 75, and air A is drawn into the inlet system through 74, and propelled along passage 76 through intercooler 78 and into passage 80.

The pressurised air can then flow though control valve 82 and into the air compressor, or along passage 84 and through valve 86 into the passage 88, and from there into the inlet manifold 54.

The control of the three valves 68, 82, and 86 allows a number of modes of operation to be provided. If the turbocharger 90 is not spinning at a speed sufficient to significantly compress the air, for example when engine 60 is turning slowly and producing very little exhaust gas, valve 82 could be fully opened and valve 86 fully closed to ensure all inlet air is compressed.

Alternatively, if the turbocharger 90 is producing a significant volume of compressed air, then it is possible to close valve 82 and open valve 86 so the air is bypassing the air compressor 40. Another possibility is using the compressed air from the turbocharger 90 and then compressing it further by opening valve 82 and closing valve 86; it would be possible to control the total compression of the system by controlling the turbocharger compression using valve 68, the air compressor bypass using valves 82 and 86, and the rate of drive When used in this specification and claims, the terms comprises' and comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the foflowing claims, or the accompanying drawings, expressed in their specific forms or in terms of a 1 5 means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

Claims 1. A forced nduction system for an internal combustion engine, comprising a piston and cylinder air compressor.
2. A forced induction system according to claim 1 wherein the air compressor is arranged to be driven directly from the engine at a fixed ratio.
3. A forced induction system according to claim 2 including a means for partially or completely unloading the air compressor as required.
4. A forced induction system according to claim 3 wherein the unloading means provides for dead volume unloading.
5. A forced induction system according to claim 3 wherein the means for unloading the air compressor includes a disengageable clutch.
6. A forced induction system according to claim I wherein the air compressor is drivable at a speed which varies relative to the speed of the engine.
7. A forced induction system according to claim 6 wherein the air compressor is drivable by an electric motor.
8. A forced induction system according to claim 6 wherein the air compressor is drivable by a continuously variable transmission.
9. A forced induction system according to any of the preceding claims which has an additional forced induction device.
10. A forced induction system according to claim 9 wherein the additional forced induction device is a turbocharger.
11 A forced induction system according to claim 10 comprising at least one control valve provided after the turbocharger.
12. A forced induction system substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
13. An internal combustion engine having a forced induction system according to any one of the preceding claims.
14. A method of supercharging an internal combustion engine, comprising using a piston and cylinder air compressor to supply combustion air to the engine.
15. A method of supercharging an internal combustion engine according to claim 14 wherein the air compressor is arranged to be driven directly from the engine at a fixed ratio.
16. A method of supercharging an internal combustion engine according to claim 15 including a means for partially or completely unloading the air compressor as required.
17. A method of supercharging an internal combustion engine according to claim 16 wherein the unloading means provides for dead volume unloading.
18. A method of supercharging an internal combustion engine according to claim 16 wherein the means for unloading the air compressor includes a disengageable clutch.
19. A method of supercharging an internal combustion engine according to claim 14 wherein the air compressor is drivable at a speed which varies relative to the speed of the engine.
20. A method of supercharging an internal combustion engine according to claim 19 wherein the air compressor is drivable by an electric motor.
21 A method of supercharging an internal combustion engine according to claim 19 wherein the air compressor is drivable by a continuously variable transmission.
22. A method of supercharging an internal combustion engine according to and of the preceding claims which has an additional forced induction device.
23. A method of supercharging an internal combustion engine according to claim 22 wherein the additional forced induction device is a turbocharger.
24. A method of supercharging an internal combustion engine according to claim 23 comprising at least one control valve provided after the turbocharger.
25. A method of supercharging an internal combustion engine substantially as hereinbef ore described with reference to and as shown in the accompanying drawings.
26. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.