Operation of forced induction internal combustion engines

Details Operation of forced induction internal combustion engines Operation of forced induction internal combustion engines

1999-05-13

2001-09-04

Denion, Thomas (Department: 3748)

Power plants

Fluid motor means driven by waste heat or by exhaust energy...

With supercharging means for engine

C060S606000, C060S620000, C123S556000, C277S377000, C277S377000

Reexamination Certificate

active

06282898

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the operation of forced induction (for example supercharged or turbocharged) internal combustion engines of the spark ignition type.
BACKGROUND OF THE INVENTION
It has long been known that the specific power output of internal combustion engines can be increased by supplying pressurized air to the engine inlet port such that a larger charge of air can be inducted into the combustion chamber or chambers of the engine during each cycle. In a spark ignition engine it is a fuel/air mixture that is induced, whereas in a compression ignition engine it is air that is induced, with fuel being injected directly into the compressed charge.
The application of forced induction to spark ignition engine presents various problems, one of which is that of pre-ignition of the air/fuel charge prior to the normal ignition timing. Such pre-ignition (or knocking) degrades engine performance and applies damaging shock forces to the engine; it must be avoided during normal engine operation. The necessity to avoid pre-ignition limits the compression ratio that can be utilized in spark ignition engines, it may require the use of high octane fuels which delay the inception of pre-ignition, and it has limited the circumstances under which forced induction can be used effectively, as well as necessitating the use of intercoolers to cool the compressed air before it is applied to the engine. In typical applications, this has entailed that forced induction can be applied effectively only under essentially full throttle conditions at high engine speeds. Under such conditions it is undoubtedly effective in increasing specific power output, but in most automotive applications, high speed full throttle operation occurs for only a very small proportion of the total operating time of the engine. It has been necessary to avoid conditions under which excessive temperatures and pressures occur with the combustion chamber(s) of the engine during the compression stroke since these tend to result in pre-ignition. One approach to this problem has involved so-called lean-burn technology, as disclosed for example in U.S. Pat. No. 5,135,235 (Yanagihara). In such an engine system, the boost applied by the forced induction system is also related to the air/fuel ratio of the mixture applied to the engine, with this ratio increasing with increasing boost of the intake air. This tends to reduce the tendency to pre-ignition, while the increased volume of air passed through the system assists somewhat in reducing engine temperatures, and somewhat extends the range over which some boost can be effectively applied.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a forced induction internal combustion engine in which a substantial increase in operating efficiency can be achieved over much of the engine operating range, while avoiding pre-ignition.
My invention is based on the discovery that, provided that combustion chamber pressure is kept high enough and temperature is kept low enough during the pre-ignition period (that period at the end of the induction stroke during which pre-ignition typically occurs), pre-ignition can be avoided. This can permit a large increase in volumetric efficiency of the engine under part throttle conditions which is accompanied by a notable increase in overall efficiency. This greatly increases efficiency in converting the thermal energy of the fuel into mechanical energy, and conversely correspondingly reduces the waste heat generated by the engine. Because the blower or other compressor used to boost the engine is effective whenever the engine is producing significant power, it is more effective, assuming that an exhaust driven turbocharger is used, in recovering energy from the exhaust gases, and the high effective pressures in the engine mean that any exhaust back-pressure from the turbine of the turbocharger should not be a significant problem.
Under conditions, other than idle or closed throttle, when the engine is required to develop significant power, sufficient pressure boost is applied to the intake air to ensure that firstly a sufficient pressure drop occurs across the combination of a throttle valve or valves and an intake valve or valves downstream of an air compressor to provide substantial cooling of the air, and secondly to ensure that, even after this pressure drop, an effective compression ratio of at least 10 relative to atmospheric pressure is achieved. The pre-expansion of the air on its way into the combustion chamber during the induction stroke provides sufficient cooling to prevent excessive temperatures being generated during the subsequent compression stroke, and the consistently high degree of expansion within the combustion chamber also keeps down combustion chamber and exhaust temperatures, further diminishing the likelihood of pre-ignition. It will be appreciated from the foregoing that the forced induction system, typically an exhaust driven turbocharger, needs to be able to maintain a substantial degree of boost, typically at least 1.5 atmospheres, over a wide range inlet and exhaust gas flow rates.
The system does result in the development of increased combustion pressures which have been found in tests to result in increased stresses on piston rings of engines so operated, which may result in failure. Accordingly, it is believed that it will usually be necessary to provide a top piston ring of modified construction and/or location so as better to resist these forces. Good results have been obtained with flexible composite ceramic rings.
According to the invention, there is provided a spark ignition internal combustion engine having at least one combustion chamber and an operating cycle with induction, compression, power and exhaust phases, said engine having a forced induction system including an intake air compressor supplying intake air to the engine through an inlet tract comprising at least one throttle, at least one intake port and means to introduce metered quantities of fuel into the inlet tract; wherein the compressor boosts intake air pressure by more than one atmosphere throughout that portion of the operating range of the engine which corresponds to significant opening of the at least one throttle, the at least one throttle and at least one intake port conjointly providing sufficient throttling of the intake air flow over said portion of the operating range such as to provide substantially adiabatic expansion of the air delivered by the compressor through the inlet tract, while causing each combustion chamber to be charged with sufficient air/fuel mixture during the induction phase that the pressure in each combustion chamber at the end of the compression phase is at least ten atmospheres over said portion of the operating range, and the combined temperature and pressure conditions in the combustion chamber during the compression phase remain outside those giving rise to pre-ignition, the means to introduce metered quantities of fuel into the inlet tract being calibrated to provide substantially stoichiometric quantities of fuel relative to the air passing through the tract over said portion of the operating range.
The invention is described further below with reference to the exemplary embodiments.


REFERENCES:
patent: 3568650 (1971-03-01), Albrich
patent: 3697091 (1972-10-01), Prasse et al.
patent: 3731941 (1973-05-01), Mori et al.
patent: 3794334 (1974-02-01), Prasse et al.
patent: 3932228 (1976-01-01), Sugiyama et al.
patent: 4125999 (1978-11-01), Melchior
patent: 4248198 (1981-02-01), Deutschmann et al.
patent: 4251599 (1981-02-01), McCormick
patent: 4284055 (1981-08-01), Wakeman
patent: 4400944 (1983-08-01), Iwamoto et al.
patent: 4417560 (1983-11-01), Frank
patent: 4445336 (1984-05-01), Inoue
patent: 4489560 (1984-12-01), Fawcett et al.
patent: 4598675 (1986-07-01), Long
patent: 4663938 (1987-05-01), Colgate
patent: 4664021 (1987-05-01), Ruddy
patent: 4840164 (1989-06-01), Parsons
patent: 4916903 (1990-04-01), Holmer
patent: 5125235 (1992-06-01), Yanagihara et al.
patent:

Affiliated with

Also associated with

Rating

Operation of forced induction internal combustion engines does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Operation of forced induction internal combustion engines, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Operation of forced induction internal combustion engines will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2524847