Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Patent
1995-02-02
1996-09-03
Nelli, Raymond A.
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
F02D 4100, F02M 2300, F02M 2500
Patent
active
055514111
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION AND PRIOR ART
The present invention relates to a system for optimizing operation of lean bum internal combustion (IC) engines for achieving the best trade-off between exhaust emissions, fuel economy, and engine power. The invention includes: 1) a strategy or process, 2) a general apparatus, and 3) a range of preferred embodiments for combining engine air, exhaust gas, and fuel in relation to engine intake air manifold absolute pressure (MAP) for achieving optimization of exhaust emissions, efficiency, and power. The invention preferably employs recently improved forms of very high power, very high energy (VHE) ignition disclosed in several prior patents and patent applications, including U.S. Pat. No. 4,677,960 on voltage doubling, U.S. Pat. No. 4,774,914 on piston firing, U.S. Pat. No. 4,841,925on enhanced toroidal gap ignition, U.S. patent application Ser. No. 07-350,945 (now abandoned) on high efficiency and high output coils, U.S. patent application Ser. No. 07-684595 now U.S. Pat. No. 5,131,376 on distributorless capacitive discharge ignition, and U.S. patent application Ser. No. 07-755,795 (now abandoned) on integrated converter ignition, which enhance the practicality of using the high air-fuel ratio and high exhaust dilution of the present invention for achieving said optimization. The present invention applies to all IC engines, and especially to four-stroke engines where NOx is relatively high and must be reduced and where fuel economy may be significantly improved over current approaches, i.e. the three-way catalyst approach and the lean bum approach.
In the three-way catalyst approach the air-fuel ratio is maintained at stoichiometry throughout the engine operating range by use of a lambda sensor. This results in relatively low NOx emissions but significantly compromised fuel economy (even when exhaust gas recirculation is employed via an EGR valve). In this approach engine-out (versus tailpipe) emissions are high, so that the system is not stable against malfunctions or even small departures from stoichiometric operation.
In modern commercial lean bum approaches the engine is operated at high air-fuel ratios (excess air) which improves fuel economy but does not reduce NOx to the required level, especially at high loads. Furthermore, modern commercial lean bum engines depend entirely on sophisticated engine design, i.e. intake air swirl and air tumble motion, to provide the very lean air-fuel ratio capabiity, and are thus not amenable for retrofit onto older cars (as in the case of the present invention). When further NOx reduction is required, they revert to the use of the conventional three-way catalyst approach with EGR, as described in SAE paper 920455, February 1992, by Honda Motors. Furthermore, the EGR valve adds the exhaust on the low pressure side of the throttle by means of engine vacuum and does not attempt to add the exhaust gas to a lean mixture in an optimized way as disclosed in the present invention.
Unconventional ways of operating lean burn engines, and advantages of doing so, are disclosed in my prior patent applications: U.S. patent application Ser. No. 07-685,057 (now U.S. Pat. No. 5,211,147) where reverse stratification is disclosed for reducing NOx, U.S. patent application Ser. No. 07/698,967 (now abandoned) where boosting of the intake air is disclosed for reducing NOx at high pressures, and U.S. patent applications 07/765,896 (now abandoned) and 07/854,074 (now abandoned) where methods of using exhaust gas in a lean burn mode are disclosed for reducing NOx emissions over a wide range of conditions.
General issues of engine emissions and fuel economy are discussed in many texts, and the following are a sampling of texts which discuss these issues in some degree: "Internal Combustion Engines and Air Pollution" by E. F. Obert (Intext Educational Publishers 1973); "Internal Combustion Engine Fundamentals" by John B. Heywood (McGraw-Hill Book Company, 1988); and the manual "Bosch Automotive Electric/Electronic Systems"(Robert Bosch GmbH 1988).
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Cohen Jerry
Combustion Electromagnetics Inc.
Nelli Raymond A.
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