Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Patent
1997-11-18
1999-12-21
Koczo, Michael
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
F02M 2507
Patent
active
060033169
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an internal combustion engine according to the preamble of claim 1.
BACKGROUND OF THE INVENTION
Such an internal combustion engine is disclosed in German Offenlegungsschrift 4,319,380 and can be used either for a diesel or an otto engine.
Exhaust-gas recirculation (EGR) is a known technique for reducing, in particular, the NO.sub.x emission of combustion engines. In the case of EGR, some of the exhaust gases are fed back to the inlet of the engine. Especially in the case of turbo-charged engines (engines provided with turbo-compressor) and turbo-charged engines with intermediate cooling (or intercooling; cooling of the compressed inlet air), this can be done in a number of different ways. The most well known are: the compressor, and
An advantage of design b) is that no contamination can occur of the compressor and the intercooler optionally connected downstream thereof.
A problem in the case of exhaust-gas recirculation is the metering of the quantity of exhaust gas in the inlet duct. This determines the emission of the respective internal combustion engine. In order to limit the NO.sub.x discharge, sufficient exhaust gas has to be recirculated. On the other hand, an unduly large addition has the consequence that the power of the internal combustion engine is adversely affected if this is at the expense of the quantity of air. With an excess EGR flow, the particle emission also increases. In addition, a pump loss is produced by the implementation of an EGR flow by the bleed points, which adversely affects the efficiency.
As a result of the efficiency loss, there are still hardly any EGR systems at present which can effect EGR in the high/maximum load range. To generate EGR in this range, use is fairly often made of a back-pressure valve in the exhaust system. In general, this results in a significant increase in fuel consumption.
EGR systems are in fact frequently used in the lighter diesel engines. As a result of the official exhaust-gas emission test procedures for this category of engines, where the stress is on low and moderate engine load, it is possible to make do with EGR at low and moderate engine load. In this case, `replacement` EGR is also involved; some of the inlet air is replaced by EGR gas. In the case of low/moderate load, this generally produces no substantial deterioration in the performance because, even after replacement, an adequate excess of air is still present. In these systems, it is generally possible to make do with fitting a simple throttle valve (between compressor and EGR introduction location) in order to effect the required EGR flow.
In the design according to German Offenlegungsschrift 4,319,380, a regulable back-pressure valve is sited downstream of the turbine. As this back-pressure valve is further closed, the back-pressure upstream of the turbine will also increase, as a result of which (more) exhaust gas flows towards the inlet via the bleed. Since turbine work and compressor work do not change or hardly change as a result of this design and in view of the usual compressor characteristic, the (fresh) air flow through the engine will drop. This is `replacement` EGR. As a result of the consequently lower excess of air, the efficiency of the engine will drop and the smoke emission will increase.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an internal combustion engine which has a high efficiency and in which a complicated regulating system is unnecessary for controlling the quantity of recirculated gas in the inlet duct.
This object is achieved in a combustion engine of the above-mentioned type in that the turbine is designed as a turbine with variable geometry. It is so designed that, when the exhaust back-pressure increases as a result, the work performed by the turbine and compressor increases. The consequence thereof is that the compressor rotary speed and the inlet manifold pressure rise, as a result of which the decrease in the air flow as a consequence of the space occupied by the EGR gas is mini
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patent: 4426848 (1984-01-01), Stachowicz
patent: 5778674 (1998-07-01), Kimura
Patent Abstracts of Japan, vol. 3, No. 24, Feb. 27, 1979.
Patent Abstracts of Japan, vol. 18, No. 660, Dec. 14, 1994.
Baert Rik Silveer Geert
Beckman Derek Edward
Dekker Hendrik Jan
Sturm Willem Lein
Verbeek Rudolfus Petrus
Koczo Michael
Nederlandse Organisatie voor Toegepast-Natuurwetenschappelijk On
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