Power plants – Internal combustion engine with treatment or handling of... – Methods
Patent
1996-09-10
1998-11-17
MaMahon, Marguerite
Power plants
Internal combustion engine with treatment or handling of...
Methods
F01N 502
Patent
active
058361529
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to a method for reducing exhaust gas emissions of an internal combustion engine for automotive vehicles with an exhaust gas catalytic converter and an exhaust gas system for such engines.
At cold start of an internal combustion engine substantial exhaust gas emissions excape into the ambient air within the first minute even when an exhaust gas catalytic converter is used. The detrimental emissions, in particular HC, CO and NO.sub.x, are due to incomplete combustion and high friction at the still cold engine masses as well to bad, instable processing of the fuel air mixture which is compensated by excess fuel. Furthermore during acceleration phases very distinct emission maxima directly related to actuation of gear mechanisms are observed, which inherently results in rapid load and speed changes. Because during these phases mixture formation is uncontrolled, dynamic mixture discrepancies between fuel delivery and air flow rates result, and the temperatures in the combustion chamber, in particular the temperature gradients in the combustion chamber walls, are subject to substantial transient changes. As a result maximal emissions of HC, NO.sub.x and CO will occur within seconds.
For example maximal emission of HC occurs at initial loading of the engine, maximal emission of NO.sub.x occurs when the gear change speed at full load has been reached, and during gear change maximal emission of CO occurs at an overrich fuel-air-mixture condition, and maximal emission of NO.sub.x occurs at a lean mixture condition. At the same time the catalytic converter is still old and accordingly ineffective so that noxious exhaust gases will escape without being processed until the catalytic converter will have been sufficiently heated.
With Diesel engines additionally substantial smoke, noise and smell will develop at the start and at acceleration from the start.
High quality catalytic converters are sufficiently effective about 50 sec after starting of the engine, while the first HC emission maximum occurs already 20 sec after starting of the engine in the CVS test when the automotive vehicle starts to move and accordingly the engine is accelerated at high load.
There have been attempts to advance the time when the catalytic converter becomes effective by electrical heating of the catalytic converter. Such electrical heating is expensive, cumbersome, results in substantial electrical energy consumption and has no influence on the generation of the emissions within the engine.
It is an object of the invention to favourably influence, in a cost effective manner, the heating of the emission relevant motor parts, in particular the combustion chamber walls, and the coated catalytic surfaces of the catalytic converter, at least a partial surface preferably at the inlet of the catalytic converter, such that the exhaust gas emissions of the engine are reduced and the catalytic converter operates effectively already when the engine is accelerated to start to move the vehicle. In order to achieve this goal, the temperatures of the gas in the combustion engine and in the catalytic converter shall be increased very rapidly to a level as high as possible. A further object is to avoid maximal emissions due to rapid load and speed changes and due to instable mixture formation.
The solution of this object consists in that there will be provided, at least at cold start, a ram pressure condition in the exhaust gas conduit to generate a pressure increase of more than 0.5 bar at the exhaust gas outlet of the engine, and by additionally loading the engine at rapid load and speed changes.
Due to the ram pressure condition density and temperature of the exhaust gases are increased and the engine is forced to process more fuel. Due to the compressed hot exhaust gases heat transfer at the walls of the engine combustion chambers and exhaust gas conduit and at the active surfaces of the catalytic converter is improved.
Tests have shown that a ram pressure of up to 0.5 bar will result in an only slight improvem
REFERENCES:
patent: 4929581 (1990-05-01), Steinwandel et al.
patent: 5125231 (1992-06-01), Patil et al.
patent: 5517820 (1996-05-01), Kuroda et al.
patent: 5613359 (1997-03-01), Zahn et al.
patent: 5765368 (1998-06-01), Matsumoto et al.
MaMahon Marguerite
Schatz Thermo Gastech GmbH
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