Design Of Electronic Control System For Lean Burn Gasoline Engine And Study On The NOx Emission Control

It is necessary to apply electronic control technology to the SI engine in order to save energy and reduce the exhaust emission. The new technology of quasi-homogeneous lean combustion, based on the Twice Fuel Injection, can use the advantage of lean burn fully, and thus help to reduce the fuel consumption and emission of the engine. However, higher requirements are raised for the engine control system, and the NOx emission is a key problem needed to solve.The paper analyzes the function of stratification to realize lean combustion at first. Based on the analysis of lean combustion principle, the quasi-homogeneous lean combustion is realized using Twice Fuel Injection. The influence of Twice Fuel Injection on lean burn limit is analyzed experimentally. The results show that Twice Fuel Injection is effective to realize lean combustion.As for the reduction of NOx in lean burn engine, several controlling ways existed nowadays are discussed, and a method to reduce NOx emission using three-way catalyst is proposed. The theoretical analysis shows that it is possible. Primary experiment is made to test it. A method to measure and control the wide range of air fuel ratio by using the traditional on-off oxygen sensor is developed. Combined with three-way catalyst, it maybe a good method to realize lean combustion, which fits our national conditions. For meeting the demand of realizing lean combustion on gasoline engine in the experiment, a set of lean burn electrical control unit is developed with enough function. Its hardware and software is designed. Using the unit, the air fuel ratio control test of lean burn engine is made on Toyota 8A engine and YH465 engine. The experiments to control NOx emission using storage-reduction catalyst and three-way catalyst are also performed. It shows that using fuzzy PI control method, the range of air fuel ratio of transit process can be controlled into 0.5 unit. The control scheme of verification and iteration is feasible to control the transform process of NOx storage-reduction catalyst. The method to reduce NOx emission in lean-burn SI engine using three-way catalyst maybe practicable. The developed electrical control unit works steadily and durably and it can meet the demand of experimental use in the research.