Combustion And Emission Performance Optimization For Low-Emission Small Non-Road SI Engine Based On The Interior Purification

The non-road SI engine industry in China has achieved rapidly development in the last ten years and China has become the world major producers and exporters of the non-road SI engine. But the use of the interior purification technology in the domestic non-road SI engine can hardly meet the US EPA phase-Ⅲ emission standard, and it has become one of the technical bottleneck in the development of the industry. Some external purification technologies can make the whole machine emission meet EPA emission regulations, but it may increase the engine cost, and reduce the engine safety. Therefore, developing a high performance, low emission non-road SI engine product by optimizing the air intake system, fuel supply system and combustion process would make an important practical value.188F gasoline engine which has a higher market share is the research prototype, and the aim of the research is to meet the most stringent US EPA phase-Ⅲ emission standard. Combination methods of simulation analysis and experimental method were used on the optimization of intake and exhaust system, fuel supply and combustion process research. The structural characteristics and the cross-sectional area change of the intake and exhaust airway were analyzed, the best optimized scheme for the intake and exhaust system with the technology meeting the die-casting technology was got by the steady flow test bench. Compared with the original engine, the intake and exhaust airway flow coefficient increased 20.3% and 16.0% respectively; with the optimized design for intake flow path, the intake flow was 4.0% higher. The engine bench test result for the optimized intake and exhaust systems shows: when the engine was working at the full load, the torque increased by 1.87 N·m, and the specific fuel consumption decreased by 8.1g/(kW·h), and the HC and CO emission at different load reduced, while NOX emissions slight increased. The effect of gasoline engine power, economy, and emissions changed with the different mixture concentration and the advanced ignition at different loads. And these results were simulated by Ricardo-Wave software. Quantify the relationship of the engine performance change with the different mixture concentration and the advanced ignition by engine bench test. A low-emission high performance non-road SI engine with ideal air ratio characteristics and ideal ignition timing characteristics were got according to regulatory emission limits. The brake specific emission of CO, HC+ NOX of the 188 F gasoline engine were 347.5g/(kW·h) and 6.91g/(kW·h). At the same time, optimal mixing excess air ratio programs were determined. The brake specific emission of HC+NOX dropped to 6.23g/(kW·h) with timing the ignition advanced angle. After the deterioration test, the brake specific emission of CO and HC+NOX were 312.5g/(kW·h) and 7.10g/(kW·h), it is far below the US EPA Phase Ⅲ emission limits. Research for the development of low-emission high-performance non-road SI engine can provides a referenced technical route for other non-road SI engine in domestic.