Study Of Jet Controlled Compression Ignition Diesel Engine

With the basic characteristics of homogeneous premixed compression ignition, low temperature combustion, the new generation of internal combustion engine combustion theory realizes super-low NOx and PM emissions and high thermal efficiency simultaneously. But practical application of diesel premixed charge combustion is still blocked by three main problems, such as preparation of pre-mixture, combustion phase control and burning rate control, load limit and so on. Combustion phase control is the core problem, and the combustion phase control is the necessary premise to break through the load limit.In order to realize the purpose of combustion phase active control of premixed charge compression ignition, this paper used the new method of jet controlled compression ignition. Experimental engine was transformed from a single cylinder four-stroke air-cooled186F diesel engine. The original engine’s cylinder head was transformed, and original engine’s injector was replaced by a ignition chamber with auxiliary LPG supply equipment and ignition system. The direct injection diesel injector was arranged near the ignition chamber in the cylinder head, providing diesel pre-mixture. Compression ratio was lowered compared to the original engine and the shape of combustion chamber was changed, which guaranteed that diesel pre-mixture could not be compressed ignition, making it appropriate for JCCI combustion system. The modified engine was called JCCI engine.Based on engine experimental data, CFD numerical simulation software, AVL FIRE, was used to analyze the ignition process of jet controlled compression ignition (JCCI), and the effect of exhaust gas recirculation (EGR) rate and gasoline to dual fuel ratio was also analyzed. So that we can understand the characteristics of the JCCI further and lay the foundation for the next step of experiment and simulation study.The results showed that combustion products from ignition chamber was jetted into main combustion chamber, which promoted the flow inside the main combustion chamber and promoted the mixing process of diesel pre-mixture; diesel pre-mixture of main combustion chamber was ignited rapidly by the combustion products jetted from ignition chamber, thus precise ignition phasing control for diesel pre-mixture was realized consequently; combustion of diesel pre-mixture in main combustion chamber had the same characteristics of premixed charge multipoint ignition combustion and low temperature combustion; with the rising of EGR rate, ignition delay was slightly longer and NOx emissions decreased in main combustion chamber; with the rising of gasoline to dual fuel ratio, heat release rate and NOx emissions reduced, and flame propagation phenomena became more remarkable.