Simulation Study On Jet Controlled Compression Ignition Of Diesel Engine With An Ignition-chamber

Diesel engine is one of the highest thermal efficiency power machinery equipment. However, the development of diesel engine is subject to the emission regulations. In order to comply with the limit of emission standard, various technologies are being developed. Among them, diesel premixed charge combustion has been able to achieve high thermal efficiency and clean combustion process with very low Nitrogen Oxides (NOx) emission. Diesel premixed charge combustion has become a hot topic of research in diesel engine combustion area. But combustion phase control is still a difficulty in diesel premixed charge combustion. In this paper research was done on an HLT132 diesel engine from Henan Diesel Engine Industry Co., Ltd (HND). An ignition-chamber on the diesel engine was designed and Jet Controlled Compression Ignition (JCCI) concept was applied to control ignition phase. Combustion and NOx emissions of the diesel engine were studied by simulation.The principle of JCCI was that the ignition of diesel pre-mixture in the main chamber was controlled by the high temperature flame and active radicals produced by gas mixture combustion in the ignition-chamber. Simulation was done to shed light on the JCCI process feature and guide the design and optimization of JCCI diesel engine. In this paper 3-D model of JCCI diesel engine was built by ProE, and AVL Fire was employed to analyze velocity distribution, equivalence distribution, temperature distribution, OH fraction distribution and NOx fraction distribution of JCCI process. Cylinder pressure, temperature and apparent heat release rate of JCCI diesel engine at four different load points were calculated as well.The calculation scheme of this paper was as follows.In order to ensure that diesel pre-mixture compression ignition could be avoided during compression stroke before top dead center (TDC), the geometric compression ratio of original diesel engine was lowered, and late intake valve closing technology to lower effective compression ratio of diesel engine was adopted in addition to reduce the max temperature in the main combustion chamber before the piston reaching TDC. In order to get relative homogeneous diesel pre-mixture, the strategy of early injection was adopted, and the fuel injection timing was 60℃CA BTDC. The ignition-chamber and Natural Gas (NG) supply component were designed. The NG mixture in the ignition chamber was ignited by spark discharge, and compression ignition of main combustion chamber mixture was triggered by the flame jet released from the ignition chamber.The simulation results showed that JCCI diesel engine could achieve low temperature combustion and reduced NOx emission, and the flame jet from the ignition-chamber could control the diesel pre-mixture ignition phase in the main combustion chamber effectively. There were two peaks in apparent heat release rate curve of JCCI diesel engine, which were generated respectively by the combustion in the ignition-chamber and the main combustion chamber. Combustion in the ignition-chamber enhanced the diesel pre-mixture temperature in the main combustion chamber. The ignition of diesel pre-mixture was directly triggered by the effect of jet disturbance and high temperature active radicals. At medium and high load, ignition phase could be controlled effectively by flame jet from ignition chamber with properly decreased effective compression ratio. At high load, the use of EGR could reduce burning rate and NOx emission of JCCI diesel engine any further.