Experimental Research On Influence Of Combustion Chamber Shape On Performance Of2.0L HPCR Diesel Engine

With the global warming becoming a serious problem, diesel engine has gotmore attention for its low CO₂emissions, and vehicle diesel engine is a majortrend of the development. With increasingly stringent energy conservation andemissions regulations, people raise a higher demand on diesel engineemissions. This is bound to proceed from improving combustion conditions, sodiesel engine injection system with electronic control and high-pressure is putinto use. The necking-DI chamber became more popular. In order to makemore effectively use of the structural characteristics and flow characteristics ofthe necking combustion chamber, It’ s necessary to study the optimization ofthe Necking-ratio and the structure of the combustion chamber shape.The combustion of diesel engine is mainly composed of premixed combustionand diffusion combustion. The premixed combustion rate should be limited toreduce NOx emission, but the diffusion combustion must be boosted by theairflow movement. In this paper, based on2type of HPCR Neckingcombustion chamber, the writer analyses the flow intensity maintenance of the2chamber and designs5optimized plans to make the elect of the chambers.With the help of FIRE software, simulates the diesel engine combustionchambers of the7types, analyses the influence of combustion chamber shapeon characteristics of the flow in different speed and load, and defines theconcept of flow intensity maintenance to calculate the squeeze intensity andswirl intensity maintenance in the above condition. simulates and analyses theequivalence-ratio field and temperature field with spray condition. Draw theheat release rate curve to compare, thus to analyses the mixture formationcharacteristics of necking-DI chamber. Then, choose4plans to manufacture the test pistons and do the comparative experiments. Draw the indicatordiagrams and heat release rate curves, choose the optimum plan bycomparing the actual performance. Thereby to optimize the combustionchamber, and come up with the following conclusions:1. From the experimental results, the performance of the optimized chamberis the best one. This is according to the theoretical results, which indicatesthat the design method is reasonable.2. From the performance curves, we can see that the improvement of thechamber shape can control the combustion process, thus to optimize theengine. The slope of the center boss in combustion chamber has a greatinfluence on flow movement, the concave slope is the best shape, it canhelp to form squeeze vortex; The center boss without platform can help toreduce the flow movement dead zone effectively; The necking-ratio has agreat impact on squeeze intensity maintenance, within a certain range,small necking-ratio helps to enhance the squeeze intensity and itsmaintenance. In this experiment, the suitable ratio is0.89; Squeezeintensity is mainly dominated by compression ratio, the small changes ofstructural parameters have little effect on it.