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Three-dimensional Transient Numerical Study on the Flow Character in Cylinder of Engine for Car

Author: ZhangZhiRong
Tutor: RanJingZuo
School: Chongqing University
Course: Thermal Power Engineering
Keywords: Engine Intake process Transient Numerical calculation
CLC: U464
Type: Master's thesis
Year: 2005
Downloads: 275
Quote: 2
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Abstract


With the energy crisis and environmental problems growing countries have developed efficient low-pollution car engine running as one of the key development projects. The engine intake process is the key of the engine cycle. The state of the intake stroke cylinder of the flow field formed directly affect the flame propagation speed in the engine combustion process, the combustion stability and combustion is completely, and thus also affect the power of the engine. At home and abroad in recent years, the subject ongoing in-depth research, especially on how to achieve the numerical study of engine cylinder flow transient has been a research focus of national researchers. Transient numerical computation engine consistent with the actual work process more intuitive understanding of the state of the flow field, to be able to test the engine intake design is reasonable, formed in the cylinder in the engine intake process can also according to the needs of the engine performance by changing reasonable structure design and organization of the intake system airflow. The dynamic meshing technologies based on the first study to achieve the numerical calculation of the engine intake process transient based control volume method combined dynamic meshing technology, and on this basis to solve the mock objects in multiple mobile borders. And intake process for the the Volkswagen Bora the 1.9TDI type of engine, a three-dimensional transient numerical study. With different inlet shapes, different locations, different speeds and different single inlet engine compression ratio of the engine and dual inlet intake process to do a transient numerical study, analysis of the velocity field, the pressure in the intake process the variation characteristic of the field, turbulence intensity, the study analyzes the parameters of the flow coefficient and the charging efficiency, characterized by an intake system characteristics. The study results show that in the early stages of the air intake inlet shape and location of the distribution of the cylinder fluid velocity field distribution, pressure, turbulence intensity and impact; the late intake process, the state of the cylinder flow field with the piston under shift, the flow is no longer a pure sense of the swirl and tumble, but the combination of these two flow. Further, the intake system of the pneumatic efficiency and turbulence intensity mutual restraint, the proportional relationship of the engine speed and turbulence intensity, and the intake air speed. Within an engine cylinder of the higher speed movement of strong eddy current is generated, and also formation of a certain pressure loss, the low speed operation is likely to cause the cylinder intake air amount is insufficient, power weakened; tangential inlet engine cylinder formation of a vortex and roll stream ability, is conducive to the spread of flame and stable combustion in the combustion process; improve the compression ratio and using the double air tract are conducive to improving the charging efficiency of the engine, increasing the dynamic intake. At the same time, the study results also showed that airflow stagnation region in the design of the intake system to narrow the rear of the valve stem, which can reduce the loss of fluid flow process, and is conducive to the air intake; engine for double inlet, two intake must be considered the mutual position of the channel, so that the intake airflow better coupling; design may be based on the performance requirements of the engine, so that the charging efficiency and the turbulence intensity to achieve the best combination. This study further engine cylinder flow transient numerical study has important reference value, the results can provide a reference for further optimization of the engine design.

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