The Effect of Combustion Chamber Deposits on Heat Transfer and Combustion ina Homogeneous Charge Compression Ignition Engine

HCCI;Deposits;CCD;Mechanical Engineering;Engineering;Mechanical Engineering

Güralp, Orgun A.Sick,Volker ;

University of Michigan

关键词: HCCI;    Deposits;    CCD;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/58488/oguralp_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Homogenous Charge Compression Ignition (HCCI) engines have the potential to achieve diesel-like fuel efficiency while virtually eliminating NOx and soot emissions. Realizing the full fuel economy potential of the gasoline HCCI engine hinges upon our ability to expand the operating range. Due to the strong dependence of HCCI combustion to in-cylinder thermal conditions, understanding the effects of changes in the thermal boundary of the combustion chamber is essential for addressing combustion stability and HCCI operating limits. Combustion chamber deposits (CCD) are known to increase the propensity of a conventional spark-ignition engine to knock through an increase in local wall temperature, therefore it is expected they would affect the main combustion event in an HCCI engine. The objective of this work is to determine the effect of CCD on HCCI combustion. This requires a thorough understanding of the effects of deposits on heat transfer to the chamber walls.This experimental investigation was performed using a gasoline fueled single cylinder research engine. Combustion analysis is performed based on in-cylinder pressure measurements and combustion chamber wall heat transfer effects are characterized through the use of fast response thermocouples. Using these measurements, it was found that there is a clear relationship between instantaneous peak temperature phasing measured below the CCD layer and the layer thickness. Based on these findings, a methodology for calculating the thermal diffusivity of the deposit layer was developed, specific for HCCI engines. These measurements were also used to develop the Lead-Corrector method, which uses numerical finite-difference based calculation of the deposit layer instantaneous surface temperature to give insight into the direct effects of CCD on chamber heat loss.It was found that the effect of deposit formation was of a much greater magnitude on HCCI combustion than on standard combustion modes. Specifically, it was found that reduced heat loss during intake and compression resulted in earlier ignition timings while higher wall temperature swings during heat release resulted in shorter burn duration of the peripheral regions of the air/fuel charge. The heat storage effects of CCD cause the range of operability of HCCI combustion to shift downward in load value.