Effect of advancing the closing angle of the intake valves on diffusion-controlled combustion in a HD diesel engine

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• 作者：J. Benajes ; S. Molina ; J. Martí ; n ; R. Novella
• 关键词：Diesel engines ; Diesel combustion ; Diesel pollutant emissions ; Variable valve actuation
• 刊名：Applied Thermal Engineering
• 出版年：2009
• 出版时间：July 2009
• 年：2009
• 卷：29
• 期：10
• 页码：1947-1954
• 全文大小：364 K

文摘

An experimental investigation has been performed on the modification of in-cylinder gas thermodynamic conditions by advancing the intake valve closing angle in a HD diesel engine. The consequences on the diffusion-controlled combustion process have been analysed in detail, including the evolution of exhaust emissions and engine efficiency. This research has been carried out at full load (100 % ) and low engine speed (1200 rpm) with the aim of generating a long and stable diffusion-controlled combustion process. The intake oxygen mass concentration was kept at 17.4 % to obtain low NO_x levels in all cases. The required flexibility on intake valve motion has been attained by means of an electro-hydraulic variable valve actuation system. The results obtained from advancing the intake valve closing angle (IVC) have shown an important reduction on in-cylinder gas pressure and density, whereas the gas temperature showed less sensitivity. Consequently, the diffusion-controlled combustion process is slowed down mainly due to the lower in-cylinder gas density and oxygen availability. Important effects of advancing IVC have also been observed on pollutant emissions and engine efficiency. Where NO_x production decreases, soot emissions increase. Finally, the results of pollutant emissions and engine efficiency have been compared with those obtained retarding the start of injection.