Authors: Marcis Jansons, Radu Florea, Fadi Estefanous, Dinu Taraza, Naeim A. Henein, Walter Bryzik
Addresses: Wayne State University, Detroit, MI 48202, USA. ' Wayne State University, Detroit, MI 48202, USA. ' Wayne State University, Detroit, MI 48202, USA. ' Wayne State University, Detroit, MI 48202, USA. ' Wayne State University, Detroit, MI 48202, USA. ' Wayne State University, Detroit, MI 48202, USA
Abstract: The thermal and chemical state of residual gas is known to influence the likelihood of autoignition, ignition delay and combustion phasing of the subsequent diesel engine cycle. To elucidate the role of residual gases in these processes, ultraviolet chemiluminescent reactions and their spectra are observed during the pre-injection, compression period in a dynamometer-driven, optically-accessible, diesel engine operated with a single fuel injection event. During a cold start sequence, while the engine is motored and fuel is injected without firing, the pre-injection chemiluminescence (PIC) intensity increases from cycle to cycle. This leads to a second mode of intermittent firing cycles which are observed to follow a higher intensity of PIC. In the third mode, decreased PIC intensity is measured in firing cycles that are preceded by partial misfires. In the fourth mode, firing is continuous, but with a high IMEP coefficient of variation (COV). Here, PIC intensity is found to strongly correlate with advanced combustion phasing. As firing continues, it is observed that COV, PIC intensity and the phasing correlation decrease. Upon fuel shutoff, PIC intensity decays with time. Spectral measurements confirm that reactions of low temperature combustion intermediates, including chemiluminescent formaldehyde (HCHO*) and CHO* comprise the observed PIC.
Keywords: UV chemiluminescence imaging; engine starting; pre-ignition; residual gases; autoignition; ignition delay; combustion phasing; diesel engines; cold start sequences; pre-injection chemiluminescence.
International Journal of Vehicle Design, 2009 Vol.49 No.1/2/3, pp.168 - 191
Available online: 30 Mar 2009 *Full-text access for editors Access for subscribers Purchase this article Comment on this article