Fadi Estefanous

Chemiluminescence imaging of pre-injection reactions during engine starting

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.

Modeling of Ion Current Signal in Diesel Combustion

Ionization in internal combustion engines produces a signal indicative of in-cylinder conditions that can be used for the feedback electronic control of the engine, to meet production goals in performance, fuel economy and emissions. Most of the research has been conducted on carbureted and port injection spark ignition engines where the ionization mechanisms are well defined. A limited number of investigations have been conducted on ionization in diesel engines because of its complex combustion process.In this study, a detailed ionization mechanism is developed and introduced in a 3-D diesel cycle simulation computational fluid dynamics (CFD) code to determine the contribution of different species in the ionization process at different engine operating conditions. The CFD code is coupled with DARS-CFD, another module used to allow chemical kinetics calculations. The three-dimensional model accounts for the heterogeneity of the charge and the resulting variations in the combustion products. Furthermore, the model shows the effects of varying fuel injection pressure and engine load on the ion current signal characteristics. Ion current traces obtained experimentally from a heavy duty diesel engine were compared to the 3-D model results. The results of the simulation indicate that some heavy hydrocarbons, soot precursors play a major role, in addition to the role of NOx in ionization in diesel combustion.Copyright

Multisensing fuel injector in turbocharged gasoline direct injection engines

With the increasingly stringent emissions and fuel economy standards, there is a need to develop new advanced in-cylinder sensing techniques to optimize the operation of internal combustion engine. In addition, reducing the number of on-board sensors needed for proper engine monitoring over the life time of the vehicle would reduce the cost and complexity of the electronic system.This paper presents a new technique to enable one engine component, the fuel injector, to perform multiple sensing tasks in addition to its primary task of delivering the fuel into the cylinder. The injector is instrumented within an electric circuit to produce a signal indicative of some injection and combustion parameters in electronically controlled spark ignition direct injection (SIDI) engines. The output of the multi sensing fuel injector (MSFI) system can be used as a feedback signal to the engine control unit (ECU) for injection timing control and diagnosis of the injection and combustion processes. A comparison between sensing capabilities of the multi-sensing fuel injector and the spark plug-ion sensor under different engine operating conditions is also included in this study. In addition, the combined use of the ion current signals produced by the MSFI and the spark plug for combustion sensing and control is demonstrated.© 2013 ASME

Multi sensing fuel injector in turbocharged gasoline direct injection engines

With the increasingly stringent emissions and fuel economy standards, there is a need to develop new advanced in-cylinder sensing techniques to optimize the operation of internal combustion engine. In addition, reducing the number of on-board sensors needed for proper engine monitoring over the life time of the vehicle would reduce the cost and complexity of the electronic system.This paper presents a new technique to enable one engine component, the fuel injector, to perform multiple sensing tasks in addition to its primary task of delivering the fuel into the cylinder. The injector is instrumented within an electric circuit to produce a signal indicative of some injection and combustion parameters in electronically controlled spark ignition direct injection (SIDI) engines. The output of the multi sensing fuel injector (MSFI) system can be used as a feedback signal to the engine control unit (ECU) for injection timing control and diagnosis of the injection and combustion processes. A comparison between sensing capabilities of the multi-sensing fuel injector and the spark plug-ion sensor under different engine operating conditions is also included in this study. In addition, the combined use of the ion current signals produced by the MSFI and the spark plug for combustion sensing and control is demonstrated.© 2013 ASME