Application of a Novel White Laser Sensor to an HCCI Engine

A laser-based sensor has been developed which generates short multicolored pulses for use with absorption spectroscopy techniques for the collection of thermodynamic information in an HCCI engine. Our sensor is based on supercontinuum generation which is accomplished by coupling a short-duration, high energy laser pulse (the pump) into fiber optics where colors other than the pump are generated through various nonlinear phenomena. The resulting “white pulse” is then stretched out in time by dispersive media (e.g., another fiber) to a time scale which can be collected by a high speed detector and oscilloscope. Although other multicolored (wavelength agile) laser based techniques generated by scanning mirrors or gratings have been applied to HCCI combustion [1], our supercontinuum approach offers a broad range of wavelengths with both high spectral and high temporal resolution from a source with no moving parts. It is anticipated that our sensor will be capable of probing multiple species per scan in the near future. In this paper, we specifically focus on water absorption measurements in an HCCI engine which are used to infer in-cylinder temperature for the purpose of studying the chemical kinetics which govern the HCCI ignition.