Professor Paul Ewart

Abstract:

Planar Laser-Induced Fluorescence has been widely accepted and applied to measurements of fuel concentration distributions in IC engines. The need for such measurements has increased with the introduction of Direct Injection (DI) gasoline engines, where it is critical to understand the influence of mixture inhomogeneity on ignition and subsequent combustion, and in particular the implications for cyclic variability. The apparent simplicity of PLIF has led to misunderstanding of the technique when applied to quantitative measurements of fuel distributions. This paper presents a series of engineering methods for optimizing, calibrating and referencing, which together demonstrate a quantitative measure of fuel concentration with an absolute accuracy of 10%. PLIF is widely used with single component fuels as carriers for the fluorescent tracers. This paper shows that this method inadequately describes a real fuel spray, and presents instead a method that uses a fully fractionated multi-component fuel for PLIF diagnostics. A series of measurements is presented of fuel distribution, early injection DI homogeneity and cyclic variation of injector plumes in a DI single cylinder optical research engine. Copyright © 2008 SAE International.

Abstract:

A technique has been developed for full bore imaging, and a high speed video camera used to obtain images that have been processed for soot temperature and loading, and flame growth. The soot measurements have been made with a colour ratio technique that avoids the need for an in-situ absolute radiation calibration. Instead, the spectral response of the camera has to be determined for each of the red, green and blue channels. Planar Laser-Induced Fluorescence (PLIF) has been extensively used for visualizing species of combustion and reacting flows. However, the relationship between PLIF signal strength and species concentration is complicated by other dependencies, so careful calibration is essential. In order to study the effects of evaporation of a multi-component fuel in an IC engine, a gasoline-like component fuel has been devised which has three components of low, medium and high-volatility. Each component is made from two non-fluorescing constituents chosen so that the component (as a whole) will co-evaporate with one of three selected tracers: namely acetone, toluene or 1,2,4-trimethylbenzene (TMB). Calibration results are presented along with fuel concentration distributions derived from the PLIF images that have been analyzed on a cycle-by-cycle basis. © IMechE 2007.