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A novel diagnostic technique named a “Tracer-Producing LIF technique” which enables 2-dimensional measurement of an internal EGR within an engine cylinder, has been developed. The main feature of this technique is the utilization of a fuel additive that does not itself emit an LIF signal by irradiation of UV-light but whose combustion products radiate strong LIF emissions by UV-light irradiation. Internal EGR behaviors can be measured by observing LIF images that are excited by a UV-laser sheet. Firstly, principles of this technique were confirmed and fuel additives were selected. Then, the “Tracer-Producing LIF technique” was applied to an optically accessible single-cylinder gasoline engine in which the entire pent-roof area can be observed from the side of the engine. The internal EGR behaviors were measured through the entire engine cycle, from intake to exhaust.

Two-line excitation LIF (Laser-Induced Fluorescence) technique for 2-dimensional temperature measurements in an engine cylinder before ignition is presented. From the fundamental examinations, the combination of toluene tracer with a pair of excitation lines of 248nm and 266nm has been selected because of the high LIF intensity ratio and closer excitation wavelengths. In-cylinder thermometry is conducted using a visualized single cylinder spark ignition engine both in PFI (port-fuel-injection) and DI (direct-injection) operation. The accuracy of this technique is determined through the homogeneous PFI experiment. Temperature and fuel distribution in unburned mixture are measured simultaneously in DI operation. It exists a strong correlation between equivalence ratio and temperature inside the mixture. Temperature in the fuel rich region is lower than in the fuel lean region.

A multi-component fuel vaporization model is developed for numerical analysis of specific fuel component behaviors in port-fuel-injection(PFI) gasoline engines. In order to specify the differences of in-cylinder fuel distribution among its components, three-dimensional calculations of intake flow, spray and vapor motion of each component are performed with respect to engine wall temperature and the distillation characteristics of the fuel. Simultaneous measurements of in-cylinder behaviors of different volatility components in the fuel are also carried out using a laser-induced fluorescence (LIF) technique to validate the calculation results. In both measurements and calculations, the same fuels are used, which are composed of seven or eight components to simulate the distillation characteristics of two kinds of gasoline. The in-cylinder vapor amount of high and low volatility components is compared between the calculations and the experiments.