2010 Volume 52 Issue 159 Pages 9-16
A novel diagnostic technique named “Tracer Producing LIF technique” which permits 2-dimensional measurements of internal EGR in an engine cylinder has been developed. The feature of this technique is utilizing a fuel additive which does not emit LIF signal but its combustion products radiate strong LIF emission. Internal EGR behaviors can be measured by observing the LIF images excited by a UV-laser sheet. Firstly, the principle of this technique and selection of fuel additives are described. Then, "Tracer Producing LIF technique" was applied to the visualized engine, in which whole pent-roof area can be observed from the engine side direction. Internal EGR behaviors have been measured from suction to exhaust in whole engine cycle. As a result, gas exchange process between burned gas and air, as well as the influence of the valve timing on the above process were clarified. It was also confirmed that inhomogeneous internal EGR distribution still existed at the ignition timing for the first time.
