Measurement of in-cylinder equivalence ratio during starting using a fast FID

In spite of the importance of the mixture preparation process during starting in affecting HC emissions, it has been poorly understood because the process is highly complicated by the multi component fuel, transient thermal environment, and two-phase mass transfer. For better understanding of the process, measurement of the equivalence ratio in the cylinder was attempted using a fast FID (Flame lonization Detector). Although extensive research has been made on the measurement using the fast FID, the method is not yet straightforward and needs careful operation. In this paper, the current status of the method is described. And within the limitations of the method the in-cylinder sampling test was conducted under the engine operating condition of 900 rpm, 0,527 bar intake pressure with gasoline injceted. The test results show that 15 to 20% of the injected fuel evaporates in the first cycle regardless of the amount of fuel injected. The lean limit of the equivalence ratio for engine firing was about 0.6. For secure firing in the first cycle, 5 to 6 times the stoichiometric fuel amount had to be injected. The contribution of the left-over fuel in the previous cycles to the mixture formation in the present cycle was found to be substantial.