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The swirl and axial components of gas velocity in the disk type combustion chamber of a fired and motored spark ignition engine were measured using a fiber-optic laser Doppler Anemometer (LDA). The engine was operated at a speed of 1500 rpm, a volumetric efficiency of ηυ = 0.5, an equivalence ratio ϕ = 1.4 and with an ignition timing of θig = 30°BTDC (MBT condition). The gas velocities at 9 points on a diameter at mid-height of the combustion chamber were processed by the cycle-resolved frequency discrimination method. The bulk (mean) velocity was determined by frequency components lower than a cut-off frequency of 667Hz. The flame propagation pattern was detected by ionization probes set at 17 points on the piston. The results indicate significant differences in flow characteristics between motored and fired conditions during the combustion period.

This paper presents an experimental study on the effects of Exhaust Gas Recirculation (EGR) on soot emission and diesel knock by using a direct-injection diesel engine. The effect of EGR on soot emission depends on operating conditions. Under the condition that the mass fraction burned by pre-mixed combustion of the two combustion patterns is increased, soot emission is decreased by EGR. It is also revealed that the EGR has the effects of both increasing and decreasing the diesel knock intensity. The mechanisms of these effects of EGR on soot emission and diesel knock are discussed.

The purpose of this study is to reveal the effect of use of W/O emulsified fuel without additives on DI diesel combustion. The combustion pattern, which means the ratio of fuel mass burned in the premixed (or the diffusion) combustion period to the overall supplied fuel mass, is varied by changing the injection timing and the intake manifold pressure. The exhaust emissions, such as particulates, NOx and CO, are measured. By analyzing the indicator diagrams, ignition lags are also measured. Contrary to the results of the other studies, NOx is hardly reduced by using the emulsified fuel, although it does not increase. While the particulate emission is considerably affected, remarkable changes in S.F.C. and the exhaust gas temperature are not recognized. With decreasing the fuel mass fraction burned in the prernixed combustion (spontaneous ignition) or the intake manifold pressure, the effect of the emulsification on particulate emission turns from the promotion to the suppression.

In order to improve adaptability of the laser Doppler anemometer (LDA) to measurement of gas flow velocities in an internal combustion engine, an optical fiber system composed of a couple of single mode, polarization-preserving optical fibers has been developed to transmit the incident beams. The overall light transmission efficiency of the system is 24 % and not so high, but the system enables real-time measurements of gas flow velocity in the combustion chamber of a small two-cycle engine during firing operation. The velocity data measured are processed with cycle by cycle analysis by stationary time-averaged method to obtain bulk velocity Ū, turbulence intensity u′ and integral time scale of turbulence Lt.