Study on the Unsteady Turbulent Combustion Process Using Statistical Methods

点击翻译按钮获取中文摘要

New technologies based on statistical methods are developed for diagnosing unsteady turbulent combustion and are applied to describe the characteristics of turbulent flows and flame structures in reciprocating internal combustion engines. The main points of the study may be surmarized as follows.1. Random motion of particles in turbulent flows was estimated to predict the local fluctuating velocity, and the great advantage of laser homodyne method for measuring the unsteady turbulence was shown. Another technique for instantaneous turbulence detection using image analysis was applied to obtain the intensity and the sace of turbulence in diesel flames, by which the effects of swirl and high-pressure injection on the rate of turbulent mixing were investigated.2. Soot clouds formed during combustion in a compression-ignition engine were characterized by a laser-light sheet method using an argon-ion laser and high-speed photography. The obtained results showed that soot clouds were distrib … More uted on the outer edges of the luminous flames, at which the fuel-rich spots in the flame were cooled. In addition, the effects of the gas motion and turbulence on soot formation were considered from the distribution of soot clouds measured in various fuel quantities, injection timings and chamber geometries.3. Stochastic model which describes the concentration heterogeniety and the turbulent mixing process was modified by considering the premixture formation and the entrainment of burnt gas into spray. The predicted results showed that this model can well reproduce the measured results of the entire courses of heat release and the pollutant emissions under wide-spread conditions.4. Effects of the heterogeniety of mixture concentration on knock in a spark ignition engine were measured by using Rayleigh scattering method. The results showed that in the case of stoichiometry the homogeneous mixture easily causes a hard knock, thereby the compression ratio being lower than that in the heterogeneous mixture. Less