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Technical Paper

Numerical Simulation of Turbulent Mixing in a Transient Jet

To understand further the mixing process between the injected fuel and air in the combustion chamber of a diesel engine, the turbulent mixing process in a one-phase, two-dimensional transient jet was theoretically studied using the discrete vortex simulation. First, the simulation model was evaluated by comparisons between calculated and experimental data on two-dimensional turbulent jets. Second, the trajectories of the injected fluid elements marked with different colors were graphically demonstrated. Also the process of entrainment of the surrounding fluid into the jet was visually presented using colored tracers.
Technical Paper

Development of a Rapid Compression-Expansion Machine to Simulate Combustion in Diesel Engines

A rapid compression-expansion machine which can simulate the combustion processes in diesel engines is developed. The configuration of the combustion chamber is a 100 mm bore and a 90 mm stroke, and the compression ratio is 15. The piston is driven by an electro-hydraulic system with a thrust of 90 kN and the maximum frequency of 20 Hz. The whole system composed of a hydraulic actuator, a fuel injection system, and a valve driving unit is sequentially controlled by a computer. The reproducibility of the stop position of the piston at the end of compression is achieved with an accuracy of ±0.1 mm by employing a hydraulic-mechanical brake mechanism. The experiment shows that the combustion in the expansion stroke is achieved, and that the combustion characteristics such as the rate of heat release and indicated output as well as the exhaust emission can be measured.
Technical Paper

Effect of High Pressure Injection on Soot Formation Processes in a Rapid Compression Machine to Simulate Diesel Flames

The characteristics of diesel spray and flame in a quiescent atmosphere were studied as a function of injection pressure ranging from 30 to 110 MPa. Measurements included the spray form and Sauter mean diameter of a non-evaporating spray, the liquid phase penetration of an evaporating spray and the visualization of sooting zone in a flame. Experimental results show that high pressure injection improves the atomization and air entrainment of non-evaporating spray and that the liquid phase penetration of evaporating spray is hardly affected by injection pressure, demonstrating a promotion of evaporation with injection pressure. Visualization of the sooting zone in a flame made it clear that high pressure injection is advantageous in reducing soot formation and shortening the combustion duration.
Technical Paper

A Photographic and Thermodynamic Study of Diesel Combustion in a Rapid Compression Machine

A diesel spray and flame in a quiescent atmosphere were realized without interference with combustion chamber walls in a newly constructed rapid compression machine. High speed shadow photography and pressure measurement were employed to obtain data for calculating the amount of air entrainment into the the flame and spray. From a comparison of air entrainment between the flame and spray, it turned out that when ignition delay becomes longer air entrainment into flames is promoted by the thermal expansion of multi-points ignition sources in the central region of the spray.