UBC Theses and Dissertations
Numerical analysis of high pressure injection of natural gas into diesel engine combustion chambers Walsh, Paul
The behaviour of a transient turbulent jet of natural gas as it is injected into a simulated combustion chamber of a diesel engine was investigated using numerical techniques. The TEACH code developed by A.D. Gosman of Imperial College, London, was used to investigate the influence of parameters such as injection angle, engine speed, and reservoir tank-to-chamber pressure ratio on the development of the jet. It has been shown that the TEACH code is fully capable of predicting details of jet behaviour such as radial and axial velocity and concentration profiles when compared to known data. The code has been modified to use a compressing and expanding grid to simulate the effects of piston motion. A model of a fixed geometry combustion chamber revealed that the most influential parameter on jet behaviour is the injection angle. The jet had a tendency to adhere to either the top wall of the chamber near the injector tip or to the bottom wall directly opposite depending on the injector angle. The compressing grid simulation showed that the presence of piston motion combined with other parameters such as injection angle and pressure ratio, produced jet characteristics that were dissimilar compared to the fixed boundary model. In general it was shown that the jet was less sensitive to injection angle and strongly influenced by increased pressure ratio as a result of the moving boundary.
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