Simulation of a turbocharged SI engine to investigate autoignition, knock onset and flame propagation by using Kiva code

Knock is a random and complex phenomenon in reciprocating engines and engine tests under knocking conditions involve high costs. In this investigation, EF7(TC) engine which is a bi-fuel spark ignition engine and has relatively high probability of knock phenomena, is used. The simulation is conducted using KIVA-3V code to simulate the engine under non-knocking and knocking conditions. ANSYS-ICEM software is used to generate structured mesh for its geometry which is provided by IPCO. The original KIVA-3V code doesnt have an auto-ignition model; therefore, a knock integral model has been added to the original code. In this paper, the results of simulation are verified using two methods, experimental in-cylinder pressure and exhaust port gas temperature. The theoretical results proved a good agreement with experimental data. Compare to experimental data, it shows that KIVA-3V and Integral Knock method could simulate knock accurately although the code cannot simulate the fluctuations of knock. Finally, development of flame in combustion chamber and formation of second flame front was investigated in numerical simulation. Besides, the simulation results show that second flame-front is created near exhaust valves and propagate onward. The results show that the model can accurately predict autoignition and calculate the effects of Knock, So, it is possible to use this model to investigate the Knock phenomenon and its effects without any experimental tests which engine damages are expected during a knocking cycle.