Influence of the Wall Heat Transfer on Flame Propagation
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Date
2016-05
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Publisher
The Ohio State University
Abstract
In the internal combustion engines, the flames interact with the walls of the cylinder, which affects the flame propagation characteristics and the engine performance. The flame tends to quench near the wall, which is due to wall heat fluxes. Also, wall heat transfer can play a significant role in undesirable auto-ignition of unburned mixture in the cylinder. The flame-unburned mixture-wall interactions can influence engine knock and affect the engine emission. The present research is aimed at understanding the effects of wall heat transfer on flame propagation. The flame propagation in the presence of the walls will be simulated and the effects of wall heat transfer on flame propagation properties will be investigated by changing wall temperature, pressures, channel widths, and equivalence ratios. By analyzing variations of those properties, we will be able to advance an understanding of flame-mixture ignition-wall heat transfer interactions, which will help reduce engine knock and emission for different types of engine structures. This research focuses mainly on the propagation of laminar premixed flames. The numerical method is used to solve the mass, momentum and energy conservation together with the combustion model. The first stage study focuses on using a single step chemistry reaction model to simulate flame propagating along one dimensional domain and two dimensional channels with adiabatic walls under different air fuel ratios, geometries, and injected flow velocity. This simulation is aimed to provide a reasonable distribution of temperature, flow velocity, pressure, fuel, oxidizer and products in the presence of the adiabatic walls. Based on the first stage, the second stage study focuses on adding heat transfer effects to the walls for two dimensional cases and analyze how wall heat transfer affects the distribution of the properties. For the first stage of research, the results from a single step chemistry model are compared with the experimental data. The results show that the single step chemistry model can accurately predict the flame consumption speed when air-fuel equivalence ratio ranges from 0.5 to 1. For the two dimensional channel with
adiabatic walls, the simulation shows that the presence of walls influences flame propagation through the flow velocity variation near the wall. In the second stage, wall heat transfer is included and the effects of wall heat transfer is analyzed in terms of flame quenching in the presence of walls. This research will lead to a better understanding of interactions of wall heat transfer and combustion in internal combustion engines, which can be a useful reference to analyze the engine knock and engine emissions.
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Keywords
Combustion, Numerical Simulation, Flame-Wall Interaction, Heat Transfer