Numerical study on heat transfer in pulse burners

Fluid flow in pulse burner is pulsatile in nature, driven by the pulsating combustion process. Heat transfer, which mainly takes place in the combustion chamber, is an important process that is not very well understood. Since the combustion chamber is usually short, the flow is basically both hydrodynamically and thermally developing. In stead, the problem is studied numerically for a wide range of Womersley Numbers from 0 to 40, and large velocity oscillatory amplitudes from 2 to 4 time the mean velocity. The finite control volume and SEMPLEC method are used. The numerical results show that the temperature oscillation is dominated, as expected, by the velocity oscillation, and its frequency is consistent with that of the oscillatory velocity. The spatial temperature profile in pulsatile flow is quite different from that of the steady flow. A thick oscillating buffer region exists and it plays an important role in transporting thermal energy form the center core region to the conduction sub-layer that exists next to the wall. The oscillatory temperature profiles along the axial direction are similar except that their amplitudes decrease towards the downstream. The thermal boundary layer exists at all time and becomes thinner as the oscillatory frequency of the flow increases, which lead to better heat transfer in pulse burner.