Numerical simulations for performance enhancement of a radial, pressure wave driven, internal combustion engine.

摘要

The Wave Disk Engine is a new engine concept which employs pressure wave compression and expansion, constant volume combustion, and power extraction within a compact rotating disk. It is a logical next step in the advancement of internal combustion wave rotor technology. Such devices achieve compression of a combustible mixture by the sudden closing of a port and power extraction when a port opens. The timing of port opening and closing is determined by the time required for compression and expansion waves to travel along the length of the channel.;Most of the research in this field has been directed at finding the correct port timings purely on the basis of fluid mechanics. However combustion inside these devices has not been studied in a thorough manner either numerically or experimentally. The first part of this work discusses numerical investigations attempting to understand the combustion process in the presence of a periodic flow induced by the opening and closing of ports. Numerical evaluations are provided for the detailed flame shape for simplified chemistry and a simulation using the detailed San Diego mechanism. Other quantities examined are vorticity, pressure fluctuations, mass consumption rate, flame surface area and the influences of adiabatic and non-adiabatic channel walls. The focus of the study is on quantities that influence overall burning rate and completeness of combustion.;The second part of this work deals with the introduction of certain design features to the Wave Disk Engine which can help in increasing the power extraction and overall efficiency of the device. These include - reinjection of combusted gas into fresh combustible mixture, a second row of turbine blades outside the wave disk, and an external combustion chamber. The overall thermodynamic efficiency of this device, which references the Humphrey thermodynamic cycle, increases with the increased pressure inside the combustion channel prior to combustion. One possible and sustainable way of achieving pre-compression in a combustion channel is to re-inject combusted gas from the previous cycle, before it is expanded. Computational fluid dynamic simulations are run for different angular speeds of the engine and widths of the re-injection passage. A balance is sought between loss of mass and enthalpy in a high pressure combustion channel and the gain in pressure and enthalpy in the low pressure channel, which would maximize overall cycle efficiency. A Wave Disk Engine equipped with a reinjection passage as well as a second row of turbine blades is provides the highest thermodynamic efficiency in this study. Another Wave Disk Engine design is proposed which addresses the problem of seizing by using two discs made of ceramic stacked on top of each other. One disc serves as a combustion chamber and the other to compress fuel-air mixture and generate power.