Reduction of the Passage Between the Flame Tubes of the Combustor for a Millimeter Size Gas Turbine Engine in the Art of Micromachine Technology

Abstract

The confluence of the market demands for the production of compact power source is not only in the electronics but also in the aeromechanical field. The micromachining technology has made feasible design and developments for the gas turbine engines in centimeter or millimeter size. The current design deals with microcombustor which keeps the performance on par with the modern combustor. In this research work, we tried to reduce the size of the combustor by reducing the passage between inner and outer flame tubes. Inside the combustor, the thermodynamics is almost same as large system but due to the millimeter size design, some changes are done in the mechanics. The design confirms almost the same gas velocity and the residence time (1 m/s) which is similar to a large scale combustor. At primary zone for keeping the flow close to the wall and for producing helical fluid path, the swirlers are designed in such a way that it can introduce the air at an angle of 30° from the axis of the combustor. This process enhances the turbulence intensity of the mixing process. A cylindrical bluish flame is established as we have chosen Liquefied Petroleum Gas (LPG) for this Micro combustor. This engine may be used with a lifting vehicle so that our interest is to minimize the combustor size as well as the combustion space with maximum heat release rate. Beside the mechanism of heat release rate, we are also interested in the rate at which chemical reaction takes place. Due to these reasons the process of vaporization in case of liquid fuel is eliminated, hereby introducing LPG as a working fluid. The turbine material and the pollutant emission point of view, equivalence ratio, and stage wise air induction is properly decided. Here, it is made an annular combustor to keep lowest total pressure loss by decelerating the flow at the inlet dome of the combustion chamber. Cold and hot losses are also reduced in this design. One row of air holes on both the inner and outer domes are made in such a manner that it is blanketing the flame tubes inner surface with a relatively cool layers of air. In a nut shell this paper briefs the art of millimeter size combustor, including system design, integration, component design, fabrication, applications, and economics etc.