A streamwise-body-force-model （SBFM） is developed and applied in the overall flow simulation for the distributed propulsion system, combining internal and external flow fields. In view of axial stage effects, fan or compressor effects could be simplified as body forces along the streamline. These body forces which are functions of local parameters could be added as source terms in Navier-Stokes equations to replace solid boundary conditions of blades and hubs. The val- idation of SBFM with uniform inlet and distortion inlet of compressors shows that pressure performance characteristics agree well with experimental data. A three-dimensional simulation of the integration configuration, via a blended wing body aircraft with a distributed propulsion system using the SBFM, has been completed. Lift coefficient and drag coefficient agree well with wind tunnel test results. Results show that to reach the goal of rapid integrated simulation combining internal and external flow fields, the computational fluid dynamics method based on SBFM is reasonable.
Non-adiabatic working condition is one of the major causes of performance deterioration in micro gas turbine engines.Complex micro scale geometry,low Reynolds number operating condition and high surface to volume ratio all lead to severe heat transfer.This paper first established a simple heat transfer model to determine appropriate non-adiabatic boundary condition for computational fluid dynamics(CFD)simulations.Isothermal wall temperature is identified as a heat transfer boundary based on model analysis in combination with material selection for pre-design of the engine and verified by the experiment carried out on directed structure applied in the model.A series of numerical simulations with adiabatic and non-adiabatic boundary conditions is then carried out to study the flow characteristics of high speed,low Reynolds number micro impeller.The physical nature for significant performance degradation related to flow behavior changes due to heat transfer effect is revealed by detailed analysis of typical flow features extracted from the comparative investigation.The result established the basis for heat transfer modeling of micro impeller purposing implications for design modification in order to attain high efficiency and better performance.
