Investigation On The Performance Analysis And Optimization Of A Fuel-Rich Working Fluid Turbine Based On Chemical Equilibrium

To fulfill the requirement of the cyclic process of system, the gas turbine fed by fuel-rich gas is adopted in rocket propellant filling system and air turbo rocket engine. Hydrocarbon fuels are inclined to decompose at fuel-rich combustion condition, producing small molecule compounds such as CH2, CO and H2. This fuel-rich gas is expanded to drive blades to rotate in the turbine. Small molecule compounds are recombined into macromolecular compounds, making features of working fluid composition and properties distinct from conventional turbines. The turbine overall performance and optimization methods are hence impacted. In addition, given that fuel-rich gas contains intermediate products of incomplete combustion, the reaction heat is absorbed or released in different regions of flow field. The work capacity is hence altered as well, which imposes a significant influence on the vortices and shock waves in the passage of fuel-rich gas turbine. Therefore, the investigation on effect of chemical equilibrium on the fuel-rich gas turbine performance is of great significance in scientific explore and industrial applications.In this thesis, the aerodynamic design of a fuel-rich gas turbine is performed and the effect of fuel-rich gas properties and composition on turbine overall performance is investigated. The flow field analysis of a fuel-rich gas turbine at design condition is conducted to illustrate this turbine performance deviation. According to the flow phenomena, an optimization method of turbine blade is proposed. Finally, the impact of chemical reaction heat produced in the expansion process on flow structures in the blade passage is studied. Therefore, the main work in the thesis is summarized as follows,1. Aerodynamic design and characteristic analysis of a fuel-rich gas turbine composition and properties is proposed. Three gas models are then established. The fuel-rich gas properties such as Cp and y are obtained by the method of chemical equilibrium constant, and Peng-Robinson equation of state is induced to describe real gas nature. Finally, the influence of fuel-rich gas properties based on similitude principle on turbine characteristic is studied.2. Flow field analysis and optimization design of a fuel-rich gas turbine The effect of gas properties based on chemical equilibrium on detailed flow structures such as supersonic flow bubbles, passage vortices and boundary layer separation near endwalls is discussed and summarized. An optimization approach of a fuel-rich gas turbine blade is then proposed to reduce the shock wave and boundary layer separation losses.3. Impact of chemical reaction heat on flow structures of a fuel-rich gas turbine The multi-component flow model taking chemical reaction heat into account in CFD computations is established. The relationships among the alternation of composition, reaction heat and flow field characteristics are discussed. The impact of multi-component flow model considering chemical reaction heat on boundary layer, passage vortices and wave systems is then studied and concluded. Thus, as a plus to last module, this module completes the impact mechanism of chemical equilibrium in fuel-rich gas on turbine aerodynamic performance.