Numerical study of energy losses in the energy conversion process of a cold model flue gas turbine based on entropy production method

A flue gas turbine system can recycle significant energy from oil refinery catalytic cracking. This study uses six degrees of freedom (6DOF) simulation in Fluent to model flue gas turbine energy conversion. The investigation explores energy loss mechanisms with entropy production theory for comprehensive analysis. A cold-state experimental platform with a model flue gas turbine-centrifugal pump was developed. The setup converts gas to mechanical energy with the turbine, and mechanical to fluid energy with the pump. The 6DOF simulation accuracy was verified with rotational speed, torque, and power. Particle Image Velocimetry (PIV) experiments validated 6DOF numerical simulation for flow field accuracy. The efficiency of converting gas energy into mechanical energy is approximately 8%–11 %, and the efficiency of converting mechanical energy into water energy is around 11%–20 %. The stator and rotor sections of the system presented high average volumetric entropy production rates, peaking at 7731 W/m³ and 4805 W/m³, respectively. The outlet section of the system can reach a maximum total entropy production rate of 0.3 W/K. The flow separation, tip leakage vortices, horseshoe vortices, and rotor-stator wake interaction all contribute to increased entropy production. This study provides substantial engineering guidance for optimizing the energy conversion efficiency of flue gas turbine.