Unsteady Flow Investigation Of A 1.5 Stage Axial Turbine

Turbo-machinery interior flows are actual three-dimensional, viscous, unsteady, and the state of any point in space is absolutely no change over time is impossible. The unsteady characteristic of turbo-machinery interior flows has an important influence, of the thermal power conversion. So to have its study and research directly related to the development of turbo-machinery.Traditional methods of turbo-machinery design have made great success. These methods are based on such an important assumption that rotors and stators operate in relative steady flow conditions. As the unsteady fluctuation of flow field is neglected, these methods essentially cannot make accurate prediction of those phenomena involving unsteady flow in turbo-machinery. Deviation from real case is thus raised by the steady design methods particularly in the case of high-load and of design condition, especially in multi-stages. Taking into account unsteady flow effects may improve performance of turbo-machinery. The work in the present dissertation aims at exploiting unsteady flow phenomena to extract useful information for unsteady design methods. Numerical simulations were applied as main tool to study unsteady flow phenomena.Current numerical simulation of turbine widely used in steady three-dimensional simulation technology has shortcomings, the interface in a multi-blade rows processing using the average surface mixing approach ignores the upstream and downstream of the unsteady interaction. Turbine stage of the unsteady flow field numerical simulation is at the present stage of the important areas of computational fluid dynamics research. The objective of the presented dissertation is to investigate two numerical simulation methods of unsteady flow on the performance of a 1.5 stage axial turbine. The Nolinear Harmonic Method for numerical simulation of the unsteady flow calculated velocity distribution after nozzle and limiting streamline pattern on the blade surface are well compared the steady numerical simulation results. Based on the good validation,discussion are mainly focus on the unsteady flow structure in passage and the rotor-stator interactions. The Domain Scaling Method carry out completely unsteady simulation for 1.5 stage flows,discussion are mainly focus on the unsteady flow and unsteady effects in the three rows of cascade. The results show that the Nolinear Harmonic Method could capture the rotor-stator interactions effectively and the feasibility and advantage in modeling the deterministic stresses,the Domain Scaling Method could simulate the development of vortex and secondary flow accurately,meanwhile could simulate rotor-stator interactions,absolute total pressure change,wake disturbance and other unsteady phenomenon。...