3-D Design And Performance Optimization Of A Stage Of Turbine

Turbine is a main component of a gas turbine engine, by which part of the thermal energy in the high-temperature and high-pressure gas from the combustion chamber, can be converted to the mechanical kinetic energy. A marine gas turbine is characterized with high power, high temperature, high rotating speed and high efficiency ,as well as size and weight restricted by strict rules. For these years, scholars in aerodynamics field have attached great importance on the theories and methodologies of turbine design as well as numerical simulation and performance optimization.Following the prescribed instruction of a turbine design, in this thesis, a blade shape is created for the first stair of the certain marine gas turbine. On the basis of constant circulation and iso-α₁ twisted laws, the blade shape is made by a three-dimensional aerodynamic design, and produced by parameterization. Applying NUMECA, a commercial software, the produced blade shape is simulated, the differences of two twist laws are explored, and the validity is testified by making a comparison between the outcome and the theoretical value. Then a series of analyses on constant circulated blade are conducted, which include analyses of the S₁ stream surface and the S₂ stream surface, discussions of the vortices in the cascades, analyses of the features in two-dimensional unsteady flow field, etc.After that, it is found that the defects of the designed blade shape exist, and the influences of load distribution on the aerodynamic performance. Then some improvements can be managed after considering the profile pressure distribution, as well as the total pressure loss coefficient and adiabatic efficiency which is influenced by the profile pressure distribution. According to the secondary flows loss theory, several trials are conducted on stator blade and rotor blade by different curve angles, and the conclusion can be draw after numerical simulation: the curved blade can control the radial pressure gradient, change the distribution of the reactionary degrees over the blade height and promote the flow field in cascade. This is followed by various compound models with different curve angles on stator blade and rotor blade, and consequently a matching question about caused by several parameters such as flow angle, Mach number is discussed, which can be solved by deploying proper ones. Finally, different blade axial intervals between the stator and the rotor are tried to observe the influences on aerodynamic performance.After the speculation and promotion, turbine's adiabatic efficiency is raised by 1.84%, which proves the effectiveness of the optimizing and improving approaches of this project in decreasing loss and lifting efficiency.