| As a direct response to the need for further performance gains from current gas turbine,adding stages is an important tendcy of the marine main propolusion system. Based on a triaxial simple cycle marine gas turbine,this thesis analyse several problems involved in the design process to increase power and efficiency by the method of adding stages in front of compressor.A deeply cycle analysis was conducted based on the thermal parameters of mother gas turbine(MGT) on the rated load status, and the variable specific heat capacity mathematical models of those key components of MGT such as compressors,turbines,combusion chamber,were established. And a lot of research studies,such as adding one stage or two stages before low commpressor,adjusting the rated load status,modulated design the low pressure compressor,were conducted based on the variable specific heat capacity mathematical model of MGT,analyse the influence by these schemes and then get the final plan.In the aerodynamic design,complete rotor firstly and then design the stator which match the parameters of rotor.The cascade model is established by the parametric blade design through Fine/Autoblade software and solving the performance of the model by CFD numerical calculation.Modified the shape of airfoil for the shortcomings of the initial design amendment.Finally got a high load transonic rotor which pressure ratio is almost 1.77 when the efficiency got about 90%.Lots of research has been conducted with compressor cascades composed of conventional straight blades,positive leaned blades,positive curved blades.It is shown that the passage vortices are quite strong in the straight blade,cascade. the secondary loss at the two ends is much higher.On the acute side of the positive leaned blade cascade,the hub corner stall disappears but shroud corner stall appears.Blade positive curving introduces the effect of positive lean on the two ends,the concentrated shed vortices move and converge towards the midspan. |
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