The Research Of The Advanced Turbine Design Method

With the development of modern high load turbine, the flow condition in blade channel becomes more and more complex. The increment of blade length makes the equal work distribution along the blade length be unable to dig the potential power of long blade at the part with high circumferential velocity. At the same time, the development of machining technique makes the cascade profile not just a combination of some simple curves. The design method of advanced aft-loading profile combining with controlled vortex method becomes a significant aspect of advanced turbine design.First, this thesis analyzed the design data of the second stage of low-pressure turbine of one gas turbine, and redesigned the turbine by the method of free vortex flow. Blade cascade is also designed in the process of turbine design. Blade profile design scheme is improved step by step through research. And 14 controlled points even distributed along both sides of mean camber line are connected by two Bezier curves. Through the analysis of the flow field, the blade profiles of 3 design sections are worked out. The contrast of new designed blade with the original one is made in the design of free vortex flow combining with aft-loading profile. It is proved that the profile loss can be decreased with the use of advanced blade through the comparison of loss coefficient of blade surface overall pressure. The advantage and disadvantage of free vortex flow method are summarized through analyzing the overall design. Then, this thesis studies the controlled vortex flow method. Through the comparison of design data, the advantage of controlled vortex flow is revealed. The reaction control is prone to equal reaction design. This increases the root reaction and root angle change and improves the flow at the root. And also this decreases the rotor tip reaction and reduces the rotor tip leakage. The turbine redesign is carried out by applying the method of controlled vortex flow combined with advanced aft-loading profile. Through comparison of several design schemes, the scheme with a moderate reaction variation and a small twist of rotor is selected and the comparison of flow field and loss of this scheme with those of other designs is made. Starting with free vortex method, this thesis improves the design method continually. In the process of improving designing, the initial design scheme of free vortex flow design method for one gas turbine is made out through the comparison of rotor/stator outlet flow angle and the computing data of middle cross section. It is verified that the design method of free vortex flow is still important in advanced turbine design. In the end, the advanced turbine design method is put forward, i.e. the method of controlled vortex flow combining with advanced aft-loading profile. The independence of computing grid is very good, the computing results are in accord with design parameters well and the results are credible.