| Abstrakt: |
In gas turbines, the effect of exhaust diffusers on the efficiency of the entire gas turbine unit (GTU) is quite significant, especially when the GTU is operated as part of a combined cycle gas plant (CCGT). Here, the pressure behind the turbine has increased values in order to ensure the passage of hot exhaust gas through the recovery boiler. Highly efficient operation of the diffuser results in an increased pressure drop in the gas turbine, thereby generating the necessary power with high efficiency. Thus, the main function of the diffuser is to convert the kinetic energy of the flow behind the turbine into static pressure with minimal losses. Since the flow in the diffuser is inhibited, it is prone to separation. In order to avoid separation phenomena and, accordingly, an increase in losses in the diffuser, recommendations were developed on the appropriate shape of the flow path of the diffuser. However, the proven geometry of the diffuser itself fails to guarantee the required characteristics, because the distribution of flow parameters at the entrance to the diffuser has a significant impact on the operation of the diffuser. Analysis of the distributions of the flow parameters behind the original turbine GTE-65.0, which is a prototype for the modified turbine 65.1, showed that the distribution of the total pressure P t ∗ and the angle of the flow outlet α2 were unfavorable for the effective operation of the diffuser, since they led to the appearance of separation zones on the power struts and on the bushing surface of the diffuser channel. Therefore, in order to increase the efficiency of the diffuser in the modified turbine GTE-65.1, the nozzle and working blades of the fourth stage were redesigned. The purpose of the redesign was to obtain such distributions of the total pressure and flow angle at the turbine outlet that would minimize the number and size of flow separation zones and reduce losses in the diffuser ζdif and increase the value of the pressure recovery factor Cp in the diffuser compared to the value of Cp in the diffuser of the original turbine 65.0. [ABSTRACT FROM AUTHOR] |
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