Methodology for gas turbine performance improvement using variable-geometry compressors and turbines

Abstract

Poor part-load performance is a well-known undesirable characteristic of gas turbines. Running off-design, both compressor and turbine lose performance. Flow misalignment at the various rows causes losses to increase sharply, thereby decreasing net output faster than decreasing fuel consumption. To bring the flow to alignment with the blade passages, it is required to restagger the blades both at the compressor and at the turbine. To avoid mechanical complexities, it is generally accepted to restagger only the stators. This work deals with a numerical approach to the simulation of a gas turbine equipped with variable stators at the compressor and at the turbine, enabling the search for better-performance operation. A computer program has been developed to simulate virtually any gas turbine having variable stators at the compressor stages and turbine nozzle guide vanes. Variable-inlet guide vanes (VIGVs), variable-stator vanes (VSVs), variable-nozzle guide vanes (VNGVs), variable-geometry compressors (VGCs) and variable-geometry turbines (VGTs) are the focus in this work, which analyses a one-shaft free power turbine for power generation in the search for performance improvement at part load.

Research on the performance improvement of a two-shaft gas turbine with a variable area nozzle power turbine

“…(12)); the mass flow equilibrium equation of HPT and PT (Eqs. (13) and (14)). Besides, the target parameter, such as rotor speed, initial temperature, and power output, etc., used to describe the operating condition of the gas turbine should also be determined (Eq.15).…”

“…However, these technologies entail additional equipment installation, which not only makes the entire cycle system more complex, but also increases operating costs. In addition to above methods, operating optimization based on fuel flow (FF) and variable area nozzle (VAN) control has been carried out for many years [9][10][11][12][13][14]. Compared with pure FF control, this method can improve the operating flexibility by adjusting the power distribution of each turbine [10].…”

“…As gas turbines seldom operating in a full load condition, the research on power improvement by increasing the PT nozzle area has not been attracted enough attention. Bringhenti et al [13,14] have studied the variations of main operating parameters of two gas turbines, such as the initial temperature, thermal efficiency, surge margin, etc., under the given power output conditions with a change of the PT inlet stagger angle. The results show that the power output at ISO conditions can increase by 2.5% and 4.3% by increasing the fuel supply and opening the VAN of the PT.…”

Effect of vane opening on aerodynamic performance of the ram-rotor test system

“…Aerodynamic optimization of adjustable guide vane or stator to improve the compressors performance and to widen steady working range is simulated numerically [15][16][17]. Adjustable blade's effect on overall cycle efficiency and performance of gas turbines is also studied [18][19].…”

Study the effect of variable vanes on performance of axial compressor for single shaft gas turbine cogeneration plant

“…The variable vanes of the compressor are regulated based on the shaft speed to avoid unstable operating condition. Similarly, C. Bringhenti and J R Barbosa [2] simulated double shaft gas turbine, having variable geometry compressor and turbine, to search for better performance operation. Ma Wentong [3] has estimated the overall compressor performance characteristics through a stage by stage calculation based on the improved analogy theory and the average stage characteristics method.…”