Axial Turbine Performance Enhancement by Specific Fluid Injection

Abstract

Extensively used in modern gas turbine engines in various applications, ranging from aerospace, marine and terrestrial propulsion to power generation and gas pumping, the axial flow turbines have been continuously updated and are now capable of high performances and reliability. One drawback that has not yet been resolved is the poor performance of the axial turbines at lower- than-nominal regimes. To solve these shortcomings, a new method to improve the performances at partial regimes by specific fluid injection is proposed in this paper. The influence of the injection system is determined by conducting a numerical analyze, studying the influence of different parameters (i.e., number, dimensions and position of the of injection orifices) on the overall performances of the turbine. The study is completed on a single stage 1300 KW turbine with the injection system being applied to different power settings across the working line. The results show that the power generated by the turbine can be enhanced by as much as 30% for different configurations of the injection system (i.e., high number of small size orifices) and different partial regimes.

Application of a Performance-Improvement Method for Small-Size Axial Flow Turbines

“…The power increase due to higher velocities overcomes the losses resulting from fluid interactions in the vicinity of injection sections. This effect has been determined in previous studies [3], as well as in this paper, with an increased power generated by the rotor after injection. From a certain regime onwards, the injection system will not lead to a power increase anymore and will most likely lead to a reduction in rotor-generated work due to increased pressure losses.…”

“…The results were obtained without increasing the total mass flow through the turbine. It was also found that the effectiveness of the injection system is dependent on the turbine regime, with injection at higher operational regimes showing better results [3].…”

“…Turbine design is performed and optimized at nominal regimes, for a set of inlet parameters and power requirements; thus, when operating at different regimes, the flow through the channels and the resulting performance may be less than desirable. To overcome this drawback and improve the axial turbine's performance at partial loads, a new method to control the flow through the turbine has been proposed in [2,3]. The method consists of injecting a fluid into specific sections of the turbine vanes in order to modify the flow field, accelerate the working fluid, and, thus, increase the rotor-generated power.…”

“…The injection mechanism in a film cooling system has been the main topic for a number of works, such as [4][5][6][7][8][9][10][11], studying the influence of different parameters on the film flow and its effectiveness. The main difference between the film cooling injection and the system proposed in [2,3] is that, in the case of cooling, the objective of injection is to create a layer on the surface of the vane or blade without disturbing the flow through the turbine. For the performanceimprovement method by specific fluid injection, the aim is to influence the flow in order to accelerate the working fluid and, thus, increase the power output of the rotor.…”

“…The aim of this paper is to apply the injection system studied in previous works, see Refs. [2,3], to a microjet engine, determining its influence on the turbine performance and engine behavior after the injection process. The paper presents the construction of the numerical models and the analysis of the injection-system performance at different partial regimes across the working line, as well as the engine response to the activation of the injection system and the resulting stabilized regimes.…”