Effect of trailing edge size on the droplets size distribution downstream of the blade

Abstract

Operational flexibility, such as fast start-up time, ability to adapt to the load change as well as high efficiency has made the gas turbines as one of the most important energy devices among the thermal power systems. It is well-known that gas turbines efficiency decreases with an increase in the ambient atmospheric temperature. For that purpose, recently fogging of water droplets have been utilized to increase the power output of these industrial gas turbines. Based on fogging principle, Advanced Humid Air Turbines (AHAT) are developed which utilizes the humid air to increase the thermal efficiency of the gas turbine systems. In this paper, the characteristics of the humid air system are investigated experimentally. Extensive high-speed images were taken using a high-speed camera. Analytical models are proposed based on the mass and energy conservation principle to understand the effects of the thickness of the trailing edge of the droplets size distribution after the trailing edge of the cascade blades. From the proposed model and experimental data, it is found that the primary droplets formed are inversely proportional to the Weber number (based on the blade thickness). It is also concluded that if the Weber number of the two profiles were kept constant, then the one with greater trailing edge thickness would result in larger primary droplet size and vice versa.

Keywords

• gas turbine
• fogging
• trailing edge thickness
• water sheet primary breakup
• shadowgraph images