Fogging has been gaining considerable importance among the gas turbine manufacturer mainly because of being the most cost-effective and efficient method to augment the power output of gas turbines. In this paper, the fundamental experimental study was conducted to understand the characteristics of two-phase phenomena around the cascade blade. Water was ingested from the holes located at different spanwise positions at the blade’s leading edge. Detailed visualization was conducted by taking shadowgraph images using a high-speed camera. Characteristics of water film formation and the droplet size distribution were measured and were also theoretically investigated. It was found that the liquid film thickness and the droplet size aft the trailing edge of the cascade blade were mainly functions of the surface tension of the liquid and the surrounding air velocity, whereas, it was independent of the shape and size of water ingestion hole.

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In this paper, conjugate heat transfer (CHT) simulation is performed for a low-pressure stage of MGT-70, a heavy-duty gas turbine (GT) manufactured by MAPNA Group. Although the vane and the blade are uncooled, CHT analysis is performed to assess the validity of using the fluid temperature of an adiabatic simulation as the uncooled vanes or blades temperature, and also to model the heat transfer between root or shroud and vane or blade profile. To compare the resultant temperatures of CHT and adiabatic flow analysis both simulations are done, using the same boundary conditions. The vane shroud extends over the blade tip, which is of free-standing type, and there is not a shroud segment. In fact, the vane and blade share the shroud. In order to predict the shroud temperature more accurately, the vane and the blade are simulated simultaneously as a stage using appropriate interfaces. A single vane CHT simulation is also performed to evaluate the effect of blade tip flow on the shroud temperature. Furthermore, the cavity above the shroud, containing the cooling and sealing flow, is also included in the model to better prediction of the shroud temperature. In addition, the rim cavity and the labyrinth seal under the vane platform are included in the model to better predict the vane platform temperature and to capture the effect of purge flows on vane and blade temperature. Simulation results show that, although, the average bulk temperature of the profile in both CHT and adiabatic simulations are close to each other, there are great differences in temperature distribution over the suction side and pressure side. These differences are because of heat flux through the profile in CHT simulation, which results in a more realistic metal temperature distribution. Comparing the results of the single vane simulation and stage simulation no remarkable difference is observed in the temperature distribution, except for the shroud region above blade tip. This reveals that, although, the tip leakage flow is better captured in the stage simulation, it is only useful when the shroud temperature is of interest and it does not affect the vane profile temperature distribution. Finally, the inclusion rim cavity and labyrinth seal in the simulation helps to predict the mass flow distribution of purge flows and the effect of these flows on platform temperature distribution in vane and blade.

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This paper presents the methodology and results of a design optimization of a single stage, axial compressor. At the design point, the compressor achieves a total pressure ratio of 2.33 at a mass-flow rate of 1.11 kg/s. The compressor is part of an electrically powered active high lift system (AHLS) for future civil aircraft. An automated process using numerical models to evaluate aerodynamic performances and mechanical loads due to centrifugal forces is used. This evaluation process is coupled to an evolutionary algorithm to help investigate the design-space. A parameterization strategy was developed to cover a wide design-space, excluding unreasonable designs. The goal was to satisfy the challenging design requirements of high pressure ratio, high power density and limited rotation speed imposed by the AHLS. The resulting design of a highly loaded compressor is characterized by significant end-wall slope and low blade aspect ratios, resembling a mixed flow compressor. According to CFD analysis it is predicted to cover the required operating points at total-total, polytropic efficiencies higher than 80 %.

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