A miniature combustor using kerosene fuel for a 100 W-class micro gas turbine was developed. The unique feature of this combustor is the use of porous media as a liquid-fuel vaporizer. The porous media was heated by combustion, causing the vaporization of the liquid fuel in the miniature combustor and the mixing of the vaporized fuel with air, which resulted in lean-premixed combustion. Experimental results indicated that the flame was stable including the design operation condition and that the combustion efficiency was >99.5%. The NOx emission was low as <15 ppm. The orifice located in the combustion chamber had significant effects on the flame stability and combustion efficiency. The effects of this orifice on the flame stability and the emissions were examined. The proposed miniature combustor using the porous-media vaporizer is suitable for practical use in the 100 W-class micro gas turbine.

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To design a gas turbine combustor for low emissions, carbon monoxide (CO) generated near the cooled wall is one of the important indexes. However, the measuring of CO concentration is difficult in experiments in actual conditions of high pressure and temperature. In this study, in order to take the heat loss effect on the cooled wall into account, a non-adiabatic flamelet generated manifolds (NA-FGM) approach, which can account for the change of gas composition due to the heat loss, is applied to two-dimensional numerical simulations of premixed flame near the cooled wall and the effect of equivalence ratio variation on the CO concentration is investigated. The results show that the CO concentrations predicted for the equivalence ratio of 1.0 using the NA-FGM approach are in good agreements with those using the detailed reaction approach, and that the NA-FGM approach can adequately catch the tendency of CO generation in the vicinity of the wall with heat loss.

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The objective of this study is to quantify the sensitivity of blade roughness on the overall performance of a 10-stage high-pressure compressor of the jet engine type V2500-A1. The Reynolds-Aver-aged Navier-Stokes flow solver TRACE is used to study the multi-stage compressor. The three-dimensional numerical setup contains all geometric and aerodynamic features such as bleed ports and the variable stator vanes system. In order to estimate the effect of stage roughness on overall compressor performance, compressor maps of the CFD-model are created by modeling the surface rough- ness separately for a single stage and combinations of stages. The surface roughness values are applied to the blade’s suction side of the first, center and last stage in the CFD-model by setting an equivalent sand-grain value. This equivalent sand-grain roughness is determined from non-intrusive measurements of blade surfaces from an equivalent real aircraft engine for the first, center and last stage. In addition, further simulations are conducted to analyze the performance drop of a fully rough HPC due to surface roughness. The studies are performed at the operating conditions ‘cruise’ and ‘take-off’ to cover two different Reynolds number regimes. The results show that the models with roughness in a single stage already lead to significantly lower mass flow rates because of higher block-age compared to the smooth compressor. In fact, roughness at the first stage has the biggest effect on the overall performance with a drop in performance of about 0.1% while the effect of the last stage is the smallest. This behavior is mainly caused by enhanced instabilities through the compressor changing the stage-by-stage matching of the stages downstream. In addition to the displacement of the compressor maps to a lower mass flow, a reduction of stall and choke margins is noticeable.

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