Numerical investigation of the hydrogen swirl combustion flow in a micro gas turbine burner

Abstract

The influence of swirl angle and hydrogen mixing ratio on the performance of micro gas turbine combustor is discussed by numerical simulation based on computational fluid dynamics (CFD) method, the parameters such as combustion characteristics and pollutant emissions are analyzed. The realizable k-epsilon model is adopted for turbulence simulation, the combustion model is general finite rate model. The results indicated that increasing swirl number reduces the temperature and NO emission. As hydrogen content in the fuel increases, flame length is slightly shortened, temperature in the combustion chamber rises, and temperature distribution becomes more uniform, NO emission at central axis becomes highly, while CO2 and CO emissions decrease. When hydrogen mixing ratio is 50%, the maximum NO emission is about 3 times that of pure methane combustion, and CO2 mass fraction is reduced by 43.9%, moreover, outlet CO emission is reduced by nearly 70%. The hydrogen mixing ratio has a greater impact on pollutant emissions, the sensitivity level of NO and CO emissions to hydrogen mixing ratio reaches 0.25 and 0.39 respectively. As hydrogen mixing ratio and swirl number increases, pressure loss grows, and average turbulent kinetic energy on central plane gradually rises, mainly in outlet region and recirculation zone. Increasing swirl number makes the synergy better, but hydrogen mixing has little effect on the synergy distribution.

Numerical investigation on combustion flow characteristics of a micro gas turbine swirl combustor with different protruded bluff body structures

“…Based on previous prototype without bluff body, 21 one micro gas turbine with protruded bluff body from the inlet is proposed in this paper, the new combustor also adopts two-stage swirling combustion, inner diameter and outer diameter of internal swirl inlet is 10 mm and 38 mm respectively, inner diameter and outer diameter of external swirl inlet is 38 mm and 100 mm respectively, and the length and outlet height of the combustion chamber is 506 mm and 109 mm respectively. Other detailed dimensions are shown in Figure 1(b).…”

“…Previous studies focused on the effect of bluff body inside the combustor on flame stability and blowoff characteristics. In order to further improve the combustion chamber performance, a micro gas turbine swirl combustor with protruded bluff body is proposed on the basis of previous combustor prototype used in industry, 21 which is shown in Figure 1(a). The protruded bluff body is behind the inlet and causes the gas flow to expand radially, which changes the vortex structure and flow characteristics, and the combustion and emission performance can be enhanced.…”