Experimental and Numerical Study on Optimizing the DLN Micromix Hydrogen Combustion Principle for Industrial Gas Turbine Applications

Abstract

Combined with the use of renewable energy sources for its production, hydrogen represents a possible alternative gas turbine fuel for future low emission power generation. Due to the difference in the physical properties of hydrogen compared to other fuels such as natural gas, well-established gas turbine combustion systems cannot be directly applied to Dry Low NOx (DLN) hydrogen combustion. The DLN Micromix combustion of hydrogen has been under development for many years, since it has the promise to significantly reduce NOx emissions. This combustion principle for air-breathing engines is based on cross-flow mixing of air and gaseous hydrogen. Air and hydrogen react in multiple miniaturized diffusion-type flames with an inherent safety against flash-back and with low NOx-emissions due to a very short residence time of the reactants in the flame region. The paper presents an advanced DLN Micromix hydrogen application. The experimental and numerical study shows a combustor configuration with a significantly reduced number of enlarged fuel injectors with high thermal power output at constant energy density. Larger fuel injectors reduce manufacturing costs, are more robust and less sensitive to fuel contamination and blockage in industrial environments. The experimental and numerical results confirm the successful application of high energy injectors, while the DLN Micromix characteristics of the design point, under part load conditions and under off-design operation are maintained. Atmospheric test rig data on NOx emissions, optical flame structure and combustor material temperatures are compared to numerical simulations and show good agreement. The impact of the applied scaling and design laws on the miniaturized Micromix flamelets is particularly investigated numerically for the resulting flow field, the flame structure and NOx formation.

NOx Emissions Predictions for a Hydrogen Micromix Combustion System

“…On each plane, mass weighted averaged static temperatures and hydroxyl mole fractions were calculated to capture the flame shapes and positions. Figure 3 recirculation zones, which are characteristic of the micromix jet-into-cross-flow injection feature [21], are correctly captured. The inner vortex comes from the recirculation of colder air from the air stream inlet, whereas the outer vortex arises from the hot gas recirculating downstream the hydrogen injection.…”

“…The computational model used in this study is based on previous work carried out at Cranfield University where the injector jeometry was investigated through two dimensional and three dimensional CFD simulations [20]. This gemetry derives directly from the injector configuration developped by Aachen University, where the computational model was validated experimentally [21]. A hexahedral mesh consisting of about 920,000 computational cells was created with a refinement in critical regions, such as the ducts where air and fuel are injected and the flame region.…”

Comparison of Hydrogen Micromix Flame Transfer Functions Determined Using RANS and LES

“…The computational model used is based on previous research at Cranfield University on the design of hydrogen micromix combustion systems using CFD [27]. As experiments on these combustion systems have not yet been conducted at Cranfield University to validate the simulations, the computational model is derived from the configuration investigated by Aachen University which has been validated experimentally [28]. This will allow the preliminary CFD work to inform the initial test rig configuration design and undergo a validation process once experiments have commenced.…”

Development of a State-of-the-Art Dry Low NOx Gas Turbine Combustor for IGCC with CCS

“…This flashback tendency characteristic hinders the application of premixed combustion technology to A solution to these hurdles is to develop state-of-the-art technologies for diluent-free (dry), low NOx combustion of hydrogen-rich fuels. Many research groups and gas turbine manufacturers have been developing dry low NOx combustion technologies for hydrogen-rich fuels [6][7][8][9][10][11][12][13][14][15][16][17][18]. Technologies described in the literature include a multi-tube mixer fuel nozzle [7], a triple-fuel syngas burner [8], a MBtu EV burner [9], a low-swirl injector [10], a flameless-oxidation burner [11], a micro-mixing leanpremix injector [12], a DLN micromix burner [13,14], a DLE combustor with supplemental burners [15], a lean premixed swirl-stabilized hydrogen burner with axial air injection [16], a rich catalytic hydrogen injector [17], and a rich/lean staged burner [18].…”

“…Many research groups and gas turbine manufacturers have been developing dry low NOx combustion technologies for hydrogen-rich fuels [6][7][8][9][10][11][12][13][14][15][16][17][18]. Technologies described in the literature include a multi-tube mixer fuel nozzle [7], a triple-fuel syngas burner [8], a MBtu EV burner [9], a low-swirl injector [10], a flameless-oxidation burner [11], a micro-mixing leanpremix injector [12], a DLN micromix burner [13,14], a DLE combustor with supplemental burners [15], a lean premixed swirl-stabilized hydrogen burner with axial air injection [16], a rich catalytic hydrogen injector [17], and a rich/lean staged burner [18]. This chapter describes the development of a state-of-the-art dry low NOx combustor for hydrogen-rich syngas fuels in CCS-equipped oxygen-blown IGCC plants.…”