Optimization of flame stabilization methods in the premixed microcombustion of hydrogen–air mixture

Abstract

The premixed combustion of a lean hydrogen–air mixture is analyzed in this study to examine various properties and flame stabilization. A two‐dimensional (2D) analysis of a microscale combustor is performed with various shapes of bluff bodies (e.g., circular and triangular). Nine bluff bodies are placed at the entrance of the microscale combustor and solved with 2D governing equations. The analysis is performed with the three velocities of 10, 20, and 30 m/s, but the equivalence ratio is fixed in all cases. The various characteristics of the microscale combustor are studied such as the temperature of the wall, difference in peak temperature, the mean velocity at the outlet, and temperature of the exhaust gases. Flame stabilization depends on various factors such as bluff body shape and size, and the velocity of the fuel–air mixture at the inlet and recirculation zone. In comparison to all bluff body cases, we observe that the wall blade bluff body is the most efficient (low exhaust gas temperature, large recirculation zone, low mean velocity at the outlet of the microcombustor, and high wall temperature) compared with all eight other bluff body cases. Combustion efficiency is directly proportional to the wall temperature, meaning that the microcombustor with wall blade bluff bodies is more efficient with a stabilized flame. The simulation results are compared with published data on an L/D ratio of 15.

Experimental Research on an Afterburner System Fueled with Hydrogen–Methane Mixtures

“…A testing campaign was conducted in order to validate the proper functioning of a newly developed afterburner. Starting from a geometry of the afterburner presented in the patent [9] and previously developed and validated for use with natural gas as fuel, a new flame holder geometry was developed and tested. Two flame holder prototypes were manufactured, one through classic manufacturing techniques (P1) and one using additive manufacturing (P2).…”

“…The results show that a recirculation zone was formed in the conventional bluff body (CBB) micro-combustor, while two symmetric recirculation zones were formed in the slotted bluff-body (SBB) micro-combustor and controllable slotted bluff-body (CSBB) micro-combustor. The premixed combustion of a lean hydrogen-air mixture was analyzed [9] to examine various properties and flame stabilization. A twodimensional (2D) analysis of a microscale combustor was performed with various shapes of bluff bodies (e.g., circular and triangular) to characterize the combined effects of the bluff body, such as shape, size, and blockage ratio, on micro-combustors, playing a crucial role in enhancing flame stability, efficiency, and blow-out limit.…”

A Review on Flame Stabilization Technologies for UAV Engine Micro-Meso Scale Combustors: Progress and Challenges

“…To evaluate the combustion performance, various studies have been conducted on these configurations at different velocities and equivalence ratios. For example, a study on flame stabilization with bluff body and wall cavity has shown significant improvement in combustion efficiency [13]. Kang et al investigated the flame stability limits and thermal performance of a parallel plate combustor with orthotropic wall made of pyrolytic graphite, which exhibits a high velocity limit due to improved temperature distribution on the plate [24].…”

“…The inner recirculation zone enhances the mixing through swirl-like configurations and becomes effective in evaporating fuel, while the combustion becomes efficient due to the recirculation zone around the linear wall. In their investigation into flame stabilization, Jha et al explored several different factors, ultimately determining that using a bluff body is one of the most effective methods to stabilize flames [13]. The study was focused on optimizing geometry-based parameters to gain a better understanding of how to stabilize flames in narrow channels.…”

“…The investigation of micro combustion is also crucial for developing small UAV engines due to the complex flame instabilities that they exhibit. To address these instabilities, various flame stabilization methods have been explored, including the bluff body, swirler, counterflow stabilization, transverse flow, and two-stage flame stabilization [13]. Two-stage flame stabilization involves creating a stepped combustion channel coupled with a suitable stabilization method.…”