Abstract
Experimental studies are conducted to find an optimum size of the cavity flameholder, which is a new combustion concept of a turbine-based combined-cycle (TBCC) engine with an excellent flame stabilization. Besides, the effect of inlet pressure on the subatmospheric performance is investigated. The experimental results indicate that the increase of the cavity length improves the flame stability with an enlarged fuel/air mixture residence time, which suggests that the big length-height ratio in a proper range of the cavity with a stable dual-vortex should be chosen when designing the cavity-based combustor. In addition, the decrease in lean ignition and the lean blowout equivalence ratios can be attributed by either increase in the inlet pressure and temperature or decrease in the Mach number. The increase in inlet pressure will lead to a linear decrease in the lean blowout equivalence ratio with a slope of 0.66 per 0.1 MPa, whereas the lean ignition equivalence ratio has a rapid drop with the increase of pressure from 0.06 MPa to 0.08 MPa and reduces slowly with the growth of pressure in the range of 0.08 MPa to 0.1 MPa. The detailed analysis of the flow field indicates that the characteristic time-scale theory can ideally explain and predict the change of flame stability in the trapped vortex cavity.
Highlights
As a novel flameholder, the trapped vortex flame-stabilizing device is rarely investigated under a low pressure operating condition, which has a wider operating range than the conventional combustor flameholder, where there is a poor investigation as well
Two different experimental approaches are adopted in the investigation on the performance of flame stabilization to determine the optimum size and limits of the cavity for ignition and lean blowout under the low-pressure condition
The lean blowout equivalence ratio corresponds to the lowest fuel/air ratio at which point the flame disappears due to deceased fuel mass flow and cannot be reignited when increasing the fuel mass flow
Summary
The trapped vortex flame-stabilizing device is rarely investigated under a low pressure operating condition, which has a wider operating range than the conventional combustor flameholder, where there is a poor investigation as well. The efficient and reliable ignition and reignition, especially in high altitude conditions with thin oxygen and low temperature, are indispensable for the turbine-based combined-cycle (TBCC) engine augmentor [1]. Different from the conventional flamestabilizing mechanism of the bluff body, the ignition and flame stabilization are conducted in the located vortex which is trapped by the geometry of the cavity. As an advanced concept flameholder, the trapped vortex creates a recirculation zone with upstream fuel injection, in which the fresh fuel/air mixture is continuously ignited by hot combustion products. The secondary vortex protects the main vortex from being destroyed by the main flow, which can implement higher combustion efficiency and the lower LBO limits (~50%) than that in a conventional combustor [16, 17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
