Abstract
A new pressurized vitiated co-flow burner (PVCB) was designed and built for the investigation of lifted flame properties and was supported by a vitiated co-flow of hot combustion products from a lean H2/air flame at a controllable pressure; its preliminary application for a methane lifted flame was tested. The distribution of the co-flow temperature, oxygen mole fraction, flow rate, and pressure of the PVCB was measured and calculated. The research results show that the co-flow temperature range is from 300 to 1300 K, the background pressure range is from 1 to 1.5 bar, the stable temperature field of the PVCB is wider, and the background pressure of the PVCB can be controlled. The simulation results show that the PVCB provides a controllable, pressurized co-flow of hot and vitiated gases, which makes it possible to investigate flame stabilization mechanisms. The PVCB has the advantages of controllable background pressure and a stable temperature field. The well-defined uniform boundary conditions and simplified flow of the PVCB simplify the establishment of a numerical model and decouple the turbulent chemical kinetics from the complex recirculating flow. It can be widely used in the research on lifted flames. A lifted flame of methane was recorded under conditions of a co-flow temperature of 1133 K and pressure from 1 to 1.043 bar. The lift-off height decreased and stabilized with the increase in the background pressure. The laminar flame speed and the autoignition delay time were tested and simulated at the same time by Chemkin; the influence of background pressure on the lift-off height, laminar flame speed, and autoignition delay were analyzed. The results show that the autoignition, as well as the flame propagation, dominated the stabilization mechanism of the lifted flame in the PVCB.
Highlights
A turbulent jet flame is a typical turbulent combustion mechanism in internal combustion engines and gas turbines, and it is a fundamental topic in combustion science
The results indicated that the lifted flame stability is controlled by spontaneous fuel combustion and turbulent flame propagation at different temperature ranges
The co-flow of the pressurized vitiated co-flow burner (PVCB) presents an active pressurized thermo-atmosphere, which can be adjusted by changing the equivalence ratios (ERs) of the premixture (H2 /air)
Summary
A turbulent jet flame is a typical turbulent combustion mechanism in internal combustion engines and gas turbines, and it is a fundamental topic in combustion science. The stability of turbulent jet flames is very important for turbulent combustion design, concerning its safety, efficiency, and emission control. Once the flame is lifted, the position of the flame base is mainly determined by the balance between the jet velocity and the burning velocity, while a possible mechanism that can prompt flame stability is autoignition [3]. Finite-rate chemistry effects and highly complex interactions between chemistry and turbulence at the flame make the accurate modeling of jet flame stabilization a fairly challenging task. The investigation of turbulent jet flame stability in a hot environment and combustion products will be useful for improving combustion technology. It is very important to study the autoignition of jet fuel and the stabilization mechanism of the lifted flame in hot co-flow in order to provide an experimental
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