Combustion Instability of Swirl Premixed Flame with Dielectric Barrier Discharge Plasma

Kai Deng,Yi Zhong,Yingjie Zhong,Jinlin Hu,Shenglang Zhao,Chenyang Xue

doi:10.3390/pr9081405

Abstract

The effects of plasma on the combustion instability of a methane swirling premixed flame under acoustic excitation were investigated. The flame image of OH planar laser-induced fluorescence and the fluctuation of flame transfer function showed the mechanism of plasma in combustion instability. The results show that when the acoustic frequency is less than 100 Hz, the gain in flame transfer function gradually increases with the frequency; when the acoustic frequency is 100~220 Hz, the flame transfer function shows a trend of first decreasing and then increasing with acoustic frequency. When the acoustic frequency is greater than 220 Hz, the flame transfer function gradually decreases with acoustic frequency. When the voltage exceeds the critical discharge value of 5.3 kV, the premixed gas is ionized and the heat release rate increases significantly, thereby reducing the gain in flame transfer function and enhancing flame stability. Plasma causes changes in the internal recirculation zone, compression, and curling degree of the flame, and thereby accelerates the rate of chemical reaction and leads to an increase in flame heat release rate. Eventually, the concentration of OH radicals changes, and the heat release rate changes accordingly, which ultimately changes the combustion instability of the swirling flame.

Highlights

As high-tech power machinery, gas turbines occupy an important position in industrialized fields such as power generation and propulsion [1]
In 2015, Kim et al [5] studied the application of plasma in a methane premixed flame, and the results showed that plasma can assist in the control of combustion kinetics, and its effect is closely related to the flame shape
The effects of acoustic frequency on combustion instability are seen when the acoustic frequency is less than 100 Hz, and the gain gradually increases with the acoustic frequency; when the acoustic frequency is between 100 and 220 Hz, and the gain in flame transfer function tends to decrease first and increase with the acoustic frequency; when the frequency is greater than 220 Hz, and the gain gradually decreases with the acoustic frequency

Summary

Introduction

As high-tech power machinery, gas turbines occupy an important position in industrialized fields such as power generation and propulsion [1]. In order to further verify and analyze the effect of plasma on the instability of a swirling premixed flame, an experimental system for plasma of a dielectric barrier discharge nonthermal plasma reaction device was created to act on a methane swirling flame under acoustic excitation. The pressure and heat release rate were measured simultaneously through dual microphones and photomultiplier tubes, obtaining the influence of dielectric barrier discharge plasma on the instability of a methane swirling flame under different acoustic frequencies. Based on a planar laser-induced fluorescence (PLIF) system, the flame structure capture technology was applied to measure OH radical concentration and other experimental methods were used to further analyze the mechanism of dielectric barrier discharge plasma on the stability of a swirling premixed flame. The heat release rate of the swirling flame is measured by a photomultiplier tube (R928 type, Hamamatsu, Japan) with a narrow band pass filter (315 nm, Semrock, Rochester, NY, USA)

Experimental Conditions

The Effects of Discharge Frequency on Flame Transfer Function

Conclusions