The Stabilization Characteristics and Reattachment Process of Lifted Diffusion Jet Flames Enhanced by Repetitive D C Electric Pulse Corona Discharges

  • 張 子威

Student thesis: Doctoral Thesis

Abstract

Among the recently prevailing flame stabilization enhancement by electric field and plasma repetitive D C electric pulse discharge is applied to a turbulent lifted diffusion jet flame to improve the reattachment limit in this study The present study demonstrates the feasibility of enhancement in lifted jet flame reattachment by applying a repetitive high-voltage pulsed DC discharge to a proposed electrode configuration To characterize experimentally the stability and the reattachment behaviors and process of lifted flames under the electric pulse effect with a proposed electrode configuration is the main objective The effects of pulse repetition frequency (PRF) and diverse voltage polarity on flame are investigated The result shows the reattachment velocity is enhanced more than double for positive polarity case with PRF of 1500 Hz as compared to the without discharge case According to the sequence high speed images the time history of flame base trace and displacement speed are presented and compared for 200 Hz and 1500 Hz cases under applying positive DC pulses Both processes could be divided into two different types of electrical discharge The electrical corona plasma is observed during upstream propagation process for both cases and it plays a key role in enhancing flame displacement speed Furthermore in order to reveal the gas velocity distribution for the complicated flame-flow interaction during rapid reattachment process a conditional particle image velocimetry (cond-PIV) measurement is used to analyze the detailed flame-flow interaction of complete reattachment process By simultaneously using shuttered PIV and high speed camera imaging to record the instantaneous planar gas velocity field measurement conditioned on high speed sequence images The results show that the instantaneous axial velocity is low and suitable for flame upstream propagation and reattachment Finally the conditionally instantaneous leading-edge propagation speed is enhanced and exceeds 3 times that of stoichiometric laminar flame speed for 1500 Hz case which leads to flame reattachment
Date of Award2018 Aug 31
Original languageEnglish
SupervisorYei-Chin Chao (Supervisor)

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