Nitric oxide emission reduction and thermal characteristics of fuel-pulsed oscillating combustion in an industrial burner system

An experimental study was conducted on the effects of non-oscillating and oscillating combustions on nitric oxide (NO)-emission reduction and heat-transfer enhancement in an industrial low-NOx burner for reheating furnaces. Natural gas was periodically supplied by an oscillating control valve equipped with a rotary-type disk generating an oscillating fuel flow inside the furnace. The furnace temperatures and gas-species concentrations were measured for non-oscillating and oscillating combustions with the oscillating-frequency and duty ratio in the ranges of 1-5 Hz and 10-40%, respectively. The flame sizes in oscillating combustion increased (decreased) under a fuel-rich (fuel-lean) combustion condition, corresponding to the oscillating fuel-flow rates. The NO-reduction efficiency of the oscillating combustion increased as the oscillating frequency (Hz) decreased and as the duty ratio (%) increased in contrast to the non-oscillating combustion. The maximum NO reduction was-32% under the 1 Hz/40% oscillating combustion. Although the peak temperature was lower in the oscillating combustion than in the non oscillating combustion, the overall temperature distribution in the oscillating condition was higher than that in the non-oscillating combustion. Thus, the oscillating combustion improved the furnace-heating performance by-9.8%. Consequently, it effectively facilitated NO-emission reduction and heat-transfer enhancement simultaneously. (C) 2020 Elsevier Ltd. All rights reserved.