Abstract
This paper focuses on a detailed numerical investigation combined with experimental research for a non-premixed swirl combustor, which aims to analyze the effects of the blade angle of the outer swirler and equivalence ratio on flow and combustion characteristics. In the experiment, the temperature in the furnace was obtained with a thermocouple, while a realizable k-ε turbulence model and two-step reaction mechanism of methane and air are used in the numerical method. The calculation results are in good agreement with the experimental data. The results reveal that the air flow rate through the swirler accounts for a small amount of the total air due to the influence of the draft fan, and there is no central recirculation zone (CRZ) despite the presence of the swirler. It was also found that NO emissions gradually decrease as the blade angle of the outer swirler increases. It was also indicated that the average temperature is 100 K higher than the general combustor with a 58° blade angle in the furnace by increasing the equivalent ratio of the tertiary air area, and the NO emissions reduced by approximately 25%. This study can provide guidance for the operation and structural design of non-premixed swirl combustors.
Highlights
The design of combustion systems can no longer be just about high efficiency and combustion stability, it should continue to be improved in response to the national call for ‘Energy Conservation and Emission Reduction’ in industry [1]
Zhou et al [12] studied the effect of primary air pipe on the combustion characteristics of a swirl burner, and the results indicated that, compared with the prototype swirl burner, the NOx emissions of the optimized burner decreased from 440 to 265 mg/m3 at 6% O2
Almeida et al [15] studied the influence of global equivalence ratio, Reynolds number, and swirler blade angle of a double-stage swirl burner on flow dynamics and emissions, and the results showed that the NOx emissions increased when the swirler angle increased
Summary
The design of combustion systems can no longer be just about high efficiency and combustion stability, it should continue to be improved in response to the national call for ‘Energy Conservation and Emission Reduction’ in industry [1]. The NOx emission is a critical factor of air pollution, and achieving low-NOx generation remains a challenge for different structures and operation schemes. Many of the ‘low NOx burners’ are based on swirl-stabilized flames. These burners achieve low NOx emissions through the appropriate design of the flame aerodynamics. Boushaki et al [11] investigated the dynamics of methane-oxygen turbulent non-premixed swirled flames and their emission characteristics with swirl numbers from 0.8 to 1.4, and the consequences indicated that
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