Fan, Huanbao; Feng, Junxiao; Bai, Wei; Wang, Hui; Akkurt, Nevzat; Li, Weidong; Gao, Jun; AliAkbaria, Omid; Xu, Qian

Based on the theory of moderate or intense low-oxygen dilution (MILD) combustion, a 3D steady-state CFD model coupling dual flue gas recirculation and dispersion combustion was developed to describe the flow field, combustion temperature field, wall temperature distribution, and NOx concentration field during the operation of a novel U-type radiant tube (N-URT). A user-defined function (UDF) method was implemented to simulate the dilution of O2 concentration in the combustion air due to external flue gas recirculation (E-FGR). The effects of the E-FGR ratio on combustion characteristics and NOx emission were evaluated. The simulated results were consistent with experimental results. The simulated NOx concentration at the outlet was reduced to 105.5 mg/m3 at 8% O2, which was about 35.2% lower than the conventional combustion method. The study found that when the E-FGR ratio was increased from 0 to 25%, the standard deviation of wall temperature decreased from 30.3 °C to 23.3 °C, and the non-uniformity coefficient decreased from 0.2598 to 0.2183, indicating an improvement in temperature uniformity. However, the thermal efficiency decreased from 82.1% to 76.2%. Moreover, at higher E-FGR ratios, the volume of the high-temperature region (above 1500 ℃) gradually decreased, and both the maximum flame temperature and the outlet NOx concentration decreased sharply. Regression equations for the E-FGR ratio (β) on the maximum combustion temperature (Tmax) and the outlet NOx concentration (CNOx) were obtained, and an E-FGR ratio greater than 13.4% was recommended to meet the emission requirements.

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Fan, Huanbao; Feng, Junxiao; Bai, Wei; Wang, Hui; Akkurt, Nevzat; Li, Weidong; Gao, Jun; AliAkbaria, Omid; Xu, Qian

The authors regret to inform that Table 1 in the final (citable) version of our article [Fuel 346 (2023) 128321] published in Fuel has a serious error; some key data in Table 1 (page 4, Section 2.2) corresponded incorrectly to variables. This was mainly due to our carelessness and was not caught in time while reviewing proofs for our publications. The correction is necessary to improve the academic accuracy of the article and for ease of reference for the readers. We are therefore publishing this correction. Specifically, the pre-exponential factor Ar and activation energy Ea of 2CO + O2 → 2CO2 should be 2.239 × 1012 1/s and 1.7 × 108 J/kg·mol, respectively. The pre-exponential factor Ar and activation energy Ea of 2H2 + O2 → 2H2O should be 9.87 × 108 1/s and 3.1 × 107 J/kg·mol, respectively. Thank you for your understanding and the previous efforts of all the reviewers and editors. Reference [1] Huanbao Fan, Junxiao Feng, Wei Bai, Hui Wang, Nevzat Akkurt, Weidong Li, Jun Gao, Omid AliAkbaria, Qian Xu, A study on the combustion performance and NOx emissions characteristics of a novel U-type radiant tube based on MILD combustion theory, Fuel 346 (2023) 128321. DOI: https://doi.org/10.1016/j.fuel.2023.128321. The correct version of Table 1 is as follows: The authors would like to apologise for any inconvenience caused.

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