Jiale Cao, Xinyi Zhou, Run Chen, Shiyan Li, Sanghoon Kook, Tie Li
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引用次数: 0
摘要
了解撞击火焰的瞬态传热机制是进一步提高高效压燃(CI)发动机热效率的关键途径。本文在高压恒容容器中对撞壁火焰的瞬态传热进行了研究。在撞击壁上安装了快速反应热电偶,以记录瞬态热通量。采用双色高温计估算火焰区域内的平均温度。首先,研究了不同环境密度、氧气浓度、温度和喷射压力条件下的瞬态传热特性。将光学火焰速度计算方法应用于这一广泛的数据集,以建立 Nu 和 Re 之间的传热相关性,从而计算出瞬态传热系数,并将其与实验结果进行比较。分析结果表明,燃料喷射累积速度是表征贴壁火焰瞬态传热的新特征参数。结果表明,与环境气体条件相比,燃料喷射压力对热通量的影响更为显著,喷射压力越高,通过撞壁的热通量越高。将撞壁火焰的光学测量结果作为特征参数时,未发现瞬态 Nu 和 Re 有明显的线性趋势。相反,在撞壁火焰的瞬态传热过程中,燃料喷射累积速度与瞬态 Nu 和 Re 呈强烈的线性趋势。此外,新的累积燃料喷射速度得出的传热系数与实验结果非常吻合。
Characteristics of the transient heat transfer of impinging flames and correlation analysis using a new characteristic velocity under CI engine-like conditions
Understanding the transient heat transfer mechanism of impinging flames is a crucial pathway for further improving the thermal efficiency of already efficient compression ignition (CI) engines. In this paper, the investigation of the transient heat transfer of wall-impinging flames was performed in a high-pressure constant-volume vessel. Fast-response thermocouples were installed in the impinging wall to record the transient heat flux. Two-color pyrometry was employed to estimate the mean temperature inside the flame region. Firstly, the transient heat transfer characteristics were investigated under varied ambient density, oxygen concentration, temperature, and injection pressure conditions. The optical flame velocity calculation method was applied to this extensive dataset to develop a heat transfer correlation between Nu and Re with which transient heat transfer coefficients were calculated and compared with the experimental results. From this analysis, cumulative fuel injection velocity was developed as the new characteristic parameter to characterize the transient heat transfer of the wall-impinging flames. Results indicate that the effect of fuel injection pressure on the heat flux is more significant than that of ambient gas conditions, with higher injection pressure causing higher heat flux through the impinging wall. No obvious linear tendency of transient Nu and Re was found when using the optical measurement results of the wall-impinging flame as the characteristic parameter. Instead, the cumulative fuel injection velocity shows a strong linear trend of transient Nu and Re during the transient heat transfer processes of the wall-impinging flame. Moreover, the heat transfer coefficients from the new cumulative fuel injection velocity well fit the experimental results.
期刊介绍:
The Proceedings of the Combustion Institute contains forefront contributions in fundamentals and applications of combustion science. For more than 50 years, the Combustion Institute has served as the peak international society for dissemination of scientific and technical research in the combustion field. In addition to author submissions, the Proceedings of the Combustion Institute includes the Institute''s prestigious invited strategic and topical reviews that represent indispensable resources for emergent research in the field. All papers are subjected to rigorous peer review.
Research papers and invited topical reviews; Reaction Kinetics; Soot, PAH, and other large molecules; Diagnostics; Laminar Flames; Turbulent Flames; Heterogeneous Combustion; Spray and Droplet Combustion; Detonations, Explosions & Supersonic Combustion; Fire Research; Stationary Combustion Systems; IC Engine and Gas Turbine Combustion; New Technology Concepts
The electronic version of Proceedings of the Combustion Institute contains supplemental material such as reaction mechanisms, illustrating movies, and other data.