Effect of thermal non-equilibrium on supersonic combustion with low equivalence ratio

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-05-17 DOI:10.1016/j.combustflame.2025.114220

You Wu , Bing Chen , Qingchun Yang , Xu Xu

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Abstract

The distribution of the vibrational energy could have significant impact on ignition and flame stabilization in the scramjet combustor. The effect of thermal non-equilibrium on the non-premixed hydrogen/air supersonic combustion with a global equivalence ratio of 0.3 in scramjet is investigated using numerical simulations based on the thermochemical non-equilibrium model and the chemical non-equilibrium model. The results show that the cold vibrational non-equilibrium of the inflow enhances the ignition but inhibits the downstream heat release, while the thermal non-equilibrium caused by the transverse jet interaction has the opposite effect. The case with the real scramjet condition (NEQ_REAL) has the earliest ignition and the lowest downstream peak heat release rate (HRR). The internal energy distribution in the shear layer determines the control temperatures of the three key initial reactions and alters the formation rates of free radicals, which affects the ignition. The downstream peak HRR is related to the internal energy distribution and the species composition which is affected by the upstream thermal non-equilibrium. The local internal energy distribution in thermal non-equilibrium cases can promote the HRR compared to the “hypothetical” equilibrium state. The change of species concentration due to thermal non-equilibrium is the main reason why peak HRR of NEQ_REAL is lower than that of thermal equilibrium case. Using different chemical-vibrational coupling models has impacts on ignition and peak HRR. When the original Park model is used, the internal energy distribution in the thermal non-equilibrium case can reduce the heat release rate compared to the “hypothetical” thermal equilibrium state. The effect of thermal non-equilibrium in supersonic expansion flow is equivalent to heat absorption effect compared to the thermal equilibrium case, which reduces the pressure and translational temperature in the nozzle. The difference of net thrust between thermal equilibrium and non-equilibrium cases exceeds 10%.

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热不平衡对低当量比超音速燃烧的影响

振动能量的分布对超燃冲压发动机燃烧室内的点火和火焰稳定有重要影响。采用基于热化学非平衡模型和化学非平衡模型的数值模拟方法，研究了热不平衡对整体等效比为0.3的超燃冲压发动机非预混氢/空气超声速燃烧的影响。结果表明，流入流的冷振动不平衡促进了点火，抑制了下游热释放，而横向射流相互作用引起的热不平衡则起到相反的作用。实际超燃冲压发动机工况下（NEQ_REAL）的点火时间最早，下游峰值放热率（HRR）最低。剪切层的内能分布决定了三个关键初始反应的控制温度，改变了自由基的形成速率，从而影响了着火。下游的峰值HRR与内能分布和物种组成有关，而内能分布和物种组成受上游热不平衡的影响。与“假设”的平衡态相比，热非平衡状态下的局部内能分布可以促进HRR的提高。热非平衡状态下的物种浓度变化是NEQ_REAL的峰值HRR低于热平衡状态的主要原因。采用不同的化学-振动耦合模型对点火和峰值HRR有影响。当使用原始的Park模型时，与“假设”的热平衡状态相比，热非平衡状态下的内能分布可以降低热释放率。与热平衡情况相比，超音速膨胀流中的热非平衡效应相当于吸热效应，降低了喷管内的压力和平动温度。热平衡和非平衡情况下的净推力差超过10%。

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来源期刊

Combustion and Flame 工程技术-工程：化工

CiteScore

9.50

自引率

20.50%

发文量

631

审稿时长

3.8 months

期刊介绍： The mission of the journal is to publish high quality work from experimental, theoretical, and computational investigations on the fundamentals of combustion phenomena and closely allied matters. While submissions in all pertinent areas are welcomed, past and recent focus of the journal has been on: Development and validation of reaction kinetics, reduction of reaction mechanisms and modeling of combustion systems, including: Conventional, alternative and surrogate fuels; Pollutants; Particulate and aerosol formation and abatement; Heterogeneous processes. Experimental, theoretical, and computational studies of laminar and turbulent combustion phenomena, including: Premixed and non-premixed flames; Ignition and extinction phenomena; Flame propagation; Flame structure; Instabilities and swirl; Flame spread; Multi-phase reactants. Advances in diagnostic and computational methods in combustion, including: Measurement and simulation of scalar and vector properties; Novel techniques; State-of-the art applications. Fundamental investigations of combustion technologies and systems, including: Internal combustion engines; Gas turbines; Small- and large-scale stationary combustion and power generation; Catalytic combustion; Combustion synthesis; Combustion under extreme conditions; New concepts.