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Ethanol Inhomogeneous Lean Combustion Under Different Ambient Temperatures and Pressures with Hydrogen Enrichment

COMBUSTION SCIENCE AND TECHNOLOGY 2025年第8期197卷 1739-1759页

作者： Ge, Ruihan Hu, Erjiang Lv, Xin Tang, Chenglong Huang, Zuohua Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The effects of different ambient temperatures and pressures on the combustion of hydrogen-enriched liquid ethanol spray were studied in a constant-volume vessel, using experimental and numerical methods. The inhomogeneous combustion experiment was conducted under ultra-lean conditions at an overall equivalence ratio of 0.3 (33% spray ethanol/67% premixed hydrogen). The spray and flame images and combustion pressures were obtained. The spray simulation models used were the RANS k-epsilon turbulence model, KH-RT model, and wall film interaction model. The experimental results showed that the inhomogeneous combustion of the liquid ethanol spray can be divided into two stages: a rapid-burning and a slow-burning stage. The slow-burning stage was sensitive to changes in ambient temperature and pressure. Combustion duration decreased with elevated pressure and declined temperature. Under low pressure and medium temperature conditions, the flame reached its fastest propagation speed. The simulation results showed that the fuel concentration and concentration gradient around the ignition position are the key factors that affect inhomogeneous lean combustion. When the equivalence ratio was over 0.8 around the ignition position and the gradient of the equivalence ratio increased no less than 0.1/mm, the optimal combustion characteristics were achieved.

关键词： Inhomogeneous combustion direct injection hydrogen enrichment constant volume vessel spray simulation

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Effect of ignition timing on the combustion characteristics of liquid ammonia spray in a lean premixed H2/Air

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COMBUSTION AND FLAME 2025年 274卷

作者： Ge, Ruihan Yin, Geyuan Hu, Erjiang Shen, Shujie Zhan, Haochen Tang, Chenglong Huang, Zuohua Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Peoples R China

Combustion of ammonia has recently been emerging as a promising approach for carbon mitigation. However, monitoring ignition of ammonia is a technique challenge due to its low reactivity. This work experimentally investigates the ignition and combustion behaviors of ammonia spray injected into a lean hydrogen air mixture, with emphasis on the ignition timing effect on the ignition and flame evolution behaviors as well as the pressure evolution and heat release. Results show that the ignition timing leads to profound alteration of the ammonia spray ignition and flame evolution due to the mixture status induced by different spray evolution time. Specifically, the flame is the most significantly affected by spray injection at ignition timings close to the start and end of injection and the heat loss is reduced, compared with the premixed fuel due to the lower heat release from evaporation and incomplete combustion. Additionally, for 10 ms pre-ignition timing, at the instant when the spray reaches the flame, the unburned gas assists in the evaporation and diffusion of the liquid ammonia, leading to a sudden increase in flame speed and a higher pressure of combustion. While, finally, for the 10 ms postignition timing case, the stratified fuel concentration distribution leads to accelerated heat release rate and a reduced overall combustion duration. The special spray characteristics of liquid ammonia and the high latent heat of evaporation are the main factors leading to the reduction of the combustion efficiency of liquid ammonia spray, which can be effectively solved by precombustion heating or homogeneous mixing. This study is believed to be beneficial for organizing better combustion for this zero-carbon fuel in SI engines.

关键词： Liquid ammonia Spray combustion Hydrogen Ignition timing

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Investigation on intermittent flow characteristics in horizontal pipe by visualization measurement method

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2025年 160卷

作者： Huang, Bo Xu, Qiang Cao, Yeqi Yu, Haiyang Li, Yuwen Chang, Yingjie Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Accurate measurement and prediction of the intermittent flow characteristics in horizontal pipes is important for constructing multiphase flow models and ensuring pipe flow safety. In this paper, a quantitative image post- processing technique for intermittent flow characteristics based on gray histogram image similarity is proposed, which can realize the measurement of slug frequency. In addition, the technique also has the ability to classify a large number of images, and can quickly find the elongated bubble head, liquid film area and liquid slug area of intermittent flow. On the basis of this technique, combined with image post-processing methods such as gas-liquid interface feature analysis, a set of intermittent flow image processing technique with perfect route is formed. Based on this post-processing technique, the similarity image oscillation trajectories of plug flow and slug flow are obtained. There are differences in the similarity image oscillation trajectories of the two intermittent sub-flow patterns, and the similarity image of the plug flow has an obvious platform period and trailing rising line, which can be used as a basis for the classification of the two intermittent sub-flow patterns. A correlation for predicting the slug frequency of intermittent sub-flow patterns is developed. The accuracy of this slug frequency prediction correlation can be improved by about 10% compared to not dividing the sub-flow patterns. When the mixture Froude number Frm m is less than 5.0, the radial position of the elongated bubble head decreases linearly as the Frm m increases. When the Frm m is greater than 5.0, the elongated bubble head oscillates near the middle of the pipe. Prediction correlations for the radial position of the elongated bubble head and the slug velocity are established separately, and the maximum error is +/- 10 %. The modified mixed Froude number is proposed, and based on this, a new prediction model for the transition from plug flow to slug f

关键词： Intermittent flow flow visualization Quantitative image processing flow characteristics flow pattern transition

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Multi-objective topology optimization design of liquid-based cooling plate for 280 Ah prismatic energy storage battery thermal management

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ENERGY CONVERSION AND MANAGEMENT 2025年 325卷

作者： Lin, Xiang-Wei Shi, Ming-Yu Zhou, Zhi-Fu Chen, Bin Lu, You-Jun Jing, Deng-Wei Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Developing energy storage system based on lithium-ion batteries has become a promising route to mitigate the intermittency of renewable energies and improve their utilization efficiency. In this context, thermal management is needed to maintain battery temperature and thermal uniformity without consuming significant power. However, conventional cooling plates are usually built via trial-and-error methods, which suffer from trade-off problem between thermal performance and flow resistance. In this study, a multi-physics model incorporating electrochemical, hydrodynamic, and thermal fields is proposed for a battery pack. Meanwhile, a multi-objective topology optimization is introduced to freely evolve the distribution of fluid domain embedded into cold plate under specified constraint conditions. The multi-objective function is formulated using normalized additive weighting approach. Based on this, the mapping relations between design parameters (i.e., Reynold number and weighting coefficients) and performance of cold plate can be established via response surface method, and it is further optimized with a non-dominated sorting genetic algorithm. Results show that topological channel structure performs lower average temperature rise than traditional straight, serpentine, and hexagonal cold plates. When the mass flow rate ranges from 1 x 10-3 to 15 x 10-3 kg s- 1, Nusselt number difference are varied from 1.33 to 5.90 compared to straight cold plate, which are improved by 15.6 to 42.2 %, respectively. This indicates that optimized cold plate achieves better heat exchange ability under the same inlet conditions. Besides, optimal design allows for excellent thermal uniformity without excessive pressure drop compared to serpentine cold plate.

关键词： Battery energy storage system Thermal management Topology optimization Liquid cooling plate

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Gas-liquid flow rates measurement based on dual differential pressures of a power-driven swirler

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MEASUREMENT 2025年 242卷

作者： Wang, Haocun Xu, Qiang Zhang, Xuemei Ma, Xiaojun Li, Lulu Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

In recent years, swirlers have gained increasing attention in gas-liquid flow rates measurement. A power-driven swirler device is designed suitable for low gas-liquid flow rates conditions. Variation characteristics of swirler differential pressure (Delta Ps) and radial differential pressure (Delta Pr) are investigated under three swirler rotational speeds (0, 300, and 600 rpm). An average reduction of 9 % and 15 % can be seen in fluctuations of Delta Ps and Delta Pr signals, respectively. Wider measurement range can be achieved by increasing the rotational speed, the minimum liquid superficial velocity decreases from 1.53 m/s to 1.02 m/s and the maximum gas volume fraction increases from 41.8 % to 51.9 %. Then, a new gas-liquid flow rate measurement model is established considering the gas-liquid slip and interfacial interaction. As the rotational speed increases from 0 to 600 rpm, the relative errors of liquid and gas mass flow rates decrease from + 3.4 % to + 2.7 % and + 24 % to + 10 %, respectively.

关键词： flow rate measurement power-driven swirler Differential pressure Gas-liquid two-phase flow

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Thermodynamic and environmental analysis of the hydrogen and combustible gas production in supercritical water partial oxidation system of coal

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ENERGY 2025年 326卷

作者： Li, Yifeng Xing, Guowei Liu, Shi Guo, Shenghui Ge, Zhiwei Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Supercritical water partial oxidation (SCWPO) is an eco-friendly coal treatment technology that lowers the temperature needed for complete coal gasification, promotes hydrogen output, enables targeted regulation of gaseous product composition, and eliminates gaseous pollutants. Current researches mainly focus on experiments and numerical simulations, with limited exploration in thermodynamics. The present study establishes an autothermal SCWPO cogeneration system for Hongliulin coal, employs sensitivity analysis to refine system parameters, and utilizes Life Cycle Assessment to evaluate the environmental impact of the hydrogen production system. When the outlet temperature of the SCWPO reactor increases, the preheating water flow and equivalence ratio (ER) enhance, the fraction of H2 in the gas product rises;conversely, the fraction of the combustible gas (CH4+CO + H2) rises. The SCWPO system can be precisely tailored to yield high-purity hydrogen or combustible gas by modulating the amount of oxygen input. The system of combustible gas production is capable of generating 241.67 GJ h- 1 of energy and attaining a cold gas efficiency of 81.62 % when the ER is 0.25. The hydrogen production system can generate 1004.38 kg h- 1 of H2 and 206 t h- 1 of steam at 0.5 MPa and 150 degrees C for an ER of 0.6. The optimized hydrogen production system achieved 90.97 % energy efficiency and 59.33 % exergy efficiency. The standard Global Warming Potential through carbon capture technology is 0.087 (kg H2)- 1. The system developed in this paper benefits the industrial application of SCWPO and the optimization of subsequent processes.

关键词： Thermodynamic analysis Supercritical water partial oxidation Life cycle assessment Efficiency enhancement Hydrogen production Combustible gas

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Three-dimensional dynamic multi-physics modeling and long-term degradation performance analysis of solid oxide fuel cell considering carbon deposition

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JOURNAL OF power SOURCES 2025年 631卷

作者： Li, Bohan Wang, Chaoyang Liu, Chang Liu, Ming Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Carbon deposition is a critical issue in solid oxide fuel cell (SOFC) operations. In this study, a 3D dynamic model of SOFC considering carbon deposition is established and validated to investigate the effects of key operating conditions (i.e., output voltage, operating temperature, and fuel composition) on the long-term power degradation of the cell. Additionally, the total working lifecycle power generation (Ptot) of the cell is calculated for methane molar fractions in the feeding fuel (XCH4) ranging from 0.1 to 0.4, output voltages (U) from 0.6 V to 0.8 V, and operating temperatures (T) from 1003 K to 1043 K. The results indicate that the long-term SOFC operating voltage should exceed the voltage for maximum steady-state power output to achieve higher Ptot. When the power degradation threshold (PDT) equals 0.75, Ptot reaches 2880 kW h/m2 at U = 0.75V, approximately twice that at U = 0.55V. The power degradation process of the cell can be divided into two stages: a rapid degradation stage and a slow degradation stage. Decreasing the operating temperature or reducing XCH4 to regulate PDT to the slow degradation stage can significantly enhance the cell's total working lifecycle power generation. A distinct boundary in X CH4 is observed between high and low P tot . When X CH4 exceeds the boundary value (0.25), the cell's P tot decreases by over 70 %.

关键词： Solid oxide fuel cell 3D dynamic model Direct internal reforming Carbon deposition

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Numerical simulation of closed-cycle R410A flash spray cooling with multiple nozzles on a large heat exchange surface

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APPLIED THERMAL ENGINEERING 2025年 268卷

作者： Yang, Wenbo Sang, Xuehao Chen, Bin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

To address the heat dissipation of high-power chips with large heat exchange surfaces, a mathematical model of a multi-nozzle R410A closed flash evaporation spray cooling system was established based on the Euler-Lagrange method to investigate the effects of nozzle number, nozzle distance, spray angle, refrigerant mass flow rate, and spray distance on heat transfer efficiency. In the single-phase stage and two-phase stage, the optimal numbers of nozzle are 2 and 4, respectively. The optimal values for nozzle distance, spray angle, refrigerant mass flow rate, and spray distance are 7.5 mm, 30 degrees, 6 g/s, and 25 mm, respectively, with an average heat exchange surface temperature of 318.6 K. The dimensionless number Sw is proposed to describe the relationship between nozzle spacing, spray distance, and heat exchange area, with an optimal value of 1.0.

关键词： Spray cooling Multi-nozzle optimization Numerical calculation R410A Heat flux density

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Morphological and mechanistic study of a continuous flash boiling liquid ammonia spray

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PHYSICS OF FLUIDS 2025年第1期37卷

作者： Liu, Jiawen Zhang, Meng An, Zhenhua Chen, Jian Wang, Jinhua Tang, Chenglong Huang, Zuohua Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

As a zero-carbon fuel with superior properties, ammonia has attracted much attention from the combustion industry in recent years. In ammonia combustion for gas turbines (GTs), direct combustion of liquid ammonia (LNH3) is considered a way to increase power, simplify the system, and reduce energy consumption. However, due to the low boiling point and high vaporization latent heat of ammonia, LNH3 is prone to flash boiling under GT conditions, leading to significant changes in its spray characteristics. The current understanding of such a special spray is still insufficient. In this paper, particle droplet image analysis, Mie scattering, and thermocouple temperature measurement were conducted for continuous flash LNH3 spray in normal pressure. Furthermore, large eddy simulation was carried out. The quantitative characterization and detailed study of its spray morphology, parameter distribution, mass transfer, and heat transfer process were investigated. Combining this with the evaporation process, the formation reason for its spray morphology was explained, and suggestions for optimizing the combustion organization of the flash boiling spray were given. The results show that the spray angle theta decreases rapidly from 86 degrees to about 10 degrees, the spray SMD is 16 mu m and the diameter spatial distribution is uniform. The spray temperature is 238.1 K at the nozzle exit, which is lower than the boiling point (239.8 K), and subsequently drops to approximately 209 K downstream the spray. The bubble behavior inside the nozzle and the gas diffusion in the near field of spray led to the expansion of near-field spray, and further changed the nozzle characteristics. The spray can be divided into three regions: Spray-core-region, Spray-main-region, and Spray-edge. The extremely high concentration of gaseous ammonia in Spray-core-region significantly deteriorates evaporation. The difference of droplet velocity and evaporation ability between Spray-main-region and Spray-e

关键词： Thermocouples

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Experimental study on water boiling heat transfer characteristics of microchannel surface in distributed jet array impingement with effusion slots

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INTERNATIONAL JOURNAL OF HEAT AND FLUID flow 2025年 112卷

作者： Tang, Xiaoyu Xu, Qiang Yu, Haoyuan Pei, Chenyu Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Distributed jet array impingement can improve the uneven temperature distribution and achieve high heat flux cooling. This paper experimentally investigated the two-phase heat transfer and pressure drop characteristics in a distributed jet array impingement on the microchannel surface. The test operating conditions were mass flux of 100 200 kg/m2s, subcooling degree of 20 40 K, jet-to-target spacing of 2 4 mm, and atmospheric pressure at the outlet. The experimental results show that lowering subcooling from 40 K to 20 K enhances the heat transfer coefficient between 45.4 % and 57.2 % and a growth in the average pressure drop of 25.5 %. Increasing mass flux causes inlet and outlet pressure to fluctuate more sharply due to enhanced condensation. The pressure drop of single-phase forced convection and that of two-phase nucleated boiling display an opposite trend as mass flux increases. Reducing jet-to-target spacing to 2 mm exhibits a noticeable enhancement in pressure drop of more than 2.5 times, and the standard deviation of inlet pressure declines instead, indicating that decreasing jet- to-target spacing can attenuate flow instability. The coefficient of performance can be raised by increasing subcooling and jet-to-target spacing and reducing mass flux in the whole heat flux range. Expanding jet-to-target spacing from 2 mm to 4 mm can produce 105.5 % to 141.7 % higher the average coefficient of performance.

关键词： Distributed jet array impingement Microchannel surface Heat transfer Jet-to-target spacing Coefficient of performance

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