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Exploration of the Responsiveness of the Atomization Field in a Centrifugal Nozzle to Variations in Inlet Pressure

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SSRN 2023年

作者： Xu, Wen Yang, Jianwen Yang, Bin Wang, Ying Shanghai Key Laboratory of Multiphase Flow and Heat Transfer of Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China Xi’an Aerospace Propulsion Institute Xi’an710100 China

As the crucial atomization unit in the propellant supply system for liquid rocket engines, the centrifugal nozzle's atomization performance is of paramount importance. However, due to flow oscillations within the propellant supply system, the resulting spray from nozzle atomization tends to oscillate, adversely impacting fuel atomization efficiency. This paper employs a VOF-to-DPM multiphase flow model to simulate the nozzle's atomization field under different inlet pressures, which is subsequently compared with experimental results. Next, the UDF is used to introduce pressure pulsation sources with varying frequency sizes at the nozzle inlet, from which the following conclusions are drawn: (1) The numerical simulation-derived atomization angle of the nozzle under different inlet pressures slightly deviates below the experimental value, but consistently maintains a similar trend, with errors not exceeding 5%;(2) Under constant inlet pressure, the nozzle's atomization field exhibits a stable, smooth, hollow cone liquid film formation, and particle droplets produced by liquid film atomization coalesce at the hollow cone's lower end;(3) When pressure pulsations with diverse frequencies and magnitudes are loaded at the nozzle inlet, the atomization field undergoes varying degrees of oscillation. When f = 100 Hz, the hollow cone liquid film disappears completely after undergoing initial formation during a pulsation cycle, and the atomized particles' number experiences the most significant change relative to constant inlet pressure. When f = 400 Hz, the broken droplets gradually reform the hollow cone liquid film within a pulsation period and maintain its form but undergo subsequent breaking. When f = 800 Hz, there is no apparent alteration in the shape of the hollow cone liquid film or total particle count during a pulsation cycle. However, the liquid film's surface appears uneven, showing wavy water marks. © 2023, The Authors. All rights reserved.

关键词： Atomization

Analysis of Different Control Strategies Considering Individual Regulation of Heat User

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Analysis of Different Control Strategies Considering Individ...

Electrical engineering and Mechatronics Technology (ICEEMT), IEEE International Conference on

作者： Zhiwei Xun Huijie Wang Liyuan Wang Long Yang Yunfang Gao Ming Liu Guoneng Jinjie Energy Co. Ltd Yulin China Xi’an Jiaotong University Xi’an China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

In the process of outdoor temperature change, it is beneficial to improve the comfort of thermal users to formulate adjustment and control strategies according to the actual needs of each user. In this paper, different adjustment modes are established according to the thermal comfort of users, and the control strategies of rising and cooling within 0, 30 and 60 minutes are proposed, and the indoor temperature control effect and heating energy consumption of each adjustment mode under different control strategies are analyzed. The results show that: in different modes, when the rise and cooling time increase, compared with the design room temperature, the indoor temperature difference under the control mode is smaller, but the time needed to reach stability is longer. At the same time, the total heat load is unchanged, but the total pump work decreases.

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On Accelerative Propagation of Premixed Hydrogen/Air Laminar and Turbulent Expanding Flames

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SSRN 2022年

作者： Zhao, Haoran Wang, Jinhua Cai, Xiao Dai, Hongchao Liu, Xiao Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong Universit Xi’an710049 China College of Power and Energy Engineering Harbin Engineering University Harbin150001 China

The accelerative propagation of laminar and turbulent premixed hydrogen/air flames are investigated using a constant volume combustion chamber. Turbulent burning velocity ( S T ) of hydrogen/air mixtures are determined in a wide range of conditions, more importantly the flame propagation dynamics and acceleration exponents are analyzed in detail. Results show that three distinct stages, namely quasi steady, transition acceleration and saturation acceleration stages are distinguished in laminar flame propagation process, and transient acceleration exponent ( a R ) increases in transition acceleration stage while nearly remains as a constant between 1.1~1.25 in saturation acceleration stage. Turbulent flame propagation follows a self-similar acceleration law, and transient acceleration exponent increases continuously as flame propagates outwardly. Furthermore, the empirical correlatio n is obtained to describe the development of turbulent flame acceleration with flame radius. Additionally, global acceleration exponents ( a ) of turbulent flames increase continuously with u ’ / S L and no significant trend variation occurs in different regimes. It appears that the accelerative propagation of turbulent expanding flames is mainly controlled by turbulence stretch, while the effect of flame intrinsic instability is nearly covered in current study. © 2022, The Authors. All rights reserved.

关键词： Acceleration

Numerical Study on the Effect of Rim Seal Slot Filleting on Turbine Endwall Cooling Performance

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SSRN 2023年

作者： Shi, Liuliu Di, Wentao School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Key Laboratory of Power Machinery and Engineering Ministry of Education Shanghai Jiao Tong University Shanghai200240 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

In the present study, the effect of rim seal slot filleting on turbine endwall cooling performance is numerically investigated. Based on validation of the numerical method, the Reynolds-averaged Navier-Stokes (RANS) equations combined with the standard turbulence model are adopted in this study. For comparison with the baseline case, five different fillet radii are adopted, i.e. R/W=1.25, 2.5, 3.75, 5 and 6.25. The results indicate that the overall film cooling effectiveness on the turbine endwall can be improved by up to 10% with smaller fillet radii. However, this effect diminishes as the fillet radius increases and it becomes negative at R/W=6.25. By examining the contours of the endwall film cooling effectiveness in filleted cases with the baseline, a prominent strip can be observed across the blade passage. This reveals that the primary contributor to the variation of the film cooling performance is the pressure-side leg horseshoe vortex. Besides, the film cooling effectiveness is slightly improved near the suction side of the leading edge owing to the suppression of endwall separation at this area. The rim seal slot filleting eliminates the slot leakage separation, which in turn speeds up the endwall coolant flow. Ultimately, this weakens the pressure-side leg horseshoe vortex and subsequently enhances the film cooling performance. As the fillet radius continues to increase, the through-flow area for the coolant flow enlarges, resulting in a gradual decrease in film cooling performance. © 2023, The Authors. All rights reserved.

关键词： Turbulence models

Numerical Study of High-Energy Spark Ignition Characteristics in a Scramjet Combustor

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SSRN 2024年

作者： Gao, Ziyan Zhang, Meng Zhang, Zhibo Wu, Yun Zheng, Xing Miao, Huifeng National Key Lab of Aerospace Power System and Plasma Technology Xi’an Jiaotong University Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong Universiy Xi’an710049 China National Key Lab of Aerospace Power System and Plasma Technology Air Force Engineering University Xi’an710038 China Shaanxi Key Laboratory of Environment and Control for Flight Vehicle School of Aerospace Engineering Xi’an Jiaotong University Shaanxi 710049 China

Reliable ignition is a fundamental prerequisite for the scramjet engines. In order to improve the reliability of ignition, further enhance the application of spark ignition in engineering, and improve the ignition ability in the field of supersonic combustion, an innovative long electrode distance high-energy spark igniter (LHSI) system was proposed by our research team. To reveal the instantaneous ignition characteristics of the LHSI, a simulation model of the LHSI is established and verified by experiments. Based on this, the formation and development of the initial fire core of vaporized kerosene and the ignition characteristics of LHSI in a scramjet combustor were simulated and compared with the conventional high-energy spark igniter (HSI). The analysis revealed that the success of the cavity ignition is greatly influenced by the local equivalent ratio of the initial flow field and the penetration depth of the initial flame core. Meanwhile, the fore recirculation zone of the cavity plays a key role in stabilization and development of the initial fire core. Compared with the HSI, the LHSI can produce initial flame core with higher penetration and greater size, which is the main reason for why LHSI has a broader ignition boundary. © 2024, The Authors. All rights reserved.

关键词： Ignition

Thermal-Mechanical Influence Aspects and Evaluation of Helical Cruciform Single Rod in Fluoride-Salt-Cooled High-Temperature Advanced Reactor

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SSRN 2024年

作者： Chen, Yiwen Zhang, Dalin Jiang, Dianqiang Li, Wei Wu, Xiaoli Tian, Wenxi Qiu, Suizheng Su, Guanghui Lu, Qi State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi’an Jiaotong University Xi’an710049 China Science Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China China

Helical cruciform fuels are novel in nuclear reactors, potential to increase reactor’s power density. However, the geometry is complicated so influence of it on the fuel performance is not identified yet. In this paper, impact of power density, cross-section parameters, and twist pitch on thermal and mechanical characteristics of fuel used in Fluoride-Salt-cooled high-Temperature Advanced Reactor is discussed based on fluid-thermal-mechanical coupling. For thermal features, twist pitch is key while others have few effects. Increase in twist pitch leads to temperature uniformity and rise owing to weaker mixing effects. Fuel center temperature at middle plane of 300mm-pitch rod is 829.58℃, 54.66℃ higher than that of 100mm-pitch rod. Difference of maximum and minimum temperature at 45° cross section of 500mm-pitch rod is 153.62℃, while the figure is only 74.00℃ of 300mm-pitch rod. Besides, axial temperature of cladding outer surface increases wavelike due to complex geometry. For mechanical features, not geometry sizes but temperature affects stress distribution. Maximum Von-Mises stress appears at the elbow, where maximum temperature exists, 116.8MPa under normal conditions, lower than tensile strength of the material. After identifying the influence of these factors, five dimensionless parameters are proposed to evaluate and rate fuel performance based on Technique for Order Preference by Similarity to an Ideal Solution. As a result, an optimization comes up, scoring 0.310, twice more than the original design, owing to the thermal uniformity and mechanical safety. This study provides a reference for identifying and evaluating the performance of helical structure. © 2024, The Authors. All rights reserved.

关键词： Geometry

A Novel Water Content Sensor Design and its Application for In-Situ Water Content Measurement Inside the flow Channel of Pemfc

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SSRN 2022年

作者： Zhang, Yan Wang, Weiding Liu, Yukai Su, Jinzhan International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering School of Energy & Power Engineering Xi’an Jiaotong University Xi’an710049 China

In-situ water content detection in proton exchange fuel cell (PEMFC) is of great importance to its water management. In this study, flexible thin film water content microsensor (WCMS) were fabricated and deployed for real-time measurement of water distribution inside the channel of proton exchange membrane fuel cells. The effect of inserting WCMS on the cell performance was confirmed to be negligible. Besides, three WCMS were used to monitor the variation of water distribution in the upstream, midstream and downstream of the flow channel, respectively. The experimental results show that the WCMS can efficiently detect the change of water content inside the fuel cell in real time. The co-occurrence phenomenon of water column clogging in the flow channel and degradation of cell performance were observed. This work provide a novel design of WCMS and its application on the water content distribution inside flow channel of fuel cells. © 2022, The Authors. All rights reserved.

关键词： Proton exchange membrane fuel cells (PEMFC)

Evaluation of a Numerical Model for Predicting flow and Heat Transfer in a Hexagonal Helical Cruciform Seven-Rods Bundle and Analysis of Rod Bundle Size Independence

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SSRN 2024年

作者： Jiang, Dianqiang Deng, Jian Zhang, Dalin Zhou, Xingguang Xiao, Changzhi Tian, Wenxi Qiu, Suizheng Su, Guanghui H. State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China Nuclear Power Institute of China Science and Technology on Reactor System Design Technology Laboratory Chengdu610213 China China Institute of Atomic Energy Beijing611731 China

In this study, the accuracy and applicability of the numerical model are comprehensively evaluated based on the experimental data of a hexagonal helical cruciform (HC) seven-rods bundle. The STAR CCM+ is utilized as a tool to obtain predicted results of flow and heat transfer in different flow regions. The numerical results indicate that it is an improved method to set a negative heat flux on the hexagonal wall in the laminar flow region. The Reynolds stress transport model can accurately predict the experimental results of heat transfer in the transitional flow region, with an average wall temperature deviation of 2.8℃. The SST k-ω model with cubic constitutive option can accurately predict the experimental results of the flow resistance, and a relative error of f is 1.8%. In the turbulent flow region, the SST k-ω model with cubic constitutive option provides an accurate prediction, with an average wall temperature deviation of 3.7℃. The realizable k-Ε two-layer model can accurately predict the flow resistance, and the relative error of f is 0.1%. The preferred numerical model is used to analyze the size independence of the HC rod bundle. This work provides certain guidelines for the accurate simulation in the HC seven-rods bundle. © 2024, The Authors. All rights reserved.

关键词： Computational fluid dynamics

Study of flow Pattern Transition Criterion and Heat Transfer Characteristics in Vertical Rectangular Narrow Channel for Steam Heating

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SSRN 2023年

作者： Gu, Shengjie Tao, Leren Jin, Cheng Ju, Yiwei Zhao, Xiefei School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power and Engineering University of Shanghai for Science and Technology Shanghai200093 China

To clarify the heat transfer characteristics of flow boiling in a narrow vertical rectangular channel at each stage and optimise the performance of the heat exchanger, an experimental study of the flow pattern and local heat transfer characteristics in a narrow vertical rectangular channel of steam heating with dimensions of 1400 mm × 250 mm × 2.75 mm (l × w × s) was carried out using deionized water as the working medium. Based on the mechanical model and the empirical formulas of the researchers, the preliminary derivation of the flow pattern transition criterion in the vertical rectangular narrow channel for steam heating is obtained. The effects of inlet temperature, mass flux and heating power on the local heat transfer characteristics were analyzed in conjunction with the flow patterns, and based on the parametric analysis of the experimental data, a new flow boiling heat transfer correlation formula was obtained which applies to the experimental conditions in this paper. The results show that the increase in inlet temperature has a positive effect on the nucleate boiling section, while the degree of effect on the local heat transfer coefficient is minimal after entering the churn flow phases. The increase in mass flux decreases the local heat transfer coefficient in the nuclear state boiling stage and enhances the local heat transfer coefficient in the evaporation zone of liquid film flow. The peak of the local heat transfer coefficient shows a tendency to shift to the left as the heating power increases. The new heat transfer correlation equation can well predict the local heat transfer coefficient of flow boiling in a vertical rectangular narrow channel heated by steam in this experimental condition. © 2023, The Authors. All rights reserved.

关键词： flow patterns