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Data Mining-Assisted Multi-Objective Optimization of Blade Angle Distributions for Efficiency and Stability Enhancement of a Free-Form Centrifugal Impeller

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SSRN 2024年

作者： Chen, Zhikai Chen, Ziying Sun, Jieshuai Guo, Yi Spence, Stephen Peng, Xueyuan Feng, Jianmei School of Energy and Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Manufacturing and Biomedical Engineering Trinity College Dublin Dublin 2 Ireland State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China

The design optimization process for a centrifugal compressors faces significant trade-offs between efficiency, pressure ratio, and stable operating range. To address this challenge, a data mining assisted-optimization combining machine learning modelling method and non-dominated sorting genetic algorithm III (NSGA-III) has been proposed to enhance efficiency and pressure ratio while considering expansion of operational stability. A validated CFD numerical model was established for data generation. A Light-GBM model with Bayesian hyperparameter tuning and a deep feedforward neural network (DNN) model were constructed, and the better one was selected for performance prediction. Data mining techniques, including Sobol sensitivity analysis and SHAP, were employed to identify the key sensitive parameters and their interactions. Finally, a NSGA-III-based multi-objective optimization was conducted to determine the optimal geometry of the free-form surface impeller. Results showed that the blade angle distributions at the leading edge of mid-span and shroud profile were the most sensitive parameters affecting isentropic efficiency at the design point, with their recommended ranges identified. The optimized impeller has an increase in total pressure ratio of 2.98% and isentropic efficiency of 0.67% at the design point, especially exhibiting excellent aerodynamic performance at higher mass flow rate conditions. The maximum improvements of total pressure ratio and isentropic efficiency were 12.91% and 9.53%, respectively, corresponding to the near choke mass flow rate at the design speed. Additionally, operating stability was expanded with a 1.22% increase in total pressure ratio at near surge mass flow rate at the design speed, which contributed to a delay in the onset of surge. © 2024, The Authors. All rights reserved.

关键词： Sensitivity analysis

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Effects of Inherent Aaems on Catalytic Gasification of Biomass with Large Particle Size Under Oxygen-Steam Atmosphere

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SSRN 2023年

作者： Ren, Jiyun Li, Yuhang Jin, Xiaoling Huang, Xiaole Li, Yang Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Xi’an Thermal Power Research Institue Co. Ltd. Xi’an710032 China

Oxygen-steam gasification of biomass is a promising technology because of its ability to improve syngas quality and reduce energy consumption. In this study, a fixed-bed reactor is employed to assess the effects of inherent alkali and alkaline earth metals (AAEMs) on the catalytic gasification of candlenut wood with large particle size under oxygen-stream atmosphere. The results show that the acid-washing would remarkably remove the inherent AAEMs in biomass, which is affected by the grain direction. In terms of the gasified chars derived from acid-washed biomass, AAEMs content gradually decreases along the end surface and radial direction, which could also be observed from the 3D reconstruction of X-ray CT images. In all biomass samples and gasified chars, micropores (0-10 μm) dominate and are distributed along the grain direction. In general, pores of 20-30 μm and above 30 μm comprise a minor proportion. Inherent AAEMs facilitate an augmentation in char yield as well as BET and total pore volume of gasified char. AAEMs and grain direction have a slight effect on functional groups of gasified chars. The tar component is remarkably affected by the grain direction. Acid-washing pretreatment augments the content and organic species of M2-M4 compounds (containing 2-4 benzene rings) in the tar. It also leads to a decrement in concentrations of H2, CH4, and CO2 by 14.49% and 13.35%, 0.51% and 0.89%, 2.32% and 1.37% in syngas for two-grain direction, respectively. But it raises the CO concentration by 17.1% and 15.18%, resulting in a reduction of 4.09% and 1.53% in syngas calorific value. A decrement in the volume fraction of CnHx induced from AAEMs is significantly affected by the grain direction. © 2023, The Authors. All rights reserved.

关键词： Biomass

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Load Forecasting of District Heating System Based on Improved Fb-Prophet Model

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SSRN 2022年

作者： Shakeel, Asim Chong, Daotong Wang, Jinshi State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi'An710049 China

Accurate load forecasting of district heating networks (DHN) is an essential guide to guaranteeing effective energy production, distribution, and rational utilization. Artificial neural networks have been extensively applied to heating energy prediction in DHN. An improved FB-Prophet model with additional positional encoding layers has been developed to forecast the DHN heat consumption. The accuracy of univariate and multivariate FB-prophet models is evaluated;this paper also investigates how training data affects the accuracy and robustness of improved FB-prophet model. Results revealed that the accuracy of the improved FB-Prophet model increases as the amount of training data increases;it is also observed that there exists a turning point after which robustness starts to decrease. To explore the performance of the improved FB-Prophet model in heating load forecasting tasks, another seven machine learning models, namely FB-Prophet, DeepVAR, long-short term memory (LSTM), extreme gradient boosting (XGBoost), multilayer perceptron (MLP), recurrent neural network (RNN), and support vector regression (SVR) are used for comparison. The historical heating load, outside temperature, relative humidity, speed of wind, direction of wind, and weather type (sunny, overcast, rainy) of a DHN in Serbia are utilized as the key parameters to extensively investigate the effectiveness of the improved FB-Prophet model. The prediction outcomes of all the models were analyzed thoroughly. The results indicated that the improved FB-Prophet model can generate the most precise and consistent predictions and it showed better results for sparse and noisy data of DHN. The prediction curve is fitted to the trend of hourly DHN consumption change, which can play an effective guiding function in the distribution of heat. © 2022, The Authors. All rights reserved.

关键词： Forecasting

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Experimental Study on Non-Isothermal Mixing Characteristics of Water in T-Junction

Experimental Study on Non-Isothermal Mixing Characteristics ...

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China Instrument and Control Society (ACCIS), Academic Conference of

作者： Shuhan Liu Wencang Guo Xianliang Lei Zhaojun Yuan Shuqi Meng Desheng Jin State Key Laboratory of Multiphase Flow Engineering Xi'an Jiaotong University Xian China China Nuclear Power Technology Research Institute Co. Ltd. Shen Zhen Guangdong China

ISBN: (数字)9798350350326

ISBN: (纸本)9798350350333

T-junction is an essential component in piping system of various thermal systems. When hot and cold fluid mixing in the T-junction, several compound mechanisms (like turbulent mixing, turbulent penetration, fluid stratification) make the mixing characteristics more complex. To clearly reveal such mixing mechanism with non-isothermal fluids, an experimental study was conducted with Ultrasound Doppler Velocimetry (UDV) and fast-response thermocouples bundle. The results show that the local velocity uncertainty of the UDV is within 10%, the uncertainty of the thermocouple bundle is 0.5°C, and the response time is 66.7 ms. After verification, the mixing characteristics between the main and branch pipe under different momentum ratios and temperature differences were discussed. It is shown that as the momentum ratio decreases, the location of the most intense radial temperature fluctuations and velocity fluctuations shifts towards the lower wall. At the same time, the peak flow rate in the cross-section increases by 35.7% and the main branch fluid mixing is more homogeneous. As the temperature difference increases, the thermal stratification is more pronounced and the velocity fluctuation peak moves towards the upper wall of the pipe.

关键词： Temperature measurement Temperature distribution Fluctuations Fluids Uncertainty Measurement uncertainty Thermocouples Distance measurement Velocity measurement Voltage control

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A Gpu-Accelerated Multi-Resolution Lsmps Method for multiphase flows Simulation with Gas-Liquid Phase Transition

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SSRN 2024年

作者： Cao, Sheng Ren, Qianyong Wang, Wenpeng Zhang, Bin Shan, Jianqiang School of Nuclear Science and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

The meshless Lagrangian method (particle method) demonstrates significant advantages in simulating multiphase flows with highly dynamic phase interfaces and has been widely applied in research areas such as ocean engineering, nuclear engineering, and aerospace engineering. The least squares moving particle semi-implicit (LSMPS) method theoretically attains high-order accuracy, significantly enhancing the precision and stability of simulations. However, compared to traditional Eulerian methods, its numerical discretization is more complex and computationally intensive, which limits its applicability in large-scale simulations. To mitigate these challenges, a multi-resolution particle model is implemented to reduce computational costs, and algorithmic improvements and optimizations enable GPU-based parallel processing, significantly boosting computational efficiency. Building on this foundation, a high-precision surface particle detection algorithm and a stable gas-liquid phase transition model are developed. The phase transition model integrates the volume change resulting from phase transition as a source term in the pressure Poisson equation. Benchmark tests of single bubble rising in liquid, Rayleigh-Taylor instability, and two-dimensional horizontal film boiling were conducted to validate the accuracy and efficiency of the GPU- accelerated multi-resolution LSMPS method for simulating multiphase flows, thereby promoting the application of the LSMPS method in both scientific research and practical engineering. © 2024, The Authors. All rights reserved.

关键词： Poisson equation

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Comprehensive Parameter Analyses on Steam-Air Condensation at Equal- Height-Difference Natural Circulation Loop Under Large Air Mass Fraction

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SSRN 2024年

作者： Chen, Weixiong Wang, Han Li, Sinian Kai, Hui Zhao, Quanbin Li, Shaodan Wang, Jinshi State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Missile Engineering College Rocket Force University of Engineering 710025 China Science and Technology on Thermal Energy and Power Laboratory Wuhan 2nd Ship Design and Research Institute Wuhan430205 China

With the development of small-sized reactors, a passive containment cooling system (PCCS) named equal-height difference natural circulation loop (EHDNCS) has been developed. Experiments were conducted at higher air mass fractions to evaluate the condensation heat transfer coefficient (HTC) as a function of steam-air mixture pressure, air mass fraction, and wall subcooling. The results indicate that the condensation HTC decreases with increasing air mass fraction and increases with increasing steam-air mixture pressure in the containment. The relationship between condensation HTC and air mass fraction gradually transitions from non-linear to linear as the steam-air mixture pressure increases. The condensation HTC increases with increasing wall subcooling;However, for air mass fractions greater than 75%, the condensation HTC remains nearly constant with changes in wall subcooling. A quantitative relationship between the condensation HTC and the height of the PCCS (sum of riser height and 0.5 times heat exchanger height) has been derived by calculating the cooling water flow driving force and resistance in the natural circulation loop. The applicable conditions for optimizing the riser height and the initial ratio of the riser to heat exchanger height to enhance the heat transfer power of the PCCS were proposed. Based on the experimental results, an empirical correlation equation for predicting the condensation HTC for PCCS with EHDNCS is established, with a prediction deviation within ±31%. © 2024, The Authors. All rights reserved.

关键词： Heat exchangers

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Numerical and Experimental Investigation of Proton Exchange Membrane Fuel Cell with Perpendicular Gas Supply Through the Ridge

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SSRN 2023年

作者： Zhang, Yan Lu, Xinyu Su, Jinzhan School of International Trade and Economics China 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

The structural design of the cathode flow field in proton exchange membrane fuel cell (PEMFC) is essential for efficient gas supply and effective water removal. For investigating the mechanism behind the effect of gas flow direction on improving the performance of PEMFC, a novel modified serpentine flow channel with vertical inlets through the ridge for PEMFC was proposed and investigated by numerical and experimental methods. Under the operating voltage of 0.4 V, the vertical air supply mode exhibits a 7% higher current density compared to the parallel air supply mode. Compared with conventional air supply mode through the serpentine flow channel, vertical air supply mode modified serpentine through a tunnel inside the ridge exhibited higher oxygen uniformity and higher current density. Furthermore, we conducted research on the impact of physical parameters, including the porosity and thickness of the GDL, as well as the vertical gas supply pore density, on the performance of the PEMFC within the vertical gas supply mode. At an operating voltage of 0.4 V, the current density of PEMFC with a GDL thickness of 0.28 mm is 1.0009 A/cm2, which is 3.02% and 6.13% higher than that of PEMFC with vertical inlets with GDL thickness of 0.38 and 0.48 mm, respectively. With a porosity of 0.6, the current density of PEMFC reaches 1.0395 A/cm2, surpassing that of PEMFCs with porosities of 0.2 and 0.4 by approximately 24.8% and 6.6%, respectively. Moreover, higher vertical inlet densities lead to improved PEMFC performance. Simulation and experimental results demonstrate that this modified flow field effectively addresses uneven current density distribution and enhances power output at low voltage. © 2023, The Authors. All rights reserved.

关键词： Porosity

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Hydrodynamic Pattern in Drying Saline Droplet with Suspended Nanoparticles

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Journal of Bionic engineering 2020年第4期17卷 802-808页

作者： Junheng Ren Xin Zhong Lu Shen Fei Duan School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

Evaporation of multicomponent droplets has gained much attention nowadays because of their complex flow fields and various deposition *** we observe strong flows in evaporating sodium chloride saline droplets with suspended alumina oxide *** evolution of flow pattern was studied by tracking the trajectories of particles and the velocity field was investigated with Particle Image Velocimetry *** non-uniform evaporation rate along the droplet surface leads to a concentration gradient which induces the convection *** the evaporation process before crystallization happens,evolution of the flow can be divided into two *** Regime I,a centrosymmetric convection recirculation is formed *** RegimeⅡ,the convection recirculation migrates to the droplet edge and evolves into several small *** the late evaporation stage,crystallization could induce strong convection *** is shown that the flow tends to become more chaotic with a lower salt concentration.

关键词： convection flow concentration gradient saline droplet crystallization

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Effect of Tungsten Size on Thermal Analysis and Mechanism of Lithium Perchlorate-Based Electrically Controlled Solid Propellant

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SSRN 2023年

作者： Yang, Meng Yoh, Jack J. Tang, Chenglong Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Aerospace Engineering Seoul National University Seoul08826 Korea Republic of

Electrically controlled solid propellant (ECSP) is a novel and potential of propellant with excellent properties, which can achieve multiple ignitions and extinguishments through supplying and cutting electric power. At present, thermochemistry coupled with electrochemical reaction processes are complex and not understood clearly, especially its based thermal decomposition mechanism without electric power. In this work, the baseline ECSP was prepared using lithium perchlorate (LiClO4, LP) as oxidant, and tungsten as metal additive to obtain high energy ECSP samples. The scanning electron microscope (SEM), differential scanning calorimeter (DSC) and thermogravimetry (TGA) were used to investigate thermal analysis characteristics of ECSP and the effect of metal tungsten sizes on reaction process and mechanism. The heat release and effective activation energy (Eα) of baseline ECSP were lower than those of metalized ECSP. In addition, with W size increasing, heat release and Eα of ECSP increase. Based on thermal analysis and kinetic results, the decomposition mechanisms of ECSP main components and samples were proposed. The absorbed and crystal water evaporated, then main components molten for all cases at low temperature ( © 2023, The Authors. All rights reserved.

关键词： Thermogravimetric analysis

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Investigation of Thermal Radiative Transfer Characteristics of Single Water Droplet

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SSRN 2023年

作者： Zhang, Dan Tu, Maoping Yuan, Yang Han, Wei State Key Laboratory of Multiphase Flow in Power Engineering School of Energy & Power Engineering Xi'an Jiaotong University Shaanxi Xi’an710049 China Xi'an Thermal Power Research Institute Co. Ltd Shaanxi Xi’an710054 China

Directly heat water droplet by thermal radiation was the key process of coupling solar energy to achieve green production in many industrial applications, such as desalination, carbon capture, energy storage, and so on. The radiative transfer of single water droplet for given irradiation, including reflection, absorption, transmission and their dependences on external irradiation, droplet geometry and radiative properties were investigated through a calculation model set up according to zone method. In current study, the ranges of equivalent diameter and length-width ratio of droplet were 0.1-1.0 mm, 1-10 respectively, its absorption coefficient was 10-15000 m-1 and refractive index was 1.2-2.0. Results suggested that, (1) the absorption mode of droplet could be classified into surface absorption (SA) and volumetric absorption (VA) depending on whether its optical thickness was greater than 1. In VA, droplet could get uniform and fast temperature increasing, and its absorptivity and mean temperature increase rate could be simultaneously improved by increasing absorption coefficient. (2) Scattering included reflection and transmission. Compared with incident irradiation, reflection distributed mainly on the same side of droplet's long axis, while transmission mainly on the opposite side. The overall reflectivity increased with rising refractive index, but was independent on droplet size. While its transmissivity increased with enlarging length-width ratio or reducing equivalent diameter. (3) In VA, at least 40% of incident irradiation was scattered out. The total quantity of scattering could be adjusted by changing absorption coefficient in VA or refractive index in SA. The proportion of transmission in scattering could always be increased by reducing refractive index. © 2023, The Authors. All rights reserved.

关键词： Drops

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