bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on Acid Corrosion Characteristics in Low-Pressure Stage Initial Condensation Zone of Supercritical H2O/CO2 Turbine
Authors: Ma Zi-yue , Wang Xiao-fang , Jiang Tao , Wang Wei , Xu Yang 
Published: April 2021

Abstract
Compared with the traditional steam turbine, the supercritical H2O/CO2 turbine has a relatively high CO2 content in the working fluid. In the initial condensation zone, CO2 dissolves in the condensed water to form carbonic acid, which intensifies the corrosion of blade. In order to study the acid corrosion characteristics in the initial condensation zone of supercritical H2O/CO2 turbine, the acid corrosion rate of the blades in the initial condensation zone of supercritical H2O/CO2 turbine was calculated and analyzed based on the numerical model of non-equilibrium condensation flow and a numerical model of CO2 corrosion reaction. The results show that the temperature, pressure, proportion of CO2 in the gas phase and thickness of the solution on blade surface are the main factors affecting the acid corrosion rate in the initial condensation zone of the turbine. The influence of temperature and pressure is more significant. Overall, the acid corrosion rate decreases stage by stage.
Study on Stiffness of Angular Contact Ball Bearing and Its Evolution Rule under Excessive Preload
Authors: Yun Xianghe , Li Ning , Wen Baogang , Han Qingkai 
Published: April 2021

Abstract
There are many factors influencing the bearing stiffness variation, among which, preload has more significant effect. In addition, bearing stiffness is developing accompanying with its performance deterioration, which leads to vibration variation of bearing-rotor system. In this paper, system support stiffness model and system dynamics model of micro-turbine bearing-rotor system test rig are built to obtain the bearing stiffness identification method by model simplification based on modal theory. The identification method is validated adopting modal test. The stiffness evolution rule and rotor vibration of different stages are achieved via employing the identification method to extract bearing stiffness over the process of bearing run-to-failure. The results indicate that bearing stiffness is the main source of system support stiffness. Bearing stiffness will change during the whole life, which affects the vibration responses in time and frequency domain. Rotor stability is influenced by cage movement.
Analysis of cage slip in angular contact ball bearing considering non-Newtonian behavior of elastohydrodynamic lubrication
Authors: Wen Baogang , Wang Meiling , Yun Xianghe , Zhang Xu , Han Qingkai 
Published: April 2021

Abstract
A dynamic model of angular contact ball bearing considering non-Newtonian behavior and interaction between balls and cage is deduced to predict cage slip. And then the cage slip are investigated and compared with measured results under different rotational speeds and axial loads to verify the proposed dynamic model of bearing. It is concluded that the results based on the non-Newtonian behavior of elastohydrodynamic lubrication is more agreement in trend with the tests than that based on the Newtonian assumption, and so the non-Newtonian behavior of elastohydrodynamic lubrication are needed in the cage slip analysis.
Effect of ball bearing misalignment on dynamic characteristics of rotor system
Authors: Wen Baogang , Wang Meiling , Han Qingkai , Yu Changxin 
Published: April 2021

Abstract
A theoretical model with 5 degrees of freedom (DOF) is derived for a rigid rotor system supported by two ball bearings considering the changes of the bearing stiffness due to misalignment. And then radial and axial vibrations of the rotor system and its bearing reactions under different misaligned offsets are investigated with theoretical and numerical analysis. Then, the effects of misalignment on the vibrations of rotor and the bearing, the variation of stiffness and reaction characteristics of the misaligned ball bearing are predicted theoretically. It is concluded that angular misalignment may cause axial vibration and parallel misalignment can bring out extra moment loads for misaligned bearing.
Design and Research of New Type High-speed Hydrostatic Spindle Test Rig
Authors: Xiao Yunfeng , Song Di , Meng Bo , Wang Lingyu , Zhang Hao , Mingyue Wang 
Published: April 2021

Abstract
Aiming at the air dynamic pressure foil bearing performance test rig, design and research a new high-speed static pressure spindle test rig. Carry out aerodynamic design of the driving turbine and compressor, obtain the three-dimensional impeller shape and carry out the strength calculation, design a new high-speed static pressure spindle test rig; use the finite element method to model the test bed rotor system, and use the transfer matrix method to analyse the shaft system structure critical speed and mode, so that the test rig can effectively avoid the critical speed and run stably. Analyse the unbalanced response and stability of the rotor system, and reasonably arrange the test rig device to achieve the purpose of measuring the performance of the dynamic pressure foil bearing, and ensure that the turbine static pressure spindle test rig can provide for the measurement of the air dynamic pressure foil bearing performance stable high speed.
Investigation of Time-series Prediction for Turbine Machinery Condition Monitoring
Authors: Liu Chang-Jun , Liu Hai-Tao , Bian Chao , Chen Xu-Dong , Yang Shu-Hua , Wang Xiao-Fang 
Published: April 2021

Abstract
A running compressor generates a huge amount of data every day. Some of the data contains useful information that allows the user to determine in advance whether the machine will fail or not. Forecasting in advance cannot only avoid the huge loss caused by unnecessary downtime but also ensure the safety of staff. The main tasks of compressor condition monitoring include data acquisition, data preprocessing, data analysis, alarm module, response strategy analysis, etc. Prediction is one of the tasks of condition monitoring. This paper mainly studies the performance of different time prediction models on the running data produced by a centrifugal compressor. In the data preprocessing part, this paper uses Bayesian wavelet denoising and probabilistic principal component analysis methods proposed by the research group to remove the useless parts in the data. In the part of time series model, the prediction performance of LSTM, GRU and ARIMA on the same dataset is compared. The comparative results indicate that since the dataset is non-stationary, the LSTM and GRU outperform the statistical ARIMA model.
Impact of exploration-exploitation trade-off on UCB-based Bayesian Optimization
Authors: Bian Chao , Wang Xiaofang , Liu Changjun , Xie Xinyu , Haitao Liu 
Published: April 2021

Abstract
As an efficient global optimization method to deal with expensive black-box functions, Bayesian optimization (BO) has great potential in the field of turbomachinery component design. It can relieve the complexity, long cycle, and excessive dependence on experience of the design process. A core of Bayesian optimization is acquisition functions which aim to guide the search to efficiently find the optimum. An excellent acquisition function can greatly improve the performance of the algorithm. The well-known acquisition function, upper confidence bound (UCB), in Bayesian optimization achieves the balance between local exploitation and global exploration through an explicit trade-off coefficient. The trade-off coefficient is a key to the quality of UCB-based Bayesian optimization. Currently, this coefficient is either manually specified according to some criterion or sampled from a specific distribution. Due to the lack of a comparative study on existing trade-off strategies, this paper attempts to comprehensively analyse and highlight the impact of various trade-off strategies on the performance of UCB-based BO algorithm through eleven numerical examples and two turbomachinery design cases. The comparative results indicate that the proper trade-off is key for the optimization quality, and the strategy of looping through a trade-off set shows superiority in our numerical experiments.
Numerical study on film cooling characteristics of BESA hole with water mist/air two-phase flow
Authors: Kang Huang , Pei-jie Shi , An-lin Jiang , Hu-sheng Ma 
Published: April 2021

Abstract
In view of a new type of film cooling hole, the backward-expanding shoulder arm(BESA) hole proposed by the author, a numerical model of two-phase flow film cooling with water mist is established. The numerical simulation of water mist / air two-phase flow film cooling characteristics shows that the comprehensive performance of water mist / air two-phase flow film cooling is significantly improved compared with pure air film cooling. For the round hole plate model, when the blowing ratio is 0.5, the film cooling efficiency of two-phase flow film cooling with 2% water spray is 37.5% higher than that of pure air film cooling (20D from the film hole outlet), When the blowing ratio is 1.0, the film cooling efficiency of the flat two-phase flow with 2% water spray is 49.0% higher than that of the pure air film cooling (20D away from the film hole outlet). When the spray amount of water is the same, the film cooling efficiency of the BESA hole is higher than that of the round hole, the expanding hole and the shoulder arm hole. For the flat film cooling model of the BESA hole, When other factors remain unchanged, the cooling efficiency of the two-phase flow film increases monotonously from 2% to 5%. The cooling characteristics of the two-phase flow film on the pressure surface of the turbine blade of the BESA hole are similar to those of the flat model, and the film coverage effect is better than that of the round hole, the expanding hole and the shoulder arm hole.
Experimental and numerical investigation on the influence of the diffuser blade setting angle on the performance of centrifugal compressor
Authors: Fang Junyi , Ji Chunjun , Li Chunyang , Zhang Ruiwu , Denis Shalyaev 
Published: April 2021

Abstract
Setting angle of the front blade row of tandem cascade diffuser was investigated experimentally to understand its influence on the performance of centrifugal compressor. Three diffusers with different setting angles were tested. The change of front blade setting angle mainly alters. The angle of attack (AOA) on the leading edge of front blades, which affects the surge point of the compressor. The throat area of the blade row is also modified, which affect the chock point of the compressor. With the increase of setting angle, performance curves of centrifugal compressor move to large flow rate side, the operation range is increased at the same time. In addition, numerical simulation was used to investigate the flow details on the passage of diffuser blades. Overall, the setting angle of front blade row has a significant influence of the performance of centrifugal compressor.
Effect of Hub Gap on Expanding Stability of Centrifugal Compressor
Authors: Li Chunyang , Ji Chunjun , Fang Junyi 
Published: April 2021

Abstract
In this paper, the possibility of using hub gap (“ HG ”for short) to suppress gas stall and expand the range of stable working condition of compressor is verified by numerical method. The research shows that when designing flow rate, HG increases, the efficiency and pressure ratio of model level decrease. When there is a large flow, the efficiency and pressure ratio of HG model are higher than those without HG. The larger HG is, the higher the efficiency and pressure ratio is. From the analysis of the expanding stability capacity, the model-level flow margin of small HG and large HG is 5% and 15% higher than that of models without HG, and the comprehensive stall margin is 6.87% and 23.59% higher on average. When operating at unstable working conditions, the action of HG causes the airflow in the high pressure zone to flow into the gap and out of the low pressure zone, which improves the flow distribution in the blade passage and makes the flow field stable. However, when operating near the design condition, the leakage flow and its mixing with the momentum of the mainstream are the main sources of aerodynamic loss. The larger HG is, the greater the pressure loss caused by the leakage flow is. Generally speaking, HG can play the role of compressor expansion stability, but at the cost of efficiency; The bigger HG is, the stronger the role of expanding stability is and the greater the efficiency loss is.
Numerical Study on Hydrodynamic Characteristics in a Centrifugal Pump at off Design Conditions Based on a Cycling-System Model
Authors: Yin Wen-Hui , Wang Xi , Yu Tao , Jian Jie , Zhang Xiang-Yuan , Shuai Zhi-Jun , Li Wan-You , Jiang Chen-Xing 
Published: April 2021

Abstract
In this paper, the unsteady hydrodynamic characteristics of a centrifugal pump handled at low-flow-rate conditions are numerically investigated. A cycling-system model is established to capture the influence of off-design operation on the internal flow field and the pressure pulsation. The preliminary results show that the cycling-system model can predict the flow field of the pump more conforming to the practical situation than that of the pump alone; besides, the generation of stall clusters in the impeller will induce low-frequency pressure pulsation.
An Experimental Platform with Rotating Airflow Excitation and Stationary Blisk Vibration Measurement
Authors: Ouyang Luohui , Bi Qingzhen , Shang Hai , Zhu Limin , Yu Jianhua 
Published: April 2021

Abstract
With the question that the vibration of the realistic blisk in the engine is hard to be predicted, researchers need an experimental test platform to study the realistic dynamic properties and monitor the vibration of the designed blisk. For keeping the relative motion between airflow and blisk in a real engine, and facilitating the measurement of the blisk vibration, a new experimental platform with rotating air excitation and stationary blisk vibration measurement is developed in this paper. Firstly, the schematic diagram of the test platform is shown and all the components are illustrated clearly, including the stationary airflow excitation system, the test rig, and the vibration measurement system. Then two typical experiments are conducted with the designed academic blisk. A stationary excitation and a transient acceleration excitation are employed to the stationary blisk. Through the time-frequency analysis of the vibration signal measured by the Laser Doppler Vibrometer, the source of each component of the vibration signal is obtained. The experiment results show that the stationary and transient vibration of the blisk can be measured and identified correctly.
A comparative study on the numerical solution algorithms of gas Reynolds equation
Authors: Wang Yongliang , Wang Yi , Zheng Longkai 
Published: April 2021

Abstract
The improved P* algorithm is studied for solving the Reynolds equation by finite difference method. P* algorithm has the advantages of distinct mathematical concepts and simple programming. Firstly, The P* algorithm is combined with the Successive Over-Relaxation (SOR) method, considering the influence of the selection of relaxation factor on the calculation results. The optimal relaxation factor is determined to be 0.97, in this case, the minimum film thickness of flexible gas foil bearing can be calculated to 3.8 μm. Then, by changing the position of P*, the algorithm accuracy, sensitivity to the initial value, and computational efficiency of different P* algorithms are compared and studied. In the end, the P* algorithm is compared with the Newton-Raphson algorithm, it is found that although the Newton-Simpson algorithm computations the matrix dimension is large; but it has the advantages of fast computing speed and high efficiency.
Numerical Study on Particle Deposition Characteristics of Impingement Effusion Cooling Structure
Authors: Li Bingran , Liu Cunliang , Li Lin , Chen Wenbin , He Yihong 
Published: April 2021

Abstract
The paper investigates the effect of impingement velocity and particle diameters on the flow and solid-phase deposition characteristics of the impingement effusion cooling structure by numerical simulation of gas-solid two-phase flow using DPM with UDF. The results show that under the same condition of the particle diameter, both the particle deposition flux and the particle deposition rate become increase with the increasing of the impingement velocity while the dimensionless particle deposition rate increases first and then decreases; Under the same condition of the impingement velocity, with the increase of the particle diameter, the particle deposition flux increases, while the particle deposition rate and the dimensionless deposition rate of the particle both increase first and then decrease. Taken together, Brownian motion of particles, turbulent diffusion, and particle inertia and flow characteristics is the main factors that affect the solid-phase particle deposition behaviour.
Volumetric entropy generation rate associated with tip clearance flow in linear cascade
Authors: Bingxiang Long , Qin Chen , Zebin Ren , Daxiong Liao 
Published: April 2021

Abstract
The tip clearance flow structure and its corresponding entropy generation rate of a linear cascade with 1.85mm radial tip clearance operating under three different incidence angle are investigated. The incidence angle influences the tip leakage vortex position as well as the size of the tip leakage vortex. Larger incidence angle results in larger tip leakage vortex and pushes the tip leakage vortex further away from the suction side. The entropy generation rate related to the tip clearance flow structure is calculated and it is confirmed that tip clearance flow is the main major source of aerodynamic loss in linear cascade. Larger incidence angle leading to higher entropy generation rate. Results also show that it’s not the core region of tip leakage vortex but the edge vortex and shear layer of the tip clearance flow which has the highest entropy generation rate. When operating under an incidence angle of 4°, there exist an extra high entropy generation rate region in main flow. It is found that the compression and expansion of fluid due to the existence of tip clearance vortex was the main reason for this extra high entropy generation.
Investigation of noise characteristics of periodic jet impinging on a flat plate
Authors: Liu Xin , Hou Jiaxin , Huang Heyuan , Guo Xiaoliang , Xie Junlong 
Published: April 2021

Abstract
Noise characteristics of periodic jet impinging on a flat plate are investigated. The numerical model is established by large eddy simulation and FW-H acoustic analogy method. Compared with experimental data obtained by noise measurement experiment, the effects of acoustic integral surface and different subgrid-scale models on noise simulation results are studied. The accuracy of the optimized numerical model is also validated by verification experiment. Further, the present numerical model is applied to numerical prediction of noise directivity and spectrum distribution with different waveforms and periodic frequency. Compared with the steady impinging jet, noise characteristic of periodic jet impinging on a flat plate are presented and the mechanism of acoustic source is analyzed. The present work provides a reference value for the analysis and control of noise of periodic jet impinging on a flat plate.
Research on structure characteristics of the helium-lubricated spiral grooved thrust bearing for helium turbine expander
Authors: Zhang X H , Peng N , Dong B , Li KR , Liu L Q 
Published: April 2021

Abstract
The helium-lubricated spiral grooved thrust bearing of helium turbo expander was studied by numerically simulating the steady-state non-linear Reynolds equation, the Reynolds equation of the pressure was solved by finite difference method (FDM), the film pressure distribution is calculated iteratively by MATLAB program, the structural parameters including the spiral angle, the groove length ratio, the groove width ratio influenced on the static characteristics were analyzed. The results show that: The bearing loading capacity of helium lubricated spiral grooved thrust gas bearing is lower than that of air lubricated bearing under the same conditions; The viscosity of the lubricant only affects the gas carrying capacity of the thrust disc when the spiral groove is on the bearing, while the density of the lubricant has a greater influence on the bearing loading capacity; When the spiral groove is designed on the rotor thrust disc, the bearing loading capacity of the spiral grooved thrust bearing increases by 6% on average compared with that of the spiral groove on the bearing.
The influence of wall roughness on centrifugal pump performance
Authors: Wang Von-Hao , Li Kun-Hang , Li Jing-Yin 
Published: April 2021

Abstract
Wall roughness is an important factor in the pump head and efficiency. Influence of wall roughness on the performance of a centrifugal pump is conducted with numerical approach. In the present study, a critical value of wall roughness is found. The performance of the pump decreases significantly while the wall roughness is less than critical value and decreases slightly while exceeding it. Influence of wall roughness of each domain is compared; the result revealed that the influence of wall roughness was decreased for volute, impeller, inlet and outlet respectively. Blade wall roughness of impeller has the greatest effect on pump performance, and pressure surface roughness has a greater influence than that for suction surface. This study could provide a reference for the manufacture and design of this type of centrifugal pump.
Effect of taper parameters on mechanical seal performance of taper/pores composite mechanical seal
Authors: Cheng X P , Liu Q , Zhang Y L , Wei J 
Published: April 2021

Abstract
a new combination fluid seal with the cone/pores is given, and the 3D fluid/solid coupling theory model is constructed, considering the interaction between the liquid pressure field and the stress deformation of the seal rings, led to seal clearance unceasingly change. Through the corresponding numerical calculation, film pressure distribution and end face deformation situation are obtained between the seal end faces, the influence rule of taper on sealing performance under the high and low pressure conditions is analyzed. The results show that the dynamic pressure effect caused by rhomboid pores can produce circumferential and radial wavy deformation of the seal end faces, while the static pressure effect also changes with the taper change of the end faces. For the low pressure and medium speed equipment, the conical end face which the taper is 0-2.4 should be chosen priority. For higher pressure and rotational speed device, the convergence end face seal which the taper is 0-2.4 should first be chosen.
Modelling of polymer optical fiber-based solar concentrators
Authors: Arrue J , Vieira A , García-Ramiro B , Illarramendi M A , Jiménez F , Zubia J 
Published: April 2021

Abstract
A comprehensive model for the theoretical simulation of luminescent solar concentrators (LSCs) has been developed and examined. It can simulate the interdependent effects of multiple dopants having two main electronic energy states, which are incorporated simultaneously into the fiber core, as well as the effect of the cladding. The available experimental results appear to confirm the accuracy of the model, which is a valuable tool for gaining insight into the behavior of LSC prototypes, since it may guide the designers at the early stages of optimization processes.