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Influence of Real Gas Properties on Aerodynamic Losses in a Supercritical CO_(2) Centrifugal Compressor

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Journal of Thermal Science 2024年第6期33卷 2032-2046页

作者： YANG Mingyang CAI Ruikai ZHUGE Weilin YANG Bijie zhang yangjun School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China School of Vehicle and Mobility State Key Laboratory of Intelligent Green Vehicle and MobilityTsinghua UniversityBeijing 100084China Department of Mechanical Engineering Imperial College LondonLondon SW72AZUK

Supercritical carbon dioxide(SCO_(2))centrifugal compressor is a key component of a closed Brayton cycle system based on SCO_(2).A comprehensive understanding of the loss mechanism within the compressor is vital for its optimized ***,the physical properties of SCO_(2) are highly nonlinear near the critical point,and the internal flow of the compressor is closely related to its properties,which inevitably influences the generation of aerodynamic losses within the *** paper presents a comprehensive investigation of the compressor's loss mechanism with an experimentally validated numerical *** real gas model of CO_(2) embodied in the Reynolds-Averaged Navier-Stokes(RANS)model was used for the ***,the numerical simulation method was validated against the experimental results of Sandia SCO_(2) ***,performance and loss distribution of the compressor were compared among three fluids including SCO_(2),ideal CO_(2)(ICO_(2))and ideal air(IAir).The results showed that the performance of SCO_(2) was comparable to IAir under low flow coefficient,however markedly inferior to the other two fluids at near choke *** distribution among the three fluids was *** the impeller,SCO_(2) was the most inefficient,followed by ICO_(2) and *** discrepancies were magnified as the flow coefficient *** is due to a stronger Blade-to-Blade pressure gradient that intensifies boundary layer accumulation on walls of the shroud/***,owing to the reduced sonic speed of SCO_(2),a shock wave appears earlier at the throat region and SCO_(2) encounters more intenseboundarylayerseparation.

关键词： SCO_(2) centrifugal compressor loss mechanism real gas properties

Real-Time Instability Detection of Centrifugal Compressors Based on Motor Speed Measurements

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Journal of Thermal Science 2023年第1期32卷 310-329页

作者： CHEN Haoxiang ZHUGE Weilin QIAN Yuping zhang yangjun LIU Hongdan State Key Laboratory of Automotive Safety and Energy Tsinghua UniversityBeijing 100084China Chongqing Jiangjin Shipbuilding Industry Corporation China Shipbuilding Industry CorporationChongqing 402263China

Flow instability in the centrifugal compressor should be detected and avoided for stable and safe *** to the popularity of electric centrifugal compressors,instability detection could be achieved by measuring motor signals instead of traditional aerodynamic *** this paper,the feasibility of instability detection by motor signals(*** speed and phase current)was studied *** physical structure and control method of the electric centrifugal compressor were discussed to reveal the potential of instability detection by motor *** pressure signals and motor signals measured during unsteady experiments were analyzed in the time domain and frequency *** of these signals were then compared under different operating conditions to indicate the feasibility of instability detection by motor ***,the ability of Short-Time Fourier Transform(STFT)of rotating speed signals in real-time instability detection was *** showed that the rotating speed signal is a good alternate for instability detection in spite of signal distortion,while the phase current signal can only detect surge due to the low resolution of the *** on the variations of the amplitude and frequency of rotating speed signals,the real-time instability can be captured accurately by STFT with a window size of 0.5 ***,the interference caused by the controller can be removed by STFT.

关键词： centrifugal compressor instability detection real-time rotating speed STFT

Improving the performance of ducted fans for VTOL applications:A review

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Science China(Technological Sciences) 2022年第11期65卷 2521-2541页

作者： QIAN YuPing LUO YiWei HU XuanYang ZENG ZeZhi zhang yangjun State Key Laboratory of Automotive Safety and Energy School of Vehicle and MobilityTsinghua UniversityBeijing 10o084China

Ducted fans have been widely used in VTOL aircraft due to the high propulsion efficiency and *** efficiency and stability of ducted fans deteriorate in some flight conditions such as hovering in crosswinds or ground *** is necessary to optimize the ducted fan’s structures or apply flow control methods for better adaptions to the typical *** paper presents a detailed review on the ducted fan technology for VTOL applications,especially the methods for improving its efficiency and *** first simplified the classification categories based on boundary conditions instead of flight conditions,since the new classification method covers more situations and is easier to distinguish flow field *** flow characteristics,thrust properties and the optimal structures under different boundary conditions were summarized and ***,new configurations and flow control methods for increasing the efficiency and stability were *** newly proposed integration design between the ducted fan and the motor was emphasized for increasing the power density of the ducted *** review would be helpful to improve our understanding of the relationship between the structures,flow characteristics and thrust properties of ducted fans under different flight conditions,and inspires scientists to design high-efficiency and high-stability propulsion systems with ducted fans.

关键词： ducted fan VTOL figure ofmerit working stability aerodynamic stability

Performance Improvement of a Centrifugal Compressor for the Fuel Cell Vehicle by Tip Leakage Vortex Control

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Journal of Thermal Science 2021年第6期30卷 2099-2111页

作者： CHEN Haoxiang ZHUGE Weilin zhang yangjun MA Xuelong TAO Lin State Key Laboratory of Automotive Safety and Energy Tsinghua UniversityBeijing 100084China Weichai Power Co. Ltd.Weifang 261061China Xecaturbo(Shanghai)Technology Co. Ltd.Shanghai 200241China

Heightened interests have been laid at the preliminary design and optimization of the centrifugal compressor for the fuel cell *** centrifugal compressor for fuel cell vehicle is driven by a high-speed motor;however,the limit of the motor speed makes the flow passage of the impeller long and narrow,which leads to a serious tip leakage *** tip leakage loss deteriorates the compressor *** this paper,3-D numerical simulations were carried out with the aim of investigating the tip leakage loss in a prototype centrifugal compressor for a 100 kW fuel cell *** results revealed that the mixing loss caused by the interaction between the tip leakage vortex and the downstream tip leakage flow contributed to the major part of the tip leakage *** path of the tip leakage vortex almost followed the streamwise direction,while the downstream tip leakage flow exhibited strong circumferential momentum,which referred to the fact that they were nearly ***,a flow control approach,which was realized by enhancing the blade loading around the leading edge of blade tips in this paper,was proposed to decrease the interaction angle between the tip leakage vortex and the downstream tip leakage flow and then mitigate mixing loss by changing the flow direction of the tip leakage *** results showed a smaller interaction angle was achieved in the optimized impeller compared with the baseline ***,the efficiency was also improved by 1.30%at design condition and the maximum efficiency improvement could be up to 10%at large mass flow condition of 92000 r/*** manufactured and tested,the optimized compressor was proved to achieve an isentropic efficiency of 75.84%at design condition.

关键词： centrifugal compressor fuel cell vehicle efficiency improvement tip leakage vortex mixing loss

Characterization of Swirling Inflow Effects on Turbine Performance under Pulsating Flows

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Journal of Thermal Science 2022年第5期31卷 1734-1744页

作者： DING Zhanming WANG Cuicui zhang Junyue LIU Ying HOU Linlin ZHUGE Weilin zhang yangjun Science and Technology on Diesel Engine Turbocharging Laboratory China North Engine Research InstituteTianjin300400China Kangyue Technology(Shandong)Co. LtdShouguangShandong262718China State Key Laboratory of Automotive Safety and Energy Tsinghua UniversityBeijing100084China

The present study focuses on the influence of the swirling flows on flow behaviors and performance of a radial-flow turbocharger turbine under pulsating inflow *** characterize the effects of swirling flow,three sets of simulations of the turbine were carried out,which are an unsteady simulation under pulsating swirling inflow,an unsteady simulation under equivalent pulsating uniform inflow,and quasi-steady simulations under uniform *** proved that swirling flow has a considerable negative influence on turbine instantaneous performance and lead to 2.5%cycle-averaged efficiency reduction under pulsating flow *** inflow would lead to significant losses in both the volute and the rotor,while the pulsating inflow leads to higher losses in the rotor and shows little influence on the losses in the *** instantaneous efficiency reduction of the turbine could be correlated with the time-varying inlet swirl *** the influence of unsteady inlet swirls,the volute flow field is highly distorted and the free vortex relation is no longer *** swirling flow has strong interactions with the wake flow of the volute tongue,leading to additional *** flow angle at rotor inlet is remarkably reduced and its distribution is significantly *** separation flows and passage vortices would appear in the rotor because of the swirling inflow,leading to inferior rotor performance.

关键词： swirling inflow pulsating flow CFD turbocharger turbine internal combustion engine

Numerical analysis of wind effects on aerodynamic characteristics of a ducted fan

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Chinese Journal of Aeronautics 2024年第5期37卷 263-280页

作者： Yiwei LUO Tianfu AI Yuhang HE Bin XU Yuping QIAN yangjun zhang State Key Laboratory of Intelligent Green Vehicle and Mobility School of Vehicle and MobilityTsinghua UniversityBeijing 100084China Key Laboratory of Conveyance and Equipment Ministry of Education East China Jiaotong UniversityNanchang 330013China Vehicle Research Center School of Mechanical EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China

Ducted fans have been extensively used in Unmanned Aerial Vehicles(UAVs)for a variety of missions because of high efficiency,high safety and low ***,as a kind of typical meteorological condition,brings significant aerodynamic interference to the ducted fan,which seriously threatens flight stability and *** this work,the numerical simulation with the Unsteady Reynolds Averaged Navier-Stokes(URANS)method and the sliding mesh technique is performed to evaluate the steady wind *** results show that the wind will lead to serious unsteady effects in the flow field,and the thrust fluctuates at the blade passing frequency of 200 *** the wind speed increases,the rotor thrust increases,the duct thrust decreases,and the total thrust changes *** instability may occur when the wind speed exceeds 8 m/*** the angle of low-speed wind increases,the rotor thrust changes little,the duct thrust increases,and the total thrust *** addition,we figure out that cases with the same crosswind ratio are similar in results,and increasing the rotating speed or fan radius is beneficial to performance improvement in *** findings are essential to the ducted fan design and UAV flight control design for stable and safe operations in wind conditions.

关键词： Unmanned Aerial Vehicle(UAV) Ducted fan Wind effect Thrust fluctuations Computational Fluid Dynamics(CFD)

Numerical investigation on unsteady characteristics of ducted fans in ground effect

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Chinese Journal of Aeronautics 2023年第9期36卷 79-95页

作者： Yiwei LUO Tianfu AI Yuhang HE Bin XU Yuping QIAN yangjun zhang State Key Laboratory of Automotive Safety and Energy School of Vehicle and MobilityTsinghua UniversityBeijing 100084China Vehicle Research Center School of Mechanical EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China

Ducted fans are widely used in various applications of Unmanned Aerial Vehicles(UAVs)due to the high efficiency,low noise and high *** unsteady characteristics of ducted fans flying near the ground are significant,which may bring stability *** this paper,the sliding mesh technology is applied and the Unsteady Reynolds Averaged Navier-Stokes(URANS)method is adopted to evaluate the influence of ground on the aerodynamic performance of ducted *** time-averaged results show that the ground leads to the decrease of duct thrust,the increase of rotor thrust and the decrease of total *** transient results show that there exist small-scale stall cells with circumferential movements in ground *** stall cells start to appear at the blade root when the height is 0.8 rotor radius distance,and arise at both the blade root and tip when the height drops to *** is found that the unsteady cells rotate between blade passages with an approximate relative speed of 30%-80%of the fan speed,and lead to thrust fluctuations up to 37%of the total *** results are essential to the flight control design of the ducted fan flying vehicle,to ensure its stability in ground effect.

关键词： Computational fluid dynamics Ducted fan Ground effect Thrust fluctuations UAV

Effects of Reynolds number on the performance of a high pressure-ratio turbocharger compressor

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Science China(Technological Sciences) 2013年第6期56卷 1361-1369页

作者： ZHENG XinQian LIN Yun GAN BinLin ZHUGE WeiLin zhang yangjun State Key Laboratory of Automotive Safety and Energy Tsinghua University Beijing Power Machinery Research Institute

The effects of Reynolds number on the performance of a high pressure-ratio turbocharger compressor were investigated by both experiments and numerical simulation. The experimental results show that the pressure ratio and the efficiency of the compressor respectively decrease by 7.9% and 6.9% when Reynolds number drops from 9.86×10 5 to 2.96×10 5 . The numerical simulation predicts a similar trend as the experimental results although it underestimates the deterioration of the performance under low Reynolds number conditions. According to simulation results, the boundary layer thickness increases at the inducer, which decreases the throat area and leads to smaller choke mass flow rate. The increments of the boundary thickness are relatively small at the rear part of the impeller. The boundary layer separation flow is severe. The interaction between boundary layer separation flows and leakage flows causes the high loss region at the rear part of the impeller passage under low Reynolds number condition.

关键词： Reynolds number high pressure-ratio turbocharger centrifugal compressor internal combustion engine

Flow Loss Mechanism in a Supercritical Carbon Dioxide Centrifugal Compressor at Low Flow Rate Conditions

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Journal of Thermal Science 2024年第1期33卷 114-125页

作者： YANG Zimu JIANG Hongsheng ZHUGE Weilin CAI Ruikai YANG Mingyang CHEN Haoxiang QIAN Yuping zhang yangjun State Key Laboratory of Automotive Safety and Energy Tsinghua UniversityBeijing 100084China School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China

With the advantages of high efficiency and compact structure,supercritical carbon dioxide(sC02)Brayton cycles have bright prospects for development in energy conversion *** one of the core components of the power cycle,the centrifugal compressor tends to operate near the critical point(304.13 K,7.3773 MPa).Normally,the compressor efficiency increases as the inlet temperature *** the inlet temperature is close to the critical point,the density increases sharply as the temperature decreases,which results in quickly decreasing of volume flow rate and efficiency *** flow loss mechanism of the sCO_(2) compressor operating at low flow rate is studied in this *** fluid dynamics(CFD) simulations for sCO_(2)compressor were carried out at various inlet temperatures and various mass flow *** the sCO_(2)compressor operates at low volume flow rate,the flow loss is generated mainly on the suction side near the trailing edge of the *** flow loss is related to the counterclockwise vortexes generated on the suction side of the main *** vortexes are caused by the flow separation in the downstream region of the impeller passage,which is different from air compressors operating at low flow *** reason for this flow separation is that the effect of Coriolis force is especially severe for the sCO_(2) fluid,compared to the viscous force and inertial *** lower flow rates,with the stronger effect of Coriolis force,the direction of relative flow velocity deviates from the direction of radius,resulting in its lower radial *** lower radial relative flow velocity leads to severe flow separation on the suction side near the trailing edge of the main blade.

关键词： supercritical CO_(2) centrifugal compressor flow loss mechanism Coriolis force