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

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

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Demonstration of a small‐scale power generator using supercritical CO_(2)

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Carbon Energy 2024年第4期6卷 269-290页

作者： Ligeng Li Hua Tian Xin Lin Xianyu Zeng Yurong Wang weilin zhuge Lingfeng Shi Xuan Wang Xingyu Liang Gequn Shu State Key Laboratory of Engines Tianjin UniversityTianjinChina Department of Thermal Science and Energy Engineering University of Science and Technology of ChinaHefeiChina State Key Laboratory of Automotive Safety and Energy Tsinghua UniversityBeijingChina

The supercritical CO_(2)(sCO_(2))power cycle could improve efficiencies for a wide range of thermal power *** sCO_(2)turbine generator plays an important role in the sCO_(2)power cycle by directly converting thermal energy into mechanical work and electric *** operation of the generator encounters challenges,including high temperature,high pressure,high rotational speed,and other engineering problems,such as *** studies of sCO_(2)turbines are insufficient because of the significant difficulties in turbine manufacturing and system *** most experimental investigations that primarily focus on 100 kW‐or MW‐scale power generation systems,we consider,for the first time,a small‐scale power generator using sCO_(2).A partial admission axial turbine was designed and manufactured with a rated rotational speed of 40,000 rpm,and a CO_(2)transcritical power cycle test loop was constructed to validate the performance of our manufactured generator.A resistant gas was proposed in the constructed turbine expander to solve the leakage *** dynamic and steady performances were *** results indicated that a peak electric power of 11.55 kW was achieved at 29,369 *** maximum total efficiency of the turbo‐generator was 58.98%,which was affected by both the turbine rotational speed and pressure ratio,according to the proposed performance map.

关键词： generator performance map power generation supercritical CO_(2) turbine

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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

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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

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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

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Effects of pulse flow and leading edge sweep on mixed flow turbines for engine exhaust heat recovery

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Science China(Technological Sciences) 2011年第2期54卷 295-301页

作者： ZHANG YangJun CHEN Li zhuge weilin ZHANG ShuYong State Key Laboratory of Automotive Safety and Energy Tsinghua University Beijing 100084 China National Key Laboratory of Diesel Engine Turbocharging Technology P.O.B. 22 Datong 037036 China

Recovery of heat energy from internal combustion engine exhaust will achieve significant road transportation CO2 reduction. Turbocharging and turbogenerating are most commonly used technologies to recover engine exhaust heat *** exhaust pulse flow can significantly affect the turbine performance of turbocharging and turbogenerating systems,and it is necessary to consider the pulse flow effects in turbine design and performance *** investigation was carried out by numerical simulation on the mixed flow turbine pulse flow performance and flow *** showed that the variations of the turbine efficiency and flowfiled under pulsating flow conditions demonstrate significant unsteady *** effect of blade leading edge sweep on turbine pulse flow performance was *** is shown that increasing of the leading edge sweep angle can improve the turbine average instantaneous efficiency by about 2 percent under pulsating flow conditions.

关键词：涡轮发动机脉冲流余热回收优势混流式数值模拟方法热能回收涡轮增压

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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：低雷诺数涡轮增压器压缩机压力比性能边界层厚度数值模拟模拟预测

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Recent Progress of Bionic Hierarchical Structure in the Field of Thermal Insulation Protection

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Journal of Bionic Engineering 2024年第1期21卷 1-18页

作者： Yina zhuge Fujuan Liu National Engineering Laboratory for Modern Silk College of Textile and Clothing EngineeringSoochow UniversitySuzhou 215123China

Some living organisms with hierarchical structures in nature have received extensive attention in various *** hierarchical structure with multiple pores,a large number of solid-gas interfaces and tortuous conduction paths provide a new direction for the development of thermal insulation materials,making the living creatures under these extreme conditions become the bionic objects of scientific *** this review,the research progress of bionic hierarchical structure in the field of heat insulation is *** bears,cocoons,penguin feathers and wool are typical examples of heat preservation hierarchy in nature to introduce their morphological *** the same time,the thermal insulation mechanism,fractal model and several preparation methods of bionic hierarchical structures are emphatically *** application of hierarchical structures in various fields,especially in thermal insulation and infrared thermal stealth,is ***,the hierarchical structure is prospected.

关键词： Hierarchical structure Bionic Heat insulation Fractal model Cocoons

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Thermal Performance of a Micro Heat Pipe Array for Battery Thermal Management Under Special Vehicle-Operating Conditions

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Automotive Innovation 2020年第4期3卷 317-327页

作者： Chengning Yao Dan Dan Yangjun Zhang Yueqi Wang Yuping Qian Yuying Yan weilin zhuge State Key Laboratory of Automotive Safety and Energy Tsinghua UniversityBeijing 100084China Fluids and Thermal Engineering Research Group Faculty of EngineeringUniversity of NottinghamNottingham NG72RDUK

The thermal management of battery systems is critical for maintaining the energy storage capacity,life span,and thermal safety of batteries used in electric vehicles,because the operating temperature is a key factor affecting battery *** temperature rises and large temperature differences accelerate the degradation rate of such ***,the increasing demand for fast charging and special on-vehicle scenarios has increased the heat dissipation requirements of battery thermal management *** address this demand,this work proposes a novel micro heat pipe array(MHPA)for thermal management under a broadened research scope,including high heat generation rates,large tilt angles,mild vibration,and distributed heat generation *** experimental results indicate that the temperature difference is maintained 3.44°C at a large heat generation of 50 W for a limited range of tilt ***,a mild vehicle vibra-tion condition was found to improve temperature uniformity by 3.3°C at a heat generation of 10 ***,the use of distributed heat sources results in a temperature variation of 3.88°C,suggesting that the heat generation distribution needs to be considered in thermal *** the effects of these special battery-operating conditions on the MHPA could significantly contribute to the enhancement of heat transfer capability and temperature uniformity improvement of battery thermal management systems based on heat pipe *** would facilitate the realization of meeting the higher requirements of future battery systems.

关键词： Battery thermal management Thermal performance Micro heat pipe array Operating conditions

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Change of probability density distributions of summer temperatures in different climate zones

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Frontiers of Earth Science 2024年第1期18卷 1-16页

作者： Xinqiu OUYANG weilin LIAO Ming LUO Guangdong Key Laboratory for Urbanization and Geo-simulation School of Geography and PlanningSun Yat-sen UniversityGuangzhou 510006China Institute of Environment Energy and SustainabilityThe Chinese University of Hong KongHong Kong 999077China

Extreme events have become increasingly frequent worldwide which are reflected in diverse changes in the shape of the temperature probability density ***,few studies have paid attention to the heterogeneity of temperature at the scale of climate ***,we use the ERA5-land data set to explore interdecadal summer temperature changes and the distribution across different climate zones from 1981 to *** the minimum(Tmin)and maximum(Tmax)temperature of 1982–1991 and 2010–2019,the results imply that Tmin and Tmax in summer maintained a notable upward trend over the past 40 years,especially *** effects of a simple shift toward a warmer climate contributed most to all climate zones,while the standard deviation,skewness and kurtosis had minor effects on extreme temperature except for *** analysis shows that the probability of extreme events in all climate zones is increasing in frequency and intensity,especially Tmin and Tmax in temperate climate *** diverse reasons for climate change can assist us with taking different measures to address extreme climate in distinct climate zones.

关键词： Climate change probability density function extreme events

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