Pub Date : 2024-05-30DOI: 10.1177/09576509241257727
Ramazan Şener, M Eşref Demir
Turbulators are used in heat exchangers to increase the contact surfaces of fluids and enhance heat transfer rates by promoting turbulence flow. This is particularly important in applications that require high productivity and capabilities. The use of turbulators can lead to maximum energy efficiency, resulting in high efficiency and lower costs. This investigation presents a comprehensive experimental and computational fluid dynamics (CFD) approach into the influence of turbulator-induced disturbances on heat transfer characteristics in a double pipe heat exchanger. In this study, two innovative turbulators (named TY and TZ) were designed to enhance the performance of heat exchangers. The turbulators are inserted into the inner pipe of the double pipe heat exchanger. According to the experimental and numerical results, compared to the plain pipe condition (without turbulator), it was observed that maximum temperature differences were reached with a 28% increase at velocity of 2.5 m/s with TY and 118% increase at velocity of 3 m/s with TZ. Nusselt numbers increased by 32% with TY and by 157.9% with TZ compared to the plain pipe condition. Therefore, TZ turbulator with a simple structure can significantly enhance the heat transfer performance of double-pipe heat exchangers, making it an ideal option for use in these exchangers.
{"title":"Heat transfer and flow characteristics of a novel turbulator design in heat exchanger: Experimental and numerical analysis","authors":"Ramazan Şener, M Eşref Demir","doi":"10.1177/09576509241257727","DOIUrl":"https://doi.org/10.1177/09576509241257727","url":null,"abstract":"Turbulators are used in heat exchangers to increase the contact surfaces of fluids and enhance heat transfer rates by promoting turbulence flow. This is particularly important in applications that require high productivity and capabilities. The use of turbulators can lead to maximum energy efficiency, resulting in high efficiency and lower costs. This investigation presents a comprehensive experimental and computational fluid dynamics (CFD) approach into the influence of turbulator-induced disturbances on heat transfer characteristics in a double pipe heat exchanger. In this study, two innovative turbulators (named TY and TZ) were designed to enhance the performance of heat exchangers. The turbulators are inserted into the inner pipe of the double pipe heat exchanger. According to the experimental and numerical results, compared to the plain pipe condition (without turbulator), it was observed that maximum temperature differences were reached with a 28% increase at velocity of 2.5 m/s with TY and 118% increase at velocity of 3 m/s with TZ. Nusselt numbers increased by 32% with TY and by 157.9% with TZ compared to the plain pipe condition. Therefore, TZ turbulator with a simple structure can significantly enhance the heat transfer performance of double-pipe heat exchangers, making it an ideal option for use in these exchangers.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141189928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-27DOI: 10.1177/09576509241256499
Xiaosong Xia, Shaogan Ye, Liang Hou, Dehui Wu, Quan Lin
Accurate calculation of instantaneous flow area is of great significance for modeling an axial piston pump. A point cloud based technique is developed to calculate the instantaneous flow area, and used to perform a parametric analysis of key parameters on the pump fluid dynamics. First, a model is developed to analyze the fluid dynamics of the axial piston pump. Second, three techniques used to obtain the instantaneous flow area are described, with focus on the detailed description of the point cloud technique. The instantaneous flow areas are compared, and the accuracy of the pump model using the obtained instantaneous flow areas are verified by comparing the output pressure. Last, a comprehensive parametric study is conducted concerning the effects of the fillet radius and diversion position of the triangular groove on the pressure in the piston chamber and flow rate at the output port based on the point cloud technique. The results shown that the computation time of the point cloud technique is only 1% of the Computational Fluid Dynamics (CFD) technique, with a total computational error of less than 2.5%, and the triangular groove inside the pitch circle with a small fillet radius is beneficial for reductions of pressure and flow rate ripples.
{"title":"Instantaneous flow area calculation for modeling an axial piston pump: A point cloud-based technique","authors":"Xiaosong Xia, Shaogan Ye, Liang Hou, Dehui Wu, Quan Lin","doi":"10.1177/09576509241256499","DOIUrl":"https://doi.org/10.1177/09576509241256499","url":null,"abstract":"Accurate calculation of instantaneous flow area is of great significance for modeling an axial piston pump. A point cloud based technique is developed to calculate the instantaneous flow area, and used to perform a parametric analysis of key parameters on the pump fluid dynamics. First, a model is developed to analyze the fluid dynamics of the axial piston pump. Second, three techniques used to obtain the instantaneous flow area are described, with focus on the detailed description of the point cloud technique. The instantaneous flow areas are compared, and the accuracy of the pump model using the obtained instantaneous flow areas are verified by comparing the output pressure. Last, a comprehensive parametric study is conducted concerning the effects of the fillet radius and diversion position of the triangular groove on the pressure in the piston chamber and flow rate at the output port based on the point cloud technique. The results shown that the computation time of the point cloud technique is only 1% of the Computational Fluid Dynamics (CFD) technique, with a total computational error of less than 2.5%, and the triangular groove inside the pitch circle with a small fillet radius is beneficial for reductions of pressure and flow rate ripples.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141165575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-25DOI: 10.1177/09576509241254416
Ruibing Wu, Zhuoxiong Zeng, Hong Liu, Kaifang Guo
In order to investigate the premixed combustion characteristics of CH4/H2/air in a micro-mixing combustor, the effects of different micro-mixing head-ends (HE1, HE2, HE3) and hydrogen mixing ratios on the temperature distribution, heat transfer process, emission characteristic, flames shape are analyzed. The results show that compared with swirl head-end combustion, the micro-mixing combustion performance is better. Among the three head-ends, HE3 has the best combustion characteristics and stable flames. The temperature distribution in the high-temperature zone is uniform, and low-temperature zone is concentrated near the jet, which can suppress the flashback. The velocity and temperature gradient near the central axis of jet streams show a strong synergistic effect. The flames are plume shaped and flames stability is mainly influenced by the H2 combustion process. Increasing the jet diameter, decreasing the jet spacing and increasing the hydrogen mixing ratio all contribute to the flames stability, but these three methods can stabilize the flames by affecting fluid Reynolds number, interaction between small flames and combustion rate, respectively. Moreover, small jet diameter and high hydrogen mixing ratio can reduce OTDF, which contributes to improve outlet temperature uniformity.
{"title":"Numerical investigation of CH4/H2/air micro-mixing combustion flow in a micro gas turbine combustor with different head-end structures","authors":"Ruibing Wu, Zhuoxiong Zeng, Hong Liu, Kaifang Guo","doi":"10.1177/09576509241254416","DOIUrl":"https://doi.org/10.1177/09576509241254416","url":null,"abstract":"In order to investigate the premixed combustion characteristics of CH<jats:sub>4</jats:sub>/H<jats:sub>2</jats:sub>/air in a micro-mixing combustor, the effects of different micro-mixing head-ends (HE1, HE2, HE3) and hydrogen mixing ratios on the temperature distribution, heat transfer process, emission characteristic, flames shape are analyzed. The results show that compared with swirl head-end combustion, the micro-mixing combustion performance is better. Among the three head-ends, HE3 has the best combustion characteristics and stable flames. The temperature distribution in the high-temperature zone is uniform, and low-temperature zone is concentrated near the jet, which can suppress the flashback. The velocity and temperature gradient near the central axis of jet streams show a strong synergistic effect. The flames are plume shaped and flames stability is mainly influenced by the H<jats:sub>2</jats:sub> combustion process. Increasing the jet diameter, decreasing the jet spacing and increasing the hydrogen mixing ratio all contribute to the flames stability, but these three methods can stabilize the flames by affecting fluid Reynolds number, interaction between small flames and combustion rate, respectively. Moreover, small jet diameter and high hydrogen mixing ratio can reduce OTDF, which contributes to improve outlet temperature uniformity.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141148889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-21DOI: 10.1177/09576509241254578
Qi-an Xie, Hu Wu, Li-ping Deng
The variable geometry methods currently used in combined-cycle gas turbines are compressor variable inlet guide vanes (VIGV) or power turbine variable area nozzles (VAN). On this basis, this study presents the optimal variable geometry control strategy for compressor and power turbine combined adjustment ([Formula: see text]) using the Differential Evolutionary Algorithm with the LM2500+ gas turbine. The aim is to further improve the part-load performance of the combined-cycle gas turbine. Firstly, a part-load performance prediction model for variable geometry gas turbines is established based on the component method. Subsequently, a variable geometry gas turbine part-load performance optimization model is developed by combining the Differential Evolution Algorithm. Finally, the optimum combination of stagger angles for the compressor inlet vane and power turbine nozzle is calculated at each part-load condition. Compared to the VIGV and VAN control strategies, the [Formula: see text] control strategy proposed in this paper shows a higher stability margin and better economy. The [Formula: see text] control strategy maintains a constant exhaust temperature within a part load range from 20% to 100% with the stability margin exceeding 14%. In comparison with the VAN control strategy, the fuel flow rate decreases by 1.152% at 45% relative load power and by 3.435% at 20.0% relative load power with the [Formula: see text] control strategy.
{"title":"Improving part-load performance of combined-cycle gas turbines by optimizing variable geometry control strategy for compressor and power turbine combined adjustment","authors":"Qi-an Xie, Hu Wu, Li-ping Deng","doi":"10.1177/09576509241254578","DOIUrl":"https://doi.org/10.1177/09576509241254578","url":null,"abstract":"The variable geometry methods currently used in combined-cycle gas turbines are compressor variable inlet guide vanes (VIGV) or power turbine variable area nozzles (VAN). On this basis, this study presents the optimal variable geometry control strategy for compressor and power turbine combined adjustment ([Formula: see text]) using the Differential Evolutionary Algorithm with the LM2500+ gas turbine. The aim is to further improve the part-load performance of the combined-cycle gas turbine. Firstly, a part-load performance prediction model for variable geometry gas turbines is established based on the component method. Subsequently, a variable geometry gas turbine part-load performance optimization model is developed by combining the Differential Evolution Algorithm. Finally, the optimum combination of stagger angles for the compressor inlet vane and power turbine nozzle is calculated at each part-load condition. Compared to the VIGV and VAN control strategies, the [Formula: see text] control strategy proposed in this paper shows a higher stability margin and better economy. The [Formula: see text] control strategy maintains a constant exhaust temperature within a part load range from 20% to 100% with the stability margin exceeding 14%. In comparison with the VAN control strategy, the fuel flow rate decreases by 1.152% at 45% relative load power and by 3.435% at 20.0% relative load power with the [Formula: see text] control strategy.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141116268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-09DOI: 10.1177/09576509241252877
Tianxiao Zhao, Zhenyu Jiang, Guangyu Mo, GuoJie Wang, Jie Gao
Gas turbines cannot be directly reversed, and the astern operation of gas turbines still requires additional power transmission equipment to be achieved. To compensate for this deficiency, the application of turbine-blade-tip turbine in gas turbines was proposed. Turbine-blade-tip turbines have the characteristics of extremely low solidity and extremely high diameter-span ratio. Compared with conventional turbine blades, the capacity of turbine blades to restrain gas flow is greatly weakened, the separation flow is obvious when going astern, resulting in low efficiency. For the control problem of low solidity turbine-blade-tip turbines separation flow, a splitter blade control strategy is selected to suppress the separation flow. Adding a splitter blade between original rotor blades effectively improves the ability of rotor blades to restrain gas flow, significantly reduces separation phenomena, and significantly improves efficiency. As the axial chord length of the splitter blade shortens, the inhibitory effect on the separation flow decreases, and the ability of splitter blades to improve the efficiency gradually descends.
{"title":"Control of separation flows of turbine-blade-tip turbines by splitter blades","authors":"Tianxiao Zhao, Zhenyu Jiang, Guangyu Mo, GuoJie Wang, Jie Gao","doi":"10.1177/09576509241252877","DOIUrl":"https://doi.org/10.1177/09576509241252877","url":null,"abstract":"Gas turbines cannot be directly reversed, and the astern operation of gas turbines still requires additional power transmission equipment to be achieved. To compensate for this deficiency, the application of turbine-blade-tip turbine in gas turbines was proposed. Turbine-blade-tip turbines have the characteristics of extremely low solidity and extremely high diameter-span ratio. Compared with conventional turbine blades, the capacity of turbine blades to restrain gas flow is greatly weakened, the separation flow is obvious when going astern, resulting in low efficiency. For the control problem of low solidity turbine-blade-tip turbines separation flow, a splitter blade control strategy is selected to suppress the separation flow. Adding a splitter blade between original rotor blades effectively improves the ability of rotor blades to restrain gas flow, significantly reduces separation phenomena, and significantly improves efficiency. As the axial chord length of the splitter blade shortens, the inhibitory effect on the separation flow decreases, and the ability of splitter blades to improve the efficiency gradually descends.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140938220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-02DOI: 10.1177/09576509241249216
Cuizhen Zhang, Xuan Gao, Kun Zhu, Yongmei Wang, Yingjie Liu, Fengming Wang, Shuai Yin
This study aims to develop a reliable numerical model for predicting the supercritical heat transfer of aviation kerosene RP-3 in a tube under heating conditions, thereby providing a reference for revealing the mechanism behind the experimental phenomena. Based on validation studies between seven turbulence models and experiments, a numerical method using the Yang-Shih turbulence model is proposed. A detailed prediction of the turbulent flow process is obtained, and the heat transfer characteristics of RP-3 are analyzed. The evolution of parameters and properties in axial and radial directions is demonstrated, followed by investigations of the effects of system pressure, fuel inlet temperature, and mass flow rate. The drastic change in the specific heat of the fuel when its temperature is close to the pseudocritical value and the temperature difference between the area near the wall and the center of the tube are the main causes of the enhancement and deterioration of the heat exchange. A higher inlet temperature increases the heat transfer coefficient, but due to its different effects on decreasing the density and the viscosity, it increases the pressure drop. In addition, larger mass flow rates can promote turbulence intensity and heat transfer, but cause a higher pressure drop across the tube.
{"title":"Numerical investigations on heat transfer of supercritical RP-3 flowing in circular tube","authors":"Cuizhen Zhang, Xuan Gao, Kun Zhu, Yongmei Wang, Yingjie Liu, Fengming Wang, Shuai Yin","doi":"10.1177/09576509241249216","DOIUrl":"https://doi.org/10.1177/09576509241249216","url":null,"abstract":"This study aims to develop a reliable numerical model for predicting the supercritical heat transfer of aviation kerosene RP-3 in a tube under heating conditions, thereby providing a reference for revealing the mechanism behind the experimental phenomena. Based on validation studies between seven turbulence models and experiments, a numerical method using the Yang-Shih turbulence model is proposed. A detailed prediction of the turbulent flow process is obtained, and the heat transfer characteristics of RP-3 are analyzed. The evolution of parameters and properties in axial and radial directions is demonstrated, followed by investigations of the effects of system pressure, fuel inlet temperature, and mass flow rate. The drastic change in the specific heat of the fuel when its temperature is close to the pseudocritical value and the temperature difference between the area near the wall and the center of the tube are the main causes of the enhancement and deterioration of the heat exchange. A higher inlet temperature increases the heat transfer coefficient, but due to its different effects on decreasing the density and the viscosity, it increases the pressure drop. In addition, larger mass flow rates can promote turbulence intensity and heat transfer, but cause a higher pressure drop across the tube.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140836955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-02DOI: 10.1177/09576509241251909
Xuedi Hao, Zeyuan Zhang, Jinling Chi, Lei Sun, Jiajin Zhang
A compressor map is usually represented by a limited number of feature points to speculate the entire operating range. Also, accurate compressor map models can be obtained quickly by using the appropriate methods. In this paper, 9351FA gas turbine is used as the research object, and a set of targeted compressor map speculation scheme is proposed. At 15 data points, high-precision compressor maps are obtained based on BP neural network, and this method is suitable for a large number of data points. At 6 data points, compressor maps are obtained based on the parameter estimation method, and this method is suitable for a small number of data points. The mean square deviation of the compressor map obtained by the neural network is about 0.002, while the minimum mean square deviation of the results of the parameter estimation method is 0.026 and the maximum mean square deviation is 0.088. Since the corrected speed line of 106.4 is almost vertical, the maximum error mean squared deviation and the maximum standard deviation occur on this line. Both methods are suitable for different sample sizes, and the speculated compressor maps are more reliable. The combination of the two methods can provide a set of reference methods for compressor map speculation.
{"title":"Research on speculation method for compressor map of PG9351FA gas turbine","authors":"Xuedi Hao, Zeyuan Zhang, Jinling Chi, Lei Sun, Jiajin Zhang","doi":"10.1177/09576509241251909","DOIUrl":"https://doi.org/10.1177/09576509241251909","url":null,"abstract":"A compressor map is usually represented by a limited number of feature points to speculate the entire operating range. Also, accurate compressor map models can be obtained quickly by using the appropriate methods. In this paper, 9351FA gas turbine is used as the research object, and a set of targeted compressor map speculation scheme is proposed. At 15 data points, high-precision compressor maps are obtained based on BP neural network, and this method is suitable for a large number of data points. At 6 data points, compressor maps are obtained based on the parameter estimation method, and this method is suitable for a small number of data points. The mean square deviation of the compressor map obtained by the neural network is about 0.002, while the minimum mean square deviation of the results of the parameter estimation method is 0.026 and the maximum mean square deviation is 0.088. Since the corrected speed line of 106.4 is almost vertical, the maximum error mean squared deviation and the maximum standard deviation occur on this line. Both methods are suitable for different sample sizes, and the speculated compressor maps are more reliable. The combination of the two methods can provide a set of reference methods for compressor map speculation.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140837117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The safe operation of closed-Bryton-cycle system is hindered by the nonlinear real gas properties in a supercritical carbon dioxide (SCO2) centrifugal compressor for waste heat recovery in a powertrain system. This paper aims to understand the influence of real gas properties on the aerodynamic stability of a shrouded SCO2 centrifugal compressor designed for waste heat recovery. Firstly, the numerical method was calibrated and validated using experimental results from the Sandia SCO2 centrifugal compressor. Next, based on the numerical method, the stability performance of an inhouse-design shrouded SCO2 compressor was discussed through a direct comparison with the identical compressor using air. The results showed that the performance of the SCO2 compressor was significantly different from that of the air compressor. Particularly, the impeller was the most unstable component featuring a notable recirculating region near the shroud at the leading edge. Further analysis is carried out to understand the discrepancies in the stability performance between the two compressors with different fluids. It is revealed that the boundary layer on the SCO2 impeller suction surface thickens at a faster rate, leading to stronger flow separation. Meanwhile, the stronger accumulation of low-momentum secondary flow near the SCO2 impeller outlet enhances the ‘wake’ structure near the shroud of suction surface at the impeller tailing edge, resulting in considerable backflow. The different behaviors of boundary layer were attributed to pressure gradient normal to the suction surface. Specifically, the pressure gradient on the suction surface for SCO2 impeller is orders of magnitude higher than that of the air impeller. The stronger gradient weakens momentum exchange in the boundary layer, thus increasing the thickness of boundary layer more rapidly along the streamwise direction. Moreover, the boundary layer is pushed towards the shroud of suction surface by the strong pressure gradient, resulting in the evident accumulation of secondary flow nearby. At the meantime, the low-momentum flow near the impeller outlet reduced the inlet flow velocity of the diffuser, causing more recirculation at the top of the vaneless diffuser in all circumferential directions, thus worsening its instability.
{"title":"Influence of real gas properties on aerodynamic stability of a SCO2 centrifugal compressor","authors":"Ruikai Cai, Mingyang Yang, Weilin Zhuge, Bijie Yang, Ricardo Martinez-Botas, Yangjun Zhang","doi":"10.1177/09576509241248885","DOIUrl":"https://doi.org/10.1177/09576509241248885","url":null,"abstract":"The safe operation of closed-Bryton-cycle system is hindered by the nonlinear real gas properties in a supercritical carbon dioxide (SCO<jats:sub>2</jats:sub>) centrifugal compressor for waste heat recovery in a powertrain system. This paper aims to understand the influence of real gas properties on the aerodynamic stability of a shrouded SCO<jats:sub>2</jats:sub> centrifugal compressor designed for waste heat recovery. Firstly, the numerical method was calibrated and validated using experimental results from the Sandia SCO<jats:sub>2</jats:sub> centrifugal compressor. Next, based on the numerical method, the stability performance of an inhouse-design shrouded SCO<jats:sub>2</jats:sub> compressor was discussed through a direct comparison with the identical compressor using air. The results showed that the performance of the SCO<jats:sub>2</jats:sub> compressor was significantly different from that of the air compressor. Particularly, the impeller was the most unstable component featuring a notable recirculating region near the shroud at the leading edge. Further analysis is carried out to understand the discrepancies in the stability performance between the two compressors with different fluids. It is revealed that the boundary layer on the SCO<jats:sub>2</jats:sub> impeller suction surface thickens at a faster rate, leading to stronger flow separation. Meanwhile, the stronger accumulation of low-momentum secondary flow near the SCO<jats:sub>2</jats:sub> impeller outlet enhances the ‘wake’ structure near the shroud of suction surface at the impeller tailing edge, resulting in considerable backflow. The different behaviors of boundary layer were attributed to pressure gradient normal to the suction surface. Specifically, the pressure gradient on the suction surface for SCO<jats:sub>2</jats:sub> impeller is orders of magnitude higher than that of the air impeller. The stronger gradient weakens momentum exchange in the boundary layer, thus increasing the thickness of boundary layer more rapidly along the streamwise direction. Moreover, the boundary layer is pushed towards the shroud of suction surface by the strong pressure gradient, resulting in the evident accumulation of secondary flow nearby. At the meantime, the low-momentum flow near the impeller outlet reduced the inlet flow velocity of the diffuser, causing more recirculation at the top of the vaneless diffuser in all circumferential directions, thus worsening its instability.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140837271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-29DOI: 10.1177/09576509241250128
Sergio M Moreno-Buesa, Emilio Muñoz-Cerón, Gustavo Nofuentes Garrido, Slawomir Gulkowski, Juan de la Casa Higueras, Jorge Aguilera Tejero
Bifacial solar technology has experienced exponential growth in recent years and its trend is increasing for the coming years. Considering the advantages that it offers over monofacial technology such as its current price equivalence, the increase in performance thanks to the production of the rear face and the consecutive reduction of the LCOE, it is logical that more and more photovoltaic plants with this technology are been installed. Nowadays, there are some regulatory gaps regarding bifacial technology and, due to this growing trend, it is necessary to study, research and implement the optimal way to evaluate these systems. This article has experimented with a 3.3 kW bifacial photovoltaic system, divided into two strings with different configurations, whose monitoring system has all the instrumentation included in the IEC 61,724 standard, with the addition that it has several rear irradiance sensors arranged in different locations of the system to evaluate the variability of this parameter. After an experimental campaign of 9 months, a power estimation analysis and the calculation of the PR and PR25°C have been carried out using the different rear irradiance sensors. The variability of this parameter depending on the location of the sensor has affected the results in such a way that the RMSE committed in the power estimation has varied between 10.22% and 2.63%, while the PR and PR25°C of the system has oscillated between 0.84 for the most unfavorable case and 0.95 in the most favorable case. Assumed the great variability between performance ratios, it is necessary to establish a specific normative standard for the evaluation of Bifacial PV systems.
{"title":"Characterization of bifacial technology Pv systems","authors":"Sergio M Moreno-Buesa, Emilio Muñoz-Cerón, Gustavo Nofuentes Garrido, Slawomir Gulkowski, Juan de la Casa Higueras, Jorge Aguilera Tejero","doi":"10.1177/09576509241250128","DOIUrl":"https://doi.org/10.1177/09576509241250128","url":null,"abstract":"Bifacial solar technology has experienced exponential growth in recent years and its trend is increasing for the coming years. Considering the advantages that it offers over monofacial technology such as its current price equivalence, the increase in performance thanks to the production of the rear face and the consecutive reduction of the LCOE, it is logical that more and more photovoltaic plants with this technology are been installed. Nowadays, there are some regulatory gaps regarding bifacial technology and, due to this growing trend, it is necessary to study, research and implement the optimal way to evaluate these systems. This article has experimented with a 3.3 kW bifacial photovoltaic system, divided into two strings with different configurations, whose monitoring system has all the instrumentation included in the IEC 61,724 standard, with the addition that it has several rear irradiance sensors arranged in different locations of the system to evaluate the variability of this parameter. After an experimental campaign of 9 months, a power estimation analysis and the calculation of the PR and PR<jats:sub>25°C</jats:sub> have been carried out using the different rear irradiance sensors. The variability of this parameter depending on the location of the sensor has affected the results in such a way that the RMSE committed in the power estimation has varied between 10.22% and 2.63%, while the PR and PR<jats:sub>25°C</jats:sub> of the system has oscillated between 0.84 for the most unfavorable case and 0.95 in the most favorable case. Assumed the great variability between performance ratios, it is necessary to establish a specific normative standard for the evaluation of Bifacial PV systems.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140837442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper proposes the circulation redistribution for the low-pressure (LP) rotor of a highly-loaded vaneless counter-rotating turbine (VCRT) to reduce the LP shock losses. The method is to decrease the mid-span circulation and increase the tip circulation at the exit of the LP rotor with unchanged high-pressure (HP) and LP power output. The LP Blade-to-Blade flow field can be considered as a Laval nozzle model. And the high static pressure drop from the throat to the exit results in strong trailing edge (TE) shocks near the LP mid-span. Also, the suction side TE shock (ST) and the reflected shock of the pressure side TE shock (RPT) near the LP mid-span merge into a relatively strong shock very close to the TE. These two factors result in high shock losses. To reduce the shock losses under the design condition, decreasing the stagger angle and the blade exit angle near the LP mid-span are adopted to reduce the LP mid-span exit circulation. This changes the throat area to exit area ratio near the LP mid-span, prompting the actual static pressure drop from the throat to the exit to be reduced and closer to the theoretical value, so that the TE shock strength is reduced. Besides, the intersection of the RPT and the ST is delayed owing to the improved flow angle distributions near the TE, further contributing to the LP mid-span shock loss reduction. Since the LP power output is decreased and the LP tip-leakage flow (TLF) losses are far lower than the HP TLF losses, increasing the stagger angle and the blade exit angle in LP tip regions are employed to increase the LP exit circulation and decrease the HP exit circulation in tip regions. Then the HP and LP efficiency are both raised with unchanged HP and LP power output after optimizing the blade profiles near the mid-span and in tip regions of the LP rotor. The remarkable thing is that the TE shock strength in LP tip and root regions are both reduced after improved because of the decreased ratio of the exit area to the throat area. And the intersection of the RPT and the ST in LP tip and root regions are also both delayed, leading to reduced shock losses. The reduced TE shock losses along the whole LP span appreciably raise the LP and VCRT efficiency by 0.96% and 0.32% respectively.
本文提出了对高负荷无叶片反转涡轮机（VCRT）的低压（LP）转子进行环流再分配以减少低压冲击损失的方法。该方法是在高压（HP）和低压（LP）功率输出不变的情况下，减少低压转子出口处的中跨环流并增加叶尖环流。LP 叶片间流场可视为拉瓦尔喷嘴模型。从喉部到出口的高静压降导致 LP 中跨附近产生强烈的后缘（TE）冲击。此外，在 LP 中跨附近，吸气侧 TE 冲击 (ST) 和压力侧 TE 冲击的反射冲击 (RPT) 汇合成一个相对较强的冲击，非常靠近 TE。这两个因素导致了较高的冲击损失。为减少设计条件下的冲击损失，可采用减小 LP 中跨附近的交错角和叶片出口角的方法来减小 LP 中跨出口环流。这就改变了 LP 中跨附近的喉部面积与出口面积比，促使喉部到出口的实际静压降减小，更接近理论值，从而降低了 TE 冲击强度。此外，由于改善了 TE 附近的流角分布，RPT 与 ST 的交点被推迟，进一步促进了 LP 中跨冲击损失的降低。由于 LP 功率输出下降，而 LP 尖端泄漏流（TLF）损失远低于 HP TLF 损失，因此采用增加 LP 尖端区域的交错角和叶片出口角的方法来增加 LP 出口环流，减少 HP 尖端区域的出口环流。优化 LP 转子中跨附近和叶尖区域的叶片轮廓后，在 HP 和 LP 功率输出不变的情况下，HP 和 LP 效率都得到了提高。值得注意的是，由于出口面积与喉部面积的比值减小，改进后 LP 叶尖和叶根区域的 TE 冲击强度均有所降低。而且 LP 尖端和根部区域的 RPT 和 ST 的交点也都延迟了，从而减少了冲击损失。整个 LP 跨度上的 TE 冲击损失减少后，LP 和 VCRT 的效率分别显著提高了 0.96% 和 0.32%。
{"title":"A shock loss reduction method for the low-pressure rotor of a vaneless counter-rotating turbine using circulation redistribution","authors":"Tian-tian Dong, Zhao Wei, Xiu-ming Sui, Pu Jian, Wei-wei Luo, Qing-jun Zhao","doi":"10.1177/09576509241248882","DOIUrl":"https://doi.org/10.1177/09576509241248882","url":null,"abstract":"This paper proposes the circulation redistribution for the low-pressure (LP) rotor of a highly-loaded vaneless counter-rotating turbine (VCRT) to reduce the LP shock losses. The method is to decrease the mid-span circulation and increase the tip circulation at the exit of the LP rotor with unchanged high-pressure (HP) and LP power output. The LP Blade-to-Blade flow field can be considered as a Laval nozzle model. And the high static pressure drop from the throat to the exit results in strong trailing edge (TE) shocks near the LP mid-span. Also, the suction side TE shock (ST) and the reflected shock of the pressure side TE shock (RPT) near the LP mid-span merge into a relatively strong shock very close to the TE. These two factors result in high shock losses. To reduce the shock losses under the design condition, decreasing the stagger angle and the blade exit angle near the LP mid-span are adopted to reduce the LP mid-span exit circulation. This changes the throat area to exit area ratio near the LP mid-span, prompting the actual static pressure drop from the throat to the exit to be reduced and closer to the theoretical value, so that the TE shock strength is reduced. Besides, the intersection of the RPT and the ST is delayed owing to the improved flow angle distributions near the TE, further contributing to the LP mid-span shock loss reduction. Since the LP power output is decreased and the LP tip-leakage flow (TLF) losses are far lower than the HP TLF losses, increasing the stagger angle and the blade exit angle in LP tip regions are employed to increase the LP exit circulation and decrease the HP exit circulation in tip regions. Then the HP and LP efficiency are both raised with unchanged HP and LP power output after optimizing the blade profiles near the mid-span and in tip regions of the LP rotor. The remarkable thing is that the TE shock strength in LP tip and root regions are both reduced after improved because of the decreased ratio of the exit area to the throat area. And the intersection of the RPT and the ST in LP tip and root regions are also both delayed, leading to reduced shock losses. The reduced TE shock losses along the whole LP span appreciably raise the LP and VCRT efficiency by 0.96% and 0.32% respectively.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140664086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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