A wave rotor is suitable for compact and efficient pressure-exchange between gas flows.This work measured the circumferential pressure distribution of the rotor/stator interfaces and utilized a CFD method to simulate ...A wave rotor is suitable for compact and efficient pressure-exchange between gas flows.This work measured the circumferential pressure distribution of the rotor/stator interfaces and utilized a CFD method to simulate the unsteady pressure waves.The experimental and CFD results showed some slopes in the circumferential pressure distributions,and the slopes indicated the traces of specific unsteady pressure waves.Such traces varied regularly if the rotational speed varied within a range from-11%to+11%off the baseline value,but they were seriously disturbed if the rotational speed varied by-45%from the baseline value.It verified that a pressure wave in a wave rotor tended to keep its pressure ratio and propagation velocity unchanged if the rotational speed varied by a small extent,and that the pressure wave could not keep its propagation patterns if the rotational speed varied by a large extent.Because of the pressure wave behaviors,the wave rotor demonstrated specific regulations of the rotational speed effects on its operational states.展开更多
Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column（OWC） wave energy converters, which can rotate in the same direction under the bi-directional air f...Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column（OWC） wave energy converters, which can rotate in the same direction under the bi-directional air flows. A numerical model established in Fluent is validated by the corresponding experimental results. The flow fields, pressure distribution and dimensionless evaluating coefficients can be calculated and analyzed. Effects of the rotor solidity varying with the change of blade number are investigated and the suitable solidity value is recommended for different flow coefficients.展开更多
This paper establishes a simplified test system for internal combustion wave rotor with a single channel and designs different intensifying combustion obstacles and arrangements. Moreover, this paper analyzes the inte...This paper establishes a simplified test system for internal combustion wave rotor with a single channel and designs different intensifying combustion obstacles and arrangements. Moreover, this paper analyzes the intensifying effect of obstacles on combustion process of the internal combustion wave rotor from the stable operation range, pressure gain and flame progression process perspective. The results show that the range of inlet velocity under stable operation of the internal combustion wave rotor narrows after the addition of obstacles, and the corresponding velocity values substantially reduce while the flame propagation speed can be improved by 2 - 4 times. At the rotation rate of 1500 rpm, the pressure gain increases significantly during the combustion process. These results provide technical supports for further research and application of the internal combustion wave rotor.展开更多
This paper presents a new type of double-helical rotor wave energy converter(WEC),which consists of two isolated sets of helical rotor structures(inner and outer).This device can generate electricity by using the risi...This paper presents a new type of double-helical rotor wave energy converter(WEC),which consists of two isolated sets of helical rotor structures(inner and outer).This device can generate electricity by using the rising and falling energy of a wave.The rotors are simulated and optimized by Fluent.Each rotor’s blades are simulated and analyzed,which are separately changed in terms of helix angle,shape,and thickness.The simulation result shows that,for both inner and outer helical rotors,the energy harvesting efficiency is the highest when the blade helix angle is 45°.Triangular blades have better hydrodynamic performance than square and circular blades.The energy harvesting efficiency of 15 mm thick blades is higher than that of 75 mm thick blades.展开更多
Ocean waves can directly drive WECs （wave energy converters） to perform two types of motion--reciprocating motion and unidirectional rotary motion. In general, the efficiency of a reciprocating WEC is strongly wave-...Ocean waves can directly drive WECs （wave energy converters） to perform two types of motion--reciprocating motion and unidirectional rotary motion. In general, the efficiency of a reciprocating WEC is strongly wave-frequency dependent, whereas the efficiency of a rotary WEC can be somewhat wave-frequency independent. To date, a huge majority of WEC technologies under development in industry belong to the reciprocating class, and only a few WEC concepts fall in the unidirectional rotary class. In the present work, a wave-driven rotor for unidirectional rotary motion was proposed and characterized. A numerical tool has been developed for characterization of the rotor＇s unidirectional rotary tendency. The tool included a wave model and a drag force model. Simple circular tubes were used as blades in a basic rotor design. This basic design demonstrated strong potential for unidirectional rotary motion at a proper rotor submersion level and under various wave conditions. Two improved designs were yielded from the basic design. In one improved design, the original circular tubes were replaced with cylindrical shells of semicircular cross section as new blades. In another design, the semicircular shells were further modified to become one-way foldable. The two improvements significantly enhanced the rotors＇ unidirectional rotary tendency in waves, which has been verified by numerical simulation. Broad ranges of wave parameters and the submersion level have been numerically explored on the two improved rotor designs in conjunction with dimensional analysis.展开更多
This study explores the influence of rotor blade angle on stall inception in an axial fan by means of numerical simulations grounded in the Reynolds-Averaged Navier-Stokes(RANS)equations and the Realizable k-εturbule...This study explores the influence of rotor blade angle on stall inception in an axial fan by means of numerical simulations grounded in the Reynolds-Averaged Navier-Stokes(RANS)equations and the Realizable k-εturbulence model.By analyzing the temporal behavior of the outlet static pressure,along with the propagation velocity of stall inception,the research identifies distinct patterns in the development of stall.The results reveal that stall inception originates in the second rotor impeller.At a blade angle of 27°,the stall inception follows a modal wave pattern,while in all other cases,it assumes the form of spike-type stall.The flow field associated with spike stall inception demonstrates a relatively uniform gradient in the radial direction,whereas the modal wave stall case displays a distinctive“L”-shaped propagation feature.At blade angles of multiple stall inceptions are observed.-9°and-18°,These phenomena initiate at the blade’s leading edge,propagate along both axial and radial directions,and transition dynamically between single and multiple inception states.展开更多
The tip leakage flow has an important influence on the performance of transonic com- pressor. Blade tip winglet has been proved to be an effective method to control the tip leakage flow in compressor, while the physic...The tip leakage flow has an important influence on the performance of transonic com- pressor. Blade tip winglet has been proved to be an effective method to control the tip leakage flow in compressor, while the physical mechanisms of blade tip winglet have been poorly understood. A numerical study for a highly loaded transonic compressor rotor has been conducted to understand the effect of varying the location of blade tip wing]et on the performance of the rotor. Two kinds of tip winglet were designed and investigated. The effects of blade tip winglet on the compressor over- all performance, stability and tip flow structure were presented and discussed, It is found that the interaction of the tip winglet with the flow in the tip region is different when the winglet is located at suction-side or pressure-side of the blade tip. Results indicate that the suction-side winglet （SW） is ineffective to improve the performance of compressor rotor. In addition, a significant stall range extension equivalent to 33.74% with a very small penalty in efficiency can be obtained by the pressure-side winglet （PW）. An attempt has been made to explain the fundamental mechanisms of blade tip winglet in detail.展开更多
To avoid the damage caused by big wind and wave in cage culture, and to solve the problem of energy supply faced by automatic breeding equipment, a new type of floating breakwater, named as Savonius double buoy breakw...To avoid the damage caused by big wind and wave in cage culture, and to solve the problem of energy supply faced by automatic breeding equipment, a new type of floating breakwater, named as Savonius double buoy breakwater(SDBB), is proposed in the paper. The floating breakwater is composed of HDPE cylindrical double buoys and horizontal axis Savonius rotors, and has the functions of wave-absorbing and energy-capturing. Based on the linear wave theory and energy conservation law, the Fourier Transform was applied to separate the two-dimensional wave frequency domain, and the energy captured by the rotors and absorbed by the floating breakwater were calculated.Experiments were conducted in a two-dimensional wave-making flume, and the transmitted waves at different wave heights and periods, the tension of mooring lines, and the rotational torque exerted on the Savonius rotor were measured. A series of performance comparison tests were also performed on the new floating breakwater and the traditional double-floating breakwater. Results show that the new floating breakwater is better than the traditional one in terms of reducing wave transmittance, and the combination of the floating breakwater with Savonius rotors can provide for marine aquaculture equipments with green power supply to a certain degree of self-sufficiency.展开更多
High-speed rotor rotation under the low-density condition creates a special low-Reynolds compressible flow around the rotor blade airfoil where the compressibility effect on the laminar separated shear layer occurs. H...High-speed rotor rotation under the low-density condition creates a special low-Reynolds compressible flow around the rotor blade airfoil where the compressibility effect on the laminar separated shear layer occurs. However, the compressibility effect and shock wave generation associated with the increase in the Mach number (M) and the trend change due to their interference have not been clarified. The purpose is to clear the compressibility effect and its impact of shock wave generation on the flow field and aerodynamics. Therefore, we perform a two-dimensional unsteady calculation by Computational fluid dynamics (CFD) analysis using the CLF5605 airfoil used in the Mars helicopter Ingenuity, which succeeded in its first flight on Mars. The calculation conditions are set to the Reynolds number (Re) at 75% rotor span in hovering (Re = 15,400), and the Mach number was varied from incompressible (M = 0.2) to transonic (M = 1.2). The compressible fluid dynamics solver FaSTAR developed by the Japan aerospace exploration agency (JAXA) is used, and calculations are performed under multiple conditions in which the Mach number and angle of attack (α) are swept. The results show that a flow field is similar to that in the Earth’s atmosphere above M = 1.0, such as bow shock at the leading edge, whereas multiple λ-type shock waves are observed over the separated shear layer above α = 3° at M = 0.80. However, no significant difference is found in the C<sub>p</sub> distribution around the airfoil between M = 0.6 and M = 0.8. From the results, it is found that multiple λ-type shock waves have no significant effect on the airfoil surface pressure distribution, the separated shear layer effect is dominant in the surface pressure change and aerodynamic characteristics.展开更多
针对抑制非线性转子系统振动难问题,提出基于超声驻波悬浮原理抑制该系统振动的方法。首先阐述超声驻波悬浮力的基本理论,根据Gor′Kov理论构造超声悬浮力的数学模型,并构建超声悬浮非线性转子系统动力学模型。其次研究谐振腔高度和声...针对抑制非线性转子系统振动难问题,提出基于超声驻波悬浮原理抑制该系统振动的方法。首先阐述超声驻波悬浮力的基本理论,根据Gor′Kov理论构造超声悬浮力的数学模型,并构建超声悬浮非线性转子系统动力学模型。其次研究谐振腔高度和声场强度对抑制系统振动的影响。基于超声悬浮非线性转子系统,引入正位置反馈(Positive Position Feedback,PPF)控制器对其振动加以抑制,提高系统的稳定性。数值仿真结果表明,基于超声驻波悬浮原理,选取适当的声场参数可有效抑制非线性转子系统的振动,PPF控制器与超声悬浮转子系统耦合可显著增强对系统的振动抑制效果和系统在高转速区的稳定性。展开更多
基金co-supported by the National Natural Science Foundation of China(No.51906007)the National Key Laboratory Foundation of China(No.6142702190204)。
文摘A wave rotor is suitable for compact and efficient pressure-exchange between gas flows.This work measured the circumferential pressure distribution of the rotor/stator interfaces and utilized a CFD method to simulate the unsteady pressure waves.The experimental and CFD results showed some slopes in the circumferential pressure distributions,and the slopes indicated the traces of specific unsteady pressure waves.Such traces varied regularly if the rotational speed varied within a range from-11%to+11%off the baseline value,but they were seriously disturbed if the rotational speed varied by-45%from the baseline value.It verified that a pressure wave in a wave rotor tended to keep its pressure ratio and propagation velocity unchanged if the rotational speed varied by a small extent,and that the pressure wave could not keep its propagation patterns if the rotational speed varied by a large extent.Because of the pressure wave behaviors,the wave rotor demonstrated specific regulations of the rotational speed effects on its operational states.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51279190 and 51311140259)the Shandong Province Natural Science Foundation for Distinguished Young Scholars(Grant No.JQ201314)
文摘Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column（OWC） wave energy converters, which can rotate in the same direction under the bi-directional air flows. A numerical model established in Fluent is validated by the corresponding experimental results. The flow fields, pressure distribution and dimensionless evaluating coefficients can be calculated and analyzed. Effects of the rotor solidity varying with the change of blade number are investigated and the suitable solidity value is recommended for different flow coefficients.
文摘This paper establishes a simplified test system for internal combustion wave rotor with a single channel and designs different intensifying combustion obstacles and arrangements. Moreover, this paper analyzes the intensifying effect of obstacles on combustion process of the internal combustion wave rotor from the stable operation range, pressure gain and flame progression process perspective. The results show that the range of inlet velocity under stable operation of the internal combustion wave rotor narrows after the addition of obstacles, and the corresponding velocity values substantially reduce while the flame propagation speed can be improved by 2 - 4 times. At the rotation rate of 1500 rpm, the pressure gain increases significantly during the combustion process. These results provide technical supports for further research and application of the internal combustion wave rotor.
基金Supported by the National Key Research and Development Program of China(2019YFB1504402).
文摘This paper presents a new type of double-helical rotor wave energy converter(WEC),which consists of two isolated sets of helical rotor structures(inner and outer).This device can generate electricity by using the rising and falling energy of a wave.The rotors are simulated and optimized by Fluent.Each rotor’s blades are simulated and analyzed,which are separately changed in terms of helix angle,shape,and thickness.The simulation result shows that,for both inner and outer helical rotors,the energy harvesting efficiency is the highest when the blade helix angle is 45°.Triangular blades have better hydrodynamic performance than square and circular blades.The energy harvesting efficiency of 15 mm thick blades is higher than that of 75 mm thick blades.
文摘Ocean waves can directly drive WECs （wave energy converters） to perform two types of motion--reciprocating motion and unidirectional rotary motion. In general, the efficiency of a reciprocating WEC is strongly wave-frequency dependent, whereas the efficiency of a rotary WEC can be somewhat wave-frequency independent. To date, a huge majority of WEC technologies under development in industry belong to the reciprocating class, and only a few WEC concepts fall in the unidirectional rotary class. In the present work, a wave-driven rotor for unidirectional rotary motion was proposed and characterized. A numerical tool has been developed for characterization of the rotor＇s unidirectional rotary tendency. The tool included a wave model and a drag force model. Simple circular tubes were used as blades in a basic rotor design. This basic design demonstrated strong potential for unidirectional rotary motion at a proper rotor submersion level and under various wave conditions. Two improved designs were yielded from the basic design. In one improved design, the original circular tubes were replaced with cylindrical shells of semicircular cross section as new blades. In another design, the semicircular shells were further modified to become one-way foldable. The two improvements significantly enhanced the rotors＇ unidirectional rotary tendency in waves, which has been verified by numerical simulation. Broad ranges of wave parameters and the submersion level have been numerically explored on the two improved rotor designs in conjunction with dimensional analysis.
基金the Natural Science Foundation of Hebei Province,China(Grant No.E2022502052)Fundamental Research Funds for the Central Universities,China(Grant No.2022MS081)Fundamental Research Funds for the Central Universities,China(Grant No.2023MS121).
文摘This study explores the influence of rotor blade angle on stall inception in an axial fan by means of numerical simulations grounded in the Reynolds-Averaged Navier-Stokes(RANS)equations and the Realizable k-εturbulence model.By analyzing the temporal behavior of the outlet static pressure,along with the propagation velocity of stall inception,the research identifies distinct patterns in the development of stall.The results reveal that stall inception originates in the second rotor impeller.At a blade angle of 27°,the stall inception follows a modal wave pattern,while in all other cases,it assumes the form of spike-type stall.The flow field associated with spike stall inception demonstrates a relatively uniform gradient in the radial direction,whereas the modal wave stall case displays a distinctive“L”-shaped propagation feature.At blade angles of multiple stall inceptions are observed.-9°and-18°,These phenomena initiate at the blade’s leading edge,propagate along both axial and radial directions,and transition dynamically between single and multiple inception states.
基金co-supported by the National Natural Science Foundation of China(Nos.51436002,51406021)the Scientific Research Fund of Education Department of Liaoning Province(No.L2014197)+1 种基金the Program for Liaoning Innovative Research Team in University(No.LT2015004)the Fundamental Research Funds for the Central Universities(Nos.3132016014,3132014319)
文摘The tip leakage flow has an important influence on the performance of transonic com- pressor. Blade tip winglet has been proved to be an effective method to control the tip leakage flow in compressor, while the physical mechanisms of blade tip winglet have been poorly understood. A numerical study for a highly loaded transonic compressor rotor has been conducted to understand the effect of varying the location of blade tip wing]et on the performance of the rotor. Two kinds of tip winglet were designed and investigated. The effects of blade tip winglet on the compressor over- all performance, stability and tip flow structure were presented and discussed, It is found that the interaction of the tip winglet with the flow in the tip region is different when the winglet is located at suction-side or pressure-side of the blade tip. Results indicate that the suction-side winglet （SW） is ineffective to improve the performance of compressor rotor. In addition, a significant stall range extension equivalent to 33.74% with a very small penalty in efficiency can be obtained by the pressure-side winglet （PW）. An attempt has been made to explain the fundamental mechanisms of blade tip winglet in detail.
基金financially supported by the National Natural Science Foundation of China (Grant no. 51605431)Major Science and Technology Projects of Ningbo (Grant no. 2015C110015 and 2017C110005)。
文摘To avoid the damage caused by big wind and wave in cage culture, and to solve the problem of energy supply faced by automatic breeding equipment, a new type of floating breakwater, named as Savonius double buoy breakwater(SDBB), is proposed in the paper. The floating breakwater is composed of HDPE cylindrical double buoys and horizontal axis Savonius rotors, and has the functions of wave-absorbing and energy-capturing. Based on the linear wave theory and energy conservation law, the Fourier Transform was applied to separate the two-dimensional wave frequency domain, and the energy captured by the rotors and absorbed by the floating breakwater were calculated.Experiments were conducted in a two-dimensional wave-making flume, and the transmitted waves at different wave heights and periods, the tension of mooring lines, and the rotational torque exerted on the Savonius rotor were measured. A series of performance comparison tests were also performed on the new floating breakwater and the traditional double-floating breakwater. Results show that the new floating breakwater is better than the traditional one in terms of reducing wave transmittance, and the combination of the floating breakwater with Savonius rotors can provide for marine aquaculture equipments with green power supply to a certain degree of self-sufficiency.
文摘High-speed rotor rotation under the low-density condition creates a special low-Reynolds compressible flow around the rotor blade airfoil where the compressibility effect on the laminar separated shear layer occurs. However, the compressibility effect and shock wave generation associated with the increase in the Mach number (M) and the trend change due to their interference have not been clarified. The purpose is to clear the compressibility effect and its impact of shock wave generation on the flow field and aerodynamics. Therefore, we perform a two-dimensional unsteady calculation by Computational fluid dynamics (CFD) analysis using the CLF5605 airfoil used in the Mars helicopter Ingenuity, which succeeded in its first flight on Mars. The calculation conditions are set to the Reynolds number (Re) at 75% rotor span in hovering (Re = 15,400), and the Mach number was varied from incompressible (M = 0.2) to transonic (M = 1.2). The compressible fluid dynamics solver FaSTAR developed by the Japan aerospace exploration agency (JAXA) is used, and calculations are performed under multiple conditions in which the Mach number and angle of attack (α) are swept. The results show that a flow field is similar to that in the Earth’s atmosphere above M = 1.0, such as bow shock at the leading edge, whereas multiple λ-type shock waves are observed over the separated shear layer above α = 3° at M = 0.80. However, no significant difference is found in the C<sub>p</sub> distribution around the airfoil between M = 0.6 and M = 0.8. From the results, it is found that multiple λ-type shock waves have no significant effect on the airfoil surface pressure distribution, the separated shear layer effect is dominant in the surface pressure change and aerodynamic characteristics.
文摘针对抑制非线性转子系统振动难问题,提出基于超声驻波悬浮原理抑制该系统振动的方法。首先阐述超声驻波悬浮力的基本理论,根据Gor′Kov理论构造超声悬浮力的数学模型,并构建超声悬浮非线性转子系统动力学模型。其次研究谐振腔高度和声场强度对抑制系统振动的影响。基于超声悬浮非线性转子系统,引入正位置反馈(Positive Position Feedback,PPF)控制器对其振动加以抑制,提高系统的稳定性。数值仿真结果表明,基于超声驻波悬浮原理,选取适当的声场参数可有效抑制非线性转子系统的振动,PPF控制器与超声悬浮转子系统耦合可显著增强对系统的振动抑制效果和系统在高转速区的稳定性。
