Combining high-speed schlieren technology and infrared imaging technology,related research has been carried out on the influence of parameters such as actuation voltage,repetition frequency,and electrode size of an ac...Combining high-speed schlieren technology and infrared imaging technology,related research has been carried out on the influence of parameters such as actuation voltage,repetition frequency,and electrode size of an actuator on the discharge characteristics,induced flow field characteristics,and thermal characteristics of nanosecond pulsed dielectric barrier discharge.The results show that increasing the value of the actuation voltage can significantly increase the actuation intensity,and the plasma discharge area is significantly extended.Increasing the repetition frequency can increase the number of discharges per unit time.Both will cause more energy input and induce more changes in the flow field.The effect of temperature rise is more significant.The width of the covered electrode will affect the potential distribution during the discharge process,which in turn will affect the extension process of the plasma discharge filament.Under the same actuation intensity,the wider the covered electrode,the larger range the induced flow field and temperature rise is.Preliminary experimental analyses of high-frequency actuation characteristics,temperature field characteristics,flow field characteristics and actuation parameter settings provide support for the parameter selection and partial mechanism analysis of plasma anti-icing.展开更多
A major issue of plasma synthetic jet actuator(PSJA)is the severe performance deterioration at high working frequency.In this study,experiments and numerical simulation are combined together to investigate the influen...A major issue of plasma synthetic jet actuator(PSJA)is the severe performance deterioration at high working frequency.In this study,experiments and numerical simulation are combined together to investigate the influence of thermal conductivity,throat length(Lth)and discharge duration(Td)on the high-frequency characteristics of PSJA.Results show that the variation of the actuator thermal conductivity and discharge duration will not alter the saturation frequency of the actuator,whereas decreasing the throat length results in an increase of the saturation frequency.For a short-duration capacitive discharge of 1.7μs,a clear shock wave is issued from the orifice,followed by a weak jet.As a comparison,when the discharge duration is increased up to 202.6μs,a strong jet column is formed and no obvious shock wave can be visualized.Based on numerical simulation results,it becomes clear that the long-duration pulse-DC discharge is able to heat the cavity gas to a much higher temperature(3141 K)than capacitive discharge,greatly improving the conversion efficiency of the arc discharge energy to the internal energy of the cavity gas.In addition,high-speed Schlieren imaging is deployed to study the performance degradation mechanism of PSJA at high working frequency.Monitor of the exit jet grayscale indicates that as long as the saturation frequency is exceeded,the actuator becomes unstable due to insufficient refresh time.The higher the discharge frequency,the more frequently the phenomenon of‘misfires’will occur,which explains well the decaying jet total pressure at above saturation frequency.展开更多
An array of 30 plasma synthetic jet actuators(PSJAs)is deployed using a modified multichannel discharge circuit to suppress the flow separation over a straight-wing model.The lift and drag of the wing model are measur...An array of 30 plasma synthetic jet actuators(PSJAs)is deployed using a modified multichannel discharge circuit to suppress the flow separation over a straight-wing model.The lift and drag of the wing model are measured by a force balance,and the velocity fields over the suction surface are captured by a particle imaging velocimetry system.Results show that the flow separation of the straight wing originates from the middle of the model and expands towards the wingtips as the angle of attack increases.The flow separation can be suppressed effectively by the PSJAs array.The best flow control effect is achieved at a dimensionless discharge frequency of F^+=1,with the peak lift coefficient increased by 10.5%and the stall angle postponed by 2°.To further optimize the power consumption of the PSJAs,the influence of the density of PSJAs on the flow control effect is investigated.A threshold of the density exits(with the spanwise spacing of PSJAs being 0.2 times of the chord length in the current research),below which the flow control effect starts to deteriorate remarkably.In addition,for comparison purposes,a dielectric barrier discharge(DBD)plasma actuator is installed at the same location of the PSJAs.At the same power consumption,4.9%increase of the peak lift coefficient is achieved by DBD,while that achieved by PSJAs reaches 5.6%.展开更多
Since flight accidents due to aircraft icing occur from time to time,this paper proposes an array of impact rod-type plasma synthetic jet de-icing methods for aircraft icing problems.The impact rod-type plasma synthet...Since flight accidents due to aircraft icing occur from time to time,this paper proposes an array of impact rod-type plasma synthetic jet de-icing methods for aircraft icing problems.The impact rod-type plasma synthetic jet actuator(PSJA)is based on the traditional PSJA with an additional impact rod structure for better de-icing in the flight environment.In this work,we first optimize the ice-breaking performance of a single-impact rod-type PSJA,and then conduct an array of impact rod-type plasma synthetic jet ice-breaking experiments to investigate the relationship between crack expansion and discharge energy,ice thickness and group spacing.The results show that the impact force and impulse of a single-impact rod-type PSJA are proportional to the discharge energy,and there exists a threshold energy Qmin for a single actuator to break the ice,which is proportional to the ice thickness.Only when the discharge energy reaches above Qmin can the ice layer produce cracks,and at the same time,the maximum radial crack length produced during the ice-breaking process is proportional to the discharge energy.When the ice is broken by an array of impact rod PSJAs,the discharge energy and group spacing together determine whether the crack can be extended to the middle region of the actuator.When the group spacing is certain,increasing the energy can increase the intersection of cracks in the middle region,and the ice-fragmentation degree is increased and the ice-breaking effect is better.At the same time,the energy estimation method of ice breaking by an array of impact rod-type PSJAs is proposed according to the law when a single actuator is breaking ice.展开更多
基金supported by the National Key R&D Program of China(No.2019YFA0405300)National Natural Science Foundation of China(Nos.51907205 and 12002363)。
文摘Combining high-speed schlieren technology and infrared imaging technology,related research has been carried out on the influence of parameters such as actuation voltage,repetition frequency,and electrode size of an actuator on the discharge characteristics,induced flow field characteristics,and thermal characteristics of nanosecond pulsed dielectric barrier discharge.The results show that increasing the value of the actuation voltage can significantly increase the actuation intensity,and the plasma discharge area is significantly extended.Increasing the repetition frequency can increase the number of discharges per unit time.Both will cause more energy input and induce more changes in the flow field.The effect of temperature rise is more significant.The width of the covered electrode will affect the potential distribution during the discharge process,which in turn will affect the extension process of the plasma discharge filament.Under the same actuation intensity,the wider the covered electrode,the larger range the induced flow field and temperature rise is.Preliminary experimental analyses of high-frequency actuation characteristics,temperature field characteristics,flow field characteristics and actuation parameter settings provide support for the parameter selection and partial mechanism analysis of plasma anti-icing.
基金supported by National Natural Science Foundation of China(No.12002384)the National Key Laboratory Foundation of China(No.614220210200112)the Foundation Strengthening Project(No.2019-JCJQ-JJ-077)。
文摘A major issue of plasma synthetic jet actuator(PSJA)is the severe performance deterioration at high working frequency.In this study,experiments and numerical simulation are combined together to investigate the influence of thermal conductivity,throat length(Lth)and discharge duration(Td)on the high-frequency characteristics of PSJA.Results show that the variation of the actuator thermal conductivity and discharge duration will not alter the saturation frequency of the actuator,whereas decreasing the throat length results in an increase of the saturation frequency.For a short-duration capacitive discharge of 1.7μs,a clear shock wave is issued from the orifice,followed by a weak jet.As a comparison,when the discharge duration is increased up to 202.6μs,a strong jet column is formed and no obvious shock wave can be visualized.Based on numerical simulation results,it becomes clear that the long-duration pulse-DC discharge is able to heat the cavity gas to a much higher temperature(3141 K)than capacitive discharge,greatly improving the conversion efficiency of the arc discharge energy to the internal energy of the cavity gas.In addition,high-speed Schlieren imaging is deployed to study the performance degradation mechanism of PSJA at high working frequency.Monitor of the exit jet grayscale indicates that as long as the saturation frequency is exceeded,the actuator becomes unstable due to insufficient refresh time.The higher the discharge frequency,the more frequently the phenomenon of‘misfires’will occur,which explains well the decaying jet total pressure at above saturation frequency.
基金National Natural Science Foundation of China(Nos.12002384 and 11802341)the National Key Laboratory Foundation of China(No.614220210200112)the Academician Workstation Foundation of the Green Aerotechnics Research Institute of Chongqing Jiaotong University(No.GATRI2020C06003)。
文摘An array of 30 plasma synthetic jet actuators(PSJAs)is deployed using a modified multichannel discharge circuit to suppress the flow separation over a straight-wing model.The lift and drag of the wing model are measured by a force balance,and the velocity fields over the suction surface are captured by a particle imaging velocimetry system.Results show that the flow separation of the straight wing originates from the middle of the model and expands towards the wingtips as the angle of attack increases.The flow separation can be suppressed effectively by the PSJAs array.The best flow control effect is achieved at a dimensionless discharge frequency of F^+=1,with the peak lift coefficient increased by 10.5%and the stall angle postponed by 2°.To further optimize the power consumption of the PSJAs,the influence of the density of PSJAs on the flow control effect is investigated.A threshold of the density exits(with the spanwise spacing of PSJAs being 0.2 times of the chord length in the current research),below which the flow control effect starts to deteriorate remarkably.In addition,for comparison purposes,a dielectric barrier discharge(DBD)plasma actuator is installed at the same location of the PSJAs.At the same power consumption,4.9%increase of the peak lift coefficient is achieved by DBD,while that achieved by PSJAs reaches 5.6%.
基金financially supported by National Natural Science Foundation of China(No.12002384)National Key Laboratory Foundation of China(No.614220220200107)+1 种基金National Science and Technology Major Project of China(No.J2019-II-0014-0035)Academician Workstation F0undation of the Green Aerotechnics Research Institute of Chongqing Jiaotong University(No.GATRI2020C06003)。
文摘Since flight accidents due to aircraft icing occur from time to time,this paper proposes an array of impact rod-type plasma synthetic jet de-icing methods for aircraft icing problems.The impact rod-type plasma synthetic jet actuator(PSJA)is based on the traditional PSJA with an additional impact rod structure for better de-icing in the flight environment.In this work,we first optimize the ice-breaking performance of a single-impact rod-type PSJA,and then conduct an array of impact rod-type plasma synthetic jet ice-breaking experiments to investigate the relationship between crack expansion and discharge energy,ice thickness and group spacing.The results show that the impact force and impulse of a single-impact rod-type PSJA are proportional to the discharge energy,and there exists a threshold energy Qmin for a single actuator to break the ice,which is proportional to the ice thickness.Only when the discharge energy reaches above Qmin can the ice layer produce cracks,and at the same time,the maximum radial crack length produced during the ice-breaking process is proportional to the discharge energy.When the ice is broken by an array of impact rod PSJAs,the discharge energy and group spacing together determine whether the crack can be extended to the middle region of the actuator.When the group spacing is certain,increasing the energy can increase the intersection of cracks in the middle region,and the ice-fragmentation degree is increased and the ice-breaking effect is better.At the same time,the energy estimation method of ice breaking by an array of impact rod-type PSJAs is proposed according to the law when a single actuator is breaking ice.
