A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation： ① The low frequency resonance...A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation： ① The low frequency resonances introduced into the system; ② Conflict between lower isolation frequency and stiffness high enough to limit quasi-static stroke;③ Inconsistent isolation level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance, nonlinearities compensation and motion flow rate compensation （MFRC） are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions： one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to tune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.展开更多
To improve the performance of the Stairmand cyclone, the effects of an expansion chamber on the flow field, the pressure drop and the separation efficiency were investigated numerically and experimentally. The experim...To improve the performance of the Stairmand cyclone, the effects of an expansion chamber on the flow field, the pressure drop and the separation efficiency were investigated numerically and experimentally. The experimental results showed that compared with the Stairmand cyclone, the cyclone with an upper expansion chamber worked better at low inlet velocity(less than 14 m/s in this study), while the cyclone with a lower expansion chamber achieved higher efficiency at a relatively high inlet velocity(14-20 m/s). The presence of an expansion chamber can generally result in a slight decrease in the cyclone pressure drop. The simulated results, which were used to further analyze the reason behind the experimental phenomena, suggested that the expansion chamber had insignificant effects on the tangential velocity profiles in the cylindrical part of cyclones. While in the cone part, the expansion chamber and the dipleg, the tangential velocity slightly decreased. Nevertheless, the expansion chamber decreased the possibility of the vortex end to sweep the wall and then reduce the particle re-entrainment. Therefore, installing the expansion chamber at a proper position could improve the separation performance of Stairmand cyclones. Both the experimental and simulated results represent a potential improvement of the Stairmand cyclone performance.展开更多
In the previous researches, it is known that the swirl flow in circular pipe causes the temperature separation. Recently, it is shown that the temperature separation occurs in a vortex chamber when compressed air are ...In the previous researches, it is known that the swirl flow in circular pipe causes the temperature separation. Recently, it is shown that the temperature separation occurs in a vortex chamber when compressed air are pumped into this device from the periphery. Especially, in a cavity installed in the periphery of the chamber, the highest temperature was observed. Therefore, it is expected that this device can be used as a heat source in the engineering field. In recent researches, the mechanism of temperature separation in vortex chamber has been investigated by some researchers. However, there are few researches for the effect of diameter and volume of vortex chamber, height of central rod and position of cavity on the temperature separation. Further, no detailed physical explanation has been made for the temperature separation phenomena in the vortex chamber. In the present study, the effects of chamber configuration and position of the cavity on temperature separation in the vortex chamber were investigated experimentally.展开更多
In order to improve the efficiency of reducing fine dust emissions from diffuse sources,the commonly used water mist can be electrostatically charged.Thus,the attraction between particles and droplets increases due to...In order to improve the efficiency of reducing fine dust emissions from diffuse sources,the commonly used water mist can be electrostatically charged.Thus,the attraction between particles and droplets increases due to electrostatic field forces.In the experimental investigations carried out,an electrostatic two-fluid nozzle was used to generate a charged spray mist according to the principle of charging by induction.In a chamber,dispersed dust was precipitated with the spray mist,while detecting the laser light attenuation.By means of comparative measurements it could be shown that faster sedimentation and separation takes place through electrostatic attraction.Parameter variations regarding the use of compressed air and water were investigated and the sedimentation time of the particle-droplet mixture in the chamber was shown.A size distribution was then calculated from the laser light attenuation,which shows that the proportion of small particles decreases with spray application.Furthermore,the influence of the polarity of droplets and solid particles on the reduction measure was determined.展开更多
基金This project is supported by Commission of Science Technology and Industry for National Defense, China.
文摘A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation： ① The low frequency resonances introduced into the system; ② Conflict between lower isolation frequency and stiffness high enough to limit quasi-static stroke;③ Inconsistent isolation level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance, nonlinearities compensation and motion flow rate compensation （MFRC） are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions： one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to tune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.
基金the financial assistance from the National Natural Science Foundation (Grant No.21276274)the National Key Project of Basic Research of the Ministry for Science and Technology of China (Grant No. 2014CB744304)
文摘To improve the performance of the Stairmand cyclone, the effects of an expansion chamber on the flow field, the pressure drop and the separation efficiency were investigated numerically and experimentally. The experimental results showed that compared with the Stairmand cyclone, the cyclone with an upper expansion chamber worked better at low inlet velocity(less than 14 m/s in this study), while the cyclone with a lower expansion chamber achieved higher efficiency at a relatively high inlet velocity(14-20 m/s). The presence of an expansion chamber can generally result in a slight decrease in the cyclone pressure drop. The simulated results, which were used to further analyze the reason behind the experimental phenomena, suggested that the expansion chamber had insignificant effects on the tangential velocity profiles in the cylindrical part of cyclones. While in the cone part, the expansion chamber and the dipleg, the tangential velocity slightly decreased. Nevertheless, the expansion chamber decreased the possibility of the vortex end to sweep the wall and then reduce the particle re-entrainment. Therefore, installing the expansion chamber at a proper position could improve the separation performance of Stairmand cyclones. Both the experimental and simulated results represent a potential improvement of the Stairmand cyclone performance.
文摘In the previous researches, it is known that the swirl flow in circular pipe causes the temperature separation. Recently, it is shown that the temperature separation occurs in a vortex chamber when compressed air are pumped into this device from the periphery. Especially, in a cavity installed in the periphery of the chamber, the highest temperature was observed. Therefore, it is expected that this device can be used as a heat source in the engineering field. In recent researches, the mechanism of temperature separation in vortex chamber has been investigated by some researchers. However, there are few researches for the effect of diameter and volume of vortex chamber, height of central rod and position of cavity on the temperature separation. Further, no detailed physical explanation has been made for the temperature separation phenomena in the vortex chamber. In the present study, the effects of chamber configuration and position of the cavity on temperature separation in the vortex chamber were investigated experimentally.
文摘In order to improve the efficiency of reducing fine dust emissions from diffuse sources,the commonly used water mist can be electrostatically charged.Thus,the attraction between particles and droplets increases due to electrostatic field forces.In the experimental investigations carried out,an electrostatic two-fluid nozzle was used to generate a charged spray mist according to the principle of charging by induction.In a chamber,dispersed dust was precipitated with the spray mist,while detecting the laser light attenuation.By means of comparative measurements it could be shown that faster sedimentation and separation takes place through electrostatic attraction.Parameter variations regarding the use of compressed air and water were investigated and the sedimentation time of the particle-droplet mixture in the chamber was shown.A size distribution was then calculated from the laser light attenuation,which shows that the proportion of small particles decreases with spray application.Furthermore,the influence of the polarity of droplets and solid particles on the reduction measure was determined.
