Currently, many studies have been made for years on dimensions of pneumatic nozzle, which influence the flow characteristic of blowing system. For the purpose of outputting the same blowing force, the supply pressure ...Currently, many studies have been made for years on dimensions of pneumatic nozzle, which influence the flow characteristic of blowing system. For the purpose of outputting the same blowing force, the supply pressure could be reduced by decreasing the ratio of length to diameter of nozzle. The friction between high speed air and pipe wall would be reduced if the nozzle is designed to be converging shape comparing with straight shape. But the volume flow and pressure, discussed in these studies, do not describe energy loss of the blowing system directly. Pneumatic power is an innovative principle to estimate pneumatic system’s energy consumption directly. Based on the above principle, a pulse blowing method is put forward for saving energy. A flow experiment is carried out, in which the high speed air flows from the pulse blowing system and continuous blowing system respectively to a plate with grease on top. Supply pressure and the volume of air used for removing the grease are measured to calculate energy consumption. From the experiment result, the pulse blowing system performs to conserve energy comparing with the continuous blowing system. The frequency and duty ratio of pulse flow influence the blowing characteristic. The pulse blowing system performs to be the most efficient at the specified frequency and duty ratio. Then a pneumatic self-oscillated method based on air operated valve is put forward to generate pulse flow. A simulation is made about dynamic modeling the air operated valve and calculating the motion of the valve core and output pressure. The simulation result verifies the system to be able to generate pulse flow, and predicts the key parameters of the frequency and duty ratio measured by experiment well. Finally, on the basis of simplifying and solution of the pulse blowing system’s mathematic model, the relationship between system’s frequency duty ratio and the dimensions of components is simply described with four algebraic equations. The system could be designed with specified frequency and duty ratio according to the four equations. This study provides theoretical basis for designing energy-saving air blowing system.展开更多
Oscillatory behaviors can be ubiquitously observed in various systems. Biological rhythms are significant in governing living activities of all units. The emergence of biological rhythms is the consequence of large nu...Oscillatory behaviors can be ubiquitously observed in various systems. Biological rhythms are significant in governing living activities of all units. The emergence of biological rhythms is the consequence of large numbers of units. In this paper we discuss several important examples of sustained oscillations in biological media, where the unit composed in the system does not possess the oscillation behavior. The dominant phase-advanced driving method is applied to study the skeletons and oscillatory organizing motifs in excitable networks and gene regulatory networks.展开更多
Numerical simulations are used to investigate the self-sustained oscillating flows past an open cavity. The two-dimensional incompressible Navier-Stokes equations are solved directly by using the finite difference met...Numerical simulations are used to investigate the self-sustained oscillating flows past an open cavity. The two-dimensional incompressible Navier-Stokes equations are solved directly by using the finite difference method for cavities with an upstream laminar boundary layer. A series of simulations are performed for a variety of cavity length-to-depth ratio. The results show the switching among some flow modes including non-oscillation mode, shear layer mode and wake mode. The variation of the Strouhal number is in favorable agreement with available experimental data. The results of flow fields in the cavity reveal the relationship between the cavity shear layer oscillation modes and recirculating vortices in the cavity.展开更多
2010年10月海南发生了自1951年以来最严重的持续性暴雨灾害。对该持续性暴雨事件的天气特征以及大气准双周振荡对其的影响进行了诊断分析。结果表明,2010年10月海南发生的两次暴雨过程都与热带辐合带的低压系统有关。10月上旬海南暴雨...2010年10月海南发生了自1951年以来最严重的持续性暴雨灾害。对该持续性暴雨事件的天气特征以及大气准双周振荡对其的影响进行了诊断分析。结果表明,2010年10月海南发生的两次暴雨过程都与热带辐合带的低压系统有关。10月上旬海南暴雨过程的水汽主要来源于南海北部和菲律宾东面的热带西太平洋,而10月中的暴雨过程的水汽除了来源于台湾-菲律宾东面的热带西太平洋外,还有源于印度洋经中南半岛南部再转向北上的水汽输送。海南持续性暴雨天气过程与热带大气的准双周振荡有关。加里曼丹岛和菲律宾南部附近地区的大气准双周低频振荡的产生及其西北向传播对海南岛的两次持续性暴雨过程有重要的影响。2010年在赤道中东太平洋发生的La Ni a现象使得9、10月热带东印度洋-西太平洋的对流活动异常活跃,有利于大气准双周低频振荡的产生。展开更多
文摘Currently, many studies have been made for years on dimensions of pneumatic nozzle, which influence the flow characteristic of blowing system. For the purpose of outputting the same blowing force, the supply pressure could be reduced by decreasing the ratio of length to diameter of nozzle. The friction between high speed air and pipe wall would be reduced if the nozzle is designed to be converging shape comparing with straight shape. But the volume flow and pressure, discussed in these studies, do not describe energy loss of the blowing system directly. Pneumatic power is an innovative principle to estimate pneumatic system’s energy consumption directly. Based on the above principle, a pulse blowing method is put forward for saving energy. A flow experiment is carried out, in which the high speed air flows from the pulse blowing system and continuous blowing system respectively to a plate with grease on top. Supply pressure and the volume of air used for removing the grease are measured to calculate energy consumption. From the experiment result, the pulse blowing system performs to conserve energy comparing with the continuous blowing system. The frequency and duty ratio of pulse flow influence the blowing characteristic. The pulse blowing system performs to be the most efficient at the specified frequency and duty ratio. Then a pneumatic self-oscillated method based on air operated valve is put forward to generate pulse flow. A simulation is made about dynamic modeling the air operated valve and calculating the motion of the valve core and output pressure. The simulation result verifies the system to be able to generate pulse flow, and predicts the key parameters of the frequency and duty ratio measured by experiment well. Finally, on the basis of simplifying and solution of the pulse blowing system’s mathematic model, the relationship between system’s frequency duty ratio and the dimensions of components is simply described with four algebraic equations. The system could be designed with specified frequency and duty ratio according to the four equations. This study provides theoretical basis for designing energy-saving air blowing system.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11475022 and 11675001)the Scientific Research Funds of Huaqiao University,China(Grant No.15BS401)
文摘Oscillatory behaviors can be ubiquitously observed in various systems. Biological rhythms are significant in governing living activities of all units. The emergence of biological rhythms is the consequence of large numbers of units. In this paper we discuss several important examples of sustained oscillations in biological media, where the unit composed in the system does not possess the oscillation behavior. The dominant phase-advanced driving method is applied to study the skeletons and oscillatory organizing motifs in excitable networks and gene regulatory networks.
文摘Numerical simulations are used to investigate the self-sustained oscillating flows past an open cavity. The two-dimensional incompressible Navier-Stokes equations are solved directly by using the finite difference method for cavities with an upstream laminar boundary layer. A series of simulations are performed for a variety of cavity length-to-depth ratio. The results show the switching among some flow modes including non-oscillation mode, shear layer mode and wake mode. The variation of the Strouhal number is in favorable agreement with available experimental data. The results of flow fields in the cavity reveal the relationship between the cavity shear layer oscillation modes and recirculating vortices in the cavity.
文摘2010年10月海南发生了自1951年以来最严重的持续性暴雨灾害。对该持续性暴雨事件的天气特征以及大气准双周振荡对其的影响进行了诊断分析。结果表明,2010年10月海南发生的两次暴雨过程都与热带辐合带的低压系统有关。10月上旬海南暴雨过程的水汽主要来源于南海北部和菲律宾东面的热带西太平洋,而10月中的暴雨过程的水汽除了来源于台湾-菲律宾东面的热带西太平洋外,还有源于印度洋经中南半岛南部再转向北上的水汽输送。海南持续性暴雨天气过程与热带大气的准双周振荡有关。加里曼丹岛和菲律宾南部附近地区的大气准双周低频振荡的产生及其西北向传播对海南岛的两次持续性暴雨过程有重要的影响。2010年在赤道中东太平洋发生的La Ni a现象使得9、10月热带东印度洋-西太平洋的对流活动异常活跃,有利于大气准双周低频振荡的产生。
