Starting transient simulation of a vacuum ejector-diffuser system under Chevron effects

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.The vacuum ejector-diffuser system has been widely used in many applications such as refrigeration systems, high altitude test facilities and fluid transportation devices. In the present study, the starting transient flows of supersonic vacuum ejector-diffuser system, and its performance characteristics were simulated and analyzed by numerical methods. Newly designed chevron lobes were installed at the inlet of the primary stream of the vacuum ejector-diffuser system for the purpose of the performance improvement. A CFD method based on transient scheme has been applied to simulate the equilibrium flows and flow dynamics behavior of the secondary chamber. Primary numerical analysis results show that the chevrons get a positive effect on the vacuum ejector performance: less starting time and secondary chamber equilibrium pressure are found in chevron transient flow, compared with the convergent nozzle. The flow characteristics inside the ejector system are discussed using pressure history, vortices behavior, transient flow pattern and Reynolds stress distributions.dc201

Numerical analysis of mixing guide vane effects on performance of the supersonic ejector-diffuser system

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.Supersonic ejector-diffuser system makes use of primary stream with high speed and high pressure to propel the secondary stream through pure shear action. It has many advantages over other fluid machinery such as no moving parts and no direct mechanical energy input. That's why ejector-diffuser system has been used in many engineering industrial applications such as air propulsion and ejector refrigeration. The ejector-diffuser system also can be considered as the most important device of the solar seawater desalination. Generally speaking, the flow field in the ejector-diffuser system is very difficult to be predicted due to the complicated turbulent mixing, compressibility effects and even flow unsteadiness. Many works have been done in the past years to achieve a higher efficiency and improve the performance of the ejector system, but not yet satisfactory, compared with that of other fluid machinery. Considering the complexity and difficulty on the researching, how to enhance the performance of ejector-diffuser system effectively became a significant task. In the present study, several mixing guide vanes were installed at the inlet of the secondary stream of the ejector-diffuser system for the purpose of the performance improvement. The present study aim is to lessen the negative effects on the secondary stream and get a higher level in both pressure recovery and entrainment ratio. A CFD method based on Fluent has been applied to simulate the supersonic flows and shock waves inside the ejector. Numerical analysis results of the mixing guide vane effects were validated with experimental data in the previous work. The comparison of ejector performance with and without the mixing guide vane was obtained and optimal position of mixing guide vane is discussed to increase the performance. The operation characteristics of the ejector system with different numbers of inlet guide vanes are analyzed in detail. The ejector-diffuser system performance is discussed in terms of the entrainment ratio, ejector efficiency, pressure recovery as well as total pressure loss.dc201

Optimization study on the contoured shock tube for needle-free drug delivery

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.An exciting alternative of the conventional drug delivery systems has been proposed in recent times named as transdermal powdered drug delivery. The idea is to deliver drug (in powdered from) into the human skin without using any external needle. Among different proposed systems the contoured shock tube (CST) system stands out. The performance of CST device is widely analyzed by different researchers. However, there is still room for improvement of it’s performance. This study aims at improving the performance of CST device by adjusting it’s geometry as well as operating condition. A significant improvement in the performance is reported after proper adjustment of different features of the device.dc201

A High-Dimensional Video Sequence Completion Method with Traffic Data Completion Generative Adversarial Networks

The lack of traffic data is a bottleneck restricting the development of Intelligent Transportation Systems (ITS). Most existing traffic data completion methods aim at low-dimensional data, which cannot cope with high-dimensional video data. Therefore, this paper proposes a traffic data complete generation adversarial network (TDC-GAN) model to solve the problem of missing frames in traffic video. Based on the Feature Pyramid Network (FPN), we designed a multiscale semantic information extraction model, which employs a convolution mechanism to mine informative features from high-dimensional data. Moreover, by constructing a discriminator model with global and local branch networks, the temporal and spatial information are captured to ensure the time-space consistency of consecutive frames. Finally, the TDC-GAN model performs single-frame and multiframe completion experiments on the Caltech pedestrian dataset and KITTI dataset. The results show that the proposed model can complete the corresponding missing frames in the video sequences and achieve a good performance in quantitative comparative analysis