Pneumatic technology takes compressed gas as the power source, but the leakage of gas in the pipeline due to poor sealing or pipeline rupture affects the accuracy of pneumatic control, the flow of gas transmission, and even the emission of harmful gas. The air tightness of differential pressure method has broad significance in the study of tight leakage because of its simple operation, short detection time, and high precision. Bubbling method, acoustic emission detection method, and direct pressure detection method have the characteristics of difficult operation, environmental sensitivity and low detection accuracy. They are not suitable for effective and high-precision detection of leakage in harsh environment. The air tightness detection method of differential pressure method has the advantages of simple operation, short detection time, and high accuracy. It has extensive significance in the research of air tightness leakage. At present, the focus of differential pressure method is to keep the same charging state of the master tank and the tested tank. However, when the shape of the tested tank is irregular or difficult to copy, the influence of different master tank on differential pressure method leakage detection needs to be considered. In this study, a gas leakage flow calculation model is established. The influence of the inherent parameters of the master tank on the calculation of the pressure difference, temperature difference, and leakage between the two cavities is analyzed in the simulation. Finally, the master tank is set as a quasi-isothermal cavity, and the tested tank is set as 3 L and 5 L air tanks for leakage test. The maximum error of experiment of 3 L tank reaches 39 mL/min at the later stage of measurement, with a detection deviation of 14.4%. The maximum error of experiment of 5 L tank is 412.4 mL/min, with a deviation rate of 28.3%. This method can detect leakage with high precision in harsh environment.
Background. Spinal cord injury (SCI) is a common severe trauma in clinic, hundreds of thousands of people suffer from which every year in the world. In terms of injury location, cervical spinal cord injury (CSCI) has the greatest impact. After cervical spinal cord injury, the lack of innervated muscles is not enough to provide ventilation and other activities to complete the respiratory function. In addition to the decline of respiratory capacity, respiratory complications also have a serious impact on the life of patients. The most commonly used assisted breathing and cough equipment is the ventilator, but in recent years, the functional electrical stimulation method is being used gradually and widely. Methods. About hundred related academic papers are cited for data analysis. They all have the following characteristics: (1) basic conditions of patients were reported, (2) patients had received nerve or muscle stimulation and the basic parameters, and (3) the results were evaluated based on some indicators. Results. The papers mentioned above are classified as four kinds of stimulation methods: muscle electric/magnetic stimulation, spinal dural electric stimulation, intraspinal microstimulation, and infrared light stimulation. This paper describes the stimulation principle and application experiment. Finally, this paper will compare the indexes and effects of typical stimulation methods, as well as the two auxiliary methods: training and operation. Conclusions. Although there is limited evidence for the treatment of respiratory failure by nerve or muscle stimulation after cervical spinal cord injury, the two techniques seem to be safe and effective. At the same time, light stimulation is gradually applied to clinical medicine with its strong advantages and becomes the development trend of nerve stimulation in the future.
Abstract. The Interstage Turbine Burner (ITB) engine provide significantly higher specific thrust with no or only small increases in thrust specific fuel consumption substitute for conventional gas engine with after-burners. Continue combustion between a high pressure turbine stage and low pressure turbine stage is organized. Ultra-Compact Combustor (UCC), which is one of mainstream design concepts of ITB, has a broad application prospect in the field of aviation with the advantages of compact structure and high combustion efficiency. In order to improve the application of Ultra-Compact Turbine interstage combustor in aero-engine, the numerical simulation was carried out by using CFD technique to research on the influence of the number of cavities in the cavity on the ITB. The results show that the increasing number of structures of cavities in the cavity will enhance the circumferential cavity of the fuel and air mixing and burning, promote the combustion mixture to the mainstream radial transport capacity and improve combustion efficiency and uniformity of exit temperature field.
Currently, the measurement methods for pneumatic system leakage include bubbling, ultrasonic, and pressure detection methods. These methods are sensitive to high-precision sensors, long detection times, and stable external environments. The traditional differential pressure method involves severe differential pressure fluctuations caused by environmental pressure fluctuations or electromagnetic noise interference of sensors, leading to inaccurate detection. In this paper, a differential pressure fitting method for an asymmetric differential pressure cylinder is proposed. It overcomes the limitation of the detection efficiency caused by the asynchronous temperature recovery of the two chambers in the asymmetric differential pressure method and uses the differential pressure substitution equation to replace the differential calculation of the differential pressure. The improved differential pressure method proposes an innovation based on the detection principle and calculation method. Additionally, the influence of the parameters in the differential pressure substitution equation on the leakage calculation results was simulated, and the specific physical significance of the parameters of the differential pressure substitution equation was explained. The experiments verified the fitting effect and proved the accuracy of this method. Compared with the traditional differential pressure method, the maximum leakage deviation of inhibition was 0.5 L/min. Therefore, this method can be used to detect leaks in air tanks.
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