The Research of Double Diaphragm Shock Tube in Dynamic Pressure Calibration
|School||University of North|
|Course||Measuring Technology and Instruments|
|Keywords||dynamic calibration pressure sensor shock tube double diaphragm|
Pressure sensor has been used from daily life to scientific research, techniquedevelopment and national security&military for a long time. Dynamic calibration technologyfor pressure sensor is always an important subject in academic field. In order to ensure thereliability of the results of shock wave overpressure test, dynamic calibration for pressuresensor is needed before and after a crucial experiment. A step signal generated by shock tubehas enough bandwidth. So shock tube has been widely used for pressure sensor in dynamiccalibration. The running of twice broken membrane system is stable. The speed of the incidentshock wave in double membrane shock tube is also stable. The major work presented in thispaper is the application of double diaphragm shock tube in dynamic pressure calibration inboth theory and practice, which is showed below:(1) Two different wave figures generated by incident shock waves, reflected shock waves,incident rarefaction waves and reflected rarefaction waves in three pressure chamber ofdouble diaphragm shock tube are introduced.(2)Based on the shock wave propagation in double diaphragm shock tube and combinedthe knowledge of pneumatics, mathematical derivation of flow parameters during the processof shock wave flowing is provided. After getting Rankine-Hugoniot conditions for doublediaphragm shock tube, incident step pressures, reflected step pressures in both low andmedium pressure chambers are solved, along with initial high/medium/low pressure-relatedtheoretical formulas. All these work established the theoretical foundation for calibration test.(3) Due to the variety of parameters and complexity of computation, a software based onLabVIEW for computing double diaphragm shock tube parameters was developed. Thetime-saving software has a greatest advantage that it can quickly achieve positive and negative operation of post-test parameters and initial parameters.(4) According to experiment results of four different thickness diaphragm rupture, thesoftware further has the function of choosing diaphragms. In order to verify that the softwareis practical, the dynamic calibration experiments of single diaphragm&double diaphragmshock tube under same thickness and the dynamic calibration experiments of doublediaphragm shock tube under different thickness are conducted. The error of the Mach numberis increased with the increase of the thickness of diaphragm. Shock wave system of doublemembrane shock tube belongs to delay burst figure when the thickness of double diaphragmis0.5mm. Shock wave system of double membrane shock tube belongs to immediately burstwave figure when the thickness of double diaphragm is1.0mm and1.5mm.