Characterization of a newly developed diaphragmless shock tube for the primary dynamic calibration of pressure meters

Abstract

In conventional shock tubes with a diaphragm, many effects related to the burst of the diaphragm can influence shock formation, thus preventing an ideal pressure step change, as predicted by the shock tube measurement model being generated. This paper presents a newly developed diaphragmless shock tube with a quick-acting pneumatic valve, which demonstrates several advantages over conventional shock tubes with a diaphragm. The tests of the developed diaphragmless shock tube were performed using nitrogen at the atmospheric initial driven pressure, and at initial driver gauge pressures from 1 MPa to 7 MPa. The results show that the construction of the developed shock tube effectively reduces the generation of secondary shock waves and mechanical vibrations, which are often generated during the operation of shock tubes, thereby increasing the uncertainty of the shock tube calibration method. The uncertainty analysis shows that the developed diphragmless shock tube can act as a primary time-varying pressure calibration standard, generating pressure steps with a magnitude calculable from its measurement model to characterize the dynamic performance of pressure transducers with a relative expanded uncertainty of less than 0.025.

Diaphragmless shock tube for primary dynamic calibration of pressure meters

“…Using the measurement model of the shock tube (1), the amplitudes of the input pressure signals provided to the transducer under test were determined. A relative expanded uncertainty of the amplitudes of the pressure steps generated within the developed shock tube has been estimated to be less than 0.025 (for the detailed uncertainty analyses see [7]). Figure 4 presents the input signals and the output response signals, which were obtained by considering the sensitivity of the piezoelectric pressure measurement system specified by its manufacturer.…”

Dynamic Calibration of Pressure Sensors With the Use of Different Gases in the Shock Tube

“…where 𝑡 last and 𝑥 last are the passage time of the shock wave over the last side-wall pressure sensor installed downstream of the driven section and its location, respectively, 𝑥 wall is the location of the end-wall of the driven section and 𝑉(𝑥) is shock wave velocity distribution along the driven section determined using a time-of-flight (TOF) method [2]- [4].…”

Effect of the Dynamic Response of a Side-Wall Pressure Measurement System on Determining the Pressure Step Signal in a Shock Tube Using a Time-of-Flight Method

“…The study of the effect of the dynamic response of the side-wall PMS was realized on the developed diaphragmless shock tube of inner diameter of 40 mm with implemented fast-opening valve (FOV; ISTA, KB-40-100), see Figure 1 . The construction of the diaphragmless shock tube and the test procedure are presented in detail in [ 33 , 34 ]. In this paper, we analysed the results of the tests performed with dry nitrogen 5.0 at the atmospheric initial driven pressure P 1 and at the initial driver gauge pressures P 4, g from 4 MPa to 10 MPa.…”

“…Therefore, V wall is usually extrapolated from the velocity distribution along the driven section determined using a time-of-flight (TOF) method. This method determines the shock wave velocity along the driven section using the times of the shock wave passages over the side-wall pressure sensors t i with the centers at locations x i along the driven section [ 30 , 31 , 32 , 33 , 34 ]. Considering the quadratic model for the variation of the shock wave velocity V ( x ) = ax 2 + bx + c , four side-wall pressure sensors are required to obtain the constants a , b and c by solving the system of three equations [ 34 ]: where i = 1–3.…”

“…The most important uncertainty component of the pressure step amplitude given by Equation (1) is associated with the end-wall shock wave velocity V wall , which typically represents more than 90% of the uncertainty of the predicted pressure step. In [ 33 ] we estimated that for the lowest observed driver pressure the uncertainty contribution of the shock wave velocity represented approximately 99%, while, at the highest observed driver pressure represented approximately 93% of the uncertainty of the predicted pressure step. After upgrading the shock tube with an additional side-wall pressure sensor installed near the end of the tube, which enabled us to describe the nonlinear decelerations of the normal shock waves along the tube, the uncertainty contribution of the shock wave velocity still represented 96% of the combined uncertainty for the lowest observed driver pressure and 97% for the highest observed driver pressure [ 34 ].…”