Propagation Speed Of Pressure Wave Research Articles

Effect of instantaneous shut-in on well bore integrity and safety of gas wells

The instantaneous shut-in of the gas well produces a transient flow phenomenon. The repeated pressure amplitude and pressure repeated changes will cause the vibration of the tubing and equipment, resulting in damage to tubing and accessory equipment. However, it is difficult to directly adopt the conventional transient flow model due to the particularity environment of the gas well bore. Based on the classical transient flow theory and mechanism of transient flow process in a gas well, a mathematical model explaining the transient flow phenomenon of gas well is established and the method of characteristics is adopted for numerical solution. The calculation results of sample show that, after the wellhead valve is closed instantaneously, the surge pressure is transmitted and gradually attenuates under the influence of frictional resistance, and reaches the balance pressure after a period of time. With the increase of valve closure time, the maximum value of wellhead pressure is reduced, and the time of peak value occurs is also delayed. When the gas well is shut in for a short time, the propagation speed of pressure wave is faster than that in the circumstance of shutting the gas well in a longer time. The transient flow model can accurately reflect the value of surge pressure, the cycle of surge pressure and attenuation law of pressure wave, which has a high reference value for studying the transient process and pressure distribution in the gas well bore.

PREVENTION OF ACCIDENTAL POLLUTION WITH COMBUSTION GASES AFTER THE OCCURRENCE OF EXPLOSIONS

This paper aims to study the behavior of air-gas explosion systems, in terms of propagation speed of pressure wave and flame front, based on experimental measurements in a shock tube, in order to prevent accidental pollution with the combustion gases. The characteristic parameters of the explosion process determined using the shock tube, the velocity of propagation of the flame front, the speed of propagation of the wave of pressure, explosion pressure at various distances from the source of initiation, can be used in the preparation of explosion risk assessment studies for technological processes carried out in potentially explosive atmospheres. Taking the developed technical measures would make possible ensure both the explosion protection and the prevention of accidental pollution with combustion gases.

Measurement of Bulk Modulus and Study of its Impact on Transport Characteristics for Dense Paste

Dense paste is solid-liquid waste from industry production and sewage disposal process with high concentration and viscosity. It has large output, low utility rate and serious environmental pollution. While the engineering application of long-distance and large-diameter pipeline transportation solve the disposal of dense paste, the serious back-flow causes that actual throughput is far less than the theoretical. It is relevant to dense paste bulk modulus, which there has no related study. In this paper, we carried out a test on coal slime based on wave speed method theory. We get the bulk modulus by measuring the propagation speed of pressure wave in the pipe, and analyze its impact on actual throughput and effective stroke of piston.Verification shows that the scheme is feasible and provides reference for the further study between bulk modulus and transport characteristics.

キャビテーションジェットによるアルミニウム材料の壊食特性と気泡雲の崩壊現象について

As for cavitating jets injected from an orifice nozzle of inner diameter 0.15 mm at pressure 10-200 MPa into still water at atmospheric pressure, we conducted experiments of flow visualization of free jets with high-speed CCD camera at 50×104 fps and erosion tests of aluminum specimens. From these experiments, the following results were obtained. In erosion tests of cavitating jets, it is known that there are two peaks in mass loss curves, and besides, the peak of the diameter of eroded area was found to exist between two mass loss peaks. The distance may be suited to cleaning material and peening on metal for large damaged area and controlling erosion effect by adjusting injection pressure. The mass loss of downstream peak owing to collapses of cavitation clouds was highest at certain pressure. A high pressure pulse wave was generated 1-5 μs before the volume of cavitation clouds becomes smallest, the incidence frequency was of the order of 10 kHz, and the propagation speed of pressure wave was 1000-1100 m/s. Cavitation noise and erosion could be caused by these behaviors of cavitation clouds.

Volumetric properties at high pressure of waste oil methyl ester compared with diesel oil

In this paper, the isothermal compressibility coefficient, the cubic expansion coefficient and the propagation speed of pressure waves of waste oil methyl ester (WOME) and diesel oil (DO) are presented. These properties can be derived mathematically from the specific volume, the only property measured in this work (from 288.15 to 328.15K and from atmospheric pressure to 350MPa). The modified Tait–Tammann Equation has been adjusted to the experimental data with a high correlation coefficient and confidence level. Because of their different physical properties, the use of WOME instead of DO can affect the behaviour of some diesel equipments and, for instance, the economic efficiency and the behaviour of heat engines.