Peiqi Liu

Stress of Make-Up Torque on the Gas Storage Well Bore and Coupling Connecting Thread

Abstract The structure of wellbore and coupling is connected by thread, it is the position where fatigue failure accidents are happened in gas storage well, and the make-up torque of thread is the key factor that influences the mechanical properties of this structure. In this pa- per, a finite element method was established to discuss the calculation method of make-up torque and the influence law on the stress of coupling in the gas storage well. Results show that the make-up torque cannot be simply ignored due to its great impact on internal stress distribution of gas storage well. Experimental results showed the correctness of the model. Under the action of the make-up torque, the overall stress level inside the wellbore is higher than the external coupling. However the maximum stress exists in the external coupling. The overall stress grad- ually increases with the increase of interference rotation number (abbr. RN) between coupling and wellbore, but the overall distribution trend is almost the same. The first thread on the left of the connection part is the area where fatigue failure is most likely to occur. The make-up torque between threads increases linearly with the increase of RN between cou- pling and wellbore.

Influence of Non-equilibrium Condensation on key Parameter of Gas Wave Refrigerator

The offset angle, which is adjustable, is a key parameter of gas wave refrigerator, affecting refrigeration performance. When the high pressure moist gas injects into the oscillation tube of the refrigerator, the non-equilibrium condensation will occur. Phase transition will impact the wave system in the tube and then change the optimal offset angle of the gas wave refrigerator. In this paper, a 2D model of the non-equilibrium condensation in oscillation tube is established to investigate the condensation influence on the optimal offset angle. The results show that: at constant offset angle, with the increase of rotation speed, refrigeration efficiency raises first and then decreases resulting from wave system difference. It shows optimal offset angle truly exists under every working condition, going for optimal wave system match. Condensation process will cause temperature-jump and condensation compression wave which affects wave system in the tube, so the optimal offset angle changes. Since the final Mach number of shock wave increases linearly with the raise of RH (0~0.8), the optimal offset angle decreases linearly. When RH= 0.8, the optimal offset angle decreases by 7%.