A new type of ice core drill bit, designed with a vane swirler, was developed for ice core drilling with air reverse circulation. An orthogonal experimental design method was employed to investigate the effects of the swirler structure parameters on the reverse circulation performance of the drill bit including helical angle, number of blades, blade length and blade central angle, etc. The entrainment ratio was used to evaluate the reverse circulation effectiveness of the drill bit. The results show that the helical angle is the dominant factor regardless of whether or not the flushing nozzles are part of the design of the drill bit. The number of blades is the least important factor for the drill bit designed with the flushing nozzles (referred to as drill bit I), while the outlet area of the swirling slot is the least influential factor for the drill bit without flushing nozzles (referred to as drill bit П). In addition, the appearance of the ice core has a certain effect on the air reverse circulation for both drill bits. Within the ranges of this study, the optimal structure of the drill bit was determined based on the range analysis of the orthogonal design.

Defoaming is a key technology for increasing the efficiency of foam drilling in petroleum engineering. To enhance the performance of a mechanical foam breaker in foam drilling, a novel aerodynamic foam breaker with two annular slits was investigated in this study. The computational fluid dynamics code of ANSYS Fluent was used to simulate the velocity and pressure distribution inside the foam breaker, and the optimum distance between the two annular slits was determined based on the simulation methods. Meanwhile, a series of experiments were conducted to test the actual performance of the foam breaker. The results demonstrate that various factors may affect the efficiency of the foam breaker, including the foam gas‐liquid ratio, basic liquid viscosity, and air supply method. A higher gas‐liquid ratio of the foam and air supply pressure result in a superior foam breaker performance. The viscosity of the foam liquid phase exhibits exactly the opposite behavior, meaning that the foam breaker more effectively destroys foam from a lower‐viscosity liquid. This study verifies the practicability of this novel aerodynamic foam breaker and discusses the effects of different parameters on the defoaming percentage, and this study can act as a reference and guidance for subsequent defoaming research.

Using an anti-icing coating to prevent ice accretion on the drill surface is a feasible solution to address the drilling difficulties in warm ice. In this study, four types of commercially available hydrophobic coating materials were tested to evaluate their water repellency and anti-icing properties, namely, a mixture of silica and fluorocarbon resin with polytrifluoroethylene, modified Teflon, silica-based emulsion and an acrylic-based copolymer. Their water contact angles are ~107°, 101°, 114° and 95°, respectively. All these hydrophobic coatings can significantly reduce the strength of the ice adhesion within a temperature range of −10 to −30°C on a planar or curved surface. The coating of an acrylic-based copolymer, in particular, can reduce the average tensile strength and the shear strength of the ice adhesion by 87.08 and 97.11% on planar surfaces at −30°C, and by 98.06 and 96.15% on a curved surface, respectively. The main challenge in the practical application of these coatings is their durability. An acrylic-based copolymer coating will lose its water repellency performance after 140 cycles of abrasion. The shear strength of ice adhered on curved surfaces coated with this material will approach that achieved on uncoated surfaces after 11 cycles of icing and de-icing tests.

No abstract

No abstract

No abstract

No abstract

To study the solidification effect of red mud, calcium carbide residue, and phosphogypsum mixture on Cu2+-contaminated soil under the soaking condition, the stress-strain, leaching toxicity, and microstructure of solidified soil with cement and mixture were systematically analyzed. The results show that the peak stress of the mixture solidified soil increases with the curing age, and the addition of solid waste is beneficial for the improvement of peak stress. Its leaching concentration of copper ion is not only lower than that of cement solidified soil, but also lower than 0.6mg·L−1. Besides, the leaching concentration decreased gradually with the curing age. According to the microstructure of solidified soil, it is found that the hydration products of the solidified soil are mainly represented by calcium silicate hydrate/calcium aluminosilicate hydrate and ettringite, which play an important role in the development of the strength and the solidification of copper ions.