Analysis of the Flow Field Characteristics Associated with the Dynamic Rock Breaking Process Induced by a Multi-Hole Combined External Rotary Bit

The characteristics of the flow field associated with a multi-hole combined external rotary bit have been studied by means of numerical simulation in the framework of an RNG k-εturbulence model,and compared with the results of dedicated rock breaking drilling experiments.The numerical results show that the nozzle velocity and dynamic pressure of the nozzle decrease with an increase in the jet distance,and the axial velocity of the nozzle decays regularly with an increase in the dimensionless jet distance.Moreover,the axial velocity related to the nozzle with inclination angle 20°and 30°can produce a higher hole depth,while the radial velocity of the nozzle with 60°inclination can enlarge the hole diameter.The outcomes of the CFD simulations are consistent with the actual dynamic rock breaking and pore forming process,which lends credence to the present results and indicates that they could be used as a reference for the future optimization of systems based on the multi-hole combined external rotary bit technology.

A brief review of the development and optimization of the three-dimensional magnetic configuration system in the J-TEXT tokamak

The three-dimensional(3D) magnetic configuration system in the J-TEXT tokamak has featured in many experimental studies.The system mainly consists of three subsystems:the static resonant magnetic perturbation(SRMP) system,the dynamic resonant magnetic perturbation(DRMP) system and the helical coil system.The SRMP coil system consist of two kinds of coils,i.e.three six-loop coils and two five-loop coils.It can suppress tearing modes with a moderate strength,and may also cause mode locking with larger amplitude.The DRMP coil system consists of 12 single-turn saddle coils(DRMP1) and 12 double-turn saddle coils(DRMP2).Its magnetic field can be rotated at a few kHz,leading to either acceleration or deceleration of the tearing mode velocity and the plasma rotation.The helical coil system consists of two closed coils,and is currently under construction to provide external rotational transform in J-TEXT.The 3D magnetic configuration system can suppress tearing modes,preventing and avoiding the occurrence of major disruption.

Rare pattern of Maisonneuve fracture:A case report

BACKGROUND Maisonneuve fracture is a special type of ankle fracture that consists of proximal fibular fracture,a lesion of the inferior tibiofibular syndesmotic complex(interosseous ligament,anterior inferior tibiofibular ligament and posterior inferior tibiofibular ligament),and injury of the medial structure of the ankle(deltoid ligament tear or medial malleolar fracture).The accepted mechanism of Maisonneuve fracture is pronation external rotation according to the Lauge-Hansen classification.In this paper,we report a rare pattern of Maisonneuve fracture,which has the characteristics of both pronation external rotation ankle fracture and supination adduction ankle fracture.CASE SUMMARY A 31-year-old female patient accidentally sprained her right ankle while walking 5 d before hospitalization in our hospital.The patient was initially missed in other hospitals and later rediagnosed in our outpatient department.Full-length radiographs of the lower leg revealed proximal fibula fracture,inferior tibiofibular joint separation,and medial malleolar fracture involving the posterior malleolus,which was also revealed on computed tomography scans.Magnetic resonance imaging revealed rupture of the anterior inferior tibiofibular ligament and anterior talofibular ligament.We diagnosed a rare pattern of Maisonneuve fracture with proximal fibular fracture,inferior tibiofibular joint separation,medial malleolar fracture and ruptures of the anterior inferior tibiofibular ligament and anterior talofibular ligament.The patient underwent open reduction and internal fixation in our hospital.A 6-mo postoperative follow-up confirmed a good clinical outcome.CONCLUSION To our knowledge,this rare pattern of Maisonneuve fracture has not been previously described.The possible mechanism of injury is supination adduction combined with pronation external rotation.Careful analysis of the injury mechanism of Maisonneuve fracture is of great clinical significance and can better guide clinical treatment.

Effects of rotational speeds on the performance of a centrifugal pump with a variable-pitch inducer

The centrifugal pumps usually work at various rotational speeds. The variation in the rotational speeds will affect the internal flow, the external performance, and the anti-cavitation performance of the pump. In order to improve the anti-cavitation performance of the centrifugal pumps, variable-pitch inducers are placed upstream of the impeller. Because the rotational speeds directly affect the flow and the performance of the pump, it is essential to characterize the performance of the pump with a variable-pitch inducer at various rotational speeds. In this paper, the simulations and the experimental tests of a centrifugal pump with a variable-pitch inducer are designed and carried out under various rotational speed conditions. Navier-Stokes equations, coupled with a Reynolds average simulation approach, are used in the simulations. In the experimental tests, the external and anti-cavitation performances of the pump are investigated in a closed system. The following results are obtained from the simulations. Firstly, the velocity in the passage of the inducer rises with the increase of the rotational speed. Secondly, the static pressure escalates on the inducer and the impeller with the increase of the rotational speed. Thirdly, the static pressure distribution on the inducer and the impeller is asymmetric. Fourthly, the anti-cavitation performance of the pump deteriorates with the increase of the rotational speed. Additional results are gathered from an analysis of the experiments. H-Q curves are similar parabolas at various rotational speeds, while η-Q curves are similar parabolas only when n ≤6 000 r/min. The anti-cavitation performance of the pump deteriorates with the increase of the rotational speed. Finally, the simulation results are found to be consistent with the experimental results.