Numerical research on rock breaking by abrasive water jet-pick under confining pressure

Dajun

2022

Geofluids

Ultrahigh frequency impact technology has great potential to break hard rocks with lower energy consumption. Based on the infrared nondestructive testing technology, the effects of load (i.e., amplitude) and boundary (i.e., confining pressure) conditions on granite damage under ultrahigh frequency impact have been investigated to promote the application of this technology in rock engineering. Experimental results demonstrate that the evolution law of the maximum radiation temperature on granite surface reflects the granite damage state. Under ultrahigh impact, granite specimens are damaged effectively with the impact amplitude exceeding 32 μm, and the failure mode of the specimen is changed by the confining pressure. Depending on Griffith’s theory, the extension angle of the fatigue crack changes from 60 to 30 degrees with increasing confining pressure. And the transverse fracture occurs in the upper part of the specimen under ultrahigh frequency impact subjected to confining pressure. This research determines the amplitude threshold of the ultrahigh frequency impact load and verifies the effectiveness of ultrahigh frequency impact technology for granite failure subjected to confining pressure.

Section: Mathematical Relationship Between Rock Stress Andmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Amplitude and Confining Pressure on Granite Failure under Ultrahigh Frequency (UHF) Impact Based on Radiation Temperature

Dajun

2022

Geofluids

“…So, compared with the free-air environment, the impinge efficiency of a single-phase water jet in a submerged environment is relatively poor. To improve the impinge capability of water jet in the submerged environment, scholars and engineers have made many efforts, such as adding abrasive into the water, 14,15 mixing gas into water. 16,17 Although the impinge capability of an abrasive jet is strong, the wear of the abrasive on nozzle wall is very serious.…”

Section: Introductionmentioning

confidence: 99%

Flow field characteristic of water jet with air ring protective layer under submerged environment and the orthogonal optimization of nozzle structure

Energy Science & Engineering

et al. 2022

A water jet with an air ring protective layer is a promising rock-breaking and cutting rate improvement method in submerged environment, such as oil-gas drilling. The jet flow field characteristic determines the jet impinge performance and is affected by nozzle structure parameters. In this study, the water jet flow with air ring under submerged environment was numerically simulated. The jet flow field structure with air ring was obtained by analyzing the distributions of jet velocity and air content at different cross sections. The effects of several critical nozzle structure parameters on jet isokinetic core length and axial velocity were investigated by adopting the orthogonal design method. The results show that the jet flow field structure with air ring in radial direction includes a high-speed water jet zone, air ring protective layer, and air-water mixed zone, having the advantages of concentrated energy in axis region, long core section length, and lowvelocity attenuation. The influence degrees of nozzle structure parameters on jet core section length and axial velocity at X = 0.3 m are: length-diameter ratio > outlet diameter > conic angle > air nozzle diameter > water-air nozzle spacing and outlet diameter > length-diameter ratio > conic angle > water-air nozzle spacing > air nozzle diameter, respectively. The jet core section length and axial velocity both increase exponentially with the increasing outlet diameter, both first increase rapidly and then slowly decreases with the increase of conic angle and water-air nozzle spacing. There is the optimal conic angle of 15°and appropriate water-air nozzle spacing of 3-5 mm. With the increase of length-diameter ratio, they both first decrease rapidly and then slow down, indicating that conical nozzle is more suitable for water jet with air ring. And 0.9-1.2 mm is proper for the air nozzle diameter.

“…For hard coal seams, there are currently some new coalcrushing technologies, which are classified according to their working principles and can be divided into jet crushing [7][8][9], jet-assisted mechanical crushing [10][11][12][13], special-shaped pick crushing [14,15], and laser crushing [16,17]. In recent years, these methods were carried out fruitfully by scholars.…”

Section: Introductionmentioning

confidence: 99%

Numerical and Experimental Study on Crushing Properties of Hard Coal Using Impacting-Cutting Technique

Wang

Tian

2022

Shock and Vibration

The reserves of high-quality coal seams have been greatly reduced in recent years, and the low efficiency of traditional cutting methods in hard coal seams has become a problem for the coal production industry. In order to improve the mining efficiency, an impacting-cutting technique was proposed in this study. A drum modification model with picks impact function was established, and crushing properties of the impacting-cutting drum at f4, f5, and f6 coal hardness were simulated using the discrete element method. The simulation results show that the impacting-cutting drum has higher coal crushing efficiency, lower drum force, and more stable cutting processes than the traditional drum. It shows that hard coal might be effectively reduced by the impacting-cutting technique to reduce the difficulty of mining, and reflected the applicability in hard coal seams. Meanwhile, a simplified test device for the impacting-cutting technique was designed. And the actual coal crushing performance was tested. The test results show that the force of the cutting mechanism in the impact mode is lower than that of the nonimpact mode, and the force is more stable. It proves that the impacting-cutting technique has a higher applicability of hard coal seams than the traditional technique.