Focus on Magnetics

Various Disaster response robots are developed and used for the search and rescue operations. We demand new actuation technology for such a tough field. In this paper, we propose a new actuation technology by water jets. We developed the instrument, which activate the water hose. This consists of a water pump, hoses, and jet nozzles. We observed the motion of the activated hose by water jets. The preliminary experiments were conducted to confirm the potential of new actuation technology for disaster response robots

Focus on magnetics and electromagnetism

Focus on sensors

Aiming at increasing design efficiency of the jet nozzle and improving scouring and cleaning efficiency of water jet,based on theoretical analysis of the mechanism of self-resonating cavitating (SRC) jet nozzle,different units of organ-pipe SRC jet nozzles are designed. The vibration of organ-pipe SRC jet nozzle and target is measured during the jet process. The vibration characteristic and frequency characteristic of SRC water jet are studied by the comparative analysis of the vibration signals. It is found that the high frequencies in the vibration frequency-domain map of SRC jet nozzles are caused by the high frequency vibration due to the impact of broken bubbles in the resonator,the modulation frequency,i.e. harmonic frequency of self-resonating in the resonator of SRC jet nozzles is found in the vibration frequency-domain map of SRC jet nozzles. The measured value is consistent with that of the theoretical calculation. The effects of the main structural parameters,i.e. nozzle diameter,resonator length of an organ-pipe SRC jet nozzle on SRC water jet are obtained,and the optimum structural parameters of SRC jet nozzle are obtained according to setting testing system. The result of vibration analysis experimental research is in good agreement with that of simulation study,and the effective method of optimum design of SCR jet nozzles is obtained.

Oil shale is an unconventional energy source, and it is also a potential petroleum substitute. Nowadays, the energy shortage is becoming more and more prominent, oil shale has attracted the attention of energy researchers all over the world. Borehole hydraulic mining is an effective method to exploit the underground oil shale which has more prominent advantages than other conventional mining methods. Jet devices are the key component of borehole hydraulic mining, which include the straight cone nozzle, organ pipe nozzle and self-excited oscillation pulsed jet nozzle. Also, the reasonable mining parameters are also crucial in mining underground oil shale efficiency. The jet characteristics of the non-submerged water jet, submerged water jet, direct water jet, cavitating water jet, and pulsed water jet are also explained and compared based on theoretical analysis. The jet performance of the non-submerged water jet is better than the submerged water jet. Each type of jet devices has its own basic principles and optimal structural parameters. The best operating scheme of borehole hydraulic mining for underground oil shale is to use the pulsed water jet which is produced by the self-excited oscillation pulsed jet nozzle to break underground oil shale under the non-submerged condition. Moreover, the pulsed water jet should be placed parallel to the oil shale bedding. In addition, under the preconditions of ensuring the safety and reliability of the hydraulic mining equipment and pipelines connection, the jet pressure and jet flow should be raised as much as possible, so as to obtain the much higher mining efficiency. These results and conclusions can provide very valuable guidance for borehole hydraulic mining of underground oil shale.

Wear characteristics of the cemented carbide blades in drilling limestone with water jet

Study on the mechanism of soil erosion by submerged water jet vertical scouring in cohesive soils

High-pressure water has been recognised as a possible method for excavation of hard rock for many years. Despite large amounts of research and development into water jet rock cutting devices, there has not been any widespread implementation within the mining industry. Many investigations have demonstrated that pulsed jets have improved excavation and higher efficiency than continuous jets. This thesis was aimed at validating such claims by conducting research, design, development, testing and analysis. Included is a comprehensive review of the existing literature regarding the application of pulsed water jets for rock cutting. The review of the literature has revealed that pulsed water jets offer many advantages over continuous water jets. It also lead to the conclusion that of all the devices utilised for pulse jet creation, self-resonating nozzles have the most potential for improved hard rock excavation. The existing nozzle theories and equations were used to develop a new nozzle capable of operating at higher pump pressures (90 MPa) for hard rock and scale cutting applications. In order to evaluate the effectiveness of the designed and manufactured selfresonating nozzle compared to standard continuous water jet nozzles, a series of comparative penetration tests were proposed. Due to unforeseen problems with equipment availability, the proposed testing program was only partially completed. The completed tests included pump pressure variation and stationary impact tests. The pump pressure variation test results revealed that there was slight evidence of improved performance at the designed pump pressure of 90 MPa. However, it is difficult to make this conclusion from one data set. The stationary impact test results showed that the pulsed jet performed quite well. It outperformed the majority of the continuous jet nozzles except for the Leach and Walker nozzle. The Leach & Walker nozzle has undergone years of research, development and refinement, whereas these tests are the first for the self-resonating nozzle. Therefore, it is envisaged that with increased research and development, the self-resonating nozzle has the potential to outperform the Leach & Walker nozzle. The test results have shown that there is potential for self-resonating pulsed water jets to be implemented into the mining and other industries for hard rock and scale excavation applications. The results and knowledge gathered as part of this thesis have given a good grounding for further research into pulsed water jets. In order to progress from the current stage to a situation were self-resonating pulsed water jet devices can be implemented, on a widespread scale, into the mining industry further research is required. Recommendations for future studies include completing the proposed testing program, conduct flow modelling simulations, analyse operational parameters such as pump pressure, stand-off distance and pulse frequency and conduct photometric and pressure transducer tests.

Focus on Laboratory Equipment

The energy transfer method is used to measure the flow velocity of the outside the high pressure water jet (WJ) and Abrasive water jet (AWJ) nozzle. The impact forces of the flow measured by the piezoelectricity ergometer will be transformed to the velocity value, the average velocity of the flow outside the nozzle will be obtained. The result indicates the velocity will reduce along the direction of the flow, and the velocity of the AWJ flow will reduced greatly than the WJ flow, which indicates that the length of the core part of the AWJ flow is shorter than the WJ Flow, the stand-off should be within the 0mm-15mm ranges to gain the most effective machining.

Water jet peening is a good potential method to control welding residual stresses. The water jet with elliptical nozzle can improve the treatment efficiency due to its large treatment area. In this article, the water jet velocity and dynamic pressure for different elliptical nozzle dimensions and standoff distances are discussed by numerical simulation. The results show that when the axial distance is 10 mm, the effective impact diameter of the elliptical nozzle a/b=8–12 is about 2 times or more than that of the circular nozzle. The length of the jet core of the elliptical nozzle is only related to the outlet structure and is independent of the inlet pressure. The correlation between the dimensionless core length of the elliptical water jet and its long and short axes is derived. When the ratio of the major axis to the minor axis is between 7 and 13, the core length of the elliptical water jet is 7–7.5 times that of its minor axis. Combining the suitable treatment area and dynamic pressure, the elliptical nozzle with an axis ratio of 8 is recommended to control the welding residual stress. Finally, a new formula for calculating dynamic pressure distribution is proposed for the elliptical nozzle water jet at different stages.

A new manufacturing process with abrasive water jet is proposed to fabricate micro channels or dimples on glass. Masks having exposed areas cover the surface so that the covered areas cannot be machined. Because the width of the exposed areas is much smaller than the diameter of the jet nozzle, tapers are made in the cross section of the masks so that abrasive slurry can reach the exposed surface. Abrasive slurry is mixed with water supplied by a low-pressure pump in a water jet nozzle. When abrasive water flows onto the surface vertically between the taper-shaped masks, stagnation is made right under the nozzle. Because the flow velocity is low in stagnation, brittle fracture does not happen on the machined surface. The vertical flow also changes to the horizontal direction at a high velocity out of the stagnation. Abrasive particles, therefore, machine the surface in the horizontal direction at a high velocity. The jet nozzle moves back and forth for several times along the exposed area. A V-shaped groove, which is a depth of 2.5µm and a width of 20µm, can be machined on the surface of fused silica. A micro fabrication machine is made to fabricate micro grooves at the specified positions and angles. It is shown that the machine works well to make micro patterns on the surface in some examples. A machining example proves that the machined shape can be predicted with computational fluid dynamics

The transportation characteristics of a 45°-bend jet pump, which has a 45° bend connected directly to a water jet nozzle from outside of the bend, are discussed theoretically and experimentally. The transportation characteristics, which are predicted theoretically using the continuity, momentum and energy equations, agree well with the experimental results in the case of transporting water and solid spheres. When cavitation bubbles occur in the jet nozzle, the transportation characteristics, which are predicted theoretically considering a holdup of gas-liquid mixed fluid, agree well with the experimental results. The efficiency of the jet pump becomes higher as both the area ratio of the jet nozzle to the transporting pipe and the discharge ratio of solid spheres to water flow become larger.

Experimental study on rock-breaking performance of water jets generated by self-rotatory bit and rock failure mechanism

Abstract. Using water jets in orthopedic surgery to drill holes in bones can be beneficial due to the absence of thermal damage and the always sharp cut. To minimize operating time and the volume of water that is used, the efficiency (volume of removed bone per added volume of water) of the water jet should be maximized. The goal was to study the effect of the open trabecular bone structure on the efficiency for different water jet diameters. 86 holes were drilled in porcine tali and femora submerged in water with nozzles of 0.3, 0.4, 0.5 and 0.6 mm at 70 MPa during 5 s and a standoff distance of 8 mm. MicroCT scans were made to measure the removed bone volume and the bone structural properties Trabecular Spacing (Tb.Sp.), Trabecular Thickness (Tb.Sp.) and Bone Volume Fraction (BV/TV). Pearson's correlation tests (p < 0.05, 95% confidence interval) were performed for each water jet diameter using the bone structural property as an independent factor and the efficiency as a dependent factor. No significant differences were found between the nozzle diameters in the material removal rates per added volume of water. The efficiency decreased for an increase in Tb.Th. and BV/TV for nozzles of 0.3, 0.4 and 0.5 mm. The 0.6 mm nozzle showed less influence of the Tb.Th. and BV/TV. The Tb.Sp. has no influence on the efficiency of a water jet. The total volume of added water combined with the Tb.Th. or BV/TV is a leading measure for the volume of bone material that is removed, which provides freedom in the development of water jet instruments as the nozzle diameter, pressure and jet time can be chosen in accordance to the maximum operating time requirements or dimensional limitations of a design.