• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.1
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• pp.1-13
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• 2010

A comparative study between a computation and an experiment has been conducted to predict the performance of a Pod type waterjet for cm amphibious wheeled vehicle. The Pod type waterjet has been chosen on the basis of the required specific speed of more than 2500. As the Pod type waterjet is an extreme type of axial flow type waterjet, theoretical as well as experimental works about Pod type waterjets are very rare. The main purpose of the present study is to validate and compare to the experimental results of the Pod type waterjet with the developed CFD in-house code based on the RANS equations. The developed code has been validated by comparing with the experimental results of the well-known turbine problem. The validation also extended to the flush type waterjet where the pressures along the duct surface and also velocities at nozzle area have been compared with experimental results. The Pod type waterjet has been designed and the performance of the designed waterjet system including duct, impeller and stator was analyzed by the previously mentioned m-house CFD Code. The pressure distributions and limiting streamlines on the blade surfaces were computed to confirm the performance of the designed waterjets. In addition, the torque and momentum were computed to find the entire efficiency and these were compared with the model test results. Measurements were taken of the flow rate at the nozzle exit, static pressure at the various sections along the duct and also the nozzle, revolution of the impeller, torque, thrust and towing forces at various advance speed's for the prediction of performance as well as for comparison with the computations. Based on these measurements, the performance was analyzed according to the ITTC96 standard analysis method. The full-scale effective and the delivered power of the wheeled vehicle were estimated for the prediction of the service speed. This paper emphasizes the confirmation of the ITTC96 analysis method and the developed analysis code for the design and analysis of the Pod type waterjet system.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.5
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• pp.533-551
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• 2015

The rock fracturing during waterjet cutting is very complicated because rock is inhomogeneous and anisotropic, compared with artificial materials (e.g., metal or glass). Thus, it is very important to verify the effects of rock properties on waterjet rock cutting performance. Properties affecting the rock cutting efficiency have been variously described in the literature, depending on the experimental conditions (e.g., water pressure, abrasive feed rate, or standoff distance) and rock-types studied. In this study, a rock-property-related literature review was performed to determine the key properties important for waterjet rock cutting. Porosity, uniaxial compressive strength, and hardness of the rock were determined to be the key properties affecting waterjet rock cutting. The results of this analysis can provide the basic knowledge to determine the cutting efficiency of waterjet rock cutting technology for rock excavation-related construction.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.922-927
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• 2004

Abrasive waterjet (AWJ) cutting is an emerging technology for precision cutting of difficult-to-machining materials with the distinct advantages of no thermal effect, high machinability, high flexibility and small cutting forces. This paper investigated theoretical and experimental cutting characteristics associated with abrasive waterjet cutting of quartz GE214. It is shown that the proper variations of several cutting parameters such as waterjet pressure, cutting speed and cutting depth improve the roughness on workpiece surfaces produced by AWJ cutting. From the experimental results by AWJ cutting of quartz GE214, the optimal cutting conditions to improve the surface roughness were proposed and discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.118-126
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• 2005

Abrasive waterjet (AWJ) cutting is an emerging technology for precision cutting of difficult-to-machining materials with the distinct advantages of no thermal effect, high machinability, high flexibility and small cutting forces. This paper investigated theoretical and experimental cutting characteristics associated with abrasive waterjet cutting of quartz GE214. It is shown that the proper variations of several cutting parameters such as waterjet cutting pressure, cutting speed and cutting depth improve the roughness on workpiece surfaces produced by AWJ cutting. From the experimental results by AWJ cutting of quartz GE214, the optimal cutting conditions to improve the surface roughness and precision were proposed and discussed.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.47-53
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• 2002

The hydraulic design optimization and performance analysis of mixed-flow pumps for waterjet marine vehicle propulsion has been carried out using mean streamline analysis and three-dimensional computational fluid dynamics (CFD) code. In the present study the conceptual design optimization has been formulated with a non-linear objective function to minimize the fluid dynamic losses and then the commercial CFD code was incorporated to allow for detailed flow dynamic phenomena in the pump system. New designed mixed-flow model pump has been tested in the laboratory. Predicted performance curves by the CFD code agree very well with experimental data for a newly designed mixed-flow pump over the normal operating conditions. The design and prediction methods presented herein can be used efficiently as a unified hydraulic design process of mixed-flow pumps for waterjet marine vehicle propulsion.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.4
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• pp.21-30
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• 1997

This paper describes the experimental method of a pod-type waterjet propulsion system in a towing tank and shows the experimental analysis and test results of a designed waterjet propulsion system to be used for a hybrid high speed craft. The cruising performance of this craft is estimated from the results of the hull resistance test and waterjet test under the assumption that the interaction between the hull and the inlet pod is very small. A pod-type waterjet system with an axial pump was designed and a stand-alone waterjet experimental system was developed. Useful data such as the pump performance, the jet efficiency, the losses of inlet duct and nozzle were obtained. Test results show a good agreement with the design requirement.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.763-778
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• 2019

Abrasive waterjet cutting technology has been used for rock excavation of tunnels and underground structures due to various advantages. In order to cut rocks by using the abrasive waterjet system, abrasive is essential to enhance impact energies for fracturing the target rock. Since garnet abrasives are not produced in Korea, alternative abrasives, instead of garnets, are needed to achieve the economical waterjet cutting. This study is to analyze cutting performance for rocks with sandy particles as alternative abrasive. Cutting tests were carried out on granite specimens at the constant waterjet energy (e.g., water pressure or water flow rate). The five kinds of sands, sampled by construction fields and natural sites, were prepared to perform the experimental tests. When sea sand was used as an alternative abrasive, cutting performance was secured to be 60~70% compared to the commercial garnet abrasive. Thus, it is expected that sand abrasives can be applied on the waterjet cutting process for the economical excavation construction.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.4
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• pp.421-435
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• 2012

Rock excavation (removal) tests are performed with effective parameters using an abrasive waterjet. For verification of the field rock excavation capabilities, the removal performance and level of efficiency are analyzed for hard granite rock in terms of the water pressure, exposure time of the jet, and the standoff distance. In particular, experimental tests are performed with a long standoff distance required condition in the real excavation field. The rock removal performance level changes according to the rock properties. In this study, various rock specimens are used and P-wave velocities are measured in order to determine the correlation between the removal performance and the P-wave velocity. As a result of the experimental study, the effect of waterjet parameters on rock removal is analyzed.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.1
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• pp.30-37
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• 2010

In order to control the weight balance of the waterjet propulsion ship, the pump's weight needed to be decreased. We reduced length of pump hub, overall length of pump and chord length of impeller and stator. To keep pump efficiency and cavitation performance similar to the $1^{st}$design pump, optimum design and experiment were conducted. This paper describes experimental method and numerical analysis for pump design. At the blade design stage, performance analysis of the pump is conducted using commercial CFD codes ($BladeGen^+$,CFX-10). Required performance and cavitation characteristics of the design pumps were measured and observed using the stand-alone test apparatus. The weight of the pump was successfully decreased through a series of pump design processes composed of blade design, performance analysis and model test.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.5
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• pp.517-528
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• 2012

Inserting a nozzle assembly into a removed cutting space during a continuous cutting operation is necessary in rock excavation using an abrasive waterjet. In this study, a combined two nozzle assembly is used to secure enough removal width. The shape of the cut space is affected by the geometric parameters (standoff distance, nozzle angle, and vertical distance between the nozzle tips) of the combined nozzle assembly. Abrasive waterjet cutting tests are performed with various geometric parameters for granite rock specimens. Optimized geometric parameters for the nozzle inserting process are determined and verified through the experimental tests.