Ken Shimojima

Mechanism of the Shock Wave Generation and Energy Efficiency by Underwater Discharge

We are developing the rice powder manufacturing system using an underwater shock wave. The purpose of this study is to research a mechanism of the shock wave generation and energy efficiency by underwater discharge in order to increase energy of the underwater shock wave. We observed the shock wave generation using the visualization device with a high speed camera, and measured voltage current characteristics at the same time. As a result, it was clarified that countless underwater shock waves were generated at the time of water plasma expansion by discharge. But, the shock wave was not confirmed at the time of after a second peak of the damping oscillation. It was clarified that one part of charging energy was used to generation of the shock wave. Therefore, it was clarified that to release energy by the critical oscillation is desirable for efficient generation of the shock wave.

Optical examination of shockwave propagation induced by an underwater wire explosion

We have been investigating underwater-explosion-induced shockwave-propagation phenomena for use in a robust food-processing system. This system comprises a high-voltage capacitor bank with gap switch, water tank, and wire explosive. We carried-out optical observation of the shockwave generated by a wire explosion using electrical discharge in the water tank. Simultaneously, we measured the shock pressure and investigated the effects of various electrical characteristics upon the shockwave-propagation phenomena. To obtain various strengths of the underwater shockwave, 0.6-, 1.0-, and 1.4-mm-wide wires made from 1.0-mm-thick aluminum plates were used at various voltages. As an example, a shockwave having a propagation velocity of 1,600 m/s was observed using the explosion of the 1.0-mm-wide aluminum wire. We found that the strength of the shockwave could be well-controlled by the discharge voltage and wire size.

Development of the rice-powder manufacturing system using underwater shock wave

Self-sufficiency in food is very low (about 40%) in Japan. Therefore, the rice powder is paid to attention because it can be processed to the udon (noodle) and bread etc. We has already developed the rice-powder disintegrator using the underwater shock wave by the electrode. But it has not been cleared what is the most suitable pressure vessel. The purpose of this study is to investigate the most suitable configuration of the pressure vessels for manufacturing the rice-powder using the underwater shock wave. Experimental conditions to manufacture the rice-powder (particle size is 100 μm) is clarified using this device. Moreover, the manufacturing efficiency of the rice-powder, the relation between the number of the shock wave generation and the grain degree of rice-powder is clarified.

Development of the Pressure Vessel for Manufacturing the Rice-Powder Using the Underwater Shock Wave

We have been researching the food processing technology by using the underwater shock wave. The rice-powder used for various foods has been demanded in Japan now. The purpose of this study is designing and development of the pressure vessels for the manufacturing rice-powder device using the underwater shock wave. The pressure vessel was made into the oval shape which focuses the energies generated under the underwater shock wave. The speed and pressure of the shock wave which were generated underwater are confirmed with a high speed camera. The durability and performance of this device is confirmed by manufacturing the rice-powder.Copyright

Examination of Power Supply of the Rice Powder Making Device With the Pressure Vessel Having the Clear Window Using Underwater Shock Wave

We have developed the rice powder production device using the underwater shock wave. The spark by a high-voltage power supply was used for generating of a shock wave. We developed two types of the high voltage power supplies, the CR circuit using transformer, Cockcroft-Walton circuit (CW circuit). We developed the vessel having the window for observation of shock wave. Generated pressure and velocity of the shock wave are evaluated using shadowgraph method used two power supplies (CR circuit and CW circuit).Copyright

Design and Development of Pressure Vessel for Improvement of Manufacturing rice-powder Efficiency using Underwater Shock wave

The rice-powder paid to attention in Japan, because the various food made by rice-powder. But, conventional method of manufacturing rice-powder generates heat when crushing of rice. One the other hand, the pressure vessel of oval structure for manufactured rice-powder using underwater shock wave has been developed in Okinawa National College of Technology. The merits of this system manufacture rice-powder without heating. But, the efficiency of this system is low. Therefore, in this paper, we propose new design of pressure vessel for the highly effective rice-powder manufacturing. To design a new pressure vessel, it is clear that the performance of the oval structure pressure vessel. And, we design and manufacturing new pressure vessel for the highly effective rice-powder manufacturing.

Experimental Verification of the Softening of the Pork Using Underwater Shock Waves Generated by Wire Electrical Discharges

The National Institute of Technology, Okinawa College (OkNCT) has developed a food processing machine that generates underwater shock waves through wire electrical discharge. The machine can used for sterilization, milling flour, softening, and extraction among others. In this study, we experimentally examined the conditions for food softening using pork as the food material in experiments. Softness was revealed to be related to the distance of shock wave generation point from meat and the number of shockwave processing.

Production and Evaluation of Pressure Vessel for Highly Effective Rice Powder Manufacturing Using Underwater Shock Wave

The rice-powder paid to attention in Japan, because rice-powder is able to process the various foods. But, conventional method of manufacturing rice-powder generates heat when crushing of rice. The pressure vessel for rice-powder using underwater shock wave at Okinawa National College of Technology has been developed. Merit of this crushing processing is dryness and non heating. The decrease of the manufacturing cost can be expected. The power supply to generate the pressure vessel and the shock wave for crushing and the transportation device of rice was developed. The amount of the milling flour of the first prototype device was 450[g/h]. Then, the pressure vessel is improved, the shock wave generation energy is improved, and the amount of the milling flour has been improved with 2kg per hour. In this report, the outline of the improved device is described. And, the factor that influences the milling flour is shown, and the evaluation method is described.Copyright

Study of the Suitable Pressure Vessel for the Rice-Powder Manufacturing Using the Underwater Shock Wave

Self-sufficiency in food is very low (about 40%) in Japan. Therefore, the rice powder is paid to attention, because it can be processed to the udon (noodle) and bread etc. We have already developed the rice-powder disintegrator using the underwater shock wave by the electrode. But it has not been cleared what is the most suitable pressure vessel. The purpose of this study is to investigate the most suitable configuration of the pressure vessels for manufacturing the rice-powder using the underwater shock wave.Experimental conditions to manufacture the rice-powder (particle size is 100μm) is clarified using this device.Moreover, the manufacturing efficiency of the rice-powder, the relation between the number of the shock wave generation and the grain degree of rice-powder is clarified.Copyright

Numerical Simulation of Electrical Discharge Characteristics Induced by Underwater Wire Explosion

The underwater shock-wave phenomenon has been applied in various fields such as manufacturing and food processing and was investigated using many experimental and numerical analyses in the past. An underwater shock-wave is produced by various methods, e.g., underwater wire explosion and pulse-gap electrical discharge. Therefore, clarifying the shock characteristics depending on the stored electrical energy, wire dimension and material is extremely important. However, predicting the pressure and its distribution induced by underwater electrical wire explosion is hard because the phenomena associated with an elementary process are significantly complicated. In this study, to predict the discharge characteristics induced by underwater electrical wire explosion, numerical simulation based on the “simplified model of underwater electrical discharge” was performed. The numerical results show good agreement with the experimental ones.