Papers by Author: Shigeru Itoh

Abstract: 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.

Abstract: In this study, we have established a novel pretreatment system that improves the juice extraction volume and nutritional value of plant material using underwater shockwaves. The optimum treatment conditions for plant materials were obtained by conducting batch experiments using simple-structured underwater shockwave treatment equipment. From these results, a continuous underwater shockwave processing device was designed. Moreover, we have been demonstrated the applicability and reliability of underwater shockwave pretreatment in improving the yield of functional ingredients and fruit juice from plants. The instantaneous high-pressure dynamic control using underwater shockwaves is applicable to a wide range of extraction processes such as extraction of juices or ingredients from other naturally occurring foods and medicinal plants.

Abstract: 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.

Abstract: It is known to be able to expect the improvement of the harvest if the cropping time can be made early in a cold region such as Russia, Norway, Sweden and Hokkaido in Japan. Therefore, for the purpose of making cropping time early as much as possible, we researched the destruction of the frozen soil by the explosive. In the simple experiment, as compared with the experiment which placed the explosive directly on top of the frozen soil, it broke greatly in the experiment which poured out water 20 mm in height after placing an explosive directly on top of the frozen soil. Furthermore, it was found that the thawing time of residual frozen soil in the experiment using water is shorter than without water. In this research, in order to investigate the effect of the covered water in thawing frozen soil by explosive load, the numerical simulation was performed. The result of the numerical simulation was well in agreement with the experimental result, and it was clarified that destruction effect is increased by covering with water.

Abstract: We propose a new method for the efficient decompression of frozen food under high dynamic pressure. Two experiments are conducted on an ice block containing peeled shrimp: wire explosion and underwater shock wave. In these experiments, the ice is finely crushed, while the frozen peeled shrimps retain their original shape and can be efficiently extracted. Since ice crushing is performed momentarily, the defrosting time is significantly shorter than that in traditional thawing techniques, such as melting in running water or cold-water soaking. This new method could increase the efficiency of food production processes.

Abstract: This study attempts to clarify underwater shock waves using a food container designed for food processing. The underwater shock wave is driven by a spark or wire explosion from a high-capacity condenser bank. Since the applied pressure must be known to control the experimental conditions, a numerical simulation was conducted and the results were compared with measurements using an elastic bar placed in the water.

Abstract: The aim of study is to confirm a new technique that can crush the frozen soil and/or ice block using underwater shock wave generated by the underwater explosion of explosive. This technique can lead to the earlier sowing, which can have the larger harvest because the duration of sunshine increases. Especially, in Hokkaido prefecture, Japan, if the sowing is carried out in April, we can expect to have 150% of harvest in the ordinary season. This technique is effective against the cold regions, for example, Russia, Norway, and Sweden, etc. In order to check about that influence we tried to give an actual frozen soil a shock wave. We could get a result that existence of water layer serves an important role in promotion of thawing by the shock loading to the frozen soil. That role was confirmed from the result of numerical simulation.

Abstract: The metal jet that is flowed out by the oblique collision between a metal flier plate and a metal block becomes a high velocity. We have been developing the device that makes a material extremely high pressure by using the metal jet. The flier plate of the previous device had been accelerated by using a high explosive. There were several problems in the collection and analysis of the material that had been made the high pressure. Therefore we thought up the new device of which the flier plate was accelerated by a powder gun. The collision process was examined by a numerical simulation because the collision process of the flier plate of this device differs from that of the previous device. LS-DYNA was used for a numerical simulation and the difference of the collision process was clarified.

Abstract: Explosive forming is one of the unconventional techniques, in which, most commonly, the water is used as the pressure transmission medium. The explosive is set at the top of the pressure vessel filled with water, and is detonated by an electric detonator. The underwater shock wave propagates through the water medium and impinges on the metal plate, which in turn, deforms. There is another pressure pulse acting on the metal plate as the secondary by product of the expansion of the gas generated by detonation of explosive. The secondary pressure pulse duration is longer and the peak pressure is lower than the primary shock pressure. However, the intensity of these pressure pulse is based also on the conditions of a pressure vessel. In order to understand the effects of the configuration of the pressure vessel on the deformation of a metal plate, numerical simulation was performed. This paper reports those results.

Abstract: We are developing the food processing system by using the underwater shock wave. The effect of the underwater shock wave on the pressure in the vessel is the important factor for food processing system in this research. The purpose of this study is to research the behavior of the underwater shock wave in the enclosed vessel to investigate the influence of the contour of the elliptical vessel on the pressure. In this research, we used the elliptical shape for the vessel and the explosive was used to generate the shock wave. Numerical calculation was carried out by using LS-DYNA. The ratio of the length of the major axis to minor axis of the elliptical were changed, as a main parameter. As a result, it was found that underwater shock wave was generated and propageated in the elliptical vessel following the explosion. The underwater shock wave was coverged at the focal point. At the same time, the pressure was increased by the coverged underwater shock wave at the focal point in the all elliptical vessels. It was also found that the peak pressure at the focal point was determined by the contour of the elliptical vessel.