The Design of Rice Powder Production Vessel and the Pulverization of the Rice Using Numerical Simulation

In recent years, the food self-support rate of Japan is 40%, and this value is the lowest level of major advanced country. The stable supply of food is a big subject that Japan has. Therefore, rice powder attracts attention for improvement of the food self-support rate in Japan. Previously, the rice powder is produced by two methods. One is dry type, and the other is wet type. However, these systems have a fault of the heat damage of the starch and the consumption of a large quantity of water. In our laboratory, as solution of those problems, production of the rice powder by using the underwater shock wave is considered. Shock wave is the pressure wave which is over velocity of sound by discharging high energy in short time. Propagating shock wave in water is the underwater shock wave. This food processing using an underwater shock wave has little influence of heat and its processing time is very short, preventing the loss of nutrients. In this research optical observation experiment and the numerical simulation were performed using trial vessel, in order to understand the behavior of the underwater shock wave in the development of the rice powder production vessel using an underwater shock wave at the factory. In addition, in order to understand the rice powder production and to develop it, the numerical simulation about pulverization of rice is performed. By this method, the pressure which takes for rice at the time of pulverization, and its pulverization phenomenon are solved. Analysis soft LS-DYNA was used for these numerical simulations. The comparative study of the experiment and the numerical simulation was investigated. The behavior of the shock wave in the device and transformation of rice were able to be clarified.


INTRODUCTION
Various processing methods of using shock waves generated by explosive and electric power have been studied and developed.It is well established that shock wave pressure propagates on a large range and duration of pulse can be long, depending on the processing techniques.
Using water as the propagation medium, the influence of thermal effect can be minimized.Rice powder is produced using this advantage.
In this research, the purpose is the utilization of the rice powder manufacture using the shock wave.Therefore, it needs to understand the following points.At first, the device with the optimal form and strength to utilize the shock wave for the maximum is designed.And next, in order to produce rice powder efficiently, it is necessary to know the destructive phenomenon of rice and the influence of the shock wave on rice.However, a cost depends on an experiment, and the observation of the phenomenon is difficult.Therefore we used numerical simulation.In design of the device, a high speed camera was used for optical observation of shock waves.And numerical simulation was performed to investigate the validity of data, and these results were compared with experimental results.[1] Moreover, in order to know what kind of influence the observed shock wave will have on food processing, influence evaluation of the shock wave by the form of a device was performed.The simulation method using SPH is proposed about the pulverization phenomenon of rice.About a pulverization phenomenon of rice, two kinds of simulation method ware proposed.

THE DESIGN OF THE SHOCK WAVE PROCESSING DEVICE 2.1. EXPERIMENTAL METHOD AND NUMERICAL SIMULATION METHOD 2.1.1. Optical observation method and Experimental device
The optical observation that uses the shadowgraph method [2] was used to evaluate the shock wave propagating.The shadowgraph system used in this study is shown in Fig. 1.This system uses a technique, also called direct projective technique, in which the shadow of the light observed and projected by density change on a screen.The shadowgraph method used for visualization of a shock wave or the motion of a wave is a classical technique.
The shadowgraph system and a high-speed video camera (HPV-1:Shimadzu Corp.) were used to observe the underwater shock wave.The velocity of a shock wave is obtained by taking a framing photography using the shadowgraph method.The schematic illustration of an optical observation for the framing photography is shown in Fig. 2.
An experimental device is a rectangular container.The observation side of the device is PMMA, the side of the device is aluminum and the upper surface and the bottom of the device are PMMA.This container is separated into two parts by a phosphor bronze plate.0ne part is the shock wave generating container and the other is the food processing container.In order to generate a shock wave in the upper part of the device, the No.6 electric detonator (made by Kayaku Japan corporation) is set.The Design of Rice Powder Production Vessel and the Pulverization of the Rice Using Numerical Simulation Figure 1 Shadowgraph system for optical observation The inner volume of the shock wave generating container is 120mm ϫ 120mm ϫ 50mm and the size of the food processing container is 120mm ϫ 120mm ϫ 150mm.Water is poured into each.

Numerical Simulation Condition
The phenomenon for an explosion and the propagation of shock wave in the device are evaluated by means of LS-DYNA.Fig. 3 shows to the numerical simulation model of the device.This simulation model is two dimension model of one mesh in depth.And calculation method is used Lagrangian and Eulerian [3,4].The number of elements is 29820 (ϭ213 ϫ 140 ϫ 1).
High explosives SEP (made by Kayaku Japan corporation, detonation velocity about 6,800m/s, density 1310 kg/m 3 ) is detonated by using Initial detonation.Because the structure of the electric detonator is complex, SEP to which the parameter value is known instead of the electric detonator is used.The power of explosive SEP is coordinated to become at the same level as an electric detonator.We applied the constrained condition for the z axis so that a translational and rotational motion can not happen when explosion is occurred in explosive container.
The various conditions used for this numerical simulation are shown below.• Explosive SEP Jones-Wilkins-Lee (JWL) equation of state [5,6] for the explosive SEP is used.This equation is well used for the numerical simulation accompanied by a detonation phenomenon.JWL parameters are given in Table 1.Expression of JWL equation of state is described as follows: (1) V ϭ ρ 0 (Initial density of an explosive) /ρ (Density of detonation gas), P is Pressure, E is Specific internal energy, A, B, R 1 , R 2 , ω are JWL parameters.C is the intercept of the v s -v p curve, S 1 , S 2 and S 3 are the coefficients of the slope of the v sv p curve, γ 0 is the Gruneisen gamma, a is the first order volume correction to γ 0 , Gruneisen coefficients are given in Table 2. • NULL This material allows equations of state to be considered without computing deviatoric stress.Optionally, a viscosity can be defined.Also, erosion in tension and compression is possible.Material parameter of WATER for NULL is given in Table 3.

• Aluminum alloy
We applied SIMPLIFIED JOHNSON COOK for the material parameter of Aluminum alloy.This Johnson cook strain sensitive plasticity is used for problems where the strain rates vary over a large range.In this simplified model, thermal effects and damage are ignored.The value of AL6082-T6 is used as a value of the aluminum alloy this time.Material parameter of Aluminum ally for SIMPLIFIED JOHNSON COOK are given in Table 4. Expression of SIMPLIFIED JOHNSON COOK is described as follows: ( A, B, C and n are constants._ ε p ϭeffective plastic strain.effective strain rate for ε .Other condition of numerical simulation is shown in Table 6. ( )

THE COMPARISON OF EXPERIMENTAL RESULTS AND SIMULATION RESULTS [1]
The framing photographs showing the behavior of the shock wave which propagates the inside of a processing device were obtained by optical observation using the high-speed video camera.The framing photographs are shown in Fig. 4. First, the shock wave with detonation velocity of No.6 electric detonator propagates into the water and the shock wave passes through the phosphor bronze plate at 5µs can be confirmed.The precursor shock wave generated by the shock wave propagated from the phosphor bronze plate to the aluminum sidewall can be confirmed at 20µs.It is understood that the precursor shock wave propagate from the phosphor bronze because the shock wave propagated from a lower wall before the shock wave reaches the upper wall.In the photograph of 35µs, the reflected wave that the shock wave that propagates by passing the phosphor bronze plate reflects to the sidewall was able to be observed.In addition, the height of the whole device is 213mm, but the distance from the phosphor bronze plate in the observation part is about 95mm at the maximum to observe the processing container part in the experiment.The pressure distribution of the precursor shock wave and the shock wave passes through the phosphor bronze plate that obtained by numerical simulation is shown in Fig. 5.These photographs show that Explosive SEP explodes and shock wave propagates.The precursor shock wave propagates from the aluminum sidewall into water.Fig. 6 has changed the pressure representation at the time of 60µs compared with Fig. 7.The reflected shock wave that the shock wave that propagates by passing the phosphor bronze plate reflects to the sidewall was able to be observed.
What measured the velocity of precursor shock wave, shock wave passes through the phosphor bronze plate (Henceforth, this is called Shock wave) and shock wave reflected in the side wall is shown in Fig. 7, Fig. 8, and Fig. 9.
In these results, since there is the same tendency as an experiment and numerical analysis in each shock wave, it can be considered that this numerical analysis is effective as the evaluation method.

Evaluation of the device form
The optimal form of a device is considered, because effectiveness was shown in the device design using numerical simulation.In this case, numerical simulation is performed in order to investigate what kind of influence a shock wave has on food processing, and the device where the shock wave acts easily is designed.
In this paragraph, the numerical simulation shown in Fig. 10, 11, 13, 15, 17 was performed.The pressure in Fig. 10 and other figures is measured, and a result is shown in Fig. 12, 14, 16, 18. Pressure was measured at a 30mm point from the phosphor bronze plate in the center of a processing container.This point is a place to put food.Moreover, all the results are compared and it is shown in Fig. 19.The figure is explained here.Fig. 10 is the model that SEP detonates in underwater, in order to consider the validity of equipment.Fig. 11 shows the same model as what was used in the experiment.Fig. 13 is the model that the aluminum side wall of the food processing container of figure 11 was removed.In consideration of reflection on the boundary, the water part is larger than Fig. 11.Furthermore, as for Fig. 15, the aluminum side wall of a shock wave generating container is also removed.Fig. 17 is the model which removed the phosphor bronze plate from the equipment used for the experiment.Two peaks were observed by the pressure value in simulation.Each peak is called the first shock wave and the second shock wave.Each consideration is shown below.• The First Shock wave The first shock wave was observed in all results.This shock wave was generated when SEP detonated.
The maximum pressure of the first shock wave in Fig. 10 is about 380 MPa.This value is about two times of Fig. 12, 14, 16 and the same level in fig.18.In Fig. 12, 14, 16, pressure became about half compared with the case of only water and the difference was in the time which measured pressure.It is thought that this is caused by attenuation of the pressure, when the shock wave passed the phosphor bronze plate which is a partition of a shock wave generating part and a food processing part.It is clear also from the result of Fig. 18 that there is not phosphor bronze plate.
• The Second Shock wave The second shock wave was observed in all results except for Fig. 16.It is thought that this shock wave observed the first shock wave reflected in the aluminum side wall (reflective shock wave).This is clear also from not observing the second shock wave in the model of Fig. 10 and Fig. 15 that is a model without the aluminum side wall.The maximum pressure of the second shock wave is about 210 MPa in Fig. 12, is about 320 MPa in Fig. 14, and is about 100 MPa and in Fig. 18.In Fig. 12, it is thought that the first shock wave reflected in the aluminum side wall of a food processing part was observed.In Fig. 14, it is thought that the shock wave reflected in the aluminum side wall of a shock wave generating part was observed.Also in Fig. 12, since the minor change occurred in the attenuation tendency of pressure in about 70µs, it is thought that the shock wave reflected in the aluminum side wall of the generating part was observed.The reflective shock wave can be observed twice in Fig. 18.In Fig. 18, as the reason that the pressure of the second shock wave is big compared with other case, it is thought that there is no attenuation of pressure with the phosphor bronze plate, as well as the first shock wave.
It is effective to make a shock wave act many times, when performing food processing using a shock wave.Therefore it is thought that it is necessary to have the following form as a processor.
• The first shock wave spreads in a food processing part without decreasing as much as possible • The second shock wave (reflective wave) acts on the food processing part efficiently by high pressure Although the phosphor bronze plate was used in order to protect food from pollution of the water which can occur on the shock wave generating part, it is necessary to think about the necessity of the plate when considering the form of the device.

THE PROPOSAL OF THE TECHNIQUE IN REAPPEARANCE OF THE PULVERIZATION PHENOMENON OF RICE
Now, the numerical simulation of the pulverization phenomenon by the shock wave of rice is not known.Therefore it proposes using the numerical analysis using the following techniques as reappearance of the pulverization phenomenon of rice.

Numerical Simulation Condition of Type 1
Fig. 20 shows the numerical simulation model of the rice.This simulation model is three dimensional model and depth is four meshes.And calculation method is used Lagrangian and Eulerian like 2.2.1.The number of elements is 45077.SEP and WATER are the same as 2.2.1.Therefore only rice is described.The various conditions used for this numerical simulation are shown below.

• Rice
We applied GRUNEISEN equation of state and ELASTIC PLASTIC HYDRO for the material parameter of rice.Since GRUNEISEN is described in 2.2.1,only the parameter of rice is described to Table 7 and explanation describes only ELASTIC PLASTIC HYDRO.In addition, since the exact parameter of rice was unknown, the value of carbon was used.8.

Figure 2 Figure 3
Figure 2 Schematic illustration of an optical observation for the framing photography

Fig. 6
Fig.6 Framing photographs of underwater shock wave

Figure 4 Figure 5 Figure 6
Figure 4 Framing photographs of underwater shock wave

Figure 7 Figure 8
Figure 7 Comparison of velocity of precursor shock wave

70Figure 9
Figure 9 Comparison of velocity of reflective wave

Figure 11 Figure 12
Figure 11 Simulation model of the experimental device

Figure 13 Figure 14
Figure 13 Simulation model of the device without the side wall

Figure 15 Figure 16
Figure 15 Simulation model of only the Phosphor Bronze Plate

Figure 17 Figure 18
Figure 17 Simulation model of the device without the PB plate

Figure 19
Figure 19 The pressure comparison of all results

Table 1
(2)ATERWe applied GRUNEISEN equation of state and NULL for the material parameter of water.•GRUNEISENequation of state This equation of state with cubic shock velocity-particle velocity defines pressure for compressed material as(2)

Table 2
Parameter of Gruneisen equation of state of WATER

Table 4 SIMPLIFIED
JOHNSON COOK parameters of AL6082-T6 • Phosphor bronze, PMMAWe applied PLASTIC KINEMATIC for the material parameter of Phosphor bronze and PMMA.This model is suited to model isotropic and kinematic hardening plasticity with option of including rate effects.Material parameter of Phosphor bronze and PMMA for PLASTIC KINEMATIC are given in Table5.

Table 5
Material parameters of phosphor bronze and PMMA mechanism for modeling Fluid-Structure Interaction (FSI).The structure can be constructed from Lagrangian shell and/or solid entities.The multi-material fluids are modeled by ALE formulation.

Table 6
Condition of Numerical calculation analysis

Table 7
Parameter of Gruneisen equation of state of Rice 74 The Design of Rice Powder Production Vessel and the Pulverization of the Rice Using Numerical Simulation

Table 8
ELASTIC PLASTIC HYDRO parameter of Rice