This paper presents a study on a structural modification focused on transfer characteristics of structures for vibration transmission acceleration using an acoustic guitar. Inverse transfer path analysis (TPA) and statistical energy analysis (SEA) were used to evaluate the transfer characteristics of vibration experimentally. The squared sound pressure levels were measured before and after the implementation of the structural modification focused on the fundamental tone of E2 by adding the sound post between boards like violin in order to confirm the increase of the amount of radiated sound. As a result, structural modification by each methods is effective.
Heat seal is a kind of welding technique for thermoplastic resin films. The technique is used to make soft hermetic bags for foods and medicines. Delamination and a pinhole in the bags must be detected before shipment even if the size of the defects is microscale. We propose a new non-contact inspection method for the heat sealed soft bags using air-coupled ultrasound. In this method, ultrasonic waves are obliquely incident on the heat sealed portion to generate coincidence effect, and transmitted wave is observed. The coincidence effects is used to magnify the effect of the small defects in the transmitted wave. This paper focuses on sensitivity of the method when two kinds of frequency of the ultrasonic wave, 640 kHz and 1.5 MHz, are applied. Through experiments using heat sealed film samples, it was found that the ultrasonic wave with 640 kHz frequency is more suitable for the proposed method.
This study is intended to evaluate levitation and rotation characteristics of magnetic bearings with superconducting coil for a pump of liquid nitrogen. And since persistent current for bias current will be available in the near future, energy saving and high stiffness magnetic bearing will be realized.
When synchronization occurs in a system where several nonlinear self-excited oscillators with different natural frequencies are coupled, the frequencies of all the oscillators are entrained due to the interaction. While to date many researchers have examined characteristics of this phenomenon, its mechanism has not been completely clarified. In order to provide new insights into the mechanism, this paper considers a system consisting of two DC motors and analyzes the energy condition which needs to be satisfied in a synchronized state. It is seen that the derived condition is able to predict the range of synchronized frequency and the applied voltage where synchronization occurs.
This paper describes the particle vibration damper design, based on experiments using multiple unit capsule-dampers in place of cavities inside SDOF structure. The interplay of various parameters such as mass ratio, percentage volume fill, particle size, intensity of excitation, number of capsules were investigated with eight different particle damping configurations loaded up to 0.18 intensity of vertical excitation. Experimental testing shows that if a given single-unit particle damper is replaced by two or more units of equivalent total mass in capsules operating in parallel; the new capsule system retains much the same effectiveness in regard to vibration amplitude reduction, while the percentage volume fill can have significant effect on the damping at high excitations.
In the present situation when the importance of logistics is expanding, the automation of overhead cranes is strongly desired. The automation needs the method which is able to handle both vibration control and obstacle avoidance. In order to meet this demand, the authors proposed a systematic method for designing path of the trolley whereby the trolley and the cargo are both able to avoid obstacles while minimizing the path as well as keeping the residual vibration suppressed. In this paper, the effectiveness of the proposed method is examined by experiment.
In recent years, liquefied natural gas and liquid hydrogen have attracted attention as an alternative energy to petroleum. Since these liquids are subject to cryogenic and high pressure gas safety laws, pumps handling them are required to be low temperature resistant bearings and sealed structures. In this research, we developed a submerged pump using a single - axis control bearingless motor to deal with these problems. The presentation will show the stability and pump characteristics of the rotor during pump operation in liquid nitrogen.
In this paper, the use of MR brakes as a driving device for safety control of human-collaborative robots is proposed. The MR brake is operated on MR fluid (magneto-rheological fluid) and electromagnet, it is a device with excellent responsiveness. Using the MR brakes as the power plant of a rotary actuator, several experiments controlling the rotation of shafts generated by a motor fitted with the MR brakes are conducted. From the result, we verify the control performance of the MR brakes, and describe the application of the MR brakes to safe control of human-collaborative robots.
The conventional multi-channel active control of an incident noise passing through an open window will increase the computational burden of the control algorithm and the complexity of the hardware configuration as more control channels are used. To overcome these problems, active noise control based on wavefront synthesis is proposed. The approach is a global ANC divided into two sub-systems. The one sub-system is to reproduce the shape of the wavefront of the incident noise, and the other is to adjust the amplitude and phase of the reproduced sound to be the anti-noise by using single channel filtered-x LMS ANC. By dividing into the sub-systems, the control algorithm and the hardware configuration can be simpler than the conventional multi-channel ANC. In this paper, the effectiveness of the proposed approach is verified by numerical simulation with 2-D boundary element method.
Isothermal model of a Stirling engine using bellows instead of power piston is proposed, and governing equations for a dynamic analysis of planar four-bar mechanism are described. Both of the isothermal model analysis and the dynamic analysis can be carried out by a spreadsheet program such as Microsoft Excel. In case of the isothermal model of a SE using bellows, a volume of the bellows affected by not only the phase angle of a mechanism but also relation between the working fluid pressure and a buffer pressure, which is atmospheric pressure in most of miniature Stirling engine. In terms of the dynamic analysis, the governing equations of coupler link in a four-revolute chain are described. In the analysis, both the acceleration caused by the motion and a gravitational force are considered. Each of the governing equations can be explained by the dynamics that a student studies in the first year of mechanical engineering course.
This paper proposes an application of the shooting method to determine values of parameters of the driving mechanism using swing motion so that it reaches a target position at a designated time. The system comprises a body and a rod which have two and one freely rotating wheels, respectively. The numerical simulation is carried out to demonstrate the effectiveness of the proposed method.
Acoustic material is used to reduce noise in various places. But, it has low effect in low frequency range. Moreover, large amounts of acoustic materials increase undesirable losses. To solve these problem, we have suggested a method of installing acoustic material by providing air layer in one-dimensional cylindrical tube system. We calculate transmission loss in order to show the difference depending on the presence or absence of air layer. In addition, we calculate frequency at which transmission loss increases by calculating sound pressure amplitude in air layer. We confirm the effect of air layer by experiment using sound tube. It show that the method can be used actually. In case of using same length of acoustic material, multiple air layers provide higher effect than single air layer in experiment. Therefore, the method can be used more effectively by setting acoustic materials so that the number of air layers increases.
Arteriosclerosis causes myocardial infraction and cerebral infraction. However, it is difficult to know extent of its progress before it causes diseases. In order to overcome this problem, we consider a possibility of identification of stiffness of a blood vessel by using automatic sphygmomanometer. To identify stiffness of a blood vessel, we use a concentrated mass model to analyze a pulse wave. We confirm the validity of this model by an experiment with a silicon tube simulated a blood vessel. Results of this model agree well with the experimental results. Furthermore, we consider a possibility of identification of stiffness of a silicon tube by using this model.
When a non-handicapped person communicates with a handicapped person, a healthy person often feels difficult to understand non-verbal signs which are shown by a handicapped person. Because someone of handicapped persons always does overreaction, and another person keeps silence. In these situations, a non-handicapped person tries to understand them with the knowledge which has been got through communication with non-handicapped persons, but it often fails. These situations give some kind of stress to healthy persons, and they come to avoid communication. We are developing the communication support system to understand non-verbal signs which are unique to handicapped persons. First of all, we have studied an appropriate method to display information which supports to understand the meaning of non-verbal signs with knowledge of ergonomics. In this paper, we improved the display method to show information on a wearable monitor and did some communication experiments to examine the effectiveness of the system. By showing the meaning of signs of a handicapped person on a monitor in a real time, a non-handicapped person can understand the situation of communication and what a handicapped person is going to tell.
In this paper, the performance evaluation of developed in-situ apparatus for real-time observation were studied. The apparatus could observe the nanoparticles phenomena on surface between substrate and polishing pad that is essential to improve the Material Removal Rate (MRR) of the substrate during Chemical Mechanical Polishing (CMP) process. We propose the single wavelength by applying an evanescent field in order to observe the nanoparticles phenomena. The experimental condition were separated into two experiments, as different size (sub 10 nm and 105 nm) silica slurry ( 5 wt% with pH 10.5) with pure water (pH 10.5). According to the experimental result, the our apparatus could detect the scattering light intensity of pure water and silica slurry during polishing process. The silica slurry are higher scattering light intensity than pure water, and sub 10 nm silica slurry is highest intensity.
Square layout four-point method with angle correction has been proposed as an on-machine profile measurement method of machined flat surfaces. In this method, it is possible to measure the planar shape without the influence of translational error, pitching, and rolling of a stage. However, a zero-adjustment error, which is a deviation of the origin height of the four displacement sensors, causes a large form error of twist shape when the planar shape is reconstructed. To solve this problem, a back calculation method of the zero-adjustment error was proposed: which calculate zero-adjustment error from the difference in the error cumulative amount of two different calculation paths for a square measurement region, the raster scanning path and the diagonal path. To improve the calculation accuracy of zero-adjustment error, the authors have proposed to apply two-point method with angle correction to the diagonal direction by measuring the posture change of the stage unit with the angle sensor newly added in the diagonal direction. Monte Carlo simulations of the square layout four-point method and back calculation of zero-adjustment error were carried out. As a result, it was confirmed that the proposed method is effective to improve correction accuracy of the zero-adjustment error.
In the 5-point method, the straight profile measurement of one line is performed using the sequential three point method, and the relation between the lines is simultaneously measured by two sensors arranged on the next scan line. Using this relation, straightness measurement results of each line, which is acquired by the three-point method, are connected to obtain a planar shape. In order to realize the on-machine measurement by this principle, the authors have prototyped a 5-point MEMS displacement sensor device for measuring a planar shape with five cantilever displacement sensors in a 20 mm square silicon wafer. Each displacement sensor has a probe of a quadrilateral frustum with a height of 250 μm at the tip of the cantilever and detects the strain generated at the root portion as a resistance value change of the piezo resistor according to the displacement. With bulk silicon wafers, when fabricating a probe by etching, they were difficult to control the thickness of the cantilever after etching and the height of the probe according to the target values. Therefore, the authors adopted the Silicon-on-insulator (SOI) wafer to improve dimensional accuracy by using etching stopped at the SiO2 layer. With the fabrication process adopting the SOI wafer, variations in height of the probe are reduced compared with conventional fabrication process using bulk silicon wafer and the size of the tip of the probe can be controlled independently. Therefore, efficiency of fabrication process using the SOI wafer is confirmed.
We propose a simple method of retrofitting common rail system to old diesel engine. Produce a boss connecting the injector and solenoid injector of 1DZ made by TOYOTA INDUSTRIES CORPORATION which is the testing institution of DENSO DCA - 25SPTH generator Process information from various sensors and send output signals to injector and tap supply pump to control injection quantity, injection time, injection rate and injection pressure. If changing from normal to common rail, NOx concentration decreased by about 51.3%. In addition, the NOx concentration was reduced by about 68.4% by multistage injection. Fuel efficiency improved by about 7.4% for single stage injection and about 8.4% for multistage injection. As experimental results, it was confirmed that the condition with the common rail system fitted reduced the NOx concentration. This is because the fuel is sprayed in the form of finer atomized fuel, it is inferred that this is a result that the common rail system was successfully retrofitted to the diesel engine of the generator. Because of the improved fuel economy, the technology of reducing the environmental load other than the common rail system. It is expected that environmental regulation can be cleared by using it.
Homogeneous Charge Compression Ignition (HCCI) combustion has advantages of high thermal efficiency and low pollutive emissions, while it has a disadvantage in controlling ignition timing. In order to solve this problem, Pulsed Flame Jet (PFJ) and Exhaust Gas Recirculation (EGR) were employed in Rapid Compression Expansion Machine (RCEM). PFJ is the jet of burning gas issuing from a small cavity facing a combustion chamber. It is expected to advance autoignition timing. In addition, EGR leads to the retard of autoignition timing. Therefore, the optimization of ignition timing by PFJ were attempted under EGR conditions. RCEM realizes single compression and expansion strokes and thus the measurement of indicated work. EGR rate was varied between 0 % and 40 %, while the amount of fuel was fixed. Without PFJ, higher EGR rate led to the retard of autoignition timing and thus to lower knock intensity. With PFJ, indicated work under EGR conditions was improved by optimizing the timing of spark discharge of PFJ.
Regulations on exhaust emissions from diesel engines have become hardness, because they have a great influence on the environment. PM concentration can reduce by improve combustion, but weight concentration of PM is decreased, it may increase number concentration of PM. Therefore, in this study, we are reduced about number concentration of PM by gas mixture fuel and corona discharge into the intake air. Corona discharge is generated ozone at the same time of discharge, and takes in ozone (OH radical) into the intake air. Gas mixture fuel can be premixed fuel and air to expand at the same time of combustion, so we can be expected improvement of combustion.
Detonation is a type of premixed combustion, which propagates interacting with shock waves and combustion flames at supersonic speed. It is known in the early researches that DDT (Deflagration to Detonation Transition) in a channel is promoted by installing obstacles. This research investigates flame propagation and local explosions in channels filled with hydrogen/oxygen stoichiometric mixture and installed ten obstacles by using the two-dimensional simulation with a detailed reaction model. Furthermore, we estimate differences between the three-dimensional experiments performed in a past study and the present two-dimensional simulations. The simulations performed by changing the scale of the channel, grid width, and obstacle height. As a result, the flames did not transit to detonation under any conditions of the obstacle heights and channel sizes, unlike the experiments. Higher obstacles disturbed the flame propagation and induced the shock waves crossing the channel, which lead to the enhancement and acceleration of the combustion reaction. A small local explosion was observed near the eighth obstacle at one-tenth the size. The flame acceleration was faster in the experiment than in the numerical analysis.
UFB water has various effects by gas and mixing sise,and development is done in various fields. However, study applied through UFB water has a lot of reports, but it is the present conditions that the property is still unknown. It is important how to make UFB high concentration and control．The effect of gas depends on the number concentration of air bubbles in a liquid．Because solubility varies according to kind and temperature of gas, high concentration must overcome influence by the temperature in aiming at becoming it．I focused on CO2 UFB water in this study and inspected the influence on number concentration of temperature by the change．Because temperature decreased, the Nano number concentration of CO2 UFB water, TDS concentration is improved．Because temperature is decrease, pH is, and it may be said that TDC concentration can be improved.
As a substitute for diesel fuel, there is an increasing demand for BDF recicling waste food oil and palm oil with high production as plant oil. Since the food oil is a plant fuel, the viscosity is high and combustion is not better, so that the PM concentraion is increased. This study aims at improve combustion and reducing PM concentraion by converting food oil into water emulsified fuel. The water emulsified fuel is expected improve combustion by premixing air and fuel by expanded surrounding air, because it made steam by water into water emulsified fuel. Moreover, it is expected that clogging of the filter and PM can also be improved because it can eliminate impurities in the fuel by refining it, which is a problem of plant fuel.
Palm oil is raw materials such as margarine and soap, and it is used as a fuel for biodiesel engines and thermal power generation. However, since it has high viscosity and hardness at low temperature, it is difficult to be combustion, dispersion of products in the production process is large and combustion tends to deteriorate. It also contributes to the emission of CO2 from peat soil. Therefore, in this study, it is expected by improve premixing air and fuel accompanying the expansion of the gas simultaneously with the decomposition of the impurities in the fuel oil by using gas mixture mixed fuel mixed with air into the palm oil, it expects to improve combustion.
We constructed the newly soot prediction model, PS3-SM, which describes the process of PAH growth up to about 60 carbons in three sections and can predict soot production by combining with the method of moments. This model was combined with the gas phase reaction model of Miyoshi et al. which is a model for gasoline surrogate fuel including the growth process up to benzene and toluene. In this study, we improved the model under oxygen coexistence condition. As a result of model adjustments and verifications using the experimental results for a gasoline surrogate fuel measured by shock tube, it was found that the basic bell characteristics, the soot yield peak temperature and the trend of peak shift with increase of oxygen content can be reproduced well.
The prechamber combustion characteristics were studied using a rapid compression and expansion machine (RCEM) to improve the efficiency of cogeneration natural gas engines. The torch flames generated by a prechamber were used to investigate the effect that a prechamber has on the main combustion. In our previous study, we observed the correlation between the torch flame and the main flame (which is a so-called “prechamber combustion”) as well as the knocking phenomena for various prechamber configurations. In this study, we have investigated the effect of prechamber combustion on main chamber combustion characteristics using a constant volume combustion chamber.
The prechamber combustion characteristics were studied using a rapid compression and expansion machine (RCEM) to improve the efficiency of cogeneration natural gas engines. The torch flames generated by a prechamber were used to investigate the effect that a prechamber has on the main combustion. In our previous study, we observed the correlation between the torch flame and the main flame (which is a so-called “prechamber combustion”) as well as the knocking phenomena for various prechamber configurations. In this study, in order to investigate the effects of engine size on prechamber combustion characteristics, large size RCEM were developed.
In this study, laminar burning velocity and lean limit were measured for various hydrocarbon fuels using a co nstant volume combustor. Laminar combustion properties for four kinds of fuels, such as C8H18, S5H(C8H18+C 7H16+C7H14+C8H16+C7H8)，S5H+Furan(C4H4O), and S5H+Furan+NitroMethane(CH3NO2) were evaluated. As resu lts, it was found that the effect of furan on the lean limit was greater than the effect on the laminar burning velocity.
Wettability on structured surfaces is gaining remarkable interest for a wide range of applications. In this study, the partial wetting model has been derived theoretically based on the energy minimization method. The intermediate wetting state between Wenzel model for a fully wetting state and Cassie-Baxter model for a completely non-wetting state on structured surface is under consideration. We adopt the surface energy minimization for the total surface energy in the intermediate wetting state and derived an equation using a parameter defined as the effective wetting ratio to interpret the partial wetting. Good agreements between the theoretical prediction and experimental results have been confirmed to explain the partial wetting at the nano/microstructured surfaces.
We have developed a micro heat flux sensor for measuring boiling heat transfer at high-resolution. The heat flux sensor consists of two thin film resistance temperature detectors (RTDs) stacked in the substrate thickness direction. The heat flux can be calculated through the one-dimensional transient heat conduction calculation using measured two temperatures. Two kinds of experiments as preliminary test were conducted. First one is the local heat flux measurement during liquid droplet contact on the sensor substrate. The sensor successfully detected a huge heat transfer of over 3MW/m2 with a quick temperature change of ~105K/s just after droplet contact. And another is measurement of the local heat flux beneath a single pool boiling bubble. The heat flux over 1 MW/m2 induced by microlayer evaporation was measured under a bubble. The developed sensor was confirmed to be useful for the measurement of fast and local heat transfer phenomena.
Enahancement of critical heat flux (CHF) is important for cooling electronic devices with a high heat generation rate. In pool boiling, the downward liquid flow to the heating surface is interrupted by the strong upward vapor flow, regarded as hydrodynamic liquid-choking limit, triggers CHF phenomenon. We have been researching a new technique in order to enhance CHF where the paths of the liquid and vapor flows can be separated to overcome the hydrodynamic liquid-choking limit. The three-dimensional porous structure was fabricated by sintering of copper particles. It was confirmed that the generated vapor was successfully vented from the side of the structure as we aimed. The maximum critical heat flux is 2.9 MW/m2 that is 2.4 times larger than the CHF on a copper flat surface.
Bubble nucleation on a solid surface was simulated using the molecular dynamics method. Liquid argon between parallel solid walls was heated using spot heating method or uniform heating method from one of the walls. The hot spot or the hydrophobic spot was used to simulate the cavity as the nucleation sites on solid surfaces. With a visualization of the density profiles in 2-D images, the onset of nucleation bubble, leading to the nucleation was investigated for different heating method and different wettability of the cavity-like spot at the solid surface. The effect of the cavity-like spot width and its wettability on the initial nucleation and bubble growth is discussed.
We observed stable nanobubbles both in bulk ultra-pure water and at Si-water interface using scanning confocal laser microscope. Since the thermal properties of nanobubble liquid are unknown so far, the specific heat capacity of nanobubble liquid is measured using the differential scanning calorimetry. We found that the heating rate, the mass of sample and the reference are important to obtain the accurate specific heat capacity of liquid. As a result, the specific heat of nanobubble liquid is obtained, showing lower value than that of the base liquid without nanobubble.
The high-quality and high-efficient drying technique is important in the field of food-processing. The purpose of this study is to clarify the mechanism of moisture transport and shrinkage phenomena in the drying of root vegetables. We use two kinds of drying methods, the micro vacuum drying and the warm air drying. Experimental study was made with the Japanese radish, the carrot and the potato. It is confirmed that the shrinkage rate increases during the falling-rate period in both drying methods. It is also found that the central part of potato has a possibility to cause a glass-transition due to lower moisture content in the micro vacuum drying. This may be a reason for that a shrinkage is suppressed in the potato.
We measured thermal boundary resistance at organic-inorganic interface to calculate the effective thermal conductivity by changing the thickness of both PEDOT:PSS and Bismuth Telluride in multi-layered thin films system. The total thermal resistance of the films as a function of thickness were measured by using a differential 3ω method. Thermal boundary resistance was calculated from the measured thermal resistance of the films at nonzero intercept. The measured PEDOT:PSS-Bismuth Telluride thermal boundary resistance was 1.4±0.3×10-7( m2·K ) / W. The measured high thermal boundary resistance can explain the low value of effective thermal conductivity of organic-inorganic composite film.
Thermal conductivity of a thin film decreases due to the strong phonon scattering at the film surface with decreasing the film thickness. However, it is shown theoretically that the thermal conductivity of a thin film with several tens nano-meter thickness can be increased due to the Surface Phonon-Polaritons (SPhPs) effects. SPhPs are surface evanescent electromagnetic waves resulting from the coupling between optical phonons and photons. In this regard, silicon dioxide films are made by thermal oxidization to have high density films compared to those grown by other methods. Further, standard micro-fabrication processes were used to fabricate suspended thin film for thermal conductivity measurement by steady state method and diffusivity by 3ω method. We also measured temperature dependence of thermal conductivity of 50 and 200 nm thick suspended thin films from 300 K to 370 K. Experimental results is comparable with analytical thermal conductivity enhanced due to surface phonon-polaritons. Result shows that the thermal transport in suspended thin films was increased with decreasing the film thickness while it increased with increasing the temperature.
In this study, we investigate thermal conductance switching characteristics using liquid metal gallium indium eutectic alloy. Gallium indium eutectic alloy was fabricated by mixing gallium and indium. Liquid metal is poured into the micro channel saturated with electrolyte aqueous solution which is driven by applying electric field and known as electrowetting. The filling rate of liquid metal in the action part can control thermal conductance. Thermal switching using electrowetting process shows that the highest value of thermal conductance ratio was about 1.6 for our liquid metal. In the future, we will be developing high efficient device using MEMS technique.
In recent years, Power to Gas technology converting electric power from renewable energy such as solar and wind powers to fuel for energy storage and transport has attracted attention. Promising methods include steam electrolysis and co-electrolysis using the Solid Oxide Electrolysis Cell (SOEC). We have developed a honeycomb electrolytic cell with a larger reactive area per unit volume than conventional flat and tubular types. Thereby the fuel production rate per unit volume can be greatly improved. In this study, we address hydrogen production by steam electrolysis with an SOEC having a porous honeycomb support consisting of Ni-YSZ cathode.
One of the promising ways to remove space debris is to attach an electrodynamic tether (EDT) to debris by shooting a harpoon from an active debris removal satellite. There is a possibility for the harpoon to be removed from the surface of debris because of the tensile load of the EDT. The purpose of this research is to evaluate the pull-out force in a novel harpoon designed for the debris capturing system. This new harpoon with a barb is composed of an inner harpoon and an outer harpoon. After the penetration, the outer harpoon is deformed by the inner harpoon and so creates a barb on the tip. Harpoon shooting tests were conducted using a debris capture gun in order to study the impact of the harpoon into the aluminum alloy plate. After firing tests, pull-out tests were conducted by the universal tensile testing machine. During these tests, the harpoon was deformed after the penetration and opened a barb on the tip so the function of barb system could be confirmed. Moreover, the maximum pull-out load the harpoon can handle without being separated from the plate is measured. For some harpoons with the barb system, pull-out load was superior to the non-barb systems. In this way, the efficiency of this design of harpoon is proved, with a maximum loading of 7000 to 16000 N.
Near Earth Objects (NEOs) are asteroids and comets which come close to Earth’s orbit each year. So there is a high possibility of impacts for example, in February 2013, an asteroid created an airburst near Chelyabinsk State in Russia, causing an estimated damage of approximately 33M$ and injuring an estimated damage of approximately 1500 people. To avoid asteroid impacts it is necessary to change NEO’s orbit. Impacting at a hypervelocity is one of the methods that we consider to change NEO’s orbits. Hypervelocity impacts intend to change the orbit by making a spacecraft impacts on the NEO. In our study we examined the orbit change induced by hypervelocity impacts and explosives to further improve the effect. The influence on the orbit by explosives depends on the shape of the crater created by an impactor. Thus we will optimize its shape by making impact tests with a Two Stage Light Gas Gun in order to accelerate impactors with different shapes. As a result, we analyzed of the influence by explosive with AUTODYN from the shape of craters obtained by the experiment and we found that the shape of crater has an optimum condition.
For further development of space development, reduction of space transportation cost is an important theme. Particularly, it is essential to reduce the weight of the propellant tank made of aluminum alloy, which occupies most of the mass of the airframe structure. In recent years, composite materials composed of carbon fiber reinforced plastics (CFRP: Carbon Fiber Reinforced Plastics) with high specific strength and lightweight are widely used in the aviation industry. However, in rockets, liquid oxygen (LOX) is often used as an oxidizing agent, and in the LOX environment, CFRP may ignite by triggering external factors such as impact and friction. Therefore, it is necessary to use a material that does not have ignitability in the portion that contacts LOX and oxygen gas. In this study, the prototype fabrication the oxygen tank liner using liquid oxygen-compatible carbon fiber reinforced thermoplastic resin (CFRTP: Carbon Fiber Reinforced Thermo Plastics). is conducted. In addition, the airtightness between the cap part and the liner, where is considered to have high risk of leakage of the propellant, is tested.
At present, Space debris have a lot of problems in the space industry. They are the crush to spacecrafts and making the restriction of orbit in space. ISO 112227 was enacted in 2012 as a measure against microscopic secondary Space debris called Ejecta among space debris. However, this protocol did not take into account oblique impacts of projectiles, and a draft revision is made for the purpose of implementing oblique impact experiments. In this research, as a verification of the revision proposal, a 1 mm diameter projectile simulating micro debris is collided with a two-stage light gas gun at a speed of 5 km.s-1 using a target of A2024-T3, usually used as a spacecraft material. The impact angles are 0 (vertical impact), 45, 60 and 75 degrees. About the evaluation method, it is based on the generation amount of Ejecta and its distribution throughout impact marks. Since the target is a ductile body, the amount of Ejecta generated is small, and so it is difficult to calculate accurate ejecta mass at 60 and 75 degrees. Since the angle also increases the distribution of impact marks, scavenging of Ejecta is insufficient. In order to solve this problem, the way of collecting Ejecta is reviewed in oblique impact experiments.
During the re-entry flight regime of reusable space transportation vehicles, due to the aerodynamic heating, it is difficult to estimate the air data parameters (airspeed, aerodynamic attitude etc.) accurately using conventional ADS (Air Data Sensing) system with a sharp shaped pitot tube. In addition, this conventional system is not redundant, because such system doesn’t have fault tolerance capability. Therefore, fault tolerant Flush-type ADS (FADS) system had been devised in previous researches. In the present research, the FADS system that has higher redundancy than the conventional system by increasing the number of pressure holes is studied in order to apply to WIRES (WInged REusable Sounding) rocket developed by Space Systems Laboratory of Kyushu Institute of Technology. The air data estimation algorithm is developed based on the calibration performed by the wind tunnel test data, and the estimation accuracy is evaluated. As a result, accuracy of the estimated side slip angle deteriorated compared to the estimated angle of attack. Additionally, the shape and compressibility parameter is depended on Mach number and Angle of attack.
In order to evaluate a performance of a propeller in Martian atmosphere, the experimental devices are set up in a low speed wind tunnel. First, the validity of the experiment is checked with an off-the-shelf propeller. Then, the experiments are done for the specially designed propeller for the test. The results show that the efficiency is lower than that as designed. The reason of the large discrepancy is due to the higher drag coefficient than the estimation. The section shape with lower thickness and camber should lead to the higher efficieny.
In recent years, Kyushu Institute of Technology has been studying and developing experimental winged rocket to validate the necessary technology for the suborbital reusable transportation system. For the development of the suborbital winged rocket, it is necessary to solve the coupled design problem of the vehicle shape and flight trajectory. This means that the shape of the vehicle must be optimized while carrying out aerodynamic analysis and flight trajectory calculation in a wide range of flight conditions such as powered ascent, high angle-of-attack re-entry, gliding, and landing phases. Therefore, the application of efficient three-dimensional shape definition method and low-cost aerodynamic analysis method are essential. In this research, OpenVSP, an open source software for the parametric modeling of aircraft airframe is used for the design of the vehicle shape, and low-fidelity Computational Fluid Dynamics (CFD) calculation based on panel methods is used. The aerodynamic characteristics obtained from the low-fidelity CFD are compared with the wind tunnel test results, and the satisfactory accuracy of the low-fidelity CFD is revealed. The comparison is performed from subsonic to hypersonic speed regime, and the control surface deflection is also considered. Furthermore, high-fidelity Navier-Stokes CFD calculations is conducted as a preliminary study for accuracy improvement of aerodynamic analysis.
Kyushu Institute of Technology has been developing experimental winged rocket for fully reusable space transportation system since 2005. For the conceptual design of the suborbital winged rocket, it is necessary to solve the coupled design problem of the vehicle sizing and flight trajectory. Therefore, multidisciplinary design optimization for the system composed of several design disciplines using an efficient gradient-based optimizer is useful. Using the gradient-based method, however, the converged solution and the computation time highly depend on the initial solution supplied by the user, and its appropriate design requires experiences. In this paper, a methodology for automatically generating initial solutions is developed. A set of problems starting from a simplified one to an increasingly complicated one is solved, and the solution obtained is used as an initial solution in the succeeding problem. Its validity is demonstrated by designing a suborbital winged rocket that carries 100 kg payload up to 120 km altitude.
Reusable space transportation system has aerodynamically nonlinear dynamics. Therefore, the flight dynamics depends on flight environment. Dynamic inversion (DI) theory cancels the nonlinear dynamics by state feedback and gives desired linear response. As the dynamics has a high relative degree, control system design becomes complex, because higher order derivative is needed to develop a control input. Hierarchical DI theory which develops DI theory can reduce the complexity of a nonlinear flight control system. In Hierarchical DI theory, linearized approximation transfer functions for each hierarchy are constructed and it is easy to determine the control gains. However, it must be assumed that all the actuators have the same response characteristics when linearized approximation transfer functions are constructed. In general, all of the actuator dynamics aren’t same, and it influences the flight control system based on hierarchical DI method. In this paper, the effect by the differences of actuator responses is evaluated.
Kyushu Institute of Technology has been developing experimental winged rocket for fully reusable space transportation system since 2005. WIRES#015, the subscale flight model of suborbital vehicle will be launched from Mojave Desert, California in 2020. The LOX-LNG engine employed for this vehicle has thrust vector control (TVC) system to improve the control performance during the ascent phase when dynamic pressure is still low. However, when the vehicle experiences maximum dynamic pressure, the natural frequency of the vehicle’s dynamics may become higher than cut-off frequency of TVC actuator, and the actuator performance becomes saturated. In this research, the attitude control law in the longitudinal and lateral-directional motion using TVC and aerodynamic control surfaces for a powered ascent was designed based on eigenvalue analysis. The response of attitude angle and TVC actuator performance was evaluated based on non-linear flight simulation. In this simulation, the TVC actuator model with saturation characteristic is taken into account.