In this study, potential site-specific designs are analyzed using standard FEA tools with the dynamic structural problem simplified to a static fundamental problem with unidirectional loading. Loading values are obtained from design specific results from a numerical simulation analysis. The properties of materials amenable to 3D printing were considered here and analyzed for their feasibility for use as micro Kaplan hydro turbines.

Static structural analyses were performed for varied numbers of stator/ runner blades and turbine blade aspect ratios against blade thickness fractions and blade tip thickness fractions. Studies with the use of additive manufacturing materials such as ULTEM and PolyCarb showed favorable results.

Use of static structural analysis in the design process refines and facilitates to narrow down to the optimal design. The process helps to obtain a sizeable site-specific design in the much needed renewable energy sector.

Higher thermal efficiency and operational flexibility are required for next-generation thermal power plants to reduce CO₂ emission and compensate for the unstable power output of variable renewable energy generation systems. The advanced humid air gas turbine (AHAT) system is expected to meet these requirements. The system concept and cycle performances of the AHAT system were verified by operation tests of a 3MW-class test plant and a 40MW-class pilot plant so far. However, operational flexibility of commercial scale system has not yet been sufficiently clarified by experiment or calculation. Therefore, we developed a dynamic simulation model of commercial scale system and analyzed the operational flexibility. In this paper, we discuss startup characteristics and frequency response characteristics of commercial scale AHAT system.

As a basic study for exploring the best layout of small vertical axis wind turbines, computational fluid dynamics (CFD) using the dynamic fluid/body interaction (DFBI) model had been carried out for the cases of tandem layout of 2-dimensional two rotors, which corresponded to the experimental miniature models with a diameter of D = 50 mm. A condition in which two rotors rotate in the same direction (TCO) and another condition in which two rotors rotate in different directions (TIR) were simulated with different spaces (gap) between the two rotors. As the results, no essential difference was observed between the flow fields of the TCO and TIR conditions. The equivalent wind speed of the downwind rotor became almost constant with the value of about 70% of the upstream wind speed (10 m/s) when gap/D was 4 or more. In the same state, the power output of the downwind rotor was about 30% of that of the upwind rotor.

Recent researches have shown that enhanced focal adhesion between cells and extracellular matrix (ECM) and intracellular actin polymerization can accelerate cellular functions like adhesion and differentiation. In this study, mesenchymal stem cells (MSCs) from Sprague Dawley (SD) rats were cultured on the substrates with surface topography, the groove patterns in micro scale, to verify the relationship between cell adhesion and differentiation. Impeded osteogenic differentiation was observed on cells cultured with micro-topographic substrates. This result may be caused by the decrease in focal adhesion. Through this study, it is expected that the technique to control bone regeneration by surface microtopography will be one more step closer.

This paper presents the near-infrared temperature measurement of water near nano-magnetic particle (NMP) clusters heated inductively in the microfluidic channel. This measurement technique is based on the temperature dependence of the absorption coefficient of water. To the bottom of a microfluidic channel in which water flowed, NMPs were aggregated by fluidic and magnetic effects. Absorbance images were obtained when the NMPs were heated inductively by an alternating magnetic field, then variations with heating time were investigated to find out the difference absorbances. The absorbance images showed the 2D geometry of the NMP clusters. Based on this geometry, the flow velocity distribution in the water region over the NMP clusters was numerically simulated. The present method is useful for hyperthermia researches using cultured biological cells and for various chemical applications of NMPs.

Various techniques and methods were implemented to identify the behavior of fluid motion within porous media. In numerical analysis, most cases used simplified representations to observe and understand the behavior of the fluid flow within the porous medium. However, there were limited information regarding the full three-dimensional cases for identifying fluid behavior and heat transfer characteristics within porous vicinity. In this study, three-dimensional approach using CFD (Computational Fluid Dynamics) simulation was taken into consideration to provide the sufficient information regarding fluid motion within the porous medium. The irregularity characteristics of the actual porous structure were also taken into consideration to foresee the influence of this factor towards heat transfer characteristics and interaction between both porous medium and fluid motion. The type of porous structure used was adapted from the Ashby’s theory related to porous and lattice structure. Modification within the Ashby structure was done to suit the irregularity of the real porous medium. Two types of porosity were investigated during the study which were 75 and 85 percent porosity. The controlled variables which were the porosity dimensions and fluid flow conditions, were set to be at 200 μm and laminar flow. Different range of imposed velocity flow were tested to foresee the influence of these parameters towards the formation of flow pattern and heat transfer behavior within the porous vicinity. The outcomes of this study were then compared with the experimental data as the boundary conditions in the simulation were set to be the same with those in the experimental setup.

It is important in recent years to understand the flow in the nanoscale flow channel due to the progress of microfabrication technology and the expectation to the engineering use of desalinated film, biological film, etc. It is known that dynamics different from macroscale flow are observed in such nanoscale flow channels, and experimental and analytical clarification is required. Molecular simulation is an effective method to understand such nanoscale flow, and in this study, through non-equilibrium molecular dynamics calculations, we analyzed the influence of water molecule flow in nanoscale-wide flow channels

A hydrogenated amorphous silicon (a-Si:H) are highly expected as potential materials applicable to electronic or optoelectronic thin-film devices such as thin-film transistors. Plasma chemical vapor deposition (PCVD) is one of the common and powerful methods to form a-Si:H films. We focus on a deposition process of a-Si:H films on a silicon (100) substrate by the PCVD using SiH4 as a precursor. To understand the deposition mechanism, we investigated influence of (a) hydrogen atoms covering the substrate as a hydrogen coverage θ and (b) the substrate temperature T_S on the adsorption probability for each chemical species. Molecular dynamics (MD) simulations were performed with the large-scale atomic/molecular massively parallel simulator (LAMMPS) MD packages using reactive force-field (ReaxFF). The following knowledges were obtained: (a) An increase in substrate temperature leads to a decrease in the adsorption probability. The reason is that the chemical species under the physisorption state has a larger possibility to receive a enough energy to desorb before changing to the chemisorption state. (b) Although the adsorption probability decreases with the increase in hydrogen coverage, it does not become 0 even hydrogen coverage is 1.00. The reason is that the hydrogen atoms thermally diffuse on the substrate, and the unstable hydrogen is displaced by the radical species.

In compressible computational fluid dynamics (CFD) analyses for combustion chamber of liquid rocket engine, the combination of cubic type equation of state (EOS) and classical mixing rule (CMR) is mostly used as typical EOS for mixture system. However, validation of the EOS for the mixture of liquid rocket propellant has hardly been validated due to lack of experimental data. Previously, validation of cubic type EOS with CMR was conducted by molecular simulation applying an ab-initio intermolecular potential as a quantum chemical approach. However, the accuracy of the H₂-O₂ potential is questionable because it was constructed on the basis of molecular orbital (MO) calculation for some limited molecular orientations. Therefore, in this study, we performed MO calculations for more molecular orientations between H₂-O₂ and reconstructed the intermolecular potential on the basis of the results of MO calculations with CCSD(T)/augcc-PVQZ level of theory. Next, we revalidated cubic type EOS coupled with CMR by evaluating the thermophysical properties of supercritical oxygen-hydrogen mixture system using Monte Carlo (MC) simulations applying the improved H₂-O₂ potential. As a result, we confirmed that cubic type EOS coupled with CMR can roughly reproduce the thermophysical properties obtained from MC simulation. Therefore, it was suggested that cubic type EOS with CMR can be applied to CFD analyses for combustion chamber of liquid rocket engine.

In rarefied gas flow conditions, where the length scale of the flow is comparable with the mean free path of the gas, a Knudsen thermal force can be induced. This force can be generated on a structure immersed in a gas in the presence of thermal gradients1. Such phenomenon is significant for vacuum microbalances as well as for microsystem sensors and actuators. The mechanisms governing this force show strong dependence on the nature of thermal gradients within the system1. It has been studied that in the case of a heated micro-beam placed on cold flat surface, a repulsive force is exerted on the micro-beam2. Furthermore, it was also investigated that when a cold object is placed over a heated micro-ratchet surface, a propulsive force is exerted on the object. This combination of repulsive and propulsive force is the interest of this study. While measuring such forces precisely at microscale can be an arduous task, numerical simulations can provide a basis for understanding the physical mechanisms of such forces. Moreover, such forces do not occur in the continuum flow regime, and hence, the Navier-Stokes equation cannot be used, and instead, the more general Boltzmann equation is required which can be numerically solved using the direct simulation Monte Carlo (DSMC) method. The main goal of this paper is to determine the forces exerted on a uniformly heated micro-beam placed at a distance away from a cold micro-ratchet surface using DSMC simulation. Figure 1 shows that the asymmetric shape of the ratchet induces a strong non-uniform temperature distribution, which in turn, induces thermally driven flows. The strongest flows are seen in the vicinity of the ratchet tip and the corners of the solid beam.

In cross-flow water turbines, the flow channel between the casing wall and the guide vane in the downstream side becomes a diffuser when the guide vane opening is narrow. In the diffuser, energy loss is produced due to both the occurrence of flow separation and turbulence. In addition, the turbine cannot be applied in a high head because an increase in flow velocity causes cavitation at the narrow part of diffuser. Therefore, the authors propose an energy loss suppression method by sucking air from the hole opened on the wall of the upstream the diffuser. Through this study, it was confirmed that sucking air into the diffuser causes water flow separation, therefore suppressing energy loss. This was accomplished using CFD. In addition, it was noted that the total pressure distribution derived by two-dimensional jet flow theory corresponds almost to the one obtained by CFD.

In the present study, the gas-liquid two-phase flow performance of a turbopump equipped with an inducer was experimentally investigated. The almost homogeneous bubbly two-phase flow condition was successively set by the uniform aeration of gas dissolved in water upstream of the test pump, which was realized by a sudden pressure decrease with the valve closure. The gas-liquid volumetric flow rate ratio was estimated from the pump inlet pressure and the initial amount of dissolved oxygen under the assumption of mass equilibrium condition of the local dissolved oxygen. The effect of initial dissolved oxygen on the two-phase flow performance of the pump was investigated. It was observed that the head performance dropped at higher NPSH with higher dissolved oxygen condition. On the other hand, with extremely low dissolved oxygen condition, the performance curve well matched with the suction performance curve.

Centrifugal pumps requiring small flow rate and high head performance are required to improve performance at low specific speed. However, a low specific speed impeller cannot be applied to the conventional design method. Therefore, special impellers have also been proposed. In this paper proposes an impeller with circumferential and radial flow channels. Then also proposes a method to predict the performance of the impeller and evaluates its validity. As the result, it is more efficient than the conventional low specific speed pump and the unstable head curve was also improve. Furthermore, the difference between the primary performance prediction method and the experimental value is suggested to be loss of volute casing.

In this study, in a cylindrical combustor assuming development of a compact combustor system, an experimental study was conducted to clarify the effect of injection mixing. The purpose of this research is to investigate the effective mixing conditions of fuel/air injection method. The combustion cylinder is composed of heat-resisting glass for visualization. The combustion stability depending on the injection method is investigated, and the stability map of the flame is shown with a wide range of equivalence ratio.

In recent years, renewable energy attracts attention due to the concern about the global warming by fossil fuel use. Among them, small hydropower is effective because stable power generation is possible throughout the year, and there are many places that can generate electricity. Although small hydropower is already widespread, there is a problem that there is a limit to the installation place and the load on the natural environment is relatively large for the large scale small hydropower over 10kW. Therefore, we focused on power generation using pico hydropower, which can be applied to agricultural water and small stream. Because pico hydropower is less efficient than large water turbines, we adopted contra-rotating rotors that can be expected to be highly efficient. In addition, focus on inline agricultural water, we designed the inline small hydroturbine. In previous researches, the influences of the tip clearance, solidity and blade thickness on the efficiency were investigated, and each preferred value has been studied. In this report, we created a new impeller model that combines the preferred values of tip clearance, solidity, and blade thickness clarified by the previous studies, and investigated the performance improvement effect by numerical analysis. As a result, the pressure loss and the internal flow condition of the high performance model improved compared with the base model, and the efficiency was improved.

The cascade pump is one of the special type pumps. In this pump, the rotation of the impeller generates a vortex in the casing, and the fluid is pressurized and transported. However, the efficiency of this pump is less than 30% and very low compared to others. In recent years, CFD used in turbo pumps is not often used in special pumps. Therefore, CFD studies of cascade pumps are important. The changes in efficiency were investigated by changing each dimension of a commercially available cascade pump. The comparison of CFD and specification values shows that CFD can predict the performance of cascade pumps with high accuracy. Therefore, the usefulness of CFD in the present study was shown. With respect to the change in efficiency, it has been found that improving the casing clearance and chamfering increases the efficiency. And as a result of examining the reason for the improvement, it became clear that the flow velocity in the pump flow path cross section is increasing.

A left ventricular assist device (LVAD) has been used for not only left ventricular assist but also right ventricular assist because a right ventricular assist device (RVAD) has not been existed. Therefore, LVADs is driven at off-design points because the demanded head of a right heart is different from that of a left heart. When blood pumps are driven at off-design point, the instability of impellers can occur and lead to damages of blood. In the present study, the optimum condition of clearance of journal bearing and material of the impeller in a RVAD under development was investigated. In experiments, performance tests of the RVAD were carried out and motions of the impeller were measured by two laser displacement sensors. As a result, it was confirmed that spectra of the frequency of shaft vibrations had two peaks whose frequencies were the rotational frequency f₀ and the half of it, 0.5. Ratios of the amplitude of the vibration to the mean radial clearance c_d were about 0.5. The vibrations could be associated with a whirling motion. When material of the impeller is Titanium and clearance at =80 μm, the vibration was the stablest.

In this research, it is important to achieve the compact fan size with the high performance and reduce the fan noise for the special applications. As a first step, focus on the miniaturization and high efficiency of the centrifugal fan with the special volute, the internal flow condition of a conventional model that called “Base model” was investigated by the numerical analysis. As a result, the recirculation flow occurred near the volute tongue in the Base model, because of the disagreement of the flow rate and volute size. Therefore, the new volute called “Volute mini model” was designed to suppress the recirculation flow and its performance was evaluated at the partial, operating and high flow rates. In the Volute mini model, the total pressure efficiency improves at all flow rates compared to the Base model. Furthermore, the recirculation flow near the volute tongue can be suppressed significantly, and the flow condition at the exit of the volute becomes uniform.

Supercritical CO2 has been employed as an effective working fluid in Brayton cycles. Compressors in supercritical CO2 Brayton cycles are primary components that work beyond the critical pressure and temperature. We have developed the numerical method for supercritical fluid flows with the equation of state for real gas defined in REFPROP. In this study, actual Centrifugal compressor flows are investigated under the subcritical and supercritical pressure conditions by our numerical method. The results of three-dimensional unsteady state simulations are compared with each other.

This study deals with detailed experimental and numerical investigations on aerodynamic loss of linear cascades composed of several types of low-pressure turbine airfoils developed by use of different design concepts. Important aerodynamic indices of the cascade are Zweifel factor, flow deceleration rate over the suction surface and velocity ratio. A wind-tunnel equipped with wake-generator is used to measure the cascade loss under the influence of incoming wakes.

Applications of Unsteady Computational Fluid Dynamics (CFD) for Research and Development of Steam Turbines are presented. It is well known that entropy generations in turbine flow paths are essentially unsteady aerodynamic phenomena. They need to be evaluated using measurements in model turbines and unsteady CFD. This report presents some related findings by the author’s group and intends to show our current study results for a modeling of three-dimensional vortices that are paying a major role in the unsteady flow phenomena in a steam turbine last stage at very low load operating conditions.

This paper presents numerical simulation of unsteady flows through first-stage stator and rotor blade rows in an actual middle pressure steam turbine while setting manufactured and secular-changed blades. Both blade shapes were measured from actual blades using 3D scanner during overhaul. For the long-term operation, oxide scales flowing from boiler pipes continued to collide with the stator and the rotor blades. As a result, the secular-changed stator trailing edge became thinner and the stator suction side near the throat became thicker than those of manufactured stator blade. The simulation employed numerical method developed by Tohoku University. The numerical results show that the secular-changed stator blades influence the thickness, angle and speed of wakes from stator trailing edges. That suggests the observation of wakes from stator blades or noise from rotor blades may help in predicting the degree of the stator secular change.

Flow structure and flow loss generation in a transonic axial compressor has been numerically investigated by using a large-scale detached eddy simulation (DES). The data mining techniques, which include a vortex identification based on the critical point theory and a limiting streamline visualization with the line integral convolution (LIC) method, were applied to the DES result in order to analyze the complicated flow field in compressor. The flow loss in unsteady flow field was evaluated by entropy production rate, and the loss mechanism and the loss amount of each flow phenomenon were investigated for the first rotor. In the first rotor, a shock-induced separation is caused by the detached shock wave and the passage shock wave. On the hub side, a hub-corner separation occurs due to the secondary flow on the hub surface, and a hub-corner separation vortex is clearly formed. The flow loss is mainly caused by the blade boundary layer and wake, and the loss due to the shock wave is very small, only about 1 percent of the total loss amount in the first rotor. However, the shock/boundary layer interaction causes an additional loss in the blade boundary layer and the wake, which amount reaches to about 30 percent of the total.

This paper reports an experimental investigation about the effect of the upstream pipe geometries on the unsteady phenomena of a transonic centrifugal compressor. In the investigation, steady measurements have been carried out to obtain the compressor maps, unsteady measurements have been performed at the surge and frequency characteristics of the unsteady measurement results have been investigated with Fast Fourier transform (FFT) and Wavelet transform.

In order to evaluate compressibility correction factor up to 120 m/s, air speeds in test section of wind tunnel were measured by JIS type Pitot static tube. Air speeds were calculated using four formulas estimated by each condition of incompressibility or compressibility and Bernoulli’s equation or energy equation. Calculated compressibility correction factor is a ratio of air speed assumed by compressibility and air speed assumed by incompressibility in this paper. Calculated compressibility correction factors had a 2.0 % difference at 120 m/s and had differential sensitivity coefficients of air speed. Some flow field evaluations conducted by CFD simulation are planned and there simulation result are shown in our presentation.

REGR (Reformed Exhaust Gas Recirculation) is expected as a promising system to improve the thermal efficiency in gasoline engines via hydrogen formation and endothermic reaction with fuel reforming. The present study investigates the effects of fuel molecule structure on the hydrogen formation and improvement of the thermal efficiency based on chemical equilibrium computations. First, the equilibrium compositions and the degree of endothermic reaction were compared among the fuels in a range of temperatures. Second, a calculation method to analyze the changes in intake gas compositions and combustion rates, and the increase in the heat value of the fuel was developed to compare the thermal efficiency among the fuels. The results showed that the improvements in thermal efficiency with non-alcohol hydrocarbons are larger than with alcohols due to larger heat recovery with fuel reforming despite lower hydrogen formation characteristics.

The aim of this study is to develop the method of measuring temperature distribution in gas flow using multi-junction thermocouple array. The present study investigated the measurement principle using the 2 × 2 thermocouple array, which is the simplest type in the multi-junction thermocouple array. At first, hot gas temperature measurements were conducted with the 2 × 2 thermocouple array and reference thermocouples. As a result, the thermocouple array could measure the same temperature to those by the reference thermocouples. Therefore, it was confirmed that the 2 × 2 thermocouple array can measure temperatures at four points simultaneously. In addition, output voltage from arbitrary terminals showed good agreement with one calculated from circuit equation. This means increment of measurement point, i.e. 2 × 3 or 3 × 3 etc. thermocouple array, may be possible for measuring temperature distribution in gas flow.

Although many efforts to reveal the mechanism of cycle to cycle variation of HCCI engine are conducted, it is not fully understood. In this study, the models which predict cycle to cycle variations of multi-cylinder HCCI engine are developed through feedforward neural networks. The output of the model is IMEP of a certain cycle and the inputs are combustion related variables such as in-cylinder pressure, intake pressure and exhaust pressure of previous cycles. Then the models are analyzed by sensitivity analysis and layer-wise relevance propagation method to investigate variables which may influence the cycle to cycle variation. As a result, a certain cycle’s combustion is influenced by the previous cycle through the residual gases, and the effect of the previous cycle become weaker when the injection timing is varied.

As a means for reducing combustion fluctuation, which is an issue for realizing lean combustion, researches using a method such as a high flow in a cylinder are actively conducted. However, there are still many unclear points on the influence of discharge specifications on combustion. So, in this research, we generated a flow field in the cylinder using a two-stroke optically accessible engine and, conducted the investigation of the influence of discharge energy on lean combustion. As a result, it was clear that the combustion stability can be improved by the increase of the energy supply per unit time by ignition, and that the increase of the pressure and resistance around the plug is effective to form rapidly the flame kernel.

The visualization technique using Photochromism was applied to the optical engine, and the visualization experiments of oil film behavior around the piston were conducted. The UV laser light sheet was illuminated to the glass cylinder liner and the oil film was colored linearly. The region of the oil film filled in the gap between the cylinder liner and the piston can be distinguished by the stretching motion of the colored oil. On the other hand, in the case that the gap is not filled with the oil film, the line of colored oil moves with the piston, indicating that the oil film exists on the piston land and not on the cylinder linear. It was confirmed that this technique can be used to monitor the position and the timing of the contact between the piston skirt and the cylinder liner.

Lubricants consist of base oils and additives with various functions. Typical examples of additives are oiliness improver and extreme pressure additive. Both the oiliness improver and the extreme pressure additive have the same structure of alkyl chains and polar groups, but their tribological characteristics are completely different. In order to clarify this difference, in this study, the adsorption behavior of organophosphate in the base oil is studied. All-atom molecular dynamics method is used for the simulation. The base oils of 3,5-diethyldodecane, the solute of mono-oleylphosphate, and solid walls of iron are chosen for the model, then the lubricant layer is confined between two solid walls. After the simulation started, the additives formed the association in the base oil. The cause of this is the interaction between strongly polarized phosphate groups. In addition, the additive molecules were not adsorbed on the solid surface even if the simulation was performed for 20 ns. This is because the formation of associations of the additive increases the apparent molecular weight and inhibits the diffusion in the base oil and the physical adsorption on the surface. These behaviors are unique to extreme pressure additives that were not found in the study on oiliness improver.

Low temperature combustion due to dilution of intake air using inert gas is one of the effective methods for heat loss reduction of the engine. However, the combustion velocity almost decreases due to high dilution and that is the reason why a misfire occurs. To prevent the misfire due to reduction of the combustion velocity, application of a biomass gasified gas containing both hydrogen and inert gas to dilution was proposed. Dilution gas in which hydrogen was added to the inert gas was introduced into the engine. And it was suggested that the efficiency be improved.

In auxiliary chamber type gas engine, an in-cylinder pressure vibration occurs in supercharged condition. This pressure vibration starts before the peak of the in-cylinder pressure and it has been revealed that this earlier vibration is different from knocking. By previous research revealed that low frequency earlier oscillation (LFEO) occurs by the torch jet but investigation of high frequency earlier oscillation (HFEO) has not been done. Therefore, in this study, the characteristics and the mechanism was investigated. As a result, HFEO occurs frequently at a specific torch intensity and high excess air ratio condition. Also the effect to the thermal efficiency was low compared to knock. Furthermore, by modeling the torch jet length and spreading angle, the frequency changes by the torch jet length changes. As a result, it was suggested that earlier oscillation is generated by the torch jet, and as the length of the torch jet changes, the combustion area where the pressure become high changes and the oscillation mode to be excited changes.

As renewable energy’s storage, hydrogen is drawing attention. Closed cycle hydrogen engine can use high specific heat ratio working gas, but knocking becomes a problem. So, it is necessary to reduce geometric compression ratio. However, it causes decrease of thermal efficiency. This research used argon gas for closed cycle engine, and intake valve late closing for effective compression ratio reduces as the same expansion ratio. As a result, both experiments increased indicated thermal efficiency. In the case of effective compression ratio 4.58 condition was 10.4 % higher than otto cycle thermal efficiency.