Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 2005"

Wind Tunnel Tests on a Different Phase Three-Stage Savonius Rotor

Abstract: In order to decrease the torque variation of a Savonius rotor and improve the starting characteristics, a new type of Savonius rotor, which has three stages with 120-degree bucket phase shift between the adjacent stages, has been designed and made. Wind tunnel tests make it clear that both the static and dynamic torque variations in one revolution of this three-stage rotor have been greatly smoothed in comparison with an ordinary one-stage rotor, which means the improvement of the starting characteristics. The torque characteristics of the rotors with guide vanes were also measured. The guide vanes increased the torque coefficient on the average in the low tip speed ratio but decreased the torque coefficient in high tip speed ratio. Although the present three-stage rotor needs improvement of the aspect ratio of each stage, the three-stage rotor with no guide vane had better torque characteristics than the one-stage rotor with guide vanes for tip speed ratio larger than 0.8.

Three-Dimensional Computerized Tomographic Reconstruction of Instantaneous Distribution of Chemiluminescence of a Turbulent Premixed Flame

Abstract: The advanced CT (computerized tomography) reconstruction technique for measuring an instantaneous three-dimensional distribution of chemiluminescence of a turbulent premixed flame is accomplished. In the technique, first, instantaneous two-dimensional images (‘projection’ images) of an objective flame are simultaneously taken from forty horizontal directions with a forty-lens camera. Next four hundred horizontal CT images, which are reconstructed from the ‘projection’ images by MLEM (maximum likelihood expectation maximization) algorithm, are vertically accumulated, resulting in an instantaneous three-dimensional distribution of flame-chemiluminescence. Results for a propane-air fuel-rich-premixed turbulent flame are as follows. The flame front is observed to be a thin wrinkled luminous region of 0.6mm in thickness. The three-dimensional result clearly shows that the cusps observed in horizontal cross-sections correspond to ridges of the three-dimensional flame front. The luminosity is quenched at the ridges by Lewis number effect. Finally, various types of display of three-dimensional distribution are performed to demonstrate the three-dimensionality of data acquisition.

Experimental Investigations on Pressure Fluctuations and Vibration of the Impeller in a Centrifugal Pump with Vaned Diffusers

Abstract: The pressure fluctuations acting on the impeller and the impeller vibration excited by the fluctuations were investigated in a centrifugal pump with several vaned diffusers. Firstly, the pressures both acting on the impeller and in the volute were measured simultaneously. It was demonstrated that both the volute static pressure and the pressure fluctuations on the impeller are uneven circumferentially (not uniform) under off-design operating conditions. At high flow rates, the pressure fluctuations are large in the front of the volute exit, where the static pressure is low. Secondly, the impeller vibration excited by the fluctuations was measured. It was found that resonance can be excited even when the resonance condition of rotor-stator interaction is not satisfied and sidebands occur in frequency spectra because of the circumferential unevenness of the fluctuations. Resonance can also be excited when a natural frequency of the impeller coincides with the frequencies of sidebands. Furthermore, the vibration wave is a traveling wave in the circumferential direction when resonance of a nodal diameter mode is excited, and the resonant frequency may depend on the traveling direction of the wave due to the inertia effect (added mass) of water.

A Feasibility Study of CO2-Based Rankine Cycle Powered by Solar Energy

Abstract: An experiment study was carried out in order to investigate feasibility of CO 2 -based Rankine cycle powered by solar energy. The proposed cycle is to achieve a cogeneration of heat and power, which consists of evacuated solar tube collectors, power generating turbine, heat recovery system, and feed pump. The Rankine cycle of the system utilizes solar collectors to convert CO 2 into high-temperature supercritical state, used to drive a turbine and produce electrical power. The cycle also recovers thermal energy, which can be used for absorption refrigerator, air conditioning, hot water supply so on for a building. A set of experimental set-up was constructed to investigate the performance of the CO 2 -based Rankine cycle. The results show the cycle can achieve production of heat and power with reasonable thermodynamics efficiency and has a great potential of the application of the CO 2 -based Rankine cycle powered by solar energy. In addition, some research interests related to the present study will also be discussed in this paper.

A Parametric Study of Low-Temperature, Late-Injection Combustion in a HSDI Diesel Engine

Abstract: A parametric study of automotive diesel combustion in a low-temperature, late-injection combustion regime is described. Injection pressure was varied from 600-1200 bar, swirl ratio from 1.44-7.12, and intake temperature from 30-110°C. In-cylinder pressure records, heat release analysis, spatially-integrated soot luminosity, and images of the spatial distribution of combustion luminosity are employed to study the influence of these parameters on the combustion and soot formation/oxidation processes. Load points of 3 and 6 bar gross IMEP at 1 500 RPM and an O 2 concentration of 0.15 are considered. Increased injection pressure is found to enhance the early mixture formation process, resulting in increased peak apparent heat release, generally decreased soot luminosity, and modestly increased light-load soot oxidation rates. At lower injection pressures, more soot luminosity is observed from the squish volume. In contrast, variation of flow swirl impacts the latter half of the combustion process, and affects the initial combustion only slightly. An optimum Ricardo swirl ratio of roughly 3 is found for best moderate-load efficiency and soot oxidation. A marked reduction in early heat release rates and peak soot luminosity is observed with decreased intake temperature. Nevertheless, significant in-cylinder soot luminosity is observed even at the lowest intake temperatures, indicating that complete suppression of in-cylinder soot formation is difficult with the fuel injection and combustion system characteristics employed.

Computational Validation for Flow around a Marine Propeller Using Unstructured Mesh Based Navier-Stokes Solver

Abstract: Results of computational fluid dynamics validation for flow around a marine propeller are presented. Computations were performed for various advance ratios following experimental conditions. The objectives of the study are to propose and verify a hybrid mesh generation strategy and to validate computational results against experimental data with advanced computational fluid dynamics tools. Computational results for both global and local flow quantities are discussed and compared with experimental data. The predicted thrust and torque are in good agreement with the measured values. The limiting streamlines on and the pathlines off the propeller blade as well as the pressure distribution on the blade surface reproduce the physics of highly skewed marine propeller flow with tip vortex very well. The circumferentially averaged velocity components compare well with the measured values, while the velocity magnitude and turbulence kinetic energy in the highly concentrated tip vortex region are under-predicted. The overall results suggest that the present approach is practicable for actual propeller design procedures.

Ni Nano-Magnetic Fluid Prepared by Submerged Arc Nano Synthesis System (SANSS)

Abstract: This study attempts to prepare Ni nano-magnetic fluid using the developed submerged arc nanoparticle synthesis system (SANSS). Using optimized process parameters, Ni nanoparticles having average diameter of 10 nm were be fabricated, and these Ni nanoparticles prepared by the SANSS has strong magnetic features. When the surfactant PVP-K30 is added to the prepared nanofluid, molecules of the surfactant adhere to the surface of the nanoparticles, enabling the nanoparticles to remain in steady suspension and good dispersion. The nanofluid thus obtained was magnetic and had good flow property. In contrast, Ni particles in nanofluid without surfactant added cannot maintain good dispersion and there is no interdependent motion between the particles and the fluid. Traditional magnetic fluids containing non-nanoscaled particles are non-Newtonian fluids with viscosity higher than that of pure fluids without particles, whereas magnetic fluids with well dispersed nanoparticles more closely resemble Newtonian fluids. The Ni nanoparticles fabricated by the SANSS has no residual magnetization or coercive force, thus showing superparamagnetism. Under the magnetic field effect, Ni nanoparticles will move in the direction of the magnetic field. Nanoparticles can resume steady suspension in the carrying liquid when the magnetic field is removed.

Dynamic Simulation and Optimization of Start-up Processes in Combined Cycle Power Plants

Abstract: This paper treats the development of a dynamic simulation model and its application to the optimization of a start-up process for a combined cycle power plant. Generally, the plant system design is complicated, and the control design is difficult to establish without dynamic simulation. The comparison of the simulation results and the plant data is reported. The obtained results demonstrate that the simulation is reliable to evaluate the plant dynamic phenomenon and available to predict the operational processes. However, not only an analytical method but also the development of a design method is important to determine the optimal operational procedure. In this paper, the dynamic simulation and the nonlinear programming are combined, and it proposes the design method that optimizes the operational parameters.

Comparison of Three Soot Models Applied to Multi-Dimensional Diesel Combustion Simulations

Abstract: In this paper, three soot models previously proposed for diesel combustion and soot formation studies are briefly reviewed and compared. The three models are (1) two-step empirical soot model, (2) eight-step phenomenological soot model, and (3) complex-chemistry coupled phenomenological soot model. All three models have been implemented into the KIVA-3V simulation code. For comparison, a heavy-duty DI diesel engine case with fuel injection typical of standard DI diesel operating conditions was studied. Flame structures of a single diesel spray predicted using these three models were compared, and the results offer our perspective on the application of these three models to soot modeling in diesel engines.

Combined heat, air, moisture, and pollutants transport in building environmental systems

Abstract: Combined heat, air, moisture and pollutants transport (CHAMP) exists across multi-scales of a building environmental system (BES): around the building, through the building shell/envelope, inside a multizone building, and in the micro-environments around occupants. This paper reviews previous work and presents a system model for simulating these transport processes and their impacts on indoor environmental quality. Components of the system model include a multizone network flow model for whole building, a room model for air and pollutant movement in ventilated spaces, a coupled heat, air, moisture, and pollutant transport model for building shell, an HVAC model for describing the dynamics of the heating, ventilating and air-conditioning (HVAC) system, and shared databases of weather conditions, transport properties of building materials, and volatile organic compounds (VOCs) emissions from building materials and furnishings. The interactions among the different components, and challenges in developing the CHAMP system model for intelligent control of BES are also discussed.

Laminar Burning Velocity of Stoichiometric CH4/air Premixed Flames at High-Pressure and High-Temperature

Abstract: Experimental and numerical studies on laminar burning velocities of stoichiometric CH4/air flames were performed at high pressure and high temperature. A stoichiometric CH4/air mixture was diluted by helium in order to restrain the intrinsic flame instabilities occurring at high pressure. Measurements of laminar burning velocity for burner-stabilized flames were conducted by a technique employing particle tracking velocimetry (PTV) and planar laser induced fluorescence for OH radical (OH-PLIF) simultaneously, which measures the instantaneous local burning velocity. Laminar burning velocities were determined by the average values of local burning velocities in the region where the Karlovitz number are sufficiently small, meaning that the effect of flame stretch and curvature can be neglected. Numerical simulations were also conducted using a one-dimensional premixed flame code. Detailed reaction mechanisms and the 4-step reduced mechanism were examined, and their results were compared with experimental results to investigate the feasibility of predicting the flame characteristics at high pressure and high temperature, based on the reaction mechanisms.

Studies of the Combustion Process with Simultaneous Formaldehyde and OH PLIF in a Direct-Injected HCCI Engine

Abstract: This paper presents simultaneous laser based measurements of formaldehyde and OH-radical distributions in a 0.5 liter optical HCCI engine with direct injection. Formaldehyde is formed as an intermediate species when combusting hydrocarbons. The formation occurs through low temperature reactions in an early phase of the combustion process. Later in the process formaldehyde is being consumed. Formaldehyde is, therefore, used as indicator of the first stage of combustion and a marker of zones with low-lemperature reactions. The OH radical is formed as an intermediate during the high temperature reactions, and is used as a marker of zones where the combustion is ongoing. The purpose of the investigation was to study how the combustion process is affected by the change in homogeneity that arises from early and late injection, respectively. The measurement technique used was planar laser-induced fluorescence where formaldehyde was excited at 355 nm and OH at 283 nm. (Less)

Performance and Internal Flow of Cross-Flow Fan with Inlet Guide Vane

Abstract: The effect of angle and length of the inlet guide vane on the performance of the cross-flow fan was examined. By installing guide vane of one sheet in tongue division side in the suction region, the performance of the cross-flow fan becomes more high pressure and high efficient than the case without the guide vane. The prerotation of the inlet flow which is counter directional with the rotation of the rotor is generated by the guide vane. In the high flow region, the high pressure and high efficiency are obtained since the suction cascade work increases by the prerotation of the flow, and since the leading edge separation of the suction cascade is more avoided to high flow. Moreover, in the low flow region, it is possible to suppress the circulating flow in scroll side in the rotor suction inlet. Therefore, the high efficiency is obtained in the low power compared to the result without the guide vane.

Magnetic Fluid Devices for Driving Micro Machines

Abstract: This paper is concerned with the development of micro magnetic fluid devices for driving micro machines. Two kinds of new magnetic fluid devices are proposed. One is the magnetic fluid motor, and another one is reciprocating actuator. These micro devices are composed of a permanent NdFeB magnet and kerosene-based magnetic fluid HC-50. They are characterized by wireless operation with alternating magnetic field. The driving characteristics of micro magnetic fluid devices are examined by using a digital high speed video camera system. The rotary motion of the micro magnetic fluid motor shows the existence of rotational regions and irrotational regions in frequencies of external magnetic field. The amplitude of reciprocating actuator depends on the frequency of magnetic field. The effect of the volume of magnetic fluid adsorbed to the permanent magnet is also revealed experimentally.

Diesel Combustion and Emission Using High Boost and High Injection Pressure in a Single Cylinder Engine : Effects of Boost Pressure and Timing Retardation on Thermal Efficiency and Exhaust Emissions( Advanced Combustion Technology in Internal Combustion Engines)

Abstract: Heavy-duty diesel engines have adopted numerous technologies for clean emissions and low fuel consumption Some are direct fuel injection combined with high injection pressure and adequate in-cylinder air motion, turbo-intercooler systems, and strong steel pistons Using these technologies, diesel engines have achieved an extremely low CO 2 emission as a prime mover However, heavy-duty diesel engines with even lower NOx and PM emission levels are anticipated This study achieved high-boost and lean diesel combustion using a single cylinder engine that provides good engine performance and clean exhaust emission The experiment was done under conditions of intake air quantity up to five times that of a naturally aspirated (NA) engine and 200 MPa injection pressure The adopted pressure booster is an external supercharger that can control intake air temperature In this engine, the maximum cylinder pressure was increased and new technologies were adopted, including a monotherm piston for endurance of P max = 30 MPa Moreover, every engine part is newly designed As the boost pressure increases, the rate of heat release resembles the injection rate and becomes sharper The combustion and brake thermal efficiency are improved This high boost and lean diesel combustion creates little smoke; ISCO and ISTHC without the ISNOx increase It also yields good thermal efficiency

Steady State Analysis of Small Molten Salt Reactor

Abstract: The Molten Salt Reactor (MSR) is a thermal neutron reactor with graphite moderation and operates on the thorium-uranium fuel cycle. The feature of the MSR is that fuel salt flows inside the reactor during the nuclear fission reaction. In the previous study, the authors developed numerical model with which to simulate the effects of fuel salt flow on the reactor characteristics. In this study, we apply the model to the steady-state analysis of a small MSR system and estimate the effects of fuel flow. The model consists of two-group neutron diffusion equations for fast and thermal neutron fluxes, transport equations for six-group delayed neutron precursors and energy conservation equations for fuel salt and the graphite moderator. The following results are obtained: (1) in the rated operation condition, the peaks of the neutron fluxes slightly move toward the bottom from the center of the reactor and the delayed neutron precursors are significantly carried by the fuel salt flow, and (2) the extension of residence time in the external-loop system and the rise of the fuel inflow temperature show weak negative reactivity effects, which decrease the neutron multiplication factor of the small MSR system.

Enhancement of Stratified Charge for DISI Engines through Split Injection

Abstract: The effect of split injection on the mixture characteristics of DISI (Direct Injection Spark Ignition) engines was investigated firstly by the Laser Absorption Scattering (LAS) technique. Through splitting the fuel injection process, two possible benefits were found: 1) High density liquid droplets piling up at the leading edge of the spray can be circumvented, subsequently the reduction of the spray tip penetration; 2) The quantity of over lean (Φ v < 0.7, Φ v : equivalence ratio of vapor) mixture in the spray can be significantly reduced. These are believed to contribute to the reduction of the engine-out smoke and HC emissions. In order to clarify the mechanism behind the effect of the split injection, the spray-induced ambient air motion was investigated by the LIF-PIV technique. The strong ambient air entrainment into the tail region of the spray and a counter-vortex structure were found in both the single and split injections. In the case of the single injection, the spray develops in extending its length, subsequently a larger volume results and thus it is diluted to over lean by the ambient air entrainment. In contrast, in the case of split injection, the second spray is injected into the tail region of the first spray and its evaporation is promoted by the ambient air motion induced by the first spray. Hence the replenishment of the liquid fuel into the leading edge of the first spray is reduced. As a consequence, the high density liquid droplets piling up at the leading edge is avoided. Furthermore, a more compact spray results so that the ambient air motion plays a positive role on evaporating the spray into more combustible (0.7 < Φ v < 1.3). This is especially true in the tail region of the spray and the region where the counter-vortex motion is occurring.

Unstructured adjoint method for Navier-Stokes equations

Abstract: For efficient aerodynamic design optimization, a discrete adjoint code is developed from an unstructured hybrid mesh Navier-Stokes solver. The adjoint code is verified by comparison of flux Jacobian and objective function gradient with a finite difference method. An aerodynamic design tool is developed utilizing the flow solver, adjoint code and a gradient-based optimizer and applied to a design example of a high-lift device. Use of prism layer grid sensitivities is suggested for more efficient gradient calculation from the adjoint analysis of Navier-Stokes equations with unstructured hybrid mesh.

Optimization of Blade Sweep in a Transonic Axial Compressor Rotor

Abstract: This paper describes the optimization of blade sweep in a transonic axial compressor rotor. The shape optimization has been performed using response surface method and the three-dimensional Navier-Stokes analysis. Two shape variables of the rotor blade, which are used to define the rotor sweep, are introduced to increase the adiabatic efficiency of the axial compressor. Blade sweep has been used in the transonic compressor design with the intent of reducing shock losses. Throughout the optimization, optimal shape having a backward sweep is obtained. Adiabatic efficiency, which is the objective function of the present optimization, is successfully increased by 1.25 percent. Separation line due to the interference between a shock and surface boundary layer on the blade suction surface is moved downstream for the optimized blade compared to the reference one. It is noted that the increase in adiabatic efficiency for the optimized blade is caused by moving the separation line to the downstream on the blade suction surface.

Numerical Analysis for Weld Formation Using a Free-Burning Helium Arc at Atmospheric Pressure

Abstract: In order to clarify the formative mechanism of weld penetration in an arc welding process, a numerical model is useful to understand quantitative values of the balances of mass, energy and force in the welding phenomena. In the present paper, the whole region of welding process using a free-burning arc, namely, tungsten cathode, arc plasma and weld pool is treated in a unified numerical model to take into account the close interaction between the arc plasma and the liquid metal. Calculations are made for the time dependent development of the weld pool for the free-burning arc in helium at atmospheric pressure. It is shown that the calculated convective flow in the weld pool is dominated by the surface tension gradient force and the electromagnetic force. It is also shown that different surface tension properties can change the direction of re-circulatory flow in the weld pool and dramatically vary the weld penetration geometry.

Flow Field in Swirl-Type Tubular Flame Burner

Abstract: The flow field in swirl-type tubular flame burners was measured using a Particle Imaging Velocimetry (PIV) system with an easily controlled kerosene droplet tracer generator. Through characterization of the flow field in two burners with different swirl numbers, it was found that the flow is an axisymmetric vortex flow. The tangential component of the velocity is zero at the tube center, and increases proportionally with radius at first, and then falls slowly in a radial direction. The gradient of the tangential component near the vortex center depends significantly on the swirl number and the flow rate. The vortex center oscillates around the tube center in a roughly circular area, and this precession is significantly sensitive to the swirl number. The radius of the precession area shrinks as the swirl number increases. The radial distributions of the axial velocity take a plateau-shape for the weak swirl burner (swirl number S = 0.21), whereas they take an M shape for the strong swirl burner (S = 0.78) with reverse flow in the vicinity of the burner axis. The occurrence of the axial reverse flow is dominated by the swirl number, and is affected by the flow rate as well. Finally, a comparison was made between the swirl numbers calculated with the measured velocity profiles in a cross section and those calculated from the input angular momentum.

Effects of Pressure on Burning Velocity and Instabilities of Propane-Air Premixed Flames

Abstract: Spherically propagating laminar flames at elevated pressures in a large volume bomb were studied for propane-air mixtures. The effects of the initial mixture pressure on the burning velocity and flame instabilities were investigated varying the initial pressure from 0.10 to 0.50MPa. The Markstein number decreased with the increase in the initial pressure. The burning velocities at elevated pressures are affected not only by the change in the unstretched burning velocity but also by the variation in the Markstein number, or the variation in the sensitivity of the burning velocity to the flame stretch. The flame with a low Markstein number was unstable. Cellular flame structure developed earlier in such cases. Cellular structure accelerated the flame propagation. The burning velocity was affected by the flame instabilities in addition to the above two factors.

Torque Control of a Rehabilitation Teaching Robot Using Magneto-Rheological Fluid Clutches

Abstract: A new robot that makes use of MR-fluid clutches for simulating torque is proposed to provide an appropriate device for training physical therapy students in knee-joint rehabilitation. The feeling of torque provided by the robot is expected to correspond to the torque performance obtained by physical therapy experts in a clinical setting. The torque required for knee-joint rehabilitation, which is a function of the rotational angle and the rotational angular velocity of a knee movement, is modeled using a mechanical system composed of typical spring-mass-damper elements. The robot consists of two MR-fluid clutches, two induction motors, and a feedback control system. In the torque experiments, output torque is controlled using the spring and damper coefficients separately. The values of these coefficients are determined experimentally. The experimental results show that the robot would be suitable for training physical therapy students to experience similar torque feelings as needed in a clinical situation.

Micro-Metallurgy of Splats: Theory, Computer Simulation and Experiment

Abstract: Over the last one and half decades the constantly growing interest to a problem of rapid solidifying the melted micro-droplets of various materials at their impact with a surface has been marked. This phenomenon is at the basis of many technologies, such as plasma, detonation and flame spraying, arc-spray, spray-casting, micro-atomization of powders, solder-drop-printing in microelectronic, making the microcrystal and amorphous materials, and producing the high-temperature superconductors. The system micro-droplet - substrate is very suitable for a physical materials science in studies of the non-equilibrium phase diagrams of different alloys and composite materials under extreme conditions. Practically speaking we have dealings with independent scientific and technological line of investigation - micro-metallurgy of a small volume of melt at its collision with an obstacle surface or, in other words, splats' micro-metallurgy. The paper presented is devoted to a brief review of theoretical, computational and experimental investigations carried out by composite authors during the last decade.

Control of Cavitating Flows: A Perspective

Abstract: This is a summary of our research on unsteady partial cavitation and ventilated partially and supercavitating flows with special emphasis on control strategies. We draw upon our experience with a variety of projects ranging from the experimental and numerical description of sheet/cloud cavitation to the control of high-speed supercavitating bodies. In addition, our numerical simulations of partially cavitating hydrofoils indicate that there is a regime where the potential exists for feedback control of gust-induced oscillations. These efforts are in the incubation stage. The purpose of this presentation is to provide our perspective on the problems and opportunities for control of cavitation and to encourage a healthy interchange of ideas at this workshop.

Research on the Influence of Hydrogen and Carbon Monoxide on Methane HCCI Combustion

Abstract: In this research, the influence on natural gas combustion of H 2 and CO was investigated by numerical calculations with elementary reactions. The investigation was carried out using the following procedures: 1. To research basic oxidation characteristics of CH 4 /H 2 /CO mixed fuel, parametric calculations for initial temperature were carried out. 2. For investigation of the effect of H 2 and CO on CH 4 combustion, the calculations with H 2 and CO initial mole fraction variation was carried out. As a result, it was clarified that the oxidation temperature of CO was higher than that of CH 4 and H 2 , the increase of H 2 initial fraction has the effect to advance CH 4 ignition timing, and increase of the CO fraction, under the condition that only CO was added, has the opposite effect of H 2 addition.

Impact of Formaldehyde Addition on Auto-Ignition in Internal-Combustion Engines

Abstract: By employing a direct-injection diesel engine equipped with a common-rail type of injection system, by adding formaldehyde (CH 2 O) to the intake air, and by changing the fuel-injection timing, the compression ratio and the intake-air temperature, a mechanism for CH 2 O as a fuel additive to affect auto-ignition was discussed. Unlike an HCCI type of engine, the diesel engine can expose an air-fuel mixture only to a limited range of the in-cylinder temperature before the ignition, and can separate low- and high-temperature parts of the mechanism. When low-temperature oxidation starts at a temperature above 900 K, there are cases that the CH 2 O advances the ignition timing. Below 900 K, to the contrary, it always retards the timing. It is because, above 900 K, a part of the CH 2 O changes into CO together with H 2 O 2 as an ignition promoter. Below 900 K, on the other hand, the CH 2 O itself acts as an OH radical scavenger against cool-flame reaction, from the beginning of low-temperature oxidation. Then, the engine was modified for its extraordinary function as a gasoline-knocking generator, in order that an effect of CH 2 O on knocking could be discussed. The CH 2 O retards the onset of auto-ignition of an end gas. Judging from a large degree of the retardation, the ignition is probably triggered below 900 K.

Cycle Analysis of Micro Gas Turbine-Molten Carbonate Fuel Cell Hybrid System

Abstract: A hybrid system based on a micro gas turbine (µGT) and a high-temperature fuel cell, i.e., molten carbonate fuel cell (MCFC) or solid oxide fuel cell (SOFC), is expected to achieve a much higher efficiency than conventional distributed power generation systems. In this study, a cycle analysis method and the performance evaluation of a µGT-MCFC hybrid system, of which the power output is 30kW, are investigated to clarify its feasibility. We developed a general design strategy in which a low fuel input to a combustor and higher MCFC operating temperature result in a high power generation efficiency. A high recuperator temperature effectiveness and a moderate steam-carbon ratio are the requirements for obtaining a high material strength in a turbine. In addition, by employing a combustor for complete oxidation of MCFC effluents without additional fuel input, i.e., a catalytic combustor, the power generation efficiency of a µGT-MCFC is achieved at over 60%(LHV).

A study on the local flame displacement velocity of premixed turbulent flames

Abstract: The local flame properties of turbulent propagating flames with respect to the ratio of the turbulence intensity to the laminar burning velocity u’/SL0 in the flamelet regime have been investigated experimentally for methane, propane and hydrogen mixtures having nearly the same laminar burning velocity with different equivalence ratios. u’/SL0 is varied as 1.4 and 2.3. A 2D laser tomography technique is used to obtain the flame configuration and movement in a constant-volume vessel and then the local flame displacement velocity SF is quantitatively measured as a key parameter of turbulent combustion. As a result, the mean value of SF shows to be affected by u’/SL0, which indicates a relation between the characteristic chemical reaction time and the characteristic flow time, to some extent, especially for leaner and richer mixtures. SF is also discussed by the concept of preferential diffusion and Markstein number which can affect the local burning velocity characteristics.

Surface Pressure Measurement on a Rotating Blade of Field Horizontal Axis Wind Turbine in Yawed Condition

Abstract: This paper shows the pressure distribution at the 50%radial section of a rotor blade of 10m-diameter wind turbine in yawed operation. The pressure sensors were mounted on the blade, and local inflow angle and local dynamic pressure were measured with the use of five hole Pitot tubes at 1 chord length upwind of the blade leading edge. It was found that the normal force coefficient in yawed condition decreases compared to that for non-yawed condition. Even if local angle of attack and the relative inflow velocity are the same, pressure distribution shows differences due to the local slip angle. The tufts flow-visualization on the rotating blade was carried out by setting a video camera on the rotating system. Separation in the region of middle chord to trailing edge on suction surface is thought to be the main reason of the reduction of normal force coefficients.