This paper reviews the present state of the art on the self-rectifying air turbines, which could be used for wave energy conversion. The overall performances of the turbines under irregular wave conditions, which typically occur in the sea, have been evaluated numerically and compared from the viewpoints of the starting and running characteristics. The types of turbine included in the paper are as follows: (a) Wells turbine with guide vanes (WTGV); (b) turbine with self-pitch-controlled blades (TSCB); (c) biplane Wells turbine with guide vanes (BWGV); (d) impulse turbine with self-pitch-controlled guide vanes (ISGV) and (e) impulse turbine with fixed guide vanes (IFGV). As a result, under irregular wave conditions it is found that the running and starting characteristics of the impulse type turbines could be superior to those of the Wells turbine. Moreover, the authors have explained the mechanism of hysteretic behavior of the Wells turbine and the necessity of links for improvement of the performance of ISGV.

This paper describes the effect of the incidence angle on the turbulence structure in the wake of a turbine rotor blade at the low inlet free-stream turbulence level. For three incidence angles of -5, 0 and 5 degrees, mid-span energy spectrum as well as mid-span profiles of mean velocity magnitude and turbulence intensity are reported at three downstream locations in the wake. Vortex shedding frequencies are obtained from the energy spectrum. The result shows that as the incidence angle changes from-5 to 5 degrees, the boundary layer on the suction surface tends to be thickened, which results in widening of the wake. Strouhal numbers based on the shedding frequencies have a nearly constant value of 0.3, independent of tested incidence angles.

In order to reduce NOx emissions in the 20kW class microturbine under development, the low NOx characteristics, as being an application to the lean premixed combustion technology, have been investigated. The study has been conducted at the conditions of high temperature and high pressure. Theair from a compressor with the pressure of 2.5bar, 3.0bar, 3.5bar was supplied to the combustor with the temperature 560K through the air preheat-treatment. The sampling exhaust gas was measured at the immediate exit of the combustor. For the effect of temperature on NO and CO emissions, though NOx were increased, CO was decreased with increasing inlet air temperature. With increasing inlet air pressure, NOx were increased and CO was decreased also. NOx were decreased, but CO was increased with increasing inlet air mass flow rate. The test has been performed on the equivalent ratio of 0.10 to 0.16 in the lean region. NOx were increased with increasing equivalent ratio, but CO was decreased as an influence of flame temperature. CFD work with an appropriate combustion model predicated a complicated swirling flow pattern in the combustor, and also produced a numerical value of NOx and CO emissions which was to be compared with the experimental one. As the results of this study, NOx are expected to be reduced to less than 42ppm at 15% O2 when operated at the design condition of the 20kW class microturbine.

The steam turbine efficiency is an important factor in power plant. Accurate evaluation of steam turbine performance is essential. However, it is not easy to evaluate the steam turbine performance due to its high temperature and high pressure circumstance. Therefore most steam turbine performance tests were conducted by air similarity test. This paper described a test program for air similarity test of steam turbine at Korea Aerospace Research Institute. A test facility has been designed and built to evaluate aerodynamic performance of turbines. The test facility consists of air supply system, single stage test section, power absorption system, instrumentation and auxiliary system. For evaluation of steam turbine performance, the test of single stage axial turbine air similarity performance was conducted and uncertainty analysis was performed.

Micro gas turbines are designed with low turbine inlet temperature and pressure ratio. To overcome the efficiency defect of the simple cycle, adoption of the recuperator is an inevitable choice. In addition to the design performance, we should also pay attention to the off-design performance of gas turbines since they usually operate at part-load conditions for a considerable amount of the time. This study aims at analyzing off-design performance characteristics of micro gas turbines and addressing the importance of the recuperator in the part load operation. Comparative analyses have been performed to evaluate the part load performance differences among various design and operating options : simple vs recuperative cycles, single vs two shaft configurations, various operating strategies for the single shaft configuration (fuel only control, variable speed operation, variable inlet guide vane control), and current vs advanced engines. Major finding is that maintaining turbine at high level is crucial in efficient operation of micro gas turbines.

A fuel spiking test was performed to measure the surge margin of gas turbine engines. The surge marin was mainly determined by the compressors and fuel spiking was used to change the operating point in the compressor characteristic map while speed remained constant. To access the surge margin region different spiking signals were applied by modulations of time(frequency) and fuel flow rate(amplitude). The test results showed good agreements with expected fuel spiking patterns and possibility of further studies.

Turbine blades experience significant surface degradation with service. This paper presents experimental evidence of blade surface roughness reducing turbine efficiency. Performance tests were conducted in a low speed, single-stage axial flow turbine rig with roughened blade surfaces. Sheets of sandpaper with equivalent sandgrain roughnesses of 106 and $400{\mu}m$ were used to roughen the blades. In these tests, effects of roughened stator vanes and rotor blades were separately evaluated. In the fully rough regime ($k_{s}=400{\mu}m$), the experimental results show an 11 percent decrease in normalized efficiency with roughness only on stator vanes ; an 8 percent decrease with roughness only on rotor blades ; and a 19 percent decrease with roughness on both the stator and rotor blades. In the transitionally rough regime ($k_{s}=106{\mu}m$), the trends are similar approximately 4 percent decrease with either roughened stator or roughened rotor and an 8 percent decrease with roughness on both stator and rotor blades. Thus, roughened stator vanes incur more performance penalty than roughened rotor blades.

In this work, mixing phenomena in the mixing chamber of a ultrasonic micromixer are analyzed through an analytical approach. A simplified 2-dimensional model for the ultrasonic micromixer is presented. Analytical solutions for fluid flow induced by ultrasonic waves are obtained through successive approximations method. From simulation results on thermal diffusion in the mixing chamber, effects of relative location, size, and vibration frequency of a piezoelectric material and aspect ratio of the mixing chamber on mixing performance of the ultrasonic micromixer are investigated. Finally, design guidelines for the ultrasonic micromixer are suggested based on the parametric study.

The influence of property difference in refraction index on micro PIV measurement of two-fluid flow in a microchannel was analyzed. The difference of measurement planes in two fluids would bring misunderstanding of the physics. The objective-imaging system for two-fluid flow measurement was presented, and the condition for measurement of valid velocity profile across two-fluid interface was derived. A micro PIV experimental system was set up to measure two-fluid flow inside a Y-shape microchannel. Under the conditions, three cases of two-fluid flow of glycerol solutions at different concentration (${\phi}$), e.g., (${\phi}=0\;and\;{\phi}=0.2,\;{\phi}=0.1\;and\;{\phi}=0.5,\;{\phi}=0\;and\;{\phi}=0.6$, were measured. Close agreement of experimental and numerical results was found.

In this work, a continuous-flow micro-PCR system is systematically designed. From the numerical simulation based on the finite volume method, adapting oneself to a new environmental temperature without an external temperature controller is shown to be possible and a cooler as well as a heater is shown to be necessary to obtain three individual temperature zones for polymerase chain reaction. In addition, appropriate geometry of a heat sink for the cooler is determined by using a compact modeling method, the porous medium approach.

Micromixer plays an important role in Bio-MEMS or ${\mu}-TAS$. Mixing is generally generated by turbulence and interdiffusion of two fluids. Because of low Reynolds number(Re << 2000) in ${\mu}-channel$, it is difficult to generate turbulence, so mixing mainly depends on interdiffusion. Thus long channel distance is required to mix two different fluids. To reduce the channel length required for mixing, we propose the a new active ${\mu}-mixer$ that two fluids are effectively mixed in ${\mu}-channel$ by the ultrasonic wave which is generated by PZT. The ultrasonic wave is radiated into a chamber in the cross-section directional direction to interface with the two fluids. The two fluids are positioned one on top of the other. Mixing state is measured by the changing of color due to the reaction of NaOH and phenolphtalein.

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This study was experimentally performed in order to estimate the errors due to the leakage of transmitter gaugelines in the orifice flow meter for natural gas. It would be a serious problem in safety if a large quantity of leak was occurred at the tubes or fittings like valve. But in most cases the safety problems might be rarely happened because the gas leak detectors could be operated in advance and the various kinds of inspection would be also fulfilled periodically. If the leakage was occurred continuously with an undetectable amount at the gaugelines for measuring the pressure or the differential pressure(DP), the amount of leakage might be an error or an unaccounted flow(UAE). In addition if the measuring value of pressure or DP were affected by the leakage, it might also be a measurement error. The experiments were performed to estimate the amount of leakage and to check the DP changes if it exited. First, through the measurement of the air pressure changes in the airtight container connected to a transmitter with gaugelines as the time passed, the amount of leakage causing from the fittings of gaugelines was roughly estimated. As changing the leak position of the gaugeline, the leak was intentionally made to break out. The variance of DP was checked as controlling the extent of leakage and compared to no leak conditions. Consequently, under the normal maintenance conditions, the result represented that the amount of leakage causing from the gaugelines was insignificant and also the DP changes on leakage conditions were too small to cause the errors of measurements.

As the fastest growing flowmeter technology, multi-path ultrasonic flow-meters are gaining wider range in petroleum industry for liquid hydrocarbon custody transfer measurement. This paper describes the mult-path ultrasonic flowmeter, URO-Ex1000 the requirements necessary to prove and test in Korea & China. URO-Ex1000 haver a good results with accuracy range, but a little exceed with repeatability.

Multi-path ultrasonic flowrate measuring technology is being received much attentions from a variety of industrial fields to exactly measure the flowmeter. Multi-path ultrasonic flowmeter has much advantage since it has no moving parts and not occurred pressure loss. It offers good accuracy, repeatability, linearity and Tum-down ratio can measure over 1:50. The present study investigates flowrate integration errors using weighting factors. A theoretical flow model uses power law to describe a fully developed velocity profiles and wall roughness changes. The methods of weighting factor simulate three configurations of measuring location of gaussian, chebyshev and tailor method. The obtained results show that many chord arrangements are not affected for wall roughness changes and can measure accurate flowrate.

It is the common features of the integral reactors that the main components of the RCS are installed within the reactor vessel, and so there are no any flow pipes connecting the coolant pumps or steam generators. Due to no any flow pipes, it is impossible to measure the differential pressure at the RCS of the integral reactors, and it also makes impossible measure the flow-rate of the reactor coolant. As a alternative method, the method by the measurement of coolant pump power has been introduced in this study. Up to now, we did not found out a precedent which the coolant pump power is used for the real-time flow-rate calculation at normal operation of the commercial nuclear power plants. The objective of the study is to embody the real-time flow-rate calculation method by the measurement of coolant pump power in an integral reactor. As a result of the study, we could theoretically reason that the capacity-head curve and capacity-shaft power curve around the rated capacity with the high specific-speeded axial flow pumps have each diagonally steep incline but show the similar shape. Also, we could confirm the above theoretical reasoning from the measured result of the pump motor inputs, So, it has been concluded that it is possible to calculate the real-time flow-rate by the measurement of pump motor inputs. In addition, the compensation for a above new method can be made by HBM being now used in the commercial nuclear power plants.

For the measurement of mass flow rate at a wide range of operation conditions, it is required that the critical nozzle gas different diameters, since the mass flow rate through the critical nozzle depends on the nozzle supply conditions and the nozzle throat diameter. In the present study, both computational and experimental investigations are performed to explore the variable critical nozzle. Computational work using the 2-dimensional, axisymmetric, compressible Navier-Stokes equations are carried out to simulate the gas flow through variable critical nozzle. In experimnet, a cylinder with several different diameters is inserted into the critical nozzle to vary the nozzle throat diameter. Computational results are compared with the experimented ones. The computed results are in close agreement with experiment. It is found that the displacement and momentum thickness of variable critical nozzle are given as a function of Reynolds numbers. The discharge coefficient of the variable critical nozzle is predicted using an empirical equation.

The automatic temperature control valve is used to control the flow rate of heating water in the large apartment complex and buildings. It is important to have simillar heating flow rate in the apartments, even though the apartment is top or bottom floors. To achieve those purposes, the automatic flow-temperature control valve was developed. The perfromance of this control valve is effected by the catridge shape and spring length. The flow capacity of this control valve is obtained with the different shape of catridges and with change of spring length.

A numerical study has been conducted to investigate the effect of an inlet flow pulsation on mixing of two solutions with different concentrations in a micro conduit. We treat an unsteady, incompressible and two-dimensional flow through a micro conduit by adopting the momentum equations with the electrostatic force due to streaming current and the concentration equation. The feasibility of the inlet flow pulsation to enhance the mixing process inside the micro conduit is carefully examined by varying the inlet pulsation frequency. When a low-frequency pulsation is induced at the inlet, the interface between two solutions with different concentrations becomes wavy, which results in mixing enhancement. As the pulsation frequency increases, the waviness of the interface becomes meager, and the concentration gradients at the interface approach the value for the non-pulsating steady flow.

An experimental study was performed to examine the heat transfer performance of individual rows of fin-tube heat exchangers. The heat transfer performance was measured using air-enthalpy type calorimeter. The examined heat exchangers consists of $7{\Phi}$ tube and fin patterns of them are slit and louver types. Equivalent fin spacing are 18 FPI for all samples, and the number of tube rows were 2. In order to confirm that thermal boundary condition on fins of each row are the same, physically separated between two rows as well as connected heat exchangers were used. The frontal air velocity varied from 0.7 to 2.5 m/s. Heat transfer performance for each row are measured. It was observed that the heat transfer coefficient of the 2nd row were smaller than that of the 1st row at low Reynolds number while larger at high Reynolds number.

In order to control indoor air quality and save energy, it is needed to install a suitable ventilation system equipped with heat exchanger for heat recovery. The purpose of this research is to find the performance of paper heat exchanger for exhaust heat recovery, which exchanges latent heat as well as sensible heat. Experimental apparatus comprises heat exchanger model, constant temperature and humidity chamber, fan and measurement systems for temperature, pressure and flow rate. Thermal performance and pressure loss of the paper heat exchanger are measured and compared at various air velocities and outdoor conditions. Experimental results show that paper heat exchanger can recover $50{\sim}70%$ of the enthalpy difference between supply and exhaust air.

The detailed flow characteristics inside a compression chamber due to the orbiting motion of a scroll is studied numerically. The orbiting motion of a scroll is modelled at 7 orbiting angles. At each orbit angle, the central compression chamber is modelled. All computations are carried by using an in-house code. It is based on the SIMPLE algorithm. Computation results show that the flow structure inside the compression chamber is dependent on the orbit angle. The pressure variation inside the compression chamber also shows great dependence on the orbit angle. The pressure variation shows local maxima when the orbiting motion of a scroll directs toward the center of the compression chamber.

This research inspects discharge state of inside of sedimentation basin, md, through the aboard literature and data, examine sedimentation sludge about discharge plan of effective sedimentation sludge that can discharge in state of high concentration.

A generation rate of sludge in Korea had increased dramatically about 200 % for a decade. A requirement for high efficiency dewatering system being possible to produce the low water content cake have suggested due to the appearanceof commercial and social problems about handling of dewatered cake. The conventional dewatering system with mechanical compression device was not suitable to produce the low water content cake and didn'tcope with lots of requirements. Therefore, this paper was to develop the high efficient filter press with the compressive and heating forces through the heating plate to be built between membrane filter plates. It is possible to produce the low water content cake and improve the dewatering rate, so this equipment positively coped with several types of problems related to the sludge dewatering. The plate heated by heat transfer materials such as steam, hot water and thermo-oil made the sludge make the residual moisture within the cake to discharge easilyand to improve the dewatering efficiency of equipment. The pilot scale experiment with 500kg of cake production showed that the dewatering efficiency determined by the final water content and dewatering velocity was improved 30% more than the conventional dewatering equipment.

High-efficiency turboblowers in the next generation have been successfully developed and commercialized first in the world, using the high-speed BLDC motors and the foil air bearings. About 20-35% savings in electricity consumption in the field are found in comparison with the conventional roots rotary blowers and the integral gear-driven turboblowers. Current TB75 and TB150 products are replacing the existing blowers in the worldwide market.

High performance turbo compressor, Turbo Master, was successfully developed by applying combined technology and experience based on aero gas turbine engines. The Turbo Master, developed using our own technology, was designed for high performance and reliability And the Turbo Master will supply absolutely oil-free compressed air to your facilities. In special, a next-generation micro compressor was lately developed, using air foil bearing and high speed motor known as the latest high technology.

Many recent development activities suggest the possibility of a high-speed turbo(centrifugal) compressor or blower for the industrial application of compressed air supplying system when used with the most advanced high-speed motor, inverter technology, and advanced bearing for high rotational speed. The problems to be overcome are of reliability, the application of mass production methods, cost effective manufacture and competitive running costs. This presentation is not focused on a specific technology advances but on an overall review of our recent experiences while we have developed the high pressure turbo blower for the commercial purpose.

Asynchronus high speed turbo blower of 100HP class with gas bearing supports is developed. The high speed motor is cooled by air and it's RPM is controlled by high frequency inverter to adjust inlet flow rate. Product family is ranged from 50 to 200HP and covered by three frames. Highly efficient impeller is designed and proved by performance test on system. Overall measured system efficiency is 82% including motor and inverter. The motor efficiency is about 95%. It is designed to guarantee to operate at ambient temperature of 35 Deg.C and max 45 DegC. Gas bearing with high load capacity is developed to support heavy rotor on low rotational speed.

Steady and unsteady cavitation characteristics of turbopump inducer were investigated in this paper. To see the effect of blade angle on the inducer performance, three inducers with inlet tip blade angle of $7.8^{\circ},\;7.0^{\circ},\;6.1^{\circ}$, respectively, were tested. For $7.8^{\circ},\;7.0^{\circ}$ inducers in the non-cavitating condition, head decreased linearly with flow rate, but head-flow rate curve had a dip at the flow coefficient ${\Phi}=0.065\;for\;6.1^{\circ}$ inducer. Rotating cavitation and cavitation surge were found in the $7.8^{\circ},\;7.0^{\circ}$ inducers in the cavitation tests. During the rotating cavitation one cell rotated at the same rotational speed as that of the inducer. The cavitation surge did not rotate and the oscillating frequency was $7{\sim}20\;Hz$. From the curve of the critical cavitation number versus flow rate, it was found that the steady cavitation performance of $6.1^{\circ}$ inducer was much lower than that of $7.8^{\circ},\;7.0^{\circ}$ inducers.

Cryogenic turbopump test facility(CTTF) is designed and developed. Hydraulic and cavitation performance of turbopump in cryogenic environment can be measured. Working fluid is liquid nitrogen and operating temperature is $-197^{\circ}C$. Liquid nitrogen run tank, catch tank and pressurizing tank has been built and remote tank pressure control system are installed. Maximum power of turbopump is 320kW and its maximum speed is 32000rpm. Cryogenic fluids and lubricating systems are effectively separated that long test times are acquired. Therefore hydraulic and cavitation performance can be measured accurately and effectively. This facility will contribute greatly to the development of turbopump for KSLV.

The study was performed to search on alternative material for turbopump parts made of Russian material by analyzing and comparing chemical and mechanical material properties. Iron base material was generally used for turbopump. This material can be categorized into stainless steel and heat resisting steel by quantity of additional elements. Each steel was also classified into austenite steel, ferrite steel, and martensite steel. Alternative materials for turbopump inducer, impeller and casing are chosen by JIS SUS 631 and 321 as a result of this study. Because the material of Russian turbopump turbine may be developed by Russia itself, alternative material can be hardly found. However, Inconel 718 for turbine material is thought to be proper in the aspect of hardness considering general use of this material for turbopump turbine in Japan and France.

Hydraulic performance and cavitation characteristics of fuel pump in turbo-pump were studied experimentally. The fuel pump has a centrifugal impeller with a separate inducer. In this paper, flow characteristics of inducer and impeller was experimentally investigated separately and together. Especially static pressure distribution of Inducer was examined in non-cavitation and cavitation conditions.

For regenerative pump performance test we made 5 times enlarged and 3 different kinds blade types impeller with similarity. Due to geometrical characteristic of regenerative pump, there are two kinds of groups which effect on performance of it. One is geometric shape of impeller blade and the other is clearance and inlet/outlet head loss. To study performance of regenerative pump with impeller shape changes, we tested it with reducing clearance. And we reconcile performance data in the case of zero clearance and zero inlet/outlet head loss. Finally we could verify the influence of each group.

In this study the effects of fluid viscosity on the pump performances of a conventional centrifugal pump were experimentally studied. The study aimed to compare the pump characteristics for water and high viscosity fluids. The Working fluids are water, aqueous sugar solution and glycerin solution. The pump characteristics of total head and efficiency with high viscosity fluids were different. The performance curves of efficiency for the sugar and glycerin solutions were decreased up to 8.1% and 12.9% than that of water.

In this paper, build up of fan performance tester in KITECH was introduced. The fan tester was set up based on AMCA standards 210-99, ANSI/ASHRAE 51-1999 with maximum flowrate within $1000\;m^{3}/min$. Both of inlet and outlet chamber setup with multiple nozzles described in AMCA 210 were established. The development of fully automatic control and measurement system are described. With this system, the accuracy of fan performance test can be maintained through the various flowrate and the uncertainty can be reduced.

A turbo blower directly driven by a variable-speed BLDC motor was designed and tested to investigate performance characteristics. Computational analysis and performance tests validated the design method for the present turbo blower. Experimental measurements showed that the blower has an enough stability margin. This paper gives an outline of design, computational flow analysis and performance test for aerodynamic performance of the blower

Shape of a multi-blades centrifugal fan is optimized by response surface method based on three-dimensional Navier-Stokes analysis. For numerical analysis, Reynolds-averaged Wavier-Stokes equations with standard $k-{\varepsilon}$ turbulence model are transformed into non-orthogonal curvilinear coordinate system, and are discretized with finite volume approximations. Due to the large number of blades in this centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models for economic calculations. Optimizations with and without constraints are carried out. Design variables, location of cur off, radius of cut off, expansion angle of scroll and width of impeller were selected to optimize the shapes of scroll and blades. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, the efficiency was successfully improved. The correlation of efficiency with relative size of inactive zone at the exit of impeller is discussed as well as with average momentum fluxes in the scroll.

A cross-flow fan relatively produces higher dynamic pressure at low speed because a working fluid passes through an impeller blade twice and blades have a forward curved shape. The performance of a cross-flow fan is influenced 25% by the impeller, 60% by the rearguider and the stabilizer, and 15% by the heat exchanger. At the low flow rate, there exist a rapid pressure head reduction, a noise increase and an unsteady flow against a stabilizer and a rearguider. The purpose of this study is to investigate the reciprocal relation among each parameter Experiments are conducted to study the effects of a rearguider and a diameter ratio of impeller on the performance analysis of a cross-flow fan. Comparing with the rearguider of radial type, the Archimedes type shows excellent results for various diameter ratios.

In an attempt to solve multiobjective optimization problems, weighted sum method is most widely used for the advantage that a designer can consider the relative significance of each object functions by weight values but it can be highly sensitive to weight vector and occasionally yield a deviated optimum from the relative weighting values designer designated because the multiobjective function has the form of simple sum of the product of the weighting values and the object functions in traditional approach. To search the design solution well agree to the designer's weighting values, we proposed new multiobjective function which is the functional of each normalized objective functions and considered to find the design solution comparing the distance between the characteristic line and the ideal optimum. In this study, proposed multiobjective function was applied to design high efficiency and low noise axial flow fan and the result shows this approach will be effective for the case that the qualify of the design can be highly affected by the designer's subjectiveness represented as weighting values in multiobjective design optimization process.

Three-dimensional vortical flow and separated flow topology near the casing wall in an axial flow fan having two different tip clearances have been investigated by a Reynolds-averaged Wavier-Stokes (RANS) flow simulation. The simulation shows that the tip leakage vortex formed close to the leading edge of the blade tip on suction side grows in the streamwise direction. On the casing wall, a separation line is formed upstream of the leakage vortex center due to the interference between the leakage vortex and main flow. The reverse flow is observed between the separation line and the attachment line generated downstream of the trailing edge, and increased with enlarging tip clearance. The patterns of a leakage velocity vector including a leakage flow rate are also analyzed according to two tip clearances. It is noted that the understanding of the distribution of a limiting streamline on the casing wall is very important to grasp the characteristics of the vortical flow in the axial flow fan.

Sedimentation phenomenon of suspended solids occurs by the gravitational force. Pollution particles are separated from slowly flowing wastewater in clarifier. Recently, the sludge suction collector is preferred rather than the scraper type sludge collector due to enhancement of the clarifier efficiency. The sludge suction collector is usually operated by the user's experiences without any scientific and/or technical consideration. To evaluate the performance of sludge suction collector, the three dimensional computer simulation was conducted by the finite volume method. To analyze the performance, the velocity vectors and the suction flow rates of the orifices were investigated. The result showed that each suction flow rate through out the collector was equivalent in the sludge suction collector and the efficiency of suction collector was good to remove high concentrated sludge in clarifier.

Recently, mixers are being widely used in the water purification plant in order to increase the filtration efficiency. The mixer normally consists of impeller, shaft, hub, reduction gear, and the driving motor. It is one of the key design issues to confirm that the vibration caused by the rotation of the shaft should not coincide with the natural vibration frequency of the shaft itself. The vibration characteristics of the hydrofoil type mixer, which is the most widely used in real plants are evaluated through the finite element modeling and verified by experiment using the mock-up facility. The fundamental natural frequency of the mixer's shaft is found to be around 1.8 Hz which showed in good agreement with the experiment. The higher natural frequencies to the 2nd, 3rd, and 4th modes are also verified by the experiment. Thus the developed model is to be utilized for the structural design of the real mixer system.

The Mixers is used for the Mixing which is the most important process in the Water&Sewage water treatment. To choose proper mixer required much career and knowledge, to check many elements which are purpose, time and condition of mixing. Thus, the design method of mixers is to be utilized for the structural design of the water & Sewage water treatment.

In this study, the overall performance and the effect of the tip leakage flow of the centrifugal compressor with the refrigerant HFC-l34a were numerically studied using CFX-TASCflow. To study the effect of a tip leakage flow, the numerical study of the overall performance of HFC-l34a centrifugal compressor with a cascade diffuser was preceded and compared with experimental result. Six different tip clearances were used to consider the influence of a tip clearance on performance. The tip leakage flow was illustrated for qualitative discussion. The results obtained in this study can be applied to the determination of the cold clearance.

A general program of meanline design and/or performance prediction for centrifugal/mixed-flow compressors is successfully commercialized using various empirical loss models. 4 types of diffusers, 3 types of exit elements, shrouded/unshrouded impellers and real gas option are included in the program capabilities. Total 16 cases of benchmark test results proved its reliability to be effectively utilized in the development processes.

A general program of three dimensional profile design of impellers for centrifugal/fixed-flow compressors is successfully commercialized using Bezier curves and quasi-3D flow analysis methods. Control points for meridional hub and shroud contours and blade camberline angles are arbitrarily changed to give smooth Bezier curves. With specified blade normal thicknesses, contructed geometry is instantly analyzed using flow analysis methods to be checked.

The performance of a centrifugal compressor composed of an impeller, tandem diffuser rows and axial guide vanes has been predicted numerically and compared with available experimental results on its design rotational speed. The pitchwise-averaged mixing plane method was employed for the boundaries between rotor and stator to obtain steady state solutions. The overall characteristics showed differently according to the relative positions of tandem diffuser rows while the characteristics of impeller showed almost identical. The numerical results agree with the measured data in respect of their tendency. It turned out that 0% of relative positions is the worst case in terms of static pressure recovery and efficiency. According to the experimental results, some pressure fluctuations and malfunction of the compressor were observed for 75% case. However, this numerical calculation using mixing plane method did not capture any of those phenomena. Thus, unsteady flow calculation should be performed to investigate the stability of the compressor caused by different diffuser configuration.

In this paper, the effect of circumferential inlet distortion on performance and stall has been experimentally investigated in a high-speed centrifugal compressor, comparing distorted cases with undistorted one. The performance of compressor was slightly deteriorated by defect of inlet static pressure which is caused by the circumferential inlet distortion. As stall was fully developed the inlet distortion did not affect the number of stall cell and the propagation velocity. It also did not affect stall inception at 40,000 and 50,000 rpm. However stall occurred at the lower flow rate for distorted flow at 60,000 rpm. For 50,000 rpm a unexpected phenomenon occurred : stall occurred first and then it disappeared.

A high-efficiency turbo steam compressor has been successfully developed for the MVR desalination system, first one in Korea. The state-of-the-art design methods using real gas properties were applied to get all the aerodynamic design results. Bull and pinion gear trains, tilting-pad bearings and investment cast impellers were developed also to be integrated into the integral gear-driven turbo steam compressor. System tests show highly efficient performance.

A high performance and low noise refrigerator fan has been developed in order to satisfy the customer's high quality needs, that is, luxury, big size and low noise. In this study, the characteristics of a new developed fan and a current fan was calculated and compared by using numerical simulation. Rotation of a fan makes cold air circulation inside a refrigerator. A numerical simulation of air flow shows distribution and local flow regime of a cold air flow circulation, and revealed a cause of low noise as well. Optimization of a duct shape also decreased noise level.

Reynolds averaged Wavier-Stokes simulations based on the Reynolds stress model was performed to investigated the effect of inlet flow angle on the distributions of the Reynolds stress tensor inside tip leakage vortex of a linear compressor cascade. Two different inlet flow angles ${\beta}=29.3^{\circ}$(design condition) and $36.5^{\circ}$(off-design condition) were considered. Stress tensor analysis, which transforms the Reynolds stress into the principal direction, was applied to show an anisotropy of the normal stresses. Whereas the anisotropy was highest in the region where the tip leakage vortex collides the suction side of the blade and tip leakage flow enters between blade tip of the pressure side and the endwall, it had the lowest value at the center of tip leakage vortex. It was also found that the magnitude of maximum shear stress at design condition was greater than that of off-design condition.

The HANARO, multi-purpose research reactor, 30 MWth open-tank-in-pool type, is under normal operation since it reached the initial critical in February 1995. The HANARO is used for fuel performance tests, radio isotope productions, reactor material performance tests, silicone semiconductor productions and etc. Specially, the HANARO is planning to produce a fission moly-99 of radio isotopes, a mother nuclide of Tc-99m, a medical isotope and is under developing a target handling tool for loading and unloading those at a flow tube (OR-5). The target should be sufficiently cooled in the flow tube without an interference with the cooling of the others and an induction of extremely vibration. This topic is described an analectic analysis for the cooling characteristics of the fission moly-99 target to find the minimum cooling water. It was confirmed through the analysis results that the minimum cooling water, about 2.717 kg/s flew through the flow tube under the worst case that the guide tube got no perforating holes for cooling water to pass through the holes and that the target was safely cooled under about seventy percent (70%) of the maximum allowable temperature of the target.

A quick injection agitator is used to mix working fluids. In this study, numerical analyses are carried out to investigate the performance of a quick injection agitator with different gaps between the impeller and vacuum enhancer. A commercial CFD code is used to compute the 3-D viscous flow field within the impeller of agitatior. Numerical results are graphically depicted with different gaps. Special attention is paid to the following topics: pressure distribution, velocity gradient, volume fraction.

The objective of this study is to document the secondary flow and the total pressure loss distribution in the contoured endwall installed linear turbine nozzle guide vane cascade passage and to propose an appropriate contraction ratio of the contoured endwall which shows the best loss reduction among the simulated cases. In this study, three different contraction ratio of contoured endwalls have been tested. This study was performed by experimental method and when the contoured endwall has the contraction ratio of 0.17 on exit height the results showed the best loss reduction.

A numerical investigation was performed to determine the effect of airfoil on the optimum flap height using NACA0015 Wells turbine. The five double flaps which have 0.5% chord height difference were selected. A Wavier-Stokes code, CFX-TASCflow, was used to calculate the flow field of the Wells turbine. The basic feature of the Wells turbine is that even though the cyclic airflow produces oscillating axial forces on the airfoil blades, the tangential force on the rotor is always in the same direction. Geometry used to define the 3-D numerical grid is based upon that of an experimental test rig. This paper tries to analyze the optimum double flap of Wells turbine with the numerical analysis.

Comprehensive study on the system, including blower and ducts, of HVAC device of a vehicle has been carried out for improvements of noise characteristics. The parameters of design improvements are concerned with geometric informations such as the shape of ducts and presence of a windshield window. Test results show that noise level increasing the following order: HV (HD) < V (D) < BH ${\sim}$ BHV (BHD) < B (B, H, V, D denote for blower, heater unit, vent duct, defrost duct, respectively). The effects of windshield glass on the noise level in the case of defrost mode are pronounced and the effects of the geometry of ducts on the overall HVAC noise prove to be not small.

In this Paper, a LON based distributed control system for HVAC is described. We developed multi-protocol converter based on SoC, Neuron Chip, embedded Linux. It utilizes the network environment and therefore requires an appropriate operating system for handling protocols and an advanced development environment. The open source licensing, reliability, and broad hardware support are key reasons for use of embedded Linux in embedded industry. The multi-prootocol converter integrates LonWorks devices to a client with Java applet. The system consists of three-tier architecture, such as clients, multi-protocol converter, and LonWorks devices. The experiment result show that multi-protocol converter using embedded Linux is a flexible and effective way to build a Web-based monitoring and control system.

Activated carbon was prepared from coffee wastes by chemical activation with $ZnCl_{2}$, NaOH and KOH. The coffee wastes was used as raw material. Preparation process involves the roasting of raw material and carbonization of roasted material followed by chemical activation. N2-BET surface areas of activated coffee char prepared by chemical activation was measured as $1,110{\sim}2,442m^{2}/g$. Removal of copper and chromium in solution by activated carbon was carried out and structural change of pore surface was observed by SEM.

EPRI PPM (Performance Prediction Methodology), a method used for the prediction of required thrust of valves, can not be applied to unbalanced-disk globe valves operated in the fluid when the fluid temperature is above $150^{\circ}F$ because the thrust increase caused by the friction between the valve disk and body is not considered in the PPM. In order to apply PPM to the valves, EPRI suggested new friction prediction method to be added in the code. This paper analyzes the applicability of the prediction method comparing the disk-to-body friction load predicted from the method with the measured friction load from the field tests. The maximum values from the prediction method and those obtained from the test were 268lbs and about 1500lbs, respectively. It is included that the prediction method should be improved for the realistic prediction of disk-to-body friction load.

The experimental apparatus is designed and installed to measure the disc positions with flow velocity, $V_{open}\;and\;V_{min}$ for 3 inch and 6 inch swing check valves. The minimum flow velocity necessary to just open the disc at a full open position is referred to as $V_{open}\;and\;V_{min}$ is defined as the minimum velocity to fully open the disc and hold it without motion. In the experiments, $V_{min}$ is determined as the minimum flow velocity at which the back stop load begins to increase after the disc is idly opened or the oscillation level of disc is reduced below $1^{\circ}$. The results show that the $V_{min}$ velocities for 3 inch and 6 inch swing check valves are about 15.6% and 4.8% higher than the $V_{open}$ velocities, respectively. Although the experiments were done with the stable uniform flow, additional experiments will be performed to determine the effects of the upstream disturbances.

This paper presents the method of Rate of Loading(ROL) improvement for the Motor Operated Gate Valve operating in high differential pressure condition. The character of ROL and Stem Factor is analyzed. Static test and dynamic test were performed and acquired the diagnosis signal for the valve closing stroke. The result of this study is the modification of stem factor is very important factor for the ROL improvement. In order to obtain the same value of dynamic test thread friction coefficient stem and stem nut should be combined appropriately.

The height of valve body is limited to 30mm in the cook-top style gas valves for the domestic gas ranges. But the all the safety specifications of KS should be fulfilled and the magnetic power unit(MPU) should be installed in the valve body for the safety reason. The length of MPU body is longer than the 30mm that it should be located in the square direction of the knob shaft and therefore the implementation of the lever mechanism to transmit the press motion of the knob to the MPU valve is very difficult. In this paper, the hinged lever with inclined plate is used to transmit the press motion of the knob to the MPU valve. The analysis of the gas flow with using the commercial software of FLOW-3D shows that the gas flow capacity is fit for the domestic gas range. The performance and responsibility of the valve is tested for the mass production and the test results shows that the valve can be installed in the commercial gas range.

In butterfly control valve, a multi-hole orifice is attached downstream of valve to stabilize flow fluctuation. The computational simulation is conducted to analyze valve flow characteristics. The results show that the velocity distribution of downstream of valve with the orifice is improved compared to non-orifice case. Test result in site is 60% reduction in vibration.

In generally, under the influence of over-pressure drop, serious problems such as cavitation, choked flow, flashing and vibration has been coming around the tilting disk check valve. A PIV experiment to examine the cause of energy loss has been performed and the improvement configuration of valve seat based on this visualization results is proposed. In the visualization results, flows in the piping system became instability under the influence of the shape of boss. This unstable flows induces sudden pressure drop in the piping system. So, we change the configuration of boss as a streamlined design to be stabilized the flows. A pressure measurement has been performed to know that the influence of the configuration change. In result, the rate of pressure loss reduction is about 22% at the position of No. 2 and 24.2% at the position of No. 6 in comparison with pre-improved shape.

This paper is concerned with the numerical analyses of an S-shaped duct for the inter-channel between compressor spools. For the compactness and lightweight of an engine, the length of the S-shaped duct is desired to be minimized. Shortening the S-shaped duct however, flow separation is likely to occur. Numerical investigation using a three-dimensional Navier-Stokes flow solver has been performed to determine the availability of the minimization of an S-shaped duct. Computations are performed introducing the experimental data as the inlet flow condition of the OGV in determining the minimum length of the S-shaped duct. Also, the leaning effect of the OGV which assists the flow to turn radially inward are studied adopting mixing-plane method to consider the rotor/OGV interaction.

This work presents a numerical procedure to optimize the shape of three-dimensional channel with angled ribs mounted on one of the walls to enhance turbulent heat transfer. The response surface method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of flow and heat transfer. SST turbulence model is used as a turbulence closure. The width-to-height ratio of the rib, rib height-to-channel height ratio, pitch-to-rib height ratio and attack angle of the rib are chosen as design variables. The objective function is defined as a linear combination of heat-transfer and friction-loss related terms with weighting factor. D-optimal experimental design method is used to determine the data points. Optimum shapes of the channel have been obtained for the weighting factors in the range from 0.0 to 1.0.

The wind turbine blade is the equipment converted wind into electric energy. The effect of the blade has influence of the output power and efficiency of wind turbine. The design of blade is considered of lift-to-drag ratio, structure, a condition of process of manufacture and stable maximum lift coefficient, etc. This study is used the simplified method for design of the aerodynamic blade and aerodynamic analysis used blade element method. This process is programed by delphi-language. The program has any input values such as tip speed ratio, blade length, hub length, a section of shape and max lift-to-drag ratio. The program displays chord length and twist angle by input value and analyzes performance of the blade.

Design optimization of a transonic compressor rotor (NASA rotor 37) using response surface method and three-dimensional Navier-Stokes analysis has been carried out in this work. Baldwin-Lomax turbulence model was used in the flow analysis. Two design variables were selected to optimize the stacking line of the blade, and mass flow was used as a design variable, as well, to obtain new design point at peak efficiency. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, adiabatic efficiency was successfully improved, and new design mass flow that is appropriate to an improved blade was obtained. Also, it is found that the design process provides reliable design of a turbomachinery blade with reasonable computing time.

Load calculation is indispensable for the construction of a large wind turbine generator system (WTGS). In procedures of load calculation, all conditions affecting to WTGS such as environment of site, operation, transport and installation have to be considered systematically. So the certification of WTGS is issued by assuring the load calculation. This work shows the generals of load calculation briefly and introduces the characteristics and results of load calculations for the 750 kW direct-drive WTGS (KBP-750D) which is under development by the consortium of POSTECH and UNISON.

Modem reciprocating air compressors have tendency to a multi-stage W-type or V-type cylinder arrangement for the purpose of high outlet pressure, compactness and low vibration and noise. A valid counter weight calculation method using the complex expression is proposed for reducing the inertia forces of the compressor. Counter weight removes only 1st forward whirl component. Counter weight formulations are applied to the six various compressor structures which are (a) 1 cylinder single-throw crank shaft, (b) 2 cylinder single-throw crank shaft (c) 2 cylinder double-throw clank shaft, (d) 3 cylinder single-throw crank shaft, (e) 4 cylinder single-throw crank shaft and (f) 4 cylinder double-throw crank shaft. The improvement of performance is verified through available vibration test.

This paper presents a performance analysis of the 1st generation bump foil journal bearings for the micro gas turbine TG75. Static performances such as load capacity and attitude angle are estimated by using soft elasto-hydrodynamic analysis technique, and dynamic performances such as stiffness and damping coefficients are estimated by perturbation method. Rotordynamic analysis for TG75 is performed by using the bearing analysis results. TG75 rotor has 2 horizontal and vertical directional natural modes due to the bearing stiffness characteristics. TG75 rotor will be stably operated between the 1st bending mode at 33000cpm and the 2nd bending mode at 85500cpm. Unbalance response analysis results satisfy the API vibration criteria.

Two-dimensional direct numerical simulation of the edge-tones by the finite difference lattice Boltzmann method (FDLBM) is presented. We use a new lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing the conventional FDLBM, and also use a boundary fitted coordinates. We have succeeded in capturing very small pressure fluctuations result from periodically oscillation of jet around the edge. That pressure fluctuations propagate with the sound speed. It is clarified that the sound wave generated in rather wide region and individual vortices do not affect the sound wave propagation.

Mixers are used in various industrial fields where it is necessary to intimately mix two reactants in a short period of time. However, despite their widespread use, complex unsteady flow characteristics of industrial mixers are not systematic investigated. The present study aimed to clarify unsteady flow characteristics induced by various impellers in a tank. Impellers are pitched blade turbine and neo-hydrofoil turbine types. A high speed CCD camera and an Ar-Ion laser for illumination were adopted to clarify the time-dependent flow characteristics of the mixers. The rotating speed of impellers increased from 6Hz to 60Hz by 6Hz. The maximum velocity around PBT impeller is higher than the hydrofoil type impeller. These two types of turbine shows that typical flow characteristics of axial turbine and suitable for mixing high -viscosity materials.

A new electrostatic rotary atomizing painting equipment using air turbine was developed. Based on the overall design requirements of painting equipment basic design specifications of the equipment parts such as air turbine and atomizing disk are defined from the present conceptual design model. Air turbine is designed with the section profile of NACA airfoil, and its internal flow field is analyzed by commercial CFD code. Atomizing disk is designed to achieve the ligament type spray of paint with the use of visualization technique. Various experiments and tests are conducted to investigate the spray and the transfer characteristics of newly-designed painting equipment, and the measurement results are compared with the those of conventional painting equipments.

Hermetic Compressor circulates refrigerant with constant flow rate regardless of operation condition. so, at the operating condition requiring low cooling capacity, too much refrigerant flow deteriorates seasonal energy efficiency ratio(SEER). In this reason, modulated compressor is needed to improve SEER. Among many types of modulated compressor, non-inverter type modulated compressor is required for its low cost and easy to development. In the modulated scroll compressor by bypass method, EER steeply decreases for many loss like re-compression, changes of volume ratio, decrease of motor efficiency by torque variation. So. the range of modulation ratio for optimized SEER must be selected accompany with air conditioner set development.

For a single stage two cylinder rotary compressor, an analytical study has been made on the discharge gas pulsation. Discharge system of the twin rotary compressor consists of lower and upper mufflers and connecting passage holes between them, and cavities on both sides of the motor and passages between them. Acoustic modeling for the discharge system by transfer matrix method gives acoustic impedances at discharge valves so that gas pulsation at the valve sections can be obtained from discharge mass velocity. Since the mass velocity and the pressure pulsation at the valves are affected by each other, iteration should be made for convergence. Gas pulsations at other sections can also be calculated by using transfer matrix.

The automobile air conditioning system generally consists of laminated type evaporator, swash plate type compressor, condenser, expansion valve and receiver drier. A swash plate type compressor has been used widely in automobile air conditioning system since 1955, because of wider operation range and better durability than other type compressors. In this study, the performance of an swash plate type compressor with variations of oil charging conditions has been investigated experimentally using the hot gas system. Further, the effects of varying compressor speed on the performance of the compressor has been discussed.