• 한국유체기계학회 논문집
• /
• 제4권3호
• /
• pp.46-52
• /
• 2001

This paper describes a turbine test program conducted at Seoul National University(SNU). To measure blades' aerodynamic performance, either linear(2-Dimensional) or annular(3-Dimensional) cascades are often used. However, neither cascade can consider effects such as those due to rotation or rotor-stator interaction. Therefore, a rotating test facility for axial turbines has been designed and built at SNU, and its description is given in this paper. The results from an axial turbine performance test are presented. At the design point, the measured efficiency agrees with the efficiency predicted by a meanline analysis. At off design points, however, the measured and predicted efficiencies diverge. The most likely cause is hypothesized to be the inaccuracy of correlations used in the meanline analysis at off design points.

• International Journal of Fluid Machinery and Systems
• /
• 제1권1호
• /
• pp.121-139
• /
• 2008

For mechanical drive steam turbines, the investigation results of corrosion fatigue phenomena in the transient zone are introduced, including basic phenomena on expansion line and actual design and damage experience. These results were analyzed from the standpoint of stress intensity during the start of cracking. In order to resolve such problems, preventive coating and blade design methods against fouling and corrosive environments are developed. Detailed evaluation test results are given for coating performance using a unique test procedure simulating fouling phenomena and washing conditions. Finally, the results of the successful modification of internals and on-line washing results on site are introduced.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.148-151
• /
• 2008

In a double-passage cascade apparatus, only two blades are installed in order to increase the accuracy of experimental result by applying bigger blade than the size of multi-blades on the same apparatus. However, this causes difficulties to make correct periodic condition. In this study, sidewalls are designed to meet periodic condition without removing the operating fluid or adjusting tail boards. Surface Mach number on the blade surface is applied to a responsible variable, and 12 design variables which are related with sidewall profile control are selected. A gradient based optimization is adopted for wall design and CFX-11 is used for the internal flow computation. The computed result shows that it could obtain the same flow structure by modifying only the sidewalls of the double-passage cascade apparatus.

• Nuclear Engineering and Technology
• /
• 제39권1호
• /
• pp.21-30
• /
• 2007

Current high-temperature gas-cooled reactors (HTGRs) are based on a closed Brayton cycle with helium gas as the working fluid. Thermodynamic performance of the axial-flow helium gas turbines is of critical concern as it considerably affects the overall cycle efficiency. Helium gas turbines pose some design challenges compared to steam or air turbomachinery because of the physical properties of helium and the uniqueness of the operating conditions at high pressure with low pressure ratio. This report present a review of the helium Brayton cycle experiences in Germany and in Japan. The design and availability of helium gas turbines for HTGR are also presented in this study. We have developed a new throughflow calculation code to calculate the design-point performance of helium gas turbines. Use of the method has been illustrated by applying it to the GTHTR300 reference.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
• /
• pp.237-243
• /
• 2002

A centrifugal compressor of 50HP for reverse brayton cryocooler using neon as a coolent has been developed. It has relatively low total-to-total pressure ratio but mass flow rate is very small and the voting gas, neon, has greater specific heat ratio than air. It was essential to have very high rotational speed of 100,000 RPM. The efficiency of compressor has great effects on overall system and the COP of cryocooler. To meet the design requirement of the compressor efficiency and to minimized the required rotational speed, highly efficiency impeller having low specific speed was designed. To maintain the overall system efficient high, gas bearing of bump type and high speed permanent magnet synchronus motor was developed and adopted. In this paper, design and performance prediction results of the compressor impeller is presented.

• 한국유체기계학회 논문집
• /
• 제18권4호
• /
• pp.56-61
• /
• 2015

It is important requirement to properly evaluate the aerodynamic performance and characteristics during preliminary design of a centrifugal compressor. In this study the centrifugal compressor was calculated for variations of mass flow and blade Mach number by means of single passage steady state. A lot of quantitative performance values were obtained and through the obtained values the aerodynamic performance characteristics of designed impeller and vaned diffuser were investigated. The results were classified by blade Mach number to analyze characteristics and the aerodynamic performance was examined at choke of impeller, diffuser and separation of diffuser.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
• /
• pp.149-155
• /
• 2001

Recently, it is required to design higher stage pressure ratio compressor while maintaining equal adiabatic efficiency. To increase the stage pressure ratio, blade rotational speed or diffusion factor should be increased. In the case of increasing rotational speed, relative speed of flow at blade leading edge is well supersonic. In supersonic blade, total pressure loss is mainly due to shock wave and blade leading edge thickness should be very thin to minimize the shock wave loss. As a result, the blade is like to be week in terms of mechanical strength and the manufacturing cost is very high because NC machining is necessary. It is also one of big hurdle to overcome to make small compressor. In this paper, the effects of blade leading edge to the performance of supersonic blade In terms of total pressure loss. The efficiency of already known method to make thin blade leading edge from the casted blade with rather thick leading edge thickness is also assessed.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
• /
• pp.367-370
• /
• 2006

Performances of multiple surrogate models are evaluated in a turbomachinery blade shape optimization. The basic models, i.e., Response Surface Approximation, Kriging and Radial Basis Neural Network models as well as weighted average models are tested for shape optimization. Global data based errors for each surrogates are used to calculate the weights. These weights are multiplied with the respective surrogates to get the final weighted average models. The design points are selected using three level fractional factorial D-optimal designs. The present approach can help address the multi-objective design on a rational basis with quantifiable cost-benefit analysis.

• International Journal of Fluid Machinery and Systems
• /
• 제6권4호
• /
• pp.177-187
• /
• 2013

A scaling method valid for most turbomachines based on first principles is derived. It accounts for axial and centrifugal turbomachines with respect to relative gap width/tip clearance, relative roughness, Reynolds number and/or Mach number for design and off-design operation as well. The scaling method has been successfully validated by a variety of experimental data obtained at TU Darmstadt. The physically based, hence reliable and universal method is compared with previous, empirical scaling methods.

• 한국유체기계학회 논문집
• /
• 제18권6호
• /
• pp.12-18
• /
• 2015

Recently, the development trend of turbomachinery is high capacity and high efficiency. Most of turbomachinery in the market are adopting ball bearings or air foil bearings. However, ball bearings have a limit for high speed product over $2.0{\times}10^6DN$(product of the inner diameter of the bearing in mm (D) and the maximum speed in rpm (N)). Air foil bearings have a limit for high axial load for high power products over 200~300 HP(horse power). Magnetic bearing is one of the solutions to overcome the limits of high speed and high axial load. Because magnetic bearings have no friction between the rotor and the bearings, they can reduce the load of the motor and make it possible to increase the rotating speed up to $5.0{\times}10^6DN$. Moreover, they can have high axial load capacity, because the axial load capacity of magnetic bearing depends on the capacity of the designed electromagnet. In this study, the radial and thrust magnetic bearings are designed to be applied to the 200 HP class turbo blower, and their performance was evaluated by the experiment. Based on the tests up to 26,400 rpm and 21,000 rpm under the no-load and load condition, respectively, it was verified that the magnetic bearings are stably support the rotor of the turbo blower.