• Title/Summary/Keyword: Centrifugal

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Experimental Study on Stall Inception in a Centrifugal Compressor (원심압축기 스톨 발단에 관한 실험적 연구)

  • Kang, Jeong-Seek;Kang, Shin-Hyoung
    • 유체기계공업학회:학술대회논문집
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    • 2000.12a
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    • pp.200-210
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    • 2000
  • 본 연구에서는 고속의 원심압축기에서 스톨 발단에 관한 연구를 수행하였다. 스톨을 일으키는 요인과, 스톨이 발생하기 전에 이를 미리 경고할 수 있는 방법을 주된 연구 주제로 삼았다. 원주방향으로 균일하게 분포된 8개의 고속응답 압력변환기를 사용하여 순간압력을 측정하였으며, 이 신호를 공간 푸리에 변환(space Fourier transform)을 사용하여 스톨의 발단을 알리는 신호를 측정하였고, 회전하는 파의 에너지(Traveling Wave Energy) 방법을 사용하여 스톨을 미리 경고하는 방법에 대하여 연구하였다. 회전하는 파의 에너지 방법은 스톨을 경고하는 데 좋은 성능을 보였으며, 저속에서는 약 임펠러 100회전, 중간속도에서는 약 200회전, 그리고 고속에서는 약 임펠러 1000회전의 경고시간을 보였다. 그리고 스톨 발단 근처에서 공간 푸리에 계수의 위상이 임펠러 주파수의 속도로 선형적인 증가를 보이는 구간이 나타났으며, 또한 임펠러 주파수의 스펙트럼이 스톨로 접근하면서 증가하는 것으로부터, 임펠러 주파수가 스톨을 일으키는 중요한 요인으로 작용함을 알 수 있었다. 또한 임펠러의 회전속도에 관계없이 스톨로 접근하면서 임펠러 주파수의 스펙트럼이 증가하므로, 이 값이 스톨을 경고하는 방법으로 사용될 수 있음을 보였으며, 약 임펠러 2n회전의 경고시간을 얻을 수 있었고, 임펠러의 속도가 빠를수록 긴 경고시간을 얻었다. 이 방법의 개발로 하나의 센서의 측정만으로도 효과적으로 스톨을 경고할 수 있는 기반을 마련하였다.

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Improving Flow Distribution in a Suction Channel for a Highly Efficient Centrifugal Compressor

  • Yagi, Manabu;Shibata, Takanori;Kobayashi, Hiromi;Tanaka, Masanori;Nishida, Hideo
    • International Journal of Fluid Machinery and Systems
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    • v.5 no.3
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    • pp.100-108
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    • 2012
  • Design parameters for suction channels of process centrifugal compressors were investigated, and an optimization method to enhance stage efficiency by using the new design parameters was proposed. From results of computational fluid dynamics, the passage sectional area ratios $A_c/A_e$, $A_e/A_s$ and $A_c/A_s$ were found to be the dominant parameters for the pressure loss and circumferential flow distortion, where $A_c$, $A_e$ and $A_s$ are passage sectional areas for the casing upstream side, casing entrance and impeller eye, respectively. The Base suction channel was optimized using the new design parameters, and the Base and Optimized types were tested. Test results showed that the Optimized suction channel achieved 3.8% higher stage efficiency than the Base suction channel while maintaining the same operating range.

Steering System in a Self-Balancing Electric Scooter (역진자형 전동 스쿠터의 조향 시스템)

  • Choi, Yong Joon;Ryoo, Jung Rae;Doh, Tae-Yong
    • Journal of Institute of Control, Robotics and Systems
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    • v.20 no.9
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    • pp.942-949
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    • 2014
  • In this paper, a new steering system for a self-balancing electric scooter is proposed with an intuitive steering command input method, where the steering command is generated from the rider's motion of shifting body to move the center of gravity toward the rotational direction. For the purpose, weight distributions on the rider's feet are measured using force sensors placed beneath the rider's feet, and the difference is applied to a steering control system. Stability of the steering system and resultant radius of gyration is investigated by modeling the steering system in consideration of the rider's motion and centrifugal force. The proposed steering system is applied to experiments, and the results are presented to prove the validity of the proposed method.

Modular Program for Conceptual Design of Liquid Rocket Engine System, Part I : Essential Components Design (액체 로켓 엔진시스템 개념설계를 위한 모듈화 프로그램 Part I : 주요 구성품 설계)

  • Yang, Hee-Sung;Park, Byung-Hoon;Yoon, Woong-Sup
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.9
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    • pp.805-815
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    • 2007
  • In order to build a conceptual design program for a liquid rocket engine system, performance based sub-programs for each core component of the engine system were made. Parts included were the combustion chamber, supersonic nozzle, centrifugal pump, and impulsive turbine. Simple mathematical models based on classical thermodynamic and inviscid theories were adopted with proper tuning by empirical data. In Part I, aiming to validate each sub-program, we examined the results of each program qualitatively, and parametrically investigated the sensitivity due to the change in design parameters.

Development of Boundary Pressure Gauge (경계(境界) 토압계(土壓計)의 개발(開發))

  • Yoo, Nam Jae
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.10 no.1
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    • pp.135-143
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    • 1990
  • Based on the mechanism of flat jack used to measure stresses in rocks, a prerssure gauge was developed to measure vertical stresses acting on the rigid boundary in a soil mass. This paper describes the mechanism of the newly built pressure gauge, the process of calibrating the response of this gauge, and its use to centrifugal model tests. By installing this gauge in centrifugal model experiments of reinforced earth retaining walls, vertical stress distribution at the rigid boundary of model wall was obtained and compared with theoretical prediction of trapezoidal vertical stress distribution.

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A Numerical Investigation of Flow and Performance Characteristics of a Small Propeller Fan Using Viscous Flow Calculations

  • Oh, Keon-Je;Kang, Shin-Hyoung
    • Journal of Mechanical Science and Technology
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    • v.16 no.3
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    • pp.386-394
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    • 2002
  • The present work is aimed at investigating an unusual variation in flow and performance characteristics of a small propeller fan at low flow rates. A performance test of the fan showed dual performance characteristics, i.e., radial type characteristics at low flow rates and axial type at high flow rates. Dual performance characteristics of the fan are numerically investigated using viscous flow calculations. The Finite Volume Method is used to solve the continuity and Navier-Stokes equations in the flow domain around a fan. The performance parameters and the circumferentially averaged velocity components obtained from the calculations are compared with the experimental results. Numerical values of the performance parameters show good agreement with the measured values. The calculation simulates the steep variations of performance parameters at low flow rates and shows the difference in the flow structure between high and low flow rates. At a low flow coefficient of $\Phi$=0.2, the flow enters the fan in an axial direction and is discharged radially outward at its tip, which is much like the flow characteristics of a centrifugal fan. The centrifugal effect at low flow rates makes a significant difference in performance characteristics of the fan. As the inlet flow rate increases, flow around the fan changes into the mixed type at $\Phi$=0.24 and the axial discharge at $\Phi$=0.4.

Fundamental Study on Cathodic Protection and Material Development as Erosion-Control Methods of Oceanic Centrifugal Pump(1) (해상용 원심펌프 임펠러의 침식억제법으로 음극방식 및 재료개발에 관한 기초연구 1)

  • 이진열;임우조
    • Journal of Advanced Marine Engineering and Technology
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    • v.19 no.2
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    • pp.56-66
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    • 1995
  • Recently, with theraped advancement in th oceanology such an ocean-going vessel and oceanic structures, there is a need to study the cavitation erosion-corrosion control of pump impeller, the partial element of ocean machinery, for more effective operation. Especially, the cathodic protection (impressed current method & Al-sacrificial anode method) was applied to sea water, and Cu-alloy material mixed Zn & Al was used as a control method of cavitation erosion-corrosion. In this study, used the piezoelectric vibrator with 20KHz, 24.mu.m to cavity generation apparatus, and investigated the weight loss, weight loss rate, electrode potential & current density etc. under this condition. According to test result, thos describes how to indentify an influence of the cathodic protection and Al & Zn addition in material development for the control of cavitation erosion-corrosion, and those will serve as fundamental data on the cavitation erosion-corrosion control of oceanic centrifugal pump.

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Development of Crack Detecting Method at Steam Turbine Blade Root Finger using Ultrasonic Test (초음파탐상 검사를 이용한 증기터빈 블레이드 루트 휭거 균열 탐지기법 개발)

  • Yun, Wan-No;Kim, Jun-Sung;Kang, Myung-Soo;Kim, Duk-Nam
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.6
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    • pp.738-744
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    • 2011
  • The reliability of blade root fixing section is required to endure the centrifugal force and vibration stress for the last stage blade of steam turbine in thermal power plant. Most of the domestic steam turbine last stage blades have finger type roots. The finger type blade is very complex, so the inspection had been performed only on the exposed fixing pin cross-section area due to the difficulty of inspection. But the centrifugal force and vibration stress are also applied at the blade root finger and the crack generates, so the inspection method for finger section is necessary. For the inspection of root finger, inspection points were decided by simulating ultra-sonic path with 3D modeling, curve-shape probe and fixing jig were invented, and the characteristics analysis method of ultrasonic reflection signal and defect signal disposition method were invented. This invented method was actually executed at site and prevented the blade liberation failure by detecting the cracks at the fingers. Also, the same type blades of the other turbines were inspected periodically and the reliability of the turbine increased.

A Fundamental Study on the Development of a Variable Preload Device Using Toggle Joint Mechanism (토글 조인트장치를 이용한 가변예압장치 개발을 위한 기초 연구)

  • Choi, Chi Hyuk;Cha, Na Hyeon;Lee, Choon Man
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.3
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    • pp.260-265
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    • 2013
  • To increase the machine accuracy by improving the stiffness of spindle bearings, preload was applied to the spindle bearings. The methods of fixed position preload, convertible preload, constant pressure preload, and variable preload are used to apply the preload to the spindle bearing. The previous studies performed by the author of this study were variable preload methods using rubber pressure and centrifugal force based on mechanical systems. This study proposed a toggle joint mechanism that could be applied to variable preload method using centrifugal force and rubber pressure to increase the preload. Also, a finite element analysis was conducted to predict the deformation of the rubber and change of the preload. And the analysis results showed that the preload by the device using rubber pressure only was increased by the toggle joint mechanism using rubber pressure.

Appropriate Input Earthquake Motion for the Verification of Seismic Response Analysis by Geotechnical Dynamic Centrifuge Test (동적원심모형 시험을 이용한 부지응답해석 검증시 입력 지진의 결정)

  • Lee, Jin-Sun
    • Journal of the Earthquake Engineering Society of Korea
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    • v.17 no.5
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    • pp.209-217
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    • 2013
  • In order to verify the reliability of numerical site response analysis program, both soil free-field and base rock input motions should be provided. Beside the field earthquake motion records, the most effective testing method for obtaining the above motions is the dynamic geotechnical centrifuge test. However, need is to verify if the motion recorded at the base of the soil model container in the centrifuge facility is the true base rock input motion or not. In this paper, the appropriate input motion measurement method for the verification of seismic response analysis is examined by dynamic geotechnical centrifuge test and using three-dimensional finite difference analysis results. From the results, it appears that the ESB (equivalent shear beam) model container distorts downward the propagating wave with larger magnitude of centrifugal acceleration and base rock input motion. Thus, the distortion makes the measurement of the base rock outcrop motion difficult which is essential for extracting the base rock incident motion. However, the base rock outcrop motion generated by using deconvolution method is free from the distortion effect of centrifugal acceleration.