• Title/Summary/Keyword: Reduction of Rotor Efficiency

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Evaluation of Tip Leakage Loss and Reduction of Efficiency of Axial Turbomachinery Using Numerical Calculation (수치계산에 의한 축류터보기계의 회전차 익말단의 누설손실과 효율저하에 대한 평가)

  • Ro, Soo-Hyuk;Cho, Kang-Rae
    • The KSFM Journal of Fluid Machinery
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    • v.2 no.1 s.2
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    • pp.73-80
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    • 1999
  • Leakage vortices formed new blade tip causes an increase of total pressure loss near the casing endwall region and as a result, the efficiency of rotor decreases. The reduction of rotor efficiency is related to the size of the tip clearance. In this study, the three-dimensional flowfields in an axial flow rotor were calculated by varying the tip clearance under various flow rates, and the numerical results were compared with experimental ones. The effects of tip clearance and attack angle on the leakage vortex and overall performance, and the loss distributions were investigated through numerical calculations. In this study, tip leakage flow rate and total pressure loss by tip clearance were evaluated using numerical results and approximate equations were presented to evaluate the reduction of rotor efficiency by tip leakage flow.

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Evaluation of Flowfield and Flow Losses insied Axial Turbomachinery Using Numerical Calculation [Evaluation of Tip Leakage Loss and Reduction of Efficiency by Tip Clearance] (수치계산에 의한 축류터보기계의 유동장과 유동온실의 평가 III [회전차 익말단의 누설손실과 효율저하에 대한 평가])

  • Ro, Soo-Hyuk;Cho, Kang-Rae
    • 유체기계공업학회:학술대회논문집
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    • 1998.12a
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    • pp.240-247
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    • 1998
  • Leakage vortices formed near blade tip causes an increase of total pressure loss near casing endwall region and as a result, the efficiency of rotor decreases. The reduction of rotor efficiency is related to the size of tip clearance. In this study, the three-dimensional flowfields in an axial flow rotor were calculated with varying tip clearance under various flow rates, and the numerical results were compared with experimental ones. The effects of tip clearance and attack angle on the leakage vortex and overall performance, and the less distributions were investigated through numerical calculations. In this study, tip leakage flow rate and total pressure loss by tip clearance were evaluated using numerical results and aprroximate equations were presented to evaluate the reduction of rotor efficiency by tip leakage flow.

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Numerical Analysis on the Blade Tip Clearance Flow in the Axial Rotor (III) - Evaluation of Tip Leakage Loss and Reduction of Efficiency near Blade Tip Clearance Region of a Rotor - (축류 회전차 익말단 틈새유동에 대한 수치해석 (III) - 회전차 익말단의 누설손실과 효율저하에 대한 평가 -)

  • Ro, Soo-Hyuk;Cho, Kang-Rae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.9
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    • pp.1113-1120
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    • 1999
  • Leakage vortices fonned near the blade tip cause an increase of total pressure loss near the casing endwall region and as a result, the efficiency of rotor decreases. The reduction of rotor efficiency is related to the size of tip clearance. In this study, the three-dimensional flow fields in an axial flow rotor were calculated with varying tip clearance under various flow rates, and the numerical results were compared with experimental ones. The effects of tip clearance and the of attack on the leakage vortex and overall performance, and the los9 distributions were investigated through numerical calculations. In this study, tip leakage flow rate and total pressure loss due to the tip clearance were evaluated using numerical results and approximate equations were presented to evaluate the reduction of rotor efficiency due to the tip leakage flow.

Optimal Design of Line-start Permanent Magnet Motor for High efficiency Performance with double-barrier rotor design (단상 유도형 동기 전동기의 효율 향상을 위한 회전자 형상 최적화)

  • Fang, Liang;Lee, Byeong-Hwa;Hong, Jung-Pyo;Nam, Hyuk;Ha, Seung-Hyung
    • Proceedings of the KIEE Conference
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    • 2008.07a
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    • pp.768-769
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    • 2008
  • This paper examines an design of double-barrier rotor structure for improving the efficiency performance in a single-phase line-start permanent magnet(LSPM) motor. By utilizing the advantages of double-barrier rotor design that by increasing reluctance torque generation to compensate magnet torque production, the copper loss reduction is achieved. The optimal approach of response surface methodogy(RSM) is performed for determining a optimum double-barrier rotor structure. The improving of efficiency performance is confirmed by finite element method(FEM) and test.

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Rotor Shape Design of Single Phase LSPM for Improvement of Start-up Characteristics and Efficiency (기동특성 및 효율 향상을 위한 Single-Phase LSPM의 회전자 형상 설계)

  • Kang, Min-Chul;Cho, Kwang-Jin;Kim, Gyu-Tak
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.1
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    • pp.58-64
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    • 2016
  • In this paper, the design of rotor shape was performed for improvement of start-up characteristics and efficiency in single-phase LSPM. In order to improve the start-up characteristics, shape of rotor aluminium cage bar was changed. Through arrangement of permanent magnets and installation of flux barriers, it was performed torque ripple reduction and efficiency improvement. Cogging torque and back-EMF is calculated by the no-load analysis, start-up time is calculated by the start-up state analysis, efficiency and torque ripple is calculated by steady state analysis. The characteristics of the motor were calculated through FEM.

A Study of the Tip Clearance Effect to the Performance of an Axial-Type Fan (축류형 송풍기의 익단간극이 성능에 미치는 영향에 관한 연구)

  • Cho, Chong-Hyun;Jung, Yang-Beom;Kim, Young-Cheol;Cho, Soo-Yong
    • The KSFM Journal of Fluid Machinery
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    • v.11 no.6
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    • pp.7-17
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    • 2008
  • Fan performances are obtained with various tip clearance gaps and stagger angles of the rotor. A tested fan is an axial-type fan of which the casing diameter is 806 mm. Two different rotors are applied to this test. One is designed on the basis of the free vortex method along the radial direction and the other is designed using the forced vortex method. The operating conditions are varied to the ultimate off-design point as well as the deign point. Overall efficiency, total pressure and input power are compared with the tip clearance gaps and different stagger angle. The experimental results show that changing of the stagger angle has minor influence to the performance when the same rotor is applied. When the tip clearance gap is less than 5% of the rotor span, the overall efficiency, total pressure loss and input power reduction are varied linearly with the variation of the tip clearance gaps. On the design point, the overall efficiency is decreased to the rate of 2.8-2.9 to the increasing of the tip clearance, but the changing rate of the overall efficiency is alleviated when the fan operates at off-design points. In particular, this rate is more quickly declined on a fan with the rotor designed using the forced vortex method. The result of the total pressure shows that the pressure reduction rate is a 0.08-0.1 according to the tip clearance, and additionally the input power reduction rate is a 0.045-0.065 at design point.

Development of rotor profile design technology for improving the screw compressor performance (공기압축기 성능향상을 위한 로터 프로파일 설계기술 개발 연구)

  • Kim, Tae-Yoon;Lee, Jae-Young;Lee, Dong-Kyun;Kim, Youn-Jea
    • Proceedings of the KSR Conference
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    • 2009.05b
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    • pp.585-592
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    • 2009
  • The performance of screw compressor depends on lots of design parameters of rotor profile, such as length of seal line, wrap angle, blow hole, suction and discharge port size, number of rotor lobe, etc. The optimum rotor profile makes it possible to increase the compression efficiency with low energy consumption, and to minimize the loss of power. In this research, a new rotor profile design and performance analysis are done by computer simulation. It is expected that the volumetric efficiency is improved because the internal leakage is reduced due to the minimization of blow hole and clearance, and the stiffness of rotors is increased due to the reduction of length to diameter ratio. Also, the specific power consumption will be secured for use ranging from low to high operation speed.

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Design of Fan-shape Type PMSM for Improving Efficiency of Non-rare Earth Motor (비희토류 전동기의 효율 향상을 위한 Fan-shape type PMSM 설계 및 성능 분석)

  • Cho, Sooyoung;Ahn, Hanwoong;Ham, Sang-Hwan;Jin, Chang-Sung;Lee, Sung Gu;Lee, Ju
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.2
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    • pp.360-364
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    • 2016
  • The rare earth output is concentrated in limited number of countries including China. Also the necessity for development of non-rare earth motor is getting signified due to the rapid increase of rare earth price and resource weaponizing policies. Non-rare earth motor is generally designed as spoke type PMSM (Permanent Magnet Synchronous Motor) in order to maximize the power density. Such spoke type PMSM has advantage in concentrating the flux but demonstrates lower efficiency compared to permanent magnet using Nd (Neodymium) permanent magnet. Therefore, applications with strong necessity for efficiency need rotor structure having improved efficiency compared to spoke type PMSM. Hence, this study suggested fan-shape type PMSM with somewhat lower power density but maximized efficiency. Fan-shape type PMSM is a rotor shape demonstrating outstanding reduction of iron loss compared to existing spoke type. Thus, this study analyzed the improvement of efficiency and reduction of loss arising from the suggested shape through parameter calculation.

Torque Ripple Reduction of a PM Synchronous Motor for Electric Power Steering using a Low Resolution Position Sensor

  • Cho, Kwan-Yuhl;Lee, Yong-Kyun;Mok, Hyung-Soo;Kim, Hag-Wone;Jun, Byoung-Ho;Cho, Young-Hoon
    • Journal of Power Electronics
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    • v.10 no.6
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    • pp.709-716
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    • 2010
  • MDPS (motor driven power steering) systems have been widely used in vehicles due to their improved fuel efficiency and steering performance when compared to conventional hydraulic steering. However, the reduction of torque ripples and material cost are important issues. A low resolution position sensor for MDPS is one of the candidates for reducing the material costs. However, it may increases the torque ripple due to the current harmonics caused by low resolution encoder signals. In this paper, the torque ripple caused by the quantized rotor position of the low resolution encoder is analyzed. To reduce the torque ripples caused by the quantization of the encoder signals, the rotor position and the speed are estimated by measuring the frequency of the encoder signals. In addition, the compensating q-axis current is added to the current command so that the 6th order torque harmonic is attenuated. The reduction of torque ripples by applying the estimated rotor position and the compensated q-axis current is verified through experimental results.

The performance effect of shroud split for turbopump turbine rotor (터보펌프 터빈 로터의 슈라우드 스플릿이 성능에 미치는 영향)

  • Lee, Hang-Gi;Jung, Eun-Hwan;Yoon, Suk-Hwan;Park, Pyun-Gu;Kim, Jin-Han
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2012.05a
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    • pp.117-122
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    • 2012
  • A blisk with rotor shroud is usually adopted in LRE turbine to maximize its performance. However it experiences severe thermal load and resulting damage during engine stating and stop. Shroud splitting is devised to relieve thermal stress on the turbine rotor. Structural analysis confirmed the reduction of plastic strain at the blade hub and tip. However, split gap at the rotor shroud entails additional tip leakage and results performance degradation. In order to assess the effect of shroud split on the turbine performance, tests have been performed for various settings of shroud split. For the maximum number of shroud splitting, measured efficiency reduction ratio was 2.65% to the value of original shape rotor.

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