• 소음진동
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• 제9권5호
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• pp.1042-1049
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• 1999

In the Part I has been reported a rotordynamic analysis of the driving motor-bull gear rotor-bearing system of a turbo-chiller. In this study, Part II, a rotordynamic analysis is performed with the turbo-chiller compressor pinion-impeller rotor system supported on two fluid film bearings. The pinion-impeller rotor system is driven to a rated speed of 14,600 rpm through a speed-increasing pinion-bull gear. It is modeled utilizing the finite element method for analysis. As loadings on the bearings due to the gear action are significant in the system considered, each resultant bearing load is calculated statically by considering the generalized forces of the gear action as well as the rotor itself. The two support bearings, the generalized forces of the gear action as well as the rotor itself. The two support bearings, partial and 3-axial groove bearings, are designed to take their varying loads along with their varying load angles, and they are also analyzed to give their rotordynamic coefficients. Then, a complex rotordynamic analysis of the compressor pinion-impeller rotor-bearing system is carried out to evaluate its stability, whirl natural frequencies and mode shapes, and unbalance responses under various loading conditions. Results show that the bearings and entire rotor system are well designed regardless of operating conditions, i.e., loads and operating speeds.

• 항공우주기술
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• 제3권2호
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• pp.183-190
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• 2004

액체로켓용 연료펌프의 설계를 검증하기 위해 상용 3차원 유동해석 소프트웨어를 이용하여 설계점 성능을 예측하였다. 연료펌프의 성능과 축추력에 영향을 미치는 누설유량에 대한 예측의 정확도를 높이기 위해 인듀서, 임펠러, 볼류트 및 2차 유로를 계산영역으로 설정하였으며 인듀서/임펠러/누설유로/볼류트 사이의 경계면에 혼합면 기법을 적용하여 계산에 소요되는 시간을 줄이고자 하였다. 유동해석을 통해 예측된 수력성능은 설계요구조건을 만족시키는 것으로 나타났으나 축추력이 허용치에 비해 크게 예측되어 이를 감소시키기 위한 설계변경이 이루어졌다. 변경된 설계안에 대한 유동해석을 수행한 결과 연료펌프의 수력성능은 유지되면서 축추력은 처음의 설계안에 비해 30% 수준으로 크게 감소하였음을 확인할 수 있었다.

• 대한기계학회논문집B
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• 제38권12호
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• pp.1065-1072
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• 2014

본 연구에서는 양흡입 원심블로어의 성능향상을 위하여 임펠러 스플리터의 형상 최적화 연구를 수행하였다. 두 개의 스플리터 형상 설계 변수(스플리터 코드 및 피치)를 선정하여 블로어 성능 및 내부 유동장 특성을 평가하였다. 수치해석에 의한 블로어 성능은 설계유량 조건에서 실험결과와 최대 4 % 이내로 잘 일치하였다. 스플리터 형상 최적화를 통하여 설계조건에서의 블로어 효율 및 압력은 기준 블로어 보다 3.65 % 및 1.14 % 각각 향상되었다. 스플리터 최적설계로 임펠러 날개 부압면의 유동박리를 억제시켜 익간 저속 유동에 의한 압력손실을 줄임으로써 블로어 전체의 성능이 향상되었다. 익간 내부유동 균일화는 임펠러 출구속도 분포에도 영향을 주어 볼류트케이싱 출구압력도 향상되었다.

• Korean Chemical Engineering Research
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• 제50권5호
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• pp.913-922
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• 2012

환경 및 화학공업에서 액-액 교반조내의 특성을 파악하는 일은 매우 중요하다. 액적 부근의 물질이동용량계수 $k_La$와 Sauter 평균경 $d_{32}$은 에스테르의 알칼리 가수분해반응을 이용하여 임펠러 부착위치나 액높이를 변화시켜 측정하였다. 그 결과 아래와 같은 이들의 양호한 상관식을 얻었다. $$d_{32}=0.270\(\frac{{\sigma}^{0.6}}{{\rho}^{0.2}P^{0.4}_{Vi}}\)k_La=0.49\(\frac{6{\phi}D_A}{d^2_{32}}\)\(\frac{P_Vd^4_{32}}{{\rho}v^3}\)^{0.193}Sc^{1/3}$$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.690-695
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• 2001

The three-dimensional spatial structures of impeller flow created by a six bladed Rushton turbine have identified based on the volumetric velocity information from multi-plane stereoscopic PIV measurements. A total of 10 planes with 2 mm space with a 50 mm by 64 mm size of the field of view were targeted. To reduce the depth of focus, we adopted an angle offset configuration which satisfied the Scheimpflug condition. The distortion compensation procedure was utilized during the in situ calibration. Phase-locked instantaneous data were ensemble averaged and interpolated in order to obtain mean 3-D, volumetric velocity fields on a 60 degree sector of a cylindrical ring volume enclosing the turbine blade. Using the equi-vorticity surface rendering, the spatial structure of the trailing vortices was clearly demonstrated. Detail flow characteristics of the radial jet reported in previous studies of mixer flows were easily identified.

• 설비공학논문집
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• 제22권3호
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• pp.139-148
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• 2010

A centrifugal compressor for HFC-134a has been newly designed and developed. Flow analysis using commercial programs was used to evaluate performance and internal flow of the impeller, inlet guide vane and diffuser etc. The purpose of this study is to establish the design theory necessary to the development of HFC-134a centrifugal compressors and to supply basic data related to design by reviewing design values and experimental values through the performance test. The compressor for HFC-134a was also investigated experimentally to check compression performance. The calculated data coincide the test results of compressor. The data obtained in the present study are useful for design of HFC-134a centrifugal compressors.

• 대한기계학회논문집B
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• 제27권6호
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• pp.773-780
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• 2003

The three-dimensional spatial structures of impeller flow created by a six bladed Rushton turbine have identified based on the volumetric velocity information from multi-plane stereoscopic PIV measurements. A total of 10 planes with 2 mm space and a 50 mm by 64 mm size of the field of view were targeted. To reduce the depth of focus, we adopted an angle offset configuration which satisfied the Scheimpflug condition. The distortion compensation procedure was utilized during the in situ calibration. Phase-locked instantaneous data were ensemble averaged and interpolated in order to obtain mean 3-D. volumetric velocity fields on a 60 degree sector of a cylindrical ring volume enclosing the turbine blade. Using the equi-vorticity surface rendering, the spatial structure of the trailing vortices was clearly demonstrated. Detail flow characteristics of the radial jet reported in previous studies of mixer flows were easily identified.

• 한국유체기계학회 논문집
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• 제17권1호
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• pp.28-34
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• 2014

This paper presents the performance enhancement of a double-inlet centrifugal blower by the shape optimization of an impeller. Two design variables, a number of blade and a length of chord, are introduced, and analyzed by a response surface method. Three-dimensional compressible Navier-Stokes equations are used to analyze the blower performance and the internal flow of the blower. Throughout the numerical simulation of the blower, blower efficiency can be increased by reducing separation flow generating from the blade leading edge of a blade pressure surface. It is noted that recirculation flow observed inside the blade passage induces low velocity region, thus increases pressure loss. Efficiency and pressure of the optimum blower are successfully increased up to 3% and 3.9% compared to those of reference blower at the design flow condition, respectively. Detailed flow field inside the blower is also analyzed and compared.

• 한국CDE학회논문집
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• 제19권1호
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• pp.12-18
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• 2014

Shot-peening is frequently used on various mechanical parts because it can improve the fatigue life of components by generating compressive residual stresses on the surface. This can be done by repeatedly hitting the work-piece surface with small balls and making indentations on it. In fact, finding optimal peening time among various peening parameters is the most important. Under-peening can not improve the fatigue life sufficiently while over-peening causes cracks and reduces fatigue life in contrast. In general, optimal peening time is experimentally determined by measuring arc-height using Almen-strip in accordance with SAE J442 standard. To save the time and efforts spent in carrying out experiments to find optimal peening time, this paper presents a computer simulation algorithm for the estimation of surface coverage made by impeller type shot-peening machines (PMI-0608). Surface coverage is defined as the proportion of the work-piece surface that has been indented in a given time of shot-peening. An example (standard tensile test specimen) is presented to validate the proposed method.

• 한국기계가공학회지
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• 제20권12호
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• pp.71-77
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• 2021

An impeller identification technique that is essential for adding viscosity measurement functions to overhead stirrers is presented in this study. Previous studies have revealed that using magnets facing the same poles arranged in a row can aid in distinguishing the types of impellers by detecting the number of magnets in a non-contact manner. However, as these previous studies measured the magnetic fields using analog Hall sensors, a converting circuit for the digital signals is required that can interface with the MCU. In this study, it was demonstrated that the number of magnets can be distinguished without using a separate conversion circuit by using a Hall sensor with a digital output. Owing to the unique hysteresis characteristics of digital Hall sensors, it was confirmed through experiments that the complex and diverse outputs appear depending on the direction of the magnetic field, the arrangement of magnetic poles, and the moving direction of the magnet. The measurement of the magnetic field showed that an edge signal equal to the number of magnets inserted into the impeller was detected when the radial direction was used, and the south pole was first approached.