• 소음진동
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• 제9권3호
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• pp.593-599
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• 1999

A rotordynamic analysis is performed with a motor-bull gear rotor system supported on two partial bearings, which is intended to drive a high-speed turbo-chiller compressor impeller shaft through its built-in pinion gear. The motor-bull gear rotor system has a rated speed of 3,600 rpm, and 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 partial 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 motor-bull gear rotor-bearing system is carried out to evaluate its 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 regradless of operating conditions, i.e., loads and operating speeds.

• 한국유체기계학회 논문집
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• 제7권6호
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• pp.21-27
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• 2004

The floating ring seal has an advantage to find the optimum position by itself, which is used in the turbo pump of a liquid rocket. The main purpose of seals is to reduce the leakage. Especially, seals of the turbo pump for the liquid rocket engine are operated under the serious conditions such as high pressure above 10 MPa, very low temperature about $-180^{\circ}C$ and high rotating speed above 25,000 rpm. So, rotordynamic stability is very important for the system stability. In this paper, the leakage and dynamic characteristics of floating ring seals were investigated by a experimental and analytical method. The theoretical results of the leakage performance for the floating ring seal showed much higher than that of experimental results. On the other hand, the results of stiffness and damping characteristics showed similarity each other. As the shaft speed was increasing, the whirl frequency ratio was increased in the experimental results.

• 대한기계학회논문집
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• 제13권3호
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• pp.373-384
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• 1989

본 논문에서는 상기와 같은 문제들을 규명하기 위하여 비교적 긴 원통에 액체를 내장할 수 있도록 회전체를 제작하여 액체의 종류, 점도, 액체의 양 등을 파라미터로 하여 불안정영역의 범위와 진동진폭에 관해서 실험적으로 조사하였고, 비중이 다른 2액체를 동시에 내장한 경우 액체의 자유표면과 경계면에 의한 진동특성을 을 검토하였다.

• 소음진동
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• 제7권3호
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• pp.467-475
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• 1997

A rotor-bearing system has been investigated, including internal damping and axial torque using finite dynamic elements. A procedure is presented for dynamic modeling of rotor-bearing system which consist of finite dynamic shaft elements, rigid disk, and bearing and seal. A finite dynamic element model including the effects of rotatory inertia, gyroscopic moments, axial force, and axial torque is developed using the frequency dependent shape function. The natural whirl speeds, stability, and unbalance response of rotor system are calculated on several cases and compared with the conventional finite elements.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.329-336
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• 2004

The lock-up position of the floating ring seal affects the leakage flowrate and the stability. And it is changed depending on the operating and geometry condition. In this paper, the leakage flowrate and stability with change of the height and length were investigated by theoretical analysis and experiment. The parameter of the height and length is expressed to the b and L. The decreasing of the b resulted in the increasing of equivalent whirl frequency ratio in the experimental result at the low speed and high pressure not such as theoretical analysis. As the L increased the leakage flowrate decreased and stiffness and direct damping coefficient increased in the experimental result. That was similar to the theoretical analysis.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권2호
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• pp.82-89
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• 2004

In this paper, an active magnetic bearing(AMB) system is designed and controlled using a digital Proportional-Integral-Derivative(PID) control concept. The plant dynamics consisting of actuator and rigid rotor dynamics are described. A digital PID controller with a global control and a local control concept is designed and implemented using digital signal processor. Some experiments are conducted with each global control and local control concept. These include start-up test, impulse test, whirl response, and generator load test. The experimental results and comparison between those of a global control and a local control indicate that the global control of concept has impressive static and dynamic control performance for the prototype considered. From the whirl test, the developed system set can be controlled within about $\pm10\mu\textrm{m}$ gap variation at the rotational speed of 6000rpm and generate the AC power of frequency of $60\textrm{Hz}$, voltage of 100V and current of 0.8$\textit{A}$.

• 한국정밀공학회지
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• 제7권3호
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• pp.103-114
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• 1990

Many high speed mechanical systems incorporate gearing for speed reduction. This study investigates the stability of mulit-rotor geared systems supported on oil film bearings taking into consideration the coupling between torsional and lateral dynamics. The emphasis of the study is on the analysis of the interaction between the combined torsional and whirl insta- bilities. The feasility of inducing a lateral and the torsional instability to neutralize an anticipated unstable condition is investigated. The possibility of suppressing the instabilities by controlling the parameters of the oil film bearings is also considered.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.523-530
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• 2006

A rotordynamic analysis was performed with a dry vacuum pump, which is a major equipment in modern semiconductor and LCD manufacturing processes. The system is composed of screw rotors, lobes picking air, helical gears, driving motor, and support rolling element hearings of rotors and motor. The driving motor-screw rotor system has a rated speed of 6,300rpm, and was modeled utilizing a rotordynamic FE method for analysis, which was verified through the results of its 3-D finite element model. As loadings on the bearings due to the gear action were significant in the system considered, each resultant bearing load was calculated determinately and indeterminately by considering the generalized forces of the gear action as veil as the rotor itself. Each resultant hearing loading was used in calculating each stiffness of rolling element bearings. Design goals are to achieve wide separation margins of critical speeds and favorable unbalance responses of the rotor in the operating range. Then, a complex rotordynamic analysis of the system was carried out to evaluate its forward synchronous critical speeds, whirl natural frequencies and mode shapes, and unbalance responses under various unbalance locations. Results show that the entire system is well designed in the operating range. In addition, the procedure of rotordynamic analysis for dry vacuum pump rotor-bearing system was proposed and established.

• 한국소음진동공학회논문집
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• 제18권8호
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• pp.879-885
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• 2008

A rotordynamic analysis was performed with a decant-type centrifuge, which is a kind of industrial centrifuge. The system is composed of screw rotor, bowl rotor, driving motors, gear box, and support rolling element bearings. These rotors have a rated speed of 4300 rpm, and were modeled utilizing a rotordynamic FE method for analysis, which was verified through 3-D FE analysis. Design goals are to achieve wide separation margins of lateral critical speeds, and favorable unbalance responses of the rotor in the operating range. Then, a complex analysis rotordynamic analysis of the system was carried out to evaluate its forward synchronous critical speeds and mode shapes, whirl natural frequencies, and unbalance responses under various balance grade. As a result of analysis, the rotordynamic analysis performed by separating a screw rotor and bowl rotor may cause an error in predicting critical speed of entire system. Therefore, the rotordynamic analysis of a coupled rotor combining a screw and bowl rotor must be performed in order to more accurately estimate dynamic characteristics of the decanter-type centrifuge as presented in this paper. Also, rolling element bearings with suitable stiffness should be selected to keep enough separation margin. In addition, in establishing balance grade of a screw and bowl rotor, ISO G2.5 balance grade is more recommended than ISO G6.3, in particular balancing correction of a screw rotor based on ISO G2.5 grade is strongly recommended.

• 한국유체기계학회 논문집
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• 제10권3호
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• pp.47-54
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• 2007

A rotordynamic analysis was performed with a dry vacuum pump, which is a major equipment in modem semiconductor and LCD manufacturing processes. The system is composed of screw rotors, lobes picking air, helical gears, driving motor, and support rolling element bearings of rotors and motor. The driving motor-screw rotor system has a rated speed of 6,300rpm, and was modeled utilizing a rotordynamic FE method for analysis, which was verified through the results of its 3-D finite element model. As loadings on the bearings due to the gear action were significant in the system considered, each resultant bearing load was calculated determinately and indeterminately by considering the generalized forces of the gear action as well as the rotor itself. Each resultant bearing loading was used in calculating each stiffness of rolling element bearings. Design goals are to achieve wide separation margins of critical speeds and favorable unbalance responses of the rotor in the operating range. Then, a complex rotordynamic analysis of the system was carried out to evaluate its forward synchronous critical speeds, whirl natural frequencies and mode shapes, and unbalance responses under various unbalance locations. Results show that the entire system is well designed in the operating range. In addition, the procedure of rotordynamic analysis for dry vacuum pump rotor-bearing system was proposed and established.