• 한국분무공학회지
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• 제22권2호
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• pp.62-68
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• 2017

It is important to study on the combustion instability to develop liquid rocket engines for preventing lower combustion efficiency and destruction of combustion chamber. There are many researches on simplex injector with liquid pulsation to solve this problem. In real rocket engine system, however, they use coaxial injectors. Therefore, research on coaxial injector with liquid pulsation is essential. In this study, we investigate dynamic characteristics of gas centered swirl coaxial injector varying tangential inlet diameter. A mechanical pulsator was used to generate an excitation in the liquid flow, and the response characteristics of the injector were confirmed. As tangential inlet diameter increased, mass flow rates increased and spray angle decreased. As tangential inlet diamter decreased, gain decreased because the pressure fluctuation in the injector manifold rarely passed through the inlet. Additionally, it was confirmed that a sufficiently small tangential inlet served as a damper.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.1020-1028
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• 2021

The nuclear reactor coolant pump transferring heat energy inherently brings with it the unsteady flow and inevitably threatens to the safe operation of the pump unit, especially with the pressure pulsation induced by the rotor-stator interaction. In this paper, the characteristics of pressure pulsation of the diffuser in a nuclear reactor coolant pump were investigated by the numerical simulation with experimental validation. Pressure pulsation signals measured synchronously from sensors mounted on the radial diffuser of a model pump were analyzed via Welch's method. Frequency components induced by the rotor-stator interaction can be revealed by the diameter mode analysis method. The pressure pulsation of the diffuser is dominated by the blade passing frequency and its harmonics, which are free from the effect of flow rate and rotational speed while the corresponding amplitudes are easily affected by different operational conditions and measuring positions. The non-uniformity is much more affected by the rotational speed than the flow rate. This research is helpful for further work to reduce the pressure pulsation for the reactor coolant pump.

• 한국생산제조학회지
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• 제26권2호
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• pp.151-157
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• 2017

Hydraulic equipment have been traditionally used for constructing machines with high power density and durability. In particular, pumps and motors are considered essential equipment, and are consistently investigated to find suitable methods for optimal utilization of their characteristics. A kinematic analysis of a swash-plate-type piston motor model using the hydraulic analysis program SimulationX$^{(R)}$ to model a nine-piston motor and simulate a swash-plate angle with a low-pulsation and high-efficiency performance of the motor has been provided in this paper. Finally, along with the theoretical consideration of the stroke, the effect of changing strokes and notch shape (V, U, non-type) on the pulsation is simulated to analyze and determine the effects of reduction in pulsation. The optimal swash-plate angle and stroke thus obtained will reduce the trial and error in future design.

• 설비공학논문집
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• 제14권7호
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• pp.592-598
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• 2002

The characteristics of a pulsating flow field from a heated block representing heat-dissipating electronic component in a channel have been numerically investigated. At the channel inlet a pulsating sinusoidal flow is imposed. The Reynolds number based on the channel height (H) is fixed at Re=500, and the forcing frequency is varied in the range of $0\leqSt\leq2$. Numerical results on the time-dependent flow field are obtained and averaged over a cycle of pulsation. The effect of the important governing parameters such as the Strouhal number is investigated in detail. The results indicate that the recirculating flow behind the block is substantially affected by the pulsation frequency. To characterize the periodic vortex shedding due to the inflow pulsation, numerical flow visualizations are carried out.

• 대한의용생체공학회:의공학회지
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• 제23권5호
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• pp.391-395
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• 2002

수두증 환자를 치료하기 위해 머리에 시술 되는 션트밸브가 받는 뇌압 펄스가 밸브의 유량조절 특성에 미치는 영향을 수치적으로 해석하였다. 션트밸브를 통한 유량을 계산하기 위하여 밸브 다이아프램이 형성하는 유량 오리피스를 모델링 하여 맥동압력과 변동하는 압력에 의한 다이아프램의 움직임을 고려하였다. 연구 결과, 압력 펄스와 이에 따른 다이아프램의 움직임에 의하여 유량이 40% 이상 증가함을 보였다. 이 결과는, 뇌실에 시술 되는 션트밸브의 압력-유량 조절특성이 제조 직후 맥동이 없는 유량을 공급하는 시린지 펌프를 사용하여 구한 실험 결과와 상당히 다르다는 사실을 보여주었다.

• 한국자동차공학회논문집
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• 제9권1호
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• pp.37-44
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• 2001

This study is focused on the development of a new muffler. A control valve installed in the exhaust system is operated by torsion springs, and its open angle is controlled automatically corresponding to the engine operating conditions. The experiments were done using an exhaust system simulator having the same pulsation wave frequency and similar pulsation propagation characteristics of a real exhaust system. The purpose of this study is to develop a new muffler system which has improved noise reduction quality and less power loss than conventional mufflers and electronic-control mufflers.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.10-16
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• 2005

Recently, the international regulations about the exhaust emissions of the motorcycle have been strengthened. The electrically controlled fuel injection type motorcycle has been emphasized to meet with this regulation. However, since the pulsation phenomenon happens in the intake port of the motorcycle because of the characteristic of high speed and the smaller layout than the passenger car, there are many difficulties to select the factor about control parameters needed to develop the ECU system. In this paper, the pulsation values measured from the engine test were compared with the calculated one by WAVE, and it was analyzed the pulsation characteristic according to the driving condition and estimated the mass flow rate. This research showed that the lowest point of the pressure gets lowin the low load and the pulsation of pressure were increased in the high load. Also, the simulation program was verified by showing good prediction of the pulsation and air mass flow rate.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.648-654
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• 2011

The feed-water piping system constitutes a complex flow impedance network incorporating dynamic transfer characteristics which will amplify some pulsation frequencies. Understanding pressure pulsation waves for the feed-water recirculation piping system with cavitation problem of flow control valve is very important to prevent acoustic resonance. Feed water recirculation piping system is excited by potential sources of the shock pulse waves by cavitation of flow control valve. The pulsation becomes the source of structural vibration at the piping system. If it coincides with the natural frequency of the pipe system, excessive vibration results. High-level vibration due to the pressure pulsation affects the reliability of the plant piping system. This paper discusses the piping vibration due to the effect of shock pulsation by the cavitation of the flow control valves for the recirculation piping of feed-water pump system in combined cycle power plants.

• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1116-1122
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• 2008

The reciprocating type hydrogen compressor has a pulsation due to the reciprocative characteristics which results in noise and vibration. Snubber is installed for the relaxation of pulsation, but it causes reduction of compressor efficiency because of pressure loss. Five types of snubber were modeled for the numerical investigation of the effect of the relative position of inlet and outlet and buffer angle on the pulsation amplitude and pressure loss. MSC/NASTRAN is used as a numerical tool to identify the vibration characteristic of each type. Frequency responses in forced vibration mode are compared for various cases and buffer angles.

• 한국음향학회지
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• 제16권6호
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• pp.68-75
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• 1997

본 연구에서는 맥동류에 의한 파이프 계의 진동응답을 고찰하기 위해 전달행렬법을 사용하였다. 유속과 압력을 시간과 위치의 함수로 다루어 유체와 파이프간의 상호작용을 파동방정식으로 정립하고, 각 파동방정식으로부터 전달행렬을 직접 유도하였다. 맥동류로부터 유발되는 파이프 계의 동적응답은 맥동으로부터 발생하는 변동유속과 압력에 의존되는 것으로 나타났으며, 공진 근처에서 맥놀이 현상이 관찰되었다. 파이프 계의 동적거동은 파이프 내부의 유동양상과 동일한 응답특성을 나타내고, 내부 유동유체에 의해 결정된다.