• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
• /
• pp.116-121
• /
• 2000

During the operation, fatigue failures and cracks of duct plate due to excessive duct vibration occurred in the fan-duct systems of fossil fueled boilers. We measured static pressure variation(pressure pulsation) in the outlet, and also measured vibration at the outlet duct of a centrifugal fan. It was found that strong pressure Pulsation caused by the inlet vortex occurred in inlet vane of centrifugal fan in the middle range of vane opening. Thus, excessive duct vibration is caused by strong pressure pulsation. In this paper, it is shown that the frequency and amplitude of pressure pulsation depend mainly on vane opening and are compared with duct vibration. Also, effective solution for reducing pressure pulsation and vibration are presented.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
• /
• pp.231-237
• /
• 2003

A numerical study has been conducted to investigate the effect of an inlet flow pulsation on mixing of two solutions with different concentrations in a micro conduit. We treat an unsteady, incompressible and two-dimensional flow through a micro conduit by adopting the momentum equations with the electrostatic force due to streaming current and the concentration equation. The feasibility of the inlet flow pulsation to enhance the mixing process inside the micro conduit is carefully examined by varying the inlet pulsation frequency. When a low-frequency pulsation is induced at the inlet, the interface between two solutions with different concentrations becomes wavy, which results in mixing enhancement. As the pulsation frequency increases, the waviness of the interface becomes meager, and the concentration gradients at the interface approach the value for the non-pulsating steady flow.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 추계학술대회논문집
• /
• pp.82-87
• /
• 2000

During the operation, fatigue failures and cracks of duct plate due to excessive duct vibration occurred in the fan-duct systems of fossil fueled boilers. We measured static pressure variation(pressure pulsation) in the outlet, and also measured vibration at the outlet duct of a centrifugal fan. It was found that strong pressure pulsation caused by the inlet vortex occurred in inlet vane of centrifugal fan in the middle range of vane opening. Thus, excessive duct vibration is caused by strong pressure pulsation. In this paper, it is shown that the frequency and amplitude of pressure pulsation depend mainly on vane opening and are compared with duct vibration. Also, effective solution for reducing pressure pulsation and vibration are presented.

• 한국소음진동공학회논문집
• /
• 제13권3호
• /
• pp.194-201
• /
• 2003

During the operation, fatigue failures and cracks of duct plate due to excessive duct vibration occurred in a fan-duct system of fossil fueled boilers. We measured static pressure variation (pressure pulsation) in the outlet, and also measured vibration at the outlet duct of a centrifugal fan. It was found that strong pressure pulsation caused by the inlet vortex occurred in inlet vane of centrifugal fan in the middle range of vane opening. Thus, excessive duct vibration is caused by strong pressure pulsation. In this Paper, it is shown that the frequency and amplitude of pressure pulsation depend mainly on vane opening and are compared with duct vibration. Also, effective solution for reducing pressure pulsation and vibration are presented.

• 한국분무공학회지
• /
• 제22권2호
• /
• pp.62-68
• /
• 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.

• Journal of Advanced Marine Engineering and Technology
• /
• 제31권8호
• /
• pp.947-953
• /
• 2007

Occurrence of pressure pulsation in positive displacement hydraulic turbine is one of the principal problems which should be cleared to improve the turbine performance and to put the turbine to practical use. Therefore, present study is tried to examine the occurrence mechanism and characteristics of the pressure pulsation CFD analysis and experimental measurement are implemented in this study to clarify the phenomena of unsteady pressure pulsation. The results show that occurrence reason of the pressure pulsation is not only due to a series of opening and closing of the chamber formed between rotor and casing wall but also due to the variation of rotational speed of following rotor. The pressure pulsation causes torque variation and the curve patterns of the torque variation conforms to that of the pressure pulsation. Pressure in the chamber is equal to the averaged value of inlet and outlet pressures. Sudden pressure decrease by accelerated through-flow between lobe and casing wall results in torque loss.

• 한국분무공학회지
• /
• 제14권1호
• /
• pp.34-38
• /
• 2009

This paper presents the pulsation of carburetor inlet and outlet pressure of a small SI gasoline engine. The engine used in this paper is a 23cc, single cylinder, diaphragm carburetor, two-stroke, air-cooled for brush cutter. The rpm and pressure wave pulsation at the inlet and the outlet of carburetor were measured and analysed for the understand of the internal air flow into the barrel on the diaphragm carburetor. These data should be used for the development of the duel fuel injection system for gasoline and LPG. The results showed that the carburetor inlet pressure variations were very steady, but the pressure variations at carburetor outlet were very sensitive to the pressure variation into the crank case and were to similar independently to the engine speed on partial opened throttle conditions. According to increasing engine speed, the pressure waves started to come out and be developed after closing the intake port of the engine at carburetor outlet. Reverse flow occurred on the WOT (wide open throttle) condition.

• Journal of Mechanical Science and Technology
• /
• 제20권10호
• /
• pp.1626-1637
• /
• 2006

The pressure pulsation due to the gear geometry of the gerotor (generalized rotor) pump mainly occurs in an instant that the chamber of the gerotor enters the delivery port and leaves the suction one. Such a pressure pulsation may result in undesirable vibration and noise of pump components as well as cavitation in hydraulic system. Therefore, it is very important to examine the pressure characteristic of the gerotor pump at its design and analysis stages. In this paper, in order to reduce the pressure pulsation in the gerotor pump, the port plate with the relief grooves is designed by referring to as notch of vane pump and relief groove of piston pump. A series of the theoretical analyses on the pressure pulsation is performed in consideration of various design parameters of the port plate, including the installation positions of the port inlet/outlet and the groove width, and the operating conditions such as rotational velocity and delivery pressure.

• 한국자동차공학회논문집
• /
• 제15권4호
• /
• pp.132-138
• /
• 2007

Experimental results of pulsating pressure behavior inside a chamber have been confirmed by computational work. Inside-cylinder pressure shows unstable condition at low rpm. This is caused by plate-type suction valve. It has effect up to inlet of the chamber. But trembling phenomenon is reduced as the pressure is enlarged by increasing the rpm. Result comparison between experimental and numerical analysis shows pulsation reduction is affected by the chamber. We can confirm that compressible effect of the working flow is shown at chamber inlet by increasing rpm. On the other side, this effect is declined at chamber outlet by increasing rpm. It means outlet pressure is going on balance with atmosphere pressure. Buffer plate-type chamber has efficiency of pulsation flow reduction.

• Nuclear Engineering and Technology
• /
• 제55권4호
• /
• pp.1310-1323
• /
• 2023

A reactor coolant pump (RCP) is essential for transporting coolant in the primary loop of pressurized water reactors. In the advanced passive reactor, the absence of a long pipeline between the steam generator and RCP serves as a transition section, resulting in a non-uniform flow field at the pump inlet. Therefore, the characteristics of the pump should be investigated under non-uniform flow to determine its influence on the pump. In this study, the pressure pulsation characteristics were examined in the time and frequency domains, and the sources of low-frequency and high-amplitude signals were analyzed using wavelet coherence analysis and numerical simulation. From computational fluid dynamics (CFD) results, non-uniform inflow has a great effect on the flow structures in the pump's inlet. The pressure pulsation in the pump at the rated flow increased by 78-128.7% under the non-uniform inflow condition in comparison with that observed under the uniform inflow condition. Furthermore, a low-frequency signal with a high amplitude was observed, whose energy increased significantly under non-uniform flow. The wavelet coherence and CFD analysis verified that the source of this signal was the low-frequency pulsating vortex under the steam generator.