A Hydraulic-Oil Pump System using SR Drive with a Direct Torque Control Scheme

Dong-Hee Lee,Tae-Hyoung Kim,Jin-Woo Ahn 전력전자학회 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.3

The hydraulic-oil pump is widely used for building machinery, brake systems of vehicles and automatic control systems due to its high dynamic force and smooth linear force control performance. This paper presents a novel direct instantaneous pressure control of the hydraulic pump system with SRM drive. The proposed hydraulic pump system embeds the pressure controller and direct instantaneous torque controller. Due to the proportional relationship between pump pressure and torque, pressure can be controlled by the motor torque directly. The proposed direct torque controller can reduce inherent torque ripple of SRM, and develop a smooth torque, which can increase the stability of the hydraulic pump. The proposed hydraulic pump system has also fast step response and load response. The proposed hydraulic pump system is verified by computer simulation and experimental results.

수리적 굴착손상영역에서의 지하수유동 특성에 관한 연구

박종성(Jong-Sung Park),류동우(Dong-Woo Ryu),류창하(Chang-Ha Ryu),이정인(Chung-In Lee) 한국암반공학회 2007 터널과지하공간 Vol.17 No.2

굴착손상영역 (EDZ)은 굴착으로 인해 현지 암반이 역학적으로 손상을 입게 되어 응력상태, 변위상태, 암반의 안정성, 지하수의 흐름상태 등에 변화가 일어나는 영역을 의미한다. EDZ의 역학적 특성과 관련한 많은 연구들이 수행되었지만, EDZ에서의 지하수 유동 특성에 관한 연구는 아직 부족한 수준이다. 본 연구에서는 굴착으로 인한 수리-역학 상호작용(coupling)에 의해 굴착면 주변의 수리적 간극값이 변하는 영역을 수리적 굴착손상영역이라 정의하고, 이를 3차원 분리단열망(DFN)에 적용시켜 보았다. 이를 통해 수리적 간극변화가 3차원 불연속 망에서의 전반적인 지하수 유동에 미치는 영향을 파악하였다. 또한 3차원 DFN 지하수 유동 해석 시 주로 이용되는 수두 조건과 유량 조건의 적용성을 고찰하였다. 해석 결과 수리-역학적 상호거동에 의해 발생하는 굴착면 주변의 수리적 간극변화는 터널 내부로 유입되는 유량에 큰 영향을 미치는 것으로 나타났다. 또한 DFN 해석 시 다양한 경계조건에 따른 상이한 결과를 토대로 보다 합리적인 경계조건 설정에 대한 방향을 제시하였다. 마지막으로 실제 현장에서 수리해석을 실시한 자료를 바탕으로 수리적 간극 값의 변화를 고려할 때와 고려하지 않을 때의 유입유량 차이를 통해, 3차원 지하공동의 지하수 유동 해석 시 수리적 간극 값의 변화를 고려하는 것이 보다 더 보수적인 결과를 나타내는 것을 확인하였다. The excavation damaged zone (EDZ) is an area around an excavation where in situ rock mass properties, stress condition, displacement, groundwater flow conditions have been altered due to the excavation. Various studies have been carried out on EDZ, but most studies have been focused on the mechanical bahavior of EDZ by in situ experiment. Even though the EDZ could potentially form a high permeable pathway of groundwater flow, only a few studies were performed on the analysis of groundwater flow in EDZ. In this study, the ‘hydraulic EDZ’ was defined as the rock zone adjacent to the excavation where the hydraulic aperture has been changed due to the excavation. And hydraulic EDZ (hydraulic aperture changed zone) estimated by two-dimensional DEM program was considered in three-dimensional DFN model. From this approach the groundwater flow characteristics corresponding to hydraulic aperture change were examined. Together, a parametric study was performed to examine the boundary conditions that frequently used in DFN analysis such as constant head or constant flux condition. According to the numerical analysis, hydraulic aperture change induced by the hydraulic-mechanical interaction becomes one of the most important factors influencing the hydraulic behavior of jointed rock masses. And also from this study, we suggest the proper boundary condition in three-dimensional DFN model.

A Hydraulic-Oil Pump System using SR Drive with a Direct Torque Control Scheme

Lee, Dong-Hee,Kim, Tae-Hyoung,Ahn, Jin-Woo The Korean Institute of Power Electronics 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.3

The hydraulic-oil pump is widely used for building machinery, brake systems of vehicles and automatic control systems due to its high dynamic force and smooth linear force control performance. This paper presents a novel direct instantaneous pressure control of the hydraulic pump system with SRM drive. The proposed hydraulic pump system embeds the pressure controller and direct instantaneous torque controller. Due to the proportional relationship between pump pressure and torque, pressure can be controlled by the motor torque directly. The proposed direct torque controller can reduce inherent torque ripple of SRM, and develop a smooth torque, which can increase the stability of the hydraulic pump. The proposed hydraulic pump system has also fast step response and load response. The proposed hydraulic pump system is verified by computer simulation and experimental results.

Response of coal rock apparent resistivity to hydraulic fracturing process

Song, Dazhao,Wang, Enyuan,Qiu, Liming,Jia, Haishan,Chen, Peng,Wei, Menghan Techno-Press 2018 Geomechanics & engineering Vol.14 No.6

In order to explore the comprehensive evaluation means of the extent of hydraulic fracturing region in coal seams, we analyzed the feasibility of detecting the response of coal rock direct current (DC) apparent resistivity to hydraulic-fracturing using Archie's theory, and conducted experimental researches on the response of DC resistivity in the hydraulic fracturing process using small-scale coal rock samples. The results show that porosity and water saturation are the two factors affecting the apparent resistivity of coal rock while hydraulic fracturing. Water has a dominant effect on the apparent resistivity of coal rock samples. The apparent resistivity in the area where water flows through is reduced more than 50%, which can be considered as a core affect region of hydraulic fracturing. Stress indirectly impacts the apparent resistivity by changing porosity. Before hydraulic fracturing, the greater axial load applied, the more serious the rupture in the samples, resulting in the greater apparent resistivity. Apparent resistivity testing is a potential regional method to evaluate the influence range of hydraulic fracturing in coal seams.

Experimental Investigation of the Hydraulic Performance of a Hydraulic-Jump-Stepped Spillway

Yu Zhou,Jianhua Wu,Fei Ma,Shangtuo Qian 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.10

For a traditional stepped spillway, low energy dissipation and cavitation damage may occur when the unit discharge is larger than a limit due to reduced air entrainment in the flow. In the present work, a new type of stepped spillway called hydraulic-jump-stepped spillway (HJSS) was developed, and the air was efficiently entrained into the flow by means of a hydraulic jump in the aeration basin, which was an aeration element of this stepped spillway. Compared with the traditional stepped spillway, various aspects of the hydraulic performance of the HJSS were experimentally investigated, including the flow pattern, energy dissipation, air entrainment characteristics and time-averaged pressure. Physical model results demonstrated that the HJSS achieved a higher energy dissipation, a more favorable air entrainment performance, and a more reasonable pressure distribution. The HJSS successfully increased the unit discharge from 50 – 60 m2/s for a traditional stepped spillway to 101.47 m2/s.

Hydraulic-jump behavior of a thin film flowing down an inclined plane under an electrostatic field

김효,김광석 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.1

The hydraulic-jump phenomenon of a thin fluid layer flowing down an inclined plane under an lectrostatic field is explored by using a global bifurcation theory. First, the existence of hydraulic-hump wave has been found from heteroclinic trajectories of an associated ordinary differential equation. Then, the jump behavior has been characterized by introducing an intensity function on the variations of Reynolds number and surfave-wave speed. Finally, we have investigated the nonlinear stability of traveling shock waves triggered from a hydraulic jump by integrating the initial-value problem directly. At a given wave speed there exists a certain value of Reynolds number beyond which a time-dependent buckling of the free surface appears. Like the other wave motions such as periodic and pulse-like solitary waves, the hydraulic-jump waves are also found to become more unstable as the electrostatic field is getting stronger

유압식 선로전환기의 Cause-consequence 분석에 관한 연구

이종규(Jong-Kyu Lee),최승호(Seung-Ho Choi) 한국철도학회 2013 한국철도학회 학술발표대회논문집 Vol.2013 No.11

선로전환기는 전기 모터식, 공압식 및 유압식 등이 있다. 선로전환기는 철도시스템의 핵심부품으로 고장이 발생하여 기능을 정확하게 동작하지 않을 경우 철도운용에 막대한 지장을 초래한다. 경부고속철도 2 단계(동대구-부산)에 Hydrostar 의 유압식 선로전환기가 설치되어 운용되고 있다. 이 유압식 선로전환기의 요구된 성능을 유지하기 위해서 Cause-consequece 분석을 필요로 한다. 본 논문에서는 유압식 선로전환기의 기능분석을 통한 모델링, FTA 를 수행하였으며, 각 기능에 대한 Cause-Consequence 분석을 수행하여 Cause-consequece diagram 을 도출하였다. The types of switch machine are electric motor, pneumatic and hydraulic. When the switch machine, which is the critical component of railway system, has a problem and does not work exactly, it results in enormous hindrance. The hydraulic switch machine of Hydrostar is installed at Gyeong-bu Highspeed Railway Project Phase Ⅱ(Dongdaegu - Pusan) and it is now operating. Cause-consequence analysis is required to maintain performance of hydraulic switch machine. This paper proposes a FTA analysis method that use the functional analysis of hydraulic point machine and presents Cause-consequence diagram by performing Cause-consequence analysis for each function.

Hydraulic control rod drive mechanism concept for passive in-core cooling system (PINCs) in fully passive advanced nuclear power plant

Kim, I.G.,Bang, I.C. Elsevier 2017 Experimental thermal and fluid science Vol.85 No.-

<P>Safety systems in nuclear power plants have become an important research topic owing to the significant impact of nuclear disasters. Herein, a passive in-core cooling system is proposed to delay the time of fuel melting and to enhance the safety of nuclear power plants during station blackout accidents. The passive in-core cooling system consist of a hydraulic control rod drive mechanism and a hybrid control rod assembly that combines the heat pipes with the control rods. To achieve the unique features of its system, hydraulic control rod drive mechanism is designed using hybrid control rods located inside the reactor vessel. The study deals with the test of a 4-finger hydraulic-rod control system as one of the components of the passive in-core cooling system. The experimental study focuses on the force-induced system based on the pressure differential between the grooved cylinders, which controls the elevation of the upper cylinder, i.e., the hybrid control rod assembly. As a result, the stable inlet flow and position were found at each step, yielding a well predicted holding flow, in accordance to the force balance equation. In withdrawal steps, reduced inlet flow was not observed, but reduced pressure was observed due to the narrow gap between the cylinders during the lift delay condition. Drop test results yield good agreement with those predicted by the simple model, resulting in percentage errors within +/- 15%. In the heat removal test, the time taken to reach the maximum pool temperature was increased by approximately 2.5 times by using the refrigerant as the working fluid of the hybrid control rod. The test shows the behavioral features of the hydraulic control rod drive mechanism in conjunction with the hybrid control rod, and the possibility of the in-core application of the hydraulic drive system to PINCs. (C) 2017 Elsevier Inc. All rights reserved.</P>

댐저수지의 남조류 수화에 대한 간헐식 폭기장치의 효과

이정호,Lee, Jeong-Ho 한국조류학회(藻類) 2004 ALGAE Vol.19 No.1

The purpose of this study is to assess the effects that hydraulic-gun-aerators have on cyanobactedial bloom in Sayeon Dam Reservoir in Ulsan City, Korea. A total of nine hydraulic-gun-aerators are in operation at the reservoir withe 100 m spacing between each aerator to control severe cyanobacterial bloom in the dam reservoir. The field studies were performed an total four times at two sampling stations in the reservoir from July to August in 2001. The standing crops of phytoplankton did not changed significantly by the operation. The cell concentration of the cyanobacteria at the surface layer were reduced about 10%, which is a poor result for the dispersing cyandobacteria deeper into the water. The average surface temperature during the study was reduced by 2.0$^{\circ}C$ by the hydraulic-gun-aerators. The effect of the operation on the vertical distribution of DO concentration was clear. However, the hydraulic-gun-aerators were not expected to have an effect in the lowest layer of the hypolimnion. In the study, it was proposed that installation distance between each hydraulic-gun-aerator would be proper when they are apart about 120 m based on DO depth profiles.

투모드 하이브리드 자동차의 유압제어 시스템 시뮬레이터 개발

김용하(Yongha Kim),전영호(Youngho Jun),김현수(Hyunsoo Kim) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11

In this paper, a performance simulator of a hydraulic-control system was investigated for a two-mode hybrid electric vehicle (HEV). Dynamic models of each solenoid valve and hydraulic-control system were developed and validated by experiments. The hydraulic characteristics of the solenoid valve and hydraulic-control system were analyzed via experimentation and simulation. Using the performance simulator of the hydraulic-control system and the powertrain model, a performance simulator for a two-mode HEV was developed and shift performances were evaluated. It was found from the simulation results that torque change during the shift can be reduced via minimizing speed difference between both sides of a clutch by motor/generator control and solenoid valve pressure control.