• Title/Summary/Keyword: Open Loop

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Study on the Capacity Design Tool Development for Open-loop Ground Heat Exchanger (개방형 지중열교환기 용량 설계 방법에 관한 연구)

  • Ryu, Hyung-Kyou;Choi, Seung-Hyuck;Yun, Hi-won;Gim, Yu-Seung
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.13 no.2
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    • pp.9-15
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    • 2017
  • When applying geothermal systems in cities such as seoul where high density development prevails, the selection of geothermal system capable of obtaining a large capacity in the limited grounds is necessary. In this study, an easy-to-use design tool is developed in the form of spreadsheet by applying the calculation theory of existing closed-loop vertical ground heat exchanger that can be used in the early design stage of the open-loop ground heat exchanger. By only using the maximum cooling and heating load, it is possible to calculate optimal design open-loop ground heat exchanger. Further research is needed, we are plan to improve the program considering the heat loss of groundwater flowing in the inner casing, G-Function for Open-Loop, and verification by applying actual projects.

Turbopump+Gas generator Open-loop coupled test (터보펌프+가스발생기 개회로 연계시험)

  • Kim, Seung-Han;Nam, Chang-Ho;Kim, Cheul-Woong;Moon, Yoon-Wan;Seol, Woo-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.11a
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    • pp.125-128
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    • 2008
  • As a interstage of the 30tonf level LOx/kerosene liquid rocket engine development, turbopump-gas generator open-loop coupled tests are performed. Test schematic and test results of open-loop coupled tests are presented. In engine system operation environment simulating combustion chamber by flow control orifice, chill-down procedure, startup characteristics, nominal operability of turbopump+gas generator open-loop coupled Test Plant are confirmed The results of open-loop coupled test were used for the preparation on turbopump+gas generator closed-loop test.

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Study on Turbopump-Gas Generator Open-Loop Coupled Test (터보펌프-가스발생기 개회로 연계시험 연구)

  • Kim, Seung-Han;Nam, Chang-Ho;Kim, Cheul-Woong;Moon, Yoon-Wan;Seol, Woo-Seok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.5
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    • pp.563-568
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    • 2010
  • Turbopump-gas generator open-loop coupled tests are performed during the development of a 30tonf-LOx/Kerosene rocket engine. In the turbopump-gas generator open-loop tests, the propellants to gas generator are supplied from the outlets of turbopump, while the gas exhausted from the gas generator is vented out to the atmosphere, instead of being used to turbine driving. This paper presents the objectives, procedure, and results of the open-loop coupled test, in addition to a schematic representation of the test apparatus and the operating conditions for the test facility system and control system. The results of turbopump-gas generator open-loop coupled test confirm chill-down procedure, startup characteristics, nominal operability and smooth shutdown of the open-loop coupled Test Plant in test conditions simulating engine system operation environment.

Design of a Dual-Band Bandpass Filter Using an Open-Loop Resonator

  • Im, Hyun-Seo;Yun, Sang-Won
    • Journal of electromagnetic engineering and science
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    • v.17 no.4
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    • pp.197-201
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    • 2017
  • In this paper, we present a novel design for a dual-band bandpass filter (BPF) based on the conventional second-order, open-loop BPF. By adding series resonant circuits to the open ends of the resonator, we can create two resonant modes from the even and odd modes. One pair of the even and odd modes constitutes the upper passband, while the other pair constitutes the lower passband. By adding another series resonant circuit to the open-loop resonator, we can control the bandwidth of either the upper passband or the lower passband. We can replace the series resonant circuits with simple microstrip line resonators. A dual-band BPF working at both Wi-Fi bands (2.4 GHz and 5.8 GHz bands) is designed based on the proposed method and is tested. The measured and simulated results show excellent agreement.

Feedback Control for Expanding Range and Improving Lineraity of Microaccelerometers (가속도계의 동작범위 확장와 선형성 향상을 위한 피드백 제어)

  • Park, Yong-Hwa;Park, Sang-Jun;Choi, Byung-Doo;Ko, Hyoung-Ho;Song, Tae-Yong;Lim, Genu-Won;Huh, Kun-Soo;Park, Jahng-Hyon;Cho, Dong-il
    • Journal of Institute of Control, Robotics and Systems
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    • v.10 no.11
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    • pp.1082-1088
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    • 2004
  • This paer presents a feedback-controlled, MEMS-fabricated microaccelerometer($\mu$XL). The $\mu$XL has received much commercial attraction, but its performance is generally limited. To improve the open-loop performance, a feedback controller is designed and experimentally evaluated. The feedback controller is applied to the x/y-axis $\mu$XL fabricated by sacrificial bulk micromachining(SBM) process. Even though the resolution of the closed-loop system is slightly worse than open-loop system, the bandwidth, linearity, and bias stability are stability are significantly improved. The noise equivalent resolution of open-loop system is 0.615 mg and that of closed-loop system is 0.864 mg. The bandwidths of open-loop and closed-loop system are over 100Hz. The input range, non-linearity and bias stability are improved from $\pm10\;g\;to\;\pm18g$, from 11.1%FSO to 0.86%FSO, and from 0.221 mg to 0.128 mg by feedback control, respectively.

The Comparison of Reliability for Change Single Loop Configuration in Radial Power Distribution System (수지상 배전계통을 단일루프로 구조 변경시 신뢰도 비교)

  • Lee, Hee-Tae;Kim, Jae-Chul;Kim, Ju-Yong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.8
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    • pp.1472-1478
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    • 2009
  • The domestic power distribution system is operating in an open loop mode; however, it already has a loop structure. Power distribution systems must be changed for bi-directions power supply for smart networks due to a changing of paradigm in electric power industry. The simplest bi-directions distribution networks can make it closing of normally open switch. However, bi-directions power supply is very difficulty to be operated and there are many parts which it must study. This paper presented various models that are able to change a radial system for loop structures. Further, we compared the reliability index for each model by evaluating the amount of improvement reliability required in radial power distribution system. In addition, we calculated CIC(Customer Interruption Cost) for each model by comparing and analyzing.

Research on Low Phase Noise Oscillator Using Microstrip Square Open Loop Resonator (Microstrip Square Open Loop Resonator를 이용한 저위상 잡음 발진기에 관한 연구)

  • Park Eun-Young;Seo Chulhun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.1 s.104
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    • pp.17-23
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    • 2006
  • This paper has presented a low phase noise oscillator using a square open loop with microstrip structure. A square open loop resonator has a large coupling coefficient value, which makes a high Q value, and has reduced phase noise. This oscillator has presented the oscillation frequency of 5.84 GHz, harmonics of -15.83 dBc and the phase noise of -111.17 dBc/Hz at the offset frequency of 100 kHz. In conclusion, the proposal structure has improved phase noise of 15 dB at the offset frequency of 100 kHz compared with the conventional structure of oscillator.

Simulation of Open-Loop Borehole Heat Exchanger System using Sand Tank Experiment and Numerical Model (토조 및 수치모형을 이용한 개방형 지중 열교환 시스템 모의)

  • Lee, Seong-Sun;Bae, Gwang-Ok;Lee, Kang-Kun
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.11a
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    • pp.489-492
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    • 2007
  • Understanding the thermohydraulic processes in the aquifer is necessary for a proper design of the aquifer thermal energy utilization system under given conditions. Experimental and numerical test were accomplished to evaluate the relationship between the geothermal heat exchanger operation and hydrogeological conditions in the open-loop geothermal system. Sand tank experiments were designed to investigate the open-loop geothermal system. Water injection and extract ion system as open-loop borehole heat exchanger was applied to observe the temperature changes in time at injection well, extraction well and ambient groundwater. The thermohydraulic transfer for heat storage was simulated using FEFLOW for two cases of extraction and injection phase operation in sand tank model. As one case, the movement of the thermal plume was simulated with variable locations of injection and extraction well. As another case, the simulation was performed with fixed location of injection and extraction well. The simulation and experimental results showed that the temperature distribution depends highly on the injected water temperature and the length of injection time and the groundwater flow and pumping rate sensitively affect the heat transfer.

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Analysis of the Initial Cost Payback Period on the Open-loop Geothermal System Using Two Wells (복수정을 이용한 개방형 지열 시스템의 초기투자비 회수기간 분석)

  • Cho, Jeong-Heum;Nam, Yujin
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.29 no.3
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    • pp.119-126
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    • 2017
  • Recently, ground source heat pump systems are being used in buildings for cooling and heating to reduce greenhouse gas and save energy. However, ground source heat pump systems mainly use the vertical closed-loop geothermal system design rather than the open-loop geothermal system design. This is due to a lack of knowledge and few research feasibility studies. In this research, a dynamic thermal analysis numerical simulation based on a standard house model was conducted for an open-loop geothermal system. Based on heating load analysis results, the life cycle costs of a standard house using an open two-well geothermal system were analyzed and compared with a vertical closed-loop geothermal system, and a diesel boiler. As a result, it was found that using an open two-well geothermal system shows economic return on investment after three years.

Electrically-induced actuation for open-loop control to cancel self-excitation vibration

  • Makihara, Kanjuro;Ecker, Horst
    • Smart Structures and Systems
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    • v.9 no.2
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    • pp.189-206
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    • 2012
  • This paper focuses on the actuation system combined with a piezoelectric transducer and an electric circuit, which leads to a new insight; the electric actuation system is equivalent to mechanical variable-stiffness actuation systems. By controlling the switch in the circuit, the electric status of the piezoelectric transducer is changed, and consequently a variable-stiffness mechanism is achieved on the electric actuator. This proposed actuator features a shift in the equilibrium point of force, while conventional electrically-induced variable-stiffness actuators feature the variation of the stiffness value. We intensively focus on the equilibrium shift in the actuation system, which has been neglected. The stiffness of the variable-stiffness actuator is periodically modulated by controlling the switch, to suppress the vibration of the system in an open-loop way. It is proved that this electric actuator is equivalent to its mechanical counterpart, and that the electrical version has some practical advantages over the mechanical one. Furthermore, another kind of electrically-induced variable-stiffness actuator, using an energy-recycling mechanism is also discussed from the viewpoint of open-loop vibration control. Extensive numerical simulations provide comprehensive assessment on both electrically-induced variable-stiffness actuators employed for open-loop vibration control.