• Title/Summary/Keyword: Optimal Pressure Control

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A study on EPB shield TBM face pressure prediction using machine learning algorithms (머신러닝 기법을 활용한 토압식 쉴드TBM 막장압 예측에 관한 연구)

  • Kwon, Kibeom;Choi, Hangseok;Oh, Ju-Young;Kim, Dongku
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.24 no.2
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    • pp.217-230
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    • 2022
  • The adequate control of TBM face pressure is of vital importance to maintain face stability by preventing face collapse and surface settlement. An EPB shield TBM excavates the ground by applying face pressure with the excavated soil in the pressure chamber. One of the challenges during the EPB shield TBM operation is the control of face pressure due to difficulty in managing the excavated soil. In this study, the face pressure of an EPB shield TBM was predicted using the geological and operational data acquired from a domestic TBM tunnel site. Four machine learning algorithms: KNN (K-Nearest Neighbors), SVM (Support Vector Machine), RF (Random Forest), and XGB (eXtreme Gradient Boosting) were applied to predict the face pressure. The model comparison results showed that the RF model yielded the lowest RMSE (Root Mean Square Error) value of 7.35 kPa. Therefore, the RF model was selected as the optimal machine learning algorithm. In addition, the feature importance of the RF model was analyzed to evaluate appropriately the influence of each feature on the face pressure. The water pressure indicated the highest influence, and the importance of the geological conditions was higher in general than that of the operation features in the considered site.

Development of an Artificial Neural Network Model for a Predictive Control of Cooling Systems (건물 냉방시스템의 예측제어를 위한 인공신경망 모델 개발)

  • Kang, In-Sung;Yang, Young-Kwon;Lee, Hyo-Eun;Park, Jin-Chul;Moon, Jin-Woo
    • KIEAE Journal
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    • v.17 no.5
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    • pp.69-76
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    • 2017
  • Purpose: This study aimed at developing an Artificial Neural Network (ANN) model for predicting the amount of cooling energy consumption of the variable refrigerant flow (VRF) cooling system by the different set-points of the control variables, such as supply air temperature of air handling unit (AHU), condenser fluid temperature, condenser fluid pressure, and refrigerant evaporation temperature. Applying the predicted results for the different set-points, the control algorithm, which embedded the ANN model, will determine the most energy efficient control strategy. Method: The ANN model was developed and tested its prediction accuracy by using matrix laboratory (MATLAB) and its neural network toolbox. The field data sets were collected for the model training and performance evaluation. For completing the prediction model, three major steps were conducted - i) initial model development including input variable selection, ii) model optimization, and iii) performance evaluation. Result: Eight meaningful input variables were selected in the initial model development such as outdoor temperature, outdoor humidity, indoor temperature, cooling load of the previous cycle, supply air temperature of AHU, condenser fluid temperature, condenser fluid pressure, and refrigerant evaporation temperature. The initial model was optimized to have 2 hidden layers with 15 hidden neurons each, 0.3 learning rate, and 0.3 momentum. The optimized model proved its prediction accuracy with stable prediction results.

A Numerical Study on Effects of Flow Analysis with Flow Control Valve on Turbine of OWC Type Wave Power Generator (유량 조절 밸브가 탑재된 진동수주형 파력발전장치의 터빈 내 유동해석을 위한 수치해석 연구)

  • Ro, Kyoung-Chul;Oh, Jae-Won;Kim, Gil-won;Lee, Jung-Hee
    • Journal of the Korean Society of Industry Convergence
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    • v.24 no.6_2
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    • pp.801-808
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    • 2021
  • In this paper, a numerical analysis was conducted on the effect of the flow control valve of a oscillation water column(OWC) type wave power generator turbine. The OWC wave power turbine operates with compressed air in the air chamber according to the change of wave height. When the wave height changes rapidly, a flow control valve is required due to overload of the turbine and reduced efficiency. Therefore, in this paper, a flow control valve with an opening angle of 60 degrees was installed in the front of the turbine, and the pressure drop, torque, and overall performance were calculated according to the change of turbine RPM and flow rate of turbine inlet. In conclusion, the flow control valve with an opening angle of 60 degrees affects when the turbine rotates at low rotation and the inlet flow rate is large. But it does not have a significant effect on overall turbine performance and it is necessary to find the optimal angle in the future works.

Influence of Pressure Toasting on Starch Ruminal Degradative Kinetics and Fermentation Characteristics and Gelatinization of Whole Horse Beans (Vicia faba) in Lactating Dairy Cows

  • Yu, P.;Goelema, J.O.;Tamminga, S.
    • Asian-Australasian Journal of Animal Sciences
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    • v.12 no.4
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    • pp.537-543
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    • 1999
  • Whole horse beans (Vicia faba cv. Alfred) (WHB) were pressure toasted at different temperatures of 100, 118 and $136^{\circ}C$ for 3, 7, 15 and 30 minutes in order to determine an optimal heating conditions to increase bypass starch (BPSt) as glucose source which is usually limiting nutrient in highly producing dairy cows in the Netherlands. Starch (St) Ruminal Degradative Kinetics and Fermentation Characteristics of (SRDC) of WHB were determined using in sacco technique in 4 lactating dairy cows fed 47% hay and 53% concentrate according to Dutch dairy cow requirements. Measured characteristics of St were soluble fraction (S), potentially degradable fraction (D) and rate of degradation (Kd) of insoluble but degradable fraction. Based on measured characteristics, percentage bypass starch (BPSt) was calculated according to the Dutch new feed evaluation system: the DVE/OEB system. Pressure toasting temperatures significantly affected starch gelatinization (p<0.01). Degradability of Starch in the rumen was highly reduced by pressure toasting (p<0.01). S varied from 58.2% in the raw WHB (RWHB as a control) to 19.6% in $136^{\circ}C/15min$. S was reduced rapidly with increasing time and temperature (p<0.01). D varied from 41.8% in RWHB to 80.5% in $136^{\circ}C/15min$. D fraction was enormously increased with increasing time and temperature (p<0.01). Kd varied from 4.9%h in RWHB to 3.4%/h in $136^{\circ}C/15min$. All these effects resulted in increasing %BPSt from 29.0% in RWHB to 53.1% in $136^{\circ}C/15min$. Therefore BPSt increased from 93.5 g/kg in RWHB to 173.5 g/kg in $136^{\circ}C/15min$. The effects of pressure toasting on %BPSt and BPSt seemed to be linear up to the highest values tested. Therefore no optimal pressure toasting conditions could be determined at this stage. But among 10 treatments, The treatment of $136^{\circ}C/15min$was the best with the highest BPSt content. It was concluded that pressure toasting was effective in shifting starch degradation from rumen to small intestine to increase bypass starch.

A Study on the Flow Characteristics of Reed Valve with Variable Geometric Variations for Cryogenic Linear Expander (극저온 선형 팽창기용 리드밸브의 기하학적 형상변화에 따른 유동 특성 연구)

  • Jeong, Eun A;Kim, Ji U;Yeom, Han Kil;Yun, So Nam
    • Journal of Drive and Control
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    • v.12 no.4
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    • pp.48-53
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    • 2015
  • This paper deals with the flow characteristics of a reed valve analyzed using computational dynamics(CFD) for optimal design. The seat sizes of the valve are modeled asØ6[mm] and Ø8[mm] to compare the flow characteristics. The inlet boundary condition is entered at 10[kPa], 15[kPa], 20[kPa], and 30[kPa] and the outlet boundary condition is set to the atmospheric pressure. The flow coefficient(C) and pressure loss coefficient(K) are calculated from the results of flow analysis. From the analysis results, it was confirmed that the flow coefficient of a reed valve having a seat size of Ø6[mm] is greater than that having a seat size of Ø8[mm], and the coefficient of pressure loss of a valve with a seat size of Ø6[mm] is lower than the Ø8[mm] size valve.

Basic Design of Hydrogen Liquefier Precooled by Cryogenic Refrigerator

  • Kim, Seung-Hyun;Chang, Ho-Myung;Kang, Byung-Ha
    • International Journal of Air-Conditioning and Refrigeration
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    • v.6
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    • pp.124-135
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    • 1998
  • A thermodynamic cycle analysis is performed for refrigerator-precooled Linde-Hampson hydrogen liquefiers, including catalysts for the ortho-to-para conversion. Three different configurations of the liquefying system, depending upon the method of the o-p conversion, are selected for the analysis. After some simplifying and justifiable assumptions are made, a general analysis program to predict the liquid yield and the figure of merit (FOM) is developed with incorporating the commercial computer code for the thermodynamic properties of hydrogen. The discussion is focused on the effect of the two primary design parameters - the precooling temperature and the high pressure of the cycle. When the precooling temperature is in a range between 45 and 60 K, the optimal high pressure for the maximal liquid yield is found to be about 100 to 140 bar, regardless of the ortho-to-para conversion. However, the FOM can be maximized at slightly lower high pressures, 75 to 130 bar. It is concluded that the good performance of the precooling refrigerator is significant in the liquefiers, because at low precooling temperatures high values of the liquid yield and the FOM can be achieved without compression of gas to a very high pressure.

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Analysis of Flow through High Pressure Bypass Valve in Power Plant (발전소용 고압 바이패스 밸브 내부 유동해석)

  • Cho, An-Tae;Kim, Kwang-Yong
    • The KSFM Journal of Fluid Machinery
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    • v.10 no.6
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    • pp.17-23
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    • 2007
  • In the present work, flow analysis has been performed in the steam turbine bypass control valve (single-path type) for two different cases i.e., case with steam only and case with both steam and water. The numerical analysis is performed by solving three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations. The shear stress transport (SST) model and $k-{\varepsilon}$ model are used to each different case as turbulence closure. Symmetry condition is applied at the mid plane of the valve while adiabatic condition is used at the outer wall of the cage. Grid independency test is performed to find the optimal number of grid points. The pressure and temperature distributions on the outer wall of the cage are analyzed. The mass flow rate at maximum plug opening condition is compared with the designed mass flow rate. The numerical analysis of multiphase mixing flow(liquid and vapor) is also performed to inspect liquid-vapor volume fraction of bypass valve. The result of volume fraction is useful to estimate both the safety and confidence of valve design.

Proposal of Analyis Method for PICV Characteristics Curve Using CFD in Hydronic System (밀폐형 수배관시스템에서 CFD를 활용한 복합밸브 특성곡선 해석 방법 제안)

  • Do, Gahyeon;Kim, Jinho;Park, Woopyeng;Min, Joonki
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.17 no.2
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    • pp.20-29
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    • 2021
  • In this study, it is proposed that an analysis method using charatersistics curve of PICV in the CFD simulation for hydronic system. From the results, the pressure drop characteristics appeared in the region of PICV at a specified flow rate. And the CFD results are in good agreement with the experimental results. Proposed analysis method is proved that the characteristics of PICV applied to the hydronic system were properly applied in the flow analysis. This result can be applied to PICV in the complex hydronic systems. Therefore, the optimal selection of PICV in hydronic system contribute the building energy saving.

Laboratory Tests to Verify the Vertically Automated Control Technique for Tripod Suction Buckets (실내실험을 통한 트라이포드 석션버켓의 수직도 자동제어 기술의 검증)

  • Xin Zhen-Hua;Lee Ju-Hyung
    • Journal of Wind Energy
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    • v.13 no.4
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    • pp.5-16
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    • 2022
  • In general, a tripod-shaped foundation secures its verticality by repeating penetration and drawing when suction penetration is performed. These repetitive tasks not only require a skilled operator, but are also less efficient. In this study, an automatic slope control system was developed to verify the slope control performance based on tripod suction in a sandy soil environment. The slope of the tripod suction base was measured, and the relative height of each suction bucket was calculated from the center of the tripod with a formula. The control program reduces the pump output of the suction bucket that penetrates too quickly by controlling the suction pressure of each suction bucket by sending an on/off signal to the suction pump according to the relative height. With such repetitive work, the relative height converges to 0 and the verticality of the structure can be secured while suction penetration is performed. As a result of the experiment, the effect of controlling the slope depending on the optimal limit setting height and penetration depth was confirmed, and a vertical degree within 0.5° was ensured. When installing a tripod suction bucket, the automatic tilt control method using the relative height is efficient without relying on the experience of the operator.

Design Principals of High Altitude Environmental Test Chamber (고도모사 환경챔버 개념 설계)

  • Owino, George;Gong, Chang-Deok;Choe, Gyeong-Ho
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.11a
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    • pp.403-406
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    • 2009
  • This research is based on the altitude temperature, pressure and humidity, as defined by MIL-HDBK-310 standard and modifies this conditions to conform to the new standard MIL-STD-810F and test procedure given in AIAA-2466 from this fundamental guideline optimal design and sizing of test section, inlet, exhauster duct, temperature and humidity control was performed.

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