• Title/Summary/Keyword: External valve

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Characteristics of Performance and Back-Fire for External Mixture Hydrogen Fueled Engine without Valve Overlap Period (밸브 오버랩 기간이 없는 흡기관 분사식 수소기관의 성능 및 역화특성)

  • Lee, K.J.;Kang, J.K.;Cong, Huynh Thanh;Noh, K.C.;Lee, J.T.
    • Transactions of the Korean hydrogen and new energy society
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    • v.18 no.4
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    • pp.374-381
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    • 2007
  • In order to verify the feasibility of expansion of back-fire limit equivalence ratio in the hydrogen-fueled engine with external mixture, the characteristics of performance and combustion are experimentally analyzed with change of intake/exhaust valve timings under the fixed valve overlap period of $0^{\circ}$ CA(non-valve overlap period). These characteristics are also tested for the change of exhaust valve closing timing while intake valve opening timing is fixed to clear the main cause of back-fire occurrence. As the results, the less valve overlap period center is retarded, the more back-fire limit equivalence ratio increases and back-fire does not occurred after TDC. In addition, it was shown that the control of back-fire is dependent on intake valve opening timing than valve overlap period.

Micromorphology of Benthic Diatom Species Achnanthes alteragracillima Lange-Bert

  • Lee, Jung Ho
    • Journal of Plant Biology
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    • v.37 no.4
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    • pp.417-420
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    • 1994
  • Morphology of Achnanthes alteragracillima Lange-Bert. was studied with scanning electron microscopy in epilithic samples from the Kwang River (Kwangchun), Kyungsangbuk-Do, Korea. The species was characterized by the external raphe terminal fissure deflecting up to valve margin, the internal raphe proximal endings slightly deflecting to the opposite direction each other and biased hyaline area at the valve pole. It could be distinguished from A. minutissima K tz., closely related species, in having not straight external raphe terminal fissures, and from A. convergens H.Kob. in having a biased hyaline area at the valve pole and not a convergent striae arrangement at the pole of the raphe valve.

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A Study of Backfire Control in a Hydrogen-Fueled Engine with External Mixture Using Changes of Valve Overlap Period (밸브오버랩기간 변화에 의한 흡기관 분사식 수소기관의 역화억제에 관한 연구)

  • Kang, J.K.;Cong, Huynh Thanh;Noh, K.C.;Lee, J.T.
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.3311-3316
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    • 2007
  • To analyze the influence of valve overlap period on a backfire occurrence, the single cylinder research engine with MCVVT(Mechanical Continuous Variable Valve Timing) system is developed and backfire limit equivalence ratio defined as fuel-air ratio equivalence ratio at which backfire occurs is examined according to various valve overlap period. The MCVVT is the system to control valve overlap period by mechanical device. It is estimated that the lower valve overlap period has the higher backfire limit equivalence ratio though the same energy is supplied. When the valve overlap period is changed from 30$^{circ}$ CA to 0$^{circ}$ CA, backfire limit equivalence ratio is increased 74%, approximately. It means that valve overlap period is concern in backfire occurrence, and may be one of the methods for controlling back fire occurred in a $H_2$ engine.

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A Development and Basic Characteristics of MCVVT Research Hydrogen Engine for Practical Use of External Mixture Hydrogen-Fueled Engine (흡기관 분사식 수소기관의 실용화를 위한 MCVVT 연구용 수소기관의 개발과 기본 특성)

  • Kang, J.K.;Cong, Huynh Thanh;Noh, K.C.;Lee, J.T.;Lee, J.H.
    • Transactions of the Korean hydrogen and new energy society
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    • v.17 no.3
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    • pp.255-262
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    • 2006
  • To develop a hydrogen fueled engine with external mixture which uses in high reliability, low cost and low pressure, the single cylinder research engine with MCVVT(Mechanical Continuous Variable Valve Timing) system is developed and its basic characteristics analyzed. The MCVVT developed has high reliability and the valve timing change is possible in wide range continuously. Though the mechanical loss due to MCVVT system is increased a little, back-fire suppression research for valve overlap period is no difficulty. It's also confirmed that the hydrogen-fueled engine has lower torque and is possible high lean burn. As fuel-air equivalence ratio is high, as thermal efficiency is remarkable increasing.

The Realization of High Performance in a Hydrogen-Fueled Engine with External Mixture by Retarding Valve Timing and Super Charging (밸브 타이밍 지각과 과급에 의한 흡기관 분사식 수소기관의 고성능 실현)

  • Lee, Kwang-Ju;Hur, Sang-Hoon;Lee, Jong-Tae
    • Transactions of the Korean hydrogen and new energy society
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    • v.20 no.6
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    • pp.464-470
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    • 2009
  • In order to analysis the possibility of high expansion and performance without backfire in a hydrogenfueled engine using external mixture injection, combustion characteristics and performance enhancement were analyzed in terms of retarding valve timing and increasing the boosting pressure. As the results, it was found that thermal efficiency increased by retarding intake valve timing with the same level of supplied energy is over 6.6% by the effect of high expansion including effect of combustion enhancement due to supercharging. It was also shown that the achievement of high power (equal to that of a gasoline engine), low brake specific fuel consumption and low emission (NOx of less than 16 ppm) without backfire in a hydrogen-fueled engine is possible around a boosting pressure of 1.5 bar, intake valve opening time of TDC and $\Phi$=0.35 in fuel-air equivalence ratio.

Morphology and distribution of some marine diatoms, family Rhizosoleniaceae, genus Proboscia, Neocalyptrella, Pseudosolenia, Guinardia, and Dactyliosolen in Korean coastal waters

  • Yun, Suk-Min;Lee, Jin-Hwan
    • ALGAE
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    • v.26 no.4
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    • pp.299-315
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    • 2011
  • The morphology, taxonomy, and distribution of species belonging to the diatom family Rhizosoleniaceae were studied from the marine coastal waters of Korea. Rhizosolenid diatom taxa were collected at 30 sites from September 2008 to February 2010 and were analyzed by light and scanning electron microscopy. We identified 6 rhizosolenid genera, including Rhizosolenia, Proboscia, Pseudosolenia, Neocalyptrella, Guinardia, and Dactyliosolen. We describe 5 genera in this study, except Rhizosolenia. Five genera were compared in detail with congeneric species. Six genera within the family Rhizosoleniaceae were divided into two groups based on morphological diagnostic characters including valve shape, areolae pattern, the shape of external process, and girdle segments in the column. The first group had a conoidal valve and loculate areolae, which comprised Rhizosolenia, Proboscia, Pseudosolenia, and Neocalyptrella, and the second group of Guinardia and Dactyliosolen showed a flat or rounded valve and poroid areolae. Important key diagnostic characters were based on valve shape, areolae pattern on the segment, external process, position of the tube, and the valve margin. D. phuketensis was new to Korean coastal waters.

A Study on Safety Engineering & System Optimization in the Closed Piping System (밀폐배관계에 있어서의 열팽창에 대한 안전설계 및 시스템 최적 설정에 관한 고찰)

  • Char, Soon-Chul;Hwang, Soon-Yong;Kang, Kyung-Sik
    • Journal of the Korea Safety Management & Science
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    • v.9 no.1
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    • pp.1-8
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    • 2007
  • To improve the practical application of the thermal expansion of closed long pipeline exposing to external heating sources such as solar energy, safety engineering and system optimization for relief valve in the closed piping system are suggested through theoretical approach, correlation in view of temperature and pressure increase caused by external solar energy in the closed piping system. The profile for thermal relief valve including relieving capacity, influx heat energy, sizing criteria, set pressure, selection against back pressure is also presented. It is noted that following topic on solar relief valve should be applied to engineering, installation and commissioning.

A Study on Engineering Design IT Installation of Thermal Relief Valve in a Chemical Plant (화학플랜트에서의 릴리프밸브 설계에 관한 고찰)

  • Char, Soon-Chul;Hwang, Soon-Yong;Jang, Seo-Il
    • Journal of the Korea Safety Management & Science
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    • v.8 no.4
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    • pp.39-51
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    • 2006
  • Based on the practical process engineering design and commissioning and startup operation experiences focused on chemical process safety, the comprehensive review of engineering design and installation of the thermal relief valve with its surrounding facility in a chemical plant piping system is provided to enhance the better understanding of the piping system of characteristics of thermal relief valve which is comprised of the theoretical approach, correlation in terms of temperature and pressure increase caused by external heat supply in a piping system, consideration of thermal relief valve engineering design, pressure relieving system of serial thermal relief valves and exception of their installation. It is earnestly suggested that following topic should be implemented during thermal relief valve engineering design, installation and normal operation as well.

Valve-Sparing Root Replacement: Aortic Root Remodeling with External Subvalvular Ring Annuloplasty

  • Cho, Sang-Ho;Kim, Dae Hyun;Kwak, Young Tae
    • Journal of Chest Surgery
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    • v.49 no.6
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    • pp.489-492
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    • 2016
  • The original valve-sparing procedures for aortic root aneurysms were remodeling and reimplantation of the aortic root. The remodeling technique provides more physiologic movement of the cusps within 3 reconstructed neo-sinuses, thus preserving root expansibility through the interleaflet triangles. However, the durability of remodeling has been a matter of concern due to the high rate of aortic insufficiency when annular dilation is not addressed. Therefore, a modified approach was developed, combining a physiologic remodeling of the root with a subvalvular annuloplasty. This case report highlights the first case of successful aortic root remodeling with external subvalvular ring annuloplasty in Korea.

Modeling and testing for hydraulic shock regarding a valve-less electro-hydraulic servo steering device for ships

  • Jian, Liao;Lin, He;Rongwu, Xu
    • International Journal of Fluid Machinery and Systems
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    • v.8 no.4
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    • pp.318-326
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    • 2015
  • A valve-less electro-hydraulic servo steering device (short: VSSD) for ships was chosen as a study object, and its mathematic model of hydraulic shock was established on the basis of flow properties and force balance of each component. The influence of system structure parameters, changing rate of motor speed and external load on hydraulic shock strength was simulated by the method of numerical simulation. Experiment was designed to test the hydraulic shock mathematic model of VSSD. Experiment results verified the correctness of the model, and the model provided a correct theoretical method for the calculation and control of hydraulic shock of valve-less electro-hydraulic servo steering device.