• Title/Summary/Keyword: Cycle ratio

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A Chancteristic of Thermal Efficiency in Order to High Expansion Realization with a Retard of Intake Valve Closing Time in the Low Speed Diesel Engine (저속 디젤기관에서 흡기밸브 닫힘시기 지연시 고팽창 실현을 위한 열효율 특성)

  • Jang Tae-Ik
    • Journal of Advanced Marine Engineering and Technology
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    • v.30 no.1
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    • pp.42-49
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    • 2006
  • In this research. the diesel cycle was thermodynamically interpreted to evaluate the possibility of high efficiency by converting diesel engines to the high expansion diesel cycle, and general cycle features were analyzed after comparing these two cycles. Based on these analyses. an experimental single cylinder a long stroke with high expansion-diesel engine. of which S/B ratio was more than 3, was manufactured. After evaluating the base engine through basic experiments, a diesel engine was converted into the high expansion diesel engine by establish VCR device and VVT system Accordingly, the high expansion diesel cycle can be implemented when the quantity of intake air is compensated by supercharge and the effective compression ratio is maintained at its initial level through the reduction of the clearance volume. In this case, heat efficiency increased by $5.0\%$ at the same expansion-compression ratio when the apparent compression ratio was 20 and the fuel cut off ratio was 2. As explained above, when the atkinson cycle was used for diesel cycle, heat efficiency was improved. In order to realize high expansion through retarding the intake value closing time, the engine needs to be equipped with variable valve timing equipment, variable compression ratio equipment and supercharged pressure equipment. Then a high expansion diesel cycle engine is realized.

A Thermodynamic Analysis on the Performance with turning Diesel Cycle into Diesel-Atkinson Cycle (디젤기관의 아트킨슨 사이클화에 따른 제반성능의 열역학적 해석)

  • 노기철;정양주;이종태
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.5
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    • pp.1-11
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    • 2004
  • In order to recognize thermal efficiency and power improvement in case that diesel cycle is turned into diesel-atkinson cycle, the fuel-air diesel-atkinson cycle considered gas exchange process is analyzed non-dimensionally and thermodynamically. As a result, in case of diesel-atkinson cycle, as expansion ratio is increased, thermal efficiency and mean effective pressure is increased and it has maximum value at Rec=1. When diesel cycle is turned into diesel-atkinson cycle by late intake valve closing timing, thermal efficiency and power is decreased because of the decline of effective compression ratio and intake airflow, but it could be compensated by increase of compression ratio or super-charged. In case compression ratio is compensated, Rec appears 1 around 100$^{\circ}$ ABDC, and it is expected that thermal efficiency is enhanced by 14.3% compared with conventional diesel cycle. In case compression ratio and intake airflow are compensated simultaneously, super-charged pressure is demanded 2.06bar at Rec=1 and it is more efficient when only compression ratio is compensated in the view point of thermal efficiency.

An Assessment of Urban Water Cycle in Changwon-si Using GIS-based Water Cycle Area Ratio (GIS 기반의 물순환 면적률을 활용한 창원시 도심지역의 물순환성 평가)

  • Song, Bonggeun;Park, Kyunghun;Lee, Taeksoon
    • Journal of Environmental Impact Assessment
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    • v.22 no.5
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    • pp.397-408
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    • 2013
  • The purpose of this study is to analyze water cycle area ratio and spatial evaluation of water cycle in urban area of Changwon-si, Gyeongsangnam-do. Water cycle area ratio are analyzed by using spatial data of land-cover and land-use, and Hot spot analysis of GIS program was used for spatial evaluation of water cycle. The results are as below. Firstly, the high water cycle area ratio areas were forests, parks, and rivers, but urban areas covered asphalt and concrete were low under 40%. Public institutions and co-residential of urban areas were higher than others because of high area ratio of pervious land-cover. Spatial evaluation of water cycle was analyzed to vulnerable areas there are dense residential and commercial area. These areas are really occurring frequently flooding and immersion, therefore, is required water management facilities and improvement of land-cover from impervious to pervious. In the future, it will require additionally analysis of water cycle area ratio supplemented data of water management facility and ground water.

trends in Techical a development of Miller Cycle for Gasdline Engine (저압축 고팽창 기관의 기술과 개발동향)

  • 정찬문
    • Journal of the Korean Professional Engineers Association
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    • v.34 no.2
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    • pp.31-36
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    • 2001
  • The Otto Cycle of conventional gasoline engine has no difference between compression ratio and expension ratio. because of the same length of 4 strokes : Intake, compression, expension, exhaust. On the other hand, miller cycle engine achieves both low-compression ratio and high-compression ratio by shortening the length of compression stroke among 4 strokes. Therefore miller cycle engine is essential for lessening knocking and improving heat efficiency. This paper Is designed to discribe not only principle and the development trend of miller cycle engine but also the control system and the technical characteristics of it.

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A Study on the Composition of Atkinson Cycle and Thermodynamically Analysis for a Diesel Engine (디젤기관에 대한 앳킨슨사이클 구성과 사이클의 열역학적 해석에 관한 연구)

  • Kim Chul Soo;Jung Young Guan;Jang Tae lk
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.2
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    • pp.185-193
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    • 2005
  • The present study composed a diesel-atkinson cycle of high expansion as a method of achieving high efficiency in diesel cycle engines. It also interpreted the cycle engine thermodynamically analysis to determine the possibility of the improvement of thermal efficiency and clarified the characteristics of several factors . According to the result of theoretical analysis, heat efficiency was highest when expansion-compression ratio Reど:1. In addition. diesel engines with high apparent compression ratio had higher expansion-compression ratio than otto engines and consequently their effect of high expansion was high. which in turn enhanced thermal efficiency. When the atkinson cycle was implemented in a real diesel engine by applying the miller cycle through the variation of the closing time of the intake valve, the effective compression ratio and the quantify of intake air decreased and as a result, the effect of high expansion was not observed. Accordingly. the atkinson cycle can be implemented when the quantity of intake air is compensated by supercharge and the effective compression ratio is maintained at its initial level through the reduction of the clearance volume. In this case. heat efficiency increased by $4.1\%$ at the same expansion-compression ratio when the apparent compression ratio was 20 and the fuel cut off ratio was 2. As explained above, when the atkinson cycle was used for diesel cycle. heat efficiency was improved. In order to realize high expansion through retarding the intake value closing time, the engine needs to be equipped with variable valve timing equipment, variable compression ratio equipment and supercharged Pressure equipment. Then a diesel-atkinson cycle engine is realized.

A Study on the Theory Analysis and Engine Test Performance by a High Expansion Diesel Engine into Intake-Exhaust Consideration (흡.배기를 고려한 고팽창 저속 디젤 기관의 이론 해석과 기관 성능에 대한 연구)

  • Jang, Tae-Ik
    • Journal of Advanced Marine Engineering and Technology
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    • v.32 no.8
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    • pp.1141-1148
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    • 2008
  • One of the methods to increase the efficiency of an engine is to expand pressures obtained from combustions equal to the pressure of atmosphere as much as possible and then convert thermal energy into mechanical energy also as much as possible. In this research, the Diesel cycle was thermodynamically interpreted to evaluate the possibility of high efficiency by converting Diesel engines to the Atkinson cycle, and general cycle features were analyzed after comparing these two cycles. In the case of fuel air the Diesel-Atkinson cycle considering intake and exhaust similar to real cycles, the value of thermal efficiency and average effective pressure increased, though their values were smaller than those of standard air amount cycle, when expansion compression ratio increased. When normal Diesel engines of which compression stroke and expansion stroke are all the same, was converted to the Atkinson cycle by changing the time of intake value close, combustion pressure reduced due to reduced expansion compression ratio and intake air amount due to decreased effective cycle volume.

A Basic Analysis of Performance of Turbo CI Engine based on Stirling Cycle (스털링 사이클을 기본으로 하는 과급 CI 엔진의 기초 성능 분석)

  • 배종욱
    • Journal of Advanced Marine Engineering and Technology
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    • v.24 no.5
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    • pp.76-85
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    • 2000
  • Stirling cycle was actualized as so called ‘hot air engine’. It has been focused again lately as one of measures for exhaust gas emission problem, but as small power engine because of its method of heat addition. Recently marine power plants commenced to meet a stringent environmental restrictions by international convention, Marpol so that diesel engines as main and auxiliarly power plants are urged to be reformed to reduce NOx emission. Author devised a compression ignition engine as a large marine power plants combined with turbo charger based on stirling cycle, and analyzed the performance by means of basic thermodynamic calculation. Analyzed in this paper, were theoretical efficiency, mean effective pressure, required equivalence ratio, gas turbine power ratio, maximum pressure, states of turbo-charger inlet gas and exhaust gas, manifesting that the engine could be proposed as one of the future power plants of marine use.

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Increase of treatment amount of thermophilic oxic process considering calorie/water (C/W) ratio (칼로리/수분 (C/W)비를 고려한 고온호기 처리법에서의 처리량 증가)

  • Jeon, Kyoung-Ho;Choi, Dong-Yoon;Song, Jun-Ik;Park, Kyu-Hyun;Kwag, Jung-Hoon;Kim, Jae-Hwan;Kang, Hee-Sul
    • Journal of Korean Society of Water and Wastewater
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    • v.24 no.2
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    • pp.203-210
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    • 2010
  • The signification of calorie/water (C/W) ratio was investigated in the treatment of highly concentrated organic wastes by thermophilic oxic process (TOP). Swine waste was used in this study. When C/W ratio was 1.6, most of swine waste was decomposed and all water was evaporated in the 24-h injection cycle. To improve treatment efficiency of TOP treating swine waste, the effect of shortening the swine waste injection cycle was examined. The shortening of injection cycle was conducted to stimulate the activity of thermophilic bacteria. A high temperature in the reactor was maintained by shortening of the injection cycle. When the swine waste injection cycle was shortened, the C/W ratio was fixed at 1.6. As a result, by shortening the swine waste injection cycle from 24-h to 12 and 6-h, the maximum loading rate of swine waste per day could be improved 1.9 and 3.5 times, respectively.

An Analysis on the Characteristics of the Hydrologic Cycle along Gyeongui Line Forest Park through time series analysis of Biotope Area Ratio and permeable ratio (생태면적률과 투수포장 비율의 시계열 분석을 통한 경의선숲길의 물 순환체계 특성 분석)

  • Kim, Mi-Hu;Oh, Choong-Hyeon
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.23 no.3
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    • pp.105-119
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    • 2020
  • The purpose of this study is to analyze the hydrologic cycle environment of Gyeongui Line Forest Park, a linear city park, in order to improve hydrologic cycle systems in urban areas. The method of the study is the Biotope Area Ratio and the Permeable ratio survey. The study subject is the Gyeongui Line Forest Park, created in 2016 as a linear park in Seoul. The results showed that the Biotope Area Ratio improved by 31.2% (31,927㎡) from 35.7% (36,480㎡) in 2000 to 66.9% (68,407㎡) in 2019 on a site area of 102,117㎡. Next, the Permeable ratio improved by 43.8% from 29.0% to 72.8%, and the impermeable ratio decreased by 43.8% from 71.0% to 27.2%. The Biotope Area Ratio exceeded the target ratio of 60% by 6.9%, set by the Ministry of Environment. The ratio of green space exceeded the target ratio of 60%, by 4.0%. And so they contributed to the improvement of the hydrologic cycle by the creation of the Gyeongui Line Forest Park. Urban parks need to exceed the Biotope Area Ratio and the green area ratio of the legal standards, especially when creating large parks of over 100,000 square meters, in the era of climate change. It is necessary to continuously plant trees in the space where trees can be planted, and to contribute to the improvement of the hydrologic cycle system and urban heat island effect by conducting three-dimensional.

A Composition and Basis Experiment of Single Cylinder Low Speed Diesel Engine for Atkinson Cycle Materialization (앳킨슨사이클 실현을 위한 단기통 저속 디젤기관의 구성과 기초 실험)

  • Jang, Jtaeik
    • Transactions of the Korean hydrogen and new energy society
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    • v.24 no.5
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    • pp.461-466
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    • 2013
  • In this research, the diesel cycle was thermodynamically interpreted to evaluate the possibility of high efficiency by converting diesel engine to the atkinson cycle, and general cycle features were analyzed after comparing these two cycles. That an experimental single cylinder and a long stroke diesel-atkinson engine, of which S/B ratio was more than 3, were manufactured. After evaluating the engine through basic experiments, a diesel engine was converted into the atkinson cycle by constituent VCR (variable compression ratio) device and VVT (variable valve timing) system. The experimental method was to observe compression work reduction effects due to low compression effects from delayed intake valve closing of the early stage atkinson engine. The result, the possibility of increasing compression ratio about each engine load was confirmation by constructing compensate expansion-compression ratio in accordance with the delayed intake valve close.