• Proceedings of the KAIS Fall Conference
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• 2010.05b
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• pp.1163-1165
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• 2010

가솔린 기관의 체적 효율은 흡기 장치의 효율의 척도로 표현된다. 현재 체적효율은 4행정 가솔린 엔진의 흡기장치의 특성과 공연비 제어를 위한 중요한 파라미터로 사용되고 있다. 체적 효율은 이론적으로 실린더로 흡입 가능한 양에 대한 실제로 실린더로 흡인한 공기량의 비율이다. 체적효율은 엔진회전 속도와 흡기다기관 부압에 따라 결정되는 종속변수이다. 체적 효율은 정상상태와 과도상태와 같은 엔진의 모든 운전조건을 시험하는데 한계와 제약이 매우 크다. 이 논문에서는 선형 알고리즘을 사용하여 체적 효율의 파라미터를 규명하여 선형 다항식 모델을 개발한다. 그리고 실험으로 구한 체적효율 데이터와 다항식 모델을 비교하고 객관적인 타당성을 평가 하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2358-2367
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• 1992

This paper deals with preliminary design conditions for a thermally actuated Vuilleumier refrigerator/heat pump. The previously reported approximate adiabatic analysis which is based on the 8-volume model makes it possible to evaluate exchanged heats per cycle as well as cyclic pressure, temperature and mass variation of each working volume. Calculated results reveal not only there exists an optimum value for the phase angle and the swept volume ratio maximizing a specific thermal output, but also design parameters can be determined independently of each other. Under a given combination of operating temperature levels, the optimum conditions for refrigeration are different from those for heat pumping and the differences between two operating modes become larger with decreasing the dead volume ratio. Both the optimum phase angle and the optimum swept volume ratio are increased asymptotically toward 0.5 pi and 1.0 respectively, as the dead volume ratio approaches to unity. When a VM machine is used for cooling and heating simultaneously, the design parameters should be carefully determined to reach the best performance.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1356-1364
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• 1990

This paper deals with the preliminary design conditions of Stirling Engines based on an adiabatic analysis with regenerator effectiveness. The investigation of thermal regeneration process results that the definition of effectiveness proposed by Urieli et al. is appropriate for the present model. Then, it is applied to the already existing approximate analytic solution for the adiabatic model in order to optimize thermal efficiency as well as work parameter. Results show that thermal efficiency is less sensitive to the variation in design parameters than work. Phase angle for the maximum work is also the most efficient at high values of the effectiveness. Swept volume ratio should be chosen with care. The optimum value of dead volume ratio is at least less than the maximum efficiency condition. The feasible design range in compression ratio lies between the maximum efficiency condition and the structural limit of Stilring Engines, where the higher its value, the better. Changes in the temperature ratio do not alter the design conditions. Working fluids with the specific heat ratio 1.67 are more efficient that those with 1.4.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1197-1205
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• 1988

An analytical method to predict qualitative performance characteristics of the Stirling Engines in the preliminary design stages is investigated. Both the expansion and the compression cylinder are treated as adiabatic and piston motions are approximated as saw-toothed waves. Basic equations which were originally proposed by Finkelstein consist of mass conservation and energy balances for each adiabatic cylinder. The approximation on piston motions and physical conditions make it possible to divide an engine cycle into four fundamental processes. In each process, first, pressure can be expressed as a function of the crank angle by solving a nonlinear first order ordinary differential equation and other thermodynamic variables are determined in turn. Application of the cyclic steady condition to the whole processes can complete a cycle. Also, further analysis results in analytic expressions for cyclic work and heat transfer in terms of the engine parameters and thermodynamic variables at boundary points. The results are expected useful as a quick reference for the engine performances. Finally, the present method can be applied to the other adiabatic analyses on the Stirling Engines with piece wise linear piston motions, if mass variations are predictable.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.1-8
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• 2001

The flow field inside a cylinder of four-valve Sl engine was investigated quantitatively using a three-dimensional Laser Doppler Velocimetry system, to determine how stroke changes affect the flow field. The purpose of this work was to develop quantitative methods which correlate in-cylinder flows to engine performance. For this study, the sane intake manifold, engine head, cylinder, and the piston were used to examine the flow characteristics in different strokes. Quantification of the flow field was done by calculating three major parameters which are believed to adequately characterize in cylinder motion. These quantities were TKE, tumble and swirl ratios. The LDV results reveal that flow patterns are similar, the flow velocities scale with piston speed but another parameters such as TKE, and tumble and swirl numbers are not the same for different stroke systems.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.4
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• pp.423-429
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• 2012

Miller cycle is considered as an effective means to meet the regulation on Tier II and to reduce $CO_2$ emission. For this cycle, the amount of intake air supplied should be enough increased. Therefore, the intake system with minimized resistance for air flow is under consideration. In this study, the flow coefficients of intake valves were measured in order to obtain the basic data for the cycle simulation and intake port design. The flow coefficients were measured using the steady-flow test rig. As a test result for the poppet valve used the marine engine with medium speed, the flow coefficients are increased to about 0.62 with the valve lift. In addition it is confirmed that the flow coefficients have the characteristic value irrelevant to the S/B ratio.

• Journal of the korean Society of Automotive Engineers
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• v.8 no.1
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• pp.22-28
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• 1986

기관의 성능에 영향을 주는 인자로서는 외적인자(outside factor), 작동인자(operating factor) 및 설계인자(design factor)의 3가지로 나눌 수 있다. 작동인자로서는 기관회전수, 공기연료비, 점화 시기 또는 분사시기 등이면 설계인자로서는 행정체적, 압축비, 흡배기계통의 구조 및 치수, 냉각 방식 등으로 기관에 따라 고유한 값을 가지는 인자이다. 그러나 외적인자인 대기조건 즉 대기 압력, 대기온도 및 대기습도는 계절, 지역 및 기상조건에 따라 달라지므로 이것에 따라 기관이 흡입하는 공기의 압력, 온도 및 습도는 변화하게 된다. 그러므로 대기조건의 변화에 따라서는 기관작동인자인 공기연료비에도 영향을 미치게 할 것이고 또한 연소상태의 변화로 유효압축비 에도 영향을 미치게 할 것이므로 대기상태의 변화는 곧 바로 기관 출력의 변화를 초래하게 될 것이다. 그러므로 같은 운전조건에서의 기관출력도 대기상태의 변화에 따라 변화하게 되므로 임의의 대기 상태에서 측정한 기관출력을 표준대기상태의 기관출력으로 환산해서 평가할 필요가 생긴다. 이것을 일반으로 출력수정(output correction)이라 하고 있으며 각 나라마다 공업규격 또는 기타규격으로 출력정식을 제정하고 있다. 예를 들면 K.S.B 9102, SAE J816B, B.S. 765, DIN 70020, JIS B 8013등이다. 이들 출력수정식들은 많은 문제점을 가지고 있으므로 종래의 출 력수정식으로 출력수정을 하여도 정확하게 맞지 않은 경우가 많다. 출력수정에 관한 문제는 수 10년전부터 많은 연구자에 의하여 연구되고 거론되어 왔으나 과거의 연구자들이 제안하고 거론 되어 왔으나 과거의 연구자들이 제안하고 있는 출력수정식, 또는 규격으로 정하고 있는 출력수 정방법은 어느 것이나 실용상 만족스러운 것이 아직 없다. 그러므로 본 자료는 스파아크 점화 기관의 흡기습도에 관한 출력수정의 문제를 실험적으로 수행한 실험적 출력수정방법에 의한 것과 종래의 출력수정방법에 의한 것과를 비교 검토하였다.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.171-176
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• 2008

As one way of design optimization of two-stage two-cylinder rotary compressor used for R410A heat pump application, displacement volume ratio, being defined by the ratio of the second stage cylinder volume to that of the first stage, has been varied and its effect on the compressor performance has been investigated by a computer simulation program. For simplicity, only the cylinder height of the second stage was varied to change the volume ratio. With increasing the volume ratio in the range of VR=$0.55{\sim}0.9$, volumetric efficiency increased monotonically, but adiabatic efficiency showed a maximum at around VR=0.6. Mechanical efficiency was little influenced by the volumetric ratio. As a consequence, maximum improvement of the compressor performance was found at around VR=0.7. Compared to a one-stage two-cylinder rotary compressor with about the same cooling capacity, COP improvement was about 6.96%.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.953-960
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• 2019

The Miller cycle is a diesel engine that has been developed in recent years that it can reduce NOx and improve fuel consumption by reducing the compression ratio through intake valve closing (IVC) time control. The Miller cycle can be divided into the early Miller method of closing the intake valve before the bottom dead center (BDC) and the late Miller method of closing the intake valve after the BDC. At low speeds, the late Miller method is advantageous as it can increase the volumetric efficiency; while at medium and high speeds, the early Miller method is advantageous because of the high internal temperature reduction effect due to the expansion of the intake air during the piston lowering from IVC to BDC. Therefore, in consideration of the ef ects of the early and late Miller methods, it is necessary to adopt the most suitable Miller method for the operating conditions. In this study, a two-stage turbo charge system was applied to four-stroke engines and the process of enhancing the Miller effect through a reduction of the intake and exhaust valve overlap as well as the valve change adjustment mechanism were considered. As a result, the ef ects of fuel consumption and Tmax reduction were confirmed by adopting the Miller cycle with a two-stage supercharge, a reduction of valve overlap, and an increase of suction valve lift.