• Advances in aircraft and spacecraft science
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• 제5권5호
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• pp.533-550
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• 2018

Detonation transmission between propane/oxygen (donor) and propane/air (acceptor) with an abrupt area change is experimentally studied. In the donor, there are two types of incident detonation waves: A self-sustained Chapman-Jouguet (CJ) detonation wave and an overdriven detonation wave that is a result of the difference in the initial donor pressure ratios. The piston work is used to characterize the strength of the incident detonation wave. For an incident CJ detonation wave, the re-initiation of a detonation wave in the acceptor depends on the initial pressure in the donor and the expansion ratio. The axisymmetric and non-axisymmetric soot patterns respectively correspond to direct detonation and detonation re-initiation. For an incident overdriven detonation wave, the re-initiation of a detonation wave in the acceptor strongly depends on the degree of overdrive.

• 한국수소및신에너지학회논문집
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• 제27권1호
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• pp.114-120
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• 2016

This paper describes generating efficiency characteristics of the double acting Stirling engine/generator for domestic small-scale CHP (Combined Heat and Power) system. In small distributed generation applications, Stirling engine has competition from fuel cell, microturbine and etc. In order to be economical in the applications, a long life with minimum maintenance is generally required. Free piston Stirling engine (FPSE) has no crank and rotating parts to generate lateral forces and require lubrication. Double acting Stirling engine/generator has one displacer and two power piston which are supported by flexure springs. Two power pistons oscillate with symmetric displacement and are connected with moving magnet type linear generators for power generation from PV work. In experiments, 1 kW class double acting free piston Stirling engine/generator is fabricated and tested. Heat is supplied to hot end of engine by the combustion of natural gas and converted to electric power by linear generators which are assembled with power pistons. The electric parameters such as voltage, current and phase are measured with for variable flow rate of fuel gas. Especially, generating efficiency of FPSE is measured with three different measurement methods. Generating efficiency of the double acting Stirling engine/alternator is about 24%.

• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.1019-1029
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• 2006

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of ballistic ranges developed to date, two-stage light gas gun is being employed most extensively. In the present study, a theoretical work has been made to develop a new type of ballistic range which can easily simulate a flying projectile. The present ballistic range consists of high-pressure tube, piston, pump tube, shock tube and launch tube. The effect of adding a shock tube in between the pump tube and launch tube is investigated. This improvement is identified as the reduction in pressures in the high pressure tube and pump tube while maintaining the projectile velocity. Equations of motions of piston and projectile are solved using Runge-Kutta methods. Dependence of projectile velocity on various design factors such as high pressure tube pressure, piston mass, projectile mass, area ratio of pump tube to launch tube and type of driver gas in the pump tube are also analyzed. Effect of various gas combinations is also investigated. Calculations show that projectile velocities of the order 8 km/sec could be achieved with the present ballistic range.

• 자원환경지질
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• 제18권3호
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• pp.239-246
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• 1985

Uranium-thorium separation technique from shallow sediment and ${\alpha}$-source electrodeposition technique are established in the present work, and uranium series disequilibrium dating method is applied to the quaternary piston core from Sangback-do, South Sea of Korean Peninsula. The age of the piston core (depth 200~300cm) sampled from Latitude $34^{\circ}06^{\prime}37^{{\prime}{\prime}}$, Longitude $127^{\circ}37^{\prime}37^{{\prime}{\prime}}$ was determined as ranging from $9.0{\pm}2.2$ to $22.9{\pm}3.3$ Ky B.P, i.e., Later Pleistocene, older than Holocene which was stratigraphically known in the previous study. The sedimentation rate in the area is regularly increased according to the depth of the sedimentation layer. Except a few split sections of the piston core the sedimentation rates are avarage 7.2cm/1,000 years. Where sedimentation layer is deeper, then sedimentation rate tend to be slower. It must be pointed in age calculation that initial $^{230}Th/^{234}U$ radioactivity ratio is much influenced when detrital material was introduced in the sample. The $^{230}Th/^{234}U$ activity ratio measured in the present work is 0.06 at $^{232}Th=0$, and this value shows higher analytical errors because of the low· radioactivity of $^{230}Th$ in the samples.

• Tribology and Lubricants
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• 제1권1호
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• pp.46-58
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• 1985

피스톤링과 실린더벽 사이의 윤활이 왕복운동을 하며 동하중을 받는 포물선형의 슬라이드 베어링의 유체 윤활로 보고 전개하였다. 싸이클 상의 유막 두께의 변화, 윤활유 운반과 마찰력을 계산하는 과정이 개략적으로 설명되었고, 이들 성능 특성들에 대한 링 높이, 링 앞면 곡률반경과 링의 비대칭의 영향을 고찰하였다. 단독링에 대한 해석결과를 조금 더 복잡한 링 팩에 대해 확대 적용하였다. 링의 부하가 되는 링 주위의 압력들은 실험적으로 또는 가스 흐름 해석으로부터 얻을 수 있는데 본 연구에서는 후자를 택하였다. 링팩에서의 유체 연속 및 윤활유 부족에 따른 수치 해석에 주안점을 두었다.

• 에너지공학
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• 제11권2호
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• pp.160-165
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• 2002

LPG 연료를 사용하는 대형 단기통엔진은 연소과정과 배기성능을 파악하기 위해서 설계.제작되었다. 실린더헤드와 피스톤 크라운은 LPG 연소를 위해서 변경되었다. 또한 플라이휠은 단기통엔진의 진동을 최소로 하기 위해서 제작되었다. 실험용 단기통엔진의 실린더내경과 행정은 각각 130mm와 140mm이다. 압축비는 피스톤 크라운 형상을 다르게 하여 8에서 9로 변경되었다. 본 연구를 위해서 제작된 단기통엔진은 1,000rpm에서 운전되었다. 본 연구의 주요 결론은 (1)제작된 엔진의 출력은 3가지 다른 압축비별로 당량비 1.0에서 최고를 나타낸다. (2) 압축비 증가에 따라서 출력이 약간 증간한다. (3) 최적 점화시기는 크랭크각으로 2에서 10까지 압축비의 증가와 함께 지각되어진다.

• 한국소음진동공학회논문집
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• 제27권1호
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• pp.65-71
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• 2017

This work presents a comparative work on the ride comfort of a quarter car suspension system between two different magneto-rheological (MR) dampers; one is conventional type without bypass hole and the other is featured by several bypass holes in the piston. As a first step, two different MR dampers are designed on the basis of the governing equation and manufactured with same geometric dimensions except the bypass holes. After investigating the field-dependent damping properties, two dampers are installed to the quarter car suspension system. The suspension model is then derived and a sky-hook controller is implemented to identify vibration control performance under random road. It is shown that the suspension system with MR damper featured by the bypass holes can provide much better ride quality than the case without the bypass holes. This is validated via experimental implementation.

• 에너지공학
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• 제26권1호
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• pp.9-22
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• 2017

A combined thermal and flow analysis was carried out to study the behavior and performance of a small, commercial LTD (Low-Temperature-Differential) heat engine. Laminar-flow solutions for annulus and channel flows were employed to estimate the viscous drags on the piston and the displacer and the pressure difference across the displacer. Temperature correction factors were introduced to account for the departure from the ideal heat transfer processes. The analysis results indicate that the work required to overcome the viscous drags on engine moving parts and to move the displacer is much smaller than the moving-boundary work produced by the power piston for temperature differentials in the neighborhood of $20^{\circ}C$ and engine speeds below 10 RPS. A comparison with experimental data reveals large degradations from the ideal heat transfer processes. Thus, heat-transfer devices inside the displacer cylinder are recommended.

• 대한기계학회논문집A
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• 제33권6호
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• pp.614-619
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• 2009

An engine for marine propulsion and power generation consists of several cylinder liner-piston sets. And the oil groove is on the cylinder liner inside wall for the lubrication between a piston and cylinder. The machining process of oil groove has been carried by manual work so far, because of the diversity of the shape. Recently, we developed an automatic grinding robot system for oil groove machining of engine cylinder liners. It can covers various types of oil grooves and adjust its position by itself. The grinding robot system consists of a robot, a machining tool head, sensors and a control system. The robot automatically recognizes the cylinder liner's inside configuration by using a laser displacement sensor and a vision sensor after the cylinder liner is placed on a set-up equipment.

• 한국자동차공학회논문집
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• 제9권3호
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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.