• 한국생산제조학회지
• /
• 제19권3호
• /
• pp.321-325
• /
• 2010

This study analyzes the results with the simulation of heat transfer, structural stress, fatigue and vibration on main parts of engine. The maximum temperature is shown by $300.73^{\circ}C$ on the upper part of piston with the heat transfer. Maximum total deformation or equivalent stress is shown by 65.31mm or 21364MPa respectively at the upper plane of piston with the structural analysis inclusive of heat transfer. The minimum life is shown by the cycle less than $10^7$ at the part of crankshaft with the fatigue analysis. The frequency with the maximum amplitude of deformation is shown by 14Hz. Maximum total deformation or equivalent stress is shown respectively by 93.99mm on the upper plane of piston or 42625MPa at the part connected with crack shaft and connecting rod at 14Hz. The durability of engine design can be verified by using the analysed result of this study.

• International Journal of Automotive Technology
• /
• 제8권5호
• /
• pp.615-622
• /
• 2007

In this study, a Coupled Computational Fluid Dynamics(CFD) and Finite Element Analysis(FEA) method are used to predict and evaluate the performance of an automotive shock absorber. Averaged Navier-Stokes equations are solved by the SIMPLE method and the RNG $k-\varepsilon$ is used to model turbulence. CFD analysis is carried out for different intake valve deflections and piston velocities. The force exerted on the valve in each valve deflection is obtained. The valve deflection-force relationship is investigated by the FEA method. The force exerted on the valve in each piston velocity is obtained with a combination of CFD and FEA results. Numerical results are compared with the experimental data and have shown agreement. Dependence of valve deflection as a function of piston velocity is investigated. Effects of hydraulic oil temperature change on valve behavior are also studied.

• 한국자동차공학회논문집
• /
• 제1권2호
• /
• pp.89-102
• /
• 1993

In this experimental investigation, various plasma-sprayed zirconia contained coatings and a kind of alumina-zirconia coating were studied to gain a better understanding of their tribological behaviour under dry contact condition in a reciprocating motion at temperature of 200℃. Particular attention was made for finding appropriate coatings in cylinder liner/piston ring application with an emphasis on the antiwear property. In order to identify the wear mechanism, SEM(Scanning Electron Microscope), optical micrograph, and roughness tester were used. Alumina-zirconia and 8% yttria-zirconia were found to be most appropriate for the application to the cylinder liner/piston ring and, especially, alumina-zirconia exhibited highest wear-resistance and also showed good friction characteristics. Wear mechanisms of ceramic coatings identified.

• 대한기계학회논문집B
• /
• 제20권1호
• /
• pp.275-283
• /
• 1996

The turbulence in the engine cylinder is generated by intake pressure and inertia effects during intake stroke, and is generated and decreased by piston compression effect during the compression stroke. The classified needed to generate high turbulence flow at vicinity of ignition timing. Therefore, A single-shot Rapid Intake Compression Expansion Machine (RICEM), which is able to realize the intake, compression, expansion or intake-compression stroke under high piston speed respectively, was manufactured and evaluated in order to find methods to generate high turbulence at around spark timing. It was found that the characteristics of RICEM such as reapperance, leakage, piston displacement with crank angle was corresponding to those of real engine and RICEM simulates not only high temperature and high pressure field but also flow patterns of the actual engine by increasing of pressure in intake line.

• 동력기계공학회지
• /
• 제17권2호
• /
• pp.21-28
• /
• 2013

Phenomenon of droplet impingement with high temperature wall needs to be investigated because atomization process of droplet and cooling process of the wall by the impingement are very important in industry, thus studies concerned with temperature of piston wall have been conducted in spray characteristics analysis of diesel engine. Hence, in this study, we defined $DT_{sat}(=T_w-T_{sat})$ superheat degree of the wall by difference between $T_w$ considering surface temperature of piston in the actual engine and $T_{sat}$ saturation temperature of the fuel and then investigated spray behavior of wall impinging with variance of the boiling process. In this study, in order to analyze wall impingement of droplet in accordance with difference of boiling condition, calculational conditions were set as $DT_{sat}=40K$(nucleate boiling), $DT_{sat}=140K$(transition boiling), and $DT_{sat}=240K$(film boiling). As a result, it can be found that fuel vapor increases and droplet mass decreases in the order of the nucleate boiling, transition boiling, and film boiling.

• 한국유체기계학회 논문집
• /
• 제18권1호
• /
• pp.37-43
• /
• 2015

A Beta-type Stirling engine is developed and tested on the operation stability and cycle performance. The flow rate for cooling water ranges from 300 to 1500 ml/min, while the temperature of heat source changes from 300 to $500^{\circ}C$. The internal pressure, working temperatures, and operation speed are measured and the engine performance is estimated from them. In the experiment, the rise in the temperature of heat source reduces internal pressure but increases operation speed, and overall, enhances the power output. The faster coolant flow rate contributes to the high temperature limit for stable operation, the cycle efficiency due to the alleviated thermal expansion of power piston, and the heat input to the engine, respectively. The experimental Stirling engine showed the maximum power output of 12.1 W and the cycle efficiency of 3.0 % when the cooling flow is 900 ml/min and the heat source temperature is $500^{\circ}C$.

• 에너지공학
• /
• 제26권1호
• /
• pp.9-22
• /
• 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.

• 전력전자학회논문지
• /
• 제19권5호
• /
• pp.457-462
• /
• 2014

Given their low cost, single rolling piston compressors (SRPC) are utilized in low-power room air-conditioning systems. The SRPC cycle is composed of one compression and discharge process per mechanical rotation. The load torque is high during the compression process of the refrigerants and low during the discharge process of the refrigerants. This load torque variation induces a speed ripple and severe vibration, which cause fatigue failures in the pipes and compressor parts, particularly under low-speed conditions. To reduce the vibration, the compressor usually operates at a high-speed range, where the rotor and piston inertia reduce the vibration. At a low speed, a predefined feed-forward load torque compensator is used to minimize the speed ripple and vibration. However, given that the load torque varies with temperature, pressure, and speed, a predefined load torque table based on one operating condition is not appropriate. This study proposes an online load torque compensator for SRPC. The proposed method utilizes the speed ripple as a load torque ripple factor. The speed ripple is transformed into a frequency domain and compensates each frequency harmonic term in an independent feed-forward manner. Experimental results are presented to verify the proposed method.

• Journal of Advanced Marine Engineering and Technology
• /
• 제24권5호
• /
• pp.69-75
• /
• 2000

Investigators who study on combustion in the cylinders of reciprocating piston type internal combustion engines have been encountered embarrassments due to the difficulties of adjusting specific parameter without interfacing other parameters such as cylinder wall temperature, composition of gas in the cylinder, existence of cylinder lubricant etc. Rapid compression expansion machine, the position and speed of piston of which are able to be controlled by means of a system controlled electrically, and actuated hydraulically could be utilized as one of the most preferable countermeasures against those difficulties. Several units of rapid compression expansion machines were developed but the speed up of frequency of piston movement still is the problem to be improved to copy with actual speed of internal combustion engines. Authors designed and manufactured a new rapid compression-expansion machine electrically controlled, hydraulically actuated, and computer programed and then examined the performance of one. Results of a set of experiments revealed acquirements of certain improvement on frequency of piston movement preserving the stability of system response and reproducing accurate compression ratio of cylinder, those are the key function for the in-cylinder combustion experiments on internal combustion engines.

• 한국연소학회지
• /
• 제20권4호
• /
• pp.26-33
• /
• 2015

American NREL (National Renewable Energy Laboratory) reported that BD20 could reduce PM, CO, SOx and cancerogenic matters by 13.6%, 9.3%, 17.6% and 13% respectively, compared to diesel fuel. BD20 has been being tested on garbage trucks and official vehicles at Seoul City, which is positive on air environment, but negative on combustion by higher viscosity in winter season. This study investigated the combustion characteristics by employing multi cavity piston for improving the deterioration of combustibility caused by the higher viscosity of the biodiesel fuel such as BD20 with the combustion flames taken by a high speed camera and the cylinder pressure diagram. A 4-cycle single cylinder diesel engine was remodeled to a visible 2-cycle engine for taking the flame photographs, which has a common-rail injection system. The test was done at laboratory temperature of about $4{\sim}5^{\circ}C$.