• Journal of Advanced Marine Engineering and Technology
• /
• 제26권6호
• /
• pp.646-652
• /
• 2002

The influence of reciprocating frequency and radius on heat transfer in the roughened rectangular channel is experimentally investigated. The aspect ratio (width/height) of the duct is 2.33 and the rib height is one fifteenth of the duct height. And the ratio of rib-to-rib distance to rib height is 10. The discrete ribs were periodically attached to the button wall of the duct with a parallel orientation. The parametric test matrix involves Reynolds number, reciprocating, and reciprocating radius, in the ranges, 1,000∼6,000, 1.7∼2.5 HB and 7∼15cm, respectively. The combined effects of reciprocating frequency and reciprocating radius have considerable influence on the heat transfer due to the modified vortex flow structure.

• Journal of Advanced Marine Engineering and Technology
• /
• 제27권5호
• /
• pp.600-608
• /
• 2003

This Paper describes a detailed experimental investigation of heat transfer in a reciprocating smooth rectangular duct having only the bottom wall heated with reference to the design of a piston for a marine propulsive diesel engine The Parametric test matrix involves Reynolds number and reciprocating radius, respectively, in the range of 1.280∼4.100, and 7∼15 cm with five different reciprocating frequency tested. namely. 1.7, 2.2, and 2.6 Hz. The effects of three different hemi-triangular wavy type tapers on the heat transfer in the reciprocating rectangular channel using the air as a working fluid were check out. The present work confirms that the Nusselt number in the channel with the triangular wavy type taper is lower than without the triangular wavy type taper.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
• /
• pp.521-526
• /
• 2004

This paper introduces works performed for reducing high frequency noise of a reciprocating compressor. Noise in a high frequency range strongly affects sound quality as well as increases total noise level of the compressor. In order to reduce the noise, two different works were carried out. the first work was to measure the vibration Power transferred through suspension spring and discharge pipe; and the second one was to obtain operational deflection shape from cross-power spectrum measured on shell. Based on the information, Adequate structural modification of the transfer path and shell resulted in noise reduction in a high frequency range.

• 설비공학논문집
• /
• 제15권6호
• /
• pp.502-509
• /
• 2003

This paper describes a detailed experimental investigation of heat transfer in a reciprocating rectangular channel fitted with rib structures with particular reference to the design of a piston for marine propulsive diesel engine. The parametric test matrix involves Reynolds number, reciprocating frequency, and reciprocating radius, respectively in the ranges, 1,000～6,000, 1.7～2.5 Hz, and 7～15 cm with four different rib arrangements. The rib arrangements have considerable influences on the heat transfer in the reciprocating channel due to the modified vortex flow structure. The experimental data confirm that the increases in the heat transfer can be seen in order of Case (b), Case (c), Case (d), and Case (a).

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2002년도 학술대회지
• /
• pp.333-336
• /
• 2002

This paper describes a detailed experimental Investigation of heat transfer In a reciprocating rectangular channel fitted with rib structures with particular reference to the design of a piston for marine propulsive diesel engine. The parametric test matrix involves Reynolds number, reciprocating frequency, and reciprocating radius, respectively, in the ranges, $1,000\;{\~}\;6,000,\;1.7\;{\~}\;2.5\;Hz,\;and\;7\;{\~}\;15cm$ with four different rib arrangements. The rib arrangements have considerable influences on the heat transfer in the reciprocating channel due to the modified vortex flow structure. The experimental data confirm that the increases in the heat transfer can be seen in order of Case (a), Case (d), Case (c), and Case (b)

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제48권5호
• /
• pp.241-248
• /
• 1999

Recently, many linear motion generators and motors are rapidly finding applications that ranges from short stroke linear motion vibrators, such as dynamic cone type loudspeakers to stirling engine driven linear reciprocating alternators, compressors, textile machines etc. The stroke-length may go up to 2m, and the maximum speed is in the range of 5 to 10m/s with oscillating frequency as high as 15 kHz. Therefore, the linear oscillating actuators(LOAs) may be considered as variable speed drivers of precise controller with stoke-length and reversal periods during the reciprocating motion. In this paper, the design, fabrication, experiments, and extraction of control parameters of a moving coil type LOA for driving of linear reciprocating motion control systems, are treated. The actuator consists of the NdFeB permanent magnets with high specific energy as the stator produced magnetic field, a coil-wrapped nonmagnetic hollow rectangular bobbin structure, and an iron core as a pathway for magnetic flux. Actually, the design is accomplished by using FEM analysis for the basic configuration of a magnetic circuit, and characteristic equations for coil design. In order to apply as the drivers of a linear motion reciprocating control system, the control parameters and circuit parameters, such as input voltage-stoke, exciting frequency-stoke, coil inductance and so on, are extracted from the analysis and experiments on concerning a fabricating LOA.

• 한국소음진동공학회논문집
• /
• 제13권5호
• /
• pp.348-356
• /
• 2003

Active vibration control algorithms for the compensator and proto-type testing system have been developed for the suppression of vibrations from the reciprocating engines. At first, the developed algorithm determines optimal control vibration phases by detecting vibration responses of the engine without and with compensator, and then performs the continuous optimal control functions by tracking the change of the vibration frequency and phase. This algorithm is comparatively simple. robust for the external excitations and needless of supplementary operation since the control process is serially carried out. To validate the performance of compensator and algorithm, testing system including excitation device are constructed and tested, and the reductions of vibration levels are observed over than 80 % of the uncontrolled levels at various frequency ranges.

• Tribology and Lubricants
• /
• 제29권2호
• /
• pp.105-110
• /
• 2013

Refrigeration and air-conditioning compressors used in home appliances, including refrigerators and air conditioners, are typically hermetic-type reciprocating compressors. Because the shell is sealed by welding, it should be designed to have a semi-permanent life. The energy consumption of a hermetic-type reciprocating compressor is low, but because it operates continuously to maintain a constant temperature inside the refrigerator, it has a certain base load. In this type of compressor, the driving motor operates at a high speed (about 3,000 - 3,600 rpm), which causes valve damage, friction, wear, and high-frequency noise. Many studies have been conducted to solve these problems. To enhance the reliability and efficiency of the reciprocating compressor, the design conditions and operating environment of journal bearings should be considered. Dynamic behavior analysis should be carried out in terms of the discharge pressure. The results showed that the load (discharge pressure) increases in the forward lookup zone and decreases in the backward lookup zone. When the revolution speed is increased, the maximum load decreases in the region where the maximum load operates.

• 설비공학논문집
• /
• 제9권1호
• /
• pp.33-42
• /
• 1997

The reciprocating compressors are widely used in industrial fields for its simplicity in principle and high efficiency. But the design of it requires rigorous experiments due to its high dependence on many design parameters. In this work, a mathematical model is developed so that we can analyze the gas-solid interaction during the whole working processes of a reciprocating compressor. The governing equations, which represent the fluid-solid interaction, was derived from the unsteady Bernoulli's equation with the assumption of quasi-steady working process. The valve itself was assumed to be a one degree of freedom spring-mass-damper system. A simple thermodynamic relation, the ideal gas state equation, was used to give it an external force term assuming that the refrigerant behaves like an ideal gas. It was suggested to use a motor of higher driving frequency to enhance the performance of the reciprocating compressor without causing a faster failure of the valve.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 추계학술대회논문집
• /
• pp.431-434
• /
• 2005

Generally, noise in a reciprocating compressor is attributed to the driving force of a pump. However, close examination shows that the noise heard by customers finally results from radiation of a shell in a compressor, the noise caused by both transmission through a shell and resonance with the natural frequency of a shell. Therefore, the peak frequencies contributing to the overall level of a compressor' noise are closely concerned with vibration of a shell. That's why radiated noise by vibration can be reduced by changing the mode of a shell and by shifting the peak frequencies to other ranges, which are not globally related with the overall noise level. In this paper, the main peak frequencies are analyzed to reduce the radiated noise of a shell, and the vibration characteristics of a shell are examined through Frequency Response Function and Finite Element Analysis. Moreover, the Operational Deflection Shape for a shell is measured with consideration of real driving force of a pump. Finally, the optimum position on a shell, closely related to the main peak frequencies, is found, and the overall noise level caused by radiated noise of a shell is noticeably reduced by mass or stiffness modification of the position.