• Journal of the Korean Society for Precision Engineering
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• v.19 no.6
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• pp.35-42
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• 2002

Verification of tool collision Is an important issue in die and mold machining. In this paper three functions of verification for 3-axis milling machining are schematically explained. Operators of geometric models are explained at first, which will be used in the functions of verification. The first verification function is getting a collision-free region when a tool assembly and a part surface model are given. The second function estimates the shortest length of cutter shank with that the tool cuts all of a region without collision The last one is cutting simulation considering all parts of tool assembly as well as cutter blade. Proposed approaches can be easily implemented by using several basic operators of geometric model. An example to calculate collision-free region is presented also.

• International Journal of Fluid Machinery and Systems
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• v.4 no.2
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• pp.243-254
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• 2011

In the present paper, we focus on the flow computation of a low head Propeller turbine at a wide range of design and off-design operating conditions. First, we will present the results on the efficiency hill chart prediction of the Propeller turbine and discuss the consequences of using non-homologous blade geometries for the CFD simulation. The flow characteristics of the entire turbine will be also investigated and compared with experimental data at different measurement planes. Two operating conditions are selected, the first one at the best efficiency point and the second one at part load condition. At the same time, for the same selected operating points, the numerical results for the entire turbine simulation will be compared with flow simulation with our standard stage calculation approach which includes only guide vane, runner and draft tube geometries.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.205-208
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• 2006

This paper proposes a new computational aeroacoustics method for an axial fan analysis. The major aeroacoustic noise source of an outdoor air-conditioner is the axial fan. It was revealed that the dominant noise source is the aerodynamic interactions between the rotating blade and stationary orifice. Many researches were focused on the fan only case. However, it does not fit to a real outdoor unit of air-conditioner. Especially, the inlet part of the axial fan of real system case is complex and not uniform. So, in order to identify the dominant noise source of axial fan, full outdoor unit analysis is important. Transient CFD analysis of full system was performed by commercial CFD code - SC/Tetra. Dominant noise source of the system was calculated by commercial CFN code - FlowNoise. The results show that not only BPF peaks but also broadband noise are similar to the measured data.

• International Journal of Fluid Machinery and Systems
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• v.1 no.1
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• pp.38-46
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• 2008

Studies on cavitation instabilities of hydrofoils and cascades are reviewed to obtain fundamental understandings of the instabilities observed in turbopump inducers. Most of them are based on the stability analysis of two-dimensional inviscid cavitating flow. The most important finding of the analysis is that the cavitation instabilities depend only on the mean cavity length. For a hydrofoil, the characteristic length is the chord length and partial/transitional cavity oscillation occurs with shorter/longer cavity than 75% of the chord length. For cascades, the characteristic length is the blade spacing and various modes of instabilities are predicted when the mean cavity is longer than 65% of the spacing. In the last part, rotating choke is shown to occur when the cavity becomes longer than the spacing.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.278-284
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• 2000

The method of Impinging jet was applied lots of part in industrial field as a cooling of as gas turbine blade, a annealing of metal and plastic sheets, drying of textile, veneer paper, X-ray medical devices, laser weapons and electronic components. This study's main factor is reciprocating Jet impingement perpendicular to the heated Surface. We researched the effect of heat transfer and enhancement with pulsating air jet. The pulsating air jet has an improvement in pulsating Frequencies((f= 0.5, 1, 1.5, 3Hz) and nozzle-to-plate distances($l/d=\;2{\sim}4,\;6{\sim}8,\;4{\sim}6,\;8{\sim}10$).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.954-960
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• 2001

Axial fans are widely used in heavy machines due to their ability to produce high cooling of engines. At the same time. the noise generated by these fans causes or serious problems. This work is concerned with the low noise technique of discrete. The prediction model. which allowed the calculation of acoustic pressure at the frequency and it's harmonics, has been developed by Farrasat and the Helmholtz-Kir. The newly developed Helmholtz-Kirchhoff BEM for thin body is used to calculate the sound field of the fan that is located in a engine room. To calculate the unsteady resultant force over blade. Time-Marching Free-Wake Method are used. The fan noise of fan sys unsymmetric engine-room is predicted. In this paper. the discussion is confined to and discrete noise of axial fan and front Part of engine room in heavy equipments.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.567-571
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• 2011

Air Starter motors are used for the start of medium-speed diesel engine. One of the main part of air starting motors is the axial turbine stage. In this study, design of 1-stage axial type turbine for 14kw class air starter motors has been performed. The turbine blade was designed based on mean-line analysis. 1-D design calculation and numerical analysis with CFD were conducted iteratively. The validation between 1-D design method and numerical analysis for axial clearance has been performed. It revealed that there is optimum axial clearance of turbine design.

• Journal of Biosystems Engineering
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• v.23 no.2
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• pp.187-194
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• 1998

This study was carried out to investigate mechanical properties o major part for agricultural machinery in Korea. The results are as follows ; 1. The mechanical Properties for heat resisting steel bars, alumium alloy castings, carbon steel for machine structural use, chromium molybdenum steels, high strength brass castings and carbon tool steels are proper for Korean standard. 2. The mechanical properties fir spring steels used to mould board, share of plow and blade of rotary are not suitable to Korean standard. Ⅰ think that a counterplan for quality rising is necessary such as supply of good quality materials and improvement of new materials in Korean agricultural machinery.

• Journal of Power System Engineering
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• v.3 no.3
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• pp.54-59
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• 1999

The purpose of the present study was to develop the numerical method for predicting the on-design and off-design performance of multistage axial-flow compressors. The aerodynamic properties in blade rows were analyzed by incorporating the streamline curvature method as a quasi 3D analysis with the imperical modeling of exit flow angle and loss coefficients. The present calculation procedure has been tested by applying to 5-stage compressors and good agreement with experiments has been found. The detail analysis of aerodynamic performances has been done on the compression part of the bench-scaled gas turbine engines. The predicted performance map at the variable speedline and flow rates could be used as a guide of the engine operation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1153-1160
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• 2010

A circular plate is the main part of a circular saw blade, which is widely used in industrial cutting tools. In experiments using a circular saw containing slots, we observed that a number of natural frequencies are simultaneously emerged in specific frequency regions. The interesting phenomenon is called the frequency convergence. Effects of design parameters such as the number, the length and the width of slots, on the frequency-convergence phenomenon are analyzed by FEM simulations using ALGOR. The frequency-convergence phenomenon will be intensified when the number, length and width of slots increase.