• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.895-903
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• 2004

In this paper are presented the blade vibration characteristics at the starting conditions of the low pressure multistage axial compressor of heavy-duty 100 MW gas turbine. Vibration data have been collected through strain gauges during aerodynamic tests of the model compressor. The influences of operating modes at the starting conditions are investigated upon the compressor blade vibrations. The exciting mechanisms and features of blade vibrations are investigated at the surge, rotating stall, and buffeting flutter. The influences of operating modes upon blade dynamic stresses are investigated for the first and second stages. It is shown that a high dynamic stress peak of 120 MPa can occur in the first stage blades due to resonances with stall cell excitations or with inlet strut wake excitations at the stalled conditions.

• 전기의세계
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• v.27 no.5
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• pp.69-75
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• 1978

3 phase induction motor applied in the method of connecting it directly across the line needs large current when it starts. At that time, leakage magnetic pathes of interior of the motor are severely saturated and leakage reactances are decreased because of saturation. Consequently, increased current and raised powerfactor yield increase of starting torque. The author, noticing those phenomena, derived experimentally the raion of decreasing leakage reactance from the fact that when voltage applied to motor is increased under locked condition the magnitude of current and phase angle are varied, and determined tha equations of starting current and starting torque, considering the decrease of leakage reactance by the large starting current. The author calculated the characteristics of Current-Time and Speed-Time with the determined equation at specific load conditions, and compared the values obtained from above calculations with those from circle diagram's method and the practically recorded values at same load conditions. Therefore, the authos got a confidience that the results of the derived theory coincide with the practically measured values more well than circle diagram's results and circle diagram's equation should be modified in order to analize the starting status of a induction motor.

• International Journal of Automotive Technology
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• v.8 no.3
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• pp.289-298
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• 2007

A nonlinear dynamic simulation model from cranking to idle speed is developed to optimize the cold start process of a diesel engine. Physically-based first order nonlinear differential equations and some algebraic equations describing engine dynamics and starter motor dynamics are used to model the performance of cold starting process which is very complex and involves many components including the cold start aiding method. These equations are solved using numerical schemes to describe the starting process of a diesel engine and to study the effects of cold starting parameters. The validity of this model is examined by a cold start test at $-20^{\circ}C$. Using the developed model the effects of the important starting variables on the cold starting processes were investigated. This model can be served as a tool for designing computer aided control systems that improve cold start performance.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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• pp.148-154
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• 2014

This paper describes problems of the sensorless starting of horizontal axis washing machines with direct drive and suggests solution, which was experimentally verified. Horizontal axis washing machines have very difficult conditions for the drive starting, especially at full load. Inertia of the tub and water, torque from the laundry make load torque at starting higher than rated one and sometimes even higher than the maximum torque of the motor, which makes sensorless starting extremely challenging task. This paper suggests modified open-loop starting, where control system is closed shortly after beginning at low speed and rotates the drum until laundry restructuring. To ensure proper work of the sensorless algorithm at low speed additional measures for increasing of the estimation algorithm performance have been taken. These measures include special algorithm for the drive parameters estimation, which has been developed and verified by the experimental results.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.1-9
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• 2004

During the SI engine starting up, starting conditions directly contribute to the unburned hydrocarbon emissions in spark ignition engines. The effects of catalyst temperatures and fuel injection skip methods on HC emissions were investigated. The test was conducted on a 1.5 L, 4-cylinder, 16 valve, multipoint-port-fuel-injection gasoline engine. To understand the formation of HC emissions, HC concentration was measured in an exhaust port using a Fast Response Flame ionization Detector (FRFID). The result showed that HC emissions, which were emitted at the cold coolant and catalyst temperature, were generated much higher than those of hot coolant and catalyst temperatures. In additions, fuel injection skips reduced highly HC emissions. It is convinced that optimized fuel injection skip method according to coolant and catalyst temperatures could be applied to reduce HC emissions during the SI engine starts.

• Journal of Navigation and Port Research
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• v.33 no.2
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• pp.127-134
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• 2009

If the research on double cycle is revitalized, crane productivity will be rapidly improved bemuse double cycle is an operational technique that can maximize equipments efficiency (Quay crane, RMG/RTG, Yard tractor). Unfortunately, it is very difficult for terminal operators to find out the starting point of double cycle bemuse the loading & unloading pattern and conditions are various. Therefore, terminal operators are apt to fail to find out the optimal starting point of double cycle to maximize its frequency. Experiencing the same mistakes in the process we made efforts to find out the optimal starting point, finally we found out the formula for it. And we verified its precision is perfect through a lot of testing. This paper on double cycling focused on making the formula to find out optimal starting point of double cycle to maximize its frequency. And it can be applied to various ships' stowages in common.

• Korean Journal of Environment and Ecology
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• v.29 no.3
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• pp.344-352
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• 2015

This study aims to identify the difference in the starting time of the dawn chorus of different species of birds and related environmental conditions. For this study, the bird songs were recorded every 2 hours a day starting from 2 hours before sunrise for a whole spring season (from April to June, 2014) in Korea. The recorded sounds were analyzed to find the starting time of each species' song by sonogram pattern using a sound analyzing program (Adobe Audition CC). To analyze the relationship between the environmental conditions and the time of the birdsong of each species, we collected the data of environmental conditions: daily precipitation, Julian date, time of sunrise and moonrise, temperature data and twilight time from the Korea Meteorological Office. As a result of this study, it was found that there are several statistical correlation between the starting time of the birdsong and environmental conditions (every environmental condition except daily precipitation and time of moonrise). Also, the difference of the starting time among each species were identified. The species were divided into 3 groups (early, mid and late) by their wake-up time. Ring-necked pheasant and yellow-throated bunting were categorized as 'Early' group and all woodpeckers were categorized as'Late' group. This study is significant as it first presented a classification of wild birds in Korea by the starting time of their dawn chorus. However, further studies are required to identify why each species to do their dawn singing at different times.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.829-832
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• 2010

For gas turbine engine starting, external power should be supplied with engine to accelerate to suitable rotational speed for air and fuel ignition conditions. Electric starting system for small gas turbine engine has simple system and light weight, so it is generally used for small aircraft. For system analysis of gas turbine engine electric starting system, Characteristics of battery, start motor, engine drag torque should be analyzed and theirs temperature effects should be considered. In this paper, preliminary design procedure of small gas turbine engine electric starting system and major design parameters were described.

• Journal of Power System Engineering
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• v.10 no.1
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• pp.5-11
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• 2006

During the SI engine starting up, starting conditions directly contribute to the harmful emissions in spark ignition engines. The effects of catalyst temperatures and fuel injection skip methods on HC emissions were investigated. The test was conducted on a 1.5L, 4-cylinder, 16 valve, multipoint-port-fuel-injection gasoline engine. To understand the formation of HC emissions, HC concentration was measured in an exhaust port using a Fast Response Flame Ionization Detector(FRFID). The result showed that HC emissions, which were generated during initial stage of the starting, could be reduced by coolant temperature and fuel injection skips. And through the vehicle test of ECE15+EUDC, it is convinced that the optimized fuel injection skip method according to coolant temperatures have favourable effects on the reduction of harmful exhaust emissions including HC during the SI engine start.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.3
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• pp.213-220
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• 2023

In this study, we report the effect of starting materials on the grain size in a multi-component system at high pressure experiments. We used two different starting materials, glass and nano powders, to synthesize bridgmanite in the reduced conditions in the presence of calcium-ferrite-phase MgAl₂O₄ to compared the grain size of synthesized samples. After synthesizing the sample at 40 GPa, 2000 K for 20 hrs, the sample from glass showed the grain size of 50-200 nm whereas the one from nano powders has ~500 nm of grains. This difference may come from 1) the temperature of 2000 K which is low enough for glass starting materials to make more crystal nucleis than to grow crystal size or 2) the possible difference in the redox state of starting materials. It is suggested that the using of nano powders is better to synthesize bigger grains in high pressure experiments with multi-component systems rather than using glass starting materials.