• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.9
• /
• pp.1292-1301
• /
• 2002

An experimental study of turbine performance is conducted with various incidence angles on a rotating turbine rotor. 5 different incidence angles are applied from -17$^{\circ}$to 13$^{\circ}$with 7.5$^{\circ}$gaps. In order to precisely set up the incidence angles at the rotor inlet, 5 turbine discs are manufactured with the different fir tree section. Total-to-total efficiencies are obtained on the several off-design points with considering the exit total pressure, which is meas fred at 12 locations between the hub and casing using a pressure rake. The degree of reaction is 0.373 at the mean radius, and Reynolds number based on the rotor chord is 0.86$\times$10$^{5}$ at the turbine inlet on the design point experiment. The experiment on a single-stage turbine is conducted at the low-pressure and low-speed state, but it is sufficient to consider the blade loading effect due to the rotating apparatus even though the total pressure loss at the exit is increased proportionally to the turbine output power. The experimental results recommend 6$^{\circ}$as an optimum incidence angle on the turbine blade design. The total-to-total efficiency is steeply decreased when the incidence angle is over $\pm$9$^{\circ}$ from the optimum incidence angle. In the range of less than -10$^{\circ}$incidence angle, 7.5$^{\circ}$ reduction of incidence angle generates 15% decrease of total-to-total efficiency. This result is obtained on the same rotor blade by changing only the rotational speed to minimize the effect of profile and secondary flow loss in the passage. Experimental results show that the change rate of total-to-total efficiency according to the incidence angle change is unchanged although the turbine operates at the off-design condition.

• Asian-Australasian Journal of Animal Sciences
• /
• v.21 no.7
• /
• pp.947-953
• /
• 2008

We studied genetic diversity and relationships among Mongolian goat populations on the basis of microsatellite DNA polymorphisms. DNA samples from eight populations (Bayandelger, Ulgii Red, Zavkhan Buural, Sumber, Zalaajinst White, Erchim Black, Dorgon, and Gobi Gurvan Saikhan) from geographically distinct areas of Mongolia were analyzed by using 10 microsatellite DNA markers. Since the 10 markers were highly polymorphic, the genetic characteristics of these native goat populations could be estimated. Genetic diversity within populations, as estimated by the expected heterozygosities, was high, ranging from 0.719 to 0.746, but genetic differentiation between populations was low, representing only 1.7% of the total genetic variation. The results suggest that Mongolian native goat populations still have a semi-wild genetic structure reflecting traditional Mongolian nomadism and the short history of artificial selection. The genetic relationships among the populations were not clear in the neighbor-joining tree generated from the modified Cavalli-Sforza chord genetic distances. By using principal components analysis, the five core populations of Mongolian native goats (Bayandelger, Ulgii Red, Zavkhan Buural, Sumber, and Dorgon) and the populations crossed with Russian breeds (Zalaajinst White, Erchim Black, and Gobi Gurvan Saikhan) were distinguished. There was no correlation between genetic relationships among the populations and the geographical distribution of the populations.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1121-1125
• /
• 2004

The RT(Robot Technology) has been developed as the next generation of a future technology. According to the 2002 technical report from Mitsubishi R&D center, IT(Information Technology) and RT(Robotic Technology) fusion system will grow five times larger than the current IT market at the year 2015. Moreover, a recent IEEE report predicts that most people will have a robot in the next ten years. RCP(Robotic Cellular Phone), CP(Cellular Phone) having personal robot services, will be an intermediate hi-tech personal machine between one CP a person and one robot a person generations. RCP infra consists of $RCP^{Mobility}$, $RCP^{Interaction}$, $RCP^{Integration}$ technologies. For $RCP^{Mobility}$, human-friendly motion automation and personal service with walking and arming ability are developed. $RCP^{Interaction}$ ability is achieved by modeling an emotion-generating engine and $RCP^{Integration}$ that recognizes environmental and self conditions is developed. By joining intelligent algorithms and CP communication network with the three base modules, a RCP system is constructed. Especially, the RCP interaction system is really focused in this paper. The $RCP^{interaction}$(Robotic Cellular Phone for Interaction) is to be developed as an emotional model CP as shown in figure 1. $RCP^{interaction}$ refers to the sensitivity expression and the link technology of communication of the CP. It is interface technology between human and CP through various emotional models. The interactive emotion functions are designed through differing patterns of vibrator beat frequencies and a feeling system created by a smell injection switching control. As the music influences a person, one can feel a variety of emotion from the vibrator's beats, by converting musical chord frequencies into vibrator beat frequencies. So, this paper presents the definition, the basic theory and experiment results of the RCP interaction system. We confirm a good performance of the RCP interaction system through the experiment results.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.1
• /
• pp.229-240
• /
• 1991

The large camber angle theory of turbomachine blade of compressor has been developed recently for the two-dimensional flow by Hawthorn, et al. However, in the above theory it was assumed that the fluid was incompressible and inviscid, and the blades had no thickness. In this study, the flow in a blade cascade being mounted in parallel fashion with blade of arbitrary thickness is studied in order to determine the effects of the camber angle on the performance characteristic of the blade section under the consideration of compressibility and viscosity of fluid. The panel method is used for potential flow analysis. The flow in the boundary-layer is obtained by solving the integral boundary-layer structure through the laminar, transitional , and turbulent flow using the pressure field determined from the potential flow. And then the viscous-inviscid interaction scheme is used for interaction of these two flows. For the determination of the variation in the outlet fluid angle influenced by deviation in cascade flow, the superposition method which is used for single foil is introduced in this analysis. By the introduction of this method, the effects of the deviation on outlet fluid angle and the resulting fluid angle are made to adjust for oneself through the calculation. As the result of this study, the blade of large camber angle, large incidence angle, large pitch-chord ratio has large viscous and compressible effect than those of small camber angle. Lift force increase as camber angle increases, but above 60.deg. of camber angle, lift force decrease as camber angle increases. But drag force increases linearly with camber angle increases in the entire region.

• Composites Research
• /
• v.13 no.3
• /
• pp.9-20
• /
• 2000

Free vibration characteristics of a cantilevered laminated composite beam with multiple non-propagating transverse open cracks are investigated. In the present analysis a special ply-angle distribution referred to as asymmetric stiffness configuration inducing the elastic coupling between chord-wise bending and extension is considered. The multiple open cracks are modelled as equivalent rotational springs whose spring constants are calculated based on the fracture mechanics of composite material structures. Governing equations of a composite beam with open cracks are derived via Hamilton's Principle and Timoshenko beam theory encompassing transverse shear and rotary inertia effect is adopted. The effects of various parameters such as the ply angle, fiber volume fraction, crack numbers, crack positions and crack depthes on the free vibration characteristics of the beam with multiple cracks are highlighted. The numerical results show that the existence of the multiple cracks in an anisotropic composite beam affects the free vibration characteristics in a more complex fashion compared with the beam with a single crack.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.3
• /
• pp.37-45
• /
• 2002

The vortex flow and aerodynamic load characteristics of a $65^{\circ}$ sweep delta wing with the leading edge extension in sideslip condition is investigated experimentally. The freestream velocity is 40 m/sec, which corresponds to a Reynolds number per meter of $1.76{\times}10^6$ based on the wing root chord. The angles of attack range from $12^{\circ}$ to $28^{\circ}$, and the sideslip angles treated are $0^{\circ}$ , $-10^{\circ}$, $-20^{\circ}$. The LEX vortex of the leeward side. The LEX and wing vortics coalesce to to become a concentrated strong vortex or to break down at down at downstream position. Due to the interation of the LEX and wing vortices, a high suction pressure is maintained on the windward wing surface, and a low suction pressure is formed on the leeward wing surface

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.11
• /
• pp.18-25
• /
• 2006

Unsteady aerodynamic force measurements were carried out in order to investigate the effects of phase difference of a dragonfly-type model with two pairs of wing. A load-cell was employed to measure the aerodynamic force generated by a plunging motion of the dragonfly-type model. The dragonfly-type model has a dynamic similarity with real one, and incidence angles of fore- and hind-wing are 0° and 10°, respectively. Other experimental conditions are as follows: The freestream velocity was 1.6 m/sec and corresponding chord Reynolds number was 2.88×103, and phase differences of fore- and hind-wing were 0°, 90°, 180° and 270°. The variation of aerodynamic coefficients during one cycle of the wing motion is presented. Results show that the lift is generated during the downstroke motion and the drag generated during the hind-wing‘s downstroke motion with the lift generation.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.6
• /
• pp.530-536
• /
• 2010

In-flight icing is a critical technical issue for aircraft safety and, in particular, ice accretions on aircraft surfaces can drastically impair aerodynamic performances and control authority. In order to investigate icing effects on the aerodynamic characteristics of KC-100 aircraft, a state-of-the-art CFD code, FENSAP-ICE, was used. A main wing section and full configuration of KC-100 aircraft were considered for the icing analysis. Also, shapes of iced area were calculated for the design of anti-/de-icing devices. The iced areas around leading edge of main wing and horizontal tail wing were observed maximum 7.07% and 11.2% of the chord length of wing section, respectively. In case of wind shield, 16.7% of its area turned out to be covered by ice. The lift of KC-100 aircraft were decreased to 64.3%, while the drag was increased to 55.2%.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.10
• /
• pp.955-965
• /
• 2010

The MH-75 propeller for the MAV propulsion is designed using a free vortex design method which considers design parameters such as the hub-tip ratio, the twist angle distribution, the maximum camber location and the chord length of the propeller blade. Aerodynamic characteristics of the MH-75 propeller are predicted by changing the flight speed using the frequency domain panel method. And, the thrust characteristics of the MH-75 propeller are measured using the balance system of the subsonic wind tunnel for the validation of numerical results. The performance characteristics of the MH-75 propeller satisfied with design requirements. Numerical results of the MH-75, which are predicted by the frequency domain panel method, are more agree with experimental results compare with XFOIL.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.37 no.1
• /
• pp.1-8
• /
• 2001

This study deals with the experimental and numerical investigations to design the high performance otter board. Experiment was carried out to determine the most effective slot size of single-slot cambered otter board in the circulation water channel of BAEK KYUNG IND. Co. LTD. Numerical analysis was done by the commercial CFD code, FLUENT, to provide some valuable physical interpretations and finally to design the otter board section by numerical method. The major results are as follows ; 1. In experiment, the maximum lift and drag coefficients of simple cambered type otterboard were 1.41, 0.55, respectively, at the angle of attack $28^\circ$, while those of slot one with slot size 0.02C (C denotes the chord length) were 1.72, 0.42 at the angle of attack $24^\circ$. 2. The hydrodynamic characteristics depending upon slot size shows the greatest at 0.02C of the slot size. 3. Numerical results well visualized the streamlines, pressure fields, and speed vectors of a simple cambered and slot cambered otter board with slot size 0.02C. The slot cambered one with slot size 0.02C was shown that pressure field was distributed moderately on front and back side of otter board. And, the delay and decrease of separation were favorably achieved by flow through slot. 4. Computed result on the pattern of hydrodynamic field and the values of $C_L$ and $C_D$ by the commercial CFD code, FLUENT, show almost the same as those of the experimental result.