• 대한전기학회논문지:전력기술부문A
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• 제48권1호
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• pp.52-60
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• 1999

This paper deals with a fault detection and isolation scheme for a DC motor driven centrifugal pump system. The emphasis is placed on the design and implementation of the residual generatorm, based on parity relation, that provides decision logic unit with residuals that will be further processed to detect and isolate three important faults in the system;brush fault, impeller fault, and the speed sensor fault. Two process faults are modelled as multiplicative type faults, while the sensor fault as an additive one. With multiplicative fault, the implementation of the residual generator needs the time varying transformation matrix that must be computed on-line. Typical implementation methods lack in generality because only a numerical approximation around the assumed fault levels is employed. In this paper, a new implementation method using well tranined neural network is proposed to improve the generality of the residual generator. Application results show that the fault detection and isolation scheme with the proposed residual generator effectively isolates three major faults in the centrifugal pump system even with a wide range of fault magnitude.

• Journal of Biosystems Engineering
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• 제34권2호
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• pp.89-94
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• 2009

Aerial application using an agricultural unmanned helicopter was suggested for an alternative against current pesticide application methods. Centrifugal clutches play important roles in the performance and safety of the helicopter operation. A previous study analyzed and verified the power transfer theory of the guide type centrifugal clutch. Based on the clutch theory, optimal designs of the clutch became possible and feasible using a simulation method. Design criteria of the clutch were the power transfer capacity of 24.66 kW(33.5 PS) at the rated engine speed and the engaging range speed of 3,000${\sim}$3,500 rpm. Various designs were accomplished using the simulation. An optimal clutch was simulated by determining the values of spring constant and mass of friction sector, which were 94,700 N/m and 123.7 g, respectively. The design performed the power capacity of 24.86 kW(33.8 PS) and engagement speed of 3,069 rpm, meeting the design criteria. Using the designed clutch, an efficient transfer of the power would be possible for the unmanned agricultural helicopter.

• 한국주조공학회지
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• 제28권3호
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• pp.113-118
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• 2008

A new approach of producing martensitic structure for guide-roll materials was developed using centrifugal casting instead of classic overlay welding process. Centrifugal casting offered a simpler process, fewer defects and even microstructures. Especially in terms of thermal fatigue cracking which usually occurs in the HAZ of welding beads of used continuous caster guide roll materials made by overlay welding process. A typical tensile strength of 1,600 MPa was obtained by this process and was higher than typical tensile strength($800{\sim}1,200\;MPa$) with overlay welding technique. Tempering at $400{\sim}550^{\circ}C$ for 2 hrs was observed to have significant precipitate hardening effect which increases strength and elongation. Nitrogen content from the Cr-N input in the casting process was found to have positive contribution to decrease the volume fraction of ${\delta}$-ferrite which directly corresponds to increasing strength of the roll materials.

• 대한기계학회논문집B
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• 제28권11호
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• pp.1332-1338
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• 2004

This paper presents the response surface optimization method using three-dimensional Navier-Stokes analysis to optimize the shape of a forward-curved blades centrifugal fan. For numerical analysis, Reynolds-averaged Navier-Stokes equations with k-$\varepsilon$ turbulence model are discretized with finite volume approximations. In order to reduce huge computing time due to a large number of blades in forward-curved blades centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models. Three geometric variables, i.e., location of cut off, radius of cut off, and width of impeller, and one operating variable, i.e., flow rate, were selected as design variables. As a main result of the optimization, the efficiency was successfully improved. And, optimum design flow rate was found by using flow rate as one of design variables. It was found that the optimization process provides reliable design of this kind of fans with reasonable computing time.

• 대한치과기공학회지
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• 제7권1호
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• pp.5-12
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• 1985

This experimental study is perform to study the effect of the direction for the centrifugal force in operating centrifugal casting machine. In order to investigate the effect of direction for centrifugal force action on the casting ability 20 pieces of specimen are produced including one vertical direction and four horizontal directions. Casting shows us that the 15 pieces of specimen among them are included within $\pm$16. The results obtained through the comparison with 5 groups of the casting ability are as follows: 1. In the experiment of the casting, statistically significant difference are found between the vertical direction and the group of horizontal direction, namely, the direction of 3, 6, 9 and 12 o'clock, and also statistically there are significant differences between the direction of 9 o'clock and of 6 o'clock, and between the direction of 9 o'clock and of 12 o'clock which lie between the groups of horizontal directions. 2. The degree of casting ability is showing us on an average, 23.80 in the vertical direction. And also in the group of horizontal direction it prove in turn 15.60 in the direction of 9 o'clock, 14.47 of 3 o'clock, 13.30 of 12 o'clock, and 12.80 of 6 o'clock.

• 한국기계가공학회지
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• 제18권10호
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• pp.99-103
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• 2019

Recently, as the high-precision machinery industry has developed rapidly, peripheral equipment has been developed to improve machining efficiency. Peripheral equipment for machining includes cooling units, housings, oil separators, and much more. Oil, such as cleaning and cutting fluids, is used for machining. When waste oil is reused, the contamination of the workpieces and reduction in machining accuracy are generated by the waste oil, including sludge. Therefore, the development of an oil separator is necessary for efficiently separating oil, water, and sludge. The purpose of this study is to analyze the oil separation efficiency and flow characteristics of a high-speed centrifugal separator according to the rotation velocity and diffusion plate. The oil separation efficiency and flow characteristics were analyzed using hydrodynamic theory and computational fluid dynamics (CFD). The results of this study will be used as basic data for the development of a high-speed centrifugal separator.

• 한국염색가공학회지
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• 제32권4호
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• pp.239-244
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• 2020

Polyethylene (PE) micro-fiber have been prepared at different hot air temperature (60, 80 and 100 ℃) and different pressure (20, 40, 60 and 80 kPa) by melt centrifugal spinning technique. The parameters of melting centrifugal spinning including polymer contents, rotational velocity, temperature of hot air and pressure were optimized for the fabrication process. The study showed that 8000 rpm rotational velocity, 80 ℃ heated hot air and 40 kPa air pressure are the best condition to obtain uniform and strong PE fiber. The prepared PE fibers were analyzed by field emission scanning electron microscope and universal testing machine and found that fibers with reduced diameter and improved tensile strength are obtained at hot air condition.

• 한국기계가공학회지
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• 제21권2호
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• pp.101-108
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• 2022

Centrifugal pumps are typically used in many slurry industries to transport solid materials. Solid particles in the slurry frequently shock the walls inside the pump, significantly abrading the flow path. Wear damage causes replacement of the pump components, which wastes manpower and time. Therefore, previous studies have been conducted on factors to improve efficiency and life time. This study identifies trends in pumps supplying lime to desulfurized devices from thermal power plants. The shear stress transport(SST) model is used to determine the erosion trend of the centrifugal pump that transfers lime slurry. The purpose of this study is to identify efficiency and erosion trends by selecting three of the various impeller design elements. The three impeller blade design variables mentioned above represent the inlet draft angle and blade angle of leading edge(L.E) and trailing edge(T.E). The maximum value of the erosion density rate tends to be similar to the Input power.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.827-838
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• 2023

Centrifugal pump is a key part of nuclear power plant systems, and its health status is critical to the safety and reliability of nuclear power plants. Therefore, fault diagnosis is required for centrifugal pump. Traditional fault diagnosis methods have difficulty extracting fault features from nonlinear and non-stationary signals, resulting in low diagnostic accuracy. In this paper, a new fault diagnosis method is proposed based on the improved particle swarm optimization (IPSO) algorithm-based variational modal decomposition (VMD) and relevance vector machine (RVM). Firstly, a simulation test bench for rotor faults is built, in which vibration displacement signals of the rotor are also collected by eddy current sensors. Then, the improved particle swarm algorithm is used to optimize the VMD to achieve adaptive decomposition of vibration displacement signals. Meanwhile, a screening criterion based on the minimum Kullback-Leibler (K-L) divergence value is established to extract the primary intrinsic modal function (IMF) component. Eventually, the factors are obtained from the primary IMF component to form a fault feature vector, and fault patterns are recognized using the RVM model. The results show that the extraction of the fault information and fault diagnosis classification have been improved, and the average accuracy could reach 97.87%.

• 한국자동차공학회논문집
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• 제17권2호
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• pp.150-158
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• 2009

A centrifugal turbo blower is one of the part to generate electric power of fuel cell electric vehicle(FCEV). In order to generate the electric power of FCEV, the centrifugal turbo blower operates at very high speed above 30,000rpm in order to increase the pressure of the air, which supplied to a stack of FCEV, using rotation of its impeller blades. Vibration which originated from the blower is generated by unbalance of mechanical components, rotation of bearings and rotating asymmetry that rotate at high speed. The vibration is transmitted to receiving structure through vibration isolators and it can causes serious problems in the noise, vibration and harshness(NVH) performance. Thus, the study about reducing this kind of vibration is an important task. Quantifying the effectiveness of vibration isolation can be effectively accomplished by using vibrational power flow because relative contributions of each isolator to the total vibration transmission can be easily represented. In this paper, vibrational power flow is applied to the centrifugal turbo blower mounted on FCEV in order to analyze the most dominant vibration transmitting path. As a result, the main contributor among four isolators is a mount #3 of the blower. Also, a 30 percent lowering of the mount #3 stiffness shows 34 percent decrement of vibrational power flow by the simulation.