• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1598-1603
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• 1994

A preliminary design procedure for a multi-stage axial compressor is developed, which is based on the stage-stacking method. It determines the flow coefficient which gives rise to the design conditions required such as pressure ratio, mass flow rate and rotational speed for a given specific mass flow rate at inlet to a compressor. With this flow coefficient, blade radii, every stage and compressor performance characterics such as stage pressure ratio, adiabatic efficiency etc. are calculated by stacking each stage performance characteristics. It is shown that there is an optimum number of stage which results in the maximum of compressor overall efficiency for a given specific mass flow rate at inlet to a compressor. A test design was tried for three different geometric design constraints, and comparison with a previous study shows that present procedure could be used reliably in determining the number of compressor stage in preliminary design stage.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.8
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• pp.1077-1084
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• 2000

In this work, a modified stage-stacking method for the performance prediction of multi-stage axial flow compressors is proposed. The method is based on a simultaneous calculation of all interstage variables (temperature, pressure, flow velocity) instead of the conventional sequential stage-by-stage scheme. The method is also very useful in simulating the effect of changing angles of the inlet guide vane and stator vanes on the compressor operating characteristics. Generalized stage performance curves are used in presenting the performance characteristics of each stage. General assumptions enable determination of flow path data and stage design performance. Performance of various real compressors is predicted and comparison between prediction and field data validates the usefulness of the present method.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.789-794
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• 2001

In this study, a program for the off-design performance prediction of multi-stage axial-compressors is developed based on stage-stacking method. To account for the increased losses at off-design conditions, generalized performance curve is applied. The purpose of this study is to investigate the influence of the choice of generalized performance curve and stator exit angle. For this purpose, we tested various generalized performance curves and stator exit angles. In conclusion, Muir's pressure coefficient curve gives a good prediction results regardless of the efficiency curve for a low-stage compressors. On the other hand, for high-stage compressors, The combination of Muir's pressure coefficient curve and Stone's efficiency curve gives a optimistic results. Stator exit angle has a small effect on overall performance curve.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.74.2-74.2
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• 2005

• ETRI Journal
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• v.32 no.2
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• pp.327-329
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• 2010

A fully integrated small form-factor HBT power amplifier (PA) was developed for UMTS Tx applications. For practical use, the PA was implemented with a well configured bottom dimension, and a CMOS control IC was added to enable/disable the HBT PA. By using helix-on-pad integrated passive device output matching, a chip-stacking technique in the assembly of the CMOS IC, and embedding of the bulky inductive lines in a multilayer substrate, the module size was greatly reduced to 2 mm ${\times}$ 2.2 mm. A stage-bypass technique was used to enhance the efficiency of the PA. The PA showed a low idle current of about 20 mA and a PAE of about15% at an output power of 16 dBm, while showing good linearity over the entire operating power range.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.143-148
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• 2001

In this study, to investigate the effect of the generalized performance curve on the performance prediction and to find the optimal ones, a systematic study is performed. For this purpose, we compared the influence of the stage performance curves with experimental data in multi-stage axial compressors. As a result, it is discovered that the optimal generalized performance curves vary according to the number of the stages in compressors. And we found that for a low-stage compressors, Muir's pressure coefficient curve gives the best prediction results at design rotational frequency regardless of the efficiency curve. On the other hand, for high-stage compressors, Stone's pressure coefficient curve gives the optimistic results about the performance prediction at design rotational frequency.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.4
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• pp.1-8
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• 2012

In this study, numerical method, stage stacking method based on the result of numerical method and scaled stage stacking method have been applied to predict the performance of a multi-stage axial compressor with inlet guide vane. The results obtained through three different methods for off-design conditions were compared with performance test data. And the effect the angle of variable inlet guide vane was also investigated. The three-dimensional numerical simulation has been performed by using flow analysis program, $FLUENT^{TM}$ 6.3 and the performance prediction based on the stage stacking method has been performed with compressor analysis code from NASA.

• The KSFM Journal of Fluid Machinery
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• v.9 no.3 s.36
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• pp.7-13
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• 2006

Shape optimization of a rotor blade in a single-stage transonic axial compressor has been performed using a response surface method and three-dimensional Navier-Stokes analysis. Two shape variables of the rotor blade, which are used to define a blade skew, are introduced to increase an adiabatic efficiency. Throughout the shape optimization of a rotor blade, the adiabatic efficiency is increased to about 2.2 percent compared to that of the reference shape of the stator. The increase in efficiency for the optimal shape of the rotor is due to the pressure enhancement, which is mainly caused by moving the separation position on the suction surface of rotor blade to the downstream direction.

• Computers and Concrete
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• v.32 no.5
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• pp.513-525
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• 2023

Recently, research on predicting the behavior of reinforced concrete (RC) columns using machine learning methods has been actively conducted. However, most studies have focused on predicting the ultimate strength of RC columns using a regression algorithm. Therefore, this study develops a successive machine learning process for predicting multiple nonlinear behaviors of rectangular RC columns. This process consists of three stages: single machine learning, bagging ensemble, and stacking ensemble. In the case of strength prediction, sufficient prediction accuracy is confirmed even in the first stage. In the case of displacement, although sufficient accuracy is not achieved in the first and second stages, the stacking ensemble model in the third stage performs better than the machine learning models in the first and second stages. In addition, the performance of the final prediction models is verified by comparing the backbone curves and hysteresis loops obtained from predicted outputs with actual experimental data.

• Advanced Composite Materials
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• v.18 no.4
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• pp.297-314
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• 2009

A design method is proposed to optimize the stacking sequence of laminated composite plates for desired vibration characteristics. The objective functions are the natural frequencies of the laminated plates, and three types of optimization problems are studied where the fundamental frequency and the difference of two adjacent frequencies are maximized, and the difference between the target and actual frequencies is minimized. The design variables are a set of discrete values of fiber orientation angles with prescribed increment in the layers of the plates. The four lamination parameters are used to describe the bending property of a symmetrically laminated plate, and are optimized by a gradient method in the first stage. A new technique is introduced in the second stage to convert from the optimum four lamination parameters into the stacking sequence that is composed of the optimum fiber orientation angles of all the layers. Plates are divided into sub-domains composed of the small number of layers and designed sequentially from outer domains. For each domain, the optimum angles are determined by minimizing the errors between the optimum lamination parameters obtained in the first step and the parameters for all possible discrete stacking sequence designs. It is shown in numerical examples that this design method can provide with accurate optimum solutions for the stacking sequence of vibrating composite plates with various boundary conditions.