• 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.33 no.2
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• pp.141-148
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• 2009

Axial-flow compressor is one of the most important parts of gas turbine units with axial turbine and combustor. Therefore, precise prediction of performance is very important for development of new compressor or modification of existing one. Meanline analysis is a simple, fast and powerful method for performance prediction of axial-flow compressors with different geometries. So, Meanline analysis is frequently used in preliminary design stage and performance analysis for given geometry data. Much correlations for meanline analysis have been developed theoretically and experimentally for estimating various types of losses and flow deviation angle for long time. In present study, meanline analysis program was developed to estimate compressor losses, incidence angles, deviation angles, stall and surge conditions with many correlations. Performance prediction of one stage axial compressors is conducted with this meanline analysis program. The comparison between experimental and numerical results show a good agreement. This meanline analysis program can be used for various types of single stage axial-flow compressors with different geometries, as well as multistage axial-flow compressors.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.419-426
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• 2004

A three-dimensional computation was conducted to understand effects of the inlet boundary layer thickness on the loss mechanism in a low-speed axial compressor operating at the design condition(${\phi}=85\%$) and near stall condition(${\phi}=65\%$). At the design condition, the flow phenomena such as the tip leakage flow and hub comer stall are similar independent of the inlet boundary layer thickness. However, when the axial compressor is operating at the near stall condition, the large separation on the suction surface near the casing is induced by the tip leakage flow and the boundary layer on the blade for thin inlet boundary layer but the hub corner stall is enlarged for thick inlet boundary layer. These differences of internal flows induced by change of the boundary layer thickness on the casing and hub enable loss distributions of total pressure to be altered. When the axial compressor has thin inlet boundary layer, the total pressure loss is increased at regions near both casing and tip but decreased in the core flow region. In order to analyze effects of inlet boundary layer thickness on total loss in detail, using Denton's loss models, total loss is scrutinized through three major loss categories in a subsonic axial compressor such as profile loss, tip leakage loss and endwall loss.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.619-622
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• 2002

It has been recognized that the flow in the blade passage of an axial turbomachinery rotor is very complex and is influenced by various flow phenomena, of which the tip leakage flow passing through the gap between rotor blade tip and casing plays a significant role. The losses produced due to the existence of the clearance have been known to be a large contributor of the rotor overall losses. Despite several experimental studies on non-rotating blade in the cascade configuration, and on actual rotating blades, the detailed nature of the complex flow phenomena associated with tip leakage, however, remains largely unresolved. Thus, a single-stage compressor test rig was built and measurements were taken at upstream and downstream of the rotor of this compressor at the aerodynamics laboratory of University of New South Wales. A five-hole probe and a hot-wire probe were used to measure mean and fluctuating flow parameters. The results show that tip leakage losses rise rapidly beyond tip gap of 0.01 Furthermore, the present project also identifies the regions in the wake behind the rotor of the axial compressor where such losses are concentrated. These results should be useful in the better design of rotors for improved performance of axial compressor.

• International Journal of Fluid Machinery and Systems
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• v.6 no.4
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• pp.189-199
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• 2013

A practical method of surge simulation in a system of a high-pressure-ratio multistage axial flow compressor and ducts, named SRGTRAN, is described about the principal procedures and the details. The code is constructed on the basis of one-dimensional stage-by-stage modeling and application of fundamental equations of mass, momentum, and energy. An example of analytical result on surge behaviors is included as an experimental verification. It will enable to examine the transient flow phenomena caused by possible compressor surges and their influences on the system components in plant systems including high-pressure-ratio axial compressors or gas turbines.

• The KSFM Journal of Fluid Machinery
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• v.11 no.6
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• pp.46-53
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• 2008

Flow structures in an axial compressor with a non-uniform tip clearance were predicted by solving a simple prediction method. For more reliable prediction at the off-design condition, off-design flow characteristics such as loss and flow blockage were incorporated in the model. The predicted results showed that flow field near the design condition is largely dependent on the local tip clearance effect. However overall flow field characteristics are totally reversed at off-design condition, especially at the high flow coefficient. The tip clearance effect decreases, while the local loss and flow blockage make a complicated effect on the compressor flow field. The resultant fluid induced Alford's force has a negative value near the design condition and it reverses its sign as the flow coefficient increases and shows a very steep increase as the flow coefficient increases.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.743-750
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• 2008

Asymmetric tip clearance in an axial compressor induces pressure and velocity redistributions along the circumferential direction in an axial compressor. This paper presents the mechanism of the flow redistribution due to the asymmetric tip clearance with a simple numerical modeling. The flow field of a rotor of an axial compressor is predicted when an asymmetric tip clearance occurs along the circumferential direction. The modeling results are supported by CFD results not only to validate the present modeling but also to investigate more detailed flow fields. Asymmetric tip clearance makes local flow area and resultant axial velocity vary along the circumferential direction. This flow redistribution 'seed' results in a different flow patterns according to the flow coefficient. Flow field redistribution patterns are largely dependent on the local tip clearance performance at low flow coefficients. However, the contribution of the main flow region becomes dominant while the tip clearance effect becomes weak as the flow coefficient increases. The flow field redistribution pattern becomes noticeably strong if a blockage effect is involved when the flow coefficient increases. The relative flow angle at the small clearance region decreases which result in a negative incidence angle at the high flow coefficient. It causes a recirculation region at the blade pressure surface which results in the flow blockage. It promotes the strength of the flow field redistribution at the rotor outlet. These flow pattern changes have an effect on the blade loading perturbations. The integration of blade loading perturbation from control volume analysis of the circumferential momentum leads to well-known Alford's force. Alford's force is always negative when the flow blockage effects are excluded. However when the flow blockage effect is incorporated into the modeling, main flow effects on the flow redistribution is also reflected on the Alford's force at the high flow coefficient. Alford's force steeply increases as the flow coefficient increases, because of the tip leakage suppression and strong flow redistribution. The predicted results are well agreed to CFD results by Kang and Kang(2006).

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.533-541
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• 2005

Compared to axial compressors, an analytical model capable of analyzing the flow in centrifugal compressor lacks because of the difficulty in governing equations for radial duct. Therefore, this paper presents a new model to predict flow field in a centrifugal compressor with a sinusoidal asymmetric tip clearance. To predict the 2 dimensional flow in the inlet and exit of the centrifugal compressor, the two flow fields are connected with compressor characteristic based on Moore-Greitzer model. Contrary to axial compressors, the nonuniformity of impeller exit pressure in centrifugal compressor decreases as flow coefficient decreases. In addition, that is sensitive to the slope of pressure rise by eccentricity. The maximum velocity exists right before the maximum tip clearance.

• The KSFM Journal of Fluid Machinery
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• v.15 no.1
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• pp.64-69
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• 2012

Currently axial flow compressor is used primarily in a large power generation gas turbine. In this paper,the main factors to be considered when designing a axial flow compressor were compared to those of a small power generation gas turbine(DGT-5). The main design parameters was examined in the aspect ratio, solidity, as well as reaction, diffusion factor, incidence angle, etc. The results in case of a small compressor are showed a regular pattern but there were not found any specific design patterns for a large class compressor.

• Journal of Power System Engineering
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• v.2 no.3
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• pp.15-20
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• 1998

An integrated computing system has been developed for a Navier-Stokes design procedure of an axial-flow compressor blades. The process is done on the four separate steps, i.e., determination of the basic profiles, generation of computational grids, cascade flow simulation and analysis of the computed results in design sense. Applications are made to the blade design of the LP compressor. Computational results are analyzed with respect to the flow-field characteristics and are compared with the expected design requirements. The present system are coupled with the design procedure of the turbomachinery blades using the Navier-Stokes technique.