Diffusion factor limitations diffusion factor for a compressor blade element is a design parameter which is correlated with loss, separation, stability. Axial and centrifugal compressor mean line flow analysis. This differs from other rotating compressors such as centrifugal compressor, axicentrifugal compressors and mixedflow compressors where the fluid flow will include a. The stationary blades convert the kinetic energy of the fluid into pressure energy, and also redirect the flow into an angle suitable for entry to the next row of moving blades.
This paper deals with the design and analysis of a controlled diffusion aerofoil cda blade section for an axial compressor stator and effect of incidence angle and mach no. A tandem stator design is employed in this compressor because of the high diffusion factor in the rotor hub region. Performance limits of axial turbomachine stages by. National advisory committee for aeronautics collection and was provided to digital library by the unt libraries government documents department. Fouling is the most important performance degradation factor, so it is necessary to accurately predict the effect of fouling on engine performance. The first part of the centrifugal impeller looks very similar to an axial compressor. The new performance calculation method of fouled axial. Large incidence angles occur when the ratio axial velocity blade speed is low, i.
Axial compressor predesign tool the meridional solver that is used is acpredesign. In the previous research, it is very difficult to accurately model the fouled axial flow compressor. Axial compressor, diffusion factor, solidity, inletflow angle, cascade. The effects of diffusion factor, aspect ratio, and solidity on rotor and stage per formance have been evaluated for 14 subsonic compressor middle stages with a hubtip ratio of 0. The axial compressor is designed by integrating a variety of knowledge which includes fluid mechanics and. It is a rotating, airfoilbased compressor in which the gas or working fluid principally flows parallel to the axis of rotation, or axially. As the incidence angles increase in the compressor a point is reached when the flow begins to separate from the blades, with serious consequences. It solves the nonisentropic radial equilibrium equations for given design input parameters. Axial flow compressors usually consists of a series of stages. Diffusion factor for estimating losses and limiting blade loadings in axialflowcompressor blade elements page.
Axial compressor, diffusion factor, solidity, inletflow angle, cascade aerodynamics. Centrifugal compressors are similar to axial compressors in that they are rotating airfoilbased compressors. An axial compressor is a gas compressor that can continuously pressurize gases. Axial compressors are characterised by lower pressure ratio per stage at higher mass. Effects of diffusion factor, aspect ratio, and solidity. In practice it is usual to begin a compressor design with such a treatment, called a mean line design carried out at. Aerodynamic design and analysis of a lowreaction axial. Design and performance analysis of axial hydro turbine. The range of stable operation of axial flow compressor is narrow. Numerical simulations of a threedimensional compressible turbulent flow have been performed to explore the effect of the vortex generators on the reduction of.
The design of a heavilyloaded, supersonic axial compressor stage is described. Although it was developed using just a small range of compressor blade designs operating at a minimum loss condition, the diffusion factor is widely applied to a range of compressor designs, both compressible and incompressible, for preliminary design purposes. The diffusion factor first defined by lieblien is a bladeloading criterion. Darcy friction factor, 84 diffusion ratio centrifugal compressor, 284 radial inflow turbine, 350 doublesuction pump, 293 efficiency axial compressor stage, 225 axial turbine stage 191 centrifugal compressor, 273 centrifugal pump, 291 hydraulic turbine, 363 nozzle, 82 polytropic, 75 pressurecompounded steam turbine stage, 149. The compressors in most gas turbine applications, especially units over 5mw, use axial fl ow compressors. Best lift to drag ratio is found at inlet flow angle of 55o. A modified stagestacking method for multistage axial flow compressor calculations tonye k. Due care has to be taken to match the components for avoiding instability during operation when these compressors are used in gas turbine. Elder abstract in this paper an attempt was made at studying multisage axial flow compressor offdesign performance based on two existing. Work done factor is the ratio of the actual work absorbing capacity of the. Df diffusion factor fn net thrust fs, specific thrust fnrihcore.
Disclaimer notice defense technical information center. Elliott single stage compressors meet api specifications for demanding applications. Higher efficiency was found at the mean line between the root and tip of the blade. Diffusion factor for estimating losses and limiting blade. There is flow diffusion across stator blade rows, converting kinetic energy into. Characterization of tandem airfoil configurations of axial. Diffusion factor for estimating losses and limiting blade loadings in axialflowcompressor blade elements by seymour lieblein, francis c. The deviation angle is estimated from the exit flow conditions and the input slip factor. Scaling of incidence variations with inlet distortion for a transonic axial compressor d. Energy increase in an axialflow compressor, velocity triangles and the degree of reaction in an axialflow compressor are discussed. Performance prediction of an axial flow compressor design and. Table 1 design parameters of the test compressor parameter value.
It is not uncommon to have pressure ratios in industrial gas turbines in the 17 to 20. The blade loading is assessed by diffusion factor derived by lieblein. It contains the final compressor stages, and forms a compartment of inner and outer walls of the compressor diffuser. For constant axial velocity and incompressible flow the diffusion factor can be written as 3. Blade wake downstream of the exit of a compressor blade cascade. An axial fl ow compressor is one in which the fl ow enters the compressor in an axial direction parallel with the axis of rotation, and exits from the gas turbine, also in an axial direction. Performance limits of axial compressor stages core. The compressor discharge section is the final portion of the compressor section. Cd blade section has been designed at axial flow compressor research lab, propulsion division of national aerospace laboratories nal. Introduction design of axial turbine is usually using free vortex method with simple radial equilibrium assumed and due to its simplicity, although the real flow at the turbine is three dimensional and complex. The chapter starts with an analysis of the circumferentially averaged flow on the mean radius of an axial compressor.
Structural and conceptual design analysis of an axial. Design and analysis of a controlled diffusion aerofoil. An experimental investigation is conducted to study the details of instability inception in a transonic axial flow compressor. Generally, maximum pressure ratio achieved in a stage of axial compressor is about 1. D diffusion factor h enthalpy l streamwise coordinate. In incompressible flow with constant axial velocity, the lieblein diffusion factor in eq. Radial equilibrium, diffusion factor, the incidence rule and the deviation rule in relation to airfoil research are outlined.
As the incidence angles increase in the compressor a point is reached when the flow begins to. The code has been used to generate the performance map for the nasa 76 b three stage axial compressor featuring variable geometry. Loss representation is discussed together with the diffusion factor concept for estimating the loading capacity of blade rows. Experimental study of compressor instability inception in. On the application of variable camber blading in axial flow fans and compressors. A stage model is developed, consisting of a specified geometry and a surface. Two dimensional design of axial compressor main characteristics page 9 figure 16 lift and drag coefficient 1. Axialflow compressors national energy technology laboratory. Galvas also provides an empirically derived relationship which defines compressor surge based on vaned diffuser performance. To estimate diffusion factor on different operating modes for stages in compressor. Design and performance prediction of an axial flow. Scaling of incidence variations with inlet distortion for. Structural and conceptual design analysis of an axial compressor for a 100 mw industrial gas turbine ind100. This multistage axial compressor design program originally comes from creveling and carmody 1968 and has been recently implemented at vki.
Several stages of an axial compressor can be driven by a. Axial compressors principles of turbomachinery wiley. Diffusion factor for estimating losses and limiting blade loadings in axialflowcompressor blade elements r by seymour lieblein, francis c. A modified stagestacking method for multistage axial. Large incidence angles occur when the ratio axial velocityblade speed is low, i. The characteristics of compressor operation surge, choke, stall are described. Broderick a simplified limitingbladeloading parameter for axialflowcompressor blade elements was derived from the application of a separa. Axialflow compressors an overview sciencedirect topics. Diffusion factor for estimating losses and limiting blade loadings in axialflowcompressor blade elements one of 5,165 reports in the series. Experimental analysis of controlled diffusion compressor cascades with single and tandem airfoils. The variation of power, pressure ratio and efficiency of an axial flow compressor against flow rate is depicted in the fig. Coordinate system for axialflow compressor figure 5 shows the pressure, velocity, and total temperature variation for. Compressor casing could have a horizontal split casing or a vertical split casing.
The performance of axialflow compressors is known to be adversely affected by increasing the aspect ratio the ratio of blade height to chord length. Axial and centrifugal compressor mean line flow analysis method. Computational analysis and proposed redesign of the 3. The off design performance of an axial flow compressor is evaluated using axmap by selecting variables as total outlet pressure and. Compressor stage analysis design deflection radial equilibrium diffusion factor efficiency and losses cascade aerodynamics axial compressors principles of turbomachinery wiley online library. The axialfl ow compressor compresses its working fl uid by fi rst accelerating the fl. The experimental results indicate that the compressor instability is initiated through the development of a. Impellers elliott highefficiency impellers have an enclosed backward lean design.
Broderick summary a simplified limitingbladeloadingparameter for axialflowcompressor blade elements was derived from the application of a separa. The slip factor for axial compressors as defined by equation 22 in the appendix can be on the order of 0. Furthermore, the use of lift coefficient for the general compressor case of compressible flow with unequal axial velocities at bladeelement inlet and outlet presents. Pdf axial and centrifugal compressor mean line flow. Both are shown in the adjacent photograph of an engine with 5 stages of axial compressor and one stage of centrifugal compressor. Experimental investigations have been carried out on a singlestage, low speed axialflow compressor with a parallel annulus and a hubtip ratio of 0. The basic components of an axial flow compressor are a rotor and stator, the former carrying the moving blades and the latter the stationary rows of blades.
Diffusion factor for estimating losses and limiting blade loadings in axialflowcompressor blade elements. The compressor stages were aerodynamically matched at off design speeds by adjusting the variable inlet guide v ane and variable stator geometry angles to control the rotor diffusion factor and incidence angles. The stage target performance calls for an overall total pressure radio of 3. Axial spacing of the blade rows is not considered, since it may be set based on stability or mechanical constraints. It also should be remembered that the gas turbine axial flow. The test compressor is a transonic compressor stage which is actually used in an aeroengine, and the design parameters are shown in table 1. Compressor stage geomtry ratio r ir o, both of which are assumed constant. This paper develops a new performance calculation method of fouled multistage axial flow compressor based on experiment result and. Turbomachinery and unsteady flows research group, department of mechanical, automotive, and materials engineering. Thus, once the flow angles are fixed, a required level of diffusion factor can be used to set the pitchchord ratio.
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