One-dimensional meanline method has always been a very valuable tool in prediction performance of modern transonic compressors. An improved model applied in it, such as incidence,deviation and loss considering compressibility , radius variations and real fluid effects,so that the transonic compressor’s operating behavior may be simulated more accurately.Moreover,the program can not only provide performance data including efficiency, pressure ratio, as well as inter-blade data for more accurate CFD modeling, but also integrate into the whole gas turbine simulations for more accurate modeling at off-design condition. The prominent issue here first considered is to establish the construction of the compressor model.

For design conditions, the minimum-loss incidence prediction are taken as an example. The most widely-known NASA SP-36 correlation which covers a wide range of parameters and were carefully examined for low-speed in two dimensional cascades (M≈0.1)is the base for calulating the reference incidence angle for design point with increasing inlet Mach number for certain blade shapes. Petrovic,Wiggins,Cetin use different types of single-stage or multistage compressor test data to correct this correlation for transonic compressor design process.Finally, The comparison between given data and calculated incidence angle have suggested that the method proposed by Wiggins is the most satisfactory one in determining the design incidence angle for transonic compressors.

For off-design conditions, this one-dimensional compressible flow program with fast convergence basically estimates the stage and cumulative compressor performance from meanline velocity diagrams located at rotor inlet and outlet meanline radii. A surge model, different from the well-known maximum static pressure rise method of Koch and smith,is introduced in this program to calculate the stage surge and chock flow rate.Stage stall flow can be calculated directly with high computing precision according to the aerodynamic separation load coefficient of rotor and stator. The aerodynamic separation stage load coefficient is closely related to the rotation speed, Reynolds number and the inlet hub-tip ratio. For chock prediction model, by adjusting the inlet flow rate of the compressor,the flow rate can gradually approach the blocking flow rate. When the maximum Mach number of the flow through the cascade is calculated by empirical formula to be greater than or equal to 1, flow rate is the blocking flow rate.The maximum Mach number that the cascade passage allows flow to pass is related to the geometric throat area and flow angle.

A discussion of the results then follows, two-stage NACA transonic fan, eight-stage NACA transonic compressor and ten-stage axial transonic compressor are calculated by this method.The speedlines and aerodynamic parameters are compared with the experimental data to demonstrate the meanline approach presented in this study. Restrictions, like manufacture difficulties and control problems, are not taken into account.

The results shown for accounting for the overall performance predictions using STAGESTACK(name of this program) were generally in good agreement with the test data,although the prediction errors that occur in some regions are a bit larger.On the whole,the method presented in this paper can predict compressor characteristics at both design and off-design conditions.The accuracy of the meanline solution depends heavily on models adopted.The deviation predictions are of errors when rotational speed are far from the design speed ,which means inadequate accounting for boundary layers and 3D effects.


Aerodynamic Performance Prediction of Transonic Axial Multistage Compressors Based on One-Dimensional Meanline Method"

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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