Computational Fluid Dynamics in Turbomachinery Design

The evolution of turbomachinery technology can be traced back several centuries and has resulted in the high efficiency turbomachines of today. Since the 1940s, turbomachinery development has been led mainly by gas turbine and aeroengine development, and the growth in power within the past 60 years has been dramatic. The development of numerical methods and the increasing computing capacity helped establish a strong design capability in the industry.

The first numerical methods related to turbomachinery were developed years before the use of digital computations. In 1951 Wu [1] introduced the blade-to-blade (S1) and hub-to-tip (S2) stream surfaces, which dominated the field until the 1980s when computer resources made it possible to account for 3D methods. The axisymmetric S2 calculations, also called “throughflow calculation” became the backbone of turbomachinery design, while the S1 calculation remains the basis for defining the detailed blade shape.

Fully 3D methods replaced the stream surface calculations by a single calculation for the whole blade row. This removed the modelling assumptions of the quasi three-dimensional approach but required far greater computer power and so was not usable as a routine design tool until the late 1980s. For similar reasons, early methods had to use coarser grids that introduced larger numerical errors than in the Q3D approach. Such limitations are now overcome with the rapid growth of computer technology.

Nowadays, the design of advanced turbomachinery components [2] is facing more demanding requirements. Higher performance must be achieved within shorter design cycles and at lower cost. Ambitious objectives in the reduction of weight, complexity and manufacturing cost lead to fewer compressor and turbine stages, and therefore to increased stage loading. For designers, this new situation implies the capability to control the very complex flow phenomena occurring in highly loaded stages, on the whole operating range of the engine, early in the design process. In addition to aerodynamic performance, the aggressive design of advanced, fully 3D blades also requires an early focus on all the aspects related to engine mechanical limitations such as blade flutter, forced response and thermal constraint.

The increased requirements on 3D CFD modelling lead to parallel processing of the flow phenomena. The majority of commercial CFD tools demands additional cost for parallel computing, which increase the total cost of the design process. With AxCFD, the users have the opportunity to use parallel calculation without the need to pay extra! AxCFD along with all design modules is fully integrated in the AxSTREAM Software Suite, the most complete engineering platform on the market. Try it now and enjoy the comfort of designing turbomachines from scratch to complete 3D CAD in a couple of hours.

References:

[1] Wu, C. H. A general through flow theory of fluid flow with subsonic or supersonic velocities in turbomachines of arbitrary hub and casing shapes. NACA paper TN2302, 1951
[2] H. Joubert, H. Quiniou, “Turbomachinery designed used intensive CFD”, Snecma http://www.icas.org/ICAS_ARCHIVE/ICAS2000/PAPERS/ICA6104.PDF 

Leave a Reply