Abstract
The “Smith Chart” has been recognized as an indispensable technique when applied to the initial design of axial compressors and turbines. The Smith Chart offers a simple method to locate the region of optimum efficiency which is achievable as a function of flow and work coefficient. The result is a targeted flow state represented by the velocity triangles that result from these coefficients.
The process was originally developed, and is best documented, for axial turbines1. Over the years, several publications, of similar methods for axial compressors have been put forward. The author presented one such work2 which made significant use of optimization to develop an improved Smith chart for moderate Mach number compressor designs. In the current work, these results are expanded to both low Mach number (basically incompressible) to high-speed transonic cases as well. Similar to the previous work, the effort makes extensive use of optimization to systematically explore the optimum 2D profile shapes for a wide range of target flow and work coefficients. The method uses an FNS quasi-3D CFD solver, coupled to an efficiently parameterized geometry generator, combined with an automated optimization process. The process was applied independently to dozens of flow and work coefficient points to generate comprehensive maps of performance.
Results are shown for three different relative inflow Mach numbers: 0.2, 0.75, and 1.1. The maps are displayed in classic Smith chart format of islands of stage efficiency as a function of the flow and work coefficient. Specifically, the results are for axial compressor stages of 50% reaction, the theoretical ideal reaction for 2D flow. The results and the implications over varying Mach numbers are discussed. Also included is an expanded discussion of the range and accuracy of various meanline modeling methods, along with their ability to determine the optimum design condition.
Non-axisymmetric complete flow conditioning gauzes
