For turbomachinery compressor designers, a delicate balance exists between system performance and system stability. It can be the deciding factor on whether an engine program is successful or not, which affects billions of dollars in revenue for large OEMs. As a designer moves towards higher compression ratio systems, managing stall margin becomes a critical factor. Optimizing airfoil design to maximize both performance and stall margin is a mature area, so designers need to look outside of traditional airfoil design to make further gains. One very promising area that is a current area of interest is non-axisymmetric endwall contouring. By contouring the endwalls, with a specific focus on the outer casing, the designer has additional tools at their disposal to manipulate the unsteady loading seen by the airfoils which allow for improvement to performance and stall margin at various points within the compressor map.
Novel casing treatment geometries have been shown experimentally to improve stall margin. However, they have not been widely adopted by industry due to the analysis complexity and the requirement of large scale unsteady simulations to attain meaningful results. Using current technologies, this analysis often requires hundreds of CPUs and weeks to complete just one analysis, precluding its use during the design cycle. The problem is also complicated by requiring extremely high-quality transfer of data along the sliding mesh interface. Traditional multi-block structured grids facilitate accurate and computationally inexpensive interpolation methods but are extremely difficult to generate for complicated endwall treatment designs. Unstructured grids are much easier to generate but require more complex and computationally expensive interpolation approaches to achieve similar levels of accuracy.
With Pointwise meshes and ADSCFD GPU accelerated CFD, simulation times are reduced by nearly 30X; reducing the turnaround time for a simulation that would take a month with traditional CPU technology down to a single day. This reduction in turnaround time enables such an analysis to be moved from something exotic and reserved for research to something useable for a designer within a typical commercial design cycle. The Pointwise capability to create hybrid unstructured grids, where surface boundaries can be meshed with a fully structured surface mesh but then combined with a fully unstructured volume mesh, gives the best of both worlds for these simulations: the speed and accuracy available to structured grid sliding mesh methods and the ease of mesh generation typically only available with fully unstructured grids.
AeroDynamice Solutions created a more detailed case study about the process. To download the PDF, click the download button below.
ADSCFD delivers aerospace-class CFD for the global turbomachinery industry. Built on the innovations of Ron-Ho Ni and rooted in decades of cutting edge aerospace application, the ADSCFD solution suite enables turbomachinery designers to tackle a wide range of compressor and turbine flow problems with confidence. The company is privately-held and headquartered in Danville, California. For more information, visit www.adscfd.com.
A challenge for compressor designers is management of tip clearance flow and its effect on stall margin. Novel casing treatments can increase operating range, however, cost and complexity of these methods prohibit their inclusion into the design cycle.
In collaboration with NASA GRC, ADSCFD applied the ADSCFD GPU accelerated flow solver to the challenge. With typical speedups of nearly 30X, effective casing treatment analysis now takes a few hours rather than weeks on traditional compute infrastructure.
With Pointwise meshes and ADSCFD GPU accelerated CFD, simulation times are reduced by nearly 30X; reducing the turnaround time for a simulation that would take a month with traditional CPU technology down to a single day.