Techsburg - News Archives - May, 2024

Techsburg to present at the 2024 Turbine Engine Technology Symposium Sep. 9-12 in Dayton, OH

Techsburg and Virginia Tech to present paper at 2024 ASME IGTI Turbo Expo June 24-28 in London, UK entitled "Flutter Parameter Study on a Complex Inlet Swirl Distortion Generator"

ABSTRACT: StreamVane devices consist of a custom designed complex vane pack that is used to produce inlet swirl distortion for fan tests, compressor tests, and ground testing of jet engines. Due to being placed upstream of these expensive test rigs, their structural integrity is very important. Since very little research has been conducted on flutter of complex vane packs like StreamVanes, this work focused on examining flutter of one of these models in more detail as well as studying the effects of various parameters on the critical flutter speed and frequency of these devices. For this study, a quad swirl StreamVane that was previously experimentally found to flutter was further analyzed using unsteady CFD with periodic mesh deformation based off the mode shape. This showed the flow in the passage between the fluttering vanes switching between a choked state and a subsonic state as the vanes moved together and apart from each other. This initial quad swirl model was then used as the basis for a series of small-scale flutter tests. These tests examined multiple parameters including chord length, vane thickness, blockage effects, and turning angle variation. To further analyze any potential causes of the excitation, oil flow visualization was conducted and found to show some leading-edge separation and minor corner separation but no pattern to indicate these flow features are responsible for the unsteady loading driving flutter. The results in this paper provide insight into the flutter behavior of these complex vane packs. 

Techsburg selected for a USAF Phase II SBIR contract entitled "Advancement of GPU-Accelerated Lattice-Boltzmann Method Simulations for Low Pressure Turbine Applications"

ABSTRACT: The aerodynamics of the Low-Pressure (LP) Turbines of High-Altitude Unmanned Air Systems (UAS) are dictated by the behavior of the transition bubble located on the suction surface of the turbine airfoils. Unfortunately, this phenomenon is difficult to predict with the Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) tools typically used in the design of LP Turbines. Scale-resolving simulations (SRS), such as Large Eddy Simulation-LES and Direct Numerical Simulation-DNS, offer a potential solution to this problem but the computational requirements of DNS are impractically high for use in the design cycle and even LES only becomes feasible when compromises are made to the grid topology that adversely affect the accuracy of the predictions. A potential solution is Graphical Processing Unit (GPU) based computing. GPUs offer improved computing capacity and memory bandwidth combined with smaller physical size and less electrical power draw than CPUs making them ideal for multi-node processing. While this option represents an evolutionary step in the design of LP turbines, Techburg is proposing to revolutionize the processes by combining GPU processing with the Scale-Resolving, Lattice-Boltzmann Method solver, PowerFLOW. In addition to the computational benefits of GPUs, PowerFLOW has been proven to be more than 50 times more computationally efficient than traditional Navier-Stokes LES, eliminating the need to make compromises in mesh topology. This combined solution yields a path toward to the ‘best of both worlds’ for SRS simulations; the physical accuracy of DNS coupled with the computational efficiency of LES. Early PowerFLOW simulations of LP turbine airfoil cascades by Techsburg have already proven this promise by accurately predicting both the total pressure losses and the behavior of the transition bubble, with simulations which require only hours on a single GPU.

Techsburg and Virginia Tech selected for a USAF Phase I STTR contract entitled “Dynamic ScreenVanes for the Generation of User-Prescribed, Time-Varying Inlet Distortion”

ABSTRACT: Next generation air platforms commonly incorporate embedded propulsion systems that can offer both aerodynamics benefits and reduced radar signature. These designs typically require compact offset diffusers that can generate non-uniform flow at the aerodynamic interface plane (AIP). Methods of evaluating the impact of the mean distortion patterns generated by these ducts on engine aeromechanics, performance, and operability have existed for many years. Distortion generating screens have been the industry standard for evaluating total pressure distortion effects in land-based engine tests for decades and more recently StreamVanesTM and ScreenVanesTM, developed by Virginia Tech, have improved the testing capabilities by generating swirl distortion as well as total pressure distortion. Despite these advancements, the need for further improvement remains. Both experiments and scale-resolved simulations of offset diffusers have shown that the resulting exit flow can not only be distorted but also highly unsteady. The impact of this unsteadiness on the engine is currently unknown and further research is necessary. To address this need, the team of Techsburg, Inc. and Virginia Tech are proposing the development of Dynamic ScreenVanes, an advancement on current ScreenVaneTM technology that will be able to produce both mean and time-varying components of fan face distortion. The proposing team will leverage its extensive experience in ScreenVaneTM design, flow control and unsteady aerodynamics to design and evaluate multiple passive and active approaches to adding the unsteady component to their existing distortion generating technology.