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April 2010
The Flow
CFD Insights for the Turbomachinery Designer

INSIGHT: Improving Durability through Accurate Metal Temperature Prediction
The need for high performance gas turbines with lower cost and weight has resulted in heavily loaded designs capable of operating at extremely high temperatures. This poses a great challenge for designers tasked with balancing performance with durability. In this month's issue of The Flow, we sit down with Bob Ni to discuss how recent advancements in CFD can enable designers to anticipate and mitigate thermal-related durability effects during the design cycle. Prior to founding ADS, Bob spent nearly 30 years at Pratt & Whitney leading turbomachinery CFD in support of compressor and turbine design.

FLOW: Bob, why is this such an important area for commercial turbomachinery designers?
BOB: Simply put, because turbomachinery makers can't compete on performance alone. If you design a gas turbine engine without regard to thermal loading effects, you run the risk of material fatigue failures that can cause operating costs to skyrocket and render a design non-competitive from the start.

FLOW: How is the issue being addressed today?
BOB: Thermal-related durability issues are being addressed in three ways: first, through the development of advanced materials/alloys better able to withstand high operating temperatures; second, through the use of techniques like film cooling to insulate blades/vanes from excessively high temperatures with a blanket of cooled air; third, through rig testing and predictive simulation to understand the distribution of thermal loads against different designs.

FLOW: How can CFD help?

BOB: As always, CFD-based simulation can save enormous amounts of time, cost and resource if the predictions consistently discern design improvements from mistakes and the analysis can be carried out in timely and cost-effective fashion. Unfortunately, several barriers exist today. First, generating a mesh for a design with hundreds if not thousands of cooling holes is a challenging and time consuming process. And even if you can successfully generate a mesh, the computational cost of conducting analysis against a mesh with tens of millions of elements can be equally as daunting. If it takes weeks for a solution to converge, it really makes it difficult to incorporate into a typical design cycle.

FLOW: How are you advancing the state of the art?
BOB: Fundamentally, the conjugate heat transfer capability we've created for our solver Code Leo integrates internal and external calculations into one tightly coupled computational procedure to accurately predict metal temperatures (and aero loads). At the front end, we've developed some scripts to automate many of the tedious tasks involved in generating the unstructured mesh, including the auto-tagging of surfaces. On the execution front, we've introduced some advanced parallelization features to enable CHT problems to be turned around in timeframes that are practical for typical design cycles. Finally, we've incorporated some interesting "fly by" visualization capabilities to enable designers to gain detailed insight into thermal loading and distribution.

FLOW: Is your conjugate heat transfer capability available now?
BOB: No. However, we are rolling out an OEM evaluation program that will provide early access to selected design partners prior to commercial release of our capabilities in 2011. The evaluation program is slated to commence in the second half of 2010 and provides participants the opportunity to exercise our capabilities at no cost in return for evaluation, feedback and attribution. For more information, please see related article on the OEM Evaluation Program in this newsletter.
FLOW: Thanks, Bob.
BOB: My pleasure.

CASE STUDY: Predicting Aero and Thermal Loads with Code Leo
As part of an SBIR Phase II grant with the U.S. Air Force Research Laboratory, ADS has developed conjugate heat transfer analysis capability to enable accurate prediction of aero and thermal loads in a film cooled turbine vane. In this video presentation, ADS chairman and CTO Bob Ni provides a quick overview of the ADS solver Code Leo and a preview of how it is being applied to gain insight to aero and thermal loading. <more>

NEWS: ADS Unveils OEM Evaluation Program

With a year of development and testing complete, we are now ready to work with qualified commercial design partners to evaluate and provide feedback on our conjugate heat transfer and full wheel unsteady analysis capabilities. <more>

Welcome to The Flow

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Welcome to The Flow, a newsletter for monthly insights on turbomachinery CFD published by AeroDynamic Solutions, Inc.

Each month we'll spotlight a topic of interest, discuss a case study and/or provide useful pointers about how to get the most out of the ADS CFD system.

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