Ingersoll Rand Energy Systems Improves Microturbine Using EFD Flow Simulation Software
Ingersoll Rand Energy Systems has improved the plenum manufacturing process of the MT250 microturbine engine by using the EFD family of computational fluid dynamics (CFD) software from Flomerics to develop a simple design that outperforms the earlier more complex design. In the past, evaluating new designs required expensive rig testing which made it impractical to evaluate a wide range of alternatives. "With EFD software, on the other hand, we were able to evaluate 15 different alternatives very quickly and without cutting any metal," said Toni Stamenov, Design Engineer for Ingersoll Rand Energy Systems. "One of them provides the same performance as the previous design even though it is much less expensive to make because it does not require hydroforming."
The MT250 microturbine is a rugged 250 kilowatt turbine engine with back-to-back rotating components, a patented recuperator and a patented combustor that meets stringent environmental regulations. The plenum receives outside air and delivers it to the compressor section of the engine. The plenum has to deliver air to the engine while maintaining an even velocity profile across its cross-section, minimizing pressure drop, and staying within limits set by other parts of the engine. When engineers originally designed the MT250 plenum they met these objectives by using a design with a rather complex geometry that had to be hydroformed, which substantially raised manufacturing costs.
After the engine was introduced, Stamenov headed up a project to reduce the costs of manufacturing the plenum. His objective was to develop a new design that provided equal performance while being less expensive to build. "It would not have been practical to undertake this project using the original build-and-test method because it would have cost too much and taken too long to evaluate each new design," Stamenov said. "But EFD software gives us the opportunity to evaluate designs in much less time." FloEFD.Pro, the version Stamenov now uses, works inside Pro/ENGINEER computer aided design (CAD) software and automates the process of converting CAD models into CFD models for flow simulation.
Stamenov first modeled the original geometry and the flow simulation results matched the test results on the original design within 1%. Then he evaluated new designs by changing the geometry that was making the part expensive to manufacture. He evaluated 15 different designs, developing each design based on the analysis results from the previous design. The CFD results were considerably more useful than test results since they include not only bulk measurements such as pressure drop and velocity but also values that are impractical to measure physically such as velocity and pressure of the airflow at every point in the plenum.
Stamenov developed a design that offers lower pressure drop than the original plenum design, which improves compressor efficiency. Yet this design has simple shapes and can be easily built by any machine shop without expensive equipment making it less expensive to manufacture than the original. The new design also improves assembly and serviceability by reducing installation time from 1 hour to 10 minutes. Stamenov ordered a prototype of the new design and tested it on a rig. Again, the results matched the simulation within about 1%. "The new design was put into production only months after starting the evaluations," Stamenov concluded.
Interested readers may download their choice of free EFD online demos at http://energy.ingersollrand.com