Original Date: 04/26/1999
Revision Date: 01/18/2007
Best Practice : Unsteady Computational Fluid Dynamics Analysis of Turbines
Marshall Space Flight Center’s (MSFC’s) Fluid Dynamics Analysis Branch developed a process that utilizes Unsteady Computational Fluid Dynamic analysis during the design cycle of a turbine to quantify, reduce, and/or manage flowfield unsteadiness. Until the recent integration of current processing power, this process typically took place after a turbine was already designed. The motivation for changing the process included: the ability to achieve better designs, lower costs, and an improved overall understanding of turbine design; the added complexities of supersonic flow from current and future turbines (e.g., Fastrac, Reusable Launch Vehicle [RLV]); and the requirements for smaller, lightweight components which pushed turbines toward more compact, closely coupled designs magnifying the effects of flowfield unsteadiness.
The ability to accurately predict turbine flowfield unsteadiness in a timely manner is crucial to producing a design that meets a program’s objectives. Flowfield unsteadiness is a major factor in turbine performance and durability. Unsteadiness is particularly important for several classes of turbines including supersonic, compact, counter rotor, high work designs, and designs using dense drive gases. Most modern rocket engine turbines fall within these classes.
The requirements of the Fastrac program drove the real-time technology of Unsteady Computational Fluid Dynamic analysis in turbine engines. The objective was to demonstrate a reliable, low cost, turbopump-fed rocket engine using a reduced number of parts, a simpler design, a single stage with exit vanes, a supersonic flow, and commercial manufacturing techniques. To meet technical, cost, and schedule objectives of the Fastrac program, MSFC needed to run a series of Unsteady Computational Fluid Dynamic analyses during the design phase on various areas including coupled and uncoupled nozzles, blade configurations, and exit guide vanes.
By using the Unsteady Computational Fluid Dynamic analysis on the Fastrac program, MSFC completed its configuration calculations in approximately 14 weeks compared to the old method which would have taken about a year. Unsteady results supplied in a timely manner enable engineers to make real-time decisions that affect turbine performance. The ability to use Unsteady Computational Fluid Dynamic analysis during the design phase results in an increased understanding of the turbine flow environment, produces a better design, and reduces the amount of rework during maintenance schedules.
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