I was reminded just how complicated and expensive it is to develop a jet engine when I came across a video describing GE’s recent $26 million Cdn investment to upgrade its Winnipeg test facility. That is on top of even bigger investments by Rolls-Royce ($50 million) and GE ($40 million) and in recent years. Physical testing is not only expensive, it is time consuming and can lengthen design cycles.
Meanwhile, it has become easier than ever to simulate engine performance prior to any physical testing. Improved techniques like harmonic analysis, turbomachinery-specific workflows and better validation coupled with faster, more capable high performance & cloud computing are quickly expanding simulation so engineers can be confident in their designs before the first prototype is ever built. While physical testing is not going away anytime soon, ANSYS is working on digital prototyping with leading turbomachinery companies and helping them to cut it down to size. Continue reading →
Transient blade row simulations in turbomachinery are needed either to improve the aerodynamic performance predictions or because the flow interaction we are trying to resolve and predict is unsteady in nature such as aeromechanical, aerothermodynamic or aeroacoustic interactions. Because the blade pitch is not similar between the rows of turbine or compressor, a transient blade row simulation will usually require the modeling of the full wheel (or full geometry). This constraint renders these simulations not practical and in many cases prohibitive as analysis or design tools.Continue reading →
As the year winds down, I thought I’d share some of the most read ANSYS blog posts of 2015 with you. From harmonic analysis to how germs spread when you sneeze, I hope you’ll find these choices as interesting as I did.
SPOILER ALERT: We have some REALLY cool stuff coming in 2016 that you won’t want to miss! If you haven’t subscribed to the ANSYS blog yet, please make sure you do that now.
Harmonic analysis is a technique used to determine the steady-state response of linear structures to loads that vary sinusoidally (harmonically) with time. In harmonic analysis, the entire structure has constant or frequency-dependent stiffness, damping and mass effects. The structure’s response at several frequencies is calculated to obtain a graph of some response quantity (usually displacements) versus frequency. Thereafter, peak responses are identified and stresses reviewed at those peak frequencies.
Harmonic analysis can be solved either using full harmonic or mode-superposition techniques each with advantages and disadvantages as shown here.
The Full Method
The Mode-Superposition Method
Easy to use.
Uses full matrices [K, M and C].
Allows unsymmetric matrices.
Calculates all displacements and stresses in a single pass.
Accepts all types of loads: nodal forces, imposed (nonzero) displacements and element loads (pressures and temperatures).
Allows effective use of solid-model loads.
More expensive than either of the other methods when you use the sparse solver.
Faster and less expensive than either the reduced or the full method for many problems.
Element loads applied in the preceding modal analysis can be applied in the harmonic analysis via the LVSCALE command.
Allows solutions to be clustered about the structure’s natural frequencies.
Prestressing effects can be included.
It accepts modal damping (damping ratio as a function of frequency).
Imposed (nonzero) displacements cannot be applied.