Simulation tools offer insight into the physical processes of heavy-duty engines. With the help of computational fluid dynamics (CFD) software, for example, a design engineer can better understand how fuel is moving from the injector and increasing emissions.
Numerical simulations also easily show the effects of design changes.
But how well can CFD software simulate the natural wear and tear on an engine?
In a live webcast last week titled “Heavy-Duty Engine Design,” a Tech Briefs reader asked Dr. Sameera Wijeyakulasuriya, Principal Engineer at the Madison, WI-based CFD software company Convergent Science:
“How common is it to simulate normal wear and tear of engine components — several times during development or just at the end? Might wear on the fuel injector needle and piston ring greatly reduce performance?”
The edited response from Wijeyakulasuriya is below.
Dr. Sameera Wijeyakulasuriya, Principal Engineer: Typically, when using CFD and comparing that against data, we oftentimes take geometries of CFD from CAD drawings. We seldomly get information from the actual engine, where wear and tear has already been taken into account and has happened – and the data is biased toward that.
For example, piston rings that have worn off will give rise to mass-loss from the cylinders. Often times what we do is get better data for CFD. If you know that there are parameters that can change from the CAD data, you want to use your best estimate, or do a sensitivity analysis. That’s the best way to go.
It’s impossible in CFD to run thousands of cycles. CFD is bounded by boundary conditions. You’re not going to see wear and tear being taken into account in CFD as you run cycle after cycle. It’s futuristic. We’re not there yet, but I think knowing how an engine is worn and how long it has run — and getting to scan actual geometries from the engine — can help us predict things much better.
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