Project Highlights

Gas Flow in a Metal 3D Printer

The Problem: Poor Performance + Limited Understanding

Laser Powder Bed Fusion (PBF-LB/M) systems rely on a constant flow of inert gas to protect the metal powder from oxidation and sweep away byproducts such as smoke and spatter. With a complex geometry and highly three-dimensional flow field, understanding the flow patterns is difficult. This limits the value of single-point measurements and leads to an over-reliance on simulation.

The Solution: Magnetic Resonance Velocimetry

A scale model and a commercial MRI system are all that's needed to obtain the full 3D velocity field. This allows designers to see the big picture - where the flow goes and why.

Armed with this information, designers can:

Reduce flow-related losses, allowing for higher flow rates with the same size pump
Improve inlet & outlet geometries to better protect critical areas of the build chamber
Get better in-situ data through smarter placement of probes & cameras

Fully Quantitative

MRV datasets aren't just useful for creating striking 2D and 3D images. The underlying data are suitable for rigorous quantitative analysis, with a typical noise level around 3% of the full dynamic range. In the example above, a key velocity profile is compared for three flow configurations under study.

Fully Three Dimensional

When dealing with a complex, three-dimensional flow, how do you know where to look? Enter MRV. A fully 3D dataset lets you slice and dice interactively. Here, an important slice of data just above the build surface is shown. The important point is that the slice location was determined from the same dataset - no need for repeat measurements or re-alignment.

Film Cooling Under Unsteady Flow

The Problem: Real-World vs. Ideal Conditions

Film cooling is an integral part of modern turbine engines. By coating the surface of turbine blades and vanes with cooler bypass air, combustion temperatures can be increased and efficiency gained. For this to work, accurate knowledge of how well the surfaces are protected is essential - even under realistic conditions including the passage of upstream wakes.

Oliver Cleynen via CC License

The Solution: Phase-Locked (Unsteady) MRI

MRI flow measurements are designed to work in the presence of motion - especially the cardiac cycle. By leveraging this capability, we can produce phase-locked measurements that reveal variations in velocity, temperature, or other scalar concentration across a periodic flow. In addition, single-plane snapshots are obtainable with ~20 millisecond resolution. This technology allowed us to compare the performance of two hole geometries under both idealized and realistic conditions.

Real-World Meaning

A design that looks better under ideal conditions may not hold up well when placed in service. In this study, unsteadiness in the free stream caused a significant reduction in the ability of bypass air to coat the surface when fed through the shaped-hole geometry. If not identified early, this type of effect can lead to a dramatic reduction in service life (and ROI).

Smarter Choices

While the shaped-hole design was heavily impacted, MRI revealed that the simpler round-hole design was more robust. Film cooling effectiveness was minimally impacted by free stream unsteadiness - shown quantitatively by the MRI data.

Publications & Visualizations

Elkins, C. J., et al. (2023). Resolving the three-dimensional flow field within commercial metal additive manufacturing machines: Application of experimental Magnetic Resonance Velocimetry. Additive Manufacturing. doi.org/10.1016/j.addma.2023.103651Borup, D. D., , et al. (2019). Experimental study of periodic free stream unsteadiness effects on discrete hole film cooling in two geometries. Journal of Turbomachinery. doi.org/10.1115/1.4041866Hoffman, D. W., et al. (2020). Experimental study of flow inside a centrifugal fan using magnetic resonance velocimetry. Journal of Engineering for Gas Turbines and Power. doi.org/10.1115/1.4045064

Page updated

Report abuse