As usual with Dave there is a bit of cross selling going on. Invisible will say "but gotta make a paycheck." Ok, thanks. Onto interesting stuff:
After a little amateur googling, found this government study by Sandia National Labs.
Conclusions excerpt
"
Conclusions
An improved dimple stepped-lip (DSL) piston was designed using computational fluid dynamics, which enhances vortex formation at near-top dead center (TDC) injection timings. This DSL piston was fabricated and evaluated experimentally at the Sandia Off-Road Diesel Research Engine Facility, and the engine performance was compared to that obtained with a production stepped-lip (SL) piston. For early injection timings at a part-load operating condition, the DSL piston leads to 0.5% higher thermal efficiency, 45% less soot, 17% less unburned HC emissions, and 20% less CO emissions than the SL piston, with a small penalty on NOx emissions. The marginal improvement in efficiency is caused by a competition between faster mixing-controlled HRR, which tends to increase the efficiency, and increased wall heat transfer losses in the DSL piston by 2.7% relative to the SL piston at the early injection timing. At low-load operation, thermal efficiency is reduced as wall heat transfer losses are increased by 1.8%, with higher CO and unburned HC emissions, lower NOx, and 45% lower soot. As injection timing is retarded, any efficiency or soot emissions benefits are reduced.
This study shows that vortex enhancement may not necessarily lead to improved thermal efficiency as it can cause increased wall heat transfer losses due to higher convection in the squish region and cylinder head. Vortex enhancement is demonstrated to be a very effective mechanism to reduce soot emissions due to better air utilization and soot oxidation. However, the dimple geometry can affect swirl intensity, which could affect the soot reduction mechanism. Future design optimization of the DSL piston will need to balance vortex enhancement and wall heat transfer losses in order to further improve thermal efficiency and reduce soot emissions. Moreover, this study also shows that benefits obtained at early injection timings do not necessarily continue at late injection timings. Thus, both late- and early-injection conditions should be included in future piston geometry optimization studies. Combustion simulations will also be performed to improve our understanding of where and when emission species are formed, and how heat transfer is distributed over the piston surface."
My take:
It looks like pistons are already for sale, ranging from $1700-3k+. It would be interesting to see a real life application, and results from someone who has the budget. Speed of Air themselves are trying, the video gets interesting about 24 minutes in. I'm delving into big diesel engines myself eventually but aint got that kind of scratch or use case.
