Um, yeah, you need to scroll down the page a bit to the images and video of it.

They did some weird editing in the video of it I watched, so it is a bit hard to see just what the flash was.
If you can get it to ignite a bit of tinder for them (fairly) regularly, then you will have done well and given them a good demonstration about heat by compression.

Then presto, suddenly they know how a diesel motor works.