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Cast iron in Roger's engine. Mine, aluminium.

Heh, would have been nice to have more direct evidence on that front. I've seen some papers where they painted the piston with something fuel soluble and after running a few cycles inspect to see where the paint washed off. Might be one way to attack that question.

Roger, With your design I wonder how much fuel gets sprayed onto the piston surface. Have you had the head off and inspected since getting a good amount of run time on the engine? Curious if there is evidence of this like a fuel washed patch in the bowl.

Technically everything is soluble in everything else at some vanishingly small concentration. But the severity of the galvanic effect inside a crankcase is minor as evidenced by the fact that aluminium pistons do not typically get destroyed by galvanic corrosion inside an iron cylinder block...

To have electrolytic corrosion you need two dissimilar metals electrically connected to each other and in contact with an electrolyte. Oil isn't conductive so the latter does not apply, no electrolytic corrosion should occur unless the oil somehow gets contaminated with lots of water. In marine...

In my experience copper and its alloys have a habit of reacting with vegetable oils and biodiesel over time. You get a film of greenish sludge building up on the parts. Better to use stainless steel, or regular steel where it isn't suitable. Anyway using fuel as coolant is possible, in fact...

Giving this some more thought, what about silicone oils? They have very good thermal stability and the heat transfer properties seem similar to those of mineral oils. This of course assumes one does not simply use the sump oil as coolant as well. Based on their specific heat capacities, it...

The opposite of a nozzle is a diffuser. For radial flow machines there are two types, vaneless and vaned. Vaneless is just a smooth annular space around the rotor, fluid spirals out and decelerates due to conservation of angular momentum. Vaned type uses diverging passages to catch and slow the...

If the compressor efficiency is similar to the pump efficiency in that paper (about 30%) you might even need an aftercooler, as the air exiting the compressor will get rather hot. Kind of business as usual for air compressors, even the reciprocating ones need fins.

As a result of ongoing discussions, I've been working on a steam turbine design spreadsheet. This is the latest (probably final, for now) model. New features compared to the Mk II version posted on the tesla turbine thread: Condensation within the turbine is now considered, and a target exit...

This is the same as the velocity compounding in my spreadsheet if you want to play with it. I've made an updated 'final' version, but I think I'll post about it in a new thread so we don't keep clogging this one with non tesla turbine stuff.

My concern with oil water emulsion would be the tendency for bacteria to grow in it if left for a long time. Though I have had some success preventing this by putting bits of copper scrap in the container.

I see no reason it cannot be done. Though I unsure what oil would be the best choice.

I think the uni of Melbourne had a big one to drive fusion experiments. Big current at low voltage. Edit: I misremembered, it was ANU that had one. On the topic of high rpm generators to go with turbines, another option is a flux switching alternator. They're used as electrical generators...

I think the ideal is for the flow in the active sector to be as contiguous as possible, so ideally you would make one single nozzle sized to your flow rate if you are using partial admission. There are lots of reasons not to do that however. For example having multiple nozzles allows you to...

I decided to take Roger's advice and grind the grooves in after heat treatment. Here's my setup, I just put a dremel cut-off wheel and arbor in my milling collet. Worked pretty well. I covered my ways with rags before grinding, the abrasive dust is not good for them. My mill only does 1100 rpm...

Toymaker, I've been reading up on something else that will be of relevance, especially if you build a mk II turbine. That something is the partial admission losses. The gist of it is that in any gas turbine the ideal flow only happens if the fluid is injected uniformly around the rotor...

The gas is introduced tangentially at high velocity, so it ends up.spinning in the casing. Ever spun on an office chair and noticed that if you pull your legs in you start spinning faster? That's conservation of angular momentum. The same applies to gas flows, the net effect is that the flow...

The best diesels just surpass 50% thermal efficiency. Supercritical steam slightly less than this, up to 48%. Of course one can do better than either by using an ICE's exhaust to heat the boiler of a steam engine, like many gas fired plants. Overall efficiency of more than 60% is possible that...

Internal combustion has a big unfair advantage over steam, it gets to just use the hot gas at the combustion temperature rather than a temperature that the boiler can withstand. As per Carnot the temperature drop across the engine directly correlates with efficiency, so it's very hard for a...