Quote from: AlexSI got +- equal outcome of 260 W shaft power, and 345 W cooling heat. For a 5:1 static CR (compression ratio) and 3.9:1 dynamic CR.
Compression ratio (so BMEP) and displacement is quit low. Would it needed cooling flow for 5 minutes test runs? or is your plan to run 30 minutes?
The idea Minh is interesting for one "blind barrel" cylinder head and cylinder in 1. Maybe option to SLM aluminium 3d printing. Option to add cooling volumes in cylinder head connected to cylinder. Minimum wall thickness for printing is 1mm. Also option for wetted or dry cast iron liner. Only need machining valve cages/stem guides from outside with fine threaded connection with loctite.
I'm targeting my CR to be ~7:1 on paper knowing that is has a habit of creeping lower in real life with nooks & crannies here & there, likely end up at say 6.5:1. The head volume is amazingly sensitive. My intent is to run methanol based fuel (for various reasons) but spark ignition with timing advance/retard. I think it should reliably bench putt-putt at 6:1 CR with spark igntion, maybe even lower, but I dont have a lot of data there. Higher CR doesnt really achieve much if power is not the objective. Minimum CR of 7:1 is a requirement for glow plug ignition methanol engines, 8+ is probably more the norm. But my own experience has been an engine that has a nice bounce usually starts & runs & behaves better. The opposite = less so. So yeah, typical bench run demos & meetups are 5 min, up & down the power range, lots of idleing because its easier on the ears. Then let the smoke clear, engine cool down & thats success in my books. At least, I have no plans to fly it if thats what you mean.
The 3DP metal print is an interesting notion. I was thinking about the cylinder water jacket area, but the head could benefit from its print capabilties even more. Especially with no vertical hold down bolt holes to work around. Something more like the FS engine 'shell'. My simple through hole coolant passage is easy to machine but I suspect not very effective. I guess if one were brave & designed it with minimum shell thickness around valve cages, ports etc (maybe what you are alluding to) it could be 3DP stainless or something similar vs aluminum. The extra liquid cooling would probably more than make up for difference between aluminum & steel. I think I need to print one in PLA to hold in my hand.
