Blower fitted with De Laval Nozzle

[T C]

The question is efficiency.

If the recovery is 75%, do you consider that efficient or not.

 

[cjl]

Depends on the mach number. As Boneh3ad said earlier, efficient pressure recovery becomes more difficult with increasing mach number, so 90%+ is trivial at a bit over mach 1, but even 75% would be incredibly difficult when hypersonic.

 

[boneh3ad]

If the recovery is 75%, do you consider that efficient or not.

I think you need to study gas dynamics a bit because it is clear from your questions that you are not familiar with the topic and it is making this very difficult to discuss.

Any supersonic flow that started at atmospheric pressure must, at some point, be slowed back down to reach atmospheric pressure. If no diffuser is used, a normal shock typically forms and causes a certain amount of total pressure loss. By fitting various forms of diffuser geometries to the outlet of such a device, we can try to improve upon the performance of a normal shock with varying degrees of success. Therefore, diffuser efficiency is typically measured by comparing it with the efficiency of a normal shock since the pressure recovery is highly dependent on Mach number.

So, if you are asking whether 75% pressure recovery is good, I'd go back to the answer I gave you last time you asked that. That would be pretty great if you had a Mach 5 flow, pretty trivial if you had a Mach 2 flow, and you really just made things worse if you have a Mach 1.5 flow.