Air flow vs density

[TheRealMRDyno]

Hi,

Does anybody out there know the relationship between air density and the flow restriction imposed by some pipe/path?

Here is my issue - flow restriction generates a pressure drop = bad.

The pressure drop is a function, mostly, I think, of velocity.

So, since an engine is going to flow the same volume, regardless of boost pressure, at xxxx RPM, the volumetric flow rate is the same, and the velocity is the same.

But, the density is different - which leads to my initial question.

If density does not play into the pressure drop, and the existing pipe/path is large enough at <current_boost>, then there is no reason to use larger pipe/path when running at <more_boost>.

Thanks,
Joe

 

[pboglio]

Density does play a factor in pressure losses. Ultimately anything that increases the flow velocity in the piping will typically increase flow losses. A temperature difference will do this, so will a pipe cross sectional change, pipe length increase, restrictive bends, or increased wall roughness.

Anywhere the air is cold and the piping is big, the flow losses are going to be small. Anywhere the air is hot and the piping is small, the flow losses are going to be bigger.

 

[Bill Hincher]

every pilot must understand the relationship between air temp and air density, you can find very detailed charts that give you exact numbers at any flying outlet