A droplet of balm for the "green power" fans

[mrfox]

On 4/24/2021 at 11:15 PM, wumpus said:

 

[note, I still don't know why 30hp turbines are inefficient.  I'm an electrical type, and only dealt with thermo in "physics for engineers", not a separate class]

In a later post you referred to the “BSHP island” for reciprocating piston engines. In a gas turbine (or any turbine really) this island is absolutely minuscule in comparison - basically, anything other than near max rated power at close to max rated RPM - efficiency falls off a cliff. This is because while the compression ratio and efficiency is mechanically fixed (and independent of RPM) in Otto/diesel cycle engines,  it is highly variable with RPM in a gas turbine/brayton cycle engine - the spinning compressor absolutely depends on being at high RPM to achieve anything near design compression.  Just look at an idling gas turbine’s fuel consumption - it is horrendous in comparison to a piston engine.

And turbines also take forever to spin up - so its not like you can just shut the turbine off Willy nilly like a piston engine to avoid idling either.

 

 

 

Edited April 27, 2021 by mrfox