2
$\begingroup$

Here is an example of a bypass ratio 9:6:1. 9kg goes around the core and 6kg goes into the core, but what is the 1 for.

$\endgroup$
  • $\begingroup$ By the way this is the bypass ratio for the General Electric GEnx-1B engines on the 787 Dreamliner. $\endgroup$ – Ethan Sep 4 '15 at 22:49
6
$\begingroup$

The bypass ratio of a turbofan engine is the ratio of the mass flow rate of the air that bypasses the engine core (i.e. it doesn't undergo combustion),$\dot{m_{f}}$ to the mass flow rate of the air that passes through the core $\dot{m_{c}}$ and undergoes combustion.

The bypass ratio is usually given as the mass flow of fan by the mass flow of core i.e. $\frac{\dot{m{f}}}{\dot{m_{c}}}:1$. In some cases, it is given as the ratio of cold air to hot air, $\frac{\dot{m{c}}}{\dot{m_{h}}}:1$.

Bypass Ratio

So, a bypass ratio of 9.6:1 means that 9.6 kg of air passes through the bypass fan for every 1 kg of air passing through the core.

$\endgroup$
10
$\begingroup$

It is 9.6:1 not 9:6:1.

9.6 parts air are bypassed for each part that goes through the core.

$\endgroup$
  • $\begingroup$ That makes more sense $\endgroup$ – Ethan Sep 4 '15 at 23:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.