Intake Fan LPC IPC HPC Combustion chamber HPT LPT Nozzle 10

Intake Fan (LPC) IPC HPC Combustion chamber HPT LPT Nozzle 10, cj (cold jet) lliv 567 89.hj (hot jet) Figure 14.55

Solution

This is a problem from T.A. Wards book.   

The basic eqns are T = (m\'air+m\'fuel) Vj - m\'air V inf + (pe-pinf) Ae

The pressure terms is usually neglected.

The TSFC is given by an empirical formula TSFC= 1.0+kM

The ratio of Vj/Vinf can be found from efficiency = 2/[ 1+ Vj/Vinf]

Taking the value of 0.8 Vj/Vinf = 1.5

Mass flow rate m\' air needs to be estimated along with m\'fuel. These are found from formulae in Ward or Mattingly, and need a compute program. I can only give basic steps. Or you may use graphs given in the texts.

TO FACTOR THE BPR of 6: Bypass changes the TSFC and reduces it but it is not linear.

Acording to CUMPSTY for a BPR of 5 (RB211) the effect was 8%.

Best