Question

Specific fuel consumption (SFC) projects the fuel economy of an engine, that is, it measures the fuel flow rate (say in pound-mass per hour or g/s) that leads to a production of a unit thrust (say 1 pound-force or 1 Newton). Two sets of numbers are copied from Table 1.1 (from EJ200 specification), which are:

SFC (max.power) SFC w/AB Thrust (SL) Thrust w/AB
0.81 lbm/h/lbf
1.75 lbm/h/lbf
13,500 lbf 20,250-22,250 lbf
First note that afterburner (AB) use more than doubles the fuel consumption while boosting the thrust by only ~50%. This explains the sparse use of an afterburner in aircraft missions. Now to quantify, calculate the amount of additional fuel burned in 30 min of afterburner use (producing 21,000 lbf thrust) as compared with 30 min of no afterburner use (producing 13,500 lbf thrust).

Answer 1

To calculate the additional fuel burned in 30 minutes of afterburner use compared to 30 minutes of no afterburner use, we need to determine the difference in fuel consumption for each scenario. The specific fuel consumption with afterburner use is 1.75 lbm/h/lbf and the specific fuel consumption without afterburner use is 0.81 lbm/h/lbf. By subtracting the fuel burned without afterburner use from the fuel burned with afterburner use, we find that the additional fuel burned in 30 minutes of afterburner use is 25,815 lbm/h.

Step-by-step explanation:

To calculate the additional fuel burned in 30 minutes of afterburner use compared to 30 minutes of no afterburner use, we need to determine the difference in fuel consumption for each scenario.

1. To calculate the fuel burned with afterburner use, we can use the specific fuel consumption (SFC) of the engine, which is 1.75 lbm/h/lbf. The thrust with afterburner use is 21,000 lbf, so the fuel flow rate is 1.75 lbm/h/lbf x 21,000 lbf = 36,750 lbm/h.
2. Next, we need to calculate the fuel burned without afterburner use. The specific fuel consumption without afterburner use is 0.81 lbm/h/lbf. The thrust without afterburner use is 13,500 lbf, so the fuel flow rate is 0.81 lbm/h/lbf x 13,500 lbf = 10,935 lbm/h.
3. Finally, we can calculate the additional fuel burned by subtracting the fuel burned without afterburner use from the fuel burned with afterburner use: 36,750 lbm/h - 10,935 lbm/h = 25,815 lbm/h.

Therefore, the additional fuel burned in 30 minutes of afterburner use compared to 30 minutes of no afterburner use is 25,815 lbm/h.