In an earlier problem we considered the GE90 engine, one of the world's most powerful engines.

Question

It was already determined that the jet velocity of this engine is 376 metres per second. Suppose that this Boeing 777 flies at 11 kilometres at M=0.82, what is then the jet efficiency of this engine (in percent)? Do not include the % sign in your answer.

Answer 1

To find the jet efficiency of the GE90 engine, we need to use the formula for jet efficiency:

jet efficiency = (jet velocity / flight velocity) x 100

First, we need to convert the flight velocity from kilometers per hour to meters per second:

11 kilometers = 11,000 meters (since there are 1000 meters in one kilometer)
11,000 meters / 3600 seconds = 3.055 meters per second (approx.)

Next, we need to calculate the flight velocity at M=0.82 using the equation:

flight velocity = speed of sound x Mach number

The speed of sound at sea level is approximately 340 meters per second.

flight velocity = 340 meters per second x 0.82
flight velocity = 278.8 meters per second (approx.)

Finally, we can calculate the jet efficiency:

jet efficiency = (jet velocity / flight velocity) x 100
jet efficiency = (376 meters per second / 278.8 meters per second) x 100
jet efficiency = 134.93

The jet efficiency of the GE90 engine is approximately 134.93%.