Machine-translated by Google. Questions are authored in English.
Top

Discussion

At Mach 5 the same relation gives a ram pressure ratio of approximately

  • A.25
  • B.529
  • C.36.7
  • D.112

Answer: B

Correct answer: 529

For isentropic deceleration of air,

\[ \frac{p_0}{p} = \left(1 + \frac{\gamma-1}{2}M^2\right)^{\frac{\gamma}{\gamma-1}} = \left(1 + 0.2 \times 25\right)^{3.5} = 6^{3.5} \approx 529 \]

Ram compression alone therefore delivers a pressure ratio far beyond anything a mechanical compressor achieves, which is why a ramjet needs no rotating machinery at all. The corresponding stagnation temperature, however, is 1320 K from an ambient 220 K, and it is that figure rather than the pressure that sets the ramjet’s limit.

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.