Question

Which of the following relations are correct for propeller advance ratio?

(a) J=\(\frac{TV}{nD}\)

(b) J=\(\frac{P}{nD}\)

(c) J=\(\frac{V}{nD}\)

(d) J=\(\frac{PV}{nD}\)

This question was posed to me in homework.

The query is from Power Producing Power Plant in division Aircraft Force Systems and the Equations of Motion of Aircraft Performance

Answer 1

Right option is (c) J=\(\frac{V}{nD}\)

For explanation I would say: The propeller efficiency depends on the propeller advance ratio and power coefficient. Propeller advance ratio is given by J=\(\frac{V}{nD}\) where J is propeller advance ratio, V is true airspeed, n is rotational speed and D is propeller diameter. Also the pressure coefficient is given by CP=\(\frac{P}{\frac{\rho n^3D^5}{2}}\) where CP is pressure coefficient, ρ is density, P is shaft power, n is rotational speed and D is propeller diameter.