Find the inlet area of a ramjet engine, if the maximum thrust to be produced is 5000\, N at sea level at an inlet velocity of 300\,m/s. The exit velocity, area and pressure are 650\,m/s, 0.08\,m^2 and 104000\,N/m^2.
Find the inlet area of a ramjet engine, if the maximum thrust to be produced is 5000\, N at sea level at an inlet velocity of 300\,m/s. The exit velocity, area and pressure are 650\,m/s, 0.08\,m^2 and 104000\,N/m^2.
Thrust produced by the engine is
T = \dot m\left( {{V_e} – {V_\infty }} \right) + \left( {{P_e} – {P_\infty }} \right){A_e}
\Rightarrow 5000 = \dot m\left( {650 – 300} \right) + \left( {104000 – 101325} \right)0.08
\Rightarrow \dot m = 13.7\,kg/s
and,
\dot m = {\rho _\infty }{V_\infty }{A_i}
\Rightarrow {13.7} = 1.225 \times 300 \times {A_i}
\Rightarrow {A_i} = \frac{{13.7}}{{367.5}} = 0.037{m^2}