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,
\[\dot m = {\rho _\infty }{V_\infty }{A_i}\]
\[ \Rightarrow {13.7} = 1.225 \times 300 \times {A_i}\]
\[ \Rightarrow {A_i} = \frac{{13.7}}{{367.5}} = 0.037{m^2}\]
