Correction of ramjet experimental data

Heat energy can be converted into mechanical energy only by the expansion of a high temperature high pressure gas to a lower pressure thus changing the random energy, temperature, into a directed energy associated with a velocity. One of the simplest methods of achieving the necessary pressure for this expansion is by utilizing the high velocity of the airstream relative to a rapidly moving aircraft. The momentum of this airstream is converted into pressure by deceleration in a diffuser. The air is then heated and ejected as a high speed jet, producing thrust, hence the name given to this system is ramjet. Other names have also been proposed such as athodyd, which is a contraction of aero-thermodynamic duct. The purpose of this study is to derive a simple ramjet theory and to use this theory in setting up dimensionless parameters and methods of analysing experimental data. No attempt is made to devise experimental techniques but only to give a method by which the experimental data may be correlated. It is found that the performance of a ramjet at any altitude can be reduced to an equivalent sea level condition by the application of suitable correction factors. These factors are derived on the basis of constant flight Mach number, constant ramjet geometrical arrangement, and constant throttle setting. This latter parameter is most accurately described by the ratio of the combustion chamber temperature to the free air temperature. It is recommended that ramjet test data be corrected to this standard sea level condition for ease of correlation and analysis