An altitude-chamber investigation of British Rolls-Royce Nene II turbojet engine was conducted over range of altitudes from sea level to 65,000 feet and ram pressure ratios from 1.10 to 3.50, using an 18.00-inch-diameter jet nozzle. The 18.00-inch-diameter jet nozzle gave slightly lower values of net-thrust specific fuel consumption than either the 18.41- or the standard 18.75-inch-diameter jet nozzles at high flight speeds. At low flight speeds, the 18.41-inch-diameter jet nozzle gave the lowest value of net-thrust specific fuel consumption.

"A complete stage of an axial-flow compressor designed to produce a high pressure ratio was investigated at speeds from 110 to 130 percent of design speed (836 ft/sec). The data obtained and the results of a previous investigation of the same compressor at speeds from 50 to 100 percent of design speed were used to determine the effect of Mach number on over-all performance. The peak total-pressure ratio increased from 1.095 to 1.515 and the peak adiabatic efficiency decreased from 0.93 to 0.89 as the relative inlet Mach number increased from 0.34 to 0.77. At a relative inlet Mach number of 0.91, a total-pressure ratio of 1.635 was obtained at an adiabatic efficiency of 0.74" (p. 1).

The use of inlet guide vanes with the 24-inch supersonic compressor resulted in a decrease in maximum pressure ratio and adiabatic efficiency, and a slight increase in equivalent mass flow. The loss in total pressure and efficiency resulted from reduced diffusion in the rotor-blade passages, increased shock losses at the higher entrance Mach number, and increased mixing separation, and transfer of mass flow toward the rotor hub. The unsteady flow field created at the compressor entrance by the guide-vane wakes is also responsible for some of the losses. This inherent loss will be encountered whenever inlet guide vanes are used with the shock-in-rotor type of supersonic compressor.