The Design and Construction of the Compressor for the 8 ft by 8 ft High-Speed Wind Tunnel at R.A.E. Bedford

The paper, which is in two parts, deals with the steps taken to meet the specified performance and conditions of operation of the compressor for the 8 ft x 8 ft high-speed wind tunnel at Royal Aircraft Establishment (R.A.E.) Bedford.

The essential requirements were that the compressor should deliver a quantity differing not greatly from 50 000 ft³/s over a range of pressure ratio 1.15 to 2.50, an important proviso being that special steps must be taken to achieve high efficiencies in the lower range of pressure ratios.

Part I deals with the reasoning which led to the adoption of the final design solutions, and the supporting experimental work including the manufacture and testing of a 1/7 scale aerodynamic model necessary to establish the performance characteristics of the compressor before deciding the final blade settings. It was decided to build a ten-stage compressor to run at 750 rev/min having a first-stage blade tip diameter of 17 ft with a blade 2 ft 6 in. long. In order to meet the requirement of good efficiency over the whole working range, the compressor was divided into two parts so that under low pressure ratio conditions only the first four stages are in the circuit, the change from 10 stage to 4 stage operation and vice versa taking place in under twenty minutes.

Part II describes the mechanical features and manufacturing processes following from the design decisions given in Part I.