Model tests on an air interchange system for removing engine exhaust products from a wind tunnel

Abstract

Model tests have been made to investigate the functioning of an air interchange system for removing from a return-circuit wind tunnel a high proportion of the exhaust products from propulsive units under test. The tests were planned to assist the design of an engine altitude tunnel. With changing circumstances the priority of this tunnel has been reduced, but the tests were continued to give general information on the extraction of engine exhaust products from this type of wind tunnel. The tests were made on a partial model of a tunnel, which had an air interchange exhaust collector designed to remove 15 per cent of the tunnel mass flow. This was installed on the tunnel axis at the downstream end of the working section. Tests were also made on 10 per cent and 5 per cent collector entries designed to be interchangeable with the 15 per cent entry. The tests have confirmed that the interchange system tested was generally very satisfactory for the specified requirements, and that in the interests of power economy, the interchange ratio should be reduced as far as possible. In other tunnels with less exacting requirements the collector duct would of course be placed in a region where the wind speed was low, in order to reduce the losses and hence the fan power.