Experimental investigation of air flow in rotating blade rows is widely regarded as desirable, but is rendered difficult in practice because of high rotational speeds and the large number of pressure tappings required. The design and operation of a system using the Scanivalve and able to transmit pressures from a rotor running at 8000 rev/min is described in this paper. Some experience in the use of the system with blade surface measurements on a small (8-in diameter) centrifugal impeller is discussed. Attention is paid to sources of error in pressure readings, including the rotating head correction to convert the transmitted pressure reading into actual pressure at the point of measurement. Theoretical relative velocities in the impeller have also been obtained with Algol computer programmes for isentropic flow in the axi-symmetric and blade-to-blade directions. A comparison is made between experimental and theoretical relative velocities in the impeller in which the flow is essentially incompressible at the test speed. It is concluded that flow separation occurs early in this particular impeller channel. On the evidence of the results obtained so far, some further uses and developments of the pressure transmission system are discussed.
An experimental investigation on the dynamic glaze ice accretion process over a wind turbine airfoil surface
