Nomogram Analysis for Ducted Fans with Pre‐rotation: A Method Extended to Include the Flow Condition in which an Upstream Swirl Velocity Exists

IN order to determine the performance of a ducted fan over a range of off‐design operating conditions it is possible to use the nomogram method of analysis described by J. F. M. Scholes. The method requires the use of a number of charts, each one being applicable only to a single radius ratio. Moreover each chart depends on the aerofoil characteristics of the blade element, so that it applies only to a single section shape operating at a given Reynolds Number. No account is taken of interference effects or compressibility. Despite these limitations the nomogram method may be valuable if it is required to analyse a number of fans employing the same blade section over a similar range of Reynolds Numbers.