Propeller Power Research Articles

Transonic computational method for an aft-mounted nacelle/pylon withpower effect

A computational method has been developed for computing transonic flows about an aft-fuselage mounted capped-nacelle/pylon configuration with/without propeller power. A hybrid conformal-mapping/transfinite-interpolation scheme is developed to generate body conforming grid systems; a multigrid line-relaxation scheme is applied to solve the potential flowfield; an Euler correction method based on the Clebsch transformation is employed to simulate the power effect; and an inverse boundary-layer method is incorporated to calculate the viscous flows over the pylon and fuselage surfaces. Included are comparisons of the solutions with available test data and the solutions of a panel method. The importance of the fuselage boundary-layer effect on the pylon pressure distribution is studied. The present method has been shown to be reliable, efficient, and general and has been successfully applied to compute a wide range of flow conditions, including those of high angles of attack.

Investigation of the aerodynamic performance and noise characteristics of a 1/5th scale model of the Dowty Rotol R212 propeller

SummaryAn investigation of the four-bladed Dowty Rotol R212 propeller (NACA 16 sections) has been made at l/5th scale (0·7 metre diameter) in the RAE 1·5 metre acoustic tunnel. Propeller power absorption and thrust have been measured over a range of rotational speeds up to 8000 rev/min at mainstream speeds from 15 m/s to 60 m/s for a range of blade settings. Slipstream wake surveys show outward movement of the position of the peak pressure as propeller loading is increased.Noise analysis demonstrates the predominance of multiple tones whose number and intensity increase with helical-tip Mach number. An empirical formula shows that the fundamental tone SPL varies with tip speed and power loading in an identical manner to that observed on a modern ARA-D section propeller.

Propulsion of single-screw ships

On the basis of the little clause in the “Outline Specification” for a new ship: “Trial speed at a load draught of … with the engine at maximum continuous rating has to be …” some aspects regarding propulsion of single-screw ships are discussed, especially the problem of how to combine the hull form, the propeller and the machinery for propulsion in such a way that an optimal solution is obtained. In order to limit the problem, only ships provided with a single conventional propeller for propulsion are considered. A parameter study of a single-screw vessel has been done in order to get some concrete information on the interaction between ship, engine and propeller, and to investigate how the ship propeller power curve should be placed in relation to the engine operation area and to investigate changes in this relationship when the conditions change.

Propulsion

Few aeronautical engineers would disagree that the development of new propulsive systems has been the main influence responsible for the achievement of supersonic flight. This is not the same thing as claiming that sustained flight at these speeds, over fairly long ranges and with reasonable economy, would ever be possible without correspondingly large contributions from the aerodynamicist, the structural engineer, and the designers of various equipment. However, if we had been limited for all time to the piston engine/ propeller power plant almost universally employed juring the first 40 years of heavier-than-air flight, it is unlikely that we should ever have exceeded a Mach number of one.