https://www.research.manchester.ac.uk/portal/files/156596374/Inop_Paper_Fin_V1.pdf

Noise reduction of a Counter Rotating Open Rotor through a locked blade row

A time domain source-doublet surface paneling method is developed for analyzing the unsteady loads on counter rotating propellers in incompressible irrotational flow. A scheme for treating the blade-wake interaction problem is described. Sample results for single rotation propellers are given, with comparisons to alternate theories and experiment. Finally, some preliminary results for quasi-steady and fully unsteady loads on counter rotating systems are presented.

Panel Method for Counter-Rotating Propfans

Math Modeling of Propeller Geometry and Aerodynamics

A propeller system with two propellers, arranged one behind the other and separated by a propeller gap, respectively comprising a propeller hub and at least one rotating force measuring device, comprises at least two differential pressure sensors and an evaluation unit. The rotating force measuring devices are mechanically connected to the respective propellers and are adapted for determining the individual thrust force of each propeller. At least one of the said differential pressure sensors is arranged on or in each propeller and is adapted for measuring a differential pressure between the propeller gap and the respectively opposing side of the propeller. By adding the measured individual thrust forces and by subtracting the gap area forces that are based on the respectively measured differential pressures, the evaluation unit can determine a precise overall thrust force for the propeller system.

Propeller system with two counter-rotating propellers, a method for measuring the thrust of a propeller system with two counter-rotating propellers and wind tunnel with a model positioned therein having a propeller system

Blade element model is one of the most popular models for rotating-wing analysis and design. Many legacy tools are based on blade-element and capable of analysing only a single-rotating configuration. The current scope suggests a simple and effective method for extending such applications to contra-rotating configurations. The model based on the classic axial-momentum theory and assumes rigid wake. The method is validated versus results from propeller, hovering rotor, and prop-fan experiments. The experiments present both single and dual-rotating wing configuration, which share the same blade geometry and test facilities. This enables the isolation of the single-versus dual-rotating configuration influences, thus validating the suggested model with high level-of-confidence. The validation shows that the same trends of the single-rotating model appears in the dual-rotating analyses. Moreover, the difference between single and dual rotating configuration is replicated accurately compared to the test results. This proves the validity of the suggested model extension. The model validation also exhibits the differences between the accuracy of the forward and rear rotating disk in the contra-rotating configuration. The rear disk contributes by the no-swirled wake and exhibits accurate results compared to the forward disk which operate similar to a single rotating wing, hence suffers from the same inaccuracies.

Extending Blade-Element Model to Contra-Rotating Configuration

A low-speed (Mach 0 to 0.3) wind-tunnel investigation was conducted to determine the basic performance, force and moment characteristics, and flow-field velocities of single- and counter-rotation propellers. Compared with the eight-blade single-rotation propeller, a four- by four- (4 x 4) blade counter-rotation propeller with the same blade design produced substantially higher thrust coefficients for the same blade angles and advance ratios. The results further indicated that ingestion of the wake from a supporting pylon for a pusher configuration produced no significant change in the propeller thrust performance for either the single- or counter-rotation propellers. A two-component laser velocimeter (LV) system was used to make detailed measurements of the propeller flow fields. Results show increasing slipstream velocities with increasing blade angle and decreasing advance ratio. Flow-field measurements for the counter-rotation propeller show that the rear propeller turned the flow in the opposite direction from the front propeller and, therefore, could eliminate the swirl component of velocity, as would be expected.

/pdf/low-speed-wind-tunnel-tests-of-single-and-counter-rotation-183m70i0sr.pdf

Low-speed wind-tunnel tests of single- and counter-rotation propellers

As part of a research program on advanced turboprop aircraft aerodynamics, a low-speed wind-tunnel investigation was conducted to document the basic performance and force and moment characteristics of an advanced eight-bladed propeller. The results show that in addition to the normal force and pitching moment produced by the propeller/nacelle combination at angle of attack, a significant side force and yawing moment are also produced. Furthermore, it is shown that for test conditions wherein compressibility effects can be ignored, accurate simulation of propeller performance and flow fields can be achieved by matching the nondimensional power loading of the model propeller to that of the full-scale propeller.

G. L. Gentry

Papers

Low-speed wind-tunnel tests of single- and counter-rotation propellers

Low-speed wind-tunnel tests of an advanced eight-bladed propeller