Showing papers on "Blade element theory published in 1971"
TL;DR: In this article, the linearized equations of blade motion up to high rotor advance ratios are applied to the quadrotor blades with elastic flapping restraint, only vertical turbulence components are considered and the ratio of turbulence scale length over rotor radius L/R is assumed to be large.
Abstract: The developed analytical methods are applicable to the linearized equations of blade motion up to high rotor advance ratios. Rigid flapping blades with elastic flapping restraint are stipulated, only vertical turbulence components are considered and the ratio of turbulence scale length over rotor radius L/R is assumed to be large. On the basis of computed threshold crossing expectations, the blade response can be described as a quasi-coherent narrowband random process. The limiting case of infinite L/R is easy to compute and to interpret and yields conservative values for the mean square blade response. Numerical analysis for a slowed unloaded rotor based on low-altitude turbulence data indicates in the absence of gust alleviating device an appreciable probability of excessive blade flapping or flap-bending. w L cor , (S) -^subscripts
39 citations
TL;DR: In this paper, a qualitative discussion of the geometrical properties of dihedral and sweep in turbo-machine blade rows is presented with a discussion of fluid dynamic effects upon blade to blade and meridional flows.
Abstract: A qualitative discussion of the geometrical properties of dihedral and sweep in turbo-machine blade rows is presented with a discussion of the consequent fluid dynamic effects upon blade to blade and meridional flows. Results of blade to blade calculations for four heavily loaded turbine cascades of infinite span and various angles of sweep are presented. Annulus end wall interference effects on blade to blade flow are briefly discussed with reference to previous work. The principal analytical contribution is a development of actuator disc theory to deal with meridional flows for swept cascades and for blade rows in cylindrical annuli.
36 citations
TL;DR: In this article, the equations for the flow through cascades of blades are averaged across the pitch and then compared with those for flow through hypothetical models of blade rows; a closely spaced blade row, an axisymmetric flow with body forces and the flow on a mean stream surface.
Abstract: The equations for the flow through cascades of blades are averaged across the pitch and then compared with those for the flow through hypothetical models of blade rows; a closely spaced blade row, an axisymmetric flow with body forces and the flow on a mean stream surface. It is shown that these models can provide an accurate representation for the overall flow changes across a blade row, but they cannot give an exact local matching with the averaged properties of the flow in the real cascade. The nature of the blade forces in the real flow and the body forces in the hypothetical flow is discussed.
27 citations
Patent•
17 May 1971TL;DR: A rotor blade for a convertiplane characterized by twist rate which is nonlinear but monotonic from blade root to blade tip and by camber nonlinear from root to tip to provide a lift due to camber which decreases from the root to an intermediate point along the length and increases from said intermediate point to the tip as discussed by the authors.
Abstract: A rotor blade for a convertiplane characterized by twist rate which is nonlinear but monotonic from blade root to blade tip and by camber nonlinear from blade root to provide a lift due to camber which decreases from blade root to an intermediate point along the length and increases from said intermediate point to blade tip.
8 citations
Dissertation•
01 Jan 1971
TL;DR: In this article, a broad investigation of the unsteady flow phenomena in axial flow compressor is presented, based on an analysis of hot wire measurements of the time variation in velocity at fixed points in the flow through a single stage machine with three blade rows.
Abstract: A broad investigation of the unsteady flow phenomena
which occur in an axial flow compressor is presented. It is
based on an analysis of hot wire measurements of the time variation
in velocity at fixed points in the flow through a single stage
machine with three blade rows. The study has been confined mainly
to the "potential flow" unsteadiness due to the rotor movement and
the effect of wakes from one blade row interacting with downstream
rows. A general experimental investigation of the compressor blade
wakes is included. The results are compared with velocity distributions
calculated from existing potential flow models of the flow
through a cascade, and a new model lased on the approximations of
thin aerofoil theory is developed by the author. Consideration is
given to the development of a model of a blade wake and the author's
potential flow model is extended to include a wake and boundary. layer
thickness effect. Also included is an account of a brief experimental
investigation of the noise generated by the compressor due to
blade row interaction effects.
1 citations
30 Sep 1971
TL;DR: In this article, the aerodynamic properties of rotor blade tip vortices were examined and the response of the trailing vortex core to changes in the flow was investigated, and a correlation between the trailing edge sweep angle at the tip and vortex core size was found.
Abstract: Several aspects of the aerodynamics of rotor blade tip vortices are examined. Two particular categories are dealt with; (1) dynamic loads on a blade passing close to or intersecting a trailing vortex, and (2) the response of the trailing vortex core to changes in the flow. Results for both categories are in reasonable agreement with existing data, although lower pressure gradients were obtained than anticipated for category one. A correlation between trailing edge sweep angle at the tip and vortex core size was noted for category two.
01 Dec 1971
TL;DR: A FORTRAN 4 computer program for the design of two-dimensional supersonic rotor blade sections corrected for boundary-layer displacement thickness is presented in this paper, where the ideal rotor is designed by the method of characteristics to produce vortex flow within the blade passage.
Abstract: A FORTRAN 4 computer program for the design of two-dimensional supersonic rotor blade sections corrected for boundary-layer displacement thickness is presented. The ideal rotor is designed by the method of characteristics to produce vortex flow within the blade passage. The boundary-layer parameters are calculated by Cohen and Reshotoko's method for laminar flow and Sasman and Cresci's method for turbulent flow. The program input consists essentially of the blade surface Mach number distribution and total flow conditions. The primary output is the corrected blade profile and the boundary-layer parameters.