Large-scale advanced propeller blade pressure distributions - Prediction and data
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Nallasamy, N.↗
Engineering topics
Bober, L. J.
Publications and source records attributed to Bober, L. J..
Large scale advanced propeller blade pressure distributions - Prediction and data
Two Euler analysis techniques, finite difference and finite volume, are employed to predict the blade surface pressure distributions of a large scale advanced propeller. The predicted pressure distributions are compared with wind tunnel data. Both techniques produced blade pressure distributions which are in fairly good agreement with the data over the range of test Mach numbers of 0.2 to 0.78. However, the numerical simulations fail to predict correctly the measured pressure distributions for the low Mach number, high power case which seem to have a leading edge vortex. A discussion of the compressibility effects is also presented.
Nallasamy, M.↗
Large-scale advanced propeller blade pressure distributions: Prediction and data
Two Euler analyses techniques, finite difference and finite volume, were employed to predict the blade surface pressure distributions of a large scale advanced propeller. The predicted pressure distributions were compared with wind tunnel data. Both techniques produced blade pressure distributions that are in fairly good agreement with the data over the range of test Mach numbers of 0.2 to 0.78. However, the numerical simulations fail to predict correctly the measured pressure distributions for the low Mach number, high power case. The data indicate the presence of a leading edge vortex for this case. A discussion of the compressibility effects is also presented.
Nallasamy, M.↗
Euler analysis of transonic propeller flows
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Barton, J. M.↗
Numerical evaluation of propeller noise including nonlinear effects
Propeller noise in the acoustic near field is presently determined through the integration of the pressure-time history in the tangential direction of a numerically generated flowfield around a propfan of SR-3 type, including the shock wave system in the vicinity of the propeller tip. This acoustic analysis yields overall sound pressure levels, and the associated frequency spectra, as a function of observer location.
Korkan, K. D.↗
Improved Euler analysis of advanced turboprop propeller flows
An implicit approximate factorization scheme in conjunction with a new boundary treatment was used to compute the inviscid flow field about an advanced high-speed propeller. The method of characteristics was used to apply impermeable boundary conditions. The convergence history of numerical calculations shows substantial decrease in the residual error decay. Euler solutions were computed for SR-3 propeller geometry and the results were compared with the experimental data and previous numerical results.
Yamamoto, O.↗
An analysis for the sound field produced by rigid wide cord dual rotation propellers of high solidarity in compressible flow
An unsteady lifting service theory for the counter-rotating propeller is presented using the linearized governing equations for the acceleration potential and representing the blades by a surface distribution of pulsating acoustic dipoles distributed according to a modified Birnbaum series. The Birnbaum series coefficients are determined by satisfying the surface tangency boundary conditions on the front and rear propeller blades. Expressions for the combined acoustic resonance modes of the front prop, the rear prop and the combination are also given.
Ramachandra, S. M.↗
An approach to the calculation of the pressure field produced by rigid wide chord dual rotation propellers of high solidity in compressible flow
An unsteady lifting service theory for the counter-rotating propeller is presented using the linearized governing equations for the acceleration potential and representing the blades by a surface distribution of pulsating acoustic dipoles distributed according to a modified Birnbaum series. The Birnbaum series coefficients are determined by satisfying the surface tangency boundary conditions on the front and rear propeller blades. Expressions for the combined acoustic resonance modes of the front prop, the rear prop and the combination are also given.
Ramachandra, S. M.↗
Inviscid analysis of advanced turboprop propeller flow fields
A three-dimensional Euler code, previously developed for high speed propellers, was rewritten and vectorized for the Cray computer. Calculations were compared with previous results and measurements. The new code requires less memory and is more than two times faster than its predecessor. The new boundary conditions produced more accurate results and improved stability. The accuracy and stability characteristics also resulted in reduced manual intervention required to obtain solutions. The code is a useful tool for examining the fluid dynamics and performance of propellers.
Barton, J. M.↗
Summary of recent NASA propeller research
Advanced high speed propellers offer large performance improvements for aircraft that cruise in the Mach 0.7 to 0.8 speed regime. At these speeds, studies indicate that there is a 15 to near 40 percent block fuel savings and associated operating cost benefits for advanced turboprops compared to equivalent technology turbofan powered aircraft. Recent wind tunnel results for five eight to ten blade advanced models are compared with analytical predictions. Test results show that blade sweep was important in achieving net efficiencies near 80 percent at Mach 0.8 and reducing nearfield cruise noise about 6 dB. Lifting line and lifting surface aerodynamic analysis codes are under development and some results are compared with propeller force and probe data. Also, analytical predictions are compared with some initial laser velocimeter measurements of the flow field velocities of an eight bladed 45 swept propeller. Experimental aeroelastic results indicate that cascade effects and blade sweep strongly affect propeller aeroelastic characteristics. Comparisons of propeller nearfield noise data with linear acoustic theory indicate that the theory adequately predicts nearfield noise for subsonic tip speeds, but overpredicts the noise for supersonic tip speeds.
Mikkelson, D. C.↗
Summary of recent NASA propeller research
Advanced high-speed propellers offer large performance improvements for aircraft that cruise in the Mach 0.7 to 0.8 speed regime. At these speeds, studies indicate that there is a 15 to near 40 percent block fuel savings and associated operating cost benefits for advanced turboprops compared to equivalent technology turbofan powered aircraft. Recent wind tunnel results for five eight to ten blade advanced models are compared with analytical predictions. Test results show that blade sweep was important in achieving net efficiencies near 80 percent at Mach 0.8 and reducing nearfield cruise noise by about 6 dB. Lifting line and lifting surface aerodynamic analysis codes are under development and some results are compared with propeller force and probe data. Also, analytical predictions are compared with some initial laser velocimeter measurements of the flow field velocities of an eightbladed 45 swept propeller. Experimental aeroelastic results indicate that cascade effects and blade sweep strongly affect propeller aeroelastic characteristics. Comparisons of propeller near-field noise data with linear acoustic theory indicate that the theory adequately predicts near-field noise for subsonic tip speeds but overpredicts the noise for supersonic tip speeds.
Mikkelson, D. C.↗
An analytical and experimental comparison of the flow field of an advanced swept turboprop
An argon ion laser velocimeter with four beams was used to measure the detailed flow-field of an advanced eight blade propeller with 45% of tip sweep in an 8x6 foot supersonic wind tunnel. Data were obtained at a free stream Mach number of 0.8, the design advance ratio of 3.06 and a power coefficient of 1.8. Data are presented for inlet flow, exit flow, flow within the blades and flow slightly outside the blade tips. The data are compared to a lifting line theory. In general, the results of the comparison are considered favorable.
Neumann, H. E.↗
Prediction of high speed propeller flow fields using a three-dimensional Euler analysis
To overcome the limitations of classical propeller theory, a computer program, NASPROP-E, was developed which solves for the flow field surrounding a multibladed propeller and axisymmetric nacelle combination using a finite difference method. The governing equations are the three dimensional unsteady Euler equations written in a cylindrical coordinate system. They are marched in time until a steady state solution is obtained. The Euler equations require no special treatment to model the blade work vorticity. The equations are solved using an implicit approximate factorization method. Numerical results are presented which have greatly increased the understanding of high speed propeller flow fields. Numerical results for swirl angle downstream of the propeller and propeller power coefficient are higher than experimental results. The radial variation of coefficient are higher than experimental results. The radial variation of swirl angle, however, is in reasonable agreement with the experimental results. The predicted variation of power coefficient with blade angle agrees very well with data.
Bober, L. J.↗
New test techniques and analytical procedures for understanding the behavior of advanced propellers
Analytical procedures and experimental techniques were developed to improve the capability to design advanced high speed propellers. Some results from the propeller lifting line and lifting surface aerodynamic analysis codes are compared with propeller force data, probe data and laser velocimeter data. In general, the code comparisons with data indicate good qualitative agreement. A rotating propeller force balance demonstrated good accuracy and reduced test time by 50 percent. Results from three propeller flow visualization techniques are shown which illustrate some of the physical phenomena occurring on these propellers.
Stefko, G. L.↗
An analytical and experimental comparison of the flow field of an advanced swept turboprop
(Previously announced in STAR as N83-14061)
Neumann, H. E.↗
Prediction of high speed propeller flow fields using a three-dimensional Euler analysis
Previously announced in STAR as N83-19710
Bober, L. J.↗
Factors influencing the predicted performance of advanced propeller designs
The assumptions on which conventional propeller aerodynamic performance analyses are based can be seriously violated when advanced high speed propellers are analyzed. Studies have been performed using a lifting line representation for the propeller to determine the sensitivity of predicted propeller performance to various assumptions in the analysis. Items which have been studied include the method of determining blade section lift and the effects of blade section drag, camber and blade sweep. The effects of nonuniform flow into the propeller and compressibility have also been studied. Comparisons of analytical and experimental results are presented to demonstrate the overall validity of the results.
Bober, L. J.↗
Factors Influencing the Predicted Performance of Advanced Propeller Designs
The assumptions on which conventional propeller aerodynamic performance analyses are based can be seriously violated when advanced high speed propellers are analyzed. Studies were performed using a lifting line representation for the propeller to determine the sensitivity of predicted propeller performance to various assumptions in the analysis. Items studied include the method of determining blade section lift and the effects of blade section drag, camber and blade sweep. The effects of nonuniform flow into the propeller and compressibility were also studied. Comparisons of analytical and experimental results are presented to demonstrate the overall validity of the results.
Bober, L. J.↗