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NACA-RM-L51A19
The torsional deflections of several propellers under operating conditions
Year: 1951
Abstract: INTRODUCTION
The constant effort to maintain good propeller efficiency even at high subsonic flight speeds has resulted in the use of very thin propeller blade sections. Thin sections, however, reduce the ability of a blade to resist torsional deflection and, consequently, greater importance must now be attached to torsional deflection.
Previous optical measurements of blade torsional deflection under operating conditions, such as presented in reference 1, indicated negligible torsional deflections. The blades used in these earlier investigations, however, were considerably thicker than are now considered desirable. Prior to the present research a theory also existed for the calculation of blade deflections of propellers operating with combined lift and centrifugal forces, but no extensive comparison of measured and calculated data had been made.
The present trend in the -design of efficient propellers is in the direction to increase the importance of blade-twist. Unless attention is given to designing for a condition of no twist-by the arduous process of selecting sections having the proper aerodynamic as well as geometric characteristics, thin propellers operating at high speeds will experience large values of blade twist. Consequently, the effect of twist may have an important bearing on-the expected performance of a propeller.
The purpose of the present investigation was to determine by experiment and by theory the magnitude- of blade deflection. This determination of blade torsional deflection was a necessary contribution to the evaluation of the results of a pressure-distribution investigation in the Langley 16-foot high-speed tunnel. Experimental values of blade tortional deflections were obtained concurrently with the pressure-distribution data. The investigation was therefore comprehensive.
A desirable consideration in the present investigation is to show the possible application of the propeller-deflection theory in the propeller design stage as it is conceivable that torsional deflections may influence blade design.
The constant effort to maintain good propeller efficiency even at high subsonic flight speeds has resulted in the use of very thin propeller blade sections. Thin sections, however, reduce the ability of a blade to resist torsional deflection and, consequently, greater importance must now be attached to torsional deflection.
Previous optical measurements of blade torsional deflection under operating conditions, such as presented in reference 1, indicated negligible torsional deflections. The blades used in these earlier investigations, however, were considerably thicker than are now considered desirable. Prior to the present research a theory also existed for the calculation of blade deflections of propellers operating with combined lift and centrifugal forces, but no extensive comparison of measured and calculated data had been made.
The present trend in the -design of efficient propellers is in the direction to increase the importance of blade-twist. Unless attention is given to designing for a condition of no twist-by the arduous process of selecting sections having the proper aerodynamic as well as geometric characteristics, thin propellers operating at high speeds will experience large values of blade twist. Consequently, the effect of twist may have an important bearing on-the expected performance of a propeller.
The purpose of the present investigation was to determine by experiment and by theory the magnitude- of blade deflection. This determination of blade torsional deflection was a necessary contribution to the evaluation of the results of a pressure-distribution investigation in the Langley 16-foot high-speed tunnel. Experimental values of blade tortional deflections were obtained concurrently with the pressure-distribution data. The investigation was therefore comprehensive.
A desirable consideration in the present investigation is to show the possible application of the propeller-deflection theory in the propeller design stage as it is conceivable that torsional deflections may influence blade design.
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| contributor author | NASA - National Aeronautics and Space Administration (NASA) | |
| date accessioned | 2017-09-04T15:51:44Z | |
| date available | 2017-09-04T15:51:44Z | |
| date copyright | 01/01/1951 | |
| date issued | 1951 | |
| identifier other | QKSWXDAAAAAAAAAA.pdf | |
| identifier uri | https://yse.yabesh.ir/std/handle/yse/54892 | |
| description abstract | INTRODUCTION The constant effort to maintain good propeller efficiency even at high subsonic flight speeds has resulted in the use of very thin propeller blade sections. Thin sections, however, reduce the ability of a blade to resist torsional deflection and, consequently, greater importance must now be attached to torsional deflection. Previous optical measurements of blade torsional deflection under operating conditions, such as presented in reference 1, indicated negligible torsional deflections. The blades used in these earlier investigations, however, were considerably thicker than are now considered desirable. Prior to the present research a theory also existed for the calculation of blade deflections of propellers operating with combined lift and centrifugal forces, but no extensive comparison of measured and calculated data had been made. The present trend in the -design of efficient propellers is in the direction to increase the importance of blade-twist. Unless attention is given to designing for a condition of no twist-by the arduous process of selecting sections having the proper aerodynamic as well as geometric characteristics, thin propellers operating at high speeds will experience large values of blade twist. Consequently, the effect of twist may have an important bearing on-the expected performance of a propeller. The purpose of the present investigation was to determine by experiment and by theory the magnitude- of blade deflection. This determination of blade torsional deflection was a necessary contribution to the evaluation of the results of a pressure-distribution investigation in the Langley 16-foot high-speed tunnel. Experimental values of blade tortional deflections were obtained concurrently with the pressure-distribution data. The investigation was therefore comprehensive. A desirable consideration in the present investigation is to show the possible application of the propeller-deflection theory in the propeller design stage as it is conceivable that torsional deflections may influence blade design. | |
| language | English | |
| title | NACA-RM-L51A19 | num |
| title | The torsional deflections of several propellers under operating conditions | en |
| type | standard | |
| page | 58 | |
| status | Active | |
| tree | NASA - National Aeronautics and Space Administration (NASA):;1951 | |
| contenttype | fulltext |