AIRCRAF T ENGINEERING 165 July, 1933 Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics, and publications of other similar research bodies as issued The majority of centrifugal superchargers in the N.A.C.A. 7 ft. by 10 ft. wind tunnel, JAPAN constructed for aero-engine service have showed the effect of the ailerons and the tip DEPT. OF AERONAUTICS utilised diffusers containing either a com shapes on the general performance of the wing, paratively large number of short, straight FACULTY OF ENGINEERING, as well as on the lateral control and stability vanes or a smaller number of curved vanes of characteristics. The hinge moments were not IMPERIAL UNIVERSITY, TOKYO greater length. In bench calibration tests of measured but approximate values are given in (The University) such superchargers a t constant rotational speed th e first report of the series. (Report No. 419.) of the impeller, in which the mass flow of air I t was found that the general performance Journal, Vol. XX , No . 7. On the Induced is progressively reduced by restricting the out of the wing with slightly rounded tips was Velocity and Characteristics of a Propeller. let from the supercharger, it is found that the somewhat poorer than that of a previously By Tomijiro Moriya. pressure of the air at delivery increases as the tested rectangular wing, but that the perform Since Rankine proposed the so-called momen mass flow diminishes until a point is reached ance of the wing with tips having more extreme tum theory in 1865, numerous papers in con curvature was slightly better than that for a a t which the discharge pressure decreases nection with airscrew theory have been pub abruptly . This sudden breakdown in the rectangular wing. Both of aileron sizes lished, but all of them are, in a greater or character of the relation between delivery tested on the wing with slightly rounded tips lesser degree, imperfect in the quantitative pressure and mass flow is generally termed the gave lower rolling moments at high angles of verification. " surge point." As a rule it is accompanied attac k than the corresponding ailerons on b y an audible air vibration, the severity of rectangular wings. Reasonably satisfactory I t can be stated that the theory which which is greatly influenced by the volume of rolling moments a t all angles of attac k tha t can represents fully the motion of fluid in the air enclosed in the pipe system between the be maintained by average aeroplanes were neighbourhood of an airscrew is the most supercharger and the valve used for throttlirg reliable. From this point of view, the vortex given by all the short wide ailerons tested, th e air flow. with both tip shapes, and particularly by the theory, based on Prandtl's aerofoil theory, short wide skewed ailerons on the wing having surpasses th e others. For instance, th e existence Tests were undertaken to determine the tips with extreme curvature. In general, the of trailing vortices has been verified by recent comparative performance of a supercharger yawing moments were somewhat smaller for experiments, and as regards the trailing and the relative proximity of the air flows th e ailerons on the wings with rounded tips vortices no other theory can explain. corresponding respectively to maximum per tha n for the corresponding ailerons on rec But the performance calculated by the formance and to the inception of surging tangular wings. vortex theory is not in satisfactory agreement when several experimental types of dilluser with experiments. This is mainly due to and impeller were incorporated. The com unsuitable assumptions in calculating the in Technical Note No. 446. Estimation of ponents tested included both shrouded and duced velocity. unshrouded impellers having either curved or the Variation of Thrust Horse-power with straight radial blades, and diffusers (1) of In the present paper, the author explains Air Speed. By Shatswell Ober. simple vaneless type, (2) containing straight a simple and accurate method to obtain The purpose of this note is to present a vanes set at various angles, and (3) con the induced velocity by introducing an in method of estimating the variation of thrust structed in the form of two equi-angular spiral duction factor, which was calculated under the horse-power with air speed, when the power volutes. assumption that a fdament of the trailing unit consists of a conventional, thin, metal, vortices to be helical extending infinitely The simple vaneless diffuser was beneficial fixed-pitch airscrew driven by an internal- backwards with constant pitch and diameter, in regard to the postponement of surging combustion engine. Such a curve is needed and develops a method of calculating the but produced very low values of adiabatic for the estimation of aeroplane performance airscrew performance by using these results efficiency and pressure ratio of compression. in conjunction with a curve of horse-power and wind tunnel data of aerofoils. A diffuser of this type is unsuitable for use in required for maintaining level flight. The a high-speed compressor of small overall dia method is intended to be used in conjunction meter, as th e length of diffuser passage available with data on families of airscrews tested with is insufficient for reduction of the final air U.S.A. aeroplane and engine, given in the form of velocity t o th e required value. The performance selection charts of V/nD and propulsive effici U.S. NATIONAL ADVISORY of the supercharger was influenced to a con ency plotted against C, the speed power siderable extent by change of the diffuser vane COMMITTEE FOR AERONAUTICS coefficient. Complete familiarity with the use angle. of such charts is presupposed, as well as an (Superintendent of Documents, Washington) Improvements in compression ratio and understanding of the adaptation of them to the efficiency were obtained from the shrouded Technical Note No. 445. Wind-Tunnel determination of approximate characteristics impellers. In particular, the design incor Research comparing Lateral Control Devices, of other airscrews. As far as possible standard porating curved blades afforded a very high symbols are used. particularly at High Angles of Attack—VIII. compression ratio, but its maximum value at Straight and Skewed Ailerons on Wings each impeller speed was reached at an air flow- with Rounded Tips. By Fred E. Weick and GREAT BRITAIN in close proximity to that at which surging Joseph A. Shortal. commenced. AERONAUTICAL RESEARCH This report is the eighth of the series Comparing the performances of the super COMMITTEE of systematic tests in which various charger on the basis of the useful power which lateral control devices are compared. The (H.M. Stationery Office, London) it enables a hypothetical engine to develop, present tests were made with rounded tips ; and excluding the cases of the plain vaneless R. & M. No. 1503. December, 1932. one rather blunt and only slightly rounded, diffuser and the less favourable vane angles, Performance Tests of Certain Experimental the other more slender with the curvature no very pronounced superiority was exhibited Designs of Diffuser and Impeller in a Cen extending well in from the end of the wing. b y any of the combinations of experimental trifugal Supercharger, with Particular Re Medium-sized and short wide ailerons were components tested, although the spiral volute ference to their Influence upon Surging, in tested on both wings, and, in addition, skewed diffuser possessed certain characteristics ren cluding the Effect of an Impressed Periodicity ailerons were tested on the wing having the dering it particularly suitable for application more slender tip. The tests, which were made of Flow. By G. V. Brooke. (Price 2s. 6d.) t o aircraft engine superchargers.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Jul 1, 1933