US 2274743 A
Description (OCR text may contain errors)
March 3, 1942. RQSSKQPF 2,274,743
AIR IMPELLER DEVICE Filed April 17, 1939 Patented Mar. 3, 1942 2,274,743 v AIR IMPELLER DEVICE Hans Rosskopf, Berlin-Charlottenburg, Germany,
assignor to Brandenburgische Motorenwerke Gesellschaft mit beschrankter Haftung', Berlin- Spandau, Germany, a corporationof Germany Application April 17, 1939, Serial No. 268,213 In Germany April 25, 1938 4 Claims. (01.123-171) This invention relates to a cooling arrange ment for air-cooled radial aero-engines.
The natural cooling of an air-cooled aeroengine is no longer suificient to meet the exacting requirements of modern aircraft with respect to reducing the surface resistance and increasing the power output. The air-cooled engines therefore have been provided with blowers for forced cooling. It appears preferable, as a rule, to arrange a single blower suflicient for furnishing the entire amount of cooling air on the main shaft of the engine rather than employing a plurality of such blowers. It has been proposed to arrange such a single blower behind the engine, i. e. at the side away from the propeller, or in front of the engine. While both arrange ments are advantageous to a certain extent, they present nevertheless relatively great drawbacks. When arranging the fan behind the engine, difliculties are encountered in that the air produced by the fan must flow in a direction opposite to the direction of flight. For this reason the cooling air must be constrained to flow through definitely given passages so that the.
construction and the mounting of the engine are dependent upon the manner in which the air is to be directed. Furthermore, the auxiliary cooling apparatus must wholly or in part be displaced towards the propeller, and a number of other difficulties arise affecting, for instance, the suspension of the engine and the mounting of the engine in the nacelle.
The arrangement of the blower in front of the engine is more favorable in this respect. The auxiliary apparatus, as has hitherto been the case, may be arranged behind the engine; the suspension of the engine is not affected; the
conduits, struts, rods and the like may easily peller is farther away from the engine'to accommodate the blower therebetween. Particularly great difficulties are encountered if the propeller is of the variable pitch type, since the accessibility of the adjusting devices is rendered difficult by the blower lying between propeller and engine. If, on the other hand, the blower is arranged in. front of the propeller, no essential alteration in the conventional construction of the complete engine set is necessary. The relative arrangement of motor and propeller remains as is usual; the auxiliary apparatus and devices may be arranged in the most suitable way without affecting the arrangement of the conduits and rods; the cooling air may be supplied and carried off in a simple and favorable manner; the impact pressure may be utilized to the full extent; and in certain cases even a slight increase in the propelling force may be obtained by the blower. The bearings may be designed in a simple and oil-tight manner; the blower may easily be regulated, if desired, in dependence uponthe regulation of the propeller pitch. Unfortunately, however, these advantages are outweighed by a functional inefficiency of the known frontal blower arrangements as regards their main cooling operation. This deficiency is caused by the fact thatdue to the relatively large distance of the blower from the engine blower is located inside the sectional area of inlet of this cowl. Particularly favorable con-' ditions of flow are attained if guide blades for 'the air delivered by the blower are provided inside the cowl.
According to another feature of the invention, the blower is driven by the revolving propeller with the aid of a reduction gear having one of its members supported on the stationary gear housing. It is also possible to utilize the relative speed between the propeller shaft and the crank shaft for driving the blower. To this end a stationary toothed rim may be secured in the gear housing, one or more intermediate shafts mounted on the propeller hub being in engagement with the toothed rim. However, since a particular design of the propeller is necessary for this purpose and since also the oil-tight casing is not so simple to construct, it is, as a rule, easier to utilize the relative speed between the propeller shaft and crank shaft.
- Figs. 1 and 2 of the accompanying drawing illustrate two embodiments of the invention in sectional elevation. The arrangement of the blower and of its drive is substantially the same in both cases, only the manner in which the flow of air is guided being diflerent. Each figure shows an aero-engine having a plurality of radially extending cylinders i8 whose pistons,
not shown, cooperate with the crank shaft I. This crank shaft drives a drum 2 having an internal gearing meshing with a plurality of planetary pinions 3 of which only one is shown. These pinions mesh with a stationary sun wheel I and are carried by studs 5 fixed on the propeller shaft 6. The propeller I is mounted on the shaft 6. A revolving internally toothed rim 8 meshing with planetary pinions 9 (of which only one is shown) is also mounted on the propeller shaft 6. Pinions 9 are carried by individual pins ID mounted on a resilient extension.
Ii of the crank shaft l, i. e. on the bell-shaped portion l2. Pinions 9 mesh with the small gear III of the driving shaft H for the fan wheel l5 of the blower arrangement. The speed of this wheel is therefore determined by the relative speed between the crank shaft I and its extension II and the propeller driving shaft 6. As shown in the drawing, the fan wheel i5 is mounted in front of the propeller 1 inside the cowl i1 revolving together with the propeller. At the entrance of cowl I! and immediately behind the fan blades iii are mounted inwardly radiating guide vanes i6 for the air delivered by the blades. Theair therefore reaches in Fig. 1 the fan wheel I 5 with the full impact pressure and is supplied to the interior of the cowl I! through the guide vanes i6 and thus to the cylinders i8 which are located in the rear cowl portion.
As apparent from the drawing, the construction of the engine is not materially altered in this novel arrangement. The displacement of the center of gravity is slight, since the overhanging masses added to the propeller are small.
The arrangement according to Fig. 2 shows another possibility of controlling the flow of air insofar as the air is directed by the guide surfaces is first over the lower cylinder portion and then reverses its direction of flow as shown by the curved arrow at the cylinder I 8, flowing over the cylinder head and to escape in the neighborhood of the propeller through an annular gap 20 disposed at a point where a low pressure exists owing to known phenomena so that thereby the forced circulation of air is influenced in a favorable manner.
What is claimed -is:-
1. In an air-impeller device for aircraft having a propeller, in combination, a rotary airguiding cowl coaxial with said propeller, said cowl being connected with said propeller so as to rotate therewith, a blower disposed in front of and coaxial with said propeller, said blower being arranged near the inlet opening of said cowl, and driving means for actuating said propeller and blower, said means comprising a gear for imparting to said blower a rotary speed higher than that of said propeller.
2. In an air-impeller device for aircraft having a propeller, in combination, an air-guiding annular cowl coaxial with said propeller and having a cross section gradually increasing from a frontal inlet opening, said cowl being arranged to rotate with said propeller and having lateral openings passed through by the blades of said propeller, a blower of propeller type disposed in front of and coaxial with said propeller, said blower being rotatable relative to said propeller and arranged in the inlet opening of said cowl, and a transmission gear operatively connecting said blower with said propeller so as to rotate said'blower with a speed higher than that of said propeller.
3. In an air-impeller devic for aircraft having a propeller and means for driving'the. propeller comprising a coaxial shaft, in combination, a blower arrangement comprising a fan having a small diameter as compared with that of said propeller and being arranged in front of and coaxial with said propeller, and cowlshaped means for guiding the air from said blower past said propeller, a reduction gear coupling said shaft with said propeller, and a planetary transmission gear having two of its coacting gear members connected with said shaft and said propeller and its third member connected with said fan to rotate it with a speed depending upon the relative speed between said propeller and said shaft.
4. In an air-impeller device for aircraft having a propeller and means for driving the pro-, peller comprising a coaxial shaft, in combination, a blower arrangement comprising a fan having a small diameter as compared with that of said propeller and' being arranged in front of and coaxial with said propeller, and cowlshaped means for guiding the air from said blower past said propeller, a reduction. gear coupling said shaft with said propeller, a resilient extension connected with and arranged coaxial to said shaft, a planetary transmission gear having a sun wheel connected with said fan, a concentric internally toothed gear connected with said propeller and a planetary pinion carrier connected with said resilient extension so as to rotate said fan with a speed depending upon the relative speed of said propeller and said extension.