US2418380A - Inlet air opening of jet propelled planes - Google Patents

Description

April 1947- D. K. WARNER r 2,418,380

INLET AIR OPENING OF JET PROPELLED PLANE Filed May 26. 1943 2 Sheets-Sheet l April 1, 1947.

INLET AIR OPENING OF JET PROPELLED PLANE Filed May 26, 1943 D. K. WARNER 2,418,380

2 Sheets-Sheet 2 f Patented Apr. 1, 1947 INLET Ara OPENING OF JET PROPELLED PLANES Douglas K. Warner, Sarasota, Fla. Application May 26, 1943, Serial No. 438,800

4 Claims. (c1. 244-13) The present invention relates to improvements in operating means for airplanes of all kinds, although since it has particular reference to propulsion means for jet propelled compression planes I have described it with particular refer ence to that type of plane.

The inherent problem in an efficient jet propelled plane is'that the opening which receives the air required for propelling the plane should be reduced in size as the plane moves faster. For example with the same pressure conditions fore and aft of the inlet opening some 40 times the weight or cu. ft. of air would pass thru an opening moving at 400 miles an hour as one moving at miles per hr, The weight of air required to propel the plane increases in a lesser ratio than this and at speeds of 400 miles per hr. and above it is necessary to slow the air down before allowing it to contact moving propeller blades in order to prevent the air flowing over the tips of those blades from exceeding the speed of sound. If the air is' not slowed downbefore reaching the propeller or fan an enormous drag will be set up, accompanied by terrific shock stresses in the propeller blades. Accordingly "even barring efiiciency considerations favored by reducing the inlet opening at very high speedsit becomes essential that the inlet opening be smaller than the fan ,area at high speeds. At low speeds an entrance to the air intake of lesser area than said fan area decreases the efiiciency and capacity of the fan. It is possible by stream lines .to restrict the passage between the entrance and the fan without causing that same decrease. in efficiency and capacity resulting from an entrance opening as small as said passage restriction. Accordingly the desired results may be obtained by changing the shape of the opening ahead of the orific throat, in sucha manner that at low plane speeds the air is speeded up over a lip to the orifice and then slowed down in a diverging nozzle leading to the fan whileat high speeds the lower lip of the orifice entrance is removed and the air enters without initial velocity gain and is just slowed up behind the.

orifice. Removal of said lower lip greatly reduces the head resistance at high speed in addition preventing excessive air speeds at the propeller blades. i

In a good airfoil while the lift coefiicient increases from .4 to 1.6 the drag increases from .02 to .20. This means that a plane requiring a lift coeflicient of 1.6 at 100 miles per hr.requires only A, as much at 200 miles per hr. and accordingly the dragcoefiicient is 1% as great" andthe actu al .drag only its as great thereby requiring a thrust less than half as much as when flying half that speed'at the same altitude. The complete compression plane has a lift coefficient many times greater than the normal airfoil cited above but has the same characteristics of requiring lower thrust at high speed. The thrust from a jet equals the weight of air timesits rearward velocity. If the velocity of the jet remained constant (it' doesnt), less than half the weight of air would have to be handled at twice the speed while a fixed front opening would be taking in twiceas much air at the higher speed, this indicating a marked decrease in frontal opening is required. Actually the jet velocity relative to the ground does not stay constant but decreases as velocity of the plane increases. Let us take for example a compression plane whose fan at starting gives an air speed of 200 miles per hr. By difiusion nozzles below the plane this is converted into a pressure lift of 20.025 inches of water or 104 /2 lbs. per sq. it. plus a suction lift above the wing immediately behind each slot of about half that amount. Ihe pressure lift extends only under the central portion of the wing resulting in a total average lift at zero velocity of approximately 1.16 lbs. for each square foot of all wing surfac'e. If the planejhas a central portiori '7 .ft. wide and 34. ft. long and spread or 27 ft. the central or pressure area is 233 sq. ft. and the wings 120 sq. ft. giving a total area of 358 sq.

ft. and a 11ft at zero velocity of 42,700 lbs. when developing 3.06 R, to theoretically expel i615 cu. ft. of air per second at 200 miles per hr. from [the slotsin the top of the Wingsurface, giving the f 23,300 lb. ft. sea, the drag on the plane due to air friction and no induced drag while skimming,

1,000 lbs., and the remaining'thrust available for acceleration 22 ,300 lbs.,.so requiring about 6 min- 7 utes more to accelerate to 200 miles per hr. .before which time the fla'punder the nose of the plane has folded back, the tail has lifted allowing air to escape rearwardly in back and the ,en-

gine has increased'its speed 30% above starting R. P. M. i

-It will be noted that while the propulsive emc'i'ency of the jets above the wing increases with increased speed. their lift decreases while the lift the fans to two or more atmospheres of adding cent of op-enage of the various jets, or by pumping fuel from rear tail tanks to thebow floats,

or by changing the attack angle or of the pilotv It should be noted that there is a marked distinction between openings in the top and bottom surfaces of the plane. Entrance to the upper jets is by an orifice with a bluntly rounded lower edge and smooth wall upper surface and no appreciable length so that maximum air velocity may be obtained where not over two atmospheres pressure is maintained inside the plane. The lower nozzles however must be designed to slow the air down by long diffusion passages so that it will emerge at the same velocity at which the air is moving on the lower side of the plane. The result of slowing down the air leaving the fan is to build up pressure and as long as that compressed air remains under pressure it will impart a definite upward lift on the bottom of the plane. The duration of what might be called an explosive lift extends backward from the tail end of the nozzle in decreasing magnitude, the distance backward and magnitude being proportional to the square of theplanes speed. This accordingly is responsible for the, rearward movement of the pressure center on the bottom of the plane which is so highly important in offsetting the opposite motion of the C. P. on the top surface due to the rapidly diminishing proportion of lift due to jet action on the top surface, as compared with lift derived from forward motion. It should, be noted that the principal bottom lift is. not caused by weight of air ejected downwardly with consequent reaction upward but by creating an instantaneous pressure wave'below the plan which even though emitted only under the central portion when'not 'confined'between the runners by a surface, spreads laterally out under the tail wing. It might be likened to the lift developed by exploding'flak beneath a plane and as clarification, I mention the flak lift as something frequently recognized and described. This pressure exists only me. very thin strata of air beneath the plane. it vanishes while the plane moves half its length while traveling at extreme speed,

restrict airleakage from the confined space below the plane. I also mention as in former applications that the efficiency of" the engine is increased because all the radiated and exhaust heat and velocity energy is introduced into air brought to considerable pressure elevation by the propulsion fan and in the resulting expansion of that air from either upper or lower orifices the heat is an important asset, capable, especially at very high altitudes, of more than doubling the power obtained from burning 'a'given weight of fuel in the engine, and in some instances where additional fuel is burned directly in the-air compressed by ten fold to the normal engine .power.

As originally cited a very important element in maintaining high efficiency in such a jet propelled plane is the ability to change the areas of the openings where the air enters and leaves the plane in a manner that does not impair the strength or stream lines of the plane and it is to this element that I am directing this application.

Figure 1 shows'a view of the compression .plane from above.

Figure 2 shows the front portion of the'same plane with the bow flap swung back under the plane on hinge 5.

Figure 3 shows a section thru the center of the plane.

Figure 4 shows the piston and tubes which op- .eratethe bow flaps.

In Figure 1 it can be seen that air enters into the compression plane in the opening below the leading edge 22 and above the hinge 5. After being speeded up by fan blades 9 shownin Fig. 3 it leaves through upper slot 3| and lower diffuser 28 and thru slots in back of fuselage controlled by the forward airfoils l5 the rearward airfoils I1 and lateral airfoils in tail wing l9 and 32.

A passenger cabin is located each side of the inlet opening with windows [2 opening in to air inlet passage as well as to the outside so that unobstructed view inall directions is obtained from either cabin, either thru the opening ahead, or directly outside, or thru the windows of the opposite cabin. I

Auxiliary air foils, 18 are controlled from the cabin to deflect air over the main wings which are at the rear. These normally are set at a small negative angle of attack in order toincrease the air velocity over the forward part of the rear wing and maintain that velocity for a longer distance. The higher the attack angle at whichthe plane may be flying the greater the negative angle of the pilot wing should be for maximum efficiency but the pilot wing may be used as a stabilizer ,as well as for adding 50% to the lift of the main wing. Changing the attack angle of the pilot or auxiliary airfoil moves the center of pressureof the main wing so providing the'pilot with additional means of controlling the flight path of the plane, usingithese in-place 'of ailerons or. elevaabout their chord from theirleading edge.

The same motion turns airfoils I] clockwise and opensall the rearward slots. Controls 'on.the wheel make it possible to'decrea'se the extent of opening of all slots or entirely' close them .all. To make a right bank and turn left 'slot 32 is closedinthe left wing and slot I!) opened Wider 1 in right wing. This stops the jet thrustland lift on the left side and increases it on'the right side so giving bank and turn in one operation and without the counteractingforces usually produced by rudder and ailerons. i v

In Fig. 3 it will be seen that the under'lip of the .plane, 1 is set rearward of the'upperlip'fior nose of the plane) 33, separated therefrom by the distance A. From the forward edge of i, hung on hinge 5, is upper fiap 4, extending downward and forward to hinge I which is directly below edge 33 a distance B which isconsiderably greater than distance A. Lower flap 3 is hinged at I synapse to upper flap 4. Its trailing edge drags over the surface below slipping snugly past the vertical inside walls of the cabins and while free to move up and down over the waves or rough surface, securely prevents leakage of compressed air under the plane from moving forward. As long as the pressure under the plane remains higher than the pressure due to forward motion on the front of plates 3 and 4 and hinge I will remain forward as shown but when the speed of the plane has produced enough additional lift to raise the tail of the plane and allow. the air pressure below to escape rearward the forward pressure against these flaps will be removed to an extent that will permit the air in front of the plane to blow the flaps back under the body. Normally, pipe or cylinder 26, is open to the outside air thru 3 way cook 34. and piston 25 and hollow rod 24 may move freely back due to the air pressure on flaps 3 and 4, and these flaps will form a smooth bottom for airfoil I when in their retracted position. However in the emergency of engine failure in high flight the cook 34 is turned so as to close communication with the outside air and connect cylinder 26 with liquid CO2 flask 30. The liquid will flow down into the cylinder 26 from the flask and the heat will evaporate the liquid and push piston 25 and rod 24 forward so pressing hinge I forward with flap 4 and thereby greatly increase the size of the air opening leading inside the plane. The dotted lines to point 6 show' where a maximum force resists the motion of piston 25 requiring a force of over 1000 lbs. per sq. inch to push the piston forward. Near the end of the stroke the resistance decreases and in order to prevent the piston blowing out the end of the cylinder cap 36 is screwed to the end of cylinder 26. The cap is fitted with compression rings 31 which contract on rod 24 as shown and prevent leakage of air from the annular passage space 35 formed between cylinder 26 and rod 24. As the piston is forced forward in the cylinder by C02, air is compressed in space 35 until the pressure becomes so enormous that it overcomes the pressure and inertia tending to drive the piston forward. However a momentary stop due to this counterpressure at the end of the forward stroke flutters rings 38 on piston 25 from their seats at varying sides of the ring slots and quickly equalizes the pressures in 35 and 26 and the piston is then held tight against cylinder head 36.

This forward motion of flap 4 will produce a large drag forward slightly below the C. G. and will so tend to dive the plane which because of the engine failure had lost a lot of lift from the air jets back of the C. G. which would otherwise have caused the plane to increase its attack angle. The main function of this action is however to resupply the air pressure formerly furnished by the engine and its fan even tho it must be obtained at the cost of additional air drag greater than the propulsive jet power derived from that drag. This procedure restores to the pilot most of his original control by the manipulation of the slot airfoils and permits the plane to descend in a long glide instead of at once going into a stall which as mentioned in a former application was a difi'iculty accompanying the enormous load carrying ability of the compression plane.

As already explained the air opening of the compression plane should be reduced as the speed increases in order that the weight of air handled by the fan shall not increase too rapidly and in order that air speed over the fan blades shall not exceed the speed of sound at any point and so '6 as to eliminate in most cases the need for chang ing the pitch of the fan blades, thereby simplifying and reducing the cost of the propulsion fans,

and finally so that air speeds approaching.90%

the speed of sound may be obtained without forming a compressibility burble either on the wings or the propeller blades. The ordinary plane will form such burbles on the propeller blades at speeds half as fast as sound because the propeller in its helical path thru the air travels twice as fast and far as the plane if the tip has an effective pitch of 30 degrees. A pitch that high puts almost the whole blade beyond the stall point at slow speed takeoff, making short takeoff runs impossible in conjunction with high top speeds where the ordinary fixed pitch propeller is used. Even where the propeller pitch is adjustable it is impossible to build a propeller with efficient attack angles at both take off and Very high speeds. Take for example an 11 ft. propeller mounted in a plane that takes oif at ft. per sec. or 68 miles per hr. In such a plane the propeller R. P. M. should be reduced from 1720 R. P. M. at take off to 1350 R. P. M. at maximum speed of 420 miles per hr. Since the engine will develop less H. P. at the lower R. P. M. required by sound effects on the prop, unless a gear shift is provided, maximum engine H. P. can not be obtained at take off and highest speed. Also While a pitch advance of 33.1 is required at the high speed at the propeller tip a 51.3 degrees advance is required at 30% of blade length, or 18.2 degrees more than at the tip. Since the efficient attack angle variation of propeller airfoils is limited to less than 6 degrees the variable pitch propeller must be very inefiicient over the circle of the inside 75% diam. in addition to requiring a disastrous reduction of R. P. M. at 420 miles per hr. The much better procedure is to cover the 75% inside diameter of the prop circle with a streamlined deflector, increase the number of blades and increase the density of the air which the blades handle at high plane speeds; by decreasing its velocity before it touches the blades. By doing this the R. P. M. does not have to be reduced so much, and because the blades will be working on denser air the slightly lower R. P. M. will be accompanied by an increase in engine torque so exactly fitting the engine power curve. This again requires a reduction of air inlet opening in front of the plane with increase of speed, the subject of this invention.

Figure 1 shows the compression plane with the flap forward increasing the entrance area and Fig. 3 shows the flap in the same position. Fig. 2 shows the flap in the rear flying position as it is also shown in the upper dotted lines of Fig. 3. When the flap is back the opening is similar to that of the Hanley Page slot. It has little frontal area, and with the fan behind it, inside the plane, causes no drag. With the flap forward there is the large entrance B and A becomes the throat of a Venturi passage.

I claim:

1. The combination in an airplane having a bottom surface pressure supported, with the propulsion fan of a flying machine of a diffusing passage of gradually and continuously increasing area rearwardly forward of said fan and a flap hinged at the lower forward portion of said passage said flap being extendable in either a forward direction or in a rearward direction beneath and adjacent to the bottom surface of said flying machine and power means for advancing said flap from a rearward to a forward position.

7 2. The combination, with the propulsion device of a flying machine of a passageof continuously, gradually increasing area rearwardly, from a forward opening, and flap means for extending the length of said passage forwardly of its no.r

mai opening with a forwardly diverging passage and power means for advancing said flap from rearward to forward position.

3. In an aircraft having a pressure chamber beneath the lower surface thereof and wholly open to the air and to the water surface beneath said aircraft, the combination with the fan propulsion device of said aircraft of a passage of continuously, rearwardly, slowly increasing area ahead of said device, a flap'hinged below the lower forward portion of said passage in a manner whereby said flap may extend rearwardly close below the lower surface of said aircraft or extend forwardly thereby increasing the length and changing the taper of said passage, while at the same time providing an air seal for compressed air beneath the aircraft when said aircraft is close to the surface, and whereby said flap in flight and away from a surface forms an elevator assisting in preventing stall by making said aircraft dive, and passages rearward of said propulsion device communicating between said device and the air above and below said aircraft, said passages communicating with the air above discharging rearwardly in contracting passages,

and the passages communicating with the space 'below the aircraft having increasing area rearwardly.

4. In a combination, as in claim 3, means comprising said pressure chamber and for permitting blowing said fiap forward by air pressure which said propulsion device creates below said Diane.

DOUGLAS K. WARNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,486,644 Durr Mar. 11, 1924 1,585,281 Graddock May 18, 1926 1,725,914 Hallowell Aug. 27, 1929 2,329,606 Goodman Sept. 14, 1943 2,115,711 Finley May 3, 1938 1,864,912 Johnson June 28, 1932 2,087,832 Birkigt July 20, 1937 1,412,073 Wagenseil Apr. 11, 1922 FOREIGN PATENTS Number Country Date 359,421 German Sept. 21, 1922 305,641 British Apr. 16, 1928

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