JPH01262330A - High-speed turbo prop - Google Patents

Abstract

PURPOSE:To eliminate necessity of a very thin wing with a sweep back angle by a method wherein a propeller is pivoted on a pivot shaft of a spinner while a cowling is pivoted on a pivot shaft of the propeller so that a pitch angle of the propeller is constituted freely adjustable by driving the pivot shaft of the propeller. CONSTITUTION:A groove provided along the center 5 of pitch-variable rotation of a propeller 2 is fitted into a pivot shaft 4 fixed on a spinner 1. On a chip of the propeller 2, another pivot shaft 6 is provided along the center 5 of pitch- variable rotation. On this pivot shaft 6, a groove of a cowling 7 is supported freely rotatable and a rod 8 pivoted on the pivot shaft 6 is stored inside the cowling 7. A supporter 9 is further supported freely slidable at the rear of the cowling 7, and one end of the rod 8 is pivoted on it. A rack 11 and a pinion 13 are provided inside the supporter 9, and the pinion 13 is connected to a motor 12 located in the cowling 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high-speed turboprop useful for increasing the efficiency, improving safety, and reducing noise of a next-generation aircraft advance/retreat system.

(Prior Art) High-speed turboprops are being researched and developed as a propulsion system for next-generation aircraft, mainly in the United States. As shown in Fig. 5, the feature of this is that the wide cord has a receding angle and is supported by the spinner 1 in a variable pitch manner.
It is a technology that propels an aircraft with a cruise speed of about 0.75 by operating with about 10 wings. However, in order to maintain such a high cruising speed, with conventional technology, the relative speed at the tip of the propeller 2 has to be made higher than the speed of sound. Therefore, in order to prevent a drop in efficiency in supersonic flow, a sweep angle is provided to reduce the effective force to the propeller 2 below the speed of sound, and the thickness to chord length ratio is 2 to 3% to reduce resistance. It is essential to use ultra-thin material.

(Problems to be Solved by the Present Invention) The form of the prior art described above requires high technology from the viewpoint of aerodynamics and structural mechanics, and there is a risk that the propeller 2 will be damaged due to flutter during operation. Highly sexual.

Furthermore, as a fate of the propeller 2, it is necessary to change the mounting angle or pitch of the propeller 2 during the process from takeoff to cruising, and the conversion mechanism 3 is housed in a spinner 1 that supports the base of the propeller 2. However, since the outer diameter of Spinner I is extremely small, if the number of blades greatly exceeds 10,
Pitch changes become impossible. In other words, the variable pitch mechanism 3 of the propeller 2 having more than 10 blades cannot be housed in the spinner 1.

In addition, the high-speed turboprop cruiser Matsuha is 0.75
In order to increase the number of blades to 10, which is close to the limit,
By increasing the number of blades and increasing the chord length to a wider chord,
Even with the maximum aerodynamic load on the wings, the relative speed at the tip of the propeller still exceeds the speed of sound, forcing the use of ultra-Fj4 wings with swept angles.

Therefore, it is an object of the present invention to solve the above-mentioned problems of the prior art.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a propeller with 15 to 25 blades rotatably supported on a first pivot shaft fixed to a spinner of a turboprop. , rotatably supports a second pivot shaft fixed to the tip of the propeller, and is connected to an annular cowling disposed around the tip and a second pivot disposed at the variable pitch rotation center of the propeller. To provide a high-speed turboprop which has a variable pitch mechanism having a part arranged in a cowling and which allows the pitch angle of a propeller to be freely adjusted by the variable pitch mechanism.

(Function) By moving the variable pitch mechanism housed in the spinner at the base of the propeller to the tip of the propeller, which has a larger outer diameter, it becomes possible to vary the pitch spatially even if the number of blades greatly exceeds 1O. . For example, if the diameter is 3.6 m and the number of blades is 20, a distance between the blades of 015 m or more can be ensured. Therefore, from the conventional high-speed rotation of about 240 m/s to 120 m/s, which is half the circumferential speed of the conventional
If the circumferential speed is reduced to , the stress applied to the material due to centrifugal force will be (
1/2)", or 25%.The centrifugal force increases by adding a new variable mechanism, but if the wing attachment provides conditions to keep the centrifugal force applied to the root the same as before. , by simple force balance calculation, mt = (r,
/rz)(s/m,)m, ((ω1/ωt)” −
(m3/s+) (rz/r+))
1). Here, III+at is the mass of the conventional wing and variable mechanism part, rl+r is the radial position to their center of gravity, and ω1. ω2 is the rotational angular velocity, and ω2 is the case where the variable mechanism is attached. Also, l is the mass of the new wing, and r is the center of gravity position.

When increasing from 8 blades to 20 blades, take into consideration the 20% increase in chord length! 3g. Since the angular velocity will be halved with the new wing, we can set (ω1/ωZ)”=4.

r,/rt = 0.75, r*/r, = 1.08
Therefore, from 2(1), mt ” 1.7 m+ (21).

If the variable mechanism part is kept to about 1.7 times the original blade mass, it can withstand the strength. Next, the number of blades is 20, the circumferential speed is 120m8, the outer diameter is 3.2m, and the cruising Matsuha is 0.75m.
I tried to calculate the aerodynamics and thermodynamics of a high-speed turboprop with a shaft power of 2500kw (38shp/f L").The power and cruise speed were kept the same, and the number of blades was changed to 8 to make it a conventional turboprop. If you bring it closer, the peripheral speed will be 240, considering current aerodynamic and thermodynamic common sense.
At the same time, it was confirmed that the design would not work unless the height was increased to around m8. The results of these computer calculations are shown in FIG. 4 in comparison.

The features of the aerodynamic and thermodynamic design according to the present invention are that the solidity (=blade chord length/interblade distance) is large and almost the same in the propeller height direction, thereby making the contractile load even. The reason is that we were able to reduce the number to 1 or less.

The maximum value of the pressure difference between negative pressure and positive pressure for one dog can be determined by performing simple calculations on the equation of motion in the circumferential direction, and after making a few assumptions, ΔP = (9/2) V, " (1- exp (
-4-5in(φ/2)/σ(1+5in2r))
(3) becomes. ΔP is the pressure difference,
■, , is the axial velocity in front of the blade, φ is the deflection angle of the blade, and σ is the solidity, which is given by (blade chord length)/(distance between blades). ρ
is the air density and γ is the pitch angle. Since ΔP occurs when the blade operates, the value obtained by dividing equation (3) by the amount obtained by converting the circumferential velocity U into pressure is tentatively named the aerodynamic load coefficient η.

η=ΔP/(ρU”/2) (41Therefore, the propeller blade of a conventional high-speed turboprop is expressed by formula (4)
When calculated, the design was from η = 0.5 (tip) to η = 4 (1 piece).

Based on the above knowledge, the characteristics of the design according to the present invention will be described by comparing FIG. 4. First, at the blade tip (R = 1.6 m), T = 22° (invention) from γ = 43° (conventional type), so solidity σ = 0.2 (conventional type).
When increasing from σ to σ-1,5 (in the present invention), exp
The term a (1+5in2r) is between 0.29 and 1.
I can do it in 57. Due to this significant increase, the aerodynamic load coefficient η=0.50 can be maintained as it was even if the circumferential speed was halved.

On the other hand, at the blade root, σ=1 to σ=2 and the formula (
The value of [] in 3) was reduced from 0.5 (conventional type) to 0.3 (invention), and the inner radius was increased in order to not change η too much. Although FIG. 2 shows an example in which the radius is increased by 10/3 compared to the conventional type, by doing so, η=8 can be suppressed. However, the flow rate will be reduced by 8% due to the reduction in front surface area. In order to keep the thrust constant, it is necessary to increase the axial velocity, and the propulsion efficiency is 4.
% decrease is inevitable. Along with this, the circumferential speed νT approximately doubles in order to keep the shaft horsepower constant.

This means that the swirl loss increases by about 0.4% in terms of thrust. Furthermore, the cowling loss for housing the variable pitch mechanism is estimated to be about 0.8% in this case.

As a result, a turboprop aircraft using the propulsion method of the present invention will have a propulsion efficiency of 5% less than the conventional type currently under development, but will still have a propulsion efficiency of 20-20% less than a jet aircraft.
A propulsion efficiency improvement of 25% is obtained.

(Example) As shown in Figures 1 and 2A, B, and C, an example of the present invention rotatably supports 15 to 25 propellers 2 on the outer peripheral surface of a spinner I. Each propeller 2 is supported on the spinner 1 by fitting grooves of the propeller 2 provided along the pinch variable rotation center 5 of each propeller 2 into a plurality of first pivot shafts 4 fixed to the spinner 1. Let's do it. Each propeller 2
A second pivot shaft 6 is provided along the pinch variable rotation center 5 at the tip portion.

An annular cowling 7 is arranged around the spinner l.

The cowling 7 has a groove for rotatably receiving the second pivot shaft 6, and further accommodates a rod 8 pivotally connected to the second pivot shaft 6 therein. An annular first supporter 9 that is slidably supported in the circumferential direction with respect to the cowling 7 is disposed at the rear of the cowling 7, and one end of the rod 8 is pivotally supported by the first supporter 9. This first supporter 9 is held movably relative to the cowling 7 by a plurality of spaced spigot structures 10 on the rear edge of the cowling 7. A rack 1) and a pinion 13 are arranged at appropriate positions within the first supporter 9, and the pinion 13 is coupled to a motor 12 within the cowling 7. When the motor 12 is operated, the rack ti and pinion 13 rotate the supporter 9 relative to the cowling 7. This relative movement of the supporter 9 with respect to the cowling 7 causes the rod 8 to rotate about the second pivot shaft 6, thereby making the pinch angle of the propeller 2 variable. In order to obtain a desired pitch angle, the current applied to the motor 12 is adjusted by a system computer (also referred to as a system controller).

In the example shown in FIG. 2, the motor 12 is disposed on the spinner l side, but an electric or hydraulic motor may be disposed within the supporter 9 and the rod 8 may be displaced via the motor or an arm connected to the motor. . In this case, the motor operates in response to a power source from within the spinner 1 and a signal from the system controller.

Separately, as shown in FIG. 3, an abutment type rail 13 is arranged inside the supporter 9, and a bogie 13 pivotally attached to the tip of each rod 8 is engaged with this rail 12, and each bogie 13 is connected by an appropriate means. Connect them so that the interval is always constant. A small motor is arranged on one of the bogies 13, and a signal is sent to this small motor from the system controller in the spinner 1 to operate the motor and move each bogie 13 onto the rail 12 by a certain amount. Obtain the desired pitch angle.

As shown in Figure 6, the moment required to change the pitch of the propeller blade during operation is the difference in moment caused by the aerodynamic force around the center axis of the pinch change, since there is no swept blade.
The pitch-variable central axis requires less power. That is, it is possible to design the variable pitch mechanism according to the present invention to be small in size and weight.

(Effects of the invention) (1) It is no longer necessary to use an ultra-thin material with a swept angle, and the risk of damage due to blade flutter combined with low speed rotation is reduced.

(2) Since the entire propeller blade is in the subsonic range, the thickness of the blade can be increased and the structure is on the safer side.
Aerodynamically, it leads to improved efficiency and load. This allows the use of blade cascade design data that has been accumulated for jet engines, and can significantly shorten the time required for development.

(3) Since the rotation speed is 1/2 that of the conventional one, noise caused by rotation is reduced. Therefore, in the development of high-speed turboprop aircraft, there is no need to consider a new aircraft structure with soundproofing materials (it is possible to reuse conventional aircraft, leading to a significant reduction in development costs.

(4) Since there is no sweepback angle, the moment required for pinch adjustment can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an example of the present invention, and FIGS. 2A and 2B. Figure 0 is a partial exploded view of each part, Figure 3 is a plan view of another example, Figure 4 is a graph showing a comparison of aerodynamic design values, Figure 5 is an exploded view of the conventional example, and Figure 6 is a propeller blade. FIG. In the diagram: 1-...-- Spinner, 2-------
-Propeller, 4.6...--Pivot axis, 7
−・−・Cowling, 9−・−−1−−Supporter,
12--Motor, 13--Dolly. Figure 6

Claims (3)

[Claims] (1) 15-25 propellers are rotatably supported on a first pivot shaft fixed to the spinner of the turboprop, and a second pivot shaft fixed on the tip of the propeller is rotatably supported. and an annular cowling disposed around the tip, and a variable pitch mechanism including a part disposed within the cowling and connected to a second pivot disposed at the center of rotation of the pitch variable of the propeller. A high-speed turboprop that uses a variable mechanism to freely adjust the pitch angle of the propeller. (2) The high-speed turboprop according to claim (1), wherein the cowling is divided into front and rear parts in the axial direction, one of which is moved in the circumferential direction, and the pitch variable of all propellers is made the same. (3) The high-speed turboprop according to claim (1), wherein the pitch of the propeller is varied by a small electric or hydraulic motor in the cowling.