WO2009128743A1

WO2009128743A1 - Birotary propeller fan

Info

Publication number: WO2009128743A1
Application number: PCT/RU2008/000284
Authority: WO
Inventors: Виктор Иванович МИЛЕШИН; Сергей Владимирович ПАНКОВ; Евгений Прокофьевич ГЛАДКОВ; Игорь Константинович ОРЕХОВ
Priority date: 2008-04-17
Filing date: 2008-05-07
Publication date: 2009-10-22
Also published as: RU2367822C1

Abstract

The invention relates to aviation engine engineering, more specifically to fans for aircraft gas-turbine engines and makes it possible to reduce noise during the operation thereof. The technical result is achieved in the inventive birotary propeller fan, preferably without a cowling, which comprises two counter-rotating rotor wheels arranged one after another. In order to form the aerofoils of both rotor wheels, the required distributions of specified inlet angles, specified outlet angles and blade-camber angles, which are formed by the difference thereof, throughout a blade height, are rectified by algebraically adding up the specified outlet angles and correction angles defined by a relationship, the inlet angles being unchanged, thereby reducing the blade-camber angles at the peripheral sections of the blades and adequately increasing the blade-camber angles at the middle sections thereof.

Description

BIOTATIVE FAN

The invention relates to aircraft engine manufacturing, specifically to fans of aircraft gas turbine engines.

One of the main tasks in the development of aircraft engines, the design of which uses rotational propeller fans made up of two impellers that oppositely rotate relative to the axis of the propeller fan, is to achieve satisfactory acoustic characteristics of such propeller fans while ensuring the required aerodynamic and strength characteristics. The noise generated by the rotorotor fan, the level of which must be reduced to the required international standards, is a consequence of the aerodynamic interaction of the flow fields formed by the impeller blades rotating in opposite directions, as well as the interaction of the end vortices from the blades of the first wheel with the blades of the second wheel and the interaction of the end vortices from the blades of both wheels behind the second impeller. Due to the last two circumstances, the peripheral sections of the blades make a more significant contribution to the noise generated by the fan.

SUBSTITUTE SHEET (RULE 26) When designing the propeller fan blade, it is necessary to develop its geometry, which should provide the required distributions along the blade height of the degrees of increase in total pressure and air flow along the blade height. Directly, the shape of the blade is determined by the distributions found during the design of the blade height distribution of the required entry angles and exit angles for its mid skeletal surface of zero thickness and, therefore, the distribution of the bending angles of this skeletal surface, which are defined as the difference between the entry angles and exit angles. Then the skeletal surface is “dressed” with the necessary solid aerodynamic profiles with a shape varying in height of the scapula.

The present invention is applied to both impellers of a rotational rotor fan at the stage of blade profiling, before their skeletal surfaces of zero thickness, for which the distribution of the required entry angles, exit angles and bending angles are already found, it is necessary to “wear” aerodynamic profiles of the chosen shape in the cross sections of the blades .

A non-capotated birobot propeller fan is known, German patent DE JNk 3933776 dated October 10, 1989, consisting of two impellers oppositely rotating relative to the axis of the fan fan with blades made with aerodynamic profiles in cross sections. The traditional shape of the blades of both impellers allows us to conclude that these blades are profiled with an aerodynamic loading of profiles that varies slightly along the height of the blades to ensure approximately uniform distribution in height of the values of the degree of increase in total pressure created by the impellers. As a result, the disturbing effect on the flow of peripheral sections of the blades

SUBSTITUTE SHEET (RULE 26) It turns out to be as significant as other sections of the blades.

Therefore, the aerodynamic interaction between the blades of both impellers and the interaction of the end vortices remain intense, which leads to an increased level of noise created by the fan.

U.S. Patent No. 5,028,207 of July 2, 1991, consisting of first-placed first impeller and second impeller with vanes, in which the cross-section contours form aerodynamic profiles covering a skeletal surface of zero thickness for the profiling constructed at varying inlet angles, exit angles and profile bending angles varying along the height of the blades. In this rotor fan, the peripheral profiles of the blades of both impellers are made with significant bends, which indicates a significant aerodynamic loading of the peripheral sections of the blades, as a result of which the disturbing effect on the flow of peripheral sections of the blades is quite significant. Because of this, the aerodynamic interaction between the blades of both impellers and the interaction of the end vortices remain intense in this rotor fan, and, therefore, an increased level of noise occurs.

The technical task of the proposed technical solution is to reduce the noise level created by the birobative fan heater.

In the claimed technical solution is significantly weakened:

- the intensity of the aerodynamic interaction of the flow fields formed by the rotating blades of the impellers;

- the intensity of the interaction of the end vortices from the blades of the first wheel with the blades of the second wheel;

SUBSTITUTE SHEET (RULE 26) - the intensity of the interaction of the end vortices from the blades of both wheels behind the second impeller, which leads to a decrease in the noise level created by the impellers of the birotational fan heater.

The technical result is achieved by the claimed birotative propeller fan, mainly unoccupied, consisting of the first impeller and the second impeller with vanes located one after the other, in which the contours of the cross sections form aerodynamic profiles, covering a given shaped skeletal surface of zero thickness, which is built on varying along the height of the blades predetermined entry angles, predetermined exit angles and profile bending angles formed from their difference their wheels, to reduce the profile bending angle in the peripheral areas of the blades and increase the profile bending angle in the middle areas of the blades by changing the exit angle at a constant entry angle, the aerodynamic profiles in the cross sections of the blades located above the cross section 0.25 from the sleeve - 0.35 the height of the blades, perform with modified exit angles obtained by algebraic summation of the specified exit angles and corrective angles (a _c j), while the corrective angles (a _c j) are determined by the ratio: a _ci = {^ [(hr h _b USN-h _b )] ³ + c ₂ χ [(hi-h _b ) / (Hh _b )] ² + c ₃ χ [(h _i -h _b ) / (Hh _b )]} χa _i , where Ci is a constant for a third-degree term in the range -3.87 ÷ 0.0, C ₂ is a constant for a second-degree term in the range + 7.19 ÷ 0.0, C ₃ is a constant for a first-degree term, which is in the range of -2.92 ÷ 0,0,

SUBSTITUTE SHEET (RULE 26) a _c j is the correcting angle in degrees, algebraically summed with the given exit angle in the local cross section of the blade, h _b is the lower boundary of the height of the local cross section of the blade above which the specified exit angles are corrected and which is separated from the height of the sleeve cross section by 0.25 - 0.35 of the height of the blade, hj is the local value of the height of the local cross section of the blade, counted from the height of the sleeve cross section,

H is the height of the scapula,

& [- the formed angle of profile bending in degrees in the local cross section of the blade, which is equal to the difference between the specified angle of entry and the given angle of exit, measured from the axis of rotation of the fan.

A biotic propeller fan can be made capotated, that is, contain an apparent shell.

In the cross section of the blade, the contour of which is the selected aerodynamic profile, the cross section of the skeletal surface is a curved line passing inside the aerodynamic profile and having a bulge towards the back of the blade. The profile bending angle in the cross section of the blade is defined as the difference between the entry angle and the exit angle of this curve line, and these angles are counted relative to the axis of rotation of the fan.

The use of the left boundary values of the constants Ci ÷ c ₃ from their ranges of variation (ci = -3.87, c ₂ = + 7.19, c ₃ = -2.92) in the above formula for the inventive birotative fan heater results in blades of both impellers to the values of the correction angle a _ci ,

SUBSTITUTE SHEET (RULE 26) decreasing from the maximum positive value at the periphery, amounting to "0.40 from the required bending angle of the profile u in the peripheral cross section of the blade, to 0.0 in the cross section spaced from the sleeve by 0.70 - 0.74 blade height, and to the minimum a negative value of "-0.33 from the desired bending angle of the profile aj in the cross section spaced 0.48-0.54 times the height of the blade from the sleeve, and then increased to 0.0 in a boundary cross section spaced 0 away from the sleeve 25 - 0.35 scapular height. For cross sections located below this boundary section, the correction angle a _C i should be taken equal to 0.0.

An increase in the exit angles in the peripheral sections due to the addition of a correction angle to the desired exit angle for a constant entry angle and, therefore, a decrease in the bending angle of the profile in the peripheral sections of the blades of both impellers, reduces the aerodynamic loading of the profiles of the peripheral sections and, as a result, reduces the disturbing effect of these sections to the stream flowing around them and the weakening of the intensity of the end vortices formed by these sections. Since a decrease in the aerodynamic loading of the peripheral sections of the blades also causes a decrease in the values of the degree of increase in the total pressure created by these sections, then to compensate for the undershot of the degree of increase in the total pressure in the peripheral regions of the blades, the degrees of the total pressure created by the middle sections of the blades simultaneously increase, for which the bending angles increase adequately profile in these mid sections of the blades by subtracting the correction angle from the desired exit angle if the angle of entry.

Due to the predominant role of the aerodynamic loading of the peripheral sections of the blades in the creation of fan noise,

SUBSTITUTE SHEET (RULE 26) a decrease in the bending angles of the profiles in the cross sections of the peripheral sections of the blades of both impellers and the associated decrease in the aerodynamic loading of the profiles of these sections, despite an adequate increase in the loading of the profiles of the cross sections of the middle sections of the blades, reduces the intensity of the aerodynamic interaction of the flow fields formed by the perturbed the impact of the impellers, and the intensity of the interaction of the end vortices from the blades of the first wheel with the blades of the second wheel and the intensity of the interaction of the end vortices from the blades of both wheels behind the second impeller, and, therefore, the level of noise generated by the fan is reduced.

At zero values of the constants ci ÷ c ₃ corresponding to the right border from their range of variation, the correcting angle a _ci becomes equal to 0.0 for the peripheral and middle sections of the blades, and, therefore, the positive effect of the application of the claimed invention disappears.

Additionally, the essence of the invention is illustrated in the figures.

In FIG. 1 shows a view of the impellers of the claimed birotative propeller fan in a meridional section.

In FIG. 2 shows a view of a median skeletal surface of zero thickness for a blade of a first impeller.

In FIG. A local cross section along A-A is shown, FIG. 1, the blades of the first impeller at an arbitrary local height of the blade.

In FIG. 36 shows a local cross-section along A-A, FIG. 1, the blades of the second impeller at an arbitrary local height of the blade.

SUBSTITUTE SHEET (RULE 26) In FIG. 1, in a meridional section of the inventive birotative fan heater, the first impeller 1 and the second impeller 2 are shown, one after the other, rotating in opposite directions relative to the axis 3 of the fan. The blades 4 of the first impeller 1 and the blades 5 of the second impeller 2 can be made rotating respectively in the disks 6 and 7 relative to the radial axes 8 and 9 or fixed motionless in these disks. The input edge 10 and the output edge 11 of the blade 4, as well as the input edge 12 and the output edge 13 of the blade 5 may have varying shapes along the height of the blades, providing the blades with direct or reverse sweep. For the information in FIG. 1 shows the height 14 of the blade 4 of the first impeller 1 and the height 15 of the blade 5 of the second impeller 2, as well as the local heights 16 and 17 of the cross-sectional arrangement in the blade 4 and in the blade 5, respectively.

In the case of using a capotated birotative fan, it can be equipped with an external shell (hood) 18.

In FIG. Figure 2 shows, for example, a skeletal surface 19 of zero thickness that could be obtained by designing a blade similar to the blade 4 of the first impeller 1. As can be seen from this figure, the found distributions of the given angles of entry into the skeletal surface and the given angles of exit from it provide a continuous decrease in bending skeletal surface in the direction from the sleeve 20 to the periphery 21.

In FIG. For and 36 are given the local cross sections of the blades 4 of the first impeller 1 and the blades 5 of the second impeller 2 located at the local heights of these blades (section A-A of the fan, fig. L). The cross section of the skeletal surface that makes up the base of the scapula 4, and the cross section of the skeletal

SUBSTITUTE SHEET (RULE 26) the surface constituting the base of the blade 5, respectively, are the curved lines 22 and 23, drawn by strokes. The contours of the cross sections of the blades are the aerodynamic profiles 24 of the blades 4 and 25 of the blades 5, which are required to ensure aerodynamic characteristics. These aerodynamic profiles 24 and 25, when profiling the blades, “dress” on the cross sections 22 and 23 of the skeletal surfaces of the blades 4 and 5. respectively. FIG. For and 36, the angles of entry 26 and 27 into the cross sections of the skeletal surfaces of the blades 4 and the blades 5 and the angles of exit 28 and 29 of these cross sections, as well as the bending angles 30 and 31 of the cross sections of the skeletal surfaces of the blades 4 and 5, respectively, are shown. 26 and 27 and the exit angles 28 and 29 are counted from straight lines parallel to the axis 3 of the fan. The bending angles 30 and 31 of the cross-sections of the skeletal surfaces, equal to the differences respectively between the angle of entry 26 and the exit angle 28 of the blade 4 and between the angle of entry 27 and the exit angle 29 of the blade 5, are simultaneously the bending angles of the profiles 24 and 25, respectively, in the cross sections of the blades 4 and 5. It is obvious that an increase in the exit angle at a constant entry angle leads to a decrease in the bend angle of the profile in the cross section of the blade, and a decrease in the exit angle at a constant entry angle causes an increase in the bend angle of the profile.

Thus, the technical result in the inventive birotative fan heater is achieved due to the fact that after the design of the blades of the first and second impellers, the height distributions of the blades of the given entry angles and the specified exit angles of their skeletal surfaces are found, which provide the necessary distributions for the degree of increase total pressure, air flow and efficiencies, distribution of exit angles are adjusted by algebraic summation of the given

SUBSTITUTE SHEET (RULE 26) exit angles and corrective angles determined by the claimed ratio, in order to ensure a decrease in the bending angles of the profiles in the peripheral sections of the blades and an adequate increase in the bending angles of the profiles in the middle sections of the blades with constant entry angles. A decrease in the profile bending angle in the peripheral sections of the blades of both impellers reduces the aerodynamic loading of the profiles of the peripheral sections and, consequently, reduces the perturbing effect of these sections on the stream flowing around them and attenuates the intensity of the end vortices formed by these sections. The underestimation of the degree of increase in total pressure in the peripheral regions of the blades caused by the decrease in the bending angles of the profiles is compensated by the simultaneous increase in the degrees of increase in the total pressure created by the middle sections of the blades due to the increase in the angles of bending of the profile in these middle sections. Since the aerodynamic loading of the peripheral sections of the blades plays a predominant role in the creation of fan noise, by reducing the bending angles of the profiles in the cross sections of the peripheral sections of the blades of both impellers, despite the adequately increased bending angles of the profiles of the cross sections of the middle sections of the blades, weakening the intensity of the aerodynamic interaction fields of currents formed by the perturbed action of the impellers, and especially a significant weakening intensively interaction whith tip vortices from the blades of the first blade wheel of the second wheel and the intensity of tip vortices by the interaction of the blades of both wheels of the second impeller, and thus achieved reduction of noise level generated propfan.

SUBSTITUTE SHEET (RULE 26)

Claims

CLAIM

1. A rotational propeller fan, mainly unoccupied, consisting of the first impeller and the second impeller with vanes located one after the other, in which the contours of the cross sections form aerodynamic profiles covering a predetermined shaped skeletal surface of zero thickness, which is built from varying along the height of the blades predetermined entry angles, predetermined exit angles and profile bending angles formed from their difference, characterized in that in both impellers, to reduce the angle profile bending in the peripheral regions of the blades and increasing the profile bending angle in the middle regions of the blades due to a change in the exit angle at a constant entry angle, aerodynamic profiles in the cross sections of the blades located above the cross section 0.25 - 0.35 times higher than the blade , perform with the modified exit angles obtained by algebraic summation of the given exit angles and correction angles (a _ci ) ,. the correcting angles (a _ci ) are determined by the relation: a _ci = {^ [(hrh _b USN-h _b )] ³ + c ₂ x [(h _r h _b ) / (Hh _b )] ² + c ₃ x [(h _g _{_{h b) / (Hh b)}} ]} xa i5 wherein Ci - constant of the term of third degree, which is in the range -3.87 ÷ 0.0,

C ₂ - a constant for a member of the second degree, which is in the range + 7.19 ÷ 0Д

C ₃ is a constant for a first-degree term in the range -2.92 ÷ 0.0, a _ci is a correction angle in degrees, algebraically summed with a given exit angle in the local cross section of the blade, h _b is the lower boundary of the height of the local transverse section of the blade above which the correction of the given angles

SUBSTITUTE SHEET (RULE 26) output and which is 0.25 - 0.35 times the height of the blade, which is spaced from the height of the sleeve cross section, hj is the local value of the height of the local cross section of the blade, measured from the height of the sleeve cross section,

H - blade height, u - formed angle of profile bending in degrees in the local cross section of the blade, which is equal to the difference between a given angle of entry and a given angle of exit, measured from the axis of rotation of the fan.

2. The rotational fan heater according to claim 1, characterized in that it is made capotated.

SUBSTITUTE SHEET (RULE 26)