CN100582466C - Method for suppressing flow separation in transition segment using guide vane - Google Patents

Abstract

The invention relates to a method for inhibiting flow separation in a transition section of a compression system of an engine of a low-bypass aerial turbofan by using a guide vane. The method comprises the following steps: placing the guide vane at a first curved conduit on the inner wall of a transition section of an air compressor, and forming a vane force with gradient opposite to that of the prior pressure at the curved conduit of the transition section through changing a peripheral included angle of a laminated line and a radial line of the guide vane, so as to reduce pressure gradient of the flow direction at the curved conduit, and inhibit the flow separation in the transition section. Because the method can inhibit the flow separation in the transition section, the method can increase bending degree of the transition section, so as to reduce the length of the transition section. At the same time, because the guide vane is placed in the transition section, the method saves space occupied by the prior guide vane, and is favorable for reducing the length of the whole air compressor. The length of the transition section is estimated to be shortened by about 20 percent by adopting the method and the method contributes to the thrust mass ratio of the engine by about 1 percent.

Description

Utilize guide vane to suppress the method for flow separation in the changeover portion

Technical field

A kind of method of utilizing guide vane to suppress flow separation in the little bypass ratio aerial turbo fan engine compression system changeover portion, this invention can effectively reduce the length of changeover portion between aerial engine fan and the high-pressure compressor.

Background technique

Turbofan engine is the main flow of modern aeroengine, and little Bypass Ratio Turbofan Engine is the main flow of ordnance engine.And all exist changeover portion between the fan outlet of nearly all little bypass ratio turbofan and the high-pressure inlet.And along with the progressively raising that the aeroengine thrust weight ratio is required.The length that reduces changeover portion can effectively improve the compact degree of turbofan engine, improves its thrust weight ratio.

In recent years, the turbofan engine changeover portion has caused everybody attention, but research concentrates on the civilian motor of big bypass ratio.For example, Europe had started the pneumatic project of high load changeover portion at big bypass ratio motor in 2004, and its target is that transition section length is reduced 20% or increase the drop between 20% high low pressure or increase the spreading rate of 20% changeover portion under the constant situation of transition section length.And the changeover portion of little Bypass Ratio Turbofan Engine is compared with the changeover portion of big Bypass Ratio Turbofan Engine, and the design of its changeover portion is more precipitous, and easier internal face at changeover portion produces flow separation.And changeover portion is the vitals that connects fan and high-pressure compressor, and its quality that flows will have influence on the performance of downstream high-pressure compressor, simultaneously also can and upstream fan between produce interference, influence the performance of fan.Therefore,, also be one of target that artificers pursued how realizing guaranteeing again when transition section length shortens that mobile performance in the changeover portion does not descend and has important engineering application value.

The changeover portion internal face is easy to generate separation, mainly is because there is bigger contrary pressure gradient in it along flowing to.At first bend place of internal face, convex curvature reduces this place's force value, and pressure then increases gradually thereafter, and the recessed curvature at the second bend place makes pressure increase to maximum again, therefore between first bend of internal face, exist bigger pressure reduction, have bigger contrary pressure gradient.

And the method that is used to shorten transition section length at present is mainly and introduces the swirler that uses originally with aircraft wing.Arrange that at the changeover portion internal face swirler can higher the mobile of main flow zone be involved in energy in the changeover portion internal face low energy boundary layer that is tending towards separating, thereby suppress the separation of changeover portion.This method in the flow separation, has been introduced extra loss in suppressing changeover portion, introduce optional feature simultaneously, has increased system complexity, also increases the weight of motor simultaneously.

Summary of the invention

A kind of method that suppresses flow separation in the little bypass ratio aerial turbo fan engine compression system (see figure 1) changeover portion.This invention places first bend place (see figure 2) of gas compressor changeover portion inwall with guide vane, utilizes blade near the radial force of the fluid changeover portion internal face to be suppressed the flow separation of changeover portion.By changing the footpath vector product superimposing thread of traditional blades, make long-pending superimposing thread of blade and radial line upwards be the certain included angle (see figure 3) in week, even blade pressure surface tilts to internal face, blade will apply radial force to the internal face of changeover portion runner like this, thereby produce the pressure gradient opposite with BLADE FORCE, this pressure gradient can partially or completely be offset crooked by changeover portion internal face runner and pressure gradient that form, therefore, can effectively improve the force value at changeover portion inner curve place, thereby reduce changeover portion inwall longshore current to the pressure gradient (see figure 4), reduce the risk of flow separation in the changeover portion greatly.Long-pending superimposing thread of blade and radial line are the key parameters of this invention at the angle that makes progress in week, can control near the size of the force value bend by regulating this parameter.Because when the angle of long-pending superimposing thread of guide vane and radial line is excessive, to produce comparatively serious Radial Flow in the guide vane, influence the mobile performance of guide vane, therefore, for changeover portion is flowed and guide vane in flow both compromise consideration, the CLV ceiling limit value with this angle among the present invention is made as 40 °.Simultaneously, if changeover portion maximum curvature position is during too near the leading edge of guide vane or trailing edge, with the parcel degree deficiency that makes blade to bend, thereby the effect that influence control separates, therefore, the present invention further limits the position of guide vane, and the maximum curvature point of first bend of changeover portion is positioned at apart from 0.2～0.8 times of guide vane shaft orientation string of guide vane leading edge strong point.

Because this method can suppress flow separation in the changeover portion, therefore can increase the degree of crook of changeover portion, reduce transition section length.Simultaneously, this method is positioned over guide vane and has also effectively utilized the changeover portion space in the changeover portion, and its benefit is appreciable.It is about 20% estimate to adopt after this method transition section length to shorten, thereby makes the motor thrust weight ratio improve about 1%.

Description of drawings

Fig. 1 is the little bypass ratio aerial turbo fan engine compression system stream sketch that the present invention is suitable for.

Fig. 2 is a changeover portion structural representation of the present invention.

Fig. 3 is that the A-A of guide vane of the present invention is to view.

Fig. 4 is the comparison diagram that is suitable for the present invention front and back changeover portion internal face pressure distribution.

Among the figure: 1. changeover portion internal face 2. changeover portion casings 3. guide vanes 4. load support plates 5. shunting rings

Embodiment

For more clearly describing the present invention, this embodiment is an example with a method that suppresses flow separation in the changeover portion, and the present invention is further illustrated in conjunction with the accompanying drawings.

It at first is the mounting point of determining guide vane.In this example, the changeover portion structure is seen Fig. 2, and the total length of changeover portion is 0.35m, and the axial chord length of guide vane is 0.06m.The maximum curvature of first bend of changeover portion is positioned at from changeover portion import 0.064m place, be located at apart from 0.6 times of axial chord length of guide vane leading edge position, then the guide vane leading edge is positioned at from the position of changeover portion import 0.04m, and trailing edge is positioned at from changeover portion import 0.1m place.

Next is to determine that long-pending superimposing thread of guide vane and radial line are at the angle that makes progress in week.In this example, meridian plane airspeed W _mBe 180m/s, the minimum profile curvature radius R of first bend place _mBe 0.08m, circumferential speed C _uBe 180m/s, the blade root radius r is 0.325m, so circular rector C _uR is 58.5m ²/ s, circular rector keeps equating that outlet circulation is 0 on all blade heights in this design, and in circular rector even variation in blade, then:

$F_b=\frac{W_m}{r}\frac{d\left(C_{u}r\right)}{\mathrm{dz}}=\frac{W_m}{r}\frac{\mathrm{\Δ}{C}_{u}r}{\mathrm{\Δz}}=180*975/0.325=540000$

And

$\frac{\∂p}{\∂r}=\frac{\mathrm{\ρ}{W_m}^2}{R_m}=0.922*180*180/0.08=373410$

Therefore,

$\sin {\mathrm{\β}}_d=\frac{\∂p}{\∂r}/F_b=373430/540000=0.6915$

Thereby

β _d＝43.75°

Because β _dSurpass 40 °, may cause producing comparatively serious Radial Flow in the guide vane, worsen flowing in the guide vane.Therefore, for the purpose of safe, the angle β with long-pending superimposing thread of guide vane and radial line in this example is chosen to be 35 °.

Long-pending superimposing thread of definite guide vane position of demonstrating above and guide vane and radial line in the process of angle that makes progress in week, be two key steps of this method.After implementing said method, can guarantee that the pressure gradient in the changeover portion is significantly reduced, thereby suppress the flow separation in the changeover portion.

Claims (3)

1, a kind of method of utilizing guide vane to suppress flow separation in the little bypass ratio aerial turbo fan engine compression system changeover portion, wherein this changeover portion is made up of internal face with two bends that connects fan outlet wheel hub and high-pressure compressor import wheel hub and outer casing, and be furnished with load support plate, shunting ring and guide vane in this changeover portion space

The method is characterized in that, guide vane is arranged in first bend place of changeover portion internal face, and make the long-pending superimposing thread of guide vane and radial line in a certain angle in a circumferential direction, definite method of this angle is as follows:

(1) changeover portion bend place radial pressure determination of gradients

$\frac{\∂p}{\∂r}=\frac{{{\mathrm{\ρW}}_m}^2}{R_m}---\left(a\right)$

Wherein p is a pressure, and r is a radius, and ρ is a gas density, W _mBe meridian plane airspeed, R _mMinimum profile curvature radius for first bend of changeover portion;

(2) guide vane BLADE FORCE F _bDetermine

$F_b=\frac{W_m}{r}\frac{d\left(C_{u}r\right)}{\mathrm{dz}}---\left(b\right)$

C wherein _uCircumferential component velocity for air-flow;

(3) angle of long-pending superimposing thread of guide vane and radial line is determined

If BLADE FORCE is lucky and runner radial pressure gradient is offset, then

$F_b\sin {\mathrm{\β}}_d=\frac{\∂p}{\∂r}$

Promptly

$\sin {\mathrm{\β}}_d=\frac{\∂p}{\∂r}/F_b$

Thereby obtain

${\mathrm{\β}}_d=\arcsin (\frac{\∂p}{\∂r}/F_b)---\left(c\right)$

β wherein _dBe the angle of long-pending superimposing thread of the guide vane of the best and radial line, but consider that this angle is at β _dNear still can play a role, so the span of the actual angle β of long-pending superimposing thread of guide vane and radial line suitably enlarges, and gets 0＜β≤1.5 β _d

2, method according to claim 1 is characterized in that, the CLV ceiling limit value of the actual angle β of long-pending superimposing thread of guide vane and radial line is 40 °.

3, method according to claim 2 is characterized in that, the maximum curvature point of first bend of changeover portion is positioned at 0.2～0.8 times of axial chord length of guide vane position apart from the guide vane leading edge.

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