SU266475A1 - Jet Gas Turbine Blade - Google Patents

Description

Known blades of reactive gas turbines with a profile delineated by arcs of curves, for example, parabolas and lemniscates, arcs of circles and straight lines. However, they have a violation of the monotony of a change in the curvature of the contour, jumps in the curvature at the points of conjugation, which leads to additional losses caused by the acceleration of the flow in the zone of maximum curvature, followed by deceleration, leading to flow separation.

In the proposed blade, the profile from the entrance edge to the maximum thickness is outlined by circular arcs, and in the rest of the sections, hyperbolic spirals smoothly match with them.

When using the proposed blade, the terms for constructing a profile bypass are reduced, since the parameters of the spirals and arcs of the circles forming the profile, while respecting the initial gas-dynamic strength conditions, can be determined on electronic-digital computers.

The drawing schematically shows the construction of the contour profile of the blade.

The contours of the back and trough from the entrance edge (points 1 and 2) to the maximum thickness (points 3, 4) are formed by circular arcs of Ospinka and trough, one on each contour. In the rest of the area, the contours of the profile are formed by hyperbolic spirals (also one at a time on the back and the trough), which adjoin the circumferences without a jump in curvature.

The parameters of the spirals and circular arcs are determined on the computer, and the initial data for this are: | 3i and 2, respectively, the angles of entry and exit of the flow;

v2afl - reduced speed (or calculated pressure drop);

t is the lattice spacing (or its width is 5); G2 is the radius of the output edge; F - profile area (or its moment

resistance S.

Given the design conditions, the values of the following profile and lattice elements are determined: ort - the optimal lattice spacing;

6 - the angle of the limb; piK - constructive entry angle

p r1sp + 1kor

 2

where (3icn and PIKOII is the angle between the front of the lattice and the tangent to the profile at the junction of the input edge corresponding to the contour

P2eff - Effective exit angle Р2эf; gs5gp -, where Cz -

output channel width, "channel throat;

r2k - constructive exit angle,

o Rask + Rakor

P2K -.

where | 32sp, | 32cor is the angle between the front of the lattice and the tangent to the nanofile at the interface between the exit edge and the back and trough contour, respectively; - the relative position of the largest circle inscribed in the profile;

 - - max /

Where is the diameter | p of the largest circle, / is the profile chord; G1 - radius of the input circle

edges;

coi and Ш2 - wedge angle, respectively, at the entrance or exit;

where Cut PlKOp - RyuP, d2 R2kor - r2sp;

7 - profile installation angle in the grid.

In order to estimate these quantities, Obobsh, experimental screen sweeps of lattices and statistical data of their geometrical parameters are used.

The parameter and position of the backrest helix are chosen in such a way that the backrest mates with the exit edge, is observed

Angle P2eff and sustained by the CONSTRUCTURE (VI2); the magnitude of the Xashti radius and the position of the center of the circle (point P) are chosen so that the tangent to the back at the junction with the input edge is angled - and the conjugation of the arc with the helix is performed without a jump in curvature.

Therefore, the point P must coincide with the point of the spiral evolute, corresponding to the point on the spiral itself, the radius of curvature of which is equal to Ospinki (the evolute is depicted by a dash-dotted line).

The radius of the arc / trough, which together with the arc forms the inlet section of the profile, and the position of this circle are determined based on observing the angle and obtaining the maximum thickness max on the distance .Kull from the inlet edge.

The parameter and position of the spiral of the trough are selected from so that the entrance section has a direction corresponding to the angle p2k, and the junction of the spiral with the circumference of the trough

was carried out without a jump in curvature. (The spiral at the conjugation point n has a radius of curvature equal to / kyry, and the center of curvature

coincides with the point Q - the center of this circle).

In the lattice designed in this way, minimal losses will be obtained at sub- and near-sound pressure drops at

Bicex used in practice are the turning angles of the stream.

Subject invention

The blade of a reactive gas turbine with a profile defined by arcs of curves, characterized in that, in order to increase the efficiency at large angles of rotation of the flow, the profile from the entrance edge to the maximum thickness is outlined by circular arcs, and in the rest of the sections it is outlined by hyperbolic spirals that smoothly match them.