SU70723A1 - Method of profiling workers and guide screw blades of steam and gas turbines - Google Patents

Description

The efficiency of the turbine depends on a number of design factors and, mainly, on the profile of the flow path of the stage. Usually, this profile is carried out at constant angles ai and Pa along the blade, and the angle p1 is made irresistible if the length of the blade reaches a certain value. This condition is reported in both the active turbine stages and the reactive ones. However, this neglects the inconsistency of the degree of reactivity along the blade, which is a consequence of the centrifugal effect that occurs in the channels of the flow passage.

The proposed new method of profiling workers and guide screw blades of steam and gas turbines with a blade angle variable in height of the blade of the working blade and an output guide allows an increase in efficiency. turbines.

A distinctive feature of this method is that the change of the mentioned angles along the blades is carried out according to the law of a parabola.

FIG. 1 shows the dependence of the angles ai, pi and p2 and the degree of reactivity g on the peripheral speed and along the blade; FIG. 2 shows an approximate profile of a working blade; FIG. 3 is an exemplary profile of the guide rail.

The law of variation of the angles oi, Pi and PO and the degree of reactivity r along the blade is subject to the condition of constant efficiency of Lsch or n, - and the condition of the absolute velocity Cz along the blade, and the direction Cz must be axial.

From the first of these conditions depends on the quantitative change in the angles ai, p1 and Pa, the degree of reactivity r along the blade and other values characterizing the turbine stage.

No. 70723-2 -

The second (additional) condition is the device for the direction of the absolute velocity of the gas (steam) from the rotor blades.

This direction can be chosen either axially or at an angle other than 90 °.

If there is a constant Л, - (Пц,) along the blade and the axial direction C at the exit, the quantitative change in angles Pi and pa and the degree of reactivity along the blade is determined by the following equations:

2vsr20sr

e (l-cp) 7i;

(. g ,.

E (1 -) - Y);

circumferential speed

adiabatic velocity

absolute rate of gas release from rotor blades.

coefficient taking into account losses from friction and ventilation

ijj - coefficients (speed)

R -fi, x

S

13) / С - polytropic indicator; / -gas consumption; V - power turbine stage

With non-axial output from the rotor blades and with P; i const along the blade is the analytical dependence of the angles ai, Pi, and p2 of the degree of reactivity r on: and (blade length) ina.

The highest value 1 corresponds permanently to its value along the blade and to the axial exit Cs from the working blades. Then it will take place:

1.C2 const along the shoulder blade.

2.h ,, const along the shoulder blade.

3. Circulation of qi inlet A const along the shoulder blade.

4. Circulation of qi at the output of G2 const along the scapula.

5.Cia const along the shoulder blade.

6.Soy const along the shoulder blade.

The pressure and temperature of the gas (vapor) at the exit from the working blades are constant along the blade.

The angles ai, PI, and p2 change along the blade, while a and pj increase from the root to the periphery of the blade, and 2 decreases. The degree of reactivity g const along the shoulder blade.

Subject invention

The method of profiling the working and guiding helical blades of steam and gas turbines with a variable in height of the blade by the angle of entry of the working blade and the exit of the guide, characterized in that the variation of said angles along the blades is carried out according to the parabola law.

FIG.

90

4 Fig.Z