SU1222859A1 - Exhaust outlet of steam turbine - Google Patents

Description

The invention relates to turbine engineering and can be used in the design of low pressure steam turbine parts.

The purpose of the invention is to increase efficiency by c-lowering the unevenness of steam flow parameters beyond the last stage in a wide range of turbine operating conditions.

FIG. 1 shows the exhaust pipe, a longitudinal section; in fig. 2 - the same cross section ..

The exhaust pipe contains an axial diffuser 1 with an internal 2 and external 3 rims, a desuperheater 4 with assembly chambers 5 and 6, installed equidistantly to the surface of the external contour 3 of the diffuser.

 The tube bundle 7 of the desuperheater 4 is divided by additional collecting chambers 8-10 into sections 11-14. All collecting chambers 5 ,. 6, 8, 9, 10 are equipped with unions 15 with locking and regulating bodies 16 - 20 installed on them.

The exhaust pipe of the steam pipe works as follows.

When the turbine operates at the nominal mode (with the axial steam inlet into the exhaust pipe), the zone of maximum pressure behind the impeller after the stage has passed is in the plane of symmetry from the side opposite to the steam outlet from the exhaust pipe. The cooling medium is fed through the control unit 18 into the collecting chamber 9 into the sections 12 and 13 of the tube bundle 7 of the desuperheater 4. The cooling medium is drained from the collecting chambers 8 and 10 through the locking and regulating bodies 17 and 19.

The steam washes the cooled sections 12 and 13 of the tube bundle 7, condenses, and its volume decreases from the nominal one. For example, on mode

consumption, which leads to a decrease in pressure in this zone and, accordingly, to the equalization of the pressure distribution behind the impeller of the last stage and increase the efficiency of the turbine.

When the turbine operates in modes other than nominal, the zone maxi50

with a relative volumetric flow rate of 60% of the nominal at the nominal frequency of rotation, the efficiency of the last stage with the proposed outlet nozzle increases by 1.5% absolute 5% relative. Circumferential pressure unequalness behind the impeller in the last stage decreases by 2–3 times

The maximum pressure behind the impeller of the last stage is shifted in the circumferential direction by an angle due to the mode of operation of the turbine: when the load decreases, in the direction opposite to the direction of rotation of the turbine, with increasing load, the direction of rotation of the turbine.

For example, when shifting the zone

the maximum pressure in the region of the collecting chamber 8, the coolant is supplied through the valve 17 to the collecting chamber 8, and the discharge from the collecting chambers 5 and 9 through

the shut-off and regulating bodies 16 and 18. The steam washes the cooled sections 11 and 12 of the tube bundle 7, condenses, decreases its volume flow, decreases the pressure in this zone,

which leads to the alignment of the distribution. The division of pressure behind the impeller of the last stage, to an increase in the efficiency of the turbine in this mode.

Thus, for effective operation of the exhaust pipe, it is necessary that the position of the zone of intense condensation of steam coincides with the position of the zone of maximum pressure.

This can be achieved by manipulating the locking and regulating bodies 16-20 and putting into operation the sections of the tube bundle of the desuperheater corresponding to the mode, and also performing the desuperheater 4 behind the axial diffusor 1 equidistant surface of the external bypass 3 of the radial diffuser 1, i.e. displacement of the zone of maximum pressure, and thus not disturbing the aerodynamics of the flow part. The greatest effect is achieved on turbine units, the last stages of which for a long time operate in modes other than

50

with a relative volumetric flow rate of 60% of the nominal at the nominal frequency of rotation, the efficiency of the last stage with the proposed outlet nozzle increases by 1.5% absolute, 5% relative. Circumferential pressure unevenness behind the impeller is. the last step is reduced by 2-3 times.

17

15.

sixteen

FIG, g

Claims (1)

EXHAUST TUBE OF A STEAM TURBINE, containing an axial radial diffuser with internal and external contours, prefabricated chambers with fittings and a steam cooler located behind the diffuser, the tube bundle of which is connected to the prefabricated chambers, characterized in that>. in order to increase efficiency by reducing uneven steam flow parameters behind the last stage in a wide range of turbine operating modes, it is equipped with at least τρβγ four additional prefabricated chambers dividing the tube bundle into sections, and shut-off and regulating bodies mounted on the nozzles, the desuperheater is placed equidistant to the surface of the outer contour of the diffuser, while all prefabricated chambers are placed inside the pipe. Figure 1