FI82291B - Method for cooling the blades in a steam turbine housing without the use of steam - Google Patents

Description

1 82291

A method for cooling the blades of a steam turbine housing in a non-steam operating mode

The invention relates to power plant technology and more particularly to methods for cooling the impeller of a steam turbine housing in a non-steam operating mode.

The method of the invention can be applied to the production of new steam turbines as well as to the renewal of 10 currently used turbines if the entire turbine or its individual nests are to be operated in a steam-free operating mode.

In the non-steam operating mode, the heat distribution of the cooling steam in the fan differs substantially from the distribution with a relatively higher application rate (nominal amount of steam). In this case, the heat resistance of the blade elements of the housing does not allow the sudden commissioning of the housing and the generation of a relatively large torque on the rotor shaft. Steam should be fed in stages at certain intervals to heat the wing-20 elements and this considerably increases the time required to change the housing from a non-steam operating mode to a nominal amount of steam.

A method according to the countercurrent principle for cooling the impeller of a steam turbine-25 n housing in a non-steam operating mode is known from the prior art (cf. the article "Temperature Condition of Blading of Turbine P-50-130 Operating in Steamless Mode", written by Makhovko Ju.

E. et al., Published in "Teploenergetika" No. 10, 1975, pp. 30-33, by the publishing house "Energia".

According to this method, the shut-off valves are closed to interrupt the supply of steam from the boiler to the turbine housing and to close the tap steam pipes leading to the heaters, and then the cooling steam is led to the outflow part of the housing. The cooling steam 35 flows through the housing impeller towards the steam inflow section 2 82291, where it is discharged into a low-pressure space consisting of a condenser, a fixed low-power steam collector and the like.

During the cooling process, the temperature of the cooling steam 5 should be measured in the steam inflow part belonging to the housing and should be close to the temperature at which the housing operates with operating steam, and depending on this temperature value the cooling steam in the steam inlet section is flow cross-section.

With such cooling, curve "A" (Fig. 1), which shows the temperature distribution in the vane along the length of the housing, differs substantially from curve "B", which shows the temperature distribution with a higher amount of operating steam, which over time increases the time required to change the housing to nominal steam. The curves describing the dependence relationship are shown in the following coordinates: ordinate axis - temperature, ° C; 20 abscissa shaft - nest zones.

The object of the invention is to provide a method for cooling the impeller of a steam turbine housing in a non-steam operating state, according to which the cooling steam is lowered to a low pressure state so that the cooling-steam steam temperatures in the non-steam housing impeller can be brought close to the operating steam temperatures.

This is achieved by a method for cooling the impeller of a steam turbine housing in a non-steam operating mode, in which cooling steam is introduced into the outflow section of the housing and flows through the impeller to the inlet section of the steam. and depending on this temperature value, the cooling steam flow rate is adjusted at its outlet, according to the invention the cooling steam is further lowered from the housing intermediate to the low pressure space, the cooling steam temperature is measured from the housing outlet and flow rate.

The cooling steam is preferably led from the housing to one of the 10 turbines from the heaters, which operates as a low pressure space.

In this case, the heat of the cooling steam is used to heat the feed water that passes through the heater to the boiler.

By using the method according to the invention for cooling the blade of a steam turbine housing in a non-steam operating mode, the operation of the housing can be changed virtually in the blink of an eye from non-steam to nominal steam, which improves turbine control at start-up and fuel economy.

When using the method according to the invention, it is also possible to utilize the heat transferred from the turbine heat exchanger system to the boiler in the start-up phase for heating the feed water, which contributes to improving fuel economy.

The invention will now be described in more detail by means of some application examples thereof and with reference to the accompanying drawings, in which: Fig. 1 shows curves illustrating longitudinal cooling temperature variation in a turbine head vane using a known method and a method according to the invention; Fig. 2 schematically shows a steam turbine a cooling steam outlet pipe leading from the intermediate part of the housing 35 to the condenser.

Fig. 3 82291 Fig. 3 corresponds to Fig. 2 except that the cooling steam outlet pipe leads from the intermediate part of the steam turbine housing to the heater.

The method for cooling the civilization of the steam turbine-5 bin housing in the non-steam state is carried out as follows. To change the housing 1 (Fig. 2) to operate in the steam-free state, the shut-off valve 2 separating the inlet part of the housing 1 from the boiler (not shown in the drawings) is closed and the shut-off valves 10 3 installed in the turbine housing 1 intermediate steam pipes 4

A shut-off valve 6 is then opened, which is mounted in a pipeline 7 connecting the outlet-15 of the housing 1 to a cooling steam source (not shown). An after-heat boiler or other steam generator with suitable operating values can be used as the steam source.

Not all of these steam sources are described, as they are not covered by the claims, and may be of any type suitable for the purpose.

At the same time, a control valve 8 is opened, which is arranged in a pipeline 9 connecting the steam inflow part belonging to the housing 1 to a low-pressure space, which may consist of a turbine condenser or other tank with a significantly lower pressure than the turbine housing.

With the aforementioned shut-off valves in the position shown, the amount of steam 30 cooling the impeller of the housing 1 should be such that the temperature in the steam inflow part belonging to the housing 1 is the same when the housing operates with both non-steam and higher operating steam. The approximate uniformity of temperatures is shown in Figure 1 in the range "a".

5 82291 The flow rate of the cooling steam at the steam outlet belonging to the housing 1 is adjusted by changing the position of the control valve 8 depending on the temperature of the cooling steam measured at this outlet. The variation of the steam temperature in the housing vane in the non-steam operating mode is shown by curve "A" in Figure 1. Curve "B" in Figure 1 shows the variation of the steam temperature in the higher operating steam zones of the housing. with the flow rate, curves "A" and "B" should be brought closer to each other.

In order to reduce the temperature differences between curves "A" and "B", the intermediate part of the housing is connected by a pipeline 11 to a low pressure space 10. In order to change the amount of steam passing through the pipeline 11 according to the cooling steam temperature measured from this outlet, a control valve 12 is installed.

When the control valves 8 and 12 are open, the amount of cooling steam in the steam outflow section 20 belonging to the housing increases. Therefore, the zones of the housing 1 located between the ejection part of the housing 1 and the outlet accessing the cooling pipe from the intermediate part to the pipeline 1 are strongly cooled.

The temperatures in these zones are shown in Figure 1 by curve "C". As the temperature of the cooling steam decreases considerably in the region of said zones and becomes closer to curve "B", in order to keep the temperature level of "a" equal, it is necessary to partially reduce the flow of cooling steam in line 9. The temperature variation of the cooling steam in the impeller of the housing 1 between the outlet of the intermediate part and the inflow part is shown in Figure 1 by the curve "C2".

In order to bring the cooling steam temperatures closer to the operating steam temperature and to move the curve "C2" closer to the curve "B", other outlets can be provided for the cooling steam 6 82291 in the zones in the intermediate part of the housing 1.

In order to utilize the heat of the cooling steam discharged from the intermediate part of the housing 1, one heating of the turbine-5 5 (Fig. 3) is used as a low-pressure space.

This heater is connected to the intermediate part of the housing 1 by a champion steam line 13, in which, in addition to the shut-off valve 3, a control valve 12 is mounted.

To change the housing 1 to the non-steam operating mode 10, the shut-off valves 2 and 3 are closed, then the shut-off valve 6 is opened and the cooling steam is led to the outflow part of the housing 1. When the control valves 8 and 12 in the pipelines 9 and 11 are opened, the cooling steam enters the low pressure space 10. At the same time, the temperature of the cooling-15 steam at its outlets should be constantly monitored and the flow cross-sections of the control valves 8 and 12 should be changed.

Thus, the temperature distribution of the housing 1 in the non-steam operating state is stabilized close to the temperature distribution prevailing in the housing operating with a relatively higher amount of operating steam. This allows the housing to be changed in almost no blink of an eye from a steam-free operating mode to a high operating steam flow rate, i.e. a nominal steam volume.

In order to reduce the cooling steam from the intermediate part to the heater 5 of the turbine 25, the cooling of the impeller of the housing 1 is carried out in much the same way as described above. In this case, the shut-off valve 3 of the pipeline 13 remains closed and the heat of the cooling steam is used in the heater 5 to heat the feed water.

Claims (2)

7 82291 1. A method for cooling the impeller of a steam turbine housing in a non-steam operating mode, wherein 5 cooling steam is introduced into the outflow section of the housing (1) and flows through the impeller into the steam inlet section of the housing. 1) and depending on this heat-10 space value, the cooling steam flow rate is adjusted at its outlet, characterized in that cooling steam is further discharged from the intermediate part of the housing (1) to the low pressure space (10), the cooling steam temperature is measured from the intermediate housing (1) 15 and depending on this temperature value, the cooling steam flow rate is adjusted at this outlet point and at the same time the cooling steam flow rate to be removed from the inlet portion of the housing is reduced. Method according to Claim 1, characterized in that the cooling steam is discharged from the intermediate part of the housing into one of the turbine heaters (5) which operates as a low-pressure space. β 82291 1. A method for the preparation of a pair of tubes and a pair of tubes, the color of which does not exceed 5 times the value of the number of legs and the number of legs (1) and the genome of a group of legs in the form (10) with the reduction of the temperature and temperature of the village in the same way as in the case of (1) 1) and in the case of (10) with the reduction of the temperature, the temperature in the village is at least 15 times the temperature (1) husets änginloppsparti. 20 2. A method according to claim 1, which can be used as a first step in a turbine batch according to a turbine paint (5).