DE569022C - Condensation steam turbine for large amounts of exhaust steam - Google Patents

Description

The main difficulty in building large capacity steam turbines with utilization high evacuation consists in the extraordinarily large increase in the amount of steam at the end of its relaxation. the The size of the wheels and the shovel is limited by the permissible loads. Of the Steam must therefore flow through these wheels at a high axial speed, which cause considerable exit losses. Attempts have been made so far by various means been to reduce these losses and the highest possible performance of a turbine given Increase speed.

A well-known way is shown in Fig. 1. It consists in getting the steam In one of the last stages, the to varying degrees and from a plurality of wheels under work performance release to condenser pressure. A disadvantage of this arrangement is that it is cumbersome Arrangement of the guide and rotor blades 3 and 4, which generally have different cross-sections on both sides of the separating rings.

Another way of reducing leakage losses is by dividing up the Steam flow in different completely separate rivers, which under work on The condenser pressure can be released. Such turbines form a special class of high-quality, but also correspondingly more expensive turbines (longer overall length, etc.).

The present invention shows a way to get around with much simpler and cheaper Means to save part of the steam leakage losses. The invention consists in that the branched off steam flow (10 to 30 0/0 of that flowing through the turbine Amount of steam) is discharged through an opening on the way to the exhaust steam chamber, whose overall cross-section is dimensioned so that the amount of steam branched off from the pressure of the amount to be discharged is throttled to the pressure of the exhaust steam. This way appears initially uneconomical. It should therefore first be based on a simple calculation evidence of economic viability must be provided.

Let G be the total secondary amount of steam, (ß · G) be the amount of steam withdrawn, hence (ι - a) G be the amount of steam still flowing through the last stage; A ₀ is the heat gradient processed in the last stage; Let η be the efficiency of the last stage. The removal of steam results in a loss of power = 4.18 (ß «G) A ₀ · η. On the other hand, there is a gain in performance by reducing the outlet losses, which we calculate as follows: Im is the outlet loss from the last stage in heat units per kilogram of steam flowing through. It is proportional to the square of the

Exit speed. If the amount of steam is reduced, there is therefore a loss of exit per kilogram of steam in the ratio of

The losses in kilowatts are reduced to the squares of the amount of steam and are therefore (i - a) ² ha.

without removal 4.18 G-ha,

with removal 4.18 - (1 - a) G ■ (1 --- «) ² ha = 4.18 G (1 - a) ³ ha,

thus the gain in output = 4.18 G · ha [1- (1 - a) ³ ]. Is z. B. G = 20 kg / sec., A = 0.1, A ₀ = 20 WE / kg, η = 0.8, ha = 8 WE / kg, then the

Power gain 4.185 20 8 (1 - ο, α. ³ ) = i82 kW,

Power failure 4.18 0.1 20 20 0.8 = 134 -,

Net profit ... = 48 kW.

It follows that the removal of this amount of steam without work and utilization of the heat gradient results in an increase in economic efficiency without the use of special facilities, such as double blading or special annular dividing and guide walls within the blading. This applies to amounts of steam of. 10 to 30 o / _{o of} the total. Fig. 2 shows an example of the implementation of the concept of the invention. 1 represents the exhaust steam casing of a low-pressure turbine, 2 its rotor; 3 are guide vanes, 4 are blades; 5 is a channel through which the extracted steam enters the exhaust case; 6 is a throttle point by which the withdrawal amount is determined; 7 is an easily exchangeable or adjustable ring with which you can can change the opening in order to adapt the removal to the respective vacuum conditions. The guide and rotor blades differ from normal turbine blades at most in their angular position. However, they can be made in exactly the same way.

In the usual steam turbine designs, the long blades of the last relaxation stages work along their length with uneven circumferential and steam speeds. As a result, at the end of the Stage at different diameters different pressures. The harmful influences These uneven pressures are sought in a known manner by twisting the blades to counteract. In a turbine according to the present invention there is a decrease of the pressure from the inside to the outside, namely where part of the steam to Throttling is removed, useful because it reduces the throttling loss. You will so twist the blade so that a pressure decrease from the inside to the outside is guaranteed is.

The means for this purpose are the simplest imaginable: it is sufficient to use the voider Not to twist the rows of blades lying on the extraction point, or less to twist than the normal turbine would require. The outer blade parts then process accordingly their higher peripheral speed automatically creates a greater gradient. As essential The difference to known designs is that this gradient distribution accomplished without the help of any ring-shaped partition and guide walls arranged in the blading will.

The steam extraction need not be limited to the transition to the last stage. In many cases it will be advantageous to extract the steam in several stages, such as is shown for example in Fig. 3. The designations in this figure agree with ' correspond to those in Fig. 2.

Claims (3)

Patent claims: i. Condensation steam turbine for large amounts of exhaust steam, in which a part of the steam stream or several parts before the last stage or stages go into the exhaust steam space, while the rest is processed in the last stage or stages to the condenser pressure, characterized in that the The branched-off partial flow or the branched-off partial flows (10 to 30 o / _{o of} the total amount flowing through the turbine) are discharged on the way to the exhaust steam chamber through one or more openings, the total cross-section of which is dimensioned such that the branched amount of steam from Pressure of the amount to be discharged is throttled to the pressure of the exhaust steam. 2. Condensation turbine according to claim i, characterized in that the Throttle cross-section on the way to the exhaust steam chamber by replaceable or adjustable body, ζ. B. rings, in size according to the vacuum conditions can be changed. 3. condensation turbine according to claim ι and 2, characterized in that that the steam pressure the amount provided for the throttle point by the shape and position of the turbine blades last row or rows without the aid of annular dividing and guide walls already accepts within the blading. For this purpose ι sheet of drawings