SU985330A1 - Method of monitoring steam turbine rotor metal damage degree - Google Patents

Description

one

The invention relates to a power system and can be used in the operation of steam turbines of power plants for KOHTpoj; iH for the state of the metal of the rotors. .

Methods are known for monitoring the accumulation of damage to the metal of a steam turbine rotor by measuring the inlet steam temperature during turbine operation, converting this temperature to the temperature value of the rotor metal and determining the damage increment over the turbine start-stop cycle based on the radial temperature difference specified by the cycle, rotor l.

These methods do not allow sufficiently reliable control of damage accumulation.

A: The closest to the proposed method is to control the accumulation of damage to the metal of the rotor of a steam turbine by measuring the input.

steam temperature during turbine operation, converting this temperature to the rotor metal temperature value, determining the obtained value and cooling time after stopping the steam supply at the characteristic starting temperature of the rotor metal and determining the damage increment per cycle starting the turbine islands for a given maximum temperature differences along the rotor radius 2.

The disadvantage of this method is the reduced reliability of the controller because of the need to simulate the heating of the rotor in the control process using an analog computing device.

The purpose of the invention is to increase the reliability of control,

This goal is achieved by preliminarily determining the dependencies between the highest characteristic temperature difference over the radius of the rotor and the characteristic prestarting temperature of the rotor metal for a cycle from different thermal conditions, and in the control process they determine the maximum characteristic temperature difference over the radius of the rotor based on the cycle. specified dependencies. FIG. 1 shows the scheme for implementing the proposed method; in fig. 2character of empirical dependencies used in the method. The circuit (Fig. 1) includes successively connected sensor 1 of the steam inlet temperature (in front of the cylinder), functional converter 2, which sets the characteristic T1 temperature of the rotor metal during turbine operation, the first breaker 3, the aperiodic link 4, the second the breaker 5, the memory element 6, the block 7 for determining the highest value of har, the actor temperature difference over the rotor radius, the functional converter 8 and the metal damage accumulation counter 9. The breakers 3 and 5 are connected to the turbine state sensor 10, which uses an end position indicator of the valves on the steam supply to the turbine or the generator circuit breaker. The functional converter 2 in its simplest form can be made as an adder with a given offset relative to the measured 1 sensor steam temperatures. And the periodic link 4, which can be made in the form of an integrator covered by negative feedback, reproduces the rotor cooling characteristic t (t) —the change in temperature t of the metal with time t. The effect of the ambient temperature, due to heat exchange which cools down, is taken into account by the introduction of additional displacements in converter 2 and determination unit 7, which in the simplest case reproduces the previously found non-linear empirical relationship t (t) between the most characteristic temperature difference d t t over the radius rotor and the characteristic pre-temperature t of the metal rotor. The functional converter 8 determines the increment of the characteristic defect size l B per cycle, proportional to the fourth power maximum 985-3 04 per cycle, the value of tensile stresses equal to the sum of the constant value of the stresses from the centrifugal forces at the nominal rotation frequency and maximum value , temperature stress, proportional to the difference D t temperature. The value of L is also proportional to the square of the current size of the defect, which can additionally be entered by the setting device 11. To the determination unit 7, the steam temperature sensor 1 can be additionally connected via the logic element 12 to take into account the influence of the start technology. The schematic diagram shown in FIG. 2) can also be considered as a block diagram of the determination of damage accumulation using a computer system. FIG. 2 shows the character of the dependences t (t), At (t). The method is carried out as follows. When the steam supply to the turbine ceases, as indicated by sensor 10, the characteristic determination of the starting temperature of the rotor metal during the cooling process starts from the initial level set by converter 2 according to the steam temperature measured by sensor 1 before the steam supply to the turbine stops. In the circuit (FIG. 1), this is done by opening the first switch 3 and connecting the second switch 5 to the aperiodic element output to the input of memory element 6. When steam is supplied to the turbine by the signal from sensor 10, the aperiodic element is disconnected by the switch 5 from memory element 6. From the thus obtained temperature value t of the rotor metal, before the start of the start, in block 7 of the determination, the maximum value of the characteristic temperature difference along the rotor radius during the start-up stop cycle is found. This value can be corrected depending on the temperature of the steam in front of the cylinder at the end of the start, fixed by logic element 12, for example, as a result of the stabilization of the level of steam temperature measured by sensor 1 for a given time interval. From the obtained value of At, the value of is determined by the functional transformation in the converter 8.

termination of the characteristic size of the de facto per cycle sent to the SL counter. The organization of such a control will ensure timely prevention of the unstable development of a defect that creates the risk of brittle destruction of the rotor.

Claims (1)

1.Plotkin E.R. and others. Starting regimes of steam turbines of power units. M., Energie, 1980, p. 100-102. 2, USSR author's certificate tf, cl. F 01 N 3/00, 1978. QfO (JJui.i