Westinghouse Electric Corporation

George J Silvestri, Jr

Homer G Hargrove

Paul W Viscovich

Joseph Davids

Michael Twerdochlib

Alvin L Stock

Scott W Kendall

Robert Draper

David H Evans

Shun Chen

Ashok T Patel

Daniel E Fridsma

James A Martin

Douglas R Ulrich

Richard M Stephani

Vincent P Buscemi

Michael S Nusbaum

Joseph T Turner

Krishnamurthy Kesavan

Vernon J Musko

Anthony F Ganci

Manuel I Llaneras

A method of reducing turbine inlet temperature excursions during sudden load demand reductions on a steam turbine, the turbine being coupled to a controllable source of high pressure, high temperature steam, incorporates throttling of steam within the steam source in conjunction with steam throttling at the turbine so as to apportion temperature drops between the source and turbine. In one form, the method includes the steps of sensing a sudden drop in load demand on the steam turbine, operating the steam source to reduce exit pressure of the steam at the steam source and bypassing sufficient steam around the steam turbine to reduce steam flow through the turbine by an amount commensurate with the drop in load demand. The steam source may be controlled by adjusting division valves between primary and secondary superheaters in the steam source to throttle steam pressure at the secondary superheater and then heating the steam in the secondary superheater to a temperature which compensates for the temperature drop across the division valves caused by throttling.

Reduction in turbine/boiler thermal stress during bypass operation

An improved cycle arrangement for a steam turbine system in which an auxiliary turbine drives a boiler feedwater pump. The turbine system includes a primary turbine driving an electric power generator. The primary turbine includes a high pressure section and a low pressure section. A boiler supplies steam to drive the primary and auxiliary turbines. A condenser recovers exhaust steam from the LP section and a plurality of feedwater heaters preheats condensate collected at the condenser and pumped back to the boiler. The system extracts steam from the HP turbine section for operating the auxiliary turbine. Extracted steam from the auxiliary turbine is isolated from the primary turbine by coupling the steam to a feedwater heater supplied solely from a corresponding extraction point of the auxiliary turbine. The exhaust steam from the auxiliary turbine is coupled directly to the condenser.

Boiler feedpump turbine drive/feedwater train arrangement

A steam turbine system including a low pressure (LP) turbine has a plurality of moisture extraction points at which a steam-water mixture is extracted and passed through a respective one of a corresponding plurality of heat exchangers. Each exchanger passes the steam-water mixture in heat exchange relationship with feedwater in a feedwater conduit. A low pressure and low temperature final stage extraction point on the steam turbine is coupled to a condenser, and water collected at the condenser is directed into the feedwater conduit. The system separates at least some of the steam in the steam-water mixture from the final stage extraction point and passes this steam in heat exchange relationship with water in the feedwater conduit.

Internal moisture separation cycle for a low pressure turbine

A method for improving operational efficiency of a partial-arc steam turbine power plant during power output variations by dynamically adjusting valve point values during turbine operation. Impulse chamber pressure at each of a plurality of valve points is first determined during operation of the steam turbine at constant pressure. For each adjacent pair of valve points, an optimum constant pressure transition point pressure for transitioning from one to the other of the sliding pressure mode and constant pressure mode is then computed. The optimum constant pressure transition point pressure for each pair of valve points is converted to a corresponding percentage of the pressure difference between the adjacent pairs of valve points. The impulse chamber pressure at each valve point is then used to calculate a corresponding impulse chamber pressure for transitioning from the one mode to the other mode based upon the percentage pressure difference. During the transition, the control valve associated with the transition point and valve point is gradually closed.

Operation between valve points of a partial-arc admission turbine

Method for improving the heat rate of a steam turbine operated in a partial-arc mode includes sequential closing of control valves to establish a first arc of admission at which pressure drop on a first control stage reaches a predetermined level. Steam pressure to the turbine may then be reduced in combination with valve closing to maintain first stage pressure at or below the predetermined level. In a further method, low power operation is achieved by maintaining a constant arc of admission while simultaneously moving all open valves toward a closed position.

Governor valve positioning to overcome partial-arc admission limits

Steam exhaust outlets of a low pressure steam turbine are fitted with a divider plate to separate exhaust steam into isolated flow paths in fluid communication with a condenser. Separation of the flow paths is maintained through the condenser so that heat rate is improved by lower average back pressure and higher temperature condensate exiting the condenser. In a double flow turbine, a further divider plate separates steam from one exhaust outlet from that of the other exhaust outlet thereby creating four steam flow paths to the condenser.

Turbine exhaust arrangement for improved efficiency

A honeycomb seal cooperatively associated with a rotatable blade of a steam turbine having a cylinder, seal include a backing plate fixedly connected to a mounting portion of the cylinder, the mounting portion having an associated moisture removal channel. A plurality of rows of honeycomb cells extend radially inwardly from the backing plate so that each cell is open adjacent said blades. The said backing plate is perforated with at least one perforation for each honeycomb cell for communicating moisture collected in the honeycomb cells to the moisture removal channel of the mounting portion of the cylinder.

Moisture drainage of honeycomb seals

Internal moisture separation cycle

A method for improving operational efficiency of a partial-arc steam turbine power plant during power output variations by dynamically adjusting valve point values during turbine operation. Impulse chamber pressure at each of a plurality of valve points is first determined during operation of the steam turbine at constant pressure. For each adjacent pair of valve points, an optimum constant pressure transition point pressure for transitioning from one to the other of the sliding pressure mode and constant pressure mode is then computed. The optimum constant pressure transition point pressure for each pair of valve points is converted to a corresponding percentage of the pressure difference between the adjacent pairs of valve points. The impulse chamber pressure at each valve point is then used to calculate a corresponding impulse chamber pressure for transitioning from the one mode to the other mode based upon the percentage pressure difference. The calculated impulse chamber pressures for transitioning are compared to measured values of impulse chamber pressure and the system force transition from one of the modes to the other mode when the measured value is substantially equal to the calculated transition pressure.

Method for predicting the optimum transition between constant and

An ultrasonic cleaning apparatus and method is provided for a venturi flow nozzle which is mounted in a pipe having fluid flowing therethrough. The apparatus includes a plurality of ultrasonic transducers mounted in openings provided upstream of the venturi flow nozzle inlet. The transducers transmit ultrasonic waves directly into and thereby excite the fluid flowing through the venturi flow nozzle and create cavitation which cleans the nozzle. Additional transducers are preferably provided in the throat area of the venturi flow nozzle. In alternative embodiments, the transducers are mounted in high and low pressure taps associated with the venturi flow nozzle such that the transducers directly transmit ultrasonic waves into fluid flowing into the high and low pressure taps. The transducers may be mounted flush with the interior of the pipe or venturi flow nozzle, or the transducers may be mounted at a position spaced therefrom in the high and low pressure tap piping.

Ultrasonic flow nozzle cleaning apparatus

A steam turbine including a plurality of rows of rotating blades interspersed with a plurality of rows of stationary blades incorporates a water barrier extending substantially across a suction side of each blade of at least one of the rows of stationary blades. Each of the water barriers is positioned relatively near a radially outer end of a respective blade and approximately parallel to an end wall of the steam turbine. Moisture which accumulates on the radially outer end of the stationary blades is trapped between the end of the blade and the water barrier. Any water which attempts to flow over the top of the barrier is picked up by the steam flow and broken into small droplets while being rapidly accelerated. Water held behind the barrier and which flows off the trailing edge of the stationary blade only impacts a limited extent of the following rotating blade row. Water collection schemes may be utilized to collect the moisture trapped above the barrier and transfer the moisture through the turbine end wall to appropriate feedwater reheaters.

Erosion control through reduction of moisture transport by secondary flow

A steam turbine system has a plurality of moisture-separator-reheaters (MSR) each connected via a respective drain line to a corresponding drain receiver. Each drain receiver includes a further drain line coupled through a flow control valve to a common line. The common line empties into a drain cooler connected at the highest pressure end of a series of feedwater reheaters. The drain cooler dumps through another flow control valve to one of the feedwater heaters. Each of the drain receivers includes a pressure sensor and liquid level sensor. A control processor monitors the pressure sensors and selects the drain receiver subjected to the lowest pressure. The processor then fully opens the valve associated with the selected drain receiver and thereafter regulates the liquid level in the others of the drain receivers by adjustment of their respective flow control valves in response to their respective level sensors. The liquid level in the selected drain receiver is adjusted to its preselected level by control of the flow control valve connected to the drain cooler. The pressure in the common drain line is regulated to the pressure at the lowest pressure drain receiver by adjustment of the control valves associated with the other drain receivers.

Moisture-separator-reheater drain cooler system

A simple and accurate method for determining the enthalpy of wet steam using pressure and moisture content values. Moisture content is determined by measuring sonic velocity of the steam, which is dependent upon enthalpy. A small sample of the wet steam is superheated by pressure reduction to a single-phase state prior to measuring its sonic velocity in order to achieve greater accuracy of this measurement. From its sonic velocity, enthalpy of the sample is calculated. Since the process takes place at constant enthalpy, the enthalpy value of the sample is the same as that of the fluid from which it was drawn.

Method of determining the enthalpy and moisture content of wet steam

A positioning system for a steam turbine element includes a plurality of flex plates which support an inner cylinder of a steam turbine element with the rotating blades of a rotor and the stationary blades of the inner cylinder at a predetermined position. Sensors detect shifting of the rotor within the inner cylinder and provide control signals to a motor which drives the inner cylinder in an axial direction to account for shifting of the rotor.

Inner cylinder axial positioning system

Power output of a steam turbine is increased by removal of at least one stage of blading in order to increase mass flow through the turbine. A flow guide or annular ring is installed in the space in the inner cylinder or blade ring surrounding the area from which the blading stage has been removed. The flow guide has a radially inner surface conforming generally to the surface configuration of the inner cylinder surrounding the turbine blades. The flow guide presents a relatively smooth, continuous surface to inlet steam flow so that flow separation and turbulence are reduced with a corresponding increase in efficiency.

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Winter Park, FL, United States of America

George J Silvestri, Jr