Fluid handling – Systems – Multi-way valve unit
Patent
1993-03-16
1994-07-19
Nilson, Robert G.
Fluid handling
Systems
Multi-way valve unit
137875, 251120, F16K 1102
Patent
active
053299701
DESCRIPTION:
BRIEF SUMMARY
This invention relates to diverter valves, particularly diverter valves provided at a three-way junction through which passes a gas at a sufficiently high temperature for it to be practical or desirable to extract heat from the gas exhaust. More specifically the invention relates to diverter valves used in exhaust systems of a gas turbine combined cycle generating plant or co-generation plant or other plant where by-pass arrangements exist, to minimize the back pressure loss and hence improve the cycle efficiency.
Gas turbines are frequently used to drive rotating machinery such as compressors, pumps and electric generators. Thermodynamically the gas turbine is a relatively inefficient prime mover, because, although the inlet temperature of the working fluid is high, the reject temperature is also relatively high and much high grade heat is lost. However, it is now common practice to couple a simple cycle gas turbine with a heat recovery steam generator (HRSG) or other heat exchanger to extract more heat from the working fluid to provide superheated steam for a steam turbine in combined cycle plant, or saturated steam for some process, or both, in cogeneration systems.
In the exhaust ducting systems following the gas turbine discharge, gas flow velocities are maintained at relatively high levels to reduce the size of ducting and silencers and to promote high rates of heat transfer in the heat recovery equipment. With these high velocities, pressure drops in the exhaust system can be considerable, and these pressure drops increase the back pressure which reduces the power output of the turbine. This back pressure may have substantial economic implications as an increase in turbine back pressure of 100 mm H.sub.2 O can reduce the power output by 1%.
Diverter valves or isolating dampers are invariably fitted in the exhaust system where heat recovery equipment is installed, to perform the following functions: to enable maintenance to be carried out while the turbine operates on simple cycle, i.e. discharging through the by-pass without any heat recovery from the working fluid; is in operation; operation.
These diverter valves or dampers are often situated at or adjacent to points in the system where T-junctions occur, typically at HRSG inlet and by-pass locations. These T-junctions cause high pressure drops, of the order of 115% of velocity pressure when the flow of gas is directed around a sharp bend. Depending on the plant layout, the flow through the bend may occur either when the plant operates on by-pass or on heat recovery mode.
Turning or deflecting vanes, or splitters, which are frequently fitted to sharp bends in ducting systems to reduce the pressure drop to about 35% of velocity pressure, cannot be fitted in the ducting at a T-junction because they would obstruct the flow when it is directed in the straight through mode.
Although most plants with waste heat recovery systems will be normally expected to operate with the by-pass closed, it can be that a plant may operate for extended periods through the by-pass, perhaps because the plant operates initially on simple cycle while construction of the heat recovery equipment proceeds, or because of reduced load demand or for maintenance of the heat recovery equipment. It is therefore apparent that, even when the bend in the flow direction is to the by-pass, considerable economic savings may be made by providing equipment which causes the inherent pressure loss of the bend to be reduced.
The diverter valves or isolating dampers provided at the various locations were formerly typically of the following types:
______________________________________ (1) HRSG Inlet Guillotine
Louvre
Flap
(2) By-Pass Louvre
Flap
(3) HRSG Outlet (where fitted)
Guillotine
Louvre
Flap
______________________________________
All these types when fitted adjacent to T-junctions do not provide any means of minimizing the pressure drop at the T-junctions.
There is thus a need for a diverter valve which can be fitted at such T-junctions and which has a capability to
REFERENCES:
patent: 3270775 (1966-09-01), Alderson
patent: 4342333 (1982-08-01), Mizuno
patent: 4342528 (1982-10-01), McAndrew
patent: 4351361 (1982-09-01), Worley
patent: 4573551 (1986-03-01), Schwerdtner et al.
patent: 4597415 (1986-07-01), Gieseke
Nilson Robert G.
WES Technology Inc.
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