Fluid flow valve and fluid flow system

Details Fluid flow valve and fluid flow system Fluid flow valve and fluid flow system

1998-11-02

2001-03-27

Thorpe, Timothy S. (Department: 3746)

Power plants

Combustion products used as motive fluid

With safety device

C060S039281

Reexamination Certificate

active

06205766

ABSTRACT:

This invention relates to a fluid flow valve having a plurality of operative states corresponding to respective operative conditions in a fluid flow system to which it is adapted for connection in use, the valve being switchable between its operable states to modify the condition of the system correspondingly.
The invention is particularly, but not exclusively, applicable to a fuel supply system for an aircraft gas turbine engine, in which three operative conditions may provide, for example, a normal fuel flow from a metering valve to the engine, a normal shut-down condition in which fuel flow is progressively reduced, and a rapid shut-down or emergency condition in which the fuel supply is interrupted very rapidly to prevent damage to the engine and/or associated components.
According to a first aspect of the invention, a fluid flow system for supplying fuel to an engine includes a fluid flow valve comprising a valve element movable alternatively to a first operative position in which a relatively low fluid flow rate is permitted through the valve, for achieving a normal gradual shut-off of fuel supply, and a second operative position in which a relatively high fluid flow rate is permitted through the valve, for achieving a rapid emergency shut-off of fuel supply.
Preferably, the relatively low flow rate is obtained by way of a restricted flow path through which the fluid is directed in said first operative position of the valve element, the fluid being directed through a less restricted flow path when the valve element is in the second said operative position.
In one convenient arrangement, the valve is of the centre-stable type, being preferably a spool valve, the valve element being movable from a central position to either of said two operative positions, as required.
The valve may comprise a port incorporating flow restriction means serving to restrict flow along said restricted flow path.
Typically, movement of the valve element is controlled by a torque motor, preferably of the multi-coil type.
Fluid flow may selectively be permitted through the valve body along first respective alternative restricted and less restricted flow paths connecting a high pressure fluid source to a servo chamber of a shut-off valve and second respective alternative restricted and less restricted flow paths connecting a servo chamber of a spill valve to a low pressure region.
In a typical practical arrangement, the fluid flow system includes a metering valve operable to provide, from a high pressure input flow, a metered fuel supply to a gas turbine engine via the normally open shut-off valve, the pressure drop across the metering valve being maintained substantially constant by the spill valve, the fluid flow valve having two pairs of valve ports arranged so that, in one of its said operative positions, the valve permits flow through one port from each pair such as to provide a relatively low flow rate respectively along the first restricted flow path to the shut-off valve servo chamber and along the second restricted flow path from the spill valve servo chamber, whereby a normal gradual shut-off of the fuel supply is achieved, and in the other of said operative positions, permits flow through the other port from each pair to provide a relatively high flow rate respectively along the first less restricted flow path to the shut-off valve servo chamber and along the second less restricted flow path from the spill valve servo chamber whereby a rapid emergency shut-off of the fuel supply is achieved.
According to another aspect of the invention, a fluid flow valve comprises a valve body incorporating a valve element movable alternatively to two operative positions in which respectively relatively low and relatively high fluid flow rates are permitted through the valve body, flow restriction means being provided in the valve body for causing said relatively low fluid flow rate.


REFERENCES:
patent: 4546786 (1985-10-01), Koike
patent: 5235806 (1993-08-01), Pickard
patent: 5315818 (1994-05-01), Smith
patent: 5555720 (1996-09-01), Wernberg et al.
patent: 5709079 (1998-01-01), Smith

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