Power plants – Combustion products used as motive fluid – Combined with regulation of power output feature
Patent
1991-08-08
1993-08-17
Casaregola, Louis J.
Power plants
Combustion products used as motive fluid
Combined with regulation of power output feature
F62C 928
Patent
active
052358062
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a fluid flow system, and, in particular, to a fluid flow system having inbuilt fail-safe fluid controlling means.
In presently known forms of fluid flow systems the control of fluid flow rate to, for example, an aircraft engine, is achieved by means of a fluid flow metering valve having a pressure difference regulator to control the fluid flow rate through the metering valve. In the event of a malfunction or failure of the system, the system itself has no means to regulate fluid flow through the system to counteract the effects, e.g. overspeed or underspeed, to the engine. However independent overspeed governor valves are provided.
DISCLOSURE OF THE INVENTION
The present invention is concerned with providing a fluid flow system having inbuilt fail-safe fluid controlling means, that in the event of a malfunction or failure of the system acts to regulate the system and counteract the effects of malfunction or failure.
In accordance with the present invention, a fluid flow system suitable for controlling the flow of fuel to an engine comprises a fuel metering valve to produce a metered output flow of fuel, and a pressure difference regulator that is responsive to the pressure difference across said fuel metering valve and operates in conjunction therewith to control said output flow of fuel, characterised in that the system includes a system control valve assembly which in the event of a malfunction or failure of the system acts to regulate the output flow of fuel in order to alleviate the effects of the malfunction or failure.
In a preferred embodiment of the present invention, the fluid flow system further comprises an augmenting valve assembly. The augmenting valve assembly is supplied so that in the event of the fluid flow across the system being too low and the pressure difference across the system rising above that encountered under normal operating conditions, the augmenting valve assembly is caused to crack open and allow fluid to flow therethrough. Hence the fluid flow across the system can be restored to the desired level. This increase in pressure in the system may also result in the fluid flow through the fuel metering valve increasing.
In order to enhance the operation of the system, it is desirable that under normal operating conditions the augmenting valve assembly remains closed preventing flow therethrough. In order to achieve this, the augmenting valve assembly may be designed so that it cracks open at a higher pressure differential across the system than would normally be encountered, typically in excess of 10-20% greater than the normal pressure difference.
Preferably, the system further comprises a minimum pressure valve in the line supplying fuel to the engine so that there is a minimum pressure within the system in order to maintain the ability of the system to position valves and bypass excess pump flow relative to engine demand back to reservoir.
The pressure difference regulator, fuel metering valve and minimum pressure valve assembly can be any of the known and available devices designed for the specific service they perform. The particular design of the components is not critical to the operation of the present invention however the function which they perform is important.
The system control valve assembly, preferably, comprises a valve which includes an electromechanical interface. The advantage of utilising a valve which includes an electromechanical interface is that a microprocessor can be used to electronically control the operation of the system in response to signal from the engine, in addition to the system being responsive to partly mechanically derived signals.
In a preferred embodiment of the present invention, the operation of the system is controlled by a microprocessor in response to engine condition signals.
In one embodiment of the present invention, the system control valve assembly comprises an electrohydraulic servo valve. The servo valve may comprise a solenoid operated torque motor which moves and operates a flappe
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patent: 2909896 (1959-10-01), Porter
patent: 4578945 (1986-04-01), Peck et al.
patent: 4760662 (1988-08-01), Dyer et al.
patent: 4817376 (1989-04-01), Brocard et al.
patent: 5088278 (1992-02-01), Smith et al.
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