Solid State Fuel Consumed & Flow Rate Indicator

Technical Information

Catalogue No: C1066
Category: Fuel Systems
Object Type: Indicator/Instrument
Object Name: Solid State Fuel Consumed & Flow Rate Indicator
Part No: 8701-00122
Serial No: 7002-02
Manufacturer: GEC Avionics
Division: Unknown
Platform(s):
Year of Manufacture: circa 2002
Dimensions:
Width (mm):
95 
Height (mm):
25 
Depth (mm):
62 
Weight (g):
175 
Location: Archive Object Store
Inscription(s):

GEC Avionics
8701-00121
-----------------------
GEC Avionics
8701-00122
Ser No 7002-02
-----------------------
µem
111.20140
8701-00126
S/N: 97454/16

Notes:

This was probably made in the Powerplant Systems Division in about 2002. This Division was making replacements for the electro-mechanical instruments using LCD technology for the display.

The "µem" (EM Microelectronics) label is for the LCD part of this folded, flexi-rigid assembly.

Instruments for the measurement of fuel tank capacity and flow seem to have been made by a number of companies such as Simmonds Aerocessories of London who advertised the product in 1952 and in that year, they acquired Firth Cleveland Instruments and as that became the overall company name from 1953 onwards they are found under the  Firth Cleveland Instruments name. Elliott Bros purchased Firth Cleveland Instruments in 1961 and the Aircraft Engine Instruments Division of Elliotts continued the brand from the Treforest works. This site produced fuel flow equipment such as the ‘Pacitor’ system of Fuel Tank Gauges and Fuel Flow Transmitters.

The business later transferred to Rochester where new types of fuel measurement and indication equipment was made.

The Transmitter is a transducer that measures the rate of fuel flowing through it and converts this to an electrical signal to drive a remote meter.There are a number of different measuring techniques:

Differential Pressure Flow meters
The Company made a range of Differential Pressure Flow meters for civil and military aircraft based on the principle of an orifice plate. The fluid flow is measured through the difference in pressure from the upstream side to the downstream side of a partially obstructed pipe. The plate obstructing the flow offers a precisely measured obstruction that narrows the pipe and forces the flowing fluid to constrict.  The accuracy however is poor at low flow rates.  A unit, Type 7801-11000, was designed for direct engine mounting to the Rolls-Royce Spey on the Trident. It had an accuracy of ±1.0% of actual flow rate over the cruise band. Variants of this type use Venturi tubes or flow nozzles but the principle is similar.

Velocity Flow meters
In a velocity flowmeter the flow is calculated by measuring the speed in one or more points in the flow, and integrating the flow speed over the flow area. The Company has produced Turbine Flowmeter which in general operate on the simple principle that if a fluid moves through a pipe and acts on the vanes of a turbine, the turbine will start to spin and rotate. The rate of spin is measured to calculate the flow.

Positive Displacement Flow meters
The positive displacement flow meter measures process fluid flow by precision-fitted rotors as flow measuring elements. Known and fixed volumes are displaced between the rotors. The rotation of the rotors are proportional to the volume of the fluid being displaced. The number of rotations of the rotor is counted by an integral electronic pulse transmitter and converted to volume and flow rate.

The earliest versions of this type have a 'paddlewheel rather than an in-line rotor but only seem to have been experimental.

The Company made gear meters having rotating gears with synchronized, close fitting teeth. A fixed quantity of liquid passes through the meter for each revolution. Shaft rotation can be monitored to obtain specific flow rates.

Another type in our Collection are rotary vane meters consists of equally divided, rotating impellers, two or more compartments, inside the meter's housings. The impellers are in continuous contact with the casing. A fixed volume of liquid is swept to the meter's outlet from each compartment as the impeller rotates. The revolutions of the impeller are counted and registered in volumetric units. Under high pressure a spring loaded disc is pushed open to allow a direct flow through.

Mass Flow meters
Mass meters measure the mass flow rate directly and have two main technologies; the Thermal Flowmeter and the Coriolis Mass Flowmeter

The thermal mass flowmeter operates independent of density, pressure, and viscosity. Thermal meters use a heated sensing element isolated from the fluid flow path where the flow stream conducts heat from the sensing element. The conducted heat is directly proportional to the mass flow rate and the temperature difference is calculated to mass flow.

Coriolis Mass Flowmeter uses the Coriolis effect to measure the amount of mass moving through the element. The fluid to be measured runs through a U-shaped tube that is caused to vibrate in an angular harmonic oscillation. Due to the Coriolis forces, the tubes will deform and an additional vibration component will be added to the oscillation. This additional component causes a phase shift on some places of the tubes which can be measured with sensors. The Coriolis flow meters are in general very accurate, better than +/-0,1% .

Vibrating Vane
The Company Research Lab FARL developed a novel Fuel Flow Transmitter  that used a vibrating metal vane rather than a rotor to measure the rate of fuel flow. The rate of vibration would be modified by the fuel flowing across it in a ratio proportional to the flow of fuel, and the varying vibration frequency was sensed and converted to a signal that could be used in further real time calculations and indications. The item proved to be either unsuitable, unreliable or not viable for full scale production.

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