FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1946
1946 - 0067.PDF
JANUARY IOTH, 1946 FLIGHT THE JET-ENGINE FUEL SYSTEM Supply, Atomising and Control Equipment Developed by Joseph Lucas BAROMETIC PRESSURE- CONTROL UNIT THROTTLE VALVE WHILST the work of evolving the jet-engine com-bustion system and equipment was proceeding,* aparallel activity of Joseph Lucas, Ltd., was the development of fuel pumps, burners and regulating com- ponents for the control of the engine. Initiated in Bir- mingham, this work was for a short time transferred to Acton, but subsequently returned to a specially equipped factory at Birmingham. Early Whittle engines employed a constant-displacement pump and a barometrically-controlled variable by-pass, but it was decided at the outset that such a system suffered from certain limitations and did not offer adequate scope for future development. To meet the wide ranges of fuel flow required by the gas turbine at vary- ing air speeds and alti- tudes a pump having a variable stroke, regu- lated by a servo system under barometric con- trol, was deemedwa more desirable. As no pumpof light weight and occu- pying small space wasavailable to meet these requirements, the de-velopment of a special pump was undertaken.After surmounting early difficulties of considerablemagnitude, a successful design was evolved forthe pump which has been employed on allRolls-Royce jet engines. Clean fuel is essentialfor satisfactory operation owing to the fine work-ing clearances of the components and the re-latively restricted pas- sages in the burners.Accordingly, all Bowser tankers employed for re-fuelling jet aircraft are equipped with Stream-line filters to prevent the transfer of foreign matter to the I aircraft tank. Fuel is drawn from the tank by a sub-^nerged electrically-driven, centrifugal-type Pulsometer pump and is passed through a Tecalemit fabric-type filterbefore reaching the pressure pump. On the power unit the fuel system includes the followingcomponents—variable-stroke pump with a built-in maxi- mum speed governor and an automatic pressure-reliefmechanism, barometric control unit, throttle valve, a unit, embodying accumulator, trip valve and high-pressure cock,fuel manifold and burners. Disposition of this equipment on the wheel case at the forward end of the Rolls-RoyceDerwent engine is shown in an illustration, and connections can be readily followed in the diagrammatic layout. Fuel is fed to the engine-driven pump, which operates • Described in Plight, 3rd January, 1946. IT would not be inapt to describe the fuel and combustion systems as the " heart and soul " of the aircraft turbine power unit, whether for jet or airscrew propulsion. This article on the fuel system, in conjunction with the one on combustion research in the previous issue, gives the first full account of the development and functioning of these vital components. It is a record of per- sistent, painstaking effort by Joseph Lucas, Ltd., undertaken in collaboration with Rolls-Royce, Ltd..which in its success- ful achievement has made a substantial and noteworthy contribution to British prestige in the air. BURNER FUEL FUEL PUMP £MAX SPEED COVERNOR LOW PRESSUREFILTER ACCUMULATOR TRIP VALVE& SHUT OFF COCK Installation of fuel equipment on Rolls-Royce Derwent jet engine. in conjunctionwith the altitude- conscious baro-metric control unit and is subject to the over-riding control of the hydraulic-type governor, which prevents theengine speed exceeding a predetermined maximum. From the pump the fuel is delivered to the throttle valve, whichis regulated by the pilot from the cockpit, and thence to the accumulator unit, the ring manifold and, by individualflexible pipes, to the burners in the combustion chambers. The accumulator is required to build up a volume of fuelunder adequate pressure for starting purposes. When shutting down theengine the high-pressure cock shuts off the flowof fuel to the burners. Drain connections frompump, throttle and accu- mulator unit discharge MANIFOLD to atmosphere. Gaugesare provided to indicate pressure at the pumpdelivery and in the manifold and depressionat the pump intake. In conjunction with thelast, a pressure-sensitive switch operates a warn-ing light in the event of the fuel supply beinginterrupted by a clogged low-pressure filter. The seven plungers ofthis positive - displace- ment pump reciprocatein a rotor running in a carbon bush and a rollerrace and driven from the engine by a splined quillshaft. The bores for the plungers are spacedevenly around a pitch cone concentric with therotor axis and converge towards the inner orpumping end. Recipro- SPILL TO ATMOSPHERE cation of the plungers iseffected by means of a cam plate engaging the outer ends of the plungers. The cam plate is carried on a large-diameter ball bearing mounted in a control ring swivelling on a pair of trunnion pins set at right angles to the rotoraxis. By varying the angle of the plane of the cam plate relative to the rotor axis from 90 deg. to 81 deg. the strokeof the plungers is varied from zero to approximately 10.5 mm. Retraction of the plungers on the inlet strokeis ensured by helical springs located against the reduced inner ends of the bores. At its inner end the face of the rotor is ground flat andsmooth to make a pressure-tight seal with a valve insert furnished with two kidney-shaped ports communicatingrespectively with the pump inlet and the pump delivery. Thus each plunger bore is in communication with thesuction and delivery passages of the pump once in each
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
