Abstract: A floating piston (54) has a valved (86) vent opening (88), with the vent opening closing (92) on movement of the piston. The piston is spring loaded (56, 58) to vent air, but seal fuel. Modulation of pressure in pressure resisting chamber (48) between pump discharge and lower pressures, provides control of the valve. Pressure difference (96, 62) and valve position (36) measurements provide flow measurement data.

Abstract: A vapor core centrifugal fuel pumping system (10') has a main flow impeller (72) and a low flow impeller (81) mounted upon the front plate (74) of the main flow impeller. Both of the impellers receive flow from an inlet passage (26') which proceeds past an inlet throttling valve (114). During pumping operation of the low flow impeller, a surface (122) on the inlet throttling valve forms a labyrinth seal with the radially inner lip (120) of the front plate to reduce inlet fuel flow entering the main impeller. A first check valve (124) and a second check valve (126) respectively prevent flow from the low flow impeller from entering the main flow impeller and flow from the main impeller from entering the low flow impeller. The second check valve is associated with conduits (140, 142) to evaculate liquid adjacent the main impeller during operation of the low flow impeller to reduce windage losses.

Abstract: A centrifugal main fuel pump (10') for a gas turbine engine has a housing (18') in which a centrifugal impeller (12') is mounted for rotation. The impeller discharges flow to a collector (20') and diffuser (22'). A low flow diffuser (26) has its inlet opening positioned closely adjacent the outer periphery of the impeller. Proper design and placement of the low flow diffuser ensures that a high percentage of the fluid energy available in the high velocity flow adjacent the impeller outer periphery is recovered as pressure rise. The low flow diffuser produces adequate fuel flow at the pressure necessary for engine light-off while the first mentioned diffuser recovers a lower pressure rise but is adapted to supply higher engine fuel flow demand in the normal range of operation. A check valve (34) prevents flow from the low flow diffuser from returning to the impeller. The check valve opens to allow the first mentioned diffuser to supply fuel when its discharge pressure exceeds that of the low flow diffuser.

Abstract: A centrifugal main fuel pump (10') for a gas turbine engine has a housing (12') in which a centrifugal impeller (16') is mounted for rotation. The centrifugal impeller includes a disc (24') which carries starting flow impeller elements (34) which are positioned in a radially outer location on the disc and also carries main flow impeller elements (26') positioned in a radially inner location on the disc. The starting flow impeller elements discharge to a starting flow collector (38) and diffuser (44) and the main flow impeller elements discharge to a separate collector (30') and diffuser (32'). The starting flow impeller elements produce adequate fuel flow at the pressure necessary for engine lightoff while the main flow impeller elements are adapted to supply engine fuel flow demand in the normal range of operation. A check valve (46) prevents starting flow from returning to the centrifugal impeller.