Fuel pumping system for gas turbines

Claim 1

A FUEL SYSTEM FOR A GAS TURBINE ENGINE COMPRISING, IN COMBINATION, A SOURCE OF FUEL, SAID TURBINE PUMP HAVING A VOLUMETRIC CAPACITY BELOW ENGINE MAXIMUM FUEL REQUIREMENTS AND HAVING A PRESSURE RISE AT LOW ENGINE SPEED SUFFICIENT TO SUPPLY THE ENGINE IN LOW SPEED OPERATION THEREOF, A TURBINE PUMP SUPPLIED THEREFROM, A CENTRIFUGAL PUMP SUPPLIED BY THE TURBINE PUMP, AND FUEL FLOW CONTROLLING MEANS INTERPOSED BETWEEN THE CENTRIFUGAL PUMP AND AN OUTLET TO THE ENGINE, THE SYSTEM INCLUDING MEANS WHEREBY THE PUMPS ARE DRIVEN CONCURRENTLY BY THE ENGINE, THE CENTRIFUGAL PUMP HAVING SUBSTANTIALLY GREATER VOLUMETRIC CAPACITY THAN THE TURBINE PUMP, AND A CONDUIT CONNECTING THE FUEL SOURCE TO THE CENTRIFUGAL PUMP AND BYPASSING THE TURBINE PUMP, THE CONDUIT INCLUDING CHECK VALVE MEANS ALLOWING FLOW ONLY FROM THE SOURCE, SAID CHECK VALVE MEANS OPENING WHEN ENGINE FUEL REQUIREMENTS EXCEED MAXIMUM DISCHARGE PRESSURE OF SAID TURBINE PUMP WHEREBY SAID TURBINE PUMP IS BYPASSED AND RUNS SUBSTANTIALLY IDLE WHILE SAID CENTRIFUGAL PUMP SUPPLIES ALL OF THE FUEL AT HIGHER ENGINE SPEEDS.