Aeronautical generator

Abstract

An unpressurised aeronautical generator ( 2 ), is provided which includes a two stage oil pump ( 6 ) comprising a centrifugal pump ( 8 ) and a gerotor pump ( 26 ). The centrifugal punp draws oil through openings ( 18 ) in a manifold, pressurises it and supplies it to the gerotor pump. The gerotor pump then pumps the pressurised oil throughout the generator. A small gerotor pump is used, which is still sufficient to operate at low pressures and high altitudes.

1 . An unpressurised aeronautical generator comprising a reservoir of oil, a centrifugal pump and a positive displacement pump, wherein the centrifugal pump is in series fluid communication with the positive displacement pump such that in operation, the centrifugal pump pumps oil from the reservoir to an input of the positive displacement pump, and the positive displacement pump delivers the oil for use in the generator.  
   
   
       2 . An unpressurised generator as claimed in  claim 1 , wherein the centrifugal pump is positioned co-axially with the positive displacement pump.  
   
   
       3 . An unpressurised generator as claimed in  claim 1 , wherein the centrifugal pump and the positive displacement pump are driven from a shared shaft.  
   
   
       4 . An unpressurised generator as claimed in  claim 1 , wherein an inlet manifold directs the oil from the reservoir to the centrifugal pump.  
   
   
       5 . An unpressurised generator as claimed in  claim 1 , wherein the centrifugal and positive displacement pumps are positioned within a casing of the generator.  
   
   
       6 . An unpressurised generator as claimed in  claim 1 , wherein at least one of the centrifugal pump and the positive displacement pump is positioned externally to a casing of the generator.  
   
   
       7 . An unpressurised generator as claimed in  claim 1 , wherein the positive displacement pump is one of a gerotor pump and a gear pump.  
   
   
       8 . An unpressurised generator as claimed in  claim 1 , wherein the centrifugal pump and the positive displacement pump are integrated as a single pump.  
   
   
       9 . An unpressurised generator as claimed in  claim 1 , wherein the reservoir is a sump within the generator.  
   
   
       10 . An unpressurised generator as claimed in  claim 1 , wherein the generator has an air inlet valve extending between the interior of the generator and the ambient surroundings and the valve is arranged to admit air into the generator when air pressure within the generator is less than an ambient air pressure.  
   
   
       11 . An oil pump for use within an unpressurised generator for an aircraft, the oil pump comprising an oil inlet, an oil outlet, a regenerative pump and a positive displacement pump, and wherein, in operation, the regenerative pump pumps oil from the oil inlet to an inlet of the positive displacement pump, and the positive displacement pump pumps the oil to the oil outlet, and wherein the positive displacement pump is smaller than it would be if the same pump type alone was used to provide oil flow to the generator.  
   
   
       12 . An oil pump as claimed in  claim 11 , in which the regenerative pump is a centrifugal pump.  
   
   
       13 . An oil pump as claimed in  11 , in which the regenerative pump is positioned co-axially with the positive displacement pump.  
   
   
       14 . An oil pump as claimed in  claim 11 , in which the regenerative pump and the positive displacement pump are driven from a shared shaft.