Aircraft turboprop engine inlet compact profile configuration

Abstract

A turboprop powered aircraft having a cowling or nacelle surrounding the engine, said cowling incorporates an air inlet and internal ducting to the engine wherein the inlet incorporated anti-icing ducts, said inlet shape has a closed oval or other non-circular shape that is not coaxial to the engine propeller drive shaft. Inlet anti-icing heating duct means are provided for channeling a portion of the engine's exhaust to the interior of the inlet rim. A further improvement in inlet efficiency can be achieved by reducing the thickness of the inlet cross-section, but this results in less space available for the hot exhaust connections. To provide for the inlet reduced section thickness, the exhaust flow connections also incorporate reduced thickness sections to facilitate cooling and insulation of the adjacent cowling and inlet duct surfaces from the excessive heat associated with the hot exhaust gas connection. Additional cooling means utilize air flow from openings in the engine cowling that are channeled to cool internal surfaces of the cowling that may be exposed to excessive heat.

The following invention is claimed: 
     
         1 . An engine for a turboprop powered aircraft incorporating an engine ram air intake duct, the ram-air intake duct comprising a ram-air inlet lip defining the opening into the engine ram-air intake duct, the ram-air inlet lip presenting a closed, ovoidal, forward facing shape; a spinner and propeller blades secured to the spinner, the spinner being rotatively connected to the engine cowling forward of the cowling and ram-air inlet lip; wherein the engine ram-air inlet lip extends rearwardly from a position rearward of the boundary of the spinner and cowling; a reference line extending parallel to the centerline of the spinner, rearwardly and forwardly from the forwardmost point of the ram-air inlet lip, extends at a distance below the centerline of the spinner and divides the interior of the ram-air inlet lip such that the portion within the inlet lip above the reference line parallel to the centerline of the spinner is smaller than the portion within the inlet lip below that reference line. 
     
     
         2 . The engine for a turboprop powered aircraft incorporating an engine ram air intake duct of  claim 1 , wherein the maximum thickness or height of the portion above the reference line is less than 40% of the total thickness of the ram-air inlet lip. 
     
     
         3 . The engine for a turboprop powered aircraft incorporating an engine ram air intake duct of  claim 2  wherein the maximum thickness or height of the portion above the reference line at the duct throat, is greater than 25%. 
     
     
         4 . The engine for a turboprop powered aircraft incorporating an engine ram air intake duct of  claim 2  wherein the maximum thickness or height of the portion above the reference line at the duct throat, is between 25% and 35% of the inlet intake air opening height (opening vertical dimension) measured at the location of the inlet duct throat. 
     
     
         5 . The engine for a turboprop powered aircraft incorporating an engine ram air intake duct of  claim 1  wherein the maximum thickness or height of the section measured at the inlet throat is between 60% and 75% of the distance from the inlet lip face to the location of the inlet throat. 
     
     
         6 . An engine cowling for a turboprop aircraft incorporating a ram-air intake duct comprising a ram-air intake duct inlet lip having a closed, approximately oval profile relative to the front view of the engine nacelle, where in the inlet incorporates means to deice the inlet lip by passing a portion of the engine exhaust flow into the interior of the inlet lip and wherein the exhaust flow connections to the interior of the inlet lip flow through a circular to non-circular, or ovoidal, transition connection attached to the inlet lip interior, wherein the vertical thickness of the transition connection is reduced to 50% or less than the diameter of the of the exhaust round tube connection. 
     
     
         7 . The engine cowling for a turboprop aircraft incorporating a ram-air intake duct of  claim 6  wherein the exhaust flow connections to the inlet transition connection are supported by a bracket attached to the outer surface of the engine air intake duct. 
     
     
         8 . The engine cowling for a turboprop aircraft incorporating a ram-air intake duct of  claim 6  wherein the transition connection has a minimal flow area between 80% and 100% of the flow area of the exhaust connection round tube. 
     
     
         9 . An engine cowling for a turboprop aircraft incorporating a ram-air intake duct lip in accordance with  claim 10 , wherein the surfaces of the cowling and intake duct in close proximity to the exhaust flow connections to the inlet lip are cooled by air flow from a plenum chamber within the cowling receiving cooling air from openings in the cowling. 
     
     
         10 . An inlet for the Pilatus PC-12 and 21 models incorporating the design elements specified in  claim 11 . 
     
     
         11 . An inlet for the Pilatus PC-12 and 21 models incorporating the design elements specified in  claim 12 . 
     
     
         12 . The engine cowlings for a multi-engine turboprop aircraft, each engine incorporating a ram-air intake duct of  claim 1 . 
     
     
         13 . The engine cowlings for a multi-engine turboprop aircraft, each engine incorporating a ram-air intake duct comprising a ram-air intake duct inlet lip having a closed, approximately oval profile relative to the front view of the engine nacelle in accordance with  claim 6 .