| CPC F02C 7/047 (2013.01) [B64D 2033/0233 (2013.01)] | 11 Claims |
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1. An aerodynamic engine cowling for a turboprop engine for powering an aircraft comprising:
a plurality of cowl openings through the aerodynamic engine cowling;
the turboprop engine having a drive shaft powered by the turboprop engine and having an axis of rotation, the drive shaft extending outwardly beyond the aerodynamic engine cowling through a first cowl opening; and
a plurality of propeller blades extending from a spinner, the spinner connected to a portion of the drive shaft extending outwardly beyond the aerodynamic engine cowling, so as to spin when the drive shaft rotates around their common axis of rotation;
the aerodynamic engine cowling further comprising:
an engine ram-air intake duct supported within the aerodynamic engine cowling, the engine ram-air intake duct extending between a first open end and a second open end, the first open end being connected to the turboprop engine to feed ram-air thereto and the second open end being in line with, and extending to, the aerodynamic engine cowling at a second cowl opening, the second cowl opening radially offset from the first cowl opening, and the second cowl opening and the second open end being generally oval in shape, a major axis of the second cowl opening and of the second open end extending perpendicular to the axis of rotation of the drive shaft;
a ram-air intake duct inlet lip surrounding and extending forward from the second cowl opening, the ram-air intake duct inlet lip also connected to and in fluid flow connection with the second open end of the engine ram-air intake duct at the second cowl opening so as to be capable of directing a ram-air flow into the engine ram-air intake duct within the aerodynamic engine cowling;
a required deicing ability being provided by connecting a back of the ram-air intake duct inlet lip to an exhaust of the turboprop engine via a pair of circular cross-section tubes to carry hot exhaust gases to and into, and out from, the ram-air intake duct inlet lip to prevent or eliminate icing;
a further improvement to the aerodynamic engine cowling resulting in improving the power output of the turboprop engine without loss of deicing ability comprising:
reducing a total radial height (C) and modifying the shape of a portion of the ram-air intake duct inlet lip closest to the spinner, and increasing a distance of that lip between the portion and the axis of rotation of the spinner by modifying the shape of the portion closest to the spinner such that the total radial height of the modified portion closest to the spinner is reduced to between 55% to 75% of a horizontal distance (B) parallel to the axis of rotation, the horizontal distance measured between an inlet face plane of the ram-air intake duct inlet lip to an inlet duct throat of the ram-air intake duct inlet lip; and
a reference line passing through a leading edge point of the modified portion closest to the spinner, the reference line extending forwardly and rearwardly from the leading edge point of the modified portion closest to the spinner in a direction parallel to the axis of rotation of the spinner and drive shaft, the reference line forming a horizontal plane offset from and parallel to the axis of rotation of the spinner, the horizontal plane divides the total radial height (C) of the modified portion closest to the spinner into an upper portion height (C2) and a lower portion height (C1), the upper portion height (C2) defined between the horizontal plane and an exterior surface facing toward the spinner, the lower portion height (C1) defined between the horizontal plane and an exterior surface facing away from the spinner, the upper portion height (C2) is less than the lower portion height (C1); and
a radial distance (S) between the axis of rotation of the spinner to the reference line is increased to a distance of between 1.2 to 1.5 times a maximum radius (R) of the spinner to increase an air gap region defined between the maximum radius (R) of the spinner and the exterior surface facing toward the spinner of the modified portion of the ram-air intake duct inlet lip to avoid the adverse effects of slow and turbulent airflow generated by the rotating spinner surface;
the improvement further comprises:
maintaining the required deicing ability sufficient to maintain the ram-air intake duct inlet lip free of ice, by providing a transition section between the circular cross-section tube from the exhaust of the turboprop engine to an interior of the ram-air intake duct inlet lip through a rear of the modified portion of the ram-air intake duct inlet lip, the transition section having the form of a circular to ovoidal transition connection between the interior of the modified portion of the ram-air intake duct lip and the circular cross-section tube from the exhaust of the turboprop engine, an ovoidal end of the circular to ovoidal transition connection having a height dimension (F) less than the total radial height (C) of the modified portion closest to the spinner, the height dimension (F) being between about 40% to about 50% of a diameter (E) of the circular cross-section tube, the ovoidal end of the circular to ovoidal transition connection having a width dimension (G) along a lateral length of the ram-air intake duct inlet lip, the width dimension (G) greater than the height dimension (F) such that a cross-sectional flow area of the ovoidal end is between 80% to 100% of the cross-sectional flow area of the circular cross-section tube; and
whereby overheating of an interior of the aerodynamic engine cowling and the exterior of the pair of circular cross-section tubes by the exhaust gas is prevented by a plurality of cooling air openings through the aerodynamic engine cowling to provide cold outside air to the interior of the aerodynamic engine cowling and the exterior of the ram-air intake duct, thereby maintaining the deicing capacity of the system, while also preventing overheating of the interior of the aerodynamic engine cowling and the exterior of the ram-air intake duct by the exhaust gas.
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