Exhaust system for rear drive engine

Claim 2

A high efficiency exhaust system for a turboshaft engine having an annular discharge and a rear drive output shaft, said exhaust system comprising: an annular relatively short diffuser having a substantial area increase ratio fOr recovering, as static pressure, a substantial portion of the velocity head in the gas stream discharged from said engine; an elbow duct receiving the flow from said diffuser and turning it to a discharge in which the flow therefrom is angled with respect to the flow passing from said turbine, said elbow duct having an intermediate portion permitting said output shaft to extend rearward outside of the hot gas flow path through said elbow duct, said elbow duct having an elliptically shaped outlet with the major axis of the ellipse positioned generally at right angles to a plane formed by the longitudinal axis of said output shaft and the center of the ellipse forming said outlet thereby permitting a more gradual curvature to said elbow.

Claim 3

An exhaust system as in claim 1 wherein said diffuser comprises inner and outer generally conical walls having substantial divergence angles and an intermediate generally conical splitter dividing the flow into inner and outer coaxial annular diffusers, thereby minimizing separation of flow from the diffuser walls.

Claim 4

An exhaust system as in claim 1 wherein said elbow duct is contoured to produce a generally constant cross-sectional flow area comprising an annular inlet section, an arcuate intermediate section and a curvilinear outlet section.

Claim 5

A gas turbine engine comprising: a gas generator for generating a hot gas high velocity stream; an axial flow power turbine positioned aft of said gas generator so that the hot gas stream passes across said power turbine; a power turbine shaft extending aft from said axial flow power turbine; an annular relatively short diffuser positioned aft of said power turbine and surrounding said power turbine shaft, said diffuser having a substantial area increase ratio for recovering, as static pressure, a substantial portion of the velocity head in the gas stream discharged from said power turbine; and an elbow duct having an annular inlet receiving flow from said diffuser and an intermediate portion permitting said output draft to extend rearward outside of the hot gas flow path through said elbow duct and an outlet portion discharging said gas stream to atmosphere in a direction angled with respect to the flow from said power turbine, the outlet of said elbow duct having an elliptical shape with the major axis of the ellipse positioned at a right angle to a plane formed by the longitudinal axis of said output shaft and the center of the ellipse forming said outlet thereby permitting a more gradual curvature to said elbow duct.

Claim 6

A gas turbine engine comprising: a gas generator for generating a hot gas high velocity stream; an axial flow power turbine positioned aft of said gas generator so that the hot gas stream passes across said power turbine; a power turbine shaft extending aft from said axial flow power turbine; an annular relatively short diffuser positioned aft of said power turbine and surrounding said power turbine shaft, said diffuser having a substantial area increase ratio for recovering, as static pressure, a substantial portion of the velocity head in the gas stream discharged from said power turbine; and an elbow duct having an annular inlet receiving flow from said diffuser and an intermediate portion permitting said output draft to extend rearward outside of the hot gas flow path through said elbow duct and an outlet portion discharging said gas stream to atmosphere in a direction angled with respect to the flow from said power turbine, the outlet of said elbow duct having an elliptical shape with the major axis of the ellipse positioned at a right angle to a plane formed by the longitudinal axis of said output shaft and the center of the ellipse forming said outlet thereby permitting a more gradual curvature to said elbow duct.

Claim 7

A gas turbine engine as in claim 4 wherein said diffuser recovers approximately 75 percent of the static pressure of the gas stream discharged from said power turbine.

Claim 8

A gas turbine engine as in claim 4 wherein said diffuser comprises inner and outer generally conical walls having substantial divergence angles and an intermediate generally conical splitter dividing the flow into inner and outer coaxial annular diffusers thereby minimizing separation of flow from the diffuser walls.

Claim 9

A gas turbine engine as in claim 4 wherein said elbow duct is contoured to produce a generally constant cross-sectional flow area comprising an annular inlet section, an arcuate intermediate section and said elliptical outlet section.