Heat exchange arrangement in a gas turbine engine fan duct for cooling hot bleed air

In a gas turbine engine including a core engine providing a source of high pressure hot air, an annular nacelle, and at least one support member extending radially between said connecting with said nacelle and core engine and spacing said nacelle about and outwardly from said core engine so as to define an annular fan duct therebetween providing a path of cool main air flow for producing thrust, said support member extending across said cool air flow path, a heat exchange arrangement comprising:

• (a) means for routing a source of high pressure hot bleed air to and from said fan duct;
• (b) a heat exchanger disposed within said fan duct and extending radially between said nacelle and casing, said heat exchanger being connected in flow communication with said routing means such that the high pressure hot bleed air passes through the interior of said heat exchanger;
• and
• (c) at least one elongated partition member disposed within said fan duct for separating said heat exchanger from the main air flow through said fan duct and for temporarily diverting a small fractional portion of the fan duct main air flow from said main air flow to pass said fractional air flow portion over the exterior of said heat exchanger in heat transfer relationship with the high pressure hot air passing through the interior of said heat exchanger and thereafter to return said fractional air flow portion to the main air flow through said fan duct where it is used to generate engine thrust after cooling the high pressure hot air carried by said routing means;
• (d) said partition member extending radially between said nacelle and casing, said partition member being oriented transversely to said heat exchanger and disposed adjacent to said heat exchanger and said support member so as to define therewith a radially and axially extending air diffusion passage through which said fractional air flow portion is diverted to pass over the exterior of said heat exchanger, said passage having an inlet and an outlet communicating with said main air flow, said diffusion passage being larger in cross-sectional size at the location of said heat exchanger than at said inlet and outlet of said passage and being provided with reversely tapering longitudinal configurations at said inlet and outlet of said passage such that said fractional air flow portion decreases in velocity after entering said passage through said inlet and before reaching said heat exchanger and then increases in velocity after leaving said heat exchanger and approaching said outlet.