Counter-rotatable fan gas turbine engine with axial flow positive displacement worm gas generator

#The present invention relates generally to gas turbine engines with counter-rotatable fans and, more particularly, to such engines having axial flow positive displacement gas generators and worm and screw compressors and turbines.

#Aircraft gas turbine engines generally have in downstream flow relationship fan, compressor, combustion, and turbine sections. The turbine sections generally drive the compressor and fan sections. The combustor section burns fuel in an airflow compressed by the compressor to provide energy to the turbines. Aircraft gas turbine engines may have one, two, three, or more rotors or spools. One or two fans upstream of the compressor are driven by one or two turbines as are the compressors. The fans, compressors, and turbines typically include radially extending blades. Core engines or gas generators of the aircraft gas turbine engine generally include a high pressure compressor, a combustor, and a high pressure turbine to provide high energy fluid to the turbines to provide power for the engine's fan or fans. Continuous axial flow gas turbine engines are utilized in a wide range of applications owing in a great deal to a combination of desirable attributes such as high specific energy exhaust stream (energy per unit mass), high mass flow rate for a given frontal area, continuous near steady fluid flow, and reasonable efficiency over a wide range of operating conditions. It is desirable to have light-weight and highly efficient engines. One type of highly efficient engine includes counter-rotatable fans powered by counter-rotatable low pressure turbines such as those disclosed in U.S. Pat. Nos. 6,763,653, and 6,763,654.

#Axial flow gas generators are particularly useful in many turbomachinery applications. Turbomachinery based gas generators are utilized in a wide range of applications owing in a great deal to a combination of desirable attributes such as high specific energy exhaust stream (energy per unit mass), high mass flow rate for a given frontal area, continuous, near steady fluid flow, reasonable thermal efficiency over a wide range of operating conditions. It is a goal of gas turbine engine manufacturers to have light-weight and highly efficient engines and gas generators. It is another goal to have as few parts as possible in the gas generator to reduce the costs of manufacturing, installing, refurbishing, overhauling, and replacing the gas generator. Therefore, it is desirable to have an aircraft gas turbine engine with a gas generator that improves all of these characteristics of gas turbine engines and their gas generators.

#FIG. 1 is a cross-sectional view illustration of an exemplary aircraft gas turbine engine with a counter-rotatable fan section and a positive displacement axial flow or worm gas generator.

#FIG. 2 is a diagrammatic cross-sectional view illustration of the gas generator illustrated in FIG. 1.

#FIG. 3 is a diagrammatic partially cut away perspective view illustration of helical portions of inner and outer bodies of the gas generator illustrated in FIG. 2.

#Illustrated in FIG. 1 is an exemplary embodiment of an axial flow positive displacement or worm gas generator 100 in a counter-rotatable fan gas turbine engine 10 circumscribed about an engine centerline 8. A counter-rotatable fan section 112 of the engine 10 includes counter-rotatable upstream and downstream fan stages 4, 6 (further illustrated in FIGS. 16-18) and receives inlet airflow of ambient air 9. The upstream and downstream fan stages 4, 6 include upstream and downstream fan blade rows 113, 115, mounted on upstream and downstream fan disks 117, 119, respectively. Downstream of the fan section 112 is a core engine 118 which is the worm gas generator 100.

#The worm gas generator 100 discharges hot gases into a low pressure turbine (LPT) 120 which powers the counter-rotatable upstream and downstream fan stages 4, 6. The low pressure turbine (LPT) 120 illustrated in FIGS. 1 and 13 is a counter-rotatable low pressure turbine (LPT) 121. The worm gas generator 100 is substantially a high pressure spool 133. The counter-rotatable LPT 121 is powered by the hot gases discharged by the worm gas generator 100 into the counter-rotatable LPT 121. As illustrated in FIG. 1, the counter-rotatable LPT 121 has, in serial downstream flow relationship, upstream and downstream low pressure turbines 122, 124 respectively. The downstream low pressure turbine 124 is downstream of the upstream low pressure turbine 122. Combustion gases are discharged from the gas generator 100 into the upstream low pressure turbine 122 having a row of upstream low pressure turbine blades 126. The upstream low pressure turbine blades 126 are drivingly attached to downstream fan blades 130 of the downstream fan blade row 115 of the downstream fan stage 6 by a low pressure outer shaft 132 to form a low pressure outer spool 134 circumscribing the engine centerline 8.

#Combustion gases are discharged from the upstream low pressure turbine 122 into the downstream low pressure turbine 124 having a row of downstream low pressure turbine blades 142. The downstream low pressure turbine blades 142 are drivingly attached to the upstream fan blade row 113 of upstream fan blades 150 of the upstream fan stage 4 by a low pressure inner shaft 152 to form a low pressure inner spool 154 circumscribing the engine centerline 8. Thus, the downstream low pressure turbine 124 is drivingly connected to the upstream fan stage 4 by the low pressure inner shaft 152 and the upstream low pressure turbine 122 is drivingly connected to the downstream fan stage 6 by a low pressure outer shaft 132.