Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64C—AEROPLANES; HELICOPTERS
  • B64C11/00—Propellers, e.g. of ducted type; Features common to propellers and rotors for rotorcraft
  • B64C11/02—Hub construction
  • B64C11/14—Spinners
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
  • F02C6/00—Plural gas-turbine plants; Combinations of gas-turbine plants with other apparatus; Adaptations of gas-turbine plants for special use
  • F02C6/20—Adaptations of gas-turbine plants for driving vehicles
  • F02C6/206—Adaptations of gas-turbine plants for driving vehicles the vehicles being airscrew driven
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
  • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
  • F02C7/12—Cooling of plants
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T50/00—Aeronautics or air transport
  • Y02T50/60—Efficient propulsion technologies, e.g. for aircraft

Definitions

• This invention relates generally to gas turbine driven propeller systems for aircraft propulsion and more specifically to an improved arrangement for ducting hot exhaust gasses through and out of the engine nacelle with minimum interference with downstream located propellers.
• Gas turbine driven propeller systems for aircraft propulsion i.e., turboprops
• turboprops have been generally known in the industry for a long time but recently there has been a renewed interest in such configurations because of several heretofore unappreciated advantages over conventional jet engines.
• Turboprops may not fly as fast as jets but can be much more fuel efficient, especially on smaller planes. In addition, turboprops are generally more effective on shorter flights since they typically have higher rates of climb.
• One problem with conventional turboprops has been their high noise level but recent development of "pusher" configura- tions, in which the propellers are placed behind the engine and cabins, have essentially eliminated the problem and produced an exceptionally quiet cabin.
• pusher configuratio there are several new problems created by utilizing such a pusher configuratio .
• turboprop engines Another problem with turboprop engines involves proper cooling of the engine nacelle and internal com ⁇ ponents. Since the propeller system by itself cannot usually supply an adequate flow of cooling air, especially at low air speeds on the ground during idle and wnen the propellers are "feathered", additional internal cooling methods are usually required. However, the additional weight and power consumption of such devices are detrimental to overall efficiency. - 3 -
• Another object of this invention is to provide an improved method of cooling a turboprop engine at low air speeds by pulling air through the engine nacelle.
• the present invention aims to overcome the dis ⁇ advantages of the prior art as well as offer certain advan- tages by providing a turboprop engine having a novel exhaust duct structure which includes a rearwardly-directed internal gas channel, which directs the hot products of combustion from the turbine outlet ports into a nozzle-like momentum exchange chamber where warmed nacelle cooling air is educ- ted into the gas stream.
• the combined gas stream is forced through a downstream annular exhaust passage formed around and integral with the rotatable spinner which covers the pusher propeller hub assembly.
• Within the annular exhaust passage are hollow, aerodynamically shaped cuffs circu - scribing each propeller blade root to protect them from the hot gas stream. More importantly, the annular passage and cuffs define a fan structure which, due to the rotation of the spinner assembly, pulls the gas stream from the momentum exchange chamber.
• the present invention not only provides an aero- dynamically smooth nacelle without protruding exhaust horns (which reduces aerodynamic drag by about 102) but also ensures adequate cooling " of the turboprop engine and com ⁇ ponents during low air speed operation, such as ground idle or taxiing, wherein the mass air flow through the turbine would not, without the propeller driven fan, be sufficient to aspirate enough cooling air through the nacelle.
• the exhaust gas stream is flowing fast enough that little or no power need be consumed by the fan. While the shape and angle of the cuffs in the fan may be designed to provide various ratios of jet thrust to propeller thrust, it is preferred that the overall efficiency, not the combined thrust, is maximized at the designed cruising speed.
• FIG. 1 is a side elevational view, in partial cross-section, illustrating a turboprop engine incorporating the present invention
• FIG. 2 is an enlarged view of the rearward portion of FIG. 1 showing additional details
• FIG. 3 is a transverse cross-sectional end view of the engine taken along line 3-3 of FIG. 2;
• FIG. 4 is a transverse cross-sectional end view of the spinner taken along line 4-4 of FIG. 2.
• FIG. 1 illustrates a partial sectional view through a pusher turboprop engine assembly incorporating the present invention.
• the assembly generally comprises a gas turbine engine (10) surrounded by an aerodynamic housing or nacelle (15) and connected, through a speed reducing gear box (20) on its aft end, to a standard propeller mechanism (30) which is surrounded by a rotatable spinner assembly (50).
• the turbine engine (10) includes an elongate fore-and-aft extending engine housing (11) defining a main air inlet port (12), in the forward end, and having at least one, but preferably two, exhaust outlet ports (13) located on each side of the housing near the aft end.
• the housing (11) contains the typical compressor, combustor, and turbine sections (14) along with their associated operating components (not shown) for producing a flow of high temperature pressurized combustion products and mechanical power.
• the engine (10) also includes the usual accessories, such as a starter (23), generator (24), oil cooler (25), and other well-Wr.ovn operating components.
• Mechanical power is extracted from the engine (10) by an output shaft (21) through an in-line gear box (20) located rearwardly of the exhaust outlet ports (13).
• the nacelle (15) includes an outer sheet metal skin or wall (16) which surrounds the engine (10) and gearbox (20) with an aerodynamically favorable outward configuration.
• a nacelle cavity (17) is thereby formed between the outer wall (16) and the engine housing (11).
• the lower portion of the nacelle (15) also includes a cooling air inlet (26) which directs air through the engine oil cooler (25) and thence rearwardly through cooling air exhaust duct (27) towards and out the aft end of the nacelle as will be explained in more detail later.
• the forward end of the nacelle (15) includes a main air inlet (18), communi- eating combustion air to the turbine inlet port (12) , while the aft end of the nacelle terminates at a transverse plane located between the gearbox (20) and the spinner assembly (50).
• the aft end of the nacelle includes an annular, open-ended momentum exchange chamber (45) formed between the nacelle skin (16), or more preferably a sheet metal attachment thereto (44) , and the aft bulkhead (43) surrounding the gearbox output shaft (21).
• This chamber (45) is open rearwardly to duct work (51) in the spinner assembly as explained later and open forwardly so as to be in flow alignment with: first, an exhaust transition duct (42) communicating to the turbine outlet port(s) (13); second, a nacelle air injector inlet (46) communicating to the nacelle cavity (17); and third, a cooling air injector inlet (47) communicating to the cooling air exhaust duct (27).
• the exhaust transition ducts (42) are constructed to terminate in two semicircular outlets arranged on each side half of the nacelle, while the nacelle air injector inlet (46) and the cooling air injector inlet (47) are semicircular openings arranged in the top half and bottom half, respectively, of the nacelle.
• a rotatable spinner assembly (50) is located aft of the nacelle (15) and includes an optional outer wall portion (53), which is configured to be an aerodynamic extension of the nacelle, and a smaller, rearwardly con ⁇ vergent, conical inner portion (52), which provides en ⁇ vironmental protection to the propeller mechanism (30).
• the outer wall portion (53) when present, extends about 1/2 or 2/3 of the length of the inner portion (52). However, it may may be omitted to reduce resistance to exhaust flow.
• annular exhaust passage (51) Between the inner portion (52) and the outer portion (53) is an annular exhaust passage (51) which is generally aligned with the momentum exchange chamber (45). Within the annular exhaust passage (51) are several radially extending, hollow, airfoil-shaped cuff members (55) which loosely surround the root portion (33) of the propeller blades (31). As shown more clearly in FIG. 4, the exhaust passages (51) open into the atmosphere aft of the cuff- protected propeller blades (31). A spinner bulkhead (56) is preferably provided to protect the interior of the spinner, which contains the propeller mechanism (30) , from the environment.
• the propeller mechanism (30), shown in FIG. 1, is well-known in the art and generally includes a hub (32) containing the pitch control machinery (not shown) and three to six radially extending propeller blades (31) .
• Each of the blades (31) are attached to the hub (32) at its root (33) and passes radially through an opening in the spinner inner wall (52) , through the hollow cuff member (55), and finally through an opening (54) in the spinner outer wall (53) when such is provided.
• the operation of this turboprop engine is similar in many respects to that of prior art engines except for the handling of the air and exhaust flow as discussed below.
• the turbine engine (10) ingests air and fuel into the gas generator portion (14) , the details of which are not shown, to produce mechanical power to drive the propellers and a high temperature, high velocity exhaust jet.
• the turbine exhaust flows from the outlet ports (13), around the gearbox (20) through transition ducts (42) and into the momentum exchange chamber (45) where its kinetic energy or momentum is used to aspirate warmed air from the two closely adjacent injectors (46) and (47) before exiting through the spinner duct (51) as a rearwardly directed jet.
• the cooling air injector (47) draws air through the engine oil cooler (25) to extract energy therefrom, while the nacelle injector (46) draws warm air from the -9 - cavity (17) surrounding the engine and accessories.
• Suf ⁇ ficient cooling air is easily provided during normal flight operation because of the large mass flow through the turbine (10) and into the momentum exchange chamber (45).
• the rotating spinner exhaust passage (51) acts like a fan, because of the blade-shaped cuff members (55), and pulls air through the momentum exchange chamber (45).
• each propeller blade root (33) While there is at least one cuff member (55) around each propeller blade root (33) , it may be advan ⁇ tageous to include additional blade shaped members in the exhaust passage (51), especially when the number of pro- pellers is few, e.g. three, or the minimum design speed of the spinner (50) is slow, so that sufficient cooling air flow is maintained.
• the propulsion engine arrangement described by mounting the propeller assembly to the rear of the turbine engine enables the engine to have a conventional intake unimpeded by the presence of a propeller and gearbox while at the same time provides a suitable method of ducting the engine exhaust to the atmosphere without interference with the aft-mounted propellers or unnecessary loss of jet thrust.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Aviation & Aerospace Engineering (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Turbine Rotor Nozzle Sealing (AREA)

Applications Claiming Priority (4)

Publications (1)

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• 1989
  • 1989-03-31 BR BR898907238A patent/BR8907238A/pt unknown
  • 1989-03-31 JP JP1506454A patent/JPH03500157A/ja active Pending
  • 1989-03-31 EP EP89906885A patent/EP0440640A1/de not_active Withdrawn
  • 1989-03-31 WO PCT/US1989/001370 patent/WO1989010300A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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