Joint Heavy Lift(JHL)-JSF Lift Fan Derivative Kevin Ferguson Juan Gutierrez Phil Lines Ryan Aaron Chris Bradshaw Jesus Claudio Romen Cross
Scope of Presentation • Mission Overview • Design Characteristics • Initial Engine Design • Final Engine and Fan Design • Driveshaft/Gearbox Design • Internal Design • Analysis/Methodology • Areas of Emphasis
Long Range, Heavy Lift Aircraft • Key requirements: • 300 nm radius of action • Payload: 37,500 lb • Capability to carry vehicles like LAV, MTVR, or HEMAT (internal or external) • Capable of 15 minute cargo on load or off load using only aircrew • Shipboard compatible • Desired speed in excess of 200 kts
Assumptions • Airframe • C-130J-30 Fuselage • Powerplant • 60,000 lbs. Max Thrust per Lift Fan • 40,000 – 45,000 (std hot day) shp • 15,000 lbs. Max Thrust per engine (Hover) • Unknown Max thrust available at cruise • 15,000 lbs thrust required for 0.7 Mach cruise speed • Technology • 2 Lift Fans • High Shaft HP Engines • Current C-17 Cargo Hold Technology
Aircraft Dimensions • Length 113 ft • Span 95.4 ft • Height 32.25 ft • Wing Area 1805 sq ft • Tail Area Horizontal 520 sq ft Vertical 186 sq ft
Sketch • Spot Factor 1.23 x CH53E • 1.5 x CH53E (Objective) • 2.0 x CH53E (Threshold)
Analysis Procedure/Methodology • Initial Engine Calculations/Sizing • Engine Performance • Mission Thrust Requirements • Weight • Weight and Balance Calculation • Mission Comparison
Engine Calculations/Sizing • Used Aircraft Engine Design written by Jack Mattingly for engine sizing requirements to calculate Thrust Req., Wing Area, and Fuel Req. • With Thrust req., used GASTURB to estimate engine performance parameters (TSFC) • Engine performance parameters were then plugged back into MATLAB program to finalize weight, wing area, fuel load, and thrust req.
Engine Performance • 15,000 lbs Thrust for Vertical T/O • 6,000 lbs Thrust for Mach 0.7 Cruise • 7,500 lbs Thrust for Mach 0.54 Ingress • 50,000 shp Required (losses and accessories) JHL Propulsion System 15,000 lbs 15,000 lbs 60,000 lbs 60,000 lbs
Mission Thrust Requirements MISSION PARAMETERTHRUST REQUIRED(lbs) • Takeoff Hover* 155,059 • Acceleration & Climb** 59,429 • Cruise Outbound 11,891 • Ingress*** 43,743 • LZ Landing* 143,256 • LZ Takeoff* 96,841 • Climb & Acceleration** 37,336 • Cruise Inbound 11,885 • Loiter 5,004 • Final Landing* 87,016 • * Denotes Lift-Fans Operating at 100% • ** Denotes Lift-Fans Operating at 40% • *** Denotes Lift-Fans Operating at 25%
Overall Weight • Takeoff Weight • 136,027 lbs. • Fuel • 21,750 lbs. • Payload (w/ crew) • 38,300 lbs. • Empty Weight • 76,777 lbs.
Cargo Bay Design Envelope The Crosshatched Area Represents The 6-Inch Clearance Required In MIL-HDBK-1791 Between The Payload And Aircraft Structure. Required JHLA Cargo Bay Design Envelope 105” • Standard C-130J-30 fuselage utilized • Height accomodates for wood shoring under combat vehicles • Under special circumstances, height can reach – 105 inches • Practical max width for wheeled vehicle at floor – 102 inches • Practical max width for tracked vehicle at floor – 100 inches • Design guidance published in MIL-HDBK-1791
C-17 w/ Similar Cargo Handling Technology Palletized System Retracted
MissionFuel(#)Rng(NM)Wto(#) 1) VTOL(design mission) -w/cargo drop 22,661 600 132,766 2) VTOL -no cargo drop 22,946 600 133,050 3) Ferry(CTOL) -no cargo,w/ fans 22,661 1,050 95,103 4) Ferry(CTOL) -w/cargo,w/fans 22,661 610 132,766 5) Ferry(CTOL) -fuel vice fans 62,161 2124 132,766 6) Ferry(CTOL) -fuel vice cargo 60,161 2,815 132,766 Mission Comparison
Lift Fan Propulsion • Fixed Parameters • Air, Standard Sea Level, Standard Hot Day • Fixes g, Cp, R, Tt1, and pt1 • Inlet, Fan, Nozzle Efficiencies, pd, ef, pn • Variables • Hub to tip Ratio, r • Diameter of Intake, D (Inlet Area, fan size) • Through flow Mach number, MA1 • Fan Pressure Ratio, pf • Results • Thrust, Power, Mass Flow Rate • Exit: Mach Number, Velocity, Area
Euler Turbine Theory Select Fan Tip Speed Mass Flow Hub/Tip Ratio Solidity Blade Aspect Ratio Diffusion Factor Relative Inflow Angle Accounts for Losses Boundary Layer Blockage Inlet and Nozzle Losses Shock Losses Results Diameter Blade Geometry #Blades Blade Chord Blade Spacing Thrust Power Required Pressure Ratio Temperature Ratio Flow Properties Along Blades Flow Angles Diffusion Factors Pressure and Temperature Ratios Shocks Lift Fan Design Analysis
Lift Fan Size • OD ~12ft • Inlet/Diffuser (unknown) • Inlet Guide Vanes (8”) • Fan Blades (6”) • Stator Vanes (10”) • Nozzle (unknown) • Weight ~ 2500 lbs
Controllability Must be able to control the flow to provide fore/aft thrust control. Necessary for transition for takeoff and landing. Shroud Wing Space is insufficient. Louvered Nozzle Practical, but effectively reduces nozzle area as the louvers pivot fore and aft. “Structural Nozzle” Can provide structural strength for wing. Will allow nozzle contraction to take place over a small distance. Allows louvers to direct flow without reducing nozzle area. Adjustable Nozzle Increase nozzle area as louver pivot fore or aft to compensate for effective area reduction. The Fan Nozzle
Lift Fan Control • Variable Geometry Inlet Guide Vanes • Provides rapid thrust changes without changing fan RPM. • Variable Fan RPM • Performance will vary with RPM as engine changes operating RPM.
Engine Design Problem • Engine must be designed to meet shaft power requirements. • LP Turbine is unmatched with the LP compressor. • Able to deliver shaft power for lift fan • LP spool Over-speeds during cruise operations unless controlled. • HP spool forced to operate at lower RPM during cruise • Alternately, designing for cruise leaves HP Spool incapable of producing sufficient flow to produce shaft work necessary for lift fans.
Variable Stator in LP spool turbines Adjust turbine power output to meet shaft work requirement without over-speeding turbine in cruise. Would allow the HP spool to operate at higher RPM, and efficiency, in cruise producing lower TSFC. Currently lack the design tools to be able to predict performance, especially off-design. Secondary Nozzle Limit LP spool RPM to 102% Contract the nozzle to adjust to lower mass flow. Bleed fan air into secondary nozzle (eliminates choking in mixer) to improve performance without losing thrust Variable bypass engine could achieve similar results, limited design tools make designing with this method simpler. Mismatched Engine Solutions
Hover Settings 60/40 Split of Power from LP Turbine 60% to Lift Fan, Accessories and Losses 40% to LP Compressor Nozzle Full Open No Bypass Air Bleed Cruise Settings 5/95 Split of Power from LP Turbine Main Gear Box and Accessory Loads Reduce Nozzle Area 40% Bleed 60% of Bypass Air to Secondary Nozzle Mismatched Engine Solutions
Size Outside Diameter ~ 6.5’ Length ~ 14’ Nozzle Diameter ~ 4’ Weight ~ 8,500-9,500lbs Specifications at Design Point ByPass Ratio ~ 0.3 Fan Pressure Ratio ~ 1.6 Overall Pressure Ratio ~ 41.6 (3.5 LP, 12 HP) Max Burner Temp ~ 3200oR LP Spool RPM ~ 10,000 HP Spool RPM ~ 40,000 LP Spool Mechanical Efficiency Modeled at 0.4 to develop required power for lift fans Design Point High, Hot Hover 4000’ PA 95oF Design Requirements 15,000 lbf Thrust 50,000 shp for Lift Fan Performance at Design Point 15,317 lbf Thrust 49,840 shp for Lift Fan TSFC 1.492 for engine thrust, overall TSFC 0.304 for hover Mass flow ~ 387 lbm/s (465 lbm/s corrected, Inlet) Core Mass Flow ~ 298 lbm/s (128 lbm/s corrected, HPC) The Engines
Drive Shaft Requirements • Transfer 50,000 shp to the each Lift Fan • Operate at 10,000 rpm • Be constructed for a high survivability rate • Maintain the operating speed clear of critical speeds Photo courtesy of the Goodrich Corporation.
Supercritical Analysis • Treat each shaft section as a Clamped-Clamped system. • Design around the requirements (ω = 10,000 rpm and shp = 50,000). • Used an iterative process to obtain optimal critical speed speeds, while maintaining allowable shear stress values for various materials (under Fsy, the Yield Stress in Shear).
Gearboxes • Main Gearbox • Provides no reduction due to the power requirement to the Fans. 1:1 Reduction Ratio • Independent 90 degree gear meshing with the shorter Lift Fan shafts. • Longer shafts from the 119 Engine enter at zero degrees pitch. • Auxiliary Gearboxes • 6:1 Ratio • 90 degree turn upward toward the Lift Fans
Required Technology • Materials • Propulsion System • Lifting Fans • Driveshaft Clutch Assembly
Critical Design Points • Main Engines • Shaft Horsepower and Thrust Requirements • Lifting Fans • Size / Disk Loading / Fitting into wing • Aerodynamic Properties • Need for prepared landing zone / Fan-Wing incorporation • Stability • Fan louvers / Engine Ducts • Gearboxes/Clutch • Main Transmission / Fan gearboxes / Clutch assembly