Counter-Rotating Motor Matt Angle 3 March 2010

Project Updates February 26 Meeting with ONR in DC Canceled due to Flight Cancellations and Rescheduled for March 19 After Sending ONR Slides, Weekend was Spent Snowboarding in the Best Conditions of the Season (5'-ish of Fresh Snow at Killington) Returned on Monday to Find $100k of Funding for Project Note to Self: Must do this More Often With Funding, Project has Become Fundamentally Different

Changes to Project Project has become Test Bed for Large Shaft Bearings DC Permanent Magnet Motor Higher Flux Density of Permanent Magnets Allows a Smaller Motor at the Same Power Level Example: MagMotor BFA kW in 4.6” Diameter, 9.13” Length, ~20 lbs Porous Carbon Spherical Air Bearings Developed at Oak Ridge Y-12 Plant Flow Compressed Air through Porous Carbon Lining to Provide Uniform Support to Sphere or Hemisphere Function as Both Radial and Thrust Bearings Eliminate Requirement to Seal End of Shaft in Submerged Environment

Competitive Analysis Fundamentally New Concept Advantages of Contra-Rotating Propellers Usually Lost to Mechanical Complexity Several Companies Produce Close Products ABB IHI Marine

ABB CRP Azipod Contra-Rotating Propellers Mounted to Two Shafts on Common Axis Current Most Efficient Industry Example Unit Shown Produces 17.6 MW Current Most Efficient Industry Example

Functional Requirements and Analytical Model Self-Compensating Hydrostatic Bearings Shaft Bending and Bearing Performance Do We Need Spherical Bearings? Thrust Capacity Simplified with Spherical Bearings Cantilevered Motor

Self-Compensating Hydrostatic Bearings How it Works – When shaft is displaced, supply grooves are blocked, pressure reduced in pockets on opposite side of shaft. – Pressure difference produces restoring force. Supply Grooves – Oriented on inside of bearing assembly. – Extend ~180° to pocket on opposite side of bearing. – Function as restrictors. – Resistance is always optimized for gap clearance. – Are self-cleaning and difficult to clog. Pockets – Bear load of shaft. – Are fed by supply channels. – Restrictor and bearing fluid resistances are always balanced because they both depend on the radial clearance (gap).

Shaft Bending Analysis Shaft Acted Upon by Propeller with Force Fp and Torque Mp Shaft Bent, Causing Changes in Bearing Gaps Bending Analysis Fed in to Bearing Design Spreadsheet Simulation Assumes Bearing Gaps 20x Bending Displacement For Future, Must Add Cantilevered Motor Forces Fp Mp Fp Mp

Hydrostatic Bearing Performance Numbers n2 diameter[m,mm] efficiency%25 bushing length[m,mm] supply spiral height[m,mm] gap factor20 gap[m,um]3.47E shaft deflectionum1.73 pocket lengthLp [m,mm] Aeff[m^2, mm^2] E+007 ps[N/m^2]1.50E+06 k per bushing[N/m, N/micron]3.50E mu[Nsec/m^2]8.90E-04 land width[m,mm] l[m]3.99 Ro3.22E+009 flow per bushing[m^3/sec, l/min]4.66E

Hydrostatic Bearing Performance Numbers Ao[m^2]1.38E-04 u[m/s]3.37 D[m,mm] Al[m^2]0.8 omega[RPS,RPM] shear power per bushing[W] pumping power per bushing[W] Hp/Hfr0.03 surface speedm/s9.97 axial water speedm/s1.69 Re from tangential speed0.39 radial load capacity per bushing[N] water CP[kJ/kg-C]4180 mass flow rate[kg/s]0.47 delta T[C]11.1

DFMA Approach Double-Hemispherical Air Bearing Design Handles Bi-Directional Thrust Eliminates Sealing Problems and Shaft Alignment Issues Desirable Noise Characteristics  Bubbles are Random and Aperiodic Cantilevered Motor Eliminates Bearing Considerations in Motor Eliminates Major Source of Noise Production  Rigidly Mounted Stators Couple Fundamental Frequency Bending to Ship Hull  Periodic Noise at Motor Frequency is Easily Detectable by Enemy Ships and is Used to Locate Targets