Embed Size (px)
Citation preview
Counter-Rotating Motor
Matt Angle3 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-42... 2.8 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
0 1 2 3 4 5 6 7 8 9 10
-1.00E-005
-8.00E-006
-6.00E-006
-4.00E-006
-2.00E-006
0.00E+000
2.00E-006
Shaft Deflection
Shaft Centerlinex1x2x3x4
Shaft Length [m]
De
flect
ion
[m]
Fp
Mp
Fp
Mp
Hydrostatic Bearing Performance Numbers
n 2
diameter [m,mm] 1.27 1270
efficiency % 25
bushing length [m,mm] 2.03 2032
supply spiral height [m,mm] 0.4 400
gap factor 20
gap [m,um] 3.47E-05 34.66
shaft deflection um 1.73
pocket length Lp [m,mm] 1.53 1532
Aeff [m^2, mm^2] 10.78 1.08E+007
ps [N/m^2] 1.50E+06
k per bushing [N/m, N/micron] 3.50E+11 349988.37
mu [Nsec/m^2] 8.90E-04
land width [m,mm] 0.1 100
l [m] 3.99
Ro 3.22E+009
flow per bushing [m^3/sec, l/min] 4.66E-004 27.99
Hydrostatic Bearing Performance Numbers
Ao [m^2] 1.38E-04
u [m/s] 3.37
D [m,mm] 1.27 1270
Al [m^2] 0.8
omega [RPS,RPM] 15.71 150
shear power per bushing [W] 20947.65
pumping power per bushing [W] 699.75
Hp/Hfr 0.03
surface speed m/s 9.97
axial water speed m/s 1.69
Re from tangential speed 0.39
radial load capacity per bushing [N] 729615
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
