Laser Surface Texturing Izhak Etsion Dept. of Mechanical Engineering Technion, Haifa 32000 Israel etsion@technion.ac.il
LST Regular Micro-Surface Structure in the Form of Micro-dimples
Hydrodynamic pressure distribution over a single protrusion F P a P a U P low U ; F = 0 high U ; F > 0 P a P c
Why dimples? - complicated etching technology - high wear - high leakage (seals) protrusions dimples - simple & cheap laser technology - lower wear - low leakage/spacing
Film Thickness and Geometry of of Micro-Dimples h 0 2r p h(x,z) h p U z x 2r 1 2r 1 dimensionless minimum clearance : δ = h ( 2r ) micro-dimple aspect ratio : ε = h p 0 (2r p p = h h = H dimensionless local film thickness : H 0 ) ( ε,δ )
A Mechanical Face Seal
Ring on Ring Scheme Rotating Ring without Laser Treatment Clearance Stationary Ring with Laser Treatment LOAD
Test rig arrangement
Friction Torque vs. Face Loading for Textured and Non-textured Seals in Water 25 Torque (in-lbs) 20 15 10 Lapped Textured 5 45 65 85 105 125 145 165 185 Unit load (psi)
Schematic of a partial laser surface textured mechanical seal h(x,z) h p c d i d p d o
Partial (on the Right) and Full (on the Left) Face Laser Texturing
Friction Torque vs. Sealed Pressure for Non-textured and Partial Textured Seals 1 0.8 Untextured Torque [Nm] 0.6 0.4 0.2 Textured 0 0 5 10 15 20 25 Pressure [barg]
Field Test with Water Pump
Field Test with Water Pump
Pressure Distribution in a Stepped Slider (a), and in a Surface Textured Parallel Slider (b) P P U U a b
Results for Infinitely Long Slider. B = 50 ; δ = 0.2 ; Sp = 50% 18 16 14 b p b U 12 Pav 10 8 6 4 2 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 ε = 0.15 ε = 0.2 ε = 0.25 ε = 0.3 ε = 0.35 α
Bearing Mating Surfaces Showing a Textured Flat Stator and a Flat Rotor
Unidirectional (a) and a bi-directional (b) versions of the partial LST thrust bearing a b
Schematic of the Test Rig
Comparison of Partial LST Bearings and a Non-textured Bearing Friction at 1500 rpm 0.065 0.055 Friction coefficient 0.045 0.035 0.025 Bi-directional Untextured 0.015 Unidirectional 0.005 150 200 250 300 350 400 450 500 Load, N
Internal Combustion Engines Improved lubrication, speed and power Lower fuel consumption Reduced exhaust levels and operating temperatures Minimized cylinder wear and mechanical losses
Piston Group
Laser Textured Piston Ring Piston Textured Piston Ring Cylinder Liner
Laser Textured Piston Ring Textured Friction Surface Full Textured Piston Ring Segment Partially Textured Piston Ring Segment
Force Balance Engine P(τ) Cylinder Piston P e =P(τ)+P spring Combustion Chamber P(τ) P = 0 Piston Rings P h
Reciprocating Test Rig
Piston Rings Holder
Piston Rings and Cylinder Liner
Test Results Average Friction Force, N 3.50 3.25 3.00 2.75 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 Untextured Fully textured Partially textured P= 0.3 MPa 500 550 600 650 700 750 800 850 900 Angular Velocity, RPM
Ford transit engine on the test bench
Cross sections of cylindrical (a) and barrel shape (b) Cr coated piston rings (a) (b)
Partial LST cylindrical face piston ring
Engine specific fuel consumption vs. engine speed. Series 1: Barrel, chrome coated, baseline, Series 2: Flat, chrome coated, laser treated, Series 3: Flat, no chrome, laser treated Series 1 Series 2 Series 3 bsfc [(g-fuel/s)/(kw*hr)] 250 245 240 235 230 1400 1600 1800 2000 2200 Engine Speed [rev/min]
Piston
Piston pin and bearing
Tape moving over a LST guide
Impact of LST on Lubrication Regime Transition
Distribution of researchers by countries of origin Algeria Argentina Brazil Czech Republic Finland France Germany Greece Israel Japan Netherlands Poland Sweden Switzerland Turkey UK USA
Summary Laser surface texturing has emerged in recent years as a viable means of enhancing tribological performance. The laser is extremely fast, clean to the environment and provides excellent control of the shape and size of the micro-dimples, which allows realization of optimum designs. Several applications were shown to benefit from LST. These include dynamic sealing, thrust bearings, magnetic recording and internal combustion engines. Most of this work is still in a stage of theoretical modeling and laboratory testing. LST was successfully applied to mechanical seals resulting in up to 60% friction reduction and threefold increase in seal life in pumps operating in the field This success is attributed to the theoretical modeling of LST under full fluid film conditions, which gave good agreement with laboratory tests and permitted optimization of the LST parameters. It is envisaged that with the continuing R&D effort more applications may benefit from LST in the coming years.
Comparison of Theoretical and Experimental Results of LST Mechanical Seal 0. 3 Average Pressure (MPa) 0. 25 0. 2 0. 15 0. 1 0. 05 Theoretical Experimental 0 0 1 2 3 4 5 6 Clearance (µm)
Enlarged View of Rotor - Carbon Specimen Interface
Torque vs. Time (Baseline rotor) BASELINE ROTOR 24 15000 22 20 Torque Average Torque RPM 14000 13000 12000 18 RPM 11000 16 10000 Torque (N-m * 100) 14 12 10 9000 8000 7000 6000 RPM 8 5000 6 4 2 3.45kPa 6.90kPa 10.34kPa 13.79kPa 17.24kPa 20.68kPa 24.13kPa 27.58kPa 34.47kPa 14000 RPM 4000 3000 2000 1000 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 0 ELAPSED TIME (MINUTES)
Torque vs. Time (LST rotor) ROTOR w/ LST 24 15000 22 20 18 Torque Average Torque RPM RPM 14000 13000 12000 11000 TORQUE (N-m * 100) 16 14 12 10 8 6 4 2 0 3.45kPa 6.90kPa 10.34kPa 13.79kPa 17.24kPa 20.68kPa 24.13kPa 27.58kPa 34.47kPa 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 ELAPSED TIME (MINUTES) 14000 RPM 10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 RPM
Average Torque vs. Time, Comparison of Baseline & LST Rotors at 12,000 rpm 12 BASELINE & LST ROTORS 3.45 kpa 6.90 kpa 10.34 kpa 13.79 kpa 17.24 kpa 20.68 kpa 10 TORQUE (N-m * 100) 8 6 4 BASELINE ROTOR LST ROTOR 2 3.45 kpa 6.90 kpa 10.34 kpa 13.79 kpa 17.24 kpa 20.68 kpa 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 ELAPSED TIME (MINUTES)
Typical Pressure Distributions and Maximum Load Capacity Tapered W=0.16 Stepped W=0.205 0.4 < S p < 0.65 Parallel LST W=0.16S p
A Comparison of Partial LST Bearing and Non-textured Bearing Performance 14 12 10 n = 3000 rpm Textured Nontextured Clearance, µm 8 6 4 n = 1500 rpm 2 0 150 200 250 300 350 400 450 500 Load, N