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RESEARCH PAPERS

Experimental Evaluation of Piston-Assembly Friction Under Motored and Fired Conditions in a Gasoline Engine

[+] Author and Article Information
Riaz A Mufti1

Institute of Tribology, School of Mechanical Engineering, The University of Leeds, Leeds LS2 9JT, UKmuftr1@bp.com

Martin Priest2

Institute of Tribology, School of Mechanical Engineering, The University of Leeds, Leeds LS2 9JT, UKM.Priest@leeds.ac.uk

1

Current address: Castrol Technology, Centre, Pangbourne, Reading RG8 7QR, UK

2

Corresponding author.

J. Tribol 127(4), 826-836 (Aug 06, 2004) (11 pages) doi:10.1115/1.1924459 History: Received March 10, 2004; Revised August 06, 2004

Piston-assembly friction measurement has been carried out on a single-cylinder gasoline engine using the IMEP (indicated mean effective pressure) method at realistic engine speeds and loads without any major engine modifications. Instantaneous and mean piston-assembly friction were measured under motored and fired conditions at different lubricant temperatures. The forces acting on the piston assembly were carefully determined by measuring the cylinder pressure, crankshaft angular velocity, and strain in the connecting rod. The difference between the resulting gas pressure, inertia, and connecting rod axial forces acting on the piston yields the piston-assembly friction. To achieve this with confidence, an advanced instrumentation, telemetry, and data acquisition system was designed and developed, giving special attention to the synchronization and simultaneous sampling of analog and digital channels. Experiments are reported for piston-assembly friction at a range of engine operating conditions with different lubricant formulations, with and without a friction modifier.

Copyright © 2005 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Forces acting on piston assembly and connecting rod

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Figure 2

Sectioning of the connecting rod for inertial calculations

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Figure 3

Crankshaft angular acceleration under motored and fired conditions, 1000 rpm

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Figure 4

Effect of crankshaft angular acceleration on piston assembly axial acceleration under motored and fired conditions, 1000 rpm

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Figure 5

Piezoresistive pressure transducer for cylinder pressure pegging

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Figure 6

Installation arrangement of the miniature absolute pressure transducer

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Figure 7

1 mm long and 0.5 mm bore pegging channel at 120 deg after TDC

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Figure 8

Pressure measured by liner absolute pressure transducer

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Figure 9

Pumping loop measured using water-cooled cylinder pressure transducer, Kistler 6067B

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Figure 10

Pumping loop measured using uncooled cylinder pressure transducer, Kistler 6121

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Figure 11

Connecting-rod stress calculated using finite element analysis, under tensile loading

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Figure 12

24-wire grasshopper linkage

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Figure 13

Connecting rod calibration using hydraulic Dartec Universal Testing Machine

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Figure 14

Instrumented connecting rod static and dynamic calibration graph

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Figure 15

Piston-assembly friction evaluation flow chart

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Figure 16

Piston-assembly reciprocating inertial force

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Figure 17

Connecting rod section B reciprocating inertial force

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Figure 18

Piston-assembly friction force, engine speed 800 rpm, 14 load, lubricant SAE 0W20 without FM (friction modifier)

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Figure 19

Piston-assembly friction at engine speed 800 rpm, load 14, lubricant SAE 5W30 with FM

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Figure 20

Piston-assembly friction force, engine speed 1500 rpm, 12 load, SAE 0W20 without FM

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Figure 21

Comparison of piston-assembly friction power loss using SAE 0W20 without FM and SAE 5W30 lubricants

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Figure 22

Engine speed 80 rpm, 14 load, lubricant temperature 24 °C, SAE 0W20 without FM

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Figure 23

Engine speed 80 rpm, 14 load, lubricant temperature 80 °C, SAE 0W20 without FM

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Figure 24

Engine speed 2000 rpm, 12 load, lubricant temperature 80 °C, SAE 0W20 without FM

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Figure 25

Piston-assembly friction under both motored and fired conditions, lubricant SAE 0W20

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