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Research Papers: Applications

Effect of Engine Operating Conditions and Lubricant Rheology on the Distribution of Losses in an Internal Combustion Engine

[+] Author and Article Information
Riaz A. Mufti1

Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UKriazmufti@hotmail.com

Martin Priest

Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK

1

Corresponding author. Present address: National University of Sciences and Technology, SMME, H-12 Islamabad, Pakistan.

J. Tribol 131(4), 041101 (Sep 25, 2009) (9 pages) doi:10.1115/1.3176988 History: Received July 21, 2008; Revised March 30, 2009; Published September 25, 2009

With new legislation coming into place for the reduction in tail-pipe emissions, the OEMs are in constant pressure to meet these demands and have invested heavily in the development of new technologies. OEMs have asked lubricant and additive companies to contribute in meeting these new challenges by developing new products to improve fuel economy and reduce emissions. Modern low viscosity lubricants with new chemistries have been developed to improve fuel consumption. However, more work is needed to formulate compatible lubricants for new materials and engine technologies. In the field of internal combustion engines, researchers and scientists are working constantly on new technologies such as downsized engines, homogeneous charge compression ignition, the use of biofuel, new engine component materials, etc., to improve vehicle performance and emissions. Mathematical models are widely used in the automotive and lubricants industry to understand and study the effect of different lubricants and engine component materials on engine performance. Engine tests are carried out to evaluate lubricants under realistic conditions but they are expensive and time consuming. Therefore, bench tests are used to screen potential lubricant formulations so that only the most promising formulations go forward for engine testing. This reduces the expense dramatically. Engine tests do give a better picture of the lubricants performance but it does lack detailed tribological understanding as crankcase oil has to lubricant all parts of the engines, which do operate under different tribological conditions. Oil in an engine experiences all modes of lubrication regimes from boundary to hydrodynamic. The three main tribological components responsible for the frictional losses in an engine are the piston assembly, valve train, and bearings. There are two main types of frictional losses associated with these parts: shear loss and metal to metal friction. Thick oil in an engine will reduce the boundary friction but will increase shear losses whereas thin oil will reduce shear friction but will increase boundary friction and wear. This paper describes how engine operating conditions affect the distribution of power loss at component level. This study was carried out under realistic fired conditions using a single cylinder Ricardo Hydra gasoline engine. Piston assembly friction was measured using indicated mean effective pressure method and the valve train friction was measured using specially designed camshaft pulleys. Total engine friction was measured using pressure-volume diagram and brake torque measurements, whereas engine bearing friction was measured indirectly by subtracting the components from total engine friction. The tests were carried out under fired conditions and have shown changes in the distribution of component frictional losses at various engine speeds, lubricant temperatures, and type of lubricants. It was revealed that under certain engine operating conditions the difference in total engine friction loss was found to be small but major changes in the contribution at component level were observed.

Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Engine drive train layout with fitted pulley torque transducers

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Figure 2

Average camshaft friction over cam profile period only (SAE 0W20)

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Figure 3

Average camshaft friction over complete cam cycle, SAE 0W20

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Figure 4

Effect of SAE 0W20 and SAE 5W30 on the average friction torque, engine speed 1500rpm

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Figure 5

Average piston assembly friction, SAE 0W20 and SAE 5W30

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Figure 6

Bearing friction power loss for SAE 0W20 lubricant

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Figure 7

Bearing friction power loss, 800rpm, SAE 0W20 and SAE 5W30

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Figure 8

Total engine and component friction at an engine speed of 800rpm with an SAE 0W20 lubricant

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Figure 9

Contribution of engine component friction at an engine speed of 800rpm, lubricant inlet temperature 24°C, SAE 0W20

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Figure 10

Contribution of engine component friction at an engine speed of 800rpm, lubricant inlet temperature 80°C, SAE 0W20

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Figure 11

Total engine and component friction at an engine speed of 1500rpm with an SAE 0W20 lubricant

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Figure 12

Total engine and component friction at an engine speed of 2000rpm, SAE 0W20 lubricant

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Figure 13

Contribution of engine component friction at an engine speed of 1500rpm, lubricant inlet temperature 24°C, SAE 0W20

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Figure 14

Contribution of engine component friction at an engine speed of 2000rpm, lubricant inlet temperature 24°C, SAE 0W20

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Figure 15

Contribution of engine component friction at an engine speed of 1500rpm, lubricant inlet temperature 80°C, SAE 0W20

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Figure 16

Contribution of engine component friction at an engine speed of 2000rpm, lubricant inlet temperature 80°C, SAE 0W20

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Figure 17

Total engine and component friction at an engine speed of 800rpm, SAE 5W30 lubricant

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Figure 18

Total engine and component friction at an engine speed of 1500rpm, SAE 5W30 lubricant

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Figure 19

Total engine and component friction at an engine speed of 2000rpm, SAE 5W30 lubricant

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Figure 20

Contribution of engine component friction at an engine speed of 1500rpm, lubricant inlet temperature 24°C, SAE 5W30

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Figure 21

Contribution of engine component friction at an engine speed of 1500rpm, lubricant inlet temperature 80°C, SAE 5W30

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