A Study of Friction Reduction by ‘Soft Skirt’ Piston

Hoshikawa, Jun; Kato, Kiminari; Miyamoto, Kazushi; Higashi, H.; Ito, Akemi

doi:10.4271/2011-01-2120

Cited by 6 publications

(5 citation statements)

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“…Over the past few years, this has become an even greater influence due to engine downsizing, whilst maintaining or increasing the overall output (increasing specific output) in order to reduce fuel consumption, thus emissions. The effect of crown stiffness on friction and contact patch has been recently experimentally highlighted by Hoshikawa et al 11 It is, therefore, very important to introduce a technique that is sensitive to the more compliant pistons and their skirts and sufficiently accurate to predict the piston skirt's load carrying capacity.…”

Section: Piston Body Distortionmentioning

confidence: 99%

“…The in-service shape is much harder to control as this is the result of various mechanical distortions. Recently, Hoshikawa et al 11 showed, through experimental techniques, the effect of stiffness modification and compared it with observation of frictional changes using a floating liner set up. Qualitative observations from a visual liner were also made.…”

Section: Introductionmentioning

confidence: 99%

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Lubrication of a flexible piston skirt conjunction subjected to thermo-elastic deformation: A combined numerical and experimental investigation

Littlefair

Cruz

Mills

et al. 2013

Proceedings of the Institution of Mechanical Engineers, Part J:

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The piston-cylinder conjunction accounts for nearly 50% of all the parasitic frictional losses in an IC engine of which the piston skirt accounts for nearly half of these losses. Consequently, part-circumferential short skirted compliant pistons have become a development trend, particularly for high-performance engines. Another trend has been the use of light weight moving parts to reduce inertial imbalance. This has led to the use of shorter lighter pistons constructed from lower density materials, such as aluminium. These higher power density pistons typically operate at elevated temperatures and undergo significant mechanical and thermal distortions due to the relatively high thermal expansion coefficients. As a result thermo-mechanical distortion of the skirt plays an important role in controlling the clearance gap between the skirt and the liner and makes the analysis, particularly skirt deformation, a computationally intensive procedure. This paper presents a semi-automatic methodology for the prediction of piston skirt thermo-mechanical deflection, which incorporates skirt deformation as well as piston crown compliant contribution to the skirt-liner clearance. This procedure is based on the creation of a compliance matrix and its intricate manipulation, significantly reducing the simulation run times. Integration of this approach with the numerical solution of Reynolds equation leads to an accurate prediction of film thickness. In addition, an array of ultrasonic sensors is used to directly measure the conjunctional lubricant film thickness in a non-invasive manner. The predictions and measurements show good conformance, an approach not hitherto reported in literature.

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Section: Piston Body Distortionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Lubrication of a flexible piston skirt conjunction subjected to thermo-elastic deformation: A combined numerical and experimental investigation

Littlefair

Cruz

Mills

et al. 2013

Proceedings of the Institution of Mechanical Engineers, Part J:

View full text Add to dashboard Cite

show abstract

“…The in-service shape is much harder to control as this emerges as a result of various mechanical distortions. Recently, Hoshikawa et al [13] showed, through experimental techniques, the effect of stiffness variations and compared it with the analysis on frictional changes using a floating liner set-up. Qualitative observations from a visual liner were also made.…”

Section: Introductionmentioning

confidence: 99%

Transient Tribo-Dynamics of Thermo-Elastic Compliant High-Performance Piston Skirts

et al. 2013

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Advanced piston technology for motorsport applications is driven through development of lightweight pistons with preferentially compliant short partial skirts. The preferential compliance is achieved through structural stiffening, such that a greater entrainment wedge is achieved at the skirt's bottom edge through thermo-elastic deformation, whilst better conforming contact geometry at the top of the skirt. In practice, the combination of some of these conditions is intended to improve the load-carrying capacity and reduce friction. The approach is fundamental to the underlying ethos of race and high-performance engine technology. Contact loads of the order of 5 kN and contact kinematics in the range 0-35 m/s result in harsh transient tribological conditions. Therefore, piston design requires detailed transient analysis, which integrates piston dynamics, thermo-elastic distortion and transient elastohydrodynamics. The paper provides such a detailed analysis as well as verification of the same using noninvasive ultrasonic-assisted lubricant film thickness measurement from a fired engine under normal operating conditions, an approach not hitherto reported in literature. Good agreement is noted between measured film thickness and predictions.

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“…This fuel conversion efficiency (η f ) is calculated with Equation (1.1), where P is power,ṁ f is the mass flow rate of fuel, and Q LHV is the lower heating value of fuel. To help achieve the CAFE standards, there is continuous research to improve the overall fuel conversion efficiency in a number of different areas including friction reduction [7,8,9], volumetric efficiency (η v ) improvements [10,11,12,13], advanced combustion systems [14,15,16,17,18], and waste heat recovery (WHR) [19,20,21,22]. By increasing the fuel conversion efficiency and meeting the CAFE standards, the depletion of the global fuel supply could be decelerated and the fuel expenditure by the end user could be decreased.…”

Section: Lists Of Abbreviationsmentioning

confidence: 99%

“…The baseline remaining friction energy and the pumping work with the percent change due to the TEG can be found in for the air density and throttle position can be seen in Table 4. 8. Because the throttle cable was removed numerous times while the engine was being serviced, the data for the throttle position and change in throttle position should only be used for overall trends.…”

Section: Remaining Friction Energy and Pumping Workmentioning

confidence: 99%

Novel Automotive Waste Heat Recovery Techniques

Armstead¹

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A Study of Friction Reduction by ‘Soft Skirt’ Piston

Cited by 6 publications

References 0 publications

Lubrication of a flexible piston skirt conjunction subjected to thermo-elastic deformation: A combined numerical and experimental investigation

Lubrication of a flexible piston skirt conjunction subjected to thermo-elastic deformation: A combined numerical and experimental investigation

Transient Tribo-Dynamics of Thermo-Elastic Compliant High-Performance Piston Skirts

Novel Automotive Waste Heat Recovery Techniques

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