Sounding out engine efficiency: Ultrasound scan

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  • Published: Dec 15, 2012
  • Channels: Atomic
thumbnail image: Sounding out engine efficiency: Ultrasound scan

Get your motor running

Piezoelectric sensors to monitor lubricant film thickness at piston-cylinder contacts in a fired engine

Atomic absorption spectroscopy might be used to analyse the metallic content of engine residues but researchers in the UK have now turned to ultrasound to scan engine components with a view to facilitating the design of new components that are more efficient and generate lower carbon emissions.

One of the most important seals in an internal combustion engine is that between the piston ring and the lining of the cylinder. At this interface lubricant is critical to an efficient and clean interface but so too is the way in which the various components interact. Now, Robin Mills, Emin Yusuf and Rob Dwyer-Joyce of the University of Sheffield have turned to the ultrasound scan to allow them to observe the interaction between components and lubricant while the piston is firing. Ultrasound allows them to observe the processes and measure lubricant film thickness in an entirely non-invasive manner that does not interfere with the engine's working. 

Piston head slap

The team explains that the placement of low-cost piezoelectric elements bonded to the outside of a four-stroke, single cylinder engine allows them to generate a pattern of short duration voltage pulses and to record the reflections from within the cylinder as it works through its stroke cycle. The team was able to image the individual ring and skirt contacts between cylinder and piston even when the engine was running at full speed. From the resulting images the team was able to obtain a direct measurement of the thickness of the lubricant film. The same measurements also allowed them to observe such secondary movements of the piston within the cylinder as "piston slap".

"There is a real urgency, now, to improve energy consumption in cars, explains Dwyer-Joyce, who is Professor of Lubrication Engineering in the University's Department of Mechanical Engineering. "Our method will allow engine manufacturers to adjust lubrication levels with confidence and ensure they are using the optimum level for any particular engine, rather than over-lubricating to ensure engine safety." At first glance one might imagine that the amount of lubricant used in an engine was a matter only of preventing friction from grinding the engine to a halt. However, the energy used by the piston rings alone amounts to approximately 3 percent of the fuel costs. Given the escalating price of fuel, this could represent the difference between a business running a fleet of vehicles thriving or struggling. "There is a lot at stake in getting the lubrication right," adds. Dwyer-Joyce. 

Lube, emissions and efficiency

In addition to the potential for improving overall engine efficiency by revealing the optimum lubricant levels for specific engines, the same concept would avoid the problem of over-lubricating, which simply leads to lubricant burning as the vehicle is driven and is not only a waste of resources but increases the carbon emissions produced by the vehicle.

The team is currently looking for commercial partners for the ultrasound technology. "Our system could provide major efficiency savings in car engines, but it could also be used on the larger diesel engines in deep water marine vessels, some of which use up to 1 tonne of oil each day," adds Dwyer Joyce.

The study was funded as part of an Engineering and Physical Sciences Research Council (EPSRC) project and included collaboration with project leader Loughborough University as well as researchers at Cranfield University and various manufacturers and suppliers. 

Related Links

J Eng Tribol, 2012, 1350650112464833: "Piezoelectric sensors to monitor lubricant film thickness at piston-cylinder contacts in a fired engine"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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