Thermal efficiency
Who: Pivotal Engineering in New Zealand has developed what it claims is a high-power-density two-stroke engine with exceptional levels of thermal efficiency. The company said the pivotal engine design was suitable for hydrogen fuel and would offer a good power-plant for a series hybrid bus.
Technology: The pivotal engine aims to overcome the inherent limitations of conventional two-stroke designs by changing the means by which the piston movement is constrained.
Its designers believe that a cylinder with large port openings does not satisfactorily restrain the piston or the piston rings when all these components are changing in size and shape.
The piston movement in the pivotal engine is instead controlled by pivot bearings, thus eliminating piston rocking and the wear associated with the cold start-up phase in a conventional two-stroke engine. The pivoted piston also ensures that the compression seals are held at a normal orientation to the surface of the chamber and do not protrude into the port openings.
The pivot shaft provides access for water which circulates through the piston to directly cool the piston crown. With the piston temperature maintained at an optimal level by its own water circuit the chamber walls are freed from the task of cooling the piston, allowing temperature to be optimised for combustion.
Because the piston movement is controlled it does not rock or thrust against the chamber walls. In a pivotal engine the only components subject to wear are the chamber surfaces, the compression seals and the bearings.
Paul McLachlan, Pivotal’s designer, said: “By pivoting the piston we have removed the high lubrication demand that is associated with the sliding piston of a conventional two-stroke engine, the cause of excessive oil loss out of the exhaust.
Oil can be metered by the engine management system directly to the surfaces of parts where it is needed.
“Due to this low lubrication requirement, oil usage is only 10% of the level required in a conventional two-stroke engine. This rate of oil consumption is comparable with the oil consumption of a four-stroke engine before the additional saving from not having oil changes is factored in.”
Application: McLachlan said: “The Pivotal engine delivers the potential for a significant advantage in power density and improved thermal efficiency and is adaptable to a wide range of combustible fuels. With absolute control of combustion chamber surface temperature it is a clear choice for hydrogen-rich gaseous fuels and will become the ubiquitous hydrogen engine of the future.”
The engine design has been refined and is at the stage of manufacturing series production engines optimised for specific fuels using direct fuel injection. Pivotal said it was seeking a commercial partner.
| University challenge - a roundup of work coming out of the academic base |
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A €2.3m project will look to improve the stability and security of European electricity supplies
Information engineering and medical imaging group at City University London
Dr Panos Liatsis and Professor Loi Lei Lai
The work aims to help countries in south-east Europe integrate their electricity infrastructure with the wider European power network for greater long-term stability.
The South-East European TSO Challenges (SEETSOC) project will create software tools to enable cross-border trading of power and grid services, meeting peak demand in individual countries. It will also look to help increase the reliability of electricity supply across the whole region and integrate renewable energy sources into the grid through better long-distance transport.
SEETSOC will run for three years. It is being led by City University and will include academic organisations in Bulgaria, Greece, Romania, Italy and Serbia. Software developed to produce models for forecasting electricity demand and congestion will be released under an open source licence at the end of the project.
The development of higher-energy-density batteries for use in plug-in electric vehicles (PHEVs)
School of chemistry at the University of St Andrews
Professor Peter Bruce
The University of St Andrews is working with battery firm Axeon to develop next-generation batteries that will offer higher energy density at a lower cost. Over the next two years St Andrews will research potential new electrode materials. It will work with several industrial partners to implement appropriate chemical engineering to scale up material synthesis and to optimise electrode fabrication resulting in prototype lithium-ion cells based on silicon anode technology. The cells produced will be used by Axeon to construct a usable, PHEV-type battery, with cells engineered into a housing with electrical interconnects and harnessing. Automotive firm Ricardo will perform testing.
Research paper into the best short-term method of reducing emissions from vehicles
Smith school of enterprise and the environment at the University of Oxford
Dr Oliver Inderwildi
More effective ways of reducing vehicle fleet emissions would be better delivered by drastic reductions in size and weight, according to the Future of Mobility Roadmap report into the potential for low-carbon transport. It finds that electric and hydrogen vehicles are likely to remain niche products for many years because of limited battery life and the high cost of platinum, which is needed for catalysts in hydrogen-fuelled cars.
Lead author Dr Inderwildi has urged the government to impose higher taxes on drivers of large, inefficient vehicles and reinvest the money in better public transport and measures to get more people cycling and walking. Rather than rely on the manufacturers to provide the “silver bullet” solution to cut transport emissions, he recommends behavioural change.
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© PE Publishing, 27 January 2010
