A composite piston accumulator designed by engineering firm Parker is set to form a vital part of Bloodhound SSC’s attempt to break the world land speed record in 2016.
Powered by a jet engine and rocket, the Bloodhound SSC (supersonic car) will begin high-speed testing at Hakskeen Pan in South Africa later this year with a target of reaching 800mph. Parker’s energy storage system will provide fast access to a big energy boost if this is needed, for instance, during rapid braking after the record attempt is complete.
Although the vehicle will rely on powerful air brakes to slow the vehicle from 800mph and below, if a loss of hydraulic power occurs, Parker’s two composite piston accumulators will be ready to release energy stored within them and deploy the air brakes at a controlled speed.
Compared to the steel bladder accumulators that might normally be used on such a vehicle, the composite accumulators are more compact and are 60 percent lighter, while being stronger and less susceptible to fatigue.
Traditionally, composite accumulators have used metal liners with an outer composite reinforcing structure, owing to the high-stresses involved. However, Parker’s engineers have been working for over 10 years to develop a high-performance hydraulic product that is almost entirely made of composites.
Their piston accumulator therefore uses a novel plastic liner, integrated into the carbon fibre reinforced epoxy composite product. The barrel design consists of two parts – an inner liner and outer barrel. The fully composite inner liner carries the hoop loads of the internal pressure, while a fully composite outer barrel is responsible for supporting the axial loads, allowing it to perform under high stress.
The development phase has included fatigue testing up to approaching six million cycles, while the accumulator also features a safe failure mode where it can leak in the event of over-pressurisation. Although more expensive than a steel bladder accumulator, the technology has applications elsewhere.
‘We think there will be a big interest in the technology from the offshore market, where corrosion is a big issue in the environment,’ said Mark Cattermole, product manager for industrial systems at Parker UK. ‘It’s a fantastic product for Bloodhound. It has to be positioned relatively high on the vehicle, so the low weight means it has less effect on the car’s centre of gravity – the car must be very stable at such high speeds.’
Following trials at Hakskeen Pan, the Bloodhound team will return to Britain to review test data before returning to South Africa in 2016 with the aim of reaching 1,000mph.