Jet power is synonymous with the modern age of transatlantic air travel, but has limited use in more modest industries. However, Jaguar is now backing jet technology to give a hefty boost to the future of the car industry. E&T finds out how.
Jet power technology is more than 70 years old, yet it still has about it a certain sense of mystery. There's a futuristic air of aspiration to the technology that has shrunk the world through its use in civil aviation.
But look beyond the aeroplanes and the occasional foray into orbit, and what use do you see for jet technology? Land speed record attempts? The Batmobile? Jet power is all about thrust and speed – hardly something that's going to help you negotiate Spaghetti Junction or the Hanger Lane Gyratory System.
Its not as if the idea of domestic jet power has not been given serious thought in the past. Other than thrust, the other great advantage of jet power is the potentially high power-to-weight technology. UK automobile manufacturer Rover sought to capitalise on the technological advances wrought by the Second World War in its experiments with jet powered cars.
However, the company's efforts sputtered and stalled in the mid-1960s. Its JET1 car was criticised for its heavy fuel consumption and poor throttle control. For this type of propulsion to have a future, these issues would have to be tackled.
Jaguar leaps ahead
This is precisely what UK company Bladon Jets has tried to do with Jaguar's eyebrow-raising (and singeing) turbine electric hybrid, which might just provide a glimpse of automotive's future.
The introduction of Jaguar's latest concept vehicle, the C-X75, marks a turning point for gas turbine cars, as evidenced by its debut at the Paris Motor Show last year, where it was awarded the coveted 'Best In Show' prize.
The styling of the vehicle adds real muscle to match the potential under the hood. Although billed as 'jet-powered', this label could be hotly debated; the powerful precision-engineered micro turbine engines do not directly power the transmission, but instead power lithium batteries in a similar fashion to other hybrids like the Toyota Prius.
Pure electric vehicles need to charge their batteries before putting the key into the ignition, but a REEV (range-extending electric vehicle) generates its own power. Jaguar's baby, then, is only a jet in the same sense that the Prius is an electric vehicle – partial but not pure electric propulsion.
The C-X75's twin turbines, designed and engineered by Bladon, are housed in the rear of the car. Most hybrids run on rotational energy generated via electric motors or a small internal combustion engine. REEVs like the Prius run on electric power with the combustion transferring energy to a generator to keep the lithium cells ticking over.
This has an advantage by alleviating the 'range anxiety' associated with pure electric vehicles which need to charge their batteries, often for a full eight hours or more, making them unsuitable for longer journeys.
A REEV generates its own power, doesn't need to be charged up for lengthy periods, and only needs to carry enough lithium cells to allow it to travel about the average journey, rather than pure electrics which require more cells to carry out longer trips. In theory, the weight of the car can be reduced significantly – and it also keeps the cost of production down as lithium batteries can be very expensive to manufacture.
Jaguar claims that as the C-X75's range-extending engine is only topping up the battery, it can always run at its most efficient speed and it doesn't have to generate a variable load that is higher under acceleration and lower while cruising, like an ordinary combustion-engine driven car.
Since putting the prototype on display, Jaguar is reportedly embarking on a feasibility study to produce 1,000-2,000 cars per year – but even so, it would be at least five years before you could see one in a showroom.
The C-X75's four 145kW, 400Nm-torque hub-mounted electric motors can generate roughly the equivalent of 780hp, propelling the car at speeds approaching 204mph and capable of 0-62mph in 3.4 seconds. When fully charged, its lithium cells will keep it going for 100 miles, but the twin gas turbine engines extend this range to 560 miles.
Working as part of a Technology Strategy Board-funded consortium with Jaguar Land Rover (now part of Tata Motors) and Harrogate-based electrical equipment manufacturer SR Drives, Bladon has developed an axial-flow turbine weighing a little under 35kg, with a compressor only 75mm across.
'The industry said micro-jets couldn't be done. Paul and Chris Bladon came at the problem as precision enginerrs and proved them wrong,' says Courtney Heading, business development director of Bladon Jets.
Previously, shrinking the size of the turbine was not possible because the blisk of the turbine had to be assembled in several parts and these blades then had to be bonded to the central hub.
Bladon therefore developed a process to machine blisks from a single piece from virtually any metal, such as ultra-light and ultra-strong aerospace alloys of aluminium and titanium. The blades can be fully customisable and therefore could be used in other motor driven apparatus.
'Paul and Chris believed that they could make a micro-jet engine,' says Heading, 'experts said it was impossible because you couldn't make a blisk small enough for the rotation speed you need. It has to be very balanced and that wasn't possible with multi-part blisks.'
Spark erosion technique
The Bladon twins discovered a way to cut the metal extremely accurately in a repeating method based on 'spark erosion' which the company developed in-house.
For the C-X75, Bladon used the turbine, spinning at a constant 80,000 rpm, with a switched-reluctance generator, which is capable of producing 70kW of power. The integration of the two turbine-generator combinations with the vehicle drew on Jaguar Land Rover's previous experience with the JET1. The result is that the engines are very quiet as the turbine's exhaust – the source of jet noise – is muffled and by the extra airflow.
'Ratan Tata really gets the technology behind the Bladon micro-jet,' says Heading. Tata, Jaguar Land Rover's parent company, has become an investor in Bladon principally because of its interest in micropower generation.
'Turbines are can use various different types of fuel – not just kerosene, so if you're in a remote location, you might not have access to jet fuel. But bio-fuels may be more abundant,' says Heading who adds, 'Turbines will work with a number of different types of fuels because they have only one moving part. Therefore it won't seize up like conventional piston engine.'
'Turbines are easy to maintain, lightweight, and they allow you to reduce the amount of batteries that you charge on the go. Everything else in electricity generation uses turbine technology so why not cars?'
Other microjet technologies
Bladon Jets is not the only company looking at jet power. ETV Motors, a private company based just outside Tel Aviv in Israel recently raised over $12m in investments and says it has also found a way to make microjets in range extending electrical vehicles commercially viable.
Like the Bladon Jet, it claims to have developed a micro-turbine engine to act as an on-board charger and a high-density battery that can power a vehicle for about 60-80 km (35-50 miles) on one charge.
Their test car uses newly designed components still undergoing development, the company said, adding that the final product should be ready for tests next year. The company is working closely with Toyota and has built a prototype car using the shell of a normal Toyota Prius, swapping the internal combustion engine for microjet technology. Just like in the Jaguar prototype, the engine is placed at the back of the vehicle and drives almost silently around a test track.
With automakers racing to develop the most efficient, environmentally friendly cars with minimal emissions, the concept of turbine-powered electric vehicles is being given serious credence by auto-engineers.
But in order for it to be more successful, it has to convince manufacturers and consumers that the problems that dogged jet power in production cars of the 1950s and the 1960s have been overcome.
Additionally, these companies are also looking at a myriad of alternative technologies. Only a handful of these will eventually be taken up – and the jet age has to shake off its image of a 20th century technology to compete with other hybrids and pure electrics in the current century.