Hamburg/Cottbus- Once written off by car industry experts, the rotary engine invented by German engineer Felix Wankel 50 years ago is on its way to becoming one of the greenest power units on the planet. Engineers in Japan and Germany are currently perfecting the engine to run on liquid hydrogen fuel, or as a hybrid in tandem with an electric motor, and they are excited about its prospects.
The Wankel is unique since it generates power using a triangular rotor inside an elongated housing instead of pistons moving up and down in cylinders as in a conventional internal combustion engine.
The design was much heralded in the 1960s and '70s when companies including Rolls-Royce, Daimler-Benz and Citroen of France queued up to buy a licence to build the Wankel engine, pioneered in the stylish Ro 80 limousine from carmaker NSU, now a part of Audi in the VW concern.
The 1973 oil crisis, however, sounded the death knell for the Wankel since it drew attention to the engine's high petrol consumption, one of the invention's major drawbacks. Interest waned and only Mazda of Japan remained loyal to the concept.
Since then a lot has changed and with fossil fuels running out fast, experts agree that hydrogen is the only source of energy which could replace them in the long run. Enter the Wankel engine, which is ideally suited to burning this type of fuel.
The Mazda RX-8 is currently the only production car in the world to be fitted as standard with Wankel propulsion and the Japanese maker has just sold 30 examples of a hydrogen-combustion version to the Norwegian government. Starting next year they will run on a highway designated as a "hydrogen corridor" with special filling stations and other facilities.
The effort is worthwhile since hydrogen is also one of the cleanest fuels. Vehicles which burn it emit nothing but water vapour into the atmosphere. It therefore has a key role to play amid increasing global efforts to cut climate-damaging carbon dioxide emissions.
At the recent Tokyo Motor Show, Mazda also showed a Wankel hybrid version of its M5 van, the Premacy Hydrogen RE Hybrid. This dual mode model can switch over from running petrol or hydrogen at the press of button and has an auxiliary electric motor too. From 2008 the van will be built in small numbers and leased to customers.
Mazda's technical director Seita Kanei told Germany's Stern magazine that the Wankel engine is ideal for dual mode cars which run on either petrol or hydrogen since its larger combustion chamber has more space for separate petrol and hydrogen injectors. Previous Wankel bugbears such as faulty engine seals and thermal distortion have also been largely overcome.
Kanei's confidence is shared by Jochen Muenziger, head of vehicle engineering technology at Mazda Germany. He stresses that the rotary engine allows for a safer burning of hydrogen fuel with none of the backfiring which is typical of a hydrogen-powered piston motor.
"We think the Wankel motor has great potential and we have never given up on it. For the last 40 years it has been an integral part of our marque history," said Muenziger. It is worth noting that Mazda has sold 150,000 of the latest generation MX-8 petrol-driven rotary cars since it came out in 2003. In Germany a total of 1,326 were sold in 2006. Muenziger drives one himself.
Meanwhile, in the eastern German city of Cottbus, the Wankel Supertec company is working on a common rail diesel version of the Wankel motor and a range of stationary engines for industrial applications. These will run on either diesel, biofuel or kerosene and are set to go into production in 2009.
The compact engine is ideally suited for petrol-electric hybrid cars where weight is at a premium and according to Dr Rudolf Klotz of Wankel Supertec, "When it comes to running on hydrogen the Wankel engine is also the best solution around."
Klotz pointed out too that the Wankel motor has also fewer moving parts and runs much more smoothly than a standard piston engine. He said Supertec had also overcome petrol consumption problems by using using a sophisticated fuel injection system.
When he fired up the first rotary engine on a testbed in southern Germany 50 years ago, inventor Felix Wankel would never have believed that his new-fangled power unit would eventually use such a high-tech fuel as hydrogen, also used to power space rockets.
A tireless pioneer, Wankel was still working on the engine concept until a few years before his death of cancer in 1988 at the age of 86.
Until the end he believed in the success of his engine and since he had never obtained a driving licence of his own, was chauffeur- driven to work every morning in a Wankel-powered NSU Ro 80. That model was arguably the most famous Wankel car of all time. It was produced for only 10 years from 1967 to 1977 is and now a collector's item.
