There can be few people working in propulsion who do not know something about Wankel rotary engines, from their much-heralded – and largely disappointing – entry into the automotive market in the 1950s to their niche applications in aviation, motorcycles and motor sport.
Precision engineers AIE UK believe it’s a technology that’s going places; alongside the company’s main business designing and manufacturing engines for unmanned aerial vehicles (UAVs), AIE is making inroads into marine and hybrid automotive markets – and has found interest in electrical generation applications.
AIE managing director Nathan Bailey puts the success down to the performance of his company’s SPARCS- enabled engines. SPARCS – for Self-Pressurised-Air Rotor Cooling – is “rewriting the rules in rotary engine design”. The Lichfield-based SME has the products and patents to prove it and NATEP to thank, in part, for its support of SPARCS development in a project that ran from 2015-2017.
AIE traces its heritage to pioneering work by Norton Motorcycles in the 1980s on new cooling technologies that made the engine simpler but increased its power density. It was also thanks to Norton that the rotary engine’s suitability for UAVs was discovered.
After AIE was formed in 2012, the company teamed up with David Garside, the inventor and engineer who developed the air-cooling technology for the Norton Classic road bike. Garside had an idea for a new iteration for the air-cooling technology which became SPARCS.
Engine built from scratch
NATEP helped AIE build an engine from scratch to test the system. It was a success – “one of those great moments,” recalled Bailey. SPARCS worked well at 40cc, now the smallest model in AIE’s range producing 6HP on average and weighing just 2kg.
SPARCS technology harnesses combustion blow-by gas as the cooling medium. “It sounds strange but it’s not that warm,” said Bailey. This blow-by gas circulates to the heat exchanger in a self-balancing, sealed system. Its density increases with the engine power. “The gas becomes very dense – so it’s the ideal medium for transferring heat from the engine.”
Since its NATEP project concluded, AIE has chalked up considerable success with SPARCS. Along with moving forward in the UAV market, the company has taken it’s technology into marine and automotive hybrid programmes.
Connecting the engine to a generator to provide electric power is “one of shifts generally in the market”, said Bailey. “We developed an engine for direct drive and found there was interest in using it in hybrid systems.”
SPARCS is unique to AIE, and the company’s standard range of four engines, from 40cc to 650cc, all incorporate the patented technology.
‘Door-openers’ to projects
The standard models act “almost as door-openers” to projects requiring a bespoke approach. Said Bailey: “Most of our major programmes are around designing specific custom solutions for customer applications based on our standard cores.”
Size presented a challenge. A 40cc engine is very small which complicates the design and manufacture of some components. It took time, he said, to find the right manufacturing techniques to achieve the high precision levels necessary, especially for the rotor and shaft.
More recently AIE has been looking into additive manufacturing (AM) as a possible way to take even more weight out of engine but add air-cooling for external surfaces.
Although AIE has doubled its staff to 26 in the last two years, the company doesn’t anticipate growing beyond SME size. “As a company specialising in the fields we’re in, our business model doesn’t take us to scale,” Bailey said.
“NATEP gave us the opportunity to work with other technology companies. The progamme saw us all the way through to a functioning engine. We’re grateful for that.”