Designing and manufacturing a rotary power plant for a new generation of military appliances might seem like an intimidating task even for a large group of engineers, but that is exactly what a small design team at Sutton Coldfield-based engine maker Cubewano has done.
Indeed, the single-rotor Wankel engine that the British engineering firm has now developed not only delivers over 1hp for every pound it weighs, but it also has the unique ability to start and run on both kerosene-based JP8/Jet-A1 and petrol at temperatures as low as -32°C.
Craig Fletcher, founder and CEO of Cubewano, said: “Another supplier was originally building the engine for the US Army’s Class 1 increment 2 project, but the turbine suffered catastrophic failure so we were brought in to design, test and deliver a brand new engine with very aggressive weight targets – all in less than two years.
“Our brief was to develop an engine with a core weight of less than 1lb per horsepower, which was previously thought impossible. Through extreme optimisation of components and carefully selecting the latest high tech materials, we were able to achieve this ambitious goal.”
The demanding technical specification of the engine meant that it was not only necessary to design bespoke subsystems to ensure that it would start quickly and run efficiently, but also to build the engine from materials that could withstand high temperature operation as well as offer the wear resistance that was required.
Like other larger rotating Wankel engines, the Cubewano design also employs a triangular rotor that incorporates a central ring gear driven around a fixed pinion within an oval-like housing, while apex seals at the corners of the rotor seal against the periphery of the housing, dividing it into separate moving combustion chambers.
But that’s where the similarities end. To ensure that the engine would start quickly from kerosene fuel, the engine designers had to develop a proprietary throttle mechanism that could preheat the kerosene air mixture from a 150W electrical source before it was injected into the combustion chamber. The design enabled the engine to start burning fuel within a few seconds.
Not only that, but they also developed an electronic control system to control the ignition sequence of the two spark plugs used in the engine to ignite the air fuel mixture. As a result, both spark plugs can be fired independently as a function of engine speed and load, resulting in a controlled burn that does not pre-ignite the kerosene fuel and cause knocking.
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Aside from the mechanical and electronic design issues that needed to be overcome, the serendipitous use of materials was fundamental to the development of the new engine.
Due to the high temperatures and stresses found within the mechanism of the engine, the company was faced with no alternative but to design and commission its own custom components, including all the gears, bearings, shafts and rotor.
The choice of material for the apex seals on the rotor was an equally important manufacturing decision.
The Cubewano team manufactured their engine seals from a hard-wearing low density ceramic material and coated the internal metal housing of the engine with a nickel ceramic coating against which the seals would come into contact as the rotor moved. The result also led to reduced heat loss and an increase in combustion efficiency.
The firm’s patented technology has potential to be used in a variety of military as well as non-military applications. The Cubewano team has created a range of products under the name Hornet Generators, which are lightweight and man-portable.
“An obvious application was a lightweight portable generator for troops in theatre. A platoon currently carries up to 11 battery types weighing up to 436lb for a 72 hour mission, as current generators running on heavy fuel are too heavy for one person to carry.
“Developing a power generation solution around our small and efficient heavy fuel rotary engines for the military market was a logical step.”
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Cubewano’s achievements have been recognised both regionally and nationally. In 2010 the company was awarded The Birmingham Post’s Business Award for Science & Technology. Co-founder of Cubewano, Shaun Addy, was lauded by his industry peers – being titled Design Engineer of the Year at the British Engineering Excellence Awards.
Mr Addy met the judges’ criteria for being able to produce innovative designs as well as contributing to the industry more widely. The panel noted that in his 26 years in the profession working for the likes of Lotus and BMW he had gained numerous patents for his innovative design work on some of the world’s most respected internal combustion engines.
Perhaps unsurprisingly, most of the firm’s customers are located outside the 海角视频. Mr Fletcher recently returned from the Singapore Airshow with a number of potentially lucrative partnership agreements under negotiation. They also have customers including European and USA-based manufacturing companies.
Cubewano’s efforts have not escaped the attention of Sutton Coldfield MP Andrew Mitchell, who said: “I am very proud to have Cubewano on my patch. This is British inventing at its best and I have written to the Minister for Defence Equipment, Support and Technology to introduce Cubewano, highlight its huge potential and encourage him to visit himself.”
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