The Duke Engine

We have been meaning to write an article about the Duke Engine for quite a while and our schedule has prevented us from doing so, which is a pity because this is an important topic for future transportation services – and it is a southern hemisphere invention!

The Duke Engine has been developed out of Auckland in New Zealand and is an axial engine which in the early days was also called a “rotary” engine because the whole unit rotated as opposed to just the crankshaft in a traditional internal combustion engine. Today, rotary engines refer to the Wankel sourced engine design. The axial engine has also been known as a “barrel” engine, thanks to its overall shape. Interestingly, this type of engine appears to be something that the southern hemisphere is good at because after World War 1, an Australian mechanical engineer developed and manufactured similar style engines in Melbourne.

In 1993 the boffins at Duke came up with the first design for their highly efficient engine and by 1996 they had it in the University of Auckland for power testing. This first version was a 996cc motor and was dyno tested before being shoe-horned into a Daihatsu Charade. It probably didn’t need a shoe-horn because both engine and car are tiny!

In the early 2000s a version 2.1 of 933cc was built and dyno tested which resulted in a version 2.2 that was run at ever higher rpm. In 2005, a 3-litre version 3 was created and tested in Auckland and the UK with Mahle Powertrains with ongoing development to improve the efficiency of the motor. Mahle are a great partner because their whole business is focused on improving the internal combustion engine and the ancillary systems that feed them.

The version 3 of the Duke Engine is a five cylinder 3-litre motor using the four stroke Otto Cycle. In a traditional engine the con-rods are connected to a single crankshaft in line – whether the cylinders are in a straight line or V configuration. This method has been changed on some H16 motors where two crankshafts were necessary. With the Duke Engine, like earlier axial engines, the con-rods are connected to a wobble-plate that makes a circular rocking motion that is converted to a power source via a shaft. This means that the five cylinders can be packaged much closer together in the style of a barrel vacuum cleaner.

The concept goes further by being valveless and this does a couple of things. Firstly it reduces the number of moving parts in the motor and the combustion chamber can then be redesigned such that it works better with a wider variety of fuels. With less parts, the engine is much lighter and smaller than a typical four or five cylinder motor and more reliable. The team have tested the engine with many different types of fuels and it works well which means that it could be used in a lot of different applications. In this instance, multi-fuel means petrol, kerosene, bio-ethanol, diesel and even methanol. That is quite an achievement although the diesel version is not ready just yet – there are two methods of combustion: ignition and compression and the team have got the ignition version working to start with. Stage 2 will be the compression version using a diesel style fuel.

One critical area that this engine excels in, is low noise and vibration. A normal engine has to deal with rotating crankshafts, moving con-rods and rotating camshafts as well as moving valves – all these make noise and are very difficult to balance to be in sync with each other. In many engines an extra balancing shaft is required or extra weights are applied to keep the motor smooth. Not so with the Duke Engine, the design takes care of the balance and the reduced components mean less noise and less wear and tear.

With the size and power output from the motor it will be suited to a lot of applications for example, small urban vehicles, motorcycles, pumps, marine use, small aircraft etc, in fact any application that needs power to drive it. Duke will not be the first to utilise an engine in different machines – pump engines have been repurposed for road and race cars and aircraft engines have appeared in cars as well over the last century. What is exciting about this engine, is the fact that it could easily be fitted to light urban hybrid cars as a range extender or simply as a power generator to recharge the batteries.

We like this sort of development because they are the bridging technologies between the old school and the new kids on the block.

Duke Engines