YAN Engines is a small technology company with offices both in Austin, Texas, and Brighton, UK. The company is focused on the development of its own proprietary high-efficiency engine concept that aims to provide significantly enhanced flexibility over the conventional four-stroke internal combustion engine architecture.
The differential stroke cycle piston (D-Cycle) concept relies on a split piston that completes the four engine strokes in a single crankshaft revolution, thus providing the opportunity to reduce the cyclic energy losses and improve combustion process efficiency. This is achieved via the use of a vertically split piston, with a lightweight crown and ring lands which can be moved independently of the main piston body to accomplish the lower stress functions of the induction and exhaust strokes. During more mechanically demanding compression and combustion strokes, the two parts of the piston are recombined, and power transmitted solely via the crankshaft. The D-Cycle concept thus achieves all four strokes of the piston within a single rotation of the crankshaft. More than this, it provides a much greater flexibility in improving efficiency, for example by reducing intake stroke volume to match the desired drive cycle demand with a long Atkinson expansion-to-compression ratio.
A veteran of engineering and management consulting, YAN Engines CEO Lu Yan approached the Ricardo Advanced Technology Development team for support with the simulation and refinement of this highly innovative engine concept. “Ricardo has a strong reputation for its expertise in engine design and high quality delivery of work. It also has its own software tools – particularly WAVE and IGNITE. We identified that having a deep level of knowledge of these would benefit our project since we wanted to challenge some of the basic principles of conventional engine combustion models.”
But while engineering expertise and access to and understanding of the physics of its own proprietary CAE tools was a crucial consideration, location was also important: “We had recently opened an office in Brighton, so it was only natural that we wanted to start a working relationship with our esteemed neighbours in Shoreham!”
YAN Engines tasked Ricardo with providing simulation-based design support in the development of a prototype version of a Ford EcoBoost 1.0-litre gasoline engine incorporating the D-Cycle piston technology. A basic model of the engine had already been created by YAN Engines using Ricardo’s WAVE software, but the project required the development of new simulation methods for the optimization of the piston motion at defined engine operating points. This included an approach to compare the simulation results of the baseline engine and the D-Cycle engine, as well as specifically-adapted simulation models for improved fuel consumption prediction. Using this bespoke toolset, sensitivity studies could be carried out on various base engine parameters to maximize the fuel-efficiency benefits of the D-Cycle concept.
“We learned a lot from the design study,” explains Yan. “It challenged a lot of our assumptions and delivered a lot of valuable information for our prototype build. Most importantly, it validated the fuel efficiency benefit that can be accomplished on a retrofit basis to a production OEM engine.”
In addition to providing a clear technical direction for the next stage of prototype development, the project was useful to YAN Engines in its communications with existing and potential backers. “Once we complete and re-work the model based on dynamometer data, we will be able to show the correlation of the WAVE model with actual results,” says Yan. “Therefore, we believe that confidence in the performance and efficiency of future engines can be gained by investors on the basis of simulation tools. The knowledge of the Ricardo team in terms of the development process has been valuable to us to better scope future budgets, schedules, and teams, both for internal planning and investor meetings.”
While the initial demonstration of the D-Cycle concept has been based on the retrofit of the technology onto an OEM production engine to deliver increased fuel efficiency, Yan is far more ambitious when it comes to the idea’s longer-term potential: “Our D-Cycle piston technology can deliver a choice of different benefits: more torque or more efficiency by way of a new piston profile that can be changed within a given engine architecture. No longer will engines be designed around full displacement of the stroke, while sacrificing fuel efficiency for the drive cycle. Tomorrow, we will implement an engine with optimized piston profiles based on whatever is the intended use for the vehicle. Ricardo’s WAVE software and the capability to optimize the piston profile will be a key resource in this future.”
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Development of the YAN Engines high-efficiency D-Cycle engine concept
13 December 2016

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