Doyle Rotary Engine adds new dimension to split cycle engines at SAE World Congress
I almost passed up the Doyle Rotary Engine at SAE World Congress 2012. Fact is, I had just finished speaking with Pinnacle Engine and was heading fast toward the FEV display. Then I looked to my right, paused, then went on. After the FEV visit, I was simply drawn back to the Doyle display.
When I looked again, I noticed, much to my surprise, that the Doyle Rotary Engine is also based on splitting the cycle. For sure, that makes it different than Scuderi Engine and Tour Engine. Recall the Scuderi holds the traditional single crankshaft design; Tour engine has an opposed piston arrangement with a single head and dual crankshafts. So it seems Lonny Doyle has introduced us to another variation of the split cycle.
For those who are new to the term, split-cycle, though, be apprised that is a modified version of the Otto Cycle or 4-cycle engine; intake, compression, power and exhaust. In the case of split cycle, the cold elements, intake-compression have dedicated pistons. Likewise, the hotter power and exhaust elements of the cycle have their own dedicated pistons. Result is an increase in efficiency greater than what we have on the road now even with all the latest downsizing, turbos, direct injection and variable cam and valve timing.
One area shared by most split-cycle engine developers is this: The engines fire AFTER top dead center. So, it is the one correction of the conventional engine that bears repeating. The traditional Otto Cycle engine must fire before top dead center, which makes the engine essentially work against itself for a short duration and increases combustion temperatures dramatically.
Moreover, the Doyle Rotary, like Scuderi and Tour, completes the four strokes in one revolution of the engine, whereas the traditional engines require two. That’s another benefit of splitting the cycle. Nonetheless, unique to the Doyle design is thus the rotary configuration as a split cycle. So, as you can surmise, the message here is that the split cycle avails many arrangements and now appears unlimited.
According to Lonny Doyle, whom I met for the first time at SAE, the first prototype first fired in 2010. Success was short lived, though, due to seals gaulding against the aluminum. The next prototype solved the issue by remanufacturing the parts so the seals would glide across the seal surfaces that were plated and hardened to the same specifications that Mazda used.
I admit, this rotary arrangement takes a bit of getting used to. For example, the crankshaft is stationary. This makes many wonder how the torque is being created. Also, some want to point back to the early failures of the Wankel. However, Doyle points them back toward a Wikipedia note that says, "In 2010 Audi revealed that in their electric car... they would have a small 250 cc Wankel engine. FEV Inc. revealed that, in their electric version of the Fiat 500, a Wankel engine would be used."