No wonder America and the world has an energy crisis. Standard gasoline engines utilize less than 30% of the fuel's potential energy, while over 70% of its energy is lost in the form of heat through the radiator and the exhaust. This is a huge energy waste by any stretch, and is directly associated with high CO2 and NOx noxious emissions.
Yet, while government mandates have engineers in the auto industry chasing their tails for a more-efficient, electrical solution, a few companies are rethinking the entire combustion engine process. One such company is Tour Engine.
Attending local events leads to new connections; and this year’s SAE Show in Detroit was no exception. In addition to the Scuderi split-cycle engine (which I already covered), the split cycle TourEngine™ was also in attendance.
Unfortunately, I missed an interview with the Tour people at SAE. However, I was fortunate to have Dr. Oded Tour write me directly with an offer for a phone interview. Of course, I jumped at the opportunity.
Split Cycle Engine Technology: Wave of the Future
Lest you think the internal combustion engine is dead and that it will be replaced soon by electric drives, think again. Just take one look at the cost of a full EV like the Nissan Leaf with its anxiety-filled, 100-mile range. Even the Volt, which is an electric-drive car with an ICE generator that extends that range to 300 miles, is priced at $41,000 before subsidies.
Point is, even after subsidies, the cost is still too high for most people. After all, companies are not paying salaries as they once did, except for executives, of course. That means the working-class will be driving cars with gasoline engines for many years, perhaps another decade or two.
In my opinion, the split-cycle engine technology is the next wave of ICE (internal combustion engine). It literally split’s the 4-cycle process of intake, compression, power and exhaust, also called the Otto cycle, into two distinct, more efficient segments: 1) the colder or intake/compression side; 2) the hotter or power/exhaust side.
The advantages are many, because splitting the cycle raises the efficiency level tremendously, which has always been the downfall of gasoline engines, especially when fuel prices are high. Again, all standard 4-cycle engines waste energy in two forms: heat through the radiator and through the exhaust.
TourEngine™ , on the other hand, is a patented, opposed-cylinder split-cycle combustion engine with the potential for substantial efficiency gain as a result of its superior thermal management. It also offers significant reduction in noxious emissions.
Hybrid and electric engine technologies offer improved efficiency, but are expensive and complex. The TourEngine™ is simpler, because it is based solely on current cylinder/piston technology. That is significant as we attempt to morph the auto industry over time.
The TourEngine™, like most split-cycle engine concepts, splits the conventional 4-stroke cycle into two segments: a Cold-Cylinder that hosts the intake and compression strokes, and a Hot-Cylinder that hosts the combustion and exhaust strokes. Splitting the cycle allows flexibility in the design and thermal management, consequently leading to improved energy utilization.
Unique to the Tour technology concept, though, is the placement of the cylinders and the crankshafts. The Tour design uses two opposing cylinders. Instead of being connected via a common crankshaft, the TourEngine™ has two crankshafts at opposite ends, while the two cylinders, one hot, one cold, directly share the same head. This is a fundamental deviation from previously proposed split-cycle designs. According to Dr. Oded Tour, this is key to minimizing the potential losses from splitting the cycle.
Overall, TourEngine™ presents a cost-effective alternative with a substantial increase in engine efficiency and an opportunity to revolutionize the way combustion engines are built. According to their website, this corrects the two major losses of the 4-cycle engine which are:
Exhaust Loss (27%) – The single cylinder size is a compromise between optimal expansion and compression sizes. As a result, the cylinder size is too small to allow complete expansion of the combusted charge, and therefore the exhausted gas contains unutilized heat energy.
Cooling Loss (37%) – A cooler environment is required for an efficient Intake and Compression. To provide these conditions the radiator continuously “steals” heat to cool the cylinder. However, overcooling during the combustion stroke is highly inefficient.
Examiner Final Comments
I have no intention on taking sides here with split-cycle technology. I think the industry will be better off with competition from companies like Scuderi, Zajac Motors, Speka Design and Thring Design. Since my familiarity has been centered on only two so far, I’ll keep my comments limited. For sure, the TourEngine™ is interesting due to its opposed cylinder layout. It is still similar to the Scuderi in that the cycle is indeed split. However, that’s where the similarities end.
For the record, the Scuderi looks like a standard engine, where a left bank of cylinders acts as a compressor for the right bank. It shares a common crankshaft. Therefore, it needs an air tube to connect the heads. While this may inhibit some thermal efficiency, this also enables a storage volume or tank which can store air while coasting. Now, whether that is enough to overcome any so-called inefficiencies, I am not certain. I’ll let Scuderi make their points on their own.
The TourEngine™ with its opposed cylinder design is unique in its configuation or layout. And that is the basis behind its claim of maximum thermal efficiency. Whether that efficiency gain is sufficient to overcome the cost of two separate crankshafts might remain to be seen. Again, I make no judgment, just an observation. I’ll let Dr. Tour make his points as we go forward.
For sure, this will not be the last time I will address split-cycle engine technology. My hope is that the public and OEMs will become aware of the passion and the ingenuity behind this technological revolution, even if we opt for natural gas. For more information on the TourEngine™, visit http://www.tourengine.com
Comments
Fascinating stuff, Frank. Truly. It only makes sense to raise the bar significantly on efficiency.
Current PM cites "5 Ways to Redesign the Internal Combustion Engine". Stirling, OPOC, Scuderi, Free-Piston, and Wankel.
If one or more of these technologies, or others, could be shown to significantly raise the bar in terms of increased fuel efficiency or decreased emissions, they might well have a future in production automobiles.
I just hope that chasing these unicorns, even if a production ready version is "just around the corner", that it doesn't turn into another distraction like the false promise of hydrogen fuel cell vehicles.
If a car maker starts delivering 100 MPG vehicles to challenge EREVs and PHEVs, using Scuderi, TourEngine, or some other technology, they have a real shot at extending the ICE age.
CNG, and new nuclear plants, should be used to retire our dirtiest coal plants.
www.popularmechanics.com/cars/news/industry/5-alternative-engine-architectures
Correction of a common misunderstanding: The TourEngine design would be better described as having two halves of a crankshaft and not two crankshafts. The basic pair of the TourEngine cylinders is comparable to two conventional cylinders as the TourEngine power cylinder fires at double the rate - once every revolution. Therefore, for example, a standard V8 is comparable to 4 TourEngine pairs. Regarding the crankshafts, it can be viewed as if the common V8 crankshaft was divided into two halves, one part actuating the 4 cold pistons and the other part actuating the 4 hot pistons. The TourEngine has the advantage in that only the power crankshaft needs to be massive to withstand combustion forces, while the compression crankshaft undergoes substantial reduced stress and therefore could be lighter.
Thanks Frank, interesting
Historically split-cycle technology couldn't raise efficiency beyond common IC’s levels.
Due to its opposed piston configuration that avoids connecting tubes, the TourEngine is the first split-cycle that closely follows the Otto cycle course of thermodynamic events.
It’s my hope and believes that sooner than later we are going to witness a refreshing breakthrough in combustion engine efficiency performances.
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