Happy medium between 2 and 4 stroke?

[Will'smotobikes19]

Right, the achates but i mean instead of pistons pushing together it could work on both sides as in the axial configuration. Picture valves and sparkplugs on both cylinder heads/endplates and 2 rotary cams with 2 lobes. The Pto would exit one of the heads with a ball bearing and a seal. In this case it would be a 10 cylinder.

4:50 shows what i mean

 

[87Octane]

Working engines do exist:

Projects - YAN Engines

YAN Engines has developed a D-Cycle modification of a mass-produced passenger car engine and for the US Department Of Defense.

yanengines.com

From the link:

"YAN Engines recently completed a D-Cycle™ modification of the Ford Ecoboost 1.0L engine. The Ecoboost is one of the most fuel-efficient production engines in the world, awarded the International Engine of the Year “Best Engine Under 1.0L” award for six consecutive years.


When modified with D-Cycle™ pistons, the Ecoboost achieved 20% more fuel efficiency and exceeded the stock torque and power output."

That is pretty amazing when we consider in the picture below the compression stroke now only uses half of the original stroke. (Think about how that would affect compression ratio in the absence of other changes to compensate.)

P.S. Here is a stock Ford 1.0L ecoboost piston with description about the importance of the piston top shape:

Look what just arrived today! (1.0L Ecoboost Piston)

www.fiestafaction.com

1.0L Ecoboost Piston:

Bore:	71.9mm / 2.83 inches
Compression Ratio:	10:1
Piston Speed:	3500fpm@6500rpm
Material:	High-Temperature Aluminum alloy combined with 2 steel cast-in upper ring supports.

• Piston top shape designed for efficient combustion with direct injector and controlled flame propagation across the cylinder.
• Low friction coatings are used on the piston skirt to reduce wear and friction on the cylinder walls.
• Piston cooling "oil squirter" jets spray oil on the underside of the piston to keep it cool.
• “Direct-Injection Bowl" Piston top shape is designed for efficient combustion with direct injector and controlled flame propagation across the cylinder.

 

[Will'smotobikes19]

As far as I know there has never been an axial engine motorized bike or motorcycle. Is it possible? probably. Ever since I saw attempting the world's fastest 49cc I thought what about a 25cc that goes atleast 40mph on a bike with multiple gears would be great probably use less fuel, but the rpm might kill it.

 

[87Octane]

This Rotary Engine is cool 4 lbs and 5 HP
It looks like it will fit nicely in a bicycle frame

Game-changing rotary engine muscles a go-kart

Imagine an engine that's 30 percent smaller than a traditional piston design of like output, and that runs smoothly, with less noise and vibration. Plus, it burns several types of fuel. That's the LiquidPiston X rotary engine, which was recently demonstrated powering a go-kart.

newatlas.com

Here is a video that was on the science channel showing how it is made:

How We Make Our Rotary Engine | LiquidPiston

Take an in-depth look at how LiquidPiston’s rotary engines are made from a single block of aluminum.

www.liquidpiston.com

 

[87Octane]

2 stroke opposed piston axial diesel engine:

The Engine | covaxe

covaxe® combines the axial and opposed piston engine architectures and applies new patented concepts to them to produce an exceptionally efficient, well-balanced lightweight engine with inherently low emissions for a wide range of applications.

With the covaxe® engine, the cams are profiled so as to maintain a constant combustion volume until fuel injection and combustion are complete, so that full combustion pressure and temperature are available to drive the pistons along the cylinders, thus maximising thermal efficiency. The covaxe cycle combines the thermal efficiency advantages of a spark-ignition (gasoline) cycle and a compression-ignition (diesel) cycle.The combustion regime thereby reduces CO2 emissions and is tailored to reduce significantly particulate emissions.

https://www.covaxe.com/encouraging-results-from-our-collaboration-with-southampton-university/news/

As we move towards the first testing of our Demonstrator Engine, the results of our collaborative study with Southampton University have just been published. The paper, entitled ‘A Numerical Study of a Compression Ignition Engine Operating with Constant Volume Combustion Phase: Effects of Constant Volume Phase on Combustion Performance and Emissions’, gives confidence that we are well on our way to achieving our objectives.

The study was carried out by PhD student Callum Ramsey under the supervision of Dr Kahanda Koralage Dinesh. It used computer fluid dynamics (CFD) modelling of the engine and examined the effects of varying the constant-volume duration, the fuel injection start time, and the effects of exhaust gas re-circulation.(EGR).

It showed that significant reductions in nitrogen oxides as well as virtual elimination of soot emissions could be achieved whilst still attaining the considerable improvement in specific fuel consumption offered by constant volume combustion.

Testing of the demonstrator engine is scheduled to start later in the summer with evaluation of the sliding and rotating bearing losses. This will be followed in the autumn with load tests on a dynamometer test cell in the premises of our sister company Covaxe GmbH in Aachen, Germany.

Further studies at Southampton of a more detailed multi-cylinder model of the engine is planned for 2021 and direct validation will follow from the testing.

 

[87Octane]

Some information on controlling oil consumption in 2 stroke opposed piston engines from Achates:

https://www.sae.org/publications/technical-papers/content/2019-01-0068/ (January 2019)

https://achatespower.com/wp-content/uploads/2021/02/Durability-Assessment-of-OP-Engines-Feb.2021.pdf (February 2021)

Results:

The fuel specific oil consumption (FSOC) for the single-cylinder experiment is shown in Figure 3. In general, the FSOC is below 0.05% for most speeds and loads with a cycle-weighted average of 0.04%. Oil consumption generally increased with load. The results are very competitive compared to four-stroke engines. The 500-hour test was designed to put high stress on the engine to accelerate evidence of wear.The average load over the 500 hours was 81% of peak load. A ten-hourcycle was repeated 50 times and consisted of idle, rated power, mid power, peak torque, and the lowest fuel consumption point (B75 on the SET cycle). After 500-hours, the power cylinders under study experienced zero performance degradation with the engine finishing in good condition. There were not any measurably differences in oil consumption before and after the 500 hour test. These results demonstrate the capability of the OP engine to achieve low oil consumption with durable hardware with good initial durability. While more extensive durability testing must be undertaken for a new OP engine design –as with any new engine design –the results to date provide a good indication that low oil consumption and good durability can be achieved.

Hopefully the longer duration durability tests also pan out.

 

[87Octane]

Some News (from 2018) on putting electric motor-generators on the crankshafts of opposed piston engines (remember a single cylinder opposed piston engine has two crankshafts, so that would mean one motor-generator for each piston):

ARPA-E announces $98M in funding for 40 OPEN projects; two opposed-piston engines projects receive $10M total

The US Department of Energy announced $98 million in funding for 40 new projects as part of OPEN 2018, the Advanced Research Projects Agency-Energy’s (ARPA-E) latest open funding opportunity. OPEN solicitations are an open call to scientists and engineers for transformational technologies across...

www.greencarcongress.com

The top awardee in this segment is Pinnacle Engines (earlier post), which is receiving $8 million for the design and demonstration of an electrification-enabled full-featured opposed piston 4-stroke engine for hybrid and range extender applications.

Pinnacle Engines will electrify its four-stroke, spark-ignited, opposed-piston engine to improve fuel efficiency and reduce its cost. Electric motor-generators on each crankshaft will improve engine efficiency by modifying the piston dynamics and resulting combustion process.

In addition, Pinnacle will employ high rates of exhaust gas recirculation and a low temperature combustion strategy, which will improve knock tolerance and reduce heat loss, pumping work, and NOx emissions. Pinnacle’s proposed technology will reduce fuel consumption beyond that of state-of-the-art series hybrid electric vehicles.

A second opposed-piston engine project is led by Achates Power (earlier post). Achates Power will develop a highly efficient opposed-piston engine for hybrid vehicles (“HOPE-Hybrid”) using a unique engine design that minimizes energy losses typical in conventional internal combustion engines.

A motor-generator integrated on each engine crankshaft will provide independent control to each piston and eliminate all torque transmitted across the mechanical crankshaft connection, thus reducing engine size, mass, cost, friction, and noise.

The application of high-bandwidth power electronics will further improve engine efficiency through the real-time control of the piston motion and combustion process. If successful, the proposed technology will offer light- and heavy-duty vehicle manufacturers a cost-effective solution to improve vehicle fuel efficiency and reduce transportation carbon dioxide (CO2) emissions.

 

[87Octane]

The part (mentioned in the previous post) about the motor-generator being able to independently control each piston I find extremely interesting.

For example, Lets say the opposed piston engine was made to have a low connecting rod length to stroke length ratio. It could still benefit (because of the effect of the motor-generator) from a long dwell time at TDC and thus benefit from more efficient combustion.

 

[HumanPerson]

As i've been riding the ebike i keep thinking about a 4 stroke build LOL am goin crazy with this weather !

 

[87Octane]

Here are some pictures of a 110cc opposed piston 4 stroke designed by Pinnacle:

Greaves Cotton @ Auto Expo 2018

Greaves Cotton @ Auto Expo 2018

www.team-bhp.com

According to the link it makes 7 HP @ 6500 rpm.

P.S. Here is a video with Pinnacle engines demonstrating how the sleeve valve works: