The Wankel Rotary Engine Is Back In Production Thanks To Mazda!
How Rotary Engines Work    • This 3D Printed Rotary Engine Is Geni...  
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From Mazda:
"With the discontinuation of the RX8, Mazda ended massproduction of the rotary engine in June 2012. Today, some 10 years later, the rotary engine is making a comeback. This new rotary engine has been adapted to meet the needs of our times and is now being used to generate power rather than as a drive unit.

While the 13B Renesis engine used on the RX8 was a 654 cm3 tworotor engine, the MX30 eSkyactiv REV uses an 830 cm3 single rotor format for the rotary engine generator. With a 120 mm generating radius (R) and 76 mm rotor width, its compact size enables coaxial placement and integration with the electric motor, decelerator and generator to achieve a unit with an overall width of less than 840 mm that fits on the same body frame as the MX30 BEV. We also successfully reduced the weight of the engine by over 15 kg by using aluminium for the side housing section of the engine structure instead of the iron used on the Renesis engine.

The main contributor to increasing fuel economy and reducing emissions on the MX30 eSkyactiv REV rotary engine was the use of direct fuel injection. When fuel is injected into the ports on a conventional rotary engine, a lot of the airfuel mixture ends up at the back of the combustion chamber, not fully combusting and eventually being expelled as unburned gas. This has a negative effect on both fuel economy and engine output.

The rotary engine on the MX30 eSkyactiv REV uses direct fuel injection, making it possible to distribute the airfuel mixture to the main combustion area and achieve more efficient combustion. Additionally, direct fuel injection atomises the fuel at the time of injection making it possible to sufficiently vaporise fuel even at lower temperatures. This also helps prevent the injection of excess fuel.

The engine also adopts an exhaust gas recirculation (EGR) system to improve fuel efficiency. Adding an EGR system that operates mostly at low rpm and low loads improves fuel economy by preventing cooling loss caused by rotary engine combustion chambers having a greater surface area than those of a reciprocating engine.

Apex seals are attached to the tip of each rotor to ensure the combustion chambers are airtight. For the MX30 eSkyactiv REV, we increased the width of these seals to 2.5 mm to improve wear resistance. We also changed the plating on the trochoid surface inside the housing to reduce wear and frictional resistance. For the sides of the housing, we use aluminium for the surface of the side housing and have added high velocity oxygen fuel coating to add a ceramic coating which also reduces wear and frictional resistance."

Related Videos:
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Mazda's Hydrogen Rotary Engine    • Mazda Built A Hydrogen And Gasoline P...  

References:
MX30 Press Kit https://eu.mazdapress.com/forms/logi...
RX8 Press Kit https://newsroom.mazda.com/en/cars/11...
BMW i3 Press Kit https://www.bmwusanews.com/newsreleas...
VVT Study https://doi.org/10.1016/S03605442(02...
Rotary Engine Intake Timing Study https://doi.org/10.2298/TSCI180504058Z
Mazda Patent https://patents.google.com/patent/US2...

Hat Tips:
Mazda VVT Patent https://carbuzz.com/news/mazdasnewr...
MX30 REV Background https://www.greencarreports.com/news/...

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