Where is the name RBR-engine coming from?
RBR-engine stands for Radial Bi Rotary - Balanced Piston Combustion Engine..
This is a further development of my existing radial 4 cylinder 2 stroke engine having the same balanced drive mechanism in a pressured charged crankcase. (picture in the gallery).
Rotary and radial engines look strikingly similar when they are not running and can easily be confused, since both have cylinders arranged radially and pointing outward around a central crankshaft.
There are two major types of rotary engines. The pistonless rotary engine like a Wankel engine and the rotary engine with pistons. Piston rotary engines have a stationary crankshaft and the entire cylinder block rotates around it.
( ex. Gnome et Rhône )
Radial engines use a rotating crankshaft in a fixed engine block,
In a bi-rotary piston engine however, the crankshaft rotates also, as in a radial ,and the cylinders are geared to turn in the opposite direction as in a rotary. ( ex. Siemens-Halske_Sh.III )
Another kind of bi-rotary engines is a configuration with "open topped " cylinders. Surrounding them is a fixed ring in which are placed alternating inlet port, spark plug, and exhaust port openings. Plates at the front and rear of this ring provide bearings for the shaft, accessory attachments, engine mounting points, etc. The engine has no expensive valve train but still operates on the four-stroke principal (inlet, compression, power, exhaust) by sequentially presenting the open top cylinders to the relevant areas of the head-ring.( example Mawen Engine and this RBR Engine)
Three key factors contributed to the rotary engines success :
* Smooth running: Rotaries deliver power very smoothly because the relatively large rotating mass of the cylinders acting as a flywheel.
* Weight advantage: many conventional engines had to have heavy flywheels added to smooth out power impulses and reduce vibration. Rotary engines gained a substantial power-to-weight ratio advantage by having no need for an added flywheel.
* Improved cooling: when the engine was running the rotating cylinder block created its own fast-moving cooling airflow, even with the engine stationary.
Why is this a balanced engine ?
Engine balance is the design, construction and tuning of an engine to run smoothly. Improving engine balance reduces vibration and other stresses and, within a respectable percentage, improves the overall performance, efficiency, cost of ownership and reliability of the engine, as well as reducing the stress on other machinery near the engine.
This is a naturally smooth engine design, because all rotating and reciprocating parts are equalized with each other , without creating any rocking couple or torsion vibrations.
Although a small engine was build with 3 inlet gates and 3 outlet gates, a bigger engine with 4 inlet gates and 4 outlet gates is under development having even ignitions so the explosion forces are balanced as well. In this configuration the balanced drive mechanism is almost acting like free-pistons.
What is the bore/stroke ?
The engine has a oversquare bore/stroke ratio in order to keep average piston speed and top end seal velocity low. The engine has fairly long con rods, strongly reducing side loading. The pistons with the connected anchors have no side loading.
What about ignitions per revolution?
The first test model RBR-engine had 12 ignitions per rotor revolution. The engine under construction has 16 ignitions per rotor revolution. Wankel has only 3 ignitions per rotor revolution. This means that the first RBE-engine had 2.5 ignitions per crankshaft revolution compared to Wankel which has 1 ignition per crankshaft revolution.
What about the lubrication and sealing of the Piston Rings
The three main functions of piston rings in internal combustion engines are:
Sealing the combustion chamber. Supporting heat transfer from the piston to the cylinder wall. Regulating motor oil consumption. The gap in the piston ring compresses to a few thousandths of an inch when inside the cylinder head. Most automotive pistons have three rings: The top two whilst also controlling oil are primarily for compression? sealing (compression rings); the lower ring is for controlling the supply of oil to the liner which lubricates the piston skirt and the compression rings (oil control rings). In a two-stroke engine the lower ring is scraping oil in the inlet port of a two stroke ( not meeting emissions regulations ). This RBR engine is just a normal working 4 stroke.
What about the top-seals compared to Wankel's apex-seals ?
The top seal does not have a oil problem, because theoretically there is no oil there. However this is a compression ring that needs some kind of controlled lubrication for the same three reasons.
Wankel suffers from scatter marks in the rotor house, caused by the flat vibrating and oil consuming apex-seals. The RBR-engine top seals are more non vibrating conventional shaped piston-rings.
The RBR-engine rotor revolution is 5 times slower than a Wankel , having thus less friction , less wear and no oil consumption compared with a Wankel.
This compression ring is also sitting in a much cooler environment than in the hot wankel rotor witch has to get rid of his internal heat trough the apex-seals.
What about fuel efficiency?
The Wankel suffers from high fuel-consumption caused by the non ideal combustion chamber and has difficulties to cope with emissions regulations. ( Mazda RX8 is no longer allowed in Europe ). The RBR-engine is a normal 4 stroke piston engine.
What about gyroscopic effect in case of use for aviation ?
This engine has a bonus ,the counter-rotating masses tend to cancel out the gyroscopic forces of the engine. This is achieved by using a planetary gear house in the rear of the crankcase.
What about propeller efficiency in case of use for aviation ?
Because of the reduction gearing effect ( approx. 1/5 ) of the engine effectively running at for instance 5000 rpm for only 1000 rpm of the airscrew directly connected to the crankshaft, there is a increased propeller efficiency.
Is this engine suited for generators or green technology hybrids ?
Cylinder bank and crankshaft has a 1 to app. 5 ratio. This means that a engine ideal designed and running at a fix full throttle has very interesting rpm-configurations.
A crankshaft running at 3000 rpm has the cylinder rotor running at 600 rpm, 6000 rpm crankshaft correspond with 1200 rpm cylinder rotor. These are all very interesting AC-electromotor rpm's.
Is this engine easy to build ?
This engine is build with standard parts machined on presently known standard machines. The engine parts are simply re-arranged. A You-tube search is showing a lot of hobbyists building small radial and rotary engines . This one is even without valve train and yet a 4 stroke.
Here are three examples of my favourites.
Jerry Hale's special rotary engine Homemade radial engine The vintage aviator CAD animation radial engine Re-boost Plastic automotive engine ?
Although this engine has a very interesting power to weight ratio , it is to be considered that voluminous parts ( ex. bearing houses ) can be built out of Torlon thermoplastic , a material that has properties that out-perform all but the most exotic composites and polymers. A plastic Cosworth engine raced successfully in the International Motor Sports Association's Camel GT Championship.
What about the Atkinson cycle ?
The Atkinson cycle is designed to provide efficiency at the expense of power density, and is used in some modern hybrid electric applications. In a Atkinson cycle the power stroke is longer than its compression stroke, therefore the engine can achieve greater thermal efficiency than a traditional otto-cycle engine. This can be achieved in the RBR-engine by longering the inlet gates on the fixed outer ring to shorten the compression stroke.
EGR Valve ?
The engine can easily be provided with a EGR valve. The inlet and outlet gates are positioned close to each other. The EGR valve helps the engine more efficiently and completely burn fuel by recirculating a portion of exhaust and running it through the combustion process again. This results in a cooler, more complete burn of the fuel which decreases noxious emissions by prohibiting the formation of some harmful gases.
