Internal Combustion Engine

RadMax® Internal Combustion Engine

Compression Ignition and Spark Ignition Engines
The RadMax internal combustion engine can be designed to utilize compression ignition (diesel engine) or spark ignition (gasoline, natural gas, etc.). In a compression ignition engine, the compression ratio is high enough (16:1 to 20:1) to ignite the fuel sprayed into the combustion chamber. The lower compression ratios (8:1 to 11:1) used by gasoline and natural gas require the addition of an ignition system to ignite the fuel.  Various prototype RadMax engines for both compression-ignition and spark-ignition configurations have been built ranging from 10 to over 300 horsepower. Designs have also been completed for a RadMax external-combustor turbine engine.

Regardless of the ignition type, the basic four-stroke principle is the same.

Four-Stroke Engine Basics
The four-stroke piston engine was first demonstrated by Karl Otto in 1876, hence it is also known as the Otto cycle. The four-stroke cycle is the most common engine type today. It powers almost all cars and trucks. The RadMax rotary, internal-combustion engine represents a dramatic departure from existing piston engine design, which has not changed significantly in over 100 years. The four strokes of the cycle are (1) intake, (2) compression, (3) power, and (4) exhaust. On a piston, internal-combustion (or reciprocating) engine, each crankshaft revolution corresponds to one full stroke of the piston, therefore the complete cycle requires two revolutions of the crankshaft. 

RadMax Internal Combustion Engine Basics
A RadMax internal-combustion engine works in a completely different way than the conventional, reciprocating-piston engine. The RadMax rotary, internal-combustion engine also uses the four-stroke principle. However, combustion chambers form between the rotor, outer housing walls and vanes, and their volumes change as the vanes move during rotation. Because the RadMax design can have up to 12 vanes, the engine generates an incredible 24 combustion events (power strokes) per rotation, 12 on the upper side of the rotor and 12 on the lower side. Due to this efficient rotary design, a RadMax internal combustion engine will produce twice the horsepower per revolution compared to an equivalent displacement-piston engine. 

Intake: The intake cycle starts when the leading vane of each chamber, defined by a pair of consecutive vanes on the rotor, passes the intake port. At the moment when the intake port is exposed to the chamber, the volume of that chamber is close to its minimum. As the leading vane moves past the intake port, the volume of the chamber expands, drawing air into the chamber. When the chamber’s trailing vane passes the intake port, that chamber is sealed off and compression begins. 

Compression: As the rotor continues its motion around the cam, the volume of the chamber decreases and the air gets compressed. By the time the leading vane has made it past the fuel injection port, the volume of the chamber is close to its minimum. At this point, conditions are right for combustion. 

Combustion/Power: In a compression-ignition engine, the compression cycle heats the air to a high enough temperature to create combustion when fuel is injected. In a lower compression engine, a spark must ignite the air/fuel mixture. Pressure quickly builds once combustion occurs, forcing the rotor to turn and creating power until the chamber’s leading vane passes the exhaust port. 

RadMax Internal Combustion Engine Cycle

Exhaust: Once the leading vane passes the exhaust port, the high-pressure combustion gases in the chamber start to flow out of the port. As the rotor continues to move, the chamber volume decreases, forcing the remaining exhaust out of the port. By the time the volume of the chamber is nearing its minimum, the exhaust port closes. The chamber has now completed one revolution around the cam and the four-stroke cycle for that chamber repeats.

The RadMax rotary, internal-combustion engine utilizes passive ports rather than mechanically operated valves. Although the RadMax internal-combustion engine is a rotary design and benefits from the basic premises of such a design, unlike the Wankel engine, RadMax technology accomplishes chamber sealing using axial vane motion rather than eccentric rotor motion.  Additionally, all RadMax internal-combustion engines can easily be designed to accommodate an extended expansion cycle for greater engine efficiency.

A RadMax internal-combustion engine is characterized by:

  • Compact size and weight (~ 25% of a comparable hp piston engine)
  • High power to weight ratio (>1 hp/lb)
  • Continual, smooth rotary motion
  • Easily scalable from 20 hp and higher
  • High compression ratio capability (up to 20:1) allows use with many fuels
  • Easier field maintenance and repair
  • Low part count (less than 75 discreet parts vs. over 1,000 for a typical piston engine); fewer moving parts results in reduced assembly and maintenance cost, increased reliability and reduced noise levels 
  • Simple intake and exhaust cam porting does not require complicated valving systems

Download a RadMax engine brochure here.