Controlled Combustion Engine (CCE) is a term used by Revetec, an engine design company, to identify a type of experimental internal combustion engine

Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

 (ICE) designed by Brad Howell-Smith. It uses two counter-rotating cam

Cam

A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path...

s instead of a crankshaft

Crankshaft

The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...

. Pairs of cylinders oppose each other in a boxer flat engine

Flat engine

A flat engine is an internal combustion engine with multiple pistons that move in a horizontal plane. Typically, the layout has cylinders arranged in two banks on either side of a single crankshaft and is sometimes known as the boxer, or horizontally opposed engine. The concept was patented in 1896...

 or "X" arrangement.

History

The idea came to Howell-Smith, an automotive engineer residing in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, during REM sleep in 1995. He designed five different engine layouts with variations on each and established Revolution Engine Technologies Pty Ltd in 1996 with a budget of A$2000. The first working prototype

Prototype

A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...

 was built by father-in-law Peter Koch in Howell-Smith's garage. Howell-Smith founded a company named Revetec Limited and set up a research and development

Research and development

The phrase research and development , according to the Organization for Economic Co-operation and Development, refers to "creative work undertaken on a systematic basis in order to increase the stock of knowledge, including knowledge of man, culture and society, and the use of this stock of...

 site in Sydney

Sydney

Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...

. The prototype was displayed at the 1996 Sydney International Motor Show which brought public awareness to the design. Work began on a second prototype intended for use in generators and pumps, however interest expressed by the Middle East automotive market shifted focus towards automotive applications.

Engine description

The REVETEC Engine design consists of two counter-rotating "trilobate" (three lobed) cams geared together, so both cams contribute to forward motion. Two bearings run along the profile of both cams (four bearings in all) and stay in contact with the cams at all times. The bearings are mounted on the underside of the two inter-connected pistons, which maintain the desired clearance throughout the stroke.

The two cams rotate and raise the piston with a scissor-like action to the bearings. Once at the top of the stroke the air/fuel mixture is fired. This is the power stroke

Power stroke

Power Stroke may refer to:In motoring:*Power stroke , the stroke of a cyclic motor which generates force*Ford Power Stroke engine, Ford diesel engineOther:*In baseball, a batter who hits for extra bases is said to have a power stroke...

 during which the maximum mechanical advantage

Mechanical advantage

Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Ideally, the device preserves the input power and simply trades off forces against movement to obtain a desired amplification in the output force...

 is reached after the piston has moved approximately 5% of its travel from top dead centre (approx. 10° ATDC), which makes better use of the high cylinder pressures at this point in the cycle. In comparison a conventional engine reaches its maximum mechanical advantage after the piston has moved approximately 40% of its travel from top dead centre (approx. 60° ATDC). A side effect of this is a CCE can idle at a much lower RPM

Revolutions per minute

Revolutions per minute is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis...

.

Because the piston assembly only moves in one dimension (unlike the case in an engine with connecting rod

Connecting rod

In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts linear motion into rotating motion....

s), contact with the cylinder wall is minimised, which reduces wear and lubrication requirements. The cams create less piston shock

Shock (mechanics)

A mechanical or physical shock is a sudden acceleration or deceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation....

, which allows ceramic

Ceramic

A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...

 components to be used. The engine can run in either direction if symmetrical lobes are used.

The effective cranking distance is determined by the length from the point of bearing contact to the centre of the output shaft (not the stroke).

The dual bearings contact the two cams in the opposite side which cancels the side forces out. The piston assembly does not experience any side force which will reduce wear and lubrication requirements at the cylinder contact. One module which consists of a minimum of five moving components, produces six power strokes per revolution. Increasing the number of lobes on each cam to five produces ten power strokes without increasing the number of components.

Claimed Advantages

The following advantages are claimed for the CCE engine at.

• Predicted production power to dressed weight ratio is 0.40 bhp/lb. For comparison a Continental 100 hp engine is 0.465 hp/lb, dressed
• Efficiency - Recent tests gave good results, for a gasoline engine, when running lean.
• fewer moving and total components. As a result of fewer components, more easily manufactured than conventional engines.
• identical cylinder head assembly (“top end") to conventional engines. Most existing head technology can be either adapted or utilised.
• Flexible design - can be four-stroke, two-stroke, petrol, diesel or gas, natural or forced aspiration.
• Eliminated irregularly reciprocating components such as connecting rod
  Connecting rod
  In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts linear motion into rotating motion....
  
  s. No second order balancing required.
• Output shaft can be run in either direction if multilobed cams with symmetrical lobes are employed.
• The CCE can be designed to operate at greatly reduced operating speeds while delivering high torque output.
• Substantial reduction in stroke reduces heat loss through cylinder wall.
• Extended piston dwell is possible because engine design allows a lower than normal compression ratio
  Compression ratio
  The 'compression ratio' of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity...
  
   to be used reducing power loss from compression cycle.
• Able to fire on a leaner mixture than conventional engines.
• Maximum mechanical advantage
  Mechanical advantage
  Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Ideally, the device preserves the input power and simply trades off forces against movement to obtain a desired amplification in the output force...
  
   can be applied to output shaft at only 20 degrees ATDC utilising high cylinder pressure early in the stroke, compared to around 60 degrees ATDC for conventional engines.
• Lower emissions can be achieved due to increased control over combustion.
• Low idle speed due to increase in mechanical efficiency at the top of the stroke.
• Little or no bore contact/piston side thrust, which reduces wear on cylinder bore.
• Can have different port timing on compression stroke than power stroke allowing better control.
• Lower centre of gravity on the boxer design.
• Due to controlled piston acceleration rates the CCE reduces engine vibration.
• A hollow output shaft can be utilised for specialty applications, such as peristaltic pumps.

Disadvantages

The following have yet to be verified independently.

• Vibration
• Reliability, especially when running lean as is required for good economy.
• Emissions

Patents

U.S. Patent 5,992,356 "Opposed piston combustion engine "; November 30, 1999; Howell-Smith; Bradely David (Worongary, AU).

Revetec has a PCT patent application pending for the "X" design lodged late 2006.

Performance

A dyno graph of the Revetec 1.38litr engine is shown on their development page, shows a flat torque curve.

Test results (11 November 2007) on the X4v2 engine showing torque and power curves and the fuel injection map.

In April 2008, Revetec completed their first Independently Certified Test Report carried out by Orbital Australia, achieving a repeatable BSFC

Brake specific fuel consumption

Brake Specific Fuel Consumption is a measure of fuel efficiency within a shaft reciprocating engine.It is the rate of fuel consumption divided by the power produced. It may also be thought of as power-specific fuel consumption, for this reason...

figure of 212g/kW-h (38.6% efficiency) with a best tested figure of 207g/kW-h (39.5% efficiency).

External links

• Revetec website
• Cams Replace Crank in new Engine Design from Automotive Design & Production.