Controlled combustion engine

The Revetec Controlled Combustion Engine (CCE) is a type of internal combustion engine designed by Brad Howell-Smith in 1995. It uses two counter-rotating cams instead of a crankshaft driving two horizontally opposed pistons [1] while retaining an identical cylinder head assembly to conventional engines.

It is around a quarter the size and weight of a conventional engine of similar output and uses fewer moving components. A four or two stroke cycle can be used and it can run on petrol, diesel, compressed natural gas or ethanol.

During the power stroke, maximum mechanical advantage 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.

Because the piston assembly only moves in one dimension (unlike the case in an engine with connecting rods), contact with the cylinder wall is minimised, which reduces wear and lubrication requirements. The cams create less piston shock, which allows ceramic components to be used. The counter-rotating nature of the cams means that most rotational forces are cancelled, which eliminates the need for a heavy flywheel. The engine can run in either direction if symmetrical lobes are used.

Background

The idea came to Howell-Smith, an automotive engineer residing in Australia, during REM sleep. 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 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 site in Sydney. 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. Revetec's business model is to license its technology to engine producers worldwide.

Engine Description

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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. The expanded gas then forces the bearings down the ramps of the cams spreading them apart ending the stroke. The point of maximum mechanical advantage or transfer is around 10deg ATDC (the piston moving approximately 5% of its travel) making the most of the high cylinder pressure.

This compares to a conventional engine that reaches maximum mechanical advantage around 40deg ATDC. (after the piston has moved through 40% of its travel, losing valuable cylinder pressure). 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. This also reduces piston shock to a negligible amount making ceramic technology suitable. 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.

Advantages

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Summaries of CCE advantages are as follows:

• approximately one half the size and weight of a conventional engine (for similar applications) combined with improved output substantially increases power/weight and torque/weight ratio.
• 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 of forced aspiration.
• Eliminated irregularly reciprocating components such as connecting rods. No second order balancing required
• Output shaft can be run in either direction if multilobed cams with symmetrical lobes are employed.
• All rotational forces are counteracted via the counter rotating cam – eliminates the need for a heavy flywheel.
• Torque and power output can be varied using a fixed capacity and piston stroke.
• 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 to be used reducing power loss from compression cycle.
• Able to fire on a leaner mixture than conventional engines.
• Maximum mechanical advantage can be applied to output shaft at only 10 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 two-stroke).
• 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.

Patents

Revolution Engine Technologies Pty Limited (a wholly owned subsidiary of Revetec Limited) holds patents or has made patent applications for the CCE design in 28 countries, including the United States of America, Europe, Australia, China, the United Kingdom and Japan. The beneficial ownership of the patents and patent applications was assigned to Revetec on 14 September 2005.

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

Abstract : An engine comprises two counter rotating multilobate cams which are acted upon by a pair of diametrically opposed pistons which are rigidly interlinked by connecting rods. Differential gearing is provided to time the counter rotation of the cams. The following is an examiner's statement of reasons for allowance: The prior art fails to teach or fairly suggest the invention as a whole including a shaft having a first multilobate cam axially fixed to said shaft and an adjacent second multilobate cam differentially geared to said first multilobate cam for axial counter rotation about said shaft, at least one pair of cylinders, the cylinders of each pair being diametrically opposed with respect to said shaft with said multilobate cams interposed therebetween, and a piston in each said cylinder, said pistons of a pair of cylinders being rigidly interconnected.

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

Government Grants

Revetec receives Federal Government Grant of over AUD$1 million Media Release from The Hon Ian Macfarlane, MP. 8 January 2007. Australian Industry, Tourism and Resources, Ministers and Parliament Secretary website link.

Applications

from Revetec website

The advantages of Revetec’s engine technology can be applied to most internal and external combustion engines for use in motor vehicles, trucks, buses, motorcycles, pumps and generators, light aircraft engines, diesel and marine engines.

The CCE integrates well with existing power plants and can utilise almost all existing engine technology with increased efficiency.

The CCE engine is extremely well suited for high torque applications such as generators, machinery and light aircraft.

Performance

Latest Announcement of performance of the X4 Engine posted on the NSXA (National Stock Exchange of Australia Director's Announcement May 2007 "X4 Engine Testing' A dyno graph of the Revetec 1.38litr engine is shown on their development page Engine Development

Images

External links

• Revetec website
• Piston Broker an Autospeed special feature.
• Cams Replace Crank in new Engine Design from Automotive Design & Production.
• Revolutionary engine was designed and built in less than six months a Siemens/UGS Customer Case Study of CAD Design
• Pure Energy Systems listing showing the Revetec engine as a New Energy Congress Top 100 from Peswiki