The covaxe® engine brings together the concepts of the barrel or axial engine, the opposed piston engine and new, patented techniques to provide a low carbon, low particulate emissions internal combustion engine that promises to be disruptive technology for the 21st century.
Axial/barrel engines have been around since about 1910 but have never seriously challenged traditional crank-based ICEs, so one might reasonably ask what has changed? The problems with axial engines have been (i) achieving a durable mechanism to convert the linear piston force into torque, be this a swash plate, cam or wobble plate, and (ii) difficulty of assembly and disassembly for maintenance.
Advances in tribology and computational analysis enable us to have confidence in solving the first of these challenges and a covaxe®-patented modular cylinder approach overcomes the second. The axial engine architecture allows us to implement our constant volume combustion cycle, delivers extremely low vibration in a convenient quasi-cylindrical package, and we have overcome the traditional limitations associated with the configuration.
Two stroke opposed piston compression-ignition engines have a number of advantages, including low vibration, the avoidance of a heavy, high thermal mass cylinder heads, the avoidance of valve gear, and the ability to perform very complete linear scavenging of exhaust gases prior to compression of clean air for the next power cycle. These benefits are recognised in a number of engine research and development projects that are ongoing around the world today.
For those that are interested, the remainder of this section provides a view of some historical axial and opposed piston engines.
In an axial engine, the linear motion of the pistons is converted to torque using either a swash plate, a cam or a wobble plate, as shown
The Statatax engine, which used a swashplate, is believed to have powered an aircraft in 1914, whilst another, the seven-cylinder Redrup Fury, known to have flown in 1929, is shown in the header image with part of the casing cut away to show the swash-plate linkage. The Fury was one of a whole series of engines designed by Charles Redrup whose story is told in Diesel Publishing book, “The Knife and Fork Man”. He always claimed that most of his prototypes were made in his home workshop with little more than a knife and fork!
A recent engine project based on the cam principle, was known as the Dyna-Cam, a double-ended spark-ignition barrel engine with twelve cylinders arranged on either side of one cam.
Opposed Piston Engines
During the 1920’s the German company Junkers developed an unusual engine with two opposed pistons in each cylinder. The two sets of opposed pistons drove two crankshafts, linked together by a train of gears to the drive shaft. The engine was a two-stroke diesel, and used ports at each end of the cylinder liner for inlet and exhaust. Such engines were produced under licence by Napier during the 1930s. In the 1940s, the British Admiralty developed the Napier design to produce a highly successful opposed piston engine called the Deltic. This entered service in the 1950s and many such engines were used in small warships and British Rail locomotives.
Modern two-stroke opposed-piston engines are manufactured by Weslake Air Services in the UK and Achates Power in the USA.
Weslake Air Services Limited engine