AU2018100117A4 - Improved opposed-piston internal combustion engine - Google Patents

Abstract

An improved engine directed to a Low friction muLti-cyLinder; two cycLe opposed-piston internaL combustion engine primariLy suited to the GeneraL Aviation Industry. In an aspect, there are two pistons per cyLinder and two synchronized crankshafts, compression ignition using dieseL fueL and is a Liquid cooLed unit with a 1.6 to 1 reduction. In an aspect turbo charged to 60 inches of mercury absoLute boost and 2 sets of fuLLy redundant common raiL pumps and injectors. DeveLoping 75hp, per cyLinder at 4,300rpm respectiveLy. Crank synchronization, propeLLer drive and reduction are via a carbon-fibre toothed beLt drive system. Pistons are oiLed by a through conrod oiL way that onLy aLLows oiL to the piston rings at the top of the piston stroke. CyLinder barreLs have an eLectron-beam weLded cooLing jacket with no gaskets or seaLs. 'I// CUTAWAY GENERAL ARRANGEMENT OF A 3 CYLINDER VERSION

Description

IMPROVED OPPOSED-PISTON INTERNAL COMBUSTION ENGINE

Field [0001] The invention relates to internal compression ignited two cycle diesel engines.

Background [0002] An opposed - piston engine is a reciprocating internal combustion engine in which each cylinder has a piston at both ends, and no cylinder head. In 1882 James Atkinson developed the Atkinson cycle, a variant of the four stroke Otto cycle. The first implementation of this was arranged as an opposed piston engine, the Atkinson differential engine.[1] [0003] The first opposed - piston diesel engines were developed in the beginning of the 20th century. In 1907, Russian Raymond Koreyvo, the engineer of Kolomna Works, built an opposed - piston two-stroke diesel with two crankshafts connected by gearing. Later engines, such as the Junkers Jumo 205 diesel aircraft engine (1930s) and today's Achates Power engine, use two crankshafts, one at either end of a single bank of cyli nders.

[0004] Koreyvo, Jumo and Napier Deltic engines used one piston per cylinder to expose an intake port, and the other to expose an exhaust port. Each piston is referred to as either an intake piston or an exhaust piston depending on its function in this regard. This Layout gives superior scavenging, as gas flow through the cylinder is axial rather than radial and simplifies design of the piston crowns.

[0005] ALL diesel engines use compression ignition, a process by which fuel is injected after the air is compressed in the combustion chamber, thereby causing the fuel to self-ignite. By contrast, gasoline engines utilize the Otto cycle, or, more recently, the Atkinson cycle, in which fuel and air are mixed before entering the combustion chamber and then ignited by a spark plug.

[0006] It is an object of this improved engine of the present invention to exploit considered mechanical inadequacies and features as described above.

Summa ry [0007] In a broad format this improved engine is directed to a low friction, multi-cylinder, two cycle opposed - piston internal combustion engine primarily suited to the General Aviation Industry. In an aspect, there are two pistons per cylinder and two synchronized crankshafts, compression ignition using diesel fuel and is a liquid cooled unit with a 1.6 to 1 reduction. In an aspect turbo charged to 60 inches of mercury absolute boost and 2 sets of fully redundant common rail pumps and injectors. Developing 75hp per cylinder at 4,300rpm respectively. Crank synchronization, propeller drive and reduction are via a carbon-fibre toothed belt drive system.Pistons are oiled by a through conrod oil way that only allows oil to the piston rings at the top of the piston stroke. Cylinder barrels have an electron-beam welded cooling jacket with no gaskets or seals. C0008D A diesel cycle is used, in contrast to an Otto Cycle (Compression ignition over a spark ignition) to achieve a thermodynamic efficiency(40% opposed to 24%) due to the higher compression prior to ignition. A two-stroke cycle minimises fuel Loss directly to the exhaust system, as only air is used during the scavenge cycle. Fuel is only being injected close to top dead centre when the inlet and exhaust ports are closed. Elimination of spark plugs prevents problems of foul-up and high voLtage interference with instrumentation.

[0009] In an aspect the Liquid cooling design of the improved engine addresses the documented catastrophic engine failure instances caused by shock cooling, a well-known General Aviation Industry safety issue.

[0010] Air-cooled engines require ambient air passing over, which can include rainwater.Mounting the improved engine into a weather-proof enclosure. Liquid cooling removes the likelihood of hot spotting and is quieter. A radiator is more aerodynamicaLLy efficient than an air-cooLed engine and can, through the Meredith Effect be made to produce a small amount of thrust.

[0011] In an aspect a carbon-fibre reinforced polymer, toothed belt in either a straight-cut or chevron pattern facilitates a crank synchronization, propeller drive and reduction drive system.

[0012] The belt is Lightly stressed and has many teeth. ConsequentLy, the pulleys are hard anodised aluminium and of Less weight compared to ground and hardened gears. The belt drive system provides the 1.6 to 1 reduction necessary for peak performance at optimum rpm. There is no lubrication requirement.Transmission is better than 98% efficient, is quiet, very smooth with no backlash and is excellent at suppressing vi brati on.

[0013] Reversible fitting of the belt drive permits the belt to be roved around the pulleys to produce either a clockwise or counter clockwise rotation of the propeller, whilst retaining uniform engine rotation. Well suited in twin installations where counter-rotating propellers are advantageous for safety.This unidirectional design is a superior solution compared with direct drive engines using a counter-rotating variantthus requiring a separate engine for each propeller rotation requi rement. C0014D In an aspect a thermal isolation ceramic insert is clamped between the steel piston crown and the aluminium piston skirt, preventing heat Loss from the thermodynamic cycle into the piston skirt and improving overall thermal efficiency.

[0015] In the instance of two pistons within a single cylinder, and no cylinder head, this thermal isolation ceramic insert is doubly effective. This also allows the sliding part of the skirt to be at substantially Lower operating temperatures than normal (approximately 120 Degrees Celsius). This makes the skirt much easier to Lubricate effectively and reduces wear on the skirt, rings and cylinder barrel. As the skirt is at a uniform temperature throughout its Length, it is manufactured parallel instead of tapered.

[0016] The steel piston crown acts as a flame shield and protector of the piston assembly. The operating temperature is the average of the combustion chamber (approx. 450 Deg. C.) The thermal isolator is made of ceramic and has a thermal conductivity some 100 times Less than the steel crown. This traps heat in the specific thermal cycle Location increasing effici ency.

[0017] In an aspect a turbine driven supercharger uses exhaust gas pressure and flow to drive a turbine that is coupled to an intake air compressor that increases the air mass entering the engine in direct proportion to the pressure increase.

[0018] The inLet manifold pressure is maintained higher than the exhaust manifold to achieve the through- flow scavenge in the engines two-cycle. These differential pressures are controlled by a computerthat receives data from the gas mass sensor, the engine speed indicator and the inlet manifold pressure gauge. This information is used to control the variable inlet vanes of the compound reclaim turbine. This turbine balances the power requirement of the turbocharger to that required to maintain the gas mass to oxidise the injected fuel as well as to maintain a 1.3 to 1 over - scavenge,required to adequately ventilate the engine. Excess exhaust gas power is returned by this turbine to the driveline. Any shortfall in compressor power requirement is compensated by activation of the auxiliary electric motor as required, including engine start up. C0019U Historically diesel two stroke engines have used positive displacement superchargers to achieve the required fresh air scavenge for operation. This improved engine of the present invention, makes this expensive and heavy piece of equipment redundant. The turbocharger will also be compounded to recover energy normally Lost through a waste gate.

[0020] Cylinder porting design of this improved engine encompasses crankshafts that have a phase angle Less than eight (8) degrees, and includes a longer exhaust port than the inlet port.

[0021] Typicallyin opposed piston designs, the crankshafts are out of phase some 11 to 20 degrees to enable the exhaust ports to open first. With a phase angle Less than eight (8) degreesand Longer exhaust ports, this enables the exhaust ports to open in advance to the inlet port opening, to depressurise the cylinder, before scavenging. The inlet and exhaust ports then close simultaneously. This enables enhanced power distribution between the crankshafts.

[0022] In an aspect the piston skirts are designed without gudgeon pins. Spherical knuckles at the small end of the connecting rod eliminates the need for a gudgeon pin hole in the piston skirt wall. The skirt is round instead of typically oval and is parallel instead of typically tapered.

[0023] The improved design eliminates the gudgeon pin hole in the piston skirt wall, and ensures no oil is Lost to the exhaust ports, this is in stark contrast of the typical oil Loss through a gudgeon pin assembly.

[0024] Having broadly described the invention, an improved engine will now be exemplified with reference to the accompanying drawings briefly described hereafter.

Brief Description of Drawings [0025] Drawing 1/7 Depicts a cut-away general arrangement view of a three-cyLinder version of the engine.

[0026] Drawing 2/7 Figure 1 is a front isometric view of the carbon-fibre reinforced polymer, toothed belt reduction drive system. Figure 2 is the same drive assembly as Figure 1 and depicts the unidirectional capability of the propeller drive pulley.

[0027] Drawing 3/7 Figure Idepicts the exploded view of the thermal isolation ceramic insert assembly. Figure 2 depicts the assembly view of Figure 1.

[0028] Drawing 4/7 depicts the turbocharger system assembly schemat i c. C0029D Drawing 5/7 Exhaust and inlet port opening diagram depicting the 360 degrees of rotation cycle. C0030D Drawing 6/7 depicts the cylinder porting design that has a phase angle less than eight (8) degrees. Figure 1 depicts the initial opening of the exhaust ports. Figure 2 is the initial opening of the inlet ports. Figure 3 depicts both inlet and exhaust ports in the fully open position. Figure 4 depicts both inlet and exhaust ports closing simultaneously. C0031□ Drawing 7/7 Figure 1 depicts the gudgeonless piston skirt assembly. Figure 2 is an exploded isometric view of Figure 1

Ci tation Li st [1] Gingery, Vincent. Building the Atkinson Differential Engine. David J. Gingery Publishing, LLC. ISBN 1878087231.

Claims (5)

1. A carbon-fibre reinforced polymer, toothed belt in either a straight-cut or chevron pattern that facilitates crank synchronization, propeller drive and reduction drive system. Reversible fitting of the belt drive permits unidirectional propeller rotation.

2. A thermal isolation ceramic insert clamped between the steel piston crown and the aluminium piston skirt, preventing heat loss from the thermodynamic cycle into the piston skirt assembly.

3. A proprietary architecture turbine driven supercharger that uses exhaust gas pressure and flow to drive a turbine that is coupled to an intake air compressor increasing the air mass entering the engine in direct proportion to the pressure increase. The computer controlled Turbocharger specifically regulates optimum airflow and air pressure for opposed piston two-stroke engines.

4. Proprietary cylinder porting design whereby the crankshafts have a phase angle Less than eight (8) degrees, and includes a Longer exhaust port than the inLet port enabling the exhaust ports to be opened in advance to inLet port opening to depressurise the cylinder, before scavenging. The inLet and exhaust ports then close si muLtaneousLy.

5. Piston skirts designed without gudgeon pins. Spherical knuckles at the small end of the connecting rod eliminates the need for a gudgeon pin hole in the piston skirt wall. The skirt is round instead of typically oval and is parallel instead of typically tapered.