Astron reinvents the internal combustion engine

PISTONS, GOODBYE? – Red line at 25,000 rpm: will it be the turbine of a jet engine? None of this, we are talking about an internal combustion engine, the Omega 1 presented by Astron Aeronautics (Watch the video below), which is however light years away from those that have accompanied us for more than a century. This diversity is reflected not only in diet of stratospheric rotation (the minimum is at 1,000 rpm) but in performance declared impressive: 160 hp and 230 Nm of torque with an engine weight of around 16 kg. the constructive scheme it is very particular since there are only circular elements: 4 rotors, coupling gears and a rotating disc valve, in addition to the axes of rotation of the rotors. The concept is to divide the phases of the internal combustion engine, assigning the intake-compression phase to the green rotors (in the figure) and the combustion-expand-exhaust phase to the red ones.

CAVITY AND TEETH – One of the raw rotors has a recess into which, during rotation, a “tooth” is inserted which occupies it almost entirely. The compression occurs gradually because the two rotors are very close together and the side walls touch the tine, which pushes the air in front of it into a smaller and smaller volume as, in its rotation, the tine itself- even approaches the point where the rotors touch. At this point, the compressed air passes through a rotating disc valve (shown in gray in the video) and reaches the chamber which contains the red rotors. This particular valve is a disc with an opening that rotates with the rotors: air can only pass through it when it encounters this “window”. Immediately after, the tooth enters the cavity, preventing the compressed air from flowing back. Once the valve is passed, the air enters”combustion chamber» : These are two rotors (in red in the figure and in the video) very similar to those of compression: one with the tooth, therefore, and the other with the cavity. Everything is timed so that the compressed air penetrates “behind” the tooth: at this stage, yes inject the fuel and you do release the spark. The combustion gases “push” the tooth with a very high efficiency because their action lasts almost a full revolution (it’s a long expansion similar to that of Atkinson cycle engines) and is then expelled from a hole near the point of combustion. the tooth enters the groove of the other rotor. Also in this case, the dent is so close to the wall of the combustion chamber that the exhaust gases cannot “remove” it.

EVERYTHING LOOKS VERY NICE – It is therefore an operation which, while retracing the phases of a classic 4-stroke engine, implements them with solutions completely different of those of piston engines. We remind you that the rotating disc valve is not a new solution and is widely used in two-stroke motorcycle engines: the Vespa, for example, used a “shouldered” crankshaft shaped in a particular shape for this purpose . Fuel is injected with a richer stratified charge near the spark plug (similar to the HCCI system used in the Mazda 3 Skyactiv-X) up to around 10,000 rpm, then switched to a homogeneous charge. The shafts which carry the rotors are hollow and therefore abundant cooling air can pass through and it is observed that the oil only reaches their bearings and timing gears: the combustion chamber is therefore never exposed to the lubricant and the oil pump absorbs very little because it has a small flow. The idea is undeniably innovative, effective (we are talking about a thermal efficiency of nearly 80% thanks also to the high compression rate) and declares itself one very low production of nitrogen oxides. Internal friction is very low (the rotors don’t touch the walls and there are no piston rings and all the other sliding parts of reciprocating engines) and it is possible to “skip” combustion. Astron Aerospace claims that at full speed, it is possible to inject fuel every revolution, or even every 10 or 50 revolutions, depending on the power demand: consumption can therefore be very low.

DOUBTS ARE NOT LACKING – Since simple is not synonymous with easy, such a sophisticated construction gives birth some questions. The sealing of the intake air and the exhaust gases is entrusted to rotors and a rotary valve which work with very small tolerances in the cavities which house them. What will happen to surfaces exposed to heat? Will normal thermal expansion be uniform or will some distortion occur which could lead to undesirable and dangerous contacts? To avoid this, you can use materials “Exotic” expensive: for aeronautical use the cost is a less restrictive barrier but it is possible to produce this engine at competitive costs for the car market? In fact, the number of moving parts is so low (Astron claims it’s comparable to a lawnmower engine) that the price may not be so prohibitive. This engine, given the very favorable weight/power ratio and its ability to run at constant speed, could be excellent for compact and powerful cars. range extender: while waiting to see some concretizations we underline the fact that Astron Aerospace collected consequent financings in a short time.

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