Yet another annular -- the Quasi-Argus
Posted: Sun Feb 26, 2006 7:29 pm
I've been looking at the almost forgotten Argus valveless engine, whose development was scuttled by the order of the German War Ministry. The Ministry wanted Argus to develop a valve-equipped large size engine based on Schmidt’s ideas, to power a flying bomb. We all know the result. With the end of the war, the Argus company ceased to exist, as far as I know, and no one else has ever attempted to take its valveless design any further.
The Argus worked well with forced intake – after all, the company apparently wanted to power a turbine with this combustor – but I see no real reason why it shouldn’t work with normal aspiration. It looks like Argus thought so, too, as their engineers also toyed with a compressor-less version. I think it merits another look.
Here’s the look I have given to it. It is no longer quite the design the Argus engineers had in mind, I guess. Maybe I can even claim it as mine, but the Argus background is quite obviously there.
The functioning of the intake vortex chamber should be obvious. It offers a completely different impedance to incoming and outgoing flows. The direction of the vortex fights against the outgoing flow but aids incoming flow.
The interesting detail is that the direction of rotation remains the same during both intake and exhaust parts of the cycle. What has occurred to me is a bit weird – If the direction remains constant, well, perhaps a constant, ‘trapped’ vortex might actually be possible in the intake cavity. One that is set in motion by the first expansion, aided by the suction that follows it, maintained by the next expansion etc. etc.
OK, the vortex would inevitably pulsate, as its temperature would change during the cycle, but the momentum of rotation should be preserved. I find the idea fascinating.
The tube on the left, sticking from the bottom of the chamber, is another of my conceits – a fueling device that is also a starting device and a tool to purge the chamber of the products of combustion. Purging is very difficult with such dead-end chambers and I think this device might help.
It is just a Bunsen burner. Crack the propane valve open, slide the masking ring off the air holes and the device will pump pre-mixed fuel-air mixture into the combustion chamber. When the chamber is full of mixture, ignite it with a spark plug. If I’m right, the engine starts. When it does, the masking ring on the fueling tube is pushed to cover the air holes and the tube starts delivering pure propane.
The masking ring can be used in conjunction with a needle valve regulating the propane flow into the jet. That way, the initial mixture prepared by the Bunsen can be very rich, so that the inflow of air through the intake proper does not make it too lean for combustion. As you snap the air holes shut, the amount of propane decreases, so that it suits the available air. (For simplicity, I have not drawn the needle valve on the sketches.) Given that propane has a fairly broad flammability range, I feel confident that this transition can be done well.
As the air sucked from the intake proper billows into the chamber in the form of a toroidal vortex, the propane shot into the center of the vortex is ideally placed to mix with the whirling air. Some fiddling with the exact relation between the Bunsen tube length and the intake path length will obviously be required to get the timing right. Ditto for the exact positioning of the inner end of the fueling tube.
Liquid fuel injection should also be possible, but without the Bunsen tube – instead, a much shorter tube with connection to a compressed air source should be used.
The Argus worked well with forced intake – after all, the company apparently wanted to power a turbine with this combustor – but I see no real reason why it shouldn’t work with normal aspiration. It looks like Argus thought so, too, as their engineers also toyed with a compressor-less version. I think it merits another look.
Here’s the look I have given to it. It is no longer quite the design the Argus engineers had in mind, I guess. Maybe I can even claim it as mine, but the Argus background is quite obviously there.
The functioning of the intake vortex chamber should be obvious. It offers a completely different impedance to incoming and outgoing flows. The direction of the vortex fights against the outgoing flow but aids incoming flow.
The interesting detail is that the direction of rotation remains the same during both intake and exhaust parts of the cycle. What has occurred to me is a bit weird – If the direction remains constant, well, perhaps a constant, ‘trapped’ vortex might actually be possible in the intake cavity. One that is set in motion by the first expansion, aided by the suction that follows it, maintained by the next expansion etc. etc.
OK, the vortex would inevitably pulsate, as its temperature would change during the cycle, but the momentum of rotation should be preserved. I find the idea fascinating.
The tube on the left, sticking from the bottom of the chamber, is another of my conceits – a fueling device that is also a starting device and a tool to purge the chamber of the products of combustion. Purging is very difficult with such dead-end chambers and I think this device might help.
It is just a Bunsen burner. Crack the propane valve open, slide the masking ring off the air holes and the device will pump pre-mixed fuel-air mixture into the combustion chamber. When the chamber is full of mixture, ignite it with a spark plug. If I’m right, the engine starts. When it does, the masking ring on the fueling tube is pushed to cover the air holes and the tube starts delivering pure propane.
The masking ring can be used in conjunction with a needle valve regulating the propane flow into the jet. That way, the initial mixture prepared by the Bunsen can be very rich, so that the inflow of air through the intake proper does not make it too lean for combustion. As you snap the air holes shut, the amount of propane decreases, so that it suits the available air. (For simplicity, I have not drawn the needle valve on the sketches.) Given that propane has a fairly broad flammability range, I feel confident that this transition can be done well.
As the air sucked from the intake proper billows into the chamber in the form of a toroidal vortex, the propane shot into the center of the vortex is ideally placed to mix with the whirling air. Some fiddling with the exact relation between the Bunsen tube length and the intake path length will obviously be required to get the timing right. Ditto for the exact positioning of the inner end of the fueling tube.
Liquid fuel injection should also be possible, but without the Bunsen tube – instead, a much shorter tube with connection to a compressed air source should be used.