In one of my old engineering books, there is described a way to augment the power of an internal combustion powerplant with a waste heat steam generator that absorbs heat from the water jacket and the exhaust. I have come to find that this principle is rather old, and works well IF implemented properly. I had considered using such a system to augment an engine by using the steam to spin up a turbo and use it to supercharge the engine itself. but the amount of boost by my calculations would make just about any petrol engine blow up from excessive manifold pressure! The resulting detonation of the mix would literally destroy the usual spark ignited engine.
Diesels are however, a different story.
But I’m thinking of a different way of combined cycling a spark ignited engine. One that requires few moving parts. The “Usual” way of combined cycle engines is to have a separate steam unit running its own generator instead of coupling to the main engine direct. although a blowdown turbine geared to the engine will combine the torque of the two engines to drive a boat or car.
I’m thinking slightly differently…
Adding mechanical componentry to an existing engine installation is difficult at best. Adding a combined cycle supercharger is much easier. The main point of adding a super or turbo is to overcome some of the “Pumping” losses associated with the host engine. polishing and porting passages gives “Free” hp boost and reducing exhaust backpressure gives yet more hp.
So… And this is where the gears got rolling in my head… Why not reduce the pumping losses to a minimum? Why not borrow an old trick from the days of the Uniflow Steam Engine, or for that matter, the modern Steam Turbine, and exhaust into a Vacuum?? A vacuum meaning… NO backpressure at all!
How do I generate my vacuum?
In a similar way that they generate the vacuum on Uniflow or Turbine engines!…With a Vortex Generator!!!!!!!! For those of you out there that may have never actually seen a vortex generator… A Vortex Generator is quite literally a specially shaped piece of pipe. It works sort-of like a venturi in a typical carburettor, but actually works on a completely different and more powerful working principle. it literally generates a “Tornado” inside of a pipe!
In fact, the pipe actually looks a lot like a tornado in shape! It is a conical section of tubing that has a tangental nozzle for a working gas to be injected at the widest part of the tube, in the centre of the head plate is another smaller conical tube that enters the centre of the primary chamber about 1/3rd of the way into the front part of the chamber. The exit of the tube is about 2 to 3 times the size of the vacuum port at the head plate. When a working gas is admitted under a mild pressure ( about 2 to 3 atmospheres) this gas rapidly expands out the conical nozzle in the side of the chamber into a circular tornado like path. Naturally, the same effect is generated that causes tornadoes to be so destructive…A VERY powerful Vacuum is generated in the Centre of the conical chamber right at the point where the entry tube in the headplate ends!
Picture this…An assembly of hardware that is about 30 centimetres in diameter and on the order of around a metre and a half in length. At the very head of this assembly is a vortex chamber with the vacuum port facing out the end. The exit of the chamber is directly into the heat exchanger tubes of a boiling chamber that looks very much like a classic horizontal firetube boiler. The vacuum port is directly connected to the exhaust manifold of the host engine by way of a short insulated tube. The Engine will start and run normally with no augmentation present or if augmentation were to fail. As the engine heats up and the exhaust gases pass into the entry tube of the vortex chamber, they pass without restriction in the usual way, other than working against atmospheric pressure and from normal friction in the pipes. They then pass completely through the Vortex Generator and out through the HX tubes and out the back of the unit in the usual exhaust way. As the water in the heat exchanger is heated up from the water jacket preheater and from the hot gases passing through the tubes, it will eventually begin to steam.
As the steam vapours begin to form, they will pass to another seperating chamber that also includes the steam nozzle regulator on the side of the vortex chamber. At this point, the steam will exit the nozzle into the primary vortex camber creating the magic tornado in the unit. As the hot gases are working through the unit, the steam pressure will ultimately reach its proper operating value and a very strong vortex and vacuum is generated by the unit which will ultimately evacuate the exhaust gases from the host engine, thereby greatly reducing its primary means of pumping loss! The net result should be a significantly measurable increase in power output without a change in power setting for the engine. The real test of a unit such as this would be to bypass the steam from the chamber and see the difference in power output with, and without the augmentation. The whole package being made so that it will look like a “Really big muffler” underneath my truck.
The exhaust pipe out the back will look like a big diesel exhaust pipe because of its unusually large size…about 8 to 10 centimetres…And will have a peculiar look with a lot of steam vapour exiting the tailpipe. I also expect that this unit will likewise be the best possible exhaust muffler because as we well know, the exhaust puffs which generate noise will be primarily exiting into a substantial vacuum, and what sound should be audible would be a gentle rushing sound from the steam vortex! Also, another secondary thing that will be required will be to have some kind of water tank installed in the vehicle for supplying the steam exhaust ejector. The beauty of such a thing would be that the internal working parts are stationary! What has really gotten me interested in this is that I have recently become aware that my truck will need a new engine or an overhaul soon, and this would be the perfect time to do this kind of experimentation with it as it is an older vehicle.
I hate to be a stick in the mud, but I’m not convinced that it’s going to work nearly as well as you hope… if at all. Correct me if I’m wrong, but isn’t the exhaust gas of most gasoline engines typically less than 125°C? (250°F) At that temperature, you’re only going to get about 16psig of steam… is that enough to run your vortex tube? (BTW: That’s not anything like a Hilsch Vortex Tube, is it?) Also, a large V8 automotive engine (300cubic inch / 5 liter?) will produce about 2.5 liters of exhaust per revolution. At 4,000 RPM (make the math easier) you’re producing 10,000 liters of exhaust per minute, or 10 cubic meters. Lesse… 1013 j/kg, 0.883 kg/m^3… that’s 8944.79 joules. Divide that over a minute’s worth of operation and you’re talking about 150 watts of usable thermal energy from the exhaust gas? Sounds like you’ll be making a rather small amount of low pressure steam, which doesn’t sound too useful for anything. These are just rough calculations (gonna be late for work now ;) ), probably faulty somewhere, but it begs the question: will it actually work?
Most engine exhaust is on the order of 350 degrees C. Or higher. have you ever seen an engine running at high power setting in the dark?? Well, You can actually see the exhaust system glow a dull red at times. And since the requirements of having a Cat (meow) installed in the exhaust system for emissions, the exhaust temperature will be higher still! and the space between the host engine and the steam ejector is the perfect place to install the catalytic converter. It is a well known fact that as much as 50% of the energy in the fuel mix goes out the exhaust as wasted heat, and if I can capture only 20% of it, that should be enough to generate a substantial vacuum. The Vortex Generator only requires about 3 to 4 Kg/Cm2 to operate (about 20 to 40 lb/sq in) pressure to operate. most of the industrial vortex gens are already operating near supersonically at 3 Kg/Cm2. They are a remarkably efficient little conical device for what they do, especially considering that they have no moving parts at all! I don’t know if this is the same as the Hilsch vortex tube, but I’m going to guess that it most likely does work on the same principle.