Engineers have been striving for a combustion engine that would be light, efficient and that would run off renewable fuel obtained straight
from nature. The main problem has been the manufacturing costs of renewable fuels: in one way or another, too much energy and other
expenses have often been sunk in manufacturing the fuel. Ideally, the engine would take its fuel straight from nature like a horse. This is not
achieved even by this invention, but it doesnīt fall much behind. This engine is best suited as the motive power for ships, forest harvesters,
tractors, maybe even trucks and busses as well as private cars. The modern production of liquid fuels spends too much energy and other
resources, but making charcoal or biocarbon powder we will use renewable energy sources effectively.....Peat ?..... Mine coal ?... Plane !
The production of the energy of biomass in nature is at least ten times bigger than the present oil consumption.
Perhaps we shall gather biomass and "burn" it charcoal for motors: energy willow - or sawdust? - or?
In this presentation I will try to show a possibility in which a outwardly ventilated or charged two-stroke or four-stroke diesel engine is run
by biomass, i.e. coniferous needles or charcoal. Needles have been left together with branches in forests after felling trees. In my opinion,
the present felling methods make it possible to collect the needles together with the branches for further processing. When dry, they will
fall from the branches after which they are ground. It is essential that not much energy is wasted on the grinding. We know how efficient
and actually exploding needles are as fuel. The outer layer of a needle is waxy: its thermal value is probably much higher than that of pulp in
general. Problematic is, among other things, how to feed this powdery fuel continuously at the right moment into the cylinder of an engine
so that the fuel input is never interrupted. After this needle diesel has been materialized, it will not be impossible to use any other kind of
solid biomass as engine fuel, and the resources of renewable fuels are almost limitless! Solid biomass will be refined charcoal. It is true,
that not all biomass can be utilized, nor is it useful to do so.
Perhaps following problems arise in constructing a diesel using solid fuel:
1. Feeding the fuel
2. The minor thermal value of the fuel per unit of volume
3. The heterogeneity of the fuel
4. The too slow burning of the fuel
5. Productization of new energy sources and "Peak oil"
1. Solid fuel can not be fed in the normal way; the fuel has to be transmitted with screw conveyors, some sort of Archimedean conveyors. Similar screw conveyors as used in agriculture and industri are useful in miniature, but the distances the fuel is conveyed have to be short as there is a risk of blocking the pipe. Because of the short conveying distance the fuel tank has to be placed near the engine, that is, on top of it. This again leads to a couple of problems: In cars the hood may rise too high, and the risk of fire. Neither of these problems is unconquerable. The engine has to be lowered a bit and the hood raised in order to fit the tank between the engine and the hood. At the same time, the tank is made wider and longer so that its height could be less than 20 cm. The tank could have some kind of electric fuel detector in it, a fuel gauge. The risk of fire caused by the fuel will not be that significant even though the fuel tank is above a hot engine. This is first of all due to the nature of this fuel: Solid fuel does not ignite easily when it is not floating in the air since it does not gasify significantly. Secondly, the tank is rather airtight; air circulates slowly in it, there is almost no oxygen there. For the same reason it doesn' t get easily damp even if it is damp outside. A warm engine underneath the tank contributes to the drying of the fuel, since hot gases poor in oxygen leak through the tank from the engine, and the drying contributes to the efficiency of the engine: the speed of ignition and rotation as well as power. Ventilation in the tank can be increased, if necessary, since a too airtight tank is not beneficial for drying the fuel. At this stage it is hard to say what the ideal leakage stream would be in each situation. Different positions of the filler cap may regulate the air flow. There is one more advantage when the tank is situated on top of the engine; the fact that there will be no need to shake the fuel - the slight vibration caused by the engine keeps fuel particles in move all the time so that they are continuously ready to be fed in.
2. The fuel value of needles is at the most one fourth of that of gasoline counted by weight, and counted by volume it is even less depending on how compact the fuel has been compressed. But charcoal has fuel value 70-80% of oil energy value. It is quite more than ethanol. The ethanol production spends carbon diokside into atmosphere - at least thrid of carbon. A typical car would need a fuel tank of 200-300 liters, using charcoal perhaps 100 liters. When filling up, the volume of the fuel in the tank may probably be reduced even to half of its normal volume with the help of a small jogging device. The dampness of wood is not necessarily a disadvantage. We know that by spraying water in a gasoline-powered engine its speed of rotation and efficiency rise thanks to the steam engine effect of water. The water in biomass evaporates and expands in the cylinder, and it doesn' t even need a very high temperature compared to the temperatures of gasoline engines. The engine needs less cooling, and not so much energy will be wasted while the efficiency stays high. This doesn' t mean that it would be a steam engine, the structure is still clearly that of a diesel. The engine may not need cooling at all, or ventilated cooling, which would further simplify the structure! In this case both the cylinder head and the piston crowns would be ceramic, for example of alumina. The energy for heating the car from the inside would then have to be taken from the exhaust gases. Of course, the fuel does have to be dried as dry as possible even though the final drying takes place in the fuel tank.
3. It cannot be denied that solid fuel is heterogeneous, mainly granular, and it is more likely that matter dangerous for the engine, like grains of sand, will get into the fuel. In the fuel production it is not useful to carry any energy consuming processes, such as the grinding, very far. The maximum particle size would still easily be kept such that the pipes will not get blocked and thus stop the engine. Particles of soil, like sand grains, are dangerous for the engine since they wear it fast. To prevent this the raw material has to be felled or delimbed straight onto the loading platform so that the branches will not touch the forest floor. In winter the situation is better thanks to the snow. If grass is being used equipment similar to combine harvesters or green fodder harvesters would cut the grass without letting it touch the soil. Hard grains of sand may in spite of all get into the cylinder and play havoc with it. It may be necessary to change the piston rings regularly - or to drill the cylinders after perhaps every 100000 kilometers. The fuel must clean well in production.
4. The slow combustion of the fuel keeps the speed of revolution low, but of course there are other ways to affect the revolution speed: a) particle size, b) fuel quality, c) engine temperature, d) sprinkling the fuel particles and "injection velocity". The smaller the fuel particles the faster they get oxygen and heat, and burn. Thus there is an inverse relationship between the engines speed of revolution the particle size of the fuel, whereas it is much more difficult to determine the quality of the fuel: The speed of combustion has at least to do with moisture content and ignition temperature. The fuel has to be absolutely dry. It is obvious that the temperature of the engine effects the speed of revolution. In a cylinder of a hot engine fuel burns quickly, which is also affected by the compression ratio as well as the fact whether ceramic coatings are being used on cylinders. Sprinkling the fuel is of importance because the particles have to spread quickly over the entire combustion space so that all the oxygen in it would be used fast. The air sucked into the cylinder could also rotate rapidly for the same reason. I think that by optimizing these factors we will reach a speed of revolution by two-stroke diesel compared to conventional engines of similar size.
5. Productization of new energy sources means great investments and organizations for many new industrial brances and for primary production - even as we must knit together long advantage of the oil industri. It takes time. But because demand of oil consumption oil prices will increase in the world, and the new energy sources will enter soon more attracting. The new oil deposits are in very difficult places or in severe form, such as oil sand, and production costs high. Many experts like in addition to that "Peak oil" is achieved, and the oil production will inevitably decline. I believe that the oil will be paid after five years twice as compared to the present. Biocarbon is especially ecological production, since it is also difficult to make exploitable waste. The energy content of the waste can be utilized as much as 90%, and the resulting fuel volume condenses 60-90% - estimated in Finland. The biocarbon is often washed.
In the following I try to apply the engine straight to the most difficult case, that is the engine of an automobile (tractor), in which problems are
the most pointed. The engine in question is perhaps a ventilated or a supercharged, three or five cylinder two-stroke diesel, front wheel
drive and transverse cylinder block. The fuel tank is on the cylinder block, which probably raises the hood some 10 - 20 cm, and contributes
to the fact that the riding position is more erect especially for shorter people - a bit like in cross-country vehicles. The front seat may have to
be adjusted both horizontally and vertically with adequately shaped seat cushions, and thus the height and, together with it, the cross-sectional
area would not grow significantly compared to the present private cars. It would also be possible to lay the cylinders horizontally, which
would allow the fuel tank the necessary volume, but the horizontal plane wears the lower parts of both the cylinders and the pistons, especially
if lubrication is not efficient enough.
Automobile by solid fuel
Illustration 1. Fuel tank
Illustration 2. For example: simple two-stroke engine like in ships. (Note: In illustrations 1. and 2. screw conveyors are wrong because clarity)
Since the engine is a ventilated two-stroke diesel it doesn' t necessarily need any valves. When we
leave out the valves we can lower the tank right on top of the cylinder head. Figuratively speaking
we make "holes" in the cylinder head and the tank, which makes the fuel flow from the tank into the
cylinder. Quite this easy it will, of course, not be, since we need a small piston to throw fuel into
the cylinder at the pace of the engine.
We can also say that instead of valves there is one small, hard metal edged piston in reciprocating
motion that pushes a small amount of solid fuel into the combustion chamber of the cylinder when
compression is at its hardest. Even though the shaking of the engine causes the fuel flow in a Teflon
coated aluminum tank towards the cylinder the piston alone does not secure that fuel will always get
into the cylinder. We still need coils which will shift fuel next to the piston. They also make sure
that ignition will not take place in the tank. However, the fuel will warm up before it gets into the
cylinder, maybe near 100oC, which will facilitate the ignition and burning. I like tree-sylinder motor
with 120 degrees between sylinders phase will be simple and good. The ceramic insulation inside
sylinders will increase temperature and the efficiency. The cooling/warming is normal of cars.
The power regulator will be perhaps flaps which regulate fuel streams to gear conveyors, and the
idling is when one flap be not completelly closed. Push-button and the flap closes and the engine stops.
The combustion chamber of the cylinder is made as much ball-like as possible, or actually lens-like, in order to prevent possible unburned particles from leaving before they have burnt. At the same time it will help prevent possible mineral particles from getting on the cylinder walls and wear them. Another reason is, of course, heat economical: diminishing temperature losses, which is further secured by using ceramics for the inside of the cylinder head and the piston crown, although it may be difficult to realize at the present time. The small cone under the fuel feed piston sticks out in the Illustration 2.
The purpose of the cone is to disperse the fuel dose, but it has yet another purpose. There is an electric resistor in the cone which heats the cone full-hot and whose wires furthermore hold the cone. The glowing cone ignites the dose of fuel and thus contributes to the rapid burning. It is equivalent to the glow plug used in ordinary diesel engines for starting only. We may also have to consider the possibility of using some hydrocarbon based liquid fuel, but hopefully it will not be needed.
The engine is two-stroke and supercharged, or at least outwardly ventilated, since air will otherwise not circulate. The incoming air has to be directed so that it will end up in a fast rotating movement and thus boost combustion. Since the fuel is as natural as possible and can at the most only form carbon monoxide, or probably some nitrogen oxides, we need not worry about pollution. There will be three or five cylinders in this automobile engine. It is preferable to have an uneven number of cylinders since then there will be no dead centers, the engine will turn continuously, and the torque will be maintained even at slow speeds of rotation - changing gears will not be needed that often. A small amount of cylinders means bigger sized cylinders and wider pipes, more secure fuel supply, even the grainy texture of the fuel will not matter that much. In passenger vehicles a common joint volume of cylinders is probably 1,5 - 3 liters.