Invented and developed by Tapani Hakonen __________
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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 production of the energy of biomass is ten times bigger than the present oil consumption. Energy sources
Perhaps we shall grow Reed canary grass (Phalaris arundinacea) and "burn" it charcoal for motors. Plane !
In this presentation I will try to show a possibility in which a outwardly ventilated or charged two-stroke (or perhaps four-stroke) diesel engine is run by biomass, i.e. coniferous needles. 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 biomass as engine fuel, and the resources of renewable fuels are almost limitless! It is true, that not all biomass can be utilized, nor is it useful to do so.
The 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 and the particles grinding the cylinder
4. The too slow burning of the fuel
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 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 10 inches. 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. A typical car would need a fuel tank of 300 liters (65 gal. / 80 US gal.). 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, 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 every 100000 kilometers (60000 miles).
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 smaller by half compared to conventional engines of similar size.
In the following I try to apply the engine straight to the most difficult case, that is the engine of an automobile, 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 20 cm (8 in), 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.
Illustration 1
Since the engine is either a ventilated or supercharged 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 even up to 100 o C (200 o F) or much more, which will facilitate the ignition and burning.
Illustration 2
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 (which can not be seen properly in Illustration 2). 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 2-3 liters (4-5 pt, 4-6 US liq pt).
Illustration 3
Fill-up: The fuel tank and the filler hole are on the engine, and fuel is fed into the tank from a silo at a filling station through a pipe in which a flow indicator is attached for invoicing. The fuel can explode, if it is too dry. Sometimes fuel must perhaps dampened. A local farmer, for example, could fill the silo with fuel that meets certain norms. The silo and the pipe are shaken a bit to ensure unobstructed flow. Especially shaking the end of the pipe also compresses slightly the fuel in the tank. When the end of the pipe is detached from the car it is closed by a shutter (iris shutter), and vice versa when it is attached to the tank again - the pipe is opened and the shaking begins (ca. 10 Hz). Another spare shutter is at the joint between the silo and the pipe, it could operate automatically - being manually operated and dependent on the shaking. Filling up should be as easy as with gasoline. It is important to shake the fuel tank especially when filling it up, since that way the fuel can be compressed to half of its normal volume, and it is further boosted by the pressure from the silo, when correspondingly the driving distance would be doubled. The wide range in the fuel amount, even up to 100 kg (200 lb.), unfortunately affects the handling characteristics of the car. Nitrogen gas will save car burn down.
A turbocharger or a blower fan forces fresh air into the cylinder while the piston sinks so down that the air inlet opens. The cylinder is filled with oxygen-rich air, and as the piston starts rising this air is squeezed together which makes it become hot. At the same time the fuel feed piston thrusts into the cylinder a small dose of solid fuel which, if it hasnīt ignited earlier, ignites when it meets the glowing ignition cone. The ignition cone hurls the burning particles around the cylinder as evenly as possible so that the oxygen in the cylinder is used efficiently. The circulating air mass increases the efficiency even further. The gas heats up as pressure rises rapidly, which pushes the piston down and works at the same time. The gases flow out when the piston goes so down that the outlet opens. The outgoing gases run a turbocharger or something similar. If there are any particles not burn left from the previous round, they can burn at the top dead center of the next stroke, but of course some unburned matter may also leave the cylinder - however, efforts are made to prevent it by shaping the cylinder. Efficiency can be adjusted by adjusting the stroke length of the fuel feed piston - i.e. by adjusting the fuel amount. Small gear conveyors bring continuously fuel into the cylinder hole of the fuel feed piston, even though the engine vibration causes the fuel slide towards the feed piston. They will also reduce the risk of fires, even though they may leek some gases low in oxygen in the fuel tank. Will some kind of back-pressure valve be needed to lower the possible excess pressure in the fuel tank? The ignition cone is heated before starting the engine, just like in most modern diesel engines, but the incandescence will probably be continued even after starting, maybe even all the time. When applying an engine of an automobile the best geometry is achieved by a transverse three cylinder inline engine on which, partly around which, the fuel tank rests. The fuel tank has to be made as big as possible since, although the fuel is vibrated when filling in, there is never too much fuel considering the traveling distances. A good target would be 500 km (300 mile) with normal speed. During repairs the tank has to be detachable and it probably has to be emptied then, but it might also be possible to design the tank so that it will not have to be emptied. The cover of the fuel tank can be lift. Minor repairs are carried out from the front of the engine where they have been concentrated. The engine can be very simple. If the cylinders are charged there will have to be valves at least in the suction face, which will make it possible to increase pressure in the cylinders and the engine efficiency.
In trucks and freight trucks the fuel tank can be placed behind the cab, maybe even under the platform. From there gear conveyors push fuel to an "intermediate tank" over the engine, from which the feeding pistons push it to the cylinders. The fuel tanks of busses are under their cabins, which of course reduces the space left for the luggage. As with the trucks, gear conveyors move fuel to the intermediate tank over the engine from where it goes to the cylinders. If no fuel comes to the intermediate tank an alarm will inform about it. The size of this intermediate tank could be say 200 liters. Ships will have the intermediate tank above cylinders too.
A combustion engine that uses solid fuel will probably not for a long time gain any notable foothold among other engines. The fact that oil based engines have been developed for decades, the fairly low oil price and the developed oil refining technology and marketing techniques all will see to it. However, there will be a time one day when the oil resources have been used up and the oil price will start rising rapidly. For that moment we have to have a new technique by and large ready which will step forward and substitute all mineral oil based fuels at a reasonable price. A new technique is also demanded by the ever growing environmental movement that demands renewable, sulfur free fuels without any heavy metals. The long transportation distances are a considerable risk to the delivery of oil under exceptional circumstances. Renewability also includes fighting global warming, since if millions of people start demanding cars the oil consumption skyrockets while the amount of carbon dioxide in the atmosphere increases. The maximum temperature of an engine using solid fuel is perhaps lower than that of a petrol car, so this engine will not give off that much nitrogen either. This engine may produce carbon monoxide and dust as well as noise. Even the smell that it generates is different from that of petrol. Because of the ashes that are produced the muffler has to be different - otherwise the ashes may block the exhaust pipe.
Illustration 4
Or the ashes could be collected in some kind of tank, which would also muffle the noise, and which the ash is from time to time sucked to the container of the service station and used to be a fertiliser. The ashes are also to be collected to prevent health hazards, since floating in the air it can cause asthma or lung cancer. Gathering the ashes is not necessary on the countryside farm work. However, the engine must not scatter hot flakes. The collector of micro particles must be connected behind the ash vessel because of new norms. The collector is cleaned in a maintenance.
I am rather concerned about the dependability of this engine; it should work smoothly and reliably. A suitable liquid fuel could help partly by being switched on in case of functional trouble, especially as the troubles are mostly momentary. These troubles are caused by badly ground and wet fuel and impurities - i.e. bad quality fuel. A guarantee must be demanded from the fuel deliverers and random tests have to be made. Particularly wholesale trade of fuel must guaranteed with sertifications. If a petrol based fuel has to be used for a longer period of time the cylinder has to be cooled more efficiently, for example, by a thermostat regulated water spraying system. However, it is my firm belief that oil based fuels will not be needed.
If there will be two cars in the family in the future, so the other is perhaps a countryside car, bigger and uses biomass (charcoal) as its fuel, and the other is a town car and a smaller one will go mainly on the solar electricity. =>Appendix J
The energy costs of a fuel are an important factor. I don' t think it is useful to grind wood powder from heavy timber since grinding consumes a lot of energy and the material is too expensive, whereas sawdust as a side product could be useful. Making needles and bark into powder demands much less energy. Thick bark of pine is very soft to grind. Energy willow, reed grass, the refuse from thinning forests could be economical, charcoal of stumps and lignin of pulp mill - in southern areas sugarcane and water hyacinth.
Suitable vegetable matter like algae could probably be collected from sees by some kind of net system at low cost by ship like a whale. The ship gathers alga by the tight net. The nets like conveyor belts transfer the alga to a reservoir from sides of the ship.
In the future dry grass will make good fuel, if only a suitable low energy grinding technique is invented. Grass will probably have to be ground as fresh and half grown as possible as cellulose fibers are at the weakest then and demand less grinding energy. Grass would be gathered many times a summer like green fodder, it would be ground and screened immediately. When a fertilized, irrigated lawn is mown at short intervals it produces a very bumper crop. According to researchers the annual harvest of fresh grass can be up to 70 ton/hectare, normally only 7 ton/hectare?
Very productive and humble energy plants are Phalaris arundinacea (Finnish ruokohelpi: 10 ton/hectare/y) and Centaurea jacea (Finnish ahdekaunokki: 20 ton/hectare/y). The plants dry out in the winter and can be harvested in late winter. There is an easy method to make pure amorphous coal for cars.
The straw that combined harvesters make could also be cut up, ground and sacked in the harvester. Newsprint can presumably be ground into a powdery fuel at low cost, but at the same time one has to be extremely careful that no plastic enters the fuel, since in the fuel tank it would melt and probably block the holes to the cylinders. Resin might also be damaging. Peat is also a good source of energy which doesn't need much grinding, but its disadvantage is the mineral soil it may contain. Ecological of peat depends on ditshing of marsh. If the ditshing has be made earlier e.g. twenty years ago then the peat must be used, because carbon dioxide and methane escape out off marsh. As the carbon dioxide situation today is it, only renewable fuels should be used without lowering the food production..
Mineral coal is bad solution for climate, but the energy produced by the charcoal can be almost (pure CO2) as clean as electric energy, and charcoal demands less grinding energy. Check the ratio C12/C14 if necessary in laboratory !
There is a big difference between old coal and
new coal.
Why should the eco-diesel be designed and realized? It is about time to design substitute structures because:
1. The oil reserves of the world are slowly
being exhausted and it will be all the more difficult to get oil.
There is not enough oil for us and for the fast
developing countries like China and India.
2. Furthermore, the oil reserves are heavily concentrated in only few areas of
the world,
which tends to cause various availability and price crises.
3. Sulfur, nitrogen and, most of all,
carbon dioxide emissions destroy our planet before long
and cause both predictable and unpredictable natural
catastrophes.
4. If oil runs out suddenly and we have not been prepared for it, then the collapse of the economy :
hunger,
riots, wars follow - perhaps the collapse of the civilisation and many people will die.
Tapani Hakonen
