c c Galang Purnomo Adi* *Physics Department of University of Brawijaya
| As the increasing technology and the world population, the need of energy keeps increasing every year. In other hand, the reserve of fossil fuels as the main source of energy today keep decreasing because of its characteristic as non-renewable energy. While fossil fuel needs a lot of time to produce, the human need of energy can not wait that long. Because of that, the energy crisis has driven many parties all over the world to do innovations in the energy field in order to overcome this issue. Meanwhile, motorcycle is one of the favorite and most preferred vehicle of Indonesian because of its efficiency compared to another fossil fueled vehicle. In connection with the energy crisis issue, that makes increasing price of gasoline as the primary fuel used in motorcycle, the need of more efficient and cleaner combustion in motorcycle engine is escalating. In the meantime, there are always some pollutant that is produced during the combustion process. One of them is the excess heat that is let out through exhaust pipe as the by product of combustion. As a matter of fact, water, that is always known can not be used as the fuel, actually has a great potential as the supplement of fossil fuel. To manipulate this potential, the excess heat produced can be used as the energy source for evaporating the water to enhance the combustion performance. Besides, the water also can also be used as
the source of hydrogen and oxygen that can be used as the additional fuel to the gasoline through a process called electrolysis. G There are two main part of the theoretical design in this paper. The first is the water steam injection into the combustion room and the second is the additional ³fuel´ produced from water electrolysis along with the hydrocarbon fuel. Generally, both parts is aimed for increasing the performance of the spark-ignition engine by decreasing the gasoline consumption and reducing the unwanted emission from the conventional combustion process. ! |£ " .1 Four Stroke Engine One of the most used engine is gasolinefueled engine that¶s also referred as sparkignition (SI) engine. Based on the number of piston strokes per combustion cycle, gasoline engine is divided into two-stroke engine and four strike engine. In four-stroke engine, there are four phases or strokes to do in order to complete one cycle of combustion, they are intake, compression, expansion, and exhaust as can be seen in the picture 1. Two of them are downward (intake and expansion) and the other two are upward (compression and exhaust). A cycle is completed as the crankshaft makes two revolutions. The valves in the combustion room open and
close for routing gas in and out of the chamber. The first phase is for the intake valve to open during the intake stroke by the piston in order to draw the mixture of fuel and air into the chamber while the exhaust valve is closed. In this stage, the piston move downward from top dead center (TDC) to bottom dead center (BDC) for creating a room for the fuel and air to get into the combustion chamber. The second phase is called compression stroke. This time, the intake valve closes and the momentum of the crankshaft generated by the downward-moving piston allows the piston to move up from BDC to TDC. It creates a compression to the fuel and air mixture. As the piston gets near to the TDC and at the end of compression stroke, the spark plug ignites the mixture that causes them to burn. The third phase is the downward movement of the piston caused by the increasing pressure and temperature by the burned fuel and air mixture or called as expansion stroke. Then the kicking piston will again move the crankshaft half revolution and place itself into BTC. At the fourth phase, the exhaust valve opens and the piston move up in the similar way as the first phase, and push out the exhaust gases out of the chamber.
Picture 1. Four-stroke engine cycle
.2 Water Electrolysis Electrolysis is a process which is use electrical energy to drive a non-spontaneous chemical reaction to arise. It is used for obtaining the elements that are chemically too reactive to found in nature. In this case, electrolysis is used to obtain hydrogen (H2) and oxygen (O2) from water. There are two reaction involve in the process. First is a reduction that occur in the cathode. Reduction will occur at the cathode. At this electrode, hydrogen gas and hydroxide ions are produced. While, the electrons required for this reduction will come from the power source of electric. The reaction can be seen as below: 4H2O + 4e- ĺ 2H2 + 4OHAt the anode, an oxidation will occur producing oxygen gas and hydrogen ions. The electrons produced will return to the power source with reaction of: 4H2O ĺ O2 + 4H+ + 4eAdding both reactions we will have 6H2O ĺ 2H2 + O2 + 4H+ + 4OH6H2O ĺ 2H2 + O2 + 4H2O 2H2O(l) ĺ 2H2(g) + O2(g) . Water Injection According to Labonte, water Injection was first successfully implemented in WWII on the P-47 ³Thunderbolt´. The Turbo Charged Pratt & Whitney R-2800 engine normally produced 2000 HP, but with water injection the power raising up to 800 HP and also had 20 minutes high power output during combat. One of the advantages using water injection into combustion room is the cooling of intake air in the first phase. By cooling the intake air, more oxygen molecules enter the cylinder through a
denser air charge. The additional oxygen from the intake air help the combustion process become more efficient because it will make the combustion of fuel more complete. The other benefit is the water steam adds the density in the combustion room that it will give extra force to the piston during the expansion stroke and will give more torque to the crankshaft. Russian researches, Satpov and Lusho, have reported the effects of water presence in fuel on spark-ignition engines. They indicated that the NOx content in exhaust gas dropped by 1. % for 1% addition of water to emulsified fuel. r # $ " % According to the second law of thermodynamic, there is no engine that can convert all the heat produce into work, and so do the engine of the motorcycle. It will always generate heat even though it is an unwanted phenomenon. So, in order to minimize the energy loss, the excess heat can be used in other way that will also boost the SI engine performance. By utilizing the excess heat, we can create dry water steam that will be injected into combustion engine. There is a water tank and is channeled into the water steamer that uses the heat from exhaust pipe that has average temperature of 0oC. From the steamer, the steam will be channeled into manifold before entering the combustion chamber. In order to keep the temperature relatively constant either in the way to the manifold or to give resistance to the environment temperature change, a system has to be made. The steamer is painted black on the innermost plate so that the heat will
be absorbed by the black side and will be radiated back into the steamer room referring to the black radiation theory. There is a room between the innermost and outermost plate of the steamer with the intention of utilizing green house effect. The radiated heat from the black-painted inner steamer will be trapped by the reflecting side of the outer plate with the outer plate¶s color remains as it is (metal color) so that the temperature from the environment will not become a bother and it acts as an insulator. And by channeling the steam into the manifold with the shortest path, it is hoped that the steam will stay as it was in the steamer. The reason utilizing the dry steam injection instead of water injection into the combustion chamber is to ensure that there will be no water accumulation in the combustion chamber that will corrode it. The electrolysis process will take place in the electrolysis chamber with electrode made from stainless steel for preventing it from corroding by the contact with the water and connected to the electric source from the accumulator. The resulting hydrogen and oxygen gases will be contained in a temporary reservoir before channeled into the combustion room in order to control the amount of the gases injected. In the combustion room the fuel, air, dry steam, hydrogen, and oxygen will meet together. In the first stroke, the intake valve opens and the entering steam will add the density that will give extra pressure to the piston plus it will absorb the heat in the chamber so that it will reduce the production of Nox gas. While, the additional oxygen will make the fuel combustion process become more
complete and result in the cleaner combustion. The hydrogen produced from the electrolysis process has the wide range of flammability, and as a result hydrogen can be used in a wide range of hydrogen-airgasoline mixture. Another advantage is hydrogen can be used in a lean mixture where the fuel amount needed is less than theory. The flame velocity of hydrogen is much faster than other fuels allowing oxidation with less heat transfer to the surroundings. This improves thermal efficiencies. Efficiencies are also improved because hydrogen has a very small gap quenching distance allowing fuel to burn more completely. The only drawback to hydrogen is that even though its lower heat value is greater than other hydrocarbon fuels it is less dense therefore a volume of hydrogen contains less energy [4]. In order to cover the drawback, steam injection is induced so that the temperature will become lower and add the overall density. X The motorcycle engine efficiency can be increased through the injection of water steam and oxygen and hydrogen gases
produced from electrolysis. The water steam will add the density and give extra force while oxygen will help the combustion process raising up and the hydrogen will act as a supplement to the gasoline due to its wide range of flammability and can be used in lean mixture. Anonymous. 20006. Electrochemistry, Electrolysis of Water. www.saskschools.ca/curr_content/chem 0_0 /6.../ .pdf| Labonte ,Daniel J. Water Methanol Injection on Diesel Engines for Combustion Cooling and Enhanced Engine Performance. USA. Lanzafame , R. 1999. Water Injection Effects In A Single-Cylinder CFR Engine. SAE International Congress and Exposition, Detroit: USA. Wall, Jacob. Effect of Hydrogen Enriched Hydrocarbon Combustion on Emissions and Performance. Department of Biological and Agricultural Engineering: University of Idaho.
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by Galang Purnomo Adi 081090002
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