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Compressed Biogas Motorcycle

Nguyen Van Dong


           The use ofrenewable fuels to replace fossil fuels is the inevitable trend of human civilization because fossil fuels will dwindle down, affecting every economy worldwide. Use of biogas as a fuel for internal combustion engines is one of the raisonable solutions to develop renewable energy in Vietnam where up to 80% of the population live in rural areas. Using biogas will be more meaningful if it can be supplied as fuel of motorcycles, the most popular individual transport in our country today.
           This subject of the research contributes handle 2 important issues to be able to use biogas as a fuel for motorcycles, which are (1) compression biogas into high pressure vessels and (2) provide compressed biogas for motorcycle ensure optimal operation in all operating conditions.
             The research allow us to draw the following conclusions:
            The filter impurities in biogas depends on the size and requirements of gaseous fuel use purposes. For small-scale station, we can use NaOH solution to eliminate H2S and CO2. CH4 concentrations can raise up to 96.7% CH4. For large biogas stations, we can combine by eliminating H2S adsorption method and CO2 removal method by high pressure..

Biogas filtration by chemical solution                        Pro II Model of calculation CO2 condensation

            Compressed biogas supply system for motorcycles including high pressure cylinders, pressure relief valves, mixture preparation device. It is possible to use compressed natural gas cylinders capacity of 5 liters, up to 200 bar pressure to store the motorcycle biogas fuel. On the other hand we can modify 3-functional valve LPG kit for motorcycle: idle valve, main gas supply valve and acceleration valve to provide compressed biogas for motorcycles. Experimental results show that using 2 cylinders of  5 liters of each containing biogas with 90% CH4 at a pressure of 75 bar, the motorcycle can run independently 20km with average speed 40km/h..

3-functional valve system for compressed biogas motorcycle         Testing compressed biogas motorcycle

             Burning velocity of biogas is lower than that of traditional liquid fuels. So when motorcycle runs on compressed biogas, the advance spark timing angle should be increased, particularly when the engine run at high speeds. The advance spark timing is larger if biogas is poorer. The results of the research shows that when the engine running with biogas containing 90% CH4 at the speed of 3000 rpm, the optimum advance spark timing angle is 34 degrees.

Simulation of combustion of biogas-air mixture in motorcycle

             When running on compressed biogas, maximum indicating pressure as well as indicating work of the cycle are lower than that when running on petrol. Experiments show that when the engine running with petrol RON92 fuel, the maximum indicating pressure is about 58 bar at 10 degrees after top dead center and the indicating work of cycle is 106.369 J/cyc; whereas when it running on biogas with 85% CH4, maximum indicating pressure is about 34.5 bar, at 19 degrees after top dead center and the indicating work of cycle is 75.842 J/cyc, i.e about 71.3% compared to petrol RON92.

Comparison of pressure and cycle work of engine running on petrol and on biogas

           The laminar burning speed of biogas-air mixture can be calculated using the empirical formula. When calculating combustion in combustion chamber of the Wave α 110cc motorcycle running on compressed, turbulent coefficient combustion speed by 1.3 can be choosen for fuel containing 80% CH4 as the engine runs within speed in range of 3000 rpm to 6000 rpm. With this coefficient, the results given by FLUENT simulation are in accordance with experimental results given by AVL motorcycle dynamometer testing.

Comparison of results given by simulation and by experiment