engleski

OPERATING PARAMETERS OF THE BIOGAS-DIESEL DUAL- FUEL ENGINE

In order to reduce air pollution from internal combustion (IC) engines, new types of combustion processes are constantly developed. One of these processes is named dual-fuel (DF) where small amount of diesel ignites the primary fuel. If this primary fuel is produced from renewable energy sources, such as biogas which consist mostly of methane (CH4) and carbon dioxide (CO2), benefits to the environment protection are even higher. An additional benefit of a dual-fuel engine is lower CO2 emissions and lower fuel costs with main disadvantage presented as the increase in carbon monoxide (CO) and hydrocarbon (HC) emissions. On the other side, the main disadvantage of the biogas as the IC engine fuel is relatively high auto ignition temperature, especially when its CO2 ratio is increased. To enable research of these new combustion processes and usage of alternative fuels an experimental setup for IC engine testing is developed in the Laboratory for IC Engines and Motor Vehicles of the Faculty of Mechanical Engineering and Naval Architecture in Zagreb. Core of the setup is experimental engine made by modification of single cylinder diesel engine Hatz 1D81Z. After required modifications the experimental engine can operate in spark ignition (SI), compression ignition (CI), homogeneous charge compression ignition (HCCI) and in dual-fuel mode of operation. Diesel fuel is injected in the cylinder using fully flexible common rail system while biogas is injected into the intake manifold. Biogas is premixed in two different volumetric ratios of CH4 and CO2. First bland is in ratio CH4:CO2 = 80:20 and second one is in ratio CH4:CO2 =60:40. Both blends are stored in pressurized cylinder tanks. The goal of this research is to determine the influence of different biogas composition, (different ratio of CH4 and CO2) used as a primary fuel in the dual-fuel mode of operation, on the performance of the same engine at similar operating conditions. Similar operating conditions mean that the engine tests were performed at the same indicated mean effective pressure (IMEP) in all ratios of biogas composition at the same engine speed. Engine speed in this research is set to 1600 rpm. Predefined IMEP level is measured in DF mode of operation with pure methane as primary fuel. Each of the comparative operating points is optimized to satisfy the limits for coefficient of variation of IMEP (CoV IMEP), maximum pressure rise rate (MPPR) and to obtain the highest engine efficiency. A result of this research presents a comparison of in-cylinder pressure, temperature, rate of heat release, indicated efficiency and maximum pressure rise rate obtained in DF mode with different biogas composition as primary fuel. Also, this research presents a comparison of the emissions levels of HC, CO, CO2 and NOX.

dual fuel engine, biogas, experimental engine testing

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