The Development of Gas (CNG, LPG and H2) Engines for Buses and Trucks and their Emission and Cycle Variability Characteristics 2001-01-0144
Few diesel vehicles engines from Czech production have been converted into gas (LPG, CNG) fuelled SI engines. The higher power engines (peMAX > 1 MPa) used the concept λ »1 in turbocharging-intercooler and with oxidation catalysts mode with total (max) efficiency of about 38%. For lower power engines (peMAX < 1 MPa) the more suitable concept was using λ=1 in naturally aspirated (atmospheric) mode with 3-way catalysts. Most of the work included the development of the engines to work on Natural Gas (CNG) and LPG for buses and medium trucks. Some laboratory tests were done also with Hydrogen and Natural Gas on the laboratory single-cylinder engine.
The measurements consists of standard emissions (CO, HC, NOx, CO2, PM) but Polycycle Aromatic Hydrocarbons (PAH and their carcinogenic derivatives PAHcarc) were also investigated. Combustion stability was assessed by means of Coefficient of MIP (indicated mean effective pressure) Variation (VARpi) for lean and very lean gas fuelled engines. The effect of Rate of Heat Release on VARpi was also investigated.
Finally, the development of the combustion chamber design for a bus gas engine during a period of 7 years is shown and discussed, showing the improvements in various areas such as total efficiency, power and emissions.