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Renewed interest in a gas turbine as an alternative driveline for heavy trucks within Volvo, driven by the demands for lower emissions, resulted in a pre-study during 1990-1992 and the development and testing of a demonstrator engine between 1993 and 2000. To achieve the demanding goals for efficiency and emissions, the engine was designed as a recuperated and intercooled two shaft powerplant with a low-emission combustor. Following a comprehensive aerodynamic and concept study, engine components were rig tested and the engine mechanical design was finalized. Two engines were built and tested in a rig and in a truck. Very low exhaust emissions were demonstrated during rig testing, with NOx as low as 0,22 g/kWh in a 13-mode test. The efficiency goal of 42 % was not reached, but given more development time the measured efficiency of 38,6 % can most certainly be improved. Still, it will be the fuel consumption that is the major disadvantage compared to a diesel engine.

In the study reported here the combustion and emission characteristics of a heavy duty six-cylinder diesel engine fuelled with dimethyl ether (DME) of chemical grade and DME with small and varying amounts of methanol and/or water were experimentally investigated. In addition, the size distribution of emitted particles and selected unregulated emissions were sampled. Methanol and water additions had a very limited effect on emissions, but affected the combustion processes in a way that accentuated the premixed combustion and thus caused more energy to be released early in the cycle. At high load, however, the effect was reversed, due to the lack of distinct premixed combustion. The results confirm that DME combustion does not generate any accumulation mode particles. The particles that are detected are smaller than the soot size range and do not occur in greater numbers than those from a diesel engine in the corresponding size range.

Combustion characteristics of dimethyl ether, DME, have been investigated experimentally, in a heavy duty single cylinder engine equipped with an adapted common rail fuel injection system, and the effects of varying injection timing, rail pressure and exhaust gas recirculation on the combustion and emission parameters. The results show that DME combustion does not produce soot and with the use of exhaust gas recirculation NOX emissions can also be reduced to very low levels. However, high injection pressure and/or a DME adopted combustion system is required to improve the mixing process and thus reduce the combustion duration and carbon monoxide emissions.