Gas engines are frequently used as generators in modern combined heat and power plants (CHPs). Until now, these engines have generally been able to comply with nitrous oxide emission limits while at the same time offering a high level of efficiency by operating in lean-burn mode, which results in excess air during combustion. However, if this process will be subject to stricter limit values the future, using engines without charging will have the effect of reducing the efficiency. Stoichiometric combustion is one alternative: a stoichiometric air-fuel ratio involves only enough air required for the combustion of the fuel and no more, allowing for the use of a three-way catalytic converter and thus, in general, extremely low exhaust emissions. As part of a DBU-funded project, the Karlsruhe University of Applied Sciences combined this operating mode with exhaust gas recirculation, speed reduction, a high geometrical compression ratio and enhanced expansion in order to increase the efficiency. Compared to learn-burn mode, this innovative new process would make it possible to comply with future nitrous oxide limit values while at the same time increasing efficiency and reducing system complexity.
DBU-AZ 32875
