CO2 reduction is increasingly becoming a focal point of international legislation. At the same time, other pollutant components such as nitrogen oxides are also targeted for reduction. Stoichiometrically operated gas engines represent an economically attractive powertrain solution compared to current commercial vehicle diesel engines. Stoichiometric combustion enables a very cost-effective exhaust aftertreatment in the form of a three-way catalyst. Furthermore, commercial vehicle gas engines emit approximately 15% less CO2 than current diesel engines due to the lower C/H ratio. This balance can be further improved by using climate-neutral gases or current key technologies.
The aim of the project is therefore to reduce knock propensity by employing valve train variability, exhaust gas recirculation, water injection, and various ignition mechanisms. This reduction in knock propensity enables operating at improved combustion phasing and higher compression ratios. Additionally, throttle losses in part-load conditions are targeted for reduction. Both measures contribute to an increase in efficiency and thus to a decrease in CO2 emissions.
For the investigations, a former commercial vehicle diesel engine with variable valve train is being converted for natural gas operation at the Institute for Internal Combustion Engines at TU Braunschweig. After comprehensive testing on a single-cylinder test bench across the entire operating map, predictive knock and combustion models can be developed. These models allow for the simulation of a full engine considering the turbocharging system. As a result, the various technologies can be evaluated individually or collectively with respect to future legislation.