Through combined modeling and experiments, Marchese and his research team uncovered a new regime of engine knock observed in dual-fuel engines, which is different from the knock observed in spark-ignited engines. “Specifically, we observed detonation of the natural gas/air mixtures in regions between the individual diesel spray jets,” he states. “This was a surprise and suggests there may be ways to minimize knock in dual-fuel engines by designing the diesel injectors in a different way.”