50% Efficiency on a Combustion Engine - Status and Measurement Results

Due to the work carried out by AVL, possible concepts for achieving a brake thermal efficiency of 50% on a 13-liter class Diesel engine for a Heavy-Duty on-road commercial vehicle can be presented in this paper. Based on the latest developments of exhaust aftertreatment systems, higher engine raw NOx emission concepts appear to be a feasible approach for maintaining a relatively simple engine layout. Following such an approach, two possible engine concepts are presented as result of AVLs investigation:Concept 1 is essentially a currently available EGR engine layout with cooled, highpressure EGR and reed valves. Due to the limitation of EGR, "moderate” engine out NOx levels can be achieved with this concept.In Concept 2, with "high” engine out NOx, no EGR is applied in a wide engine map zone. The turbocharger selection is conducted independently of EGR path requirements. Hence, additional fuel economy benefits can be achieved and a more moderate peak cylinder pressure level than for Concept 1 is required. Due to the lack of EGR at full load, all necessary and further NOx reduction needs to be achieved by the EAS system. For all operation points, where EGR delivery is possible (e.g. low engine load, high engine speed), cooled high pressure EGR can still be applied and consequently the urea consumption can be improved under real driving conditions.Engine tests have been conducted and prove that highest BTE can be achieved, if highest turbocharger efficiencies, an optimized combustion system and low engine friction concepts are applied.