Ultra-low NOx Technologies for Heavy-Duty Applications with reduced Total Cost of Ownership

The utilization of gasoline engines in heavy-duty vehicles for the purpose of continental transportation is in direct competition with conventional diesel engines. It’s imperative that the operating performance of the gasoline engine is equivalent to the diesel engine, and that the gasoline engine shows efficiency benefit to both cost segments, the product manufacturing costs) and total cost of ownership (TCO). The 11.6-liter gasoline engine developed has been designed and applicated in such a way that it operates at a stoichiometric combustion air ratio (lambda = 1) across the entire engine map range without exception. In combination with external exhaust gas recirculation (EGR) this strategy does not result in a substantial decrease in the absolute NOx concentration in raw emissions compared to the diesel engine with 15.0-liter displacement, but it facilitates the cost-efficient utilization of the three-way catalyzer as the main exhaust aftertreatment system, thereby reducing NOx emissions to the detection limit. This reduction is necessary for adherence to the stringent future emission standards for heavy trucks that are being established by the U.S. regulatory authorities (EPA; CARB) for model years commencing in 2027. In addition to the stoichiometric operating strategy, the engine features an innovative combustion chamber geometry, including a high compression ratio, high EGR compatibility within the real engine operating range, and an optimized crankshaft drive. This already tested technology package is now being applied to heavy-duty engines, proving its scalability and effectiveness. Its application to heavy-duty engines not only promises significant production cost savings but also ensures compliance with future emission regulations. By integrating high EGR rates and high compression ratio, the engine achieves optimal combustion efficiency, thereby minimizing emissions without compromising performance. The engine efficiency is demonstrated by its brake thermal efficiency of 43.1% and an extended map range with a specific consumption of less than 200 g/kWh. In a real heavy-duty driving cycle, the average consumption is 228 g/kWh (vs. 217.5 g/kWh), resulting in a significant reduction in total operating costs on the American market using gasoline as fuel. The paper provides an overview of the mechanical and thermodynamic engine design and shows the stationary engine map and dynamic performance in a real driving cycle of heavy-duty transport. Furthermore, a comprehensive cost analysis is included to compare the TCO of the new engine with those of a conventional diesel engine.