Fuel properties impact the engine-out emission directly. For some geographic regions where diesel engines can meet emission regulations without aftertreatment, the change of fuel properties will lead to final tailpipe emission variation. Aftertreatment systems such as Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) are required for diesel engines to meet stringent regulations. These regulations include off-road Tier 4 Final emission regulations in the USA or the corresponding Stage IV emission regulations in Europe. As an engine with an aftertreatment system, the change of fuel properties will also affect the system conversion efficiency and regeneration cycle.
Previous research works focus on prediction of engine-out emission, and many are based on chemical reactions. Due to the complex mixing, pyrolysis and reaction process in heterogeneous combustion, it is not cost-effective to find a general model to predict emission shifting due to fuel variation. Some empirical models use testing data as input to locate relationships between controlled inputs and engine response. The typical controlled inputs are Engine Control Module (ECM) parameters. These empirical models usually do not have fuel properties as an independent input, so the empirical models cannot predict the emission change when fuel properties change.
This paper investigates the effects of fuel properties on engine-out emission. The challenges of theoretic combustion calculation are discussed, as well as the root causes of emission variation. A regression model, which includes heat-release characteristics, is also presented. The increase in the fuel cetane number leads to the reduction of the ignition delay. When there is a phase change due to the ignition delay in light load operating conditions, Particulate Matter (PM) emission shows considerable variation.
The Low Pressure Bypass Waste Gate (LPBWG) turbo charger is introduced in this paper as a feasible solution for engine rating calibration. The LPBWG can adjust air flow at light load operating conditions to compensate for the change of fuel properties. With LPBWG installed on turbo chargers, a diesel engine can keep the common calibration maps when an engine runs with different fuels. This solution is particularly suitable to constant-speed diesel engines, such as an electric generation set diesel engine.