Due to agricultural engines’ high average workload and operation in rural areas, substituting internal combustion engines in non-road sector is still a challenge. Utilizing sustainable solutions are therefore in key position for decarbonizing the non-road sector. To this day, the diesel engines dominate the markets because of their high efficiency. However, the simplicity and cost effectiveness of the spark-ignited engines together with renewable fuels are suggested to bring several advantages compared to the diesel engine. E.g. ethanol and bio methane are relatively simple to produce from agricultural residuals and wastes, and the raw materials are easily available around the world. Additionally, stoichiometric engines would only require a three-way catalyst (TWC) to fulfil Stage V emission regulations. A bi-fuel (BF) and dual-fuel (DF) engine operating on both ethanol and biogas could potentially offer a flexible option for e.g. farmers, as they could produce the fuels locally and simultaneously increase the sources of income.
The largest technical challenges concerning spark-ignited (SI) engines compared to its diesel counterparts are mainly related to lower engine efficiency. Furthermore, the differences in SI fuels characteristics set limitations on regular SI engines for flexible fuel operation. The main focus of this paper was therefore to study possible methods for developing a flexible spark-ignited non-road engine fulfilling Stage V emission requirements. The studied test engine was a port fuel injected (PFI) SI-conversion based on a commonly used non-road diesel engine for agricultural applications. The engine was equipped with two injectors per cylinder, one directed into the swirl port, the other to the tangential flow port. Additionally, a single gas injection mixer was added to distribute gaseous fuel for all cylinders at once. Four different injection methods were studied: Single liquid fuel injection separately in both swirl and tangential ports, dual port liquid injection and dual-fuel mode, utilizing simultaneously ethanol and methane. The results are compared against Stage V requirements.