Samenvatting

Awareness of climate change and stricter emission regulations have accelerated the search for sustainable energy solutions. A central goal is carbon-neutral energy use, minimizing greenhouse gas emissions while ensuring reliable energy supply. In applications with limited grid access—such as festivals, shipping, or mobile workstations—internal combustion engine (ICE) generators remain vital due to their high power density, operational simplicity, and low costs. To improve environmental performance, renewable fuels like methanol (CH₃OH) can partially replace diesel. This project investigates converting Stage III diesel generators into diesel-methanol dual-fuel (DMDF) systems to comply with Stage V emission standards, focusing on methanol injection timing, air intake temperature, and Methanol Energy Fraction (MEF).

A literature review revealed that intake air temperature (IAT) strongly affects combustion: lower temperatures increase ignition delay and reduce peak cylinder pressure, while higher temperatures enhance combustion efficiency but raise NOx emissions. Methanol’s high latent heat, high octane, and low cetane numbers make it suitable as a secondary fuel, reducing particulate matter (PM) and enabling leaner combustion, though it may increase unburned hydrocarbons (HC), CO, and formaldehyde, especially at higher MEF or low loads. Methanol’s cooling effect delays diesel ignition, affecting knock. Injection timing and valve overlap are critical: early methanol injection improves evaporation and reduces knock, whereas late injection can increase HC/CO emissions. Multi-Point Sequential Injection (MPI-S) provides a practical retrofit for Stage III engines. Aftertreatment systems—Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF), and Selective Catalytic Reduction (SCR)—remain essential to meet Stage V standards, as dual-fuel conversion alone is insufficient.

This study focuses on a John Deere 4045 HFG82 diesel engine, a 4.5 L, 4-cylinder, direct-injection unit rated at 103 kW. Modifications for dual-fuel operation included installing a methanol fuel rail, reinforced brackets, a modified cylinder head, and a bypass valve to control IAT. Measurements included mass airflow, intake air temperature, exhaust gas temperature, in-cylinder pressure, smoke, and exhaust composition (CO, CO₂, NOx, HC, PM), along with crankshaft speed, fuel flow, and power. Data were processed in Matlab to evaluate efficiency, MEF, and emissions.

Tests varied IAT (30–70 °C), methanol injection timing (early, middle, late) based on TDC, and MEF (10–50 %), with baseline diesel-only measurements for calibration. Efficiency was calculated from output power relative to total fuel energy, and emissions were expressed in g/kWh for comparison with Stage III and V standards.
Results showed that IAT, Methanol Injection Timing (MIT), and MEF significantly influence combustion, efficiency, and emissions. Higher IAT improved methanol vaporization, combustion, and reduced HC/CO, but increased NOx. Efficiency increased at low loads but slightly decreased at medium loads due to changes in air density and oxygen availability. MIT effects were minor in the tested range, though extreme timings caused knock and unstable combustion. Higher MEF reduced NOx and PM emissions, but could increase HC and CO at low IAT due to incomplete methanol combustion. Methanol combustion also produced formaldehyde, requiring monitoring. These findings provide insights for optimizing dual-fuel engine operation to meet emission standards while maintaining performance.