First experimental investigation of high pressure methanol cavitating flow characteristics in quasi two-dimensional nozzles

The global shift toward low-carbon solutions is driving the transition from fossil fuels to carbon-neutral fuels in engine applications. Methanol is gaining attention as a promising alternative due to its clean combustion and potential for reducing greenhouse gas emissions. High-pressure direct injection of methanol can reduce emissions and improve fuel efficiency, making it a viable solution for sustainable energy. However, the flow characteristics of methanol in injector nozzles are not well understood due to its unique physical properties compared to diesel and gasoline. The lack of experimental data limits precise control of injection rates and spray patterns. This study presents the first experimental analysis of high-pressure methanol flow in a quasi two-dimensional optical nozzle. An experimental platform was developed to control injection pressures from 1 to 10 MPa and back pressures from 0.1 to 4 MPa with ±1 % accuracy. Flow characteristics are studied under various pressures and temperatures, providing high-precision data for model validation. Comparative experiments were conducted to analyze the flow characteristics of methanol and diesel, providing insights for replacing diesel with methanol in engines. Results show that methanol has a higher discharge coefficient than diesel at higher cavitation numbers due to its lower viscosity, but a lower discharge coefficient at lower cavitation numbers due to stronger cavitation. Finally, a rounded-corner nozzle is introduced to reduce cavitation at the orifice entrance, confirming the role of back suction of the cavitation region in the exit shear layer in promoting the growth of the cavitation region inside the orifice.