Experimental investigation of high-pressure methanol spray characteristics for engines

Methanol high-pressure direct injection (HPDI) engines are a promising low-carbon solution for heavy-duty applications. Multi-dimensional computational fluid dynamics (CFD) simulations play a crucial role in the design and optimization of these engines. However, the distinct physical properties of methanol, compared to diesel, lead to significant differences in spray behavior, including atomization and development, raising doubts about the applicability of diesel spray models to methanol. While most existing studies focus on low-pressure low-reactivity methanol spray or diesel-like high-reactivity fuel spray behavior, there is a lack of spray data for methanol HPDI, leaving the question of whether diesel-based models are suitable for methanol unresolved. To address this gap, this study investigates the spray characteristics of methanol in a constant volume combustion chamber using Schlieren imaging to measure key spray parameters. Spray penetration length, spray cone angle, and other characteristics were systematically examined with the varying injection pressures of 30-90 MPa over the ambient temperature range of 300-500 K at ambient pressures of 0.5 and 3.5 MPa. The results showed that injection pressure, ambient temperature, and pressure significantly affected spray penetration length and spray cone angle, consistent with known spray behavior trends, thus validating the experimental data. Most importantly, based on these experimental results, a non-dimensional analysis of spray penetration length was conducted, demonstrating a linear relationship between dimensionless spray penetration length and time, with a coefficient of determination close to unity. This strong correlation confirms that methanol spray behavior can be effectively modeled using gas-phase jet flow models, similar to diesel spray in engines. This study provides valuable experimental data for calibrating methanol HPDI spray models and lays the theoretical foundation for simplifying the spray modeling approach in engine simulations.