Large-bore, slow-speed, natural gas two-stoke cycle engines used for power generation and gas compression on natural gas pipelines suffer from poor in-cylinder mixing processes caused by ineffective fuel delivery, which can increase emissions and create low engine efficiency (higher fuel consumption). To address this problem, researchers at the Colorado State University (CSU) Engines and Energy Conversion Laboratory (EECL) used Planar Laser Induced Fluorescence (PLIF) to image the fuel in the cylinder, or combustion chamber.
PLIF allows the user to visualize injected fuel flow and the ensuing fuel and air mixing process. A seeded gas (acetone tracer) is used such that, when irradiated with laser light, it fluoresces, enabling the gas mixture to be visible for high-speed photography within an optically accessible combustion chamber.
The EECL used The Cooke Corporation's DiCAM-PRO ICCD camera, along with a Spectra-Physics Model LAB-150-10 Nd:YAG laser, as the basis for the PLIF data collection. With a custom designed gating power supply, a 12-bit dynamic range, and high resolution CCD, the camera was able to meet the experiments' criteria by providing variable gating (gate widths down to 3 ns), accurate synchronization with other equipment, single photon detection sensitivity, and high resolution (1280 x 1024). The Nd:YAG laser operates at 266 nm and produces over 70 mJ/pulse at 10 Hz with a 5 ns pulse width.
The experiments have been completed, demonstrating that high-pressure fuel injection can reduce fuel consumption and pollutant emissions through improvements to in-cylinder mixing and combustion.