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High Speed Visualization

Multi-hole High Pressure Hydrogen Injection Studies


Hydrogen makes an excellent fuel for combustion engines. The major drawbacks to hydrogen as an engine fuel are the tendency for backfire and pre-ignition, and the low power density due to the displacement of air in the intake by the gaseous fuel. Direct injection of the hydrogen into the engine overcomes most of these problems. However, in-cylinder mixing phenomena are complicated and require a good knowledge of the injector characteristics. In this study, several prototype high pressure hydrogen injectors were studied in a constant volume chamber.

A Z-type schlieren system was used to visualize the gas jets. In the movie, a three hole injector is shown injecting hydrogen at a pressure of 104 bar into the nitrogen-filled chamber at 3.8 kg/m3. The movie was acquired at a frame rate of 4800 fps using a high speed CMOS camera. The raw images have been corrected to remove static flaws in the imaging system. Some interesting features of the jets are clearly visible in the images. At this injection pressure the jet is underexpanded and expansion waves can be seen in the plumes. These data, and those from other conditions, are being used to assess the near-nozzle conditions and the far-field jet scaling. This information is necessary to accurately model the injection process, which will facilitate a shortened development cycle for hydrogen direct-injection engines.

Acknowledgements: This work was performed by Ben Petersen and was supported by Ford Motor Co.

Publication: SAE Paper 2006-01-0652

For more information contact Prof. Ghandhi

Investigation of Diesel Spray Impingement


Low temperature Diesel combustion often requires very advanced injection timings, which can lead to fuel spray impingement on the piston or cylinder liner. Liquid fuel films are problematic because of the low volatility of Diesel fuel. In this study the fuel impingement process is being parametrically investigated for a range of injector orifice sizes, chamber densities, impingement distances and impingement angles.

The movie shown was acquired with a 0.350 mm orifice at a chamber density of 25 kg/m3, an impingement distance of 60 mm and a chamber temperature of 500 K, which was chosen to match the expected engine wall temperature. The movie was acquired by backlighting the spray and using a high speed CMOS camera. The framing rate was 12000 frames per second. These data are being coupled with measurements of the fuel film thickness on the impinging surface.

Acknowledgements: This work was performed by Bo Yang and was supported by Caterpillar.

For more information contact Prof. Ghandhi