An experimental investigation of a hydrogen, methane and helium gas jet behavior using single hole and hollow cone piezoelectric injector

Abstract

There is now an increasing need for using alternative fuels especially in the transportation sector, which are more environmentally friendly fuels due to a decrease in fossil fuels and also more importantly a rapid increase in global warming. Use of Hydrogen in Hydrogen internal combustion engine either as a dual fuel option along with diesel or even better, as a sole fuel, is much better for the environment considering the emissions and their impact on the environment. But to shift from present infrastructure to a completely clean and green hydrogen economy might take many years, resources, and finance. The use of Hydrogen as a dual fuel option would provide a bridge towards the hydrogen economy. Also, the use of methane is seen as one of the potential options to get closer to the full hydrogen economy. Direct injection (DI) is a well-established technology and the combustion of hydrogen has a possibility of further being studied in a similar way as that of diesel. Further research on optimizing DI engines using Hydrogen has the potential of achieving higher efficiency and reduced nitrogen oxides (NOx) emissions.

Jets of Helium, Hydrogen, and Methane are studied in the experimental part of this thesis. These gas jets were injected into quiescent nitrogen with variable injection and chamber pressures and pressure ratios. Helium and Hydrogen have similar jet characteristics but their variations are confirmed through experimental analysis if any. Data between methane and hydrogen jets are compared in this thesis. To study these invisible, high-speed gas jets, a high-speed schlieren imaging technique was used to analyze the geometrical properties of the jets. The images obtained were post-processed to acquire geometrical attributes of jets such as penetration, width and area. Also, two different types of injectors i.e., single hole injector and hollow cone injector were used for all these jets and their results were compared and analyzed. A hollow cone injector like the one used in this thesis is already being used for gasoline engines. These injectors are capable of injecting gases up to 100 bar. The jet characteristics were also studied for different voltages for the hollow cone injector.

The results showed that the jet penetration was more for the single hole injector as compared to the hollow cone injector for the same conditions. Also, it was found that with increasing pressure ratio, penetration was more for both the injectors but the area for single hole injector got reduced over time faster compared to the hollow cone injector due to quicker dispersion of gas for single hole injector. Also, it was found that increased needle lift has a higher penetration length due to higher injection pressure.