UBC Theses and Dissertations
Numerical prediction and pyrometric imaging of a hot-surface ignition-assist application Zepeda Gutiérrez, René
The combustion of natural gas is an interesting alternative to liquid fossil fuels due to its competitive price and lower CO₂ emissions. One technique to burn natural gas inside direct-injection engines is the hot-surface ignition-assist method. The natural gas jet impinges on the hot surface, which acts as an ignition source. As a constant high temperature is required in the hot surface to have quick and consistent ignition events, a numerical prediction of the temperature of an application of the hot surface technique was done, and a method to study the temperature of the hot surface was developed. One proposed application of the hot-surface method consists in a fuel injector equipped with a heater ring. The high temperature of the heater could produce an excessive temperature in the injector, affecting its functioning or the fuel. To study this, heat transfer simulations were performed. A sensitivity analysis revealed a large effect of the coolant temperature in the temperature of the injector, and a large effect of the input power and surface emissivity on the temperature of the heater. With an input power of 100 W, the injector temperature is expected to remain within 200 °C, while the heater reaches a temperature beyond 1300 °C. During the injection of the fuel, the hot surface experiences a rapid cooling event. This can affect the ignition delay, hampering the combustion efficiency. To study this, a pyrometer method with high spatial and temporal resolution was developed. A hot surface was subject to a series of cooling jets. The pyrometer method revealed that the jets with a direct orientation produced a larger temperature drop compared to jets with a side orientation, regardless of their pressure or duration. The thermometer method developed has the potential to be used in different applications where rapid changes in temperature are expected, allowing to calculate the temperature of a surface in transient-state using a digital camera and the radiation intensity at a single wavelength.
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