Integrated Control of Variable Geometry Injectors to Accommodate Fuels with Heating Values Varying in Real Time

As energy prices increase along with the demand for energy, it becomes a priority to utilize available fuel supplies in a clean and efficient manner. Landfill gas represents an opportunity for distributed power generation utilizing gas turbines, but also provides challenges associated with burning a diluted fuel stream of varying heating value in small scale gas turbines. This goal of this study is to design and implement active combustion control with a variable geometry injector and flame ionization sensor for the control of a microturbine generator operating on landfill gas with varying heating value. An injector was designed and tested for durability. The signal from an ion probe, incorporated into the injector, was characterized for the specific geometry of the microturbine combustor. The flame ionization sensor created a 300 V potential between the positively charged ion probe and the grounded injector body. The current transmitted by the air/fuel mixture passing between the probe and injector body was translated to a dynamic voltage signal. The averaged amplitude of the ion signal was compared to both equivalence ratio and NOx emissions, while the dynamic component of the signal was compared to CO emissions.;The variable geometry injector was able to provide stable combustion on fuel streams ranging from undiluted natural gas to a 40% dilution of CO 2. The ion signal was shown to have a linear correlation with both equivalence ratio and NOx emissions, but no definitive correlation was found for CO emissions. Despite the correlation found between the ion signal and equivalence ratio, the ion signal was determined to be unsuitable due to an extreme sensitivity to probe length, and a significant variation between the signals of different injectors.