Flameholding Studies for Lean Premixed Fuel Injectors for Application in Gas Turbine Engines

Open Access
- Author:
- Marzelli, Steven Benjamin
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 30, 2010
- Committee Members:
- Robert John Santoro, Thesis Advisor/Co-Advisor
Robert John Santoro, Thesis Advisor/Co-Advisor - Keywords:
- gas turbine engines
lean premixed
flameholding - Abstract:
- Due to the ever-increasing demand for energy, it is likely that stationary gas turbine engines will require the use of fuels with a diverse range of chemical compositions in the near future. Utilizing fuels, such as syngas, bio-derived fuels, hydrogen and liquefied natural gas, present serious challenges in lean premixed gas turbine engines. In particular, combustion phenomena, such as flashback and flameholding, are known to be sensitive to inlet flow conditions and fuel composition. Changes in composition can lead to an increase in the flame speed, resulting in upstream flame propagation. This has the potential to cause catastrophic damage to gas turbine hardware if the flame anchors at an undesired upstream location. The current research effort investigated flameholding characteristics of a fuel injector nozzle used in lean premixed gas turbine engine operation. A single vane of a swirled, cross-flow fuel injector was examined. A test rig with optical access to the fuel injector nozzle vane was designed and constructed, such that combustion phenomena within the nozzle could be viewed and recorded through the use of a high-speed camera. It should be noted that the likely location for flameholding was presumed to be near the location of the fuel injection jets within the nozzle vane. For hot-fire testing, flow conditions in the combustor apparatus were closely matched to those experienced during the full-scale operation of a stationary gas turbine engine. The test apparatus was outfitted with both high- and low- frequency pressure and temperature transducers in order to determine inlet fuel and air flow conditions as well as monitor combustor performance. Once full operating conditions were reached for a given test, a hydrogen torch ignition system was fired in order to simulate a severe combustion event upstream of the fuel injector nozzle. This practice is commonly used in examining fuel injector nozzle performance. A series of tests were conducted at a wide range of flow conditions with a variety of fuel mixtures in order to develop a threshold for flameholding in terms of reference air velocity and fuel composition. A range of inlet air velocities, from 190 ft/s to 55 ft/s, and several fuel compositions were examined. Fuels studied included natural gas (~95% methane) and various ethane-natural gas mixtures to determine the nozzle’s susceptibility to flashback and flameholding with natural gas and higher hydrocarbon blends. For all cases tested, there was no evidence of flameholding within the fuel injector nozzle after hydrogen torch firing. However, during tests at lower inlet velocities with ethane-natural gas mixtures, a flame did appear to anchor at a location downstream of the fuel injector nozzle as observed via high-speed pressure and temperature measurements. Because the flame held outside the field of view of the high-speed camera, the exact location of the hold is unknown.