Lean blowout (LBO) limit is one of the most important parameters for aero engines. The LBO must be avoided during the whole flight envelope and modes. Thus the LBO limit should be predicted accurately during the research and development (R&D) process of an aero engine combustor. Some prediction models had been proposed by the previous studies. Lefebvre’s LBO model is widely used among these models due to its good accuracy and generality. Based on Lefebvre’s LBO model, the flame volume (FV) model is proposed to improve the prediction accuracy as well as keep the good generality. However, an additional equation is needed when the FV model is applied to predict the LBO limit. Based on our previous studies, the volume in the combustor liner enclosed by the iso-surface whose temperature is 900K could be chosen as the flame volume. The flame volume could be served as the additional equation and further makes the FV model available for the LBO limit prediction. This method could be named as the hybrid method based on the FV concept in this paper. On the other hand, the LBO limit at high altitude is attracting more and more attentions due to the extension of the flight envelope and modes in the recent years. Low inlet temperature is one of the most typical characteristics for the operating condition at high altitude. The temperature could reach less than -40 °C at high altitude. Compared with the normal condition, the characteristics of flow, atomization and combustion are different at the low temperature condition. In this paper, the hybrid method based on the FV concept is applied to predict the LBO limits of 11 combustors with low inlet temperature. The inlet temperature is 236.2K (corresponding to the altitude of 8km). The results show that the flame volumes obtained by the numerical simulation vary near linearly with the fuel/air ratio when the fuel/air ratio is close to the LBO limits. For all these 11 combustor configurations, the LBO limits with low inlet temperature (236.2K) obtained from the hybrid method based on the FV concept are significantly larger than those with normal inlet temperature (300K) obtained from experiments. The maximum and minimum increases are 29% and 2%, respectively. The LBO limits increases are more than 20% and 10% for 6 out of the 11 combustors and 9 out of the 11 combustors, respectively. The reasons for the increase of the LBO limits at low temperature include the decreasing of chemical reaction rate and evaporation rate, the increasing of the mean drop size.


Hybrid Method Based on FV Concept for Lean Blowout Limits Predictions for Aero Engine Combustors With Low Inlet Temperature

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

Turbo Expo - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.