Saini, RohitRohitSainiDe, AshokeAshokeDeAggarwal, VenuVenuAggarwalYadav, RakeshRakeshYadav2025-08-302025-08-302018-01-0110.1007/978-981-10-7473-8_122-s2.0-85049681715http://repository.iitgn.ac.in/handle/IITG2025/22975The study reports on the numerical investigation of lifted turbulent jet flames with H<inf>2</inf>/N<inf>2</inf> fuel issuing into a vitiated coflow. The hot vitiated co-flow containing oxygen as well as combustion products stabilize the lifted turbulent flame by providing an autoignition source. A 2D axisymmetric formulation has been used for the predictions of the flow field, while multidimensional Flamelet Generated Manifold (multi-FGM) approach has been used for turbulence-chemistry interactions in conjunction with RANS approach. The chemical kinetics in H<inf>2</inf>-O<inf>2</inf> combustion is followed by (Mueller et al, Int J Chem Kinet 31: 113–125, 1999 [1]) and (Li et al, Int J Chem Kinet 36(10): 566–575, 2004 [2]) mechanisms and the difference in chemical kinetics is analyzed (in terms of auto-ignition distance) using one-dimensional calculations. The major difference between the two mechanisms is the value of rate constants contributing towards the source of the autoignition and the corresponding enthalpy of formation of OH radicals. The lift-off height is determined from the axial distance (from the burner exit) at which the auto-ignition occurs, and is located through local concentration of OH radical equivalent to 2 × 10⁻⁴. In order to understand the impact of chemical kinetics on the autoignition, speeding up (Set A) and delaying (Set B) auto-ignition controlled reaction rates are augmented and corresponding changes in lift-off height are observed. Hereafter, the comprehensive chemical kinetics sensitivity analysis is carried out in understanding the underlying behavior of HO<inf>2</inf> radicals as autoignition precursor and OH radicals as reaction rate determinant. It is found that some specific reaction is most sensitive to auto-ignition and plays a vital role in lift-off height predictions. The results obtained in the current study elucidates that the flame is largely controlled by chemical kinetics.falseLifted flame | Multi-FGM approach | Role of chemical kineticsBook Chapter18653537293-31420181chBook Series1