In modern gas turbines lean premixed combustion is commonly used to minimize excessive formation of nitrogen oxide. Many highly reliable premixed combustion systems are available for methane based low reactivity gaseous fuels. The use of a highly reactive fuel like hydrogen increases the risk of flashback (FB) and so reduces the reliability of premix injectors. Thus only a limited amount of hydrogen can be added to the main fuel in common gas turbine combustion systems. These limits are very low in terms of mass fraction. Premixed combustion with hydrogen as main fuel is not yet technically feasible.

Flame FB and flame anchoring in the fuel injection region are the main threats for commercially available premixed combustion systems when using highly reactive fuels causing hardware overheating with subsequent failure.

FB in technical premixing systems normally exhibits three phases; (1) flame transition from the combustor into the burner with subsequent (2) flame propagation and (3) flame anchoring near the fuel injection ports, as shown in Fig. 1. Phase (1) has been studied more extensivly at the Chair of Thermodynamics, TU Munich than the subsequent phases (2) and (3) (cf. Baumgartner [1], Utschick [2]). In the past, the focus was on the FB mechanisms in phase (1). Four different mechanisms are described in the literature: FB in turbulent bulk flow (BFF), FB due to combustion-induced vortex breakdown (CIVB), FB in the wall boundary layer (BLF), and FB due to combustion instabilities (cf. Fig. 2). The investigation in the current project focuses on the mechanisms of the phases (2) and (3) of FB. Furthermore, the fuel-reactivity's influence on FB is being investigated. Full FB safety of injectors requires that none of the three mentioned phases can occur under engine operation conditions.