## 1 Introduction
[17] examined the combustion instability profile of ethanol and n-heptane fuels under different combustor geometries and suppressed the combustion instability using CO\({}_{2}\)-O\({}_{2}\) or CO\({}_{2}\)-Ar jet-in-crossflows. [PERSON] et al. [18] investigated the suppression effects of hydrogen microjets on the combustion instability, highlighting the need to consider changes in flame NOx emissions after jetting. [PERSON] et al. [19] examined the suppression of combustion oscillations using local hydrogen jets and highlighted the high-temperature challenges caused by hydrogen doping. [PERSON] et al. [20; 21] investigated the mitigation of combustion instabilities through local diluent injections in a premixed swirl-stabilized combustor. The results confirmed that carbon dioxide and nitrogen effectively controlled combustion instabilities. [PERSON] et al. [22] explored the flow structures in a lean-premixed swirl-stabilized combustor with a microjet air injection. The results indicated that vortex shedding in the recirculation zone inside and outside the flame plays a key role in suppress ing thermoacoustic oscillations. [PERSON] et al. [23] found that the pressure oscillations could be effectively suppressed by fuse gas jets and maintain relatively low levels of CO and NO\({}_{\text{x}}\) emissions. [PERSON] et al. [24] revealed that fuel injection parameters can influence the stability and emission performance of the combustion system. [PERSON] and [PERSON] [25; 26] confirmed that superheated steam and CO\({}_{2}\)/O\({}_{2}\) jet-in-crossflows could suppress the thermoacoustic instability. [PERSON] et al. [27] investigated the effect of low-bandwidth open-loop control on the combustion instability using high-momentum air jets. The results revealed that jets can significantly alter the distribution area of flame heat-release pulsations. These studies suggest that air injection methods, such as jet-in-crossflow, can suppress the thermoacoustic oscillations and regulate NO\({}_{\text{x}}\) emissions. Owing to its low cost, ease of implementation, and high reliability, jet-in-crossflow has emerged as a vital method for investigating thermoacoustic instability and NO\({}_{\text{x}}\) emission characteristics at different momentum ratios [28]. Unlike hydrogen, inert jets, such as argon or helium, can adjust the flame equivalence ratio without causing overheating issues. The aforementioned studies indicate that the components of the jet medium significantly affect the thermoacoustic oscillation suppression, while the jet mode determines the final control effectiveness. Additionally, recent studies have shown that stratified combustion modes can enhance flame stability and reduce NO\({}_{\text{x}}\) emissions [29]. Although stratified combustion and jet-in-crossflow methods regulate combustion and emission performance, no research has yet explored the effect of stratified jet-in-crossflow on combustion instability. Although scholars have investigated the inhibitory effects of microjet injections on thermoacoustic instability and NO\({}_{\text{x}}\) emissions, no studies have explored the control of combustion oscillations using stratified jet-in-crossflow. Currently, no research has examined the use of stratified jet-in-crossflow with different parameters to control the thermoacoustic oscillations. To address this gap, this paper aims to explore the characteristics of thermoacoustic oscillations and NO\({}_{\text{x}}\) emissions at different argon/helium volume ratios and flow rates. Notably, jet parameters can influence the behavior of thermoacoustic oscillation modes. Therefore, this study investigates the effect of stratified Ar/He jet-in-crossflow on the migration of these oscillation modes. Overall, this paper aims to elucidate the suppression mechanisms of stratified jet-in-crossflow. This study investigated the control effects of different jet flow rates and Ar/He volume ratios.