Numerical prediction of heat transfer characteristics on a turbine nozzle guide vane under various combustor exit hot‐streaks

Abstract

The precise prediction of the aerothermal conditions at the outlet of modern combustors of aero engines is of primary interest in the aerothermal design of high‐pressure turbines. The use of high swirling flows to stabilize the flame in the new generation of lean‐burn combustors (LBCs) leads to shorter combustor length and high degrees of unsteady temperature. These aspects generate high levels of turbulence and complex temperature nonuniformity patterns at the combustor–turbine interface. Therefore, the nozzle guide vane (NGV) located at the interface exhibits a high inlet temperature gradient called a hot‐streak. The transport mechanism of the hot‐streak across the NGV needs to be decrypted to increase turbine service life and enhance its performance. In this context, the present study aims to examine numerically the effect of three new distorted hot‐streak gradients on the heat transfer characteristics across a turbine NGV. An innovative LBC is used to generate the three inlet hot‐streaks, which are highly swirled and distorted similar to real aero‐engine conditions. The use of such a generation approach avoids any simplification associated with uniform or circular contours that are widely used by researchers. A solid NGV cascade developed by NASA is adopted for the investigations. The results show significant differences in the thermal field on the cascade at each distorted thermal condition. The transport of the hot‐streak behaves differently under axial and swirl conditions. The presence of a swirl induces flow mixing and results in thermal load increasing on the cascade surfaces (NGV, hub, and shroud).

Heat transfer characteristics of a high-pressure turbine under combined distorted hot-streak and residual swirl: an unsteady computational study

“…It is important to note that the results presented in this section are related to the rotor domain, which is the main focus of the present study. Results of the effects of combined distorted hotstreak and residual swirl on the vane are already published in [23] .…”

“…During the last few years, the effects of the residual swirl and hot-streak simultaneously on HPT vane aerothermodynamics has gained a particular attention. Many studies are now available in the literature [18][19][20][21][22][23][24] . However, works on combined residual swirl and hot-streak effects on rotating HPTs are rare in the literature [25][26][27][28][29][30] .…”

“…Among the four swirled setups, the one with negative swirl orientation aligned to the vane LE was found to be the best choice as it has reduced the temperature on the vane LE and PS compared with the other setups. The more recent numerical study by Mansouri [23] on the impact of three different distorted hot-streaks at engine representative conditions on a HPT vane was carried out under axial and swirl flow conditions. The results showed significant differences in the aerothermal field on the vane cascade under each distorted hot-streak.…”

“…It was generated by a lean-burn combustor simulator designed and scaled to fit the present HP turbine stage [23] . The combustor can operate using swirl injectors of different sizes, angles and arrangements that can generate different distorted temperature topologies representative of modern aero-engine combustor outflows [23] . The distorted hotstreak features a large deformed hot temperature core aligned with the vane LE and connected to a bottom hot strip.…”