Mechanism Study Of Turbulent Cooling In A Gas Turbine

In a gas turbine, increasing the turbine inlet temperature is an important means toimprove turbine performance. Temperature that the blade material could bear always muchlower than the inlet temperature of a modern gas turbine, so the effective cooling structureis necessary for turbine blades to ensure lasting and effective work. In the design ofturbine blade cooling structure, we need to know and master the working mechanism of avariety of cooling methods for blade cooling, on this basis, we might achieve the rationalcombination of the cooling structure and design a satisfactory cooling structure.Therefore, it’s essential to study the cooling mechanism of the various cooling methods.This paper studied the turbulent cooling process of the turbine blade internal cooling.It consists of two parts: Numerical study of turbulent cooling in a ribbed single channeland Numerical Study of turbulent cooling in a ribbed two-pass channel. DimensionlessNu and pressure loss along the channel were choosed as the measurement parameters ofwall heat transfer performance and flow loss of the ribbed channel, and by thecomparison of programs with different boundary conditions, we summmarized thevariation of turbulent cooling.In this paper, we applied with parametric models, and the grids automaticallygenerated, then reduced the workload. In the numerial simulation calculations of ribbedchannel on heat transfer, the requirements for turbulence model and grid were morestringent, so we carried out the work of choosing turbulence model and fluid domainmesh validation. After the comparison of four turbulence models, we choosed the SSTk turbulence model and-Re transition model.For ribbed single channel, we first studied how the single90°turbulent rib effectcooling air flow, and found there were a small vortex area and a big vortex area in thefront of turbulent rib, which also happened in the rear of a turbulent rib, each of thevortex area effect wall heat transfer performance differently. The study followed was theeffect of multi-rib with angle of90°and60°on the channel wall heat transferperformance, the results showed that the channel with multi-rib have more better heattransfer performance than the channel with single rib, but the pressure loss also increased;90°rib and60°rib disturbed air flow in different way, and the latter program had more better heat transfer performance. Finally we considered how four factors of rib spacing,inlet Reynolds number, channel aspect ratio and rib angle effect the channel wall heattransfer performance, the results showed that the rib spacing have different effect ondifferent aspect ratio channels; inlet Reynolds number improved the channel wall heattransfer performance, while reduced the channel overall pressure loss; wall heat transferperformance of large aspect ratio channel was better than small aspect ratio channel, andchannel overall pressure loss increased; in the four programs with different rib angle,60°rib and45°rib programs had the best heat transfer performance, while channel overallpressure loss of45°rib program was the lowest.Compared with the smooth two-channel, overall heat transfer performance of theribbed two-channel wall was greatly improved, and the overall channel pressure lossincreased, indicating that the turbulent ribs effect two-channel’s heat transfer performanceand flow characteristics significantly. For the three programs with different inletReynolds number, when Re=10000, the effect of Coriolis force due to rotation on thewall heat transfer in two-pass channel was the most obvious. Increasing inlet Reynoldsnumber was conducive to the improvement of wall heat transfer performance, andweaken the effect of rotation on two-channel wall heat transfer. Whether rotation or notand the size of inlet Reynolds number had no effect on the overall pressure loss in atwo-pass channel.