Parametric study of turbine NGV blade lean and vortex design

The effects of blade lean and vortex design on the aerodynamics of a turbine entry nozzle guide vane （NGV） are considered using computational fluid dynamics. The aim of the work is to address some of the uncertainties which have arisen from previous studies where conflicting results have been reported for the effect on the NGV. The configuration was initially based on the energy efficient engine turbine which also served as the validation case for the computational method. A total of 17 NGV configurations were evaluated to study the effects of lean and vortex design on row efficiency and secondary kinetic energy. The distribution of mass flow ratio is introduced as an additional factor in the assessment of blade lean effects. The results show that in the turbine entry NGV, the secondary flow strength is not a dominant factor that determines NGV losses and therefore the changes of loading distribution due to blade lean and the associated loss mecha- nisms should be regarded as a key factor. Radial mass flow redistribution under different NGV lean and twist is demonstrated as an addition key factor influencin~ row efficiency.

Blade Lean and Tip Leakage Flows in Highly Loaded Compressor Cascades

Blade lean has been intensively utilized in axial compressors.In this study,three families of highly loaded compressor cascades featuring different aspect ratios(AR)with different levels of blade lean were designed and simulated with and without tip clearance.The influences of blade lean on corner separation and tip leakage flow(TLF)were investigated.Results show that blade lean can exert spanwise pressure gradient confined to the fore part,spanwise mass flow rate re-distribution exhibiting differently at fore and rear part of blade,and stage reaction variations.AR has a significant influence on blade lean.With the increase of AR,corner separation grows significantly and requires a higher lean level to be controlled.TLF eliminates corner separation of linear cascades but also increases the loss of leaned cascades;blade lean introduces 22%higher tip leakage mass flow,but exhibits 43%(blade M)and 38%(blade E)lower tip leakage loss.The flow mechanism can be mainly accounted by the reduction of bulk flow velocity,tip leakage velocity and the velocity difference near leading edge(LE).High AR cascade induces re-distribution of TLF along blade chord and reduces leakage loss compared with low AR counterpart.

Investigating the effect of blade sweep and lean in one stage of an industrial gas turbine's transonic compressor

In this paper,the simultaneous effects of the sweep and lean of the blades in one stage of a transonic compressor on its performance have been investigated.Then,with the help of numerical solution,fluid flows over these two modified geometries generated from the original sample were analyzed.Considering the applied constraints,the two generated rotor geometries have different geometrical characteristics;so that in rotor No.1,the blade has a backward sweep and it is less affected by lean,while in the modified rotor No.2,the blade has a forward sweep and it is more affected by lean.In the first sample,it is observed that the stage efficiency increases by 0.5%for operating design,while the stall margin reduces,and the chocking mass flow rate diminishes by 1.5%.Also regarding the second modified blade,the results indicate that the stall margin increases,the choking flow rate at the nominal rotational speed of the stage increases by 0.18%and the stage efficiency increases by 1%.The comparison of numerical results also shows that,in the first modified rotor,the pressure ratio of the stage diminishes by 0.01%;while in the second sample,the pressure ratio of the stage increases by the same amount.These results were then compared with the experimental results,showing a good agreement.