Design and off-design behavior of a tandem rotor stage

Abstract

With an ever-increasing focus on clean and sustainable energy for transport and power, aero-engine designers need to come up with engine designs that can meet the efficiency and thrust requirements. In this aspect, compressor/fan designers always aim at designs that can result in higher pressure ratios and maximum possible efficiency with a fewer number of stages. Compressor blades, which are designed for higher diffusion, have an inherent risk of flow separation. This, therefore, fixes the upper permissible limit in terms of diffusion. If the suction surface adverse pressure gradient can be efficiently managed to avoid flow separation, it would be possible to target higher diffusion factors. One such concept for achieving this is using tandem blading. In the present computational study, a conventional low-speed compressor stage performance is compared with a tandem stage. Both designs attempt similar levels of targeted diffusion. The computational results are simulated at the design and the off-design conditions. The computational results are validated with experimental data. A high percentage pitch and low axial overlap configuration are finalized for the design of the tandem rotor based on existing literature as well as initial parametric analyses. The study shows that it is possible to achieve higher diffusion for the tandem rotor in comparison to a single rotor. The behavior of the gap-nozzle, interaction of the tip leakage with the gap-nozzle, blockage due to the tip leakage vortex, performance of stator, and performance of both stages are discussed in detail in this paper.

Effect of radial inflow distortion on the performance of a highly loaded tandem stage

“…From the hub to 60% span, a lower pressure is observed for the hub distortion, which can be correlated with the higher incidence, lower energy, and ineffectiveness of the gap-nozzle. 12 The pressure difference near the gap-nozzle acts as the main force behind the momentum transfer, which is largely attenuated under the flow distortion. Figure 6(b) compares the radial variation of flow angle at the exit of the rotor.…”

“…The present work is part of an ongoing study conducted on “aerodynamics of tandem rotor in an axial compressor”. Kumar and Pradeep 12 reported some preliminary CFD results of this ongoing work. The present paper is a follow-up study in which the final design (based on gap-nozzle optimization result), and testing of the tandem rotor have been realized.…”

“…From the numerical analysis, it was reported that the tandem rotor demonstrated a 17% higher pressure rise and 2% higher adiabatic efficiency than the baseline NASA Rotor 37. Kumar and Pradeep 12 conducted a numerical study of a tandem rotor stage. The tandem stage demonstrated a higher pressure ratio and efficiency at the design point than the conventional stage.…”

Analysis of Flow Characteristic of Transonic Tandem Rotor Airfoil and Its Optimization

“…Ju et al [16] optimized a 2D tandem blade with the multiobjective genetic algorithm and artificial neural network method. A massive amount of simulation results [17][18][19][20] indicated that the tandem blade performance should be estimated in design and off-design conditions comprehensively; for instance, a larger pitchwise blade distance will lead to an increase of the loss and the choke margin simultaneously. All the results stated above show the prescribed velocity distribution design concept has become an effective measure in highly loaded axial compressors optimization.…”

A New Method for Rapid Optimization Design of a Subsonic Tandem Blade

“…This is a constructive effort to guide splitter blading design into becoming a conventional design process, which also provides a beneficial reference to developing an empirical model for tandem blades. In addition, Schlaps [10], Schneider [11], and Kumar [12,13] indicated that optimal design parameters may change in design and off-design conditions; for instance, a larger pitch-wise blade distance will lead to a simultaneous increase of the loss and choke margins [14].…”