Numerical and Experimental Research of the Highly Loaded Compressor 1st Stage: Part 1 — Aerodynamics

It is recognized that concept of the compressor with highly loaded 1^st stage is one of the perspective schemes which provides high performance of turbomachine in terms of adiabatic efficiency and stall margin. Since the reduction of the number of stages and increase of the overall pressure ratio is a general trend in aeroengine design, the investigations of highly loaded stage aerodynamics are of significant importance. It is a well-known phenomenon that the implication of the highly loaded stages with wide-cord blades in high pressure compressor leads to higher level of unsteadiness in the flow and vibrations caused by increased azimuthal non-uniformity of the flowfield in row-to-row spacing. Studies devoted to unsteady nature of rotor-stator wake-blade and shockwave-blade interaction in stages with high total pressure ratio are complicated and time consuming in numerical way and need good instrumentation for experiment on the one hand, and allows achieving additional benefit in aero and mechanical properties on the other.

Investigation object is a 1.5-stage with wide-cord rotor blades modeling a full-scale first stage of advanced highly loaded high pressure compressor. Overall total pressure ratio of the stage in the design point is 2.32.

Numerical part of the investigation includes a series of the simulations in 3D RANS statement to assess the integral performances of the stage at different operating conditions. The simulation is carried out using the blade geometries defined with taking into account pressure distribution at the blade sides. The second part of the simulation is devoted to the analysis of unsteady row interaction in URANS statements at the design rotational speed. Finite volume grid covering full-annulus blade rows was generated. Total numbers of meshed passages are: 3 blades of inlet struts, 29 inlet guide vanes, 29 rotor blades, 58 stator vanes. Through flow simulation is carried out using dual time-stepping scheme with physical time step corresponding the movement by approximately 1 cell at the rotor-stator interface at 1 time step. The calculation continues until the flow parameters become periodic in time. The analysis of instantaneous and time averaged flow distributions is carried out. Viscous wakes propagation from struts, vanes and rotor blades through the flowpath is studied. The comparison between time averaged flow fields and the distribution from steady RANS shows some features in different problem statement. Unsteady pressure distribution at blade sides is extracted at each time step for mechanical analysis.

Experimental part of the investigation consists of series of tests at CIAM compressor test rig at wide range of rotational speed. The instrumentation of the stage allows to measure steady and unsteady flow parameters and to control mechanical behavior of rotor blades by strain gages and tip timing method.

Finally, the comparison between measured data is performed in integral performances and flow distributions.