The numerical method for 3D calculation of the turbomachinery tonal noise generation, propagation and radiation in the near and far fields taking account of the rotor-stator interaction is developed in CIAM. The method is based on the direct numerical solution of three-dimensional Euler equations for disturbances in time or in frequency domain using numerical methods of computational acoustics (CAA). For far-field radiation calculation the Ffowcs Williams method is used. The method is build into CIAM domestic aeroacoustic solver 3DAS (3 Dimensional Acoustics Solver). In this paper we present some examples of our method applications for calculation of rotor-stator interaction and propagation: • Ducted fan tonal noise simulation; • Ducted counter-rotated fan noise simulation; • Low pressure turbine tonal noise simulation.

Results of the high bypass ratio (>8) turbojet fan tone noise simulations in the cutback and sideline operating conditions are presented. Calculations are performed using the method of 3D unsteady numerical calculation of interaction between fan rows implemented in the 3DAS (3 Dimensional Acoustics Solver) CIAM in-house solver. The results of computations are compared with the experimental data for the fan under consideration, obtained in the anechoic chamber of CIAM C-3A acoustic test facility. Comparison was performed for first three harmonics of tone noise for each of conditions. It showed satisfactory qualitative and quantitative agreement between the results of the simulation and the experiment.

The matter of developing counter-rotating fans for advanced next generation aeroengines with ducted and unducted propfans is very important [1]. Counter-rotating fans can be made with fixed blades. This article considers tractor propfans consisting of two counter-rotating rotors of variable pitch (VPR) which valuable property is the possibility to turn their blades about the radial axis in order they can take the optimal position in direct thrust regimes, and to obtain a reverse thrust when turning them by a rather large angle. In this case there is no necessity to use a bulky special clamshell-type thrust reverser. In the 1-st phase of designing new CRFs it is necessary, by calculation or experimentally, to show the possibility of obtaining gasdynamic effectiveness of such fans up to the level of single-rotor fans or, at least, to obtain η*ad.f ≥ 0.90÷0.91. But the main thing is to substantiate the feasibility of getting high acoustic characteristics. CIAM (Central Institute of Aviation Motors) is carrying out calculation-experimental investigations of the SV-92 ducted counter-rotating propfan (DCRP) model (the SV-92 is an advanced fan for ultra-high bypass ratio engine [2]) as well as the SV-27 CRF (Fig. 1, Table 1) with unducted rotors for the test aircraft. This paper presents some results on gasdynamic and acoustic characteristics for the SV-27 CRF only. These investigations are aimed at providing the meeting of the test aircraft perceivable noise to ICAO chapter IV regulations.

Widening of surge margin of a transonic compressor stage is the main objective of the paper. This stage is a typical middle stage of a modern high pressure compressor (HPC) with decreased number of stages. Hot tip clearance of the stage being integrated into a six-stage HPC providing total pressure ratio π* HPC ≥ 12 and mass flow-rate < 16 kg/sec is estimated at 2.5 – 3% of blade height and is classified as a large tip clearance. In this paper experimental and 3D viscous numerical performances of the stage are obtained for two values of rotor tip clearance — equal to 0.76% (small size) and 2.66% (large size) of blade height. In doing so, tip clearance enlargement from 0.76% to 2.66% has been made by increase of casing (shroud) radius. This increase is manufactured as a circumferential trench (recess) with axial width 30% larger than rotor axial chord. Below this tip clearance is called “recessed” tip clearance. A distinguishing feature of leakage flow in case of large tip clearance is a formation of reversed flow near rotor casing. This backflow being intensified by throttling causes increase of incidence at the rotor leading edge and development of rotor stall. Casing treatments are intended to inhibit and delay the process. Among them circumferential grooves is the simplest casing treatment. Investigated in this paper casing circumferential grooves cover 82% of rotor axial chord. Numerical visualization of the near-casing streamlines demonstrates that tip leakage flow drains into the casing grooves giving rise to extended domains of positive axial velocity. Calculated mass flow-rate through groove’s cross-section demonstrates maximum over the rotor blade tip (flow into the groove) and minimum at mid-pitch (flow out of the groove). Amplitude of this variation depends on the groove location and stage throttling.

In the work are presented the results of a three dimensional computational analysis of tonal noise of two counter-rotating open rotors. The analysis was performed using 3DAS (3 Dimensional Acoustics Solver) CIAM in-house solver, designed for three dimensional calculation of turbomachinery tone noise generation, propagation and radiation in the near and the far acoustic fields. The results of the computations were compared with the results of experiments performed in the wind tunnel of Central Aerohydrodynamic Institute (TsAGI), Russia, within the project DREAM (Validation of radical engine architecture systems) of European Seventh Framework Programme (FP7). The comparison showed satisfactory correspondence between directivity diagrams for the tone noise on combinational harmonics.