The facility for acoustic tests of aero engine fans in conditions of anechoic chamber is created in Central Institute of Aviation Motors (Moscow). The facility is designed for testing models of single rotating fans and counter rotating fans. The measurements of the sound are carried out in forward and rearward semi-spheres simultaneously. Design features of the anechoic chamber and its acoustic performance are presented. Also a fan drive system and systems of acoustic and aerodynamic measurements are described. In particular fan rotor max rotation frequency makes up 13,000 rpm at each shaft max power 2.5 MW. The rig acquisition system allows checking in real time results of complete three-octave analysis of machine noise on all 24 channels in a measurement frequency range of 0œ80 kHz.

Results of numerical calculations of fan tone noise for three variants of swept stator are presented. In the first variant the stator vanes are not leaned. In the second variant stator vanes are leaned on 30 degrees in the direction of rotor rotation and in the last variant the vanes are leaned on 30 degrees in the opposite direction. Calculations are carried out for approach fan operational conditions. These results are compared with the experimental data for the fan under consideration obtained in the Central Institute of Aviation Motors (CIAM) C-3A acoustic test facility. Comparison showed that the method can be used for qualitative estimation of tone noise variation with the change of stator lean.

The experimental investigation of leaned bypass stator vanes impact on the fan model acoustic and aerodynamic performance was carried out for the purpose of noise reduction technology development for advanced turbofan engine. It was studying three versions of bypass duct guide vanes of fan model with pressure ratio 1.54, tip speed 390 m/s and inlet diameter 700 mm. The fan model reference configuration has the blades swept back in the meridional direction (the sweep angle is equal to 18.3 degrees). The blade aspect ratio is equal to 2.13; blades count is equal to 41. The blade has approximately the same profiles along the blade height with the maximal thickness 5.3%. The second configuration of bypass stator was obtained by blade tip and hub profile displacement in circumferential direction clockwise and counter clockwise accordingly in such a manner that the tilt angle between the blade centreline and the radial direction kept constant and equal to +30 degrees. At last, the third configuration of bypass stator was obtained by blade tip and hub profile displacement in circumferential direction counter clockwise and clockwise accordingly in such a manner that the tilt angle between the blade centreline and the radial direction kept constant and equal to 30 degrees. Spectra and directivity diagrams of three versions of fan model measured in the anechoic chamber of C-3A test facility were analyzed. It was obtained, that the stator version leaned in the direction of rotation showed noise reduction relative to the reference stator version; on the contrary the stator version leaned counter to the direction of rotation showed increased noise levels. More noticeable these trends appear at approach mode in rear hemisphere.

The results of 700-mm fan model study in terms of acoustic response obtained at the CIAM C-3A test rig anechoic chamber are represented. The fan model is a bypass universal propulsion simulator UPS (bypass ratio 8.5, pressure ratio 1.54, fan tip speed 395 m/s, scaled factor k = 2.7) with one-stage fan and nacelle inside which hush kit may be installed. At the CIAM test rig C-3A acoustic investigation of the S-2 wide chord fan model was carried out. The results showed that at Runway and Flyover the S-2 fan model noise spectra practically did not differ from the noise spectra of single stage fan models with conventional blades. At Approach mode the S-2 fan model noise spectra radiated in front hemisphere contains several high level tonal components which could be identified as tonal noise at sum frequencies of rotor interaction with the first booster stage. It should be mentioned, that at Approach mode tonal noise at BPF practically does not exceed the broadband noise. The UPS noise matrices obtained allowed noise prediction of the hypothetical aircraft equipped with turbofan, the scaled fan model of which was tested.

Purpose -The purpose of the conducted investigations is assessment of performance improvement of hybrid gas-turbine engine (HGTE) based on solid oxide fuel cell (SOFC) using cheaper and environmental alternative fuels (AF) such as liquid methane and propane -butane mixture (propanebutane). This paper also assessed the efficiency of mid-flight propulsion system (PS) based on HGTE for advanced short -medium hall aircrafts (SMHA) of 2025 (with level of parameters corresponding to technologies of 2025-2030 time period). Design/methodology/approach -According to purposes of this paper, following are conducted: Analysis of properties of conventional and advanced aviation fuels, updating of architectures and parameters of energy system of HGTE based on SOFC using different fuels (kerosene, methane and propane -butane). Examination of rational architectures and updating of possible design parameters of HGTE using different types of fuel. Assessment of efficiency of PS with HGTE using different fuels under aircraft criteria. Assessment of emission of harmful substances and acoustical efficiency of SMHA with HGTE using different fuels. Findings -Improvement of technical and environmental performances of SMHA with HGTE based on SOFC using AF in comparison with turbofan is shown. Research limitations/implications -Accuracy of research results is defined by a number of the adopted aircraft and engine restrictions, as well as accuracy of prediction concerning to the improvement of integral characteristics of elements SMHA and PS with HGTE for 2025. Practical implications -Advantages of HGTE based on SOFC create good preconditions for initiation of works on development of new-generation aircrafts using AF after 2025. Social implications -Development of SOFC technologies result in evolution of new high-economic and environmental friendly hybrid gas-turbine PS for aircrafts using AF, Improvement of an environmental situation around the airport, decrease of CO 2 emission for full-flight cycle, creation of scientific and technological base for transition to electric PS of full electric aircraft. Originality/value -Research results show that application of AF increases efficiency of electrochemical generator (ECG) based on SOFC and fuel efficiency of whole engine, which enable to use HGTE for PS of advanced aircrafts more effectively than turbofan. As distinct from storage battery (Bradley et al., 2010) and ECG based on Polymer Electrolyte Membrane Fuel Cell (Horyson Energy Systems, 2010), specific characteristics of ECG based on SOFC using methane allow to design PS for SMHA of 2025.