Flow Controlled Core Overview Hanna Reiss, Snecma Safran Group
Introduction High BPR and/or new architectures will require highly loaded, efficient and operable HPC (+20/25% vs. in-service compressor) Enhancement of highly loaded HPC achievable through Innovative concepts linked to Flow Control Integrated and optimised design for full benefit NEWAC SP5 strategy is to validate the Flow Controlled Core concept by developing flow control approach into HPC linking advanced aerodynamic design with innovative concepts maturing the integration in real-engine environment The high level objective for SP5 is A significant increase of efficiency and stall margin for the HPC +2.5% efficiency / +15% stall margin / deterioration in service reduced by 1/3 A significant reduction of Fuel Burn and emissions for the engine -3 % in fuel burn / -3% in CO2 and NOX / maintenance and production cost reduced 2
Partners involved SNECMA, Safran Group Techspace Aero, Safran Group Cenaero ONERA EPFL ECL-LMFA ULg UTBM Sulzer Metco AG 3
Description of the concept FCC with engine architecture from VITAL Tip flow control and advanced aero. Advanced casing concepts (casing treatment, casing aspiration) 3D optimised aerodynamic Non axisymetric endwall Stall active control Fast-opening valves Integrated recycling system Aspiration concept on blade profiles Evaluation and optimisation of aspiration technology on vane and blade Identification of potential benefits Rub management Modelling the abradable and its wearing Development of improved abradable Validation via rub tests 4
Objectives Tip Flow Control and Advanced Aero + 1.5pt efficiency w/o SM penalty Lower efficiency deterioration Tip injection Linked to engine air system Wall aspiration Stall active control +8% SM w/o efficiency penalty Blade aspiration concept + 0.5pt efficiency + 5% SM (SFC benefit = -0.7%) SP5 NEWAC objectives for HPC: +2.5% efficiency +15% stall margin -1/3 deterioration in service Blade/casing rub management + 0.5pt efficiency + 2% SM Lower rub clearance opening 5
Tip Flow Control and Advanced Aero Advanced casing treatment Axisymetric casing treatment Casing aspiration Baseline: in-house 6 stage high loaded HPC CLEAN Compressor rig with Tip FC and advanced aerodynamic technologies Non-axisymetric endwall optimised design for high efficiency 3D aero optimised profiles: R1 to R4, S3 S1 & S2 unchanged (low aero benefit and high integration constraint) R6: clearance sensitivity improvement 6
Tip Flow Control and Advanced Aero: design Advanced aerodynamic design Efficiency-oriented design 3D aero optimised profiles Aero adapted to the casing concepts for efficiency improvement and lower sensitivity Stall margin from casing concepts partially converted into efficiency Advanced methodology Aerodynamic and mechanical optimisation loops process Front block CFD analysis for matching Newac Through-flow velocity Assessment from CFD on final design in line with the objectives Efficiency global stack-up: +1.4pt +/- 0.2pt Additional stall margin expected vs. baseline Reduced sensitivity to clearance opening Rig-test results +0.9pt No change on SM Sensitivity on SM divided by 2 Front block CFD analysis Expected efficiency in a new HPC design 1.1pt thanks to SM specification reduction 7
Aspiration on blade profiles: Flow control device on blades and vanes Concept Delay separation at high incidence / loading Reduce shock/boundary layer interaction improve blade stability / efficiency / loading Principle for engine application : Reusing air into air engine system Reference With aspiration Potential interest at compressor level : Increasing efficiency / stall margin of conventional compressor Increasing blade loading => reduction of stage or blade number Work plan including Evaluation of the concept in an annular cascade CDF calculations Aeromechanical preliminary design of an aspirated compressor first stage Aspirated compressor first stage: global assessment Additional equipment: +7 kg Polytropic efficiency: +0.2pt without impact on the stall margin Technological integration of an aspirated stage 8
Aspiration on blade profiles: Annular cascade tests Stator vane annular cascade tested in different configurations: Baseline: smooth endwall Hub aspiration Hub and blade profile aspiration Hub and blade profile aspiration combined to blade count reduction (22%) Main results: Significant impact of the hub aspiration on losses Endwall separation successfully controlled by boundary layer suction Additional losses reduction with blade aspiration Blade aspiration balances blade count reduction Annular cascade Blades with inner channel & aspiration slot 200 without hub aspiration r [mm] 190 180 with hub aspiration r [mm] 200 190 180 Mach number distributions at stator exit (measurements) 172 277 272 267 262 257 Mach 0.69 0.63 0.57 0.51 0.45 0.39 0.33 0.27 0.21 0.15 Loss coefficient Cd 9
Stall active control: Recycling system Integration into real engine Casing redesign + new equipment = +10kg Assessment of the concept with front-block CFD computations Additional SM of 3% (system applied to the FCC aerodynamic already optimised at tip) Mass flow of the compressor impacted at full-speed : -1% Impact on the efficiency: -0.3pt polytropic Impact of the recycling system on the engine cycle and real benefit Permanent activation: SFC breakdown consequently to efficiency loss SFC +0.5% at cruise Activation of the recycling system during transients only: SFC benefit assessment at cruise = -0.25% For FCC HPC, confirmation of a benefit from tip-injection concept only on an active mode 10
Blade casing rub management Objective efficiency improvement with tight tip clearances Development of a numerical simulation tool to modelise rotor stator contacts Development of a new coating with improved characteristics under contact: abradability, corrosion (baseline = Metco 601) Component tests in order to characterize the new coating: bond test, corrosion & abradability test Numerical simulation of blade-casing contact Metco 601 NS New coating Coatings under 200h-long salt spray Global-structure test: validation of the behaviour of the blisk during contact with casing, to avoid any mechanical concern Validation of the simulation software using test data: Very satisfactory contact simulation Modelling of the divergence Abradability test 11
Blade casing rub management: Blisk global-structure test Abradable shroud Full-scale rig for blisk/casing contact Blisk Rubbing blade Determination of the contact speed close to a given coincidence Stabilization at this speed After 2min, appearance of mechanical divergence Modification of the blade characteristics end of the divergence phenomenon Under divergence, rubbing of the over-length blade into the abradable with n lobes, n corresponding to the ratio «response frequency by speed frequency» 3 instrumented blades Blade-coating contact initialization Successful test fully consistent with the expectations Time (s) Several lobes appear on casing during the mechanical divergence Thermal camera measurement of the casing Beginning of the divergence Max stress level End of the divergence Rubbing-blade gauge stress level evolution during contact 12
Result synthesis FCC Short Range application Performances Operability Weight Tip flow control and Advanced aero +1.1 pt No impact on SM Low clr sensitivity Negligible Aspiration concept on blade profiles +0.2 pt Aspirated stage 1 No penalty on SM ~ +7 kg (Blade row weight unchanged, additional equipement) Stall active control integration None + 3.5% SM 1 ~ +10 kg (Casing redesign + equipment) Blade-casing rub management +0.6 pt +4% (Higher stability all stages) None TOTAL 1.9 pt ~ + 7.5% SM +17 kg 1 Assessment for tip-injection at rotor 1 (recycling air at casing)
Implementation into a real - engine environment Applications from SP5 technologies are fully combinable SP5 technologies applicable to CRTF or high BPR conventional Turbofan Real engine benefit assessment Combination of all Flow controlled core innovations SFC benefit assessed to 1.9% 1 Fuel burn and CO 2 2 : Short Range : - 2.0% Long Range : - 3.7% 1 using usual NEWAC trades 2 using NEWAC trades = VITAL trades
Conclusion & outlook Innovative concepts and new technologies have been developped through the Flow Controlled Core approach CFD assessments have been consolidated by several tests, providing a high level confidence in these technologies These concepts are compatible and combinable into a real engine The Flow Controlled Core Short Range application provides a significant SFC benefit On this basis, further studies will be lead in order to keep improving knowledge and innovation for future clean engines.