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ACTIVELY STABILIZED ISENTROPIC SUPERSONIC INLET (ASISI)

ACTIVELY STABILIZED ISENTROPIC SUPERSONIC INLET (ASISI). PROGRAM OVERVIEW March 7, 2002. PROBLEM STATEMENT AND CONCEPT FOR FLOW CONTROL PROGRAM Elements & Responsibilities Brief Descriptions and Progress SOME TECHNICAL DETAILS (‘Appendices’). OUTLINE.

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ACTIVELY STABILIZED ISENTROPIC SUPERSONIC INLET (ASISI)

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  1. ACTIVELY STABILIZED ISENTROPIC SUPERSONIC INLET (ASISI) PROGRAM OVERVIEW March 7, 2002 ASISI Overview

  2. PROBLEM STATEMENT AND CONCEPT FOR FLOW CONTROL PROGRAM Elements & Responsibilities Brief Descriptions and Progress SOME TECHNICAL DETAILS (‘Appendices’) OUTLINE Northrop’s ‘dual relevant’ QSP concept, baseline for active inlet design and control studies ASISI Overview

  3. INITIAL CONCEPT FOR HIGH EFFICIENCY INLETInternal Compression With Little or No Shock Losses • Less efficient, stable internal compression normal shock d/s of throat: d = 0.94 boundary layer loss ~ 0.03 • Highly efficient, unstable internal compression no shock losses: d = 0.97 robust boundary layer at design ASISI Overview

  4. TRADE-OFF: INLET STABILITY VS. PRESSURE RECOVERY • Stability of uncontrolled inlet determined by shock position move shock u/s and control it pressure recovery increasing stability as shock moves d/s reducing exit static pressure gain stability margin and performance using control ASISI Overview

  5. ESTIMATED COMPONENT PERFORMANCE BENEFITS Propulsion Technology Areas Studied Under QSP Phase I • using optimized BPR at given c & component efficiencies: † assumes 1% red. in TOGW through higher BPR ‡ assumes 2.5% red. in TOGW through fewer comp. stages and higher BPR * internal cooling allows higher Tt4. Value quoted meets range target in conj. with aspir. compr. ASISI Overview

  6. OBJECTIVE: 97% Total Pressure Recovery at Cruise Condition Minimize Stabilization Bleed BENEFITS: +2.5% or Better Recovery Improvement +1.25% SFC Improvement  100+ NM Range Increase 30-60% Reduction in Required Stability Bleed Sonic Boom Reduction APPROACH: Advanced Design of Reduced Stability, Increased Efficiency Inlet Active Disturbance Rejection to Eliminate Unstart Generalized Dynamical Analysis and Control Design Tools LIMITED DATA RIGHTS USE, DUPLICATION OR DISCLOSURE OF THESE DATA, IN WHOLE OR IN PART, AND IN ANY MANNER, IS FOR GOVERNMENT PURPOSES ONLY, AND TO HAVE OR PERMIT OTHERS TO DO SO FOR GOVERNMENT PURPOSES ONLY PROGRAM GOALS AND APPROACH ASISI Overview

  7. PROGRAM ELEMENTS • DIFFUSER DESIGN (MIT) • Develop a Viable, Near-Isentropic, Reduced Stability Design • CONTROL ARCHITECTURE DEVELOPMENT • Understand Unstart Phenomenology • Propose Control Strategy • Initial Simulation Studies (1D) • Next-Generation Model Development • EXPERIMENTAL DEMONSTRATION FACILITIES • 1/50th Scale Experiment • 1/12th Scale Experiment ASISI Overview

  8. DESIGN CHALLENGES subsonic diffusion • Shock loss vs. viscous loss • Impacts length • Bleed requirement • Set by boundary layer thickness upstream of slot • Exit Mach number • Static stability • Choice of throat Mach, shock Mach • Aerodynamic shaping • Supersonic, subsonic regions supersonic compression • Exit Mach ~ 0.55-0.6 M=2.2 Bleed slot • Shock system loss • Supersonic compression shocks • Terminal normal shock • Boundary layer loss • Long development along length • Shock-boundary layer interaction growth • Subsonic recovery ASISI Overview

  9. CURRENT DESIGN CONCEPTDesign Using Same Tools As Aspirated Compressor • ASPIRATED, MIXED COMPRESSION DIFFUSER • Much shorter, reducing BL losses • Bleeds also reduce BL thickness, make more robust to variations • Shock losses offset BL gains ~ same recovery • Bottom line: lighter, more easily integrated inlet • MIXED-OUT PRESSURE RECOVERY = 97%, EXIT MACH = 0.55 • STEADY BLEED REQUIREMENT = 4% OF INLET MASS FLOW Shock Bleed 2% Shock Bleed 1% Control Bleed 1% ASISI Overview

  10. PHENOMENOLOGY OF UNSTARTAnd Concept for Prevention • TWO ROUTES TO UNSTART • If downstream pressure or upstream Mach number rise too high, shock moves up to throat, becomes unstable and blows out • If Mach number at throat falls below 1, a new shock forms at the throat, blows out the front and unstarts the original shock (See Movies Unstart.mpg and Unstart2.mpg) • ACTIVE CONTROL • Maintain throat mach number near it’s design value (perturbations to cancel propagate from upstream) • Maintain shock position (main perturbations that cause shock motion come from compressor face) • Initial studies indicate that bleed is a simple and effective actuator • Static pressure and perhaps temperature must be sensed ASISI Overview

  11. LIMITED DATA RIGHTS USE, DUPLICATION OR DISCLOSURE OF THESE DATA, IN WHOLE OR IN PART, AND IN ANY MANNER, IS FOR GOVERNMENT PURPOSES ONLY, AND TO HAVE OR PERMIT OTHERS TO DO SO FOR GOVERNMENT PURPOSES ONLY Sensors Actuators ControlComputer Inlet Flow Isentropic Ramp Bleed Flow To Bleed Cavity Bleed Slot Control Actuators Solenoid Actuator w/ Spring-Loaded Valve (Densitron or Moog Servos) Bleed Air to Subsystems Bleed Cavity ACTIVE CONTROL SYSTEM ARCHITECTURE Continuous Isentropic Compression Surface (Cruise Throat Position) Terminal Shock Takeoff Throat Position ASISI Overview

  12. LIMITED DATA RIGHTS USE, DUPLICATION OR DISCLOSURE OF THESE DATA, IN WHOLE OR IN PART, AND IN ANY MANNER, IS FOR GOVERNMENT PURPOSES ONLY, AND TO HAVE OR PERMIT OTHERS TO DO SO FOR GOVERNMENT PURPOSES ONLY Sensors Actuators ControlComputer Solenoid Actuated Bleed Valves Static Pressure Ports CompressorDisturbances AtmosphericDisturbances Terminal Shock Controller Downstream perturbationsAlso Feed ‘Forward’ (in Time)to Predict Shock Location Correct Number of Bleed Valves Open to AbsorbDisturbance Appropriate Control ActionFrom Remote and LocalActuators Stabilizes Shock Upstream Disturbances AreDetected by SensorsFar From Throat Feedback Signal FromThroat Provides Corrections+ Adaptation of Feedforward Estimation RoutinesPredict Effect on Throat Mach Number Shock Motion Sensing + Prediction of UpstreamDisturbances Feeds Into Shock Location Models Bleed Air Flows toEnvironmental System Controller Subtracts SystemDelays (Servo + Fluid Mechanical) to Compute Time to Launch Cancellation Action FEEDFORWARD / FEEDBACK CONTROL Note: View in Slideshow Mode ASISI Overview

  13. USE 1D EULER CODE (FAST, SIMPLIFIED DYNAMICS) IDENTIFY VARIOUS SYSTEM TRANSFER FUNCTIONS Disturbance to Sensed Pressure Disturbance to Throat Mach Number Actuation to Throat Mach Number USE TRANSFER FUNCTIONS TO DESIGN FEEDFORWARD CANCELATION TRANSFER FUNCTION Invert out measurement dynamics, launch wave at appropriate time advance to arrive at throat simultaneous to disturbance Ultimate implementation would require feedback to make robust (See Movie Control.mpg) CONTROL SYSTEM DEMO DESIGNS(Upstream Control) ASISI Overview

  14. NEXT-GENERATION MODEL DEVELOPMENT • 1D SIMULATIONS • Improved accuracy of Euler scheme • Incorporate M profile from latest mixed-compression design • Incorporate actuation models from 2D simulations • Perform more detailed control studies • 2D SIMULATIONS • Develop actuation models for incorporation into 1D models • Develop reduced-order input-output models that capture physics in a model suitable for control law design • Arnoldi methods for CFD model order reduction • Extension to supersonic, possible nonlinear regime • Validate control laws designed in 1D ASISI Overview

  15. ATMOSPHERIC DISTURBANCE MODEL • Inlet Perturbations • Atmospheric, Angle of attack changes • Perturbation Characterization • Isothermal Horizontal, Vertical Gusts • Atmospheric speed of sound (temperature) change • Angle of attack (Da=Dv / U) • Inflow boundary condition is superposition of above perturbations ASISI Overview

  16. OPEN LOOP RESPONSE TO PERTURBATION IN ATMOSPHERIC TEMPERATURE Control Point actuator ASISI Overview

  17. CLOSED LOOP RESPONSE Control Point actuator ASISI Overview

  18. ACTIVE CONTROL APPLIED TO 2D REDUCED-ORDER MODELDisturbance: atmospheric temperature variationsOutput: throat Mach number • Apply same method as previously demonstrated in 1D simulations • Model-based control design • Feed-forward inversion of sensor and actuator transfer functions • Goal: cancel disturbance before it reaches the throat • Challenges introduced by 2D • Currently canceling one output: average throat Mach number • Actuator effect on average throat Mach number is non-minimum phase: limits frequency range of cancellation • Capability demonstrated here: • Low order modeling for control system design • Feed-forward approach still works ASISI Overview

  19. STEP INPUT BLEED PROPAGATIONTO THROAT (13 FRAMES) • The effect of a step in bleed must travel across duct to get to throat – this results in A non-uniform distribution of response at the throat • The actuator characterization derived from simulations such as this will be incorporated into the 1D control design models, so that they account for the 2D effects • Slots run across entire span – 3rd dimension should not change behavior significantly ASISI Overview

  20. Step Response of Mach Number at Throat to 1% Bleed Step • Mach number response at various spanwise stations (all at throat) • One time constant will ~characterize settling time of all stations • ‘Broadening’ of Mach no distribution (both in transient and SS) is detrimental to control system effectiveness ASISI Overview

  21. Wind Tunnel Setup and Initial Tests • PURPOSE • Verify design recovery • Validate unsteady modeling (including actuation) • Psuedo-control tests (time scales too short for full implementation of control) • MIT FACILITY • 2.5”x4” Test Section • Mach no. up to 2.2 • Blow-down for ~ 2 minutes • Retest every 30 minutes • STATUS • Shakedown with representative wedges complete • Test article in final stages of manufacture/assembly Shown: Test section and focusingschleiren system ASISI Overview

  22. WIND TUNNEL SETUP AND INITIAL TESTS • PURPOSE • Verify design recovery • Validate unsteady modeling (including actuation) • Psuedo-control tests (time scales too short for full implementation of control • MIT FACILITY • 2.5”x4” Test Section • Mach no. up to 2.5 • Blow-down for ~ 2 minutes • Retest every 30 minutes • STATUS • Test article assembled • Schlieren images of operation at design point and unstart Shown: Test section with assembled inlet ASISI Overview

  23. 1/50TH SCALE TEST ARTICLE Transpiration • Kulite transducers: Inlet, throat, exit • Piezo-actuators provide bleed flap excitation • Upper surface bleed to maintain boundary layer attachment • Throttle at exit to control static pressure boundary condition Throttle Kulites(3 places) Piezo Stack Actuators(2 places) Bleed Flaps ASISI Overview

  24. TEST ARTICLE • Kulite transducers: Inlet, throat, exit • Piezo-actuators provide bleed flap excitation • Upper surface bleed to maintain boundary layer attachment 1 inch Throttle flap Bleed Flaps ASISI Overview

  25. TEST ARTICLE Movable Upper Surface Flow Direction Bleed Flaps 5.5 inches 4 inches Kulite Transducer Bleed Flaps ASISI Overview

  26. FACILITY FOR 1/12th SCALE TESTING Required to achieve tractable time scales for control WILL REFURBISH HEAT EXCHANGERS, DRYERS, ETC. NEW TEST SECTIONTO DESIGN: NON-STANDARD ASPECTRATIO, WITH ACTUATION GTL SUPERSONIC FLOW LOOP Diffuser Test Section (4” by 4”) Compressor (~13 lb/sec) ASISI Overview

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