SR-71 Inlet Design Issues And Solutions Dealing With Behaviorally Challenged Supersonic Flow Systems 3/4/14 Tom Anderson 1
A-12, SR-71 Inlet Designers Dave Campbell SR-71 Inlet Designer Propulsion Boss Ben Rich SR-71 Vehicle and Inlet Preliminary Design Propulsion Boss ADP President 2
SR-71 Inlet Document 3
SR-71 Nacelle Station 0 Station 2 Station 8 Station 9 4
Inlet Needed To Capture Ram Pressure Vehicle Velocity Mach Number Pram Pambient Pram-Pambient Pambient Car 70 miles per 0.1 Less than 1.01 Less than.01 hour Airliner 530 miles per 0.8 1.5.5 hour Fighter 1300 miles per 2.0 7.8 6.8 Max Speed hour SR-71 2130 miles per hour 3.2 49.4 48.4 A Figure Of Merit For Inlet Performance Is Recovery. Recovery Is The Amount Of Ram Pressure That Is Recovered From The Inlet Compression Process. Recovery = P t2 /P t0 5
Inlet Compression Regions Normal Shock A c Oblique Shocks A t Supersonic Diffuser Subsonic Diffuser 6
Inlet Configuration Definitions Spike Design Position Cowl Mice Struts Spike Translated Position Fixed Centerbody 7
Cowl Pressure Ratio ADP Inlet Cowl Pressure Distribution 20 16 12 8 Normal Shock 4 0 Normal Shock A c Oblique Shocks A t Supersonic Diffuser Subsonic Diffuser 8
Ptns/Pto Mach Number Flow Rate/Area ADP Supersonic Compression Ends With Normal Shock Sonic; M=1.0 Normal Shock A c Oblique Shocks A t Supersonic Diffuser Subsonic Diffuser Mach Number 9
Supersonic Compression Done Through Compression And Shock Waves 10
Basic Law Of Physics Continuity Everything That Enters The Inlet Must Leave Or Be Stored. The Inlet Does Not Act Like A Balloon And Will Not Store Air. Therefore Flow In Must Equal Flow Out. W in =W out = W engine + W bleed + W bypass + W leak Flow In Is Approximately 200 lbs/sec. Therefore Events Happen VERY Rapidly. 11
The Problem M o >1.0 M 2 <1.0 Subsonic Air Supersonic Air Skier Is Working Hard Skier Is Blind 12
Comparison Of Mo=3.2 Started And Unstarted Performance Inlet Started Recovery 80% Mass Flow 80% Oblique Shocks Normal Shock Oblique Shocks Normal Shock Inlet Unstarted Recovery 20% Mass Flow 20% 13
Inlet Flow Schlierens Show Started And Unstarted Operation Inlet Started Inlet Unstarted Ram Recovery = 0.8 Mass Flow Ratio = 0.8 Ram Recovery = 0.2 Mass Flow Ratio = 0.2 14
SR-71 Inlet Orientation Facing Into The Wind At Cruise 15
Nacelle Centerlines Engine Centerline Dd Inlet Centerline Inlet Cant Dd (Downward) Dd (Inboard) Preliminary 6.5 deg. 0 deg. Final 5.6 deg. 3.2 deg. 16
Forward Bypass Matches Inlet And Exit Airflow 17
Inlet Automatic Control System 18
Variable Geometry Is Required Mach Numbers Below Cruise Require Increased Throat Area. Internal Flow Areas Must Grow In Order To Restart The Inlet From An Unstarted Condition. Therefore Variable Area Internal Geometries Are Required. This is Accomplished On The SR-71 By Spike Translation. 19
Inlet Geometry And Area Distribution 80 20
Spike Translation Varies Inlet Area Distribution 21
Supersonic Diffuser Flow Field 22
SR-71 Inlet Bleed Regions 23
Cowl (Shock Trap) Bleed Flows To Nozzle 24
Centerbody (Porous) Bleed Flows Overboard Support Strut Spike Bleed Exit Louvers (4 Locations) Spike Bleed Exit Louver View Looking AFT Support Strut Spike Bleed (Slotted Surface) Engine Face Side View 25
Aft Bypass Flows to Nozzle 26
Inlet Geometric Features 27
Inlet Diffuser Photos 28
Nacelle Leakage Test Rig 29
Backup 30
Inlet Wind Tunnel Model 31
Inlet Airflow Paths 32
Inlet Airflow Paths 33
Inlet Airflows 34
Nacelle Thrust Distribution 35
Inlet Pressure Recovery 36
Mixed Compression Inlet Characteristics 37
Inlet Restart Cycle 38