Università Degli studi di Napoli “Federico II” TESI DI DOTTORATO IN INGEGNERIA AEROSPAZIALE, NAVALE E DELLA QUALITÀ CICLO XIX Cloud Characterization in CIRA Icing Wind Tunnel Relatori Ch.mi: Matteo Bellucci Prof. Ing. G. M. Carlomagno Centro Italiano Ricerche Aerospaziali Prof. Ing. T. Astarita DETEC, Facoltà di Ingegneria Page 1 of 243 INDEX INTRODUCTION .................................................................................................................6 CHAPTER 1 ........................................................................................................................9 WHY AIRCRAFT ICING IS DANGEROUS .........................................................................9 1.1 ICING THREAT......................................................................................................................9 1.2 KINDS OF ICE .......................................................................................................................9 1.2.1 Clear (or Glaze) Ice....................................................................................................10 1.2.2 Rime Ice .....................................................................................................................11 1.2.3 Mixed Ice....................................................................................................................12 1.3 WHY THEY FALL: EFFECT OF ICE ACCRETION ON AIRCRAFT FLIGHT DYNAMICS...13 1.3.1 Performance Degradation.........................................................................................13 1.3.2 Aircraft Handling .......................................................................................................16 1.3.3 Airfoil sensitivity .......................................................................................................18 1.4 ICING RELATED ACCIDENTS............................................................................................20 CHAPTER 2 ......................................................................................................................25 THE ICING WEATHER .....................................................................................................25 2.1 MECHANISM AND COMPOSITION OF CLOUDS...............................................................25 2.2 COMPOSITION AND STRUCTURE OF THE ATMOSPHERE.............................................26 2.2.1 Composition of the Atmosphere ..............................................................................27 2.2.2 Structure of the Atmosphere ....................................................................................28 2.3 WATER CYCLES IN THE ATMOSPHERE ..........................................................................30 2.4 CLOUDS FORMATION........................................................................................................32 2.5 CLOUDS CLASSIFICATION ...............................................................................................32 2.5.1 High Clouds (Above 6 km, or 20,000 ft) ...................................................................34 2.5.2 Middle Clouds (2 to 6 km, or 6,500 to 20,000 ft) ......................................................34 2.5.3 Low Clouds (Below 2 km, Or 6,500 ft)......................................................................35 2.5.4 Clouds Of Vertical Development ..............................................................................36 2.6 ICING CLOUDS ...................................................................................................................37 2.6.1 Stratiform Clouds ......................................................................................................37 2.6.2 Cumuliform Clouds ...................................................................................................39 2.7 FRONTAL ICING CONDITIONS..........................................................................................40 CHAPTER 3 ......................................................................................................................42 ICE ACCRETION PHISICS...............................................................................................42 3.1 FORMATION OF ICE IN THE ATMOSPHERE ....................................................................42 3.2 SUPERCOOLED WATER DROPLETS ...............................................................................44 3.3 MECHANISM OF AIRCRAFT ICING ...................................................................................44 3.4 ICING VARIATIONS ............................................................................................................46 3.5 ICE GROWTH......................................................................................................................47 3.6 PRECIPITATION TYPE AND ICING....................................................................................50 CHAPTER 4 ......................................................................................................................53 Page 2 of 243 MAIN PARAMETERS IN AIRCRAFT ICING.....................................................................53 4.1 PHYSICAL FACTORS AFFECTING AIRCRAFT ICING......................................................53 4.2 ICING INTENSITY................................................................................................................53 4.3 LIQUID WATER CONTENT.................................................................................................55 4.4 TEMPERATURE..................................................................................................................58 4.5 DROPLET DIAMETER.........................................................................................................60 4.6 COLLECTION EFFICIENCY................................................................................................64 4.7 AIRSPEED...........................................................................................................................65 4.8 ICING MEASUREMENT INSTRUMENTS............................................................................66 CHAPTER 5 ......................................................................................................................67 ICING CERTIFICATION....................................................................................................67 5.1 AIRCRAFT CERTIFICATION ISSUES.................................................................................67 5.2 BASIC ASPECTS OF SAFETY ...........................................................................................69 5.3 ICE PROTECTION SYSTEM BASIC ISSUES .....................................................................71 5.4 CURRENT DESIGN ENVELOPES.......................................................................................73 CHAPTER 6 ......................................................................................................................79 ICING SIMULATION TOOLS............................................................................................79 6.1 BRIEF OVERVIEW OF THE AVAILABLE TOOLS..............................................................79 6.2 DIFFERENT SIMULATION TECHNIQUES..........................................................................81 6.3 GROUND FACILITIES.........................................................................................................83 6.3.1 Icing Wind Tunnels....................................................................................................84 6.3.2 Engine Icing Facilities...............................................................................................85 6.3.3 Low Velocity Facilities ..............................................................................................86 6.4 USE OF ICING SIMULATION TOOLS IN DESIGN AND CERTIFICATION.........................87 6.4.1 Current Simulation Capabilities ...............................................................................89 6.4.2 Limitation Of Current Simulation Methods..............................................................91 CHAPTER 7 ......................................................................................................................95 CIRA – ICING WIND TUNNEL..........................................................................................95 7.1 IWT OVERVIEW ..................................................................................................................95 7.2 WIND TUNNEL GENERAL DESCRIPTION.........................................................................99 7.2.1 Cooling Systems .....................................................................................................101 7.2.2 Air Plant ...................................................................................................................102 7.2.3 Fan System ..............................................................................................................103 7.2.4 Spray Bar System....................................................................................................104 7.2.5 Test Sections...........................................................................................................107 7.2.6 Engine Flow Simulator............................................................................................110 7.3 TEST EQUIPMENT............................................................................................................111