(1) Thermal, Fluid System and Heat Transfer 2003. 5. 26.
Airplane
Airplane Design?
Gas Turbine Engine GE 90 Engine
Gas Turbine Engine
Schematic View of Gas Turbine Engine
T-s and P-v diagrams
Gas Turbine Brayton cycle 1-2: COMPRESSOR 2-3: COMBUSTER 3-4: TURBINE 4-1: HEAT REJECT Ideal Thermal Efficiency T 1 η = 1 T 3
Gas Turbine Brayton cycle T 3 Turbine inlet temperature T 2 T 1 s Maximum work T 2 = T1 T3
Variation of TIT over recent years : NEW COOLING CONCEPT 1600 FILM IMPINGEMENT CONVECTTION SIMPLE COOLING UNCOOLED TURBINES ALLOWABLE METAL TEMPERATURE
Turbine Blade Turbine Vane
Turbine Vane/Blade Film Cooled Blade/Vane Several rows of cooling holes Coolant Ejection Protect the Surface
Photos of Cross-section of Turbine Blades with Internal Cooling Passages
Rotor Blade Cooling Impingement Cooling Film Cooling Convective Cooling 7FA 501G Pin Fin / Slot Cooling
Turbine Blade Modeling Tube Flow Inside Tube (Cooling air) Tube wall Outside tube (Combustion gas)
Inside and Outside Tube Flows Forced flow in a tube Forced flow over a cylinder
Thermal Design? Q = h o A (T gas T wo ) Q = k A (T wo T wi ) / L Q = h i A (T wi T cool ) h i T wi
To Design Thermal Components? 1. Estimate h 2. Obtain a correlation equation Nu = hl / k = c Re m Pr n 3. Enhance h = 0.664 Re 0.5 Pr 0.333
Applications of ducts with ribs and pin-fin arrays Gas turbine internal cooling passages with ribs and pin-fin arrays
Modeling Internal Cooling Passage Internal cooling passages of turbine blades Break laminar sublayer, promote turbulence, improve flow mixing, induce various vortices Flow Augment heat transfer greatly (Additional friction loss penalty)
Design Parameters (1) - Rib Turbulators p α e Rib height and width Rib-to-rib pitch Rib angle of attack Rib arrangement Rib shape
Basic flow patterns and heat transfer (1) 4 - around the transverse ribs with rib angle = 90º Nu Nu 0 3 2 1 Recirculation Reattachment Re-developing boundary layer Separation e Rib Rib 0 2 4 6 8 10 vortex x/e vortex
Basic flow patterns and heat transfer (2) Secondary flows induced by angled ribs Secondary flow pattern Rib Parallel rib array Cross rib array Flow reattachments Rib Flow separation Path lines Kilm et al. (1999) Mainstream Mainstream Downward flow Flow Rotating secondary flow Upward flow
Flow patterns and heat transfer? Mainstream Rib turbulator Low heat transfer region 10.0 10.0 Flow 5.0 5.0 z/e 0.0-5.0 z/e 0.0-5.0 Steep gradient -10.0 30.0 35.0 40.0 45.0 50.0 55.0 x/e -10.0 30.0 35.0 40.0 45.0 50.0 55.0 x/e Potential hot spots, large thermal stress
Contour Plots of Nu/Nuo Flow 10.0 A90N1 5.0 10.0 A90N2 5.0 z/e 0.0 z/e 0.0-5.0-5.0 Flow z/e -10.0 30.0 35.0 40.0 45.0 50.0 55.0 10.0 A90N3 5.0 0.0 x/e z/e -10.0 30.0 35.0 40.0 45.0 50.0 55.0 10.0 A90N5 5.0 0.0 x/e 4.6 3.4-5.0-5.0 2.2-10.0 30.0 35.0 40.0 45.0 50.0 55.0 x/e -10.0 30.0 35.0 40.0 45.0 50.0 55.0 x/e 1.0
Thermal Design? Q = h i A (T wi T cool ) Q = 15 kw h i = 2000 w/ C m 2 A = pdl = 0.01 m 2 T cool = 700 K T i = 15,000/(2000)(0.01)+700 =1450 K h i = 15,000/(0.01)(1200-700) = 3000
Types of Gas Turbines
Fuel Cell
Small Gas Turbine - kw - - / Hybrid - -
Gas turbine Fuel cell Hybrid System : 800~1000 C (SOFC)
Hybrid System Gas turbine with Cycle improvement Gas turbine-fuel cell Hybrid system Gas turbine Combined cycle Advanced Turbine System Diesel and gas engine
Hybrid System
Micro Gas Turbine 1) (Battery ) : g : 10 g/hr ( ) 2) 1) 2)
Micro Gas Turbine Micro Gas Turbine (MIT) Dimension 12 mm OD 3 mm Combustor Temp. 1600 K Pressure ratio 4:1 Fuel consumption 7 gram/hr Rotor speed 2.4 10 6 rpm Weight 1 gram Air flow 0.15 gram/sec Power output 16 W
Four Forces on an Aircraft What forces are generated by fluid?
Drag and Lift Drag is the aerodynamic force in the direction of upstream velocity. Lift is the aerodynamic force normal to upstream velocity Drag and Lift are generated by the interaction and contact of a solid body with a fluid (liquid or gas).
Lift or Magnus Effects 1. Disaster of a Racing Car (PORSCHE) due to Lift
Lift or Magnus Effects 2. R. Carlos Free Kick Brazil vs France (1997)
Control Volume Analysis CVs (Control volumes) are artificial boundaries used to simplify analysis (similar to free body diagram in solid mechanics). CVs (open system) have porous surface (control surface), so mass can cross the boundary. Cf. Closed system (control mass): no mass crosses the boundary. CVs have solid characteristics. - Forces may act upon CV boundaries. - Forces may be exerted by CV boundaries. Examples Closed System Control Volume (a) simplified physical view (b) Isolated using a control volume
Examples of positive displacement machines Tire pump Human heart Gear pump Most positive displacement machines are used in hydraulic system.
Classification of Turbomachines Working fluid Liquids: pumps, hydro turbines Gases: compressors, fans, blowers, wind turbines, gas turbines Flow path Axial flow, mixed flow, radial flow turbomachines
Turbomachines and Supersonic Flow
Vortex
Flows around a Cylinder A: Re<<1 B: 4<Re<40 C: 40<Re<3*10 5 D: 3*10 5 <Re<5*10 5 E: 5*10 5 <Re
Inside and Outside Tube Flows Forced flow in a tube Forced flow over a cylinder Flow through a tube bank
Condenser
Heat Transfer Tube flow Inside Tube (refrigerant) Tube wall Outside tube (air, room) Condenser Evaporator
Pipes which have fins
Different boiling regimes Transition boiling Nucleate boiling Natural convection boiling Film boiling
Flow boiling in a tube
Two phase flow in a pipe (1) Two phase flow in a vertical circular pipe
Biomimetics - Glider(1889)
Biomimetics Wright Brother s Airplanes
Biomimetics - Aircraft wing
Aircraft wing
Aircraft wings leading & trailing edges
Airfoil Shape (NACA) - Trout
Upward deflected wing
Humming bird
MAVs using Flapping Wing
Reduction of Drag : Shark s Skin