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COMBUSTION ENGINEERING

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Presentation on theme: "COMBUSTION ENGINEERING"— Presentation transcript:

1 COMBUSTION ENGINEERING
PROF. SEUNG WOOK BAEK DIV. OF AEROSPACE ENGINEERING, KAIST, IN KOREA ROOM : 3304 TELEPHONE : 3714

2 BURNING OF A FUEL DROPLET IN AN OXIDIZED ATMOSPHERE
PROBLEMS HOW TO PRODUCE SPRAYS CHARACTERISTICS OF THE SPRAY BURNING RATE OF SPRAY? OXIDIZER PRESSURE AMBIENT TEMPERATURE EFFECTS OF MICRO EXPLOSION METAL PARTICLE SLURRY IGNITION PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

3 COMBUSTION ENGINEERING
DROPLET MAY INTERACT IF CLOSE TOGETHER GROUP COMBUSTION INDIVIDUAL DROPLET COMBUSTION EFFECT OF CONVECTION EFFECT OF BUOYANCY OXIDIZER FUEL BURNING OF AN INDIVIDUAL DROPLET FLAME SURFACE PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

4 COMBUSTION ENGINEERING
TYPICAL EXPERIMENTS EXCESSIVELY LARGE SIZE PRECLUSION OF TRANSIENT PHENOMENA QUARTZ FILAMENT DISTORTION HEAT LOSS SUSPENSION TECHNIQUE SUSPENDED DROPLET FUEL POROUS SPHERE (A) (B) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

5 COMBUSTION ENGINEERING
FREE FALLING DROPS ZERO g EXPERIMENTS FORCED CONVECTION (C) (D) BUOYANCY EFFECT (1) BURNING RATE IS INCREASED DUE TO ENHANCED TRANSPORT RATES (2) FLAME SHAPE IS SEVERELY DISTORTED: NOT MEANINGFUL TO IDENTIFY A FLAME DIAMETER PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

6 COMBUSTION ENGINEERING
IN (A) FOR STEADY BURNING (1) : SPHERE RADIUS IN (B) AND (C) AFTER AN INITIAL UNSTEADY PERIOD (2) : DROPLET DIAMETER : EVAPORATION CONSTANT(BURNING CONSTANT) LAW: ALSO VALID FOR PURE VAPORIZATION ANALYSIS DERIVATION OF EQUATION (2): PREDICTS BURNING RATE: FLAME SHAPES: TEMPERATURE AND CONCENTRATION PROFILES PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

7 COMBUSTION ENGINEERING
PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

8 COMBUSTION ENGINEERING
ASSUMPTION (1) SPHERICAL SYMMETRY (2) USE SINGLE STEP REACTION (3) Shvab-Zeldovitch FORMULATION (4) STEADY COMBUSTION (i) HEATING AND IGNITION PERIODS NEGLECTED (THE FLOW VARIABLES ARE CONSTANT INSIDE THE DROPLET) (ii) CHANGES AS DROPLET VAPORIZES: AT MOST USING QUASI STEADY THEORY PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

9 COMBUSTION ENGINEERING
BECAUSE OF THE SIGNIFICANT DENSITY DISPARITY BETWEEN LIQUID AND GAS, THE PROPERTIES AT THE DROPLET SURFACE SUCH AS THE REGRESSION RATE, SPECIES CONCENTRATIONS, AND TEMPERATURE IN LIQUID PHASE CHANGE AT RATES MUCH SLOWER THAN THOSE FOR THE GAS PHASE TRANSPORT PROCESSES (3) (4) IF (5) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

10 COMBUSTION ENGINEERING
THE BURNING RATE? (6) WILL BE AN EIGENVALUE OF (7) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

11 COMBUSTION ENGINEERING
COMBINE (6) AND (7) (8) ( IS INDEPENDENT OF r ) LET (9) (10) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

12 COMBUSTION ENGINEERING
IF (11) FROM (5) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

13 COMBUSTION ENGINEERING
CONSIDER THERMAL COUPLING FCN B.C. PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

14 COMBUSTION ENGINEERING
DROPLET SURFACE SPECIES CONSERVATION (GO TO APPENDIX) NO SURFACE REACTION INTERFACE IS NOT MOVING. NO EXCESS MASS AT SURFACE PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

15 COMBUSTION ENGINEERING
(12) FOR OXIDIZER (NO DISSOLUTION INTO DROPLET) USE (13) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

16 COMBUSTION ENGINEERING
INTERFACE CONDITION ON T FOR UNIFORM AND CONSTANT DROPLET TEMPERATURE (14) L = LATENT HEAT OF VAPORIZATION INTRODUCE PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

17 COMBUSTION ENGINEERING
(15) BY MAKING TERM INVOLVING DROPS OUT COMBINE RESULTS (13) & (15), (16) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

18 COMBUSTION ENGINEERING
APPLY FOR (17) (18) AS (19) (20) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

19 COMBUSTION ENGINEERING
(20) FROM DEFINITION OF (21) USING DEFINITION OF FROM EQUATION (20), (22) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

20 COMBUSTION ENGINEERING
DISCUSSION (EQUATION (22)) CAN BE VARIABLE DOES NOT DEPEND ON FLAME SURFACE APPROXIMATION ( : FLAME SURFACE APPROXIMATION) : BASIC FUEL PROPERTIES GENERALLY KNOWN : FOR BURNING DROPS : USUALLY KNOWN IF AMBIENT ATMOSPHERE IS SPECIFIED PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

21 COMBUSTION ENGINEERING
Tl IS DETERMINED BY THERMODYNAMIC CONDITION, SUCH THAT AT THE SURFACE = THEREFORE, WE NEED TO KNOW FREQUENTLY USED ONE IS Clausius-Clapeyron RELATION. : NORMAL ATMOSPHERIC PRESSURE & BOILING TEMPERATURE : PREVAILING PRESSURE FUEL BOILING TEMPERATURE, (GOOD APPROXIMATION) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

22 COMBUSTION ENGINEERING
(23) (24) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

23 COMBUSTION ENGINEERING
(25) (ACCURATE KNOWLEDGE OF Tb IS NOT ESSENTIAL) (SIMILARITY BETWEEN VAPORIZATION & COMBUSTION) B PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

24 COMBUSTION ENGINEERING
FROM EQUATION (5) (26) REMARKS INSENSITIVE TO PRESSURE, WEAKLY DEPENDENT ON TEMPERATURE PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

25 COMBUSTION ENGINEERING
OTHER CHARACTERISTICS OF BURNING DROPLETS SOLVED FOR 2nd ORDER EQUATIONS 3 B.C’s FLAME LOCATION? (27) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

26 COMBUSTION ENGINEERING
AS ASSUME AS (28) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

27 COMBUSTION ENGINEERING
AT DROPLET SURFACE, (29) BECAUSE OF AT DROPLET SURFACE, PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

28 COMBUSTION ENGINEERING
(20) (21) (28) (29) (30) COMBINE : (28), (29), (30) FOR UNKNOWNS SOLVE FOR (31) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

29 COMBUSTION ENGINEERING
CONCENTRATION PROFILE AND TEMPERATURE FLAME SURFACE APPROXIMATION AT FLAME PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

30 COMBUSTION ENGINEERING
PROFILES 1 PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

31 COMBUSTION ENGINEERING
(32) (27) WHEN (33) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

32 COMBUSTION ENGINEERING
ASSUME USE EXPRESSION FOR IF PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

33 COMBUSTION ENGINEERING
REMARK INDEPENDENT OF (DROPLET RADIUS) TOO LARGE BY A FACTOR OF 2 BECAUSE NATURAL CONVECTION IS NEGLECTED PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

34 COMBUSTION ENGINEERING
MODERN DEVELOPMENTS NOT SPHERICALLY SYMMETRIC, BUT MULTIDIMENSIONAL TRANSIENT EFFECTS IN SURFACE REGRESSION RATE AND INTERIOR DROPLET HEATING MULTICOMPOSITIONAL WITH VARYING VOLATILITIES DROPLET INTERACTIONS THERMODYNAMIC NON-IDEALITY: DISSOLUTION OF AMBIENT GA IN LIQUID DROPLET, REAL EQUATION OF STATE, REAL THERMODYNAMIC PROPERTIES PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

35 COMBUSTION ENGINEERING
APPENDIX CONDITION AT FLAME SURFACE AND THE NATURE OF THE FLAME SURFACE APPROXIMATION OXIDIZER FUEL ai = INTERFACE AREA v = VOLUME OF CONTROL VOLUME FROM Leibnitz RULE WITH USING PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

36 COMBUSTION ENGINEERING
MOTION OF THE C.V. USING DIVERGENCE RULE PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

37 COMBUSTION ENGINEERING
WHEN THE INTERFACE (C.V.) DOES NOT MOVE CONSERVATION OF SPECIES BECOMES (*) FOR i = F, (**) PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

38 COMBUSTION ENGINEERING
ALL FUEL FLOWING TOWARD THE FLAME FRONT + SIDE IS CONSUMED AT THE FLAME SURFACE FOR i = 0 (***) FOR SINGLE STEP CHEMICAL REACTION : RATE OF PRODUCTION PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

39 COMBUSTION ENGINEERING
DIVIDE (**) BY (***) BY AND SUBTRACT WHEN FUEL + OXIDIZER FLOW INTO FLAME FROM OPPOSITE SIDES IN STOICHIOMETRIC PROPORTIONS, AT FLAME PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

40 COMBUSTION ENGINEERING
CONCENTRATION GRADIENTS REMAIN FINITE AT THE FLAME DIFFUSION FLUX IN STOICHIOMETIC PROPORTIONS PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

41 COMBUSTION ENGINEERING
REMARKS TEMPERATURE? SOLVE FOR AND PRODUCT? SOLVE FOR AND BASIC PROPERTIES OF DIFFUSION FLAME ARE ESTABLISHED WITHOUT CONSIDERATION OF REACTION RATES I.E. CHEMICAL KINETICS PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING


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