1. COMBUSTION TA : Donggi Lee PROF. SEUNG WOOK BAEK
DEPARTMENT OF AEROSPACE ENGINEERING, KAIST, IN KOREA
ROOM: Building N7-2 #3304
TELEPHONE : 3714
Cellphone :
TA : Donggi Lee
ROOM: Building N7-2 #1304
TELEPHONE : 5754
Cellphone :

2. COMBUSTION ENGINEERING
C. IGNITION
1) THERMAL IGNITION
EXTERNAL SOURCE OF HEATING
REACTIVE HEAT GENERATION EXCEEDS LOSS RATE
RAPID INCREASE IN REACTION RATE AND TEMPERATURE
2) CHEMICAL CHAIN IGNITION
OCCURS WHEN CHAIN CARRIERS AND CHAIN REACTIONS ARE INVOLVED.
CAN OCCUR IN ISOTHERMAL CONDITIONS
RADIATION OF PROPER WAVELENGTH CAN GENERATE CHAIN CARRIERS WHICH RESULT IN IGNITION
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

4. COMBUSTION ENGINEERING
3) TYPE OF IGNITION
SPONTANEOUS IGNITION OCCURS WHEN COMBUSTIBLE MIXTURE IS RAISED IN TEMP E.G. : DIESEL ENGINE CYLINDER
FORCED IGNITION: DUE TO LOCAL ENERGY SOURCE-SPARK
DETONATION
COLD FUEL+OXIDIZER MIXTURE
HIGH T REGION
IGNITION AND COMBUSTION
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

5. COMBUSTION ENGINEERING
QUESTIONS :
(1) UNDER WHAT CONDITION DOES IGNITION OCCUR?
(2) WHAT IS “IGNITION DELAY” I.E. TIME BETWEEN INITIAL TEMPERATURE RISE AND IGNITION?
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

6. COMBUSTION ENGINEERING
SPONTANEOUS IGNITION AND IGNITION DELAY T0
V T S
SURFACE AREA: S VOLUME : V ENERGY CONSERVATION
A MINIMUM REQUIREMENT FOR SPONTANEOUS IGNITION
CONSIDER ADIABATIC SPONTANEOUS IGNITION
CONSIDER A PERFECT GAS
, USE FOR SECOND ORDER REACTION
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

7. COMBUSTION ENGINEERING
ENERGY EQUATION
IN TERMS OF DENSITY,
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

8. COMBUSTION ENGINEERING
IN GENERAL FORM
Area tig
Tig
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

9. COMBUSTION ENGINEERING
Reactants exhausted
Rapid combustion
QUANTITATIVE ANALYSIS
DEFINITION OF tig
FOR INSTANCE
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

10. COMBUSTION ENGINEERING
APPROXIMATIONS
ADIABATIC IGNITION DELAY
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

11. COMBUSTION ENGINEERINGIF
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

12. COMBUSTION ENGINEERING
REMARKS)
FOR HC’S
PROVIDED THAT , CHOICE OF Tig, HAS ONLY A SMALL EFFECT ON tig
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

13. COMBUSTION ENGINEERING
Tig IF
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

14. COMBUSTION ENGINEERING
VARIOUS FORMS FOR
ARRHENIUS TERM IS MAIN FEATURE FOR MOST FUELS.
COMMENTS
EFFECT OF ;
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

15. COMBUSTION ENGINEERING
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

16. COMBUSTION ENGINEERING
CAN USE THIS GRAPH TO FIND ACTIVATION ENERGY
ACTUALLY,
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

17. TREATMENT OF COMBUSTION WAVES AS A DISCONTINUITY
STATIONARY COMBUSTION WAVE ρ1 U1 P1 T1 ρ2 U2 P2 T2
CHEMICAL REACTION
MASS DIFFUSION
THERMAL CONDUCTION
VISCOUS EFFECTS
REACTANTS
PRODUCTS x
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

18. COMBUSTION ENGINEERING
ASSUMPTIONS
1) STEADY,ONE DIMENSIONAL FLOW
2) AT FAR-UPSTREAM AND FAR-DOWNSTREAM, IT BECOMES
(UNIFORM FLOW)
3) NO EXTERNAL FORCES
4) NEGLECT THERMAL AND PRESSURE DIFFUSION
CONSERVATION EQUATIONS
MASS
= MASS FLOW PER UNIT AREA
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

19. COMBUSTION ENGINEERING
MOMENTUM : 1-D NAVIER STOKES EQUATION
INTEGRATE
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

20. COMBUSTION ENGINEERING
ENERGY EQUATION
INCLUDES THE FORMATION ENERGIES.
: DIFFUSION VELOCITY
HOWEVER
AT (1) AND (2)
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

21. COMBUSTION ENGINEERING
INTEGRATE
AT (1) AND (2)
ENERGY INCLUDES CHEMICAL ENERGY.
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

22. COMBUSTION ENGINEERING
ENERGY
LET
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

23. COMBUSTION ENGINEERING
LET
ENERGY EQUATION BECOMES
COMBINING MASS AND MOMENTUM
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

24. COMBUSTION ENGINEERING
Slope
(1)
Rayleigh
FINAL STATE(2) ON THIS LINE
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

25. COMBUSTION ENGINEERING
PERFECT GASES OR
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

26. COMBUSTION ENGINEERING
(A) SUPPOSE
THEN,
SUPERSONIC DETONATION WAVE
SHOCK INDUCED REACTION FRONT
(B) SUPPOSE
THEN,
SUBSONIC
DEFLAGRATION WAVE
NOW INTRODUCE ENERGY EQUATION TO CONSIDER HEAT ADDITION
(h ; SENSIBLE ENTHALPY)
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

27. COMBUSTION ENGINEERINGOR
Rankine-Hugoniot RELATION
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

28. COMBUSTION ENGINEERING
USE OR
ANOTHER FORM OF R-H
EQUATION OF STATE OR
SAY THAT Q = Constant
DETERMINE THE LOCUS OF ALL POSSIBLE END STATES FOR GIVEN INITIAL CONDITIONS USING R-H AND EQUATION OF STATE
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

29. COMBUSTION ENGINEERING
Hugoniot Curve
C-J
STRONG DETONATION
DETONATION BRANCH
WEAK DETONATION
PHYSICALLY IMPOSSIBLE
WEAK DEFLAGRATION
DEFLAGRATION BRANCH
STRONG DEFLAGRATION
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

30. COMBUSTION ENGINEERING
CONSIDER THE Chapman-Jouguet POINTS
AT C-J : Rayleigh LINE IS TANGENT TO Hugoniot CURVE
FOR A SMALL CHANGE NEAR THE C-J POINT
FROM R-H RELATION
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

31. COMBUSTION ENGINEERING
NEAR A C-J POINT, ENTROPY CHANGE IS ZERO FOR A SMALL CHANGE.
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

32. COMBUSTION ENGINEERING
ENTROPY IS A MAXIMUM OR MINIMUM.
FOR DETONATION : C-J POINT IS MINIMUM
FOR DEFLAGRATION : C-J POINT IS MAXIMUM
(1S)
C-J
(2)
ISENTROPIC
(1)
(1)
C-J
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

33. COMBUSTION ENGINEERING
AT C-J POINT : ISENTROPIC PROCESS
WHERE
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

34. COMBUSTION ENGINEERING
AT C-J POINT : VELOCITY OF BURNT GASES
RELATIVE TO THE WAVE IS SONIC
I.E.
1-A, CONSTANT VOLUME DETONATION
FROM
1-B, WEAK DETONATION : IMPOSSIBLE
(ENTROPY DECREASES)
1-C, STRONG DETONATION : POSSIBLE
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

35. COMBUSTION ENGINEERING
1-C-J, COMMON DETONATION
1-D, CONSTANT PRESSURE DEFLAGRATION
1-C-J, C-J DEFLAGRATION : NEVER REALIZED
CHEMICAL KINETICS ARE NOT SO FAST TO SUPPORT FAST VELOCITY
1-E, STRONG DEFLAGRATION : IMPOSSIBLE
ENTROPY DECREASES
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

36. COMBUSTION ENGINEERING
APPROACH TO CLASSIFICATION OF COMBUSTION WAVES
NOW WE’LL ELIMINATE THE THERMODYNAMIC PROPERTIES.
ASSUME PERFECT GASES,
AND CONSTANT MOLECULAR WEIGHT
FOR MASS
(1)
R IS ELIMINATED, BECAUSE MOLECULAR WEIGHT IS CONSTANT.
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

37. COMBUSTION ENGINEERING
FOR MOMENTUM
(2)
FOR ENERGY
(3)
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

38. COMBUSTION ENGINEERING
ELIMINATING FROM (1), (2) AND (3)
LET’S
NOW DEFINE,
SUBSTITUTE,
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

39. COMBUSTION ENGINEERING
WHERE,
INCREASES WITH HEAT ADDITION.
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

40. COMBUSTION ENGINEERING
VARIOUS COMBUSTION WAVES
a b,
SHOCK WAVE
a b c,
STRONG DETONATION
a b d, C-J DETONATION
a b c e, WEAK DETONATION
c e, IMPOSSIBLE
ENTROPY DECREASES
a e,
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

41. COMBUSTION ENGINEERING
CHEMICAL KINETICS & TRANSPORT PHENOMENA ARE NOT SO FAST TO ADD HEAT TO GAS, SO IT DOES NOT OCCUR.
bw-cw, WEAK DEFLAGRATION
b-d, C-J DEFLAGRATION
b-c-e, STRONG DEFLAGRATION
IMPOSSIBLE: VIOLATE ENTROPY
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

42. COMBUSTION ENGINEERING
HW P393: #29, #30, #32
PROPULSION AND COMBUSTION LABORATORY
COMBUSTION ENGINEERING

43. Homework #2 (from Kanury, P393 #29, #30, #32)
PCI5 decomposes into PCI3 and Cl2 at elevated temperatures. If for PCl5 ⇔ PCI3 + Cl2 at 250 ℃, Kp is given as 1.78, at what pressure should the system be operated in order to obtain a 50% decomposition at 250 ℃?
Let C dissociate into A and B according to C ⇔ A + B. If λ is degree of decomposition and P is total pressure, Kp is a function of λ and P. In other words, while Kp is a function of temperature T at which the system is operated, so is also P for obtaining any desired conversion. Eliminating T from the two relations, for any desired degree of dissociation, Kp can be related to P. If the desired λ is 0.25, find this relation for the above reaction.
In a vessel containing a mixture of H2, F2 and Cl2, fluorine and chlorine compete with each other for hydrogen to form HF and HCl by the following reactions:
0.5H F → HF Kp = 15,800
0.5H Cl2 → HCl Kp = 51.2
Are we more likely to observe more HF than HCl or vice versa if the total pressure is 1 atm?
at 3,500K