COMBUSTION TA : Donggi Lee PROF. SEUNG WOOK BAEK DEPARTMENT OF AEROSPACE ENGINEERING, KAIST, IN KOREA ROOM: Building N7-2 #3304 TELEPHONE : 3714 Cellphone : 010 - 5302 - 5934 swbaek@kaist.ac.kr http://procom.kaist.ac.kr TA : Donggi Lee ROOM: Building N7-2 #1304 TELEPHONE : 5754 Cellphone : 010 - 8504 - 5841 kingdonggi@kaist.ac.kr

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

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

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

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

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

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

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

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

COMBUSTION ENGINEERING IF PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

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

COMBUSTION ENGINEERING Tig IF PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

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

COMBUSTION ENGINEERING PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

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

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

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

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

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

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

COMBUSTION ENGINEERING ENERGY LET PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

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

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

COMBUSTION ENGINEERING PERFECT GASES OR PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

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

COMBUSTION ENGINEERING OR Rankine-Hugoniot RELATION PROPULSION AND COMBUSTION LABORATORY COMBUSTION ENGINEERING

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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: 0.5H2 + 0.5F2 → HF Kp = 15,800 0.5H2 + 0.5Cl2 → 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