Astronomy1013:WritingC
Todate,therehavebeenanumberofin-classvideosshown,inordertoillustrate
keyconceptsandapproaches.Chooseoneofthosevideos(alllinkedfromthe
coursenotesonBB)andaddresseachofthefollowingquestionswithin(a)aclear
andconciseessay(~1page,single-spaced);OR(b)ashort(~5slide)PowerPoint
presentation.
1. Summarizethevideointhecontextofthecourse.Becertaintobequantitative.
2. Inwhatspecificwaysdoesthevideoaddressthecoreconceptsofscience(the
coreconceptsofscienceare…)?
3. Constructananalogyforhowscienceworksandusethechosenvideoto
illustrateyouranalogy.
4. Commentonwhatattractedyoutodiscussthatparticularvideo(e.g.“Ireally
enjoyedthisvideobecause…”OR“Thisvideoreallyannoyedmebecause…”).
Suggestspecificimprovements,particularlyimprovementsthatincreasethe
quantitativenatureofthevideo.
RubricforGradingWritingC
5Points 3Points 1Point 0Points
Summary
Clear,concise,
andrepresents
video;
quantitative
pointsandcourse
contextincluded
Lessclear,longer,
andmuddiesthe
pointofthevideo;
muddies
quantitativeaspect;
classcontextless
clear
Summary
wandersand
missesthe
pointofthe
video;no
quantitative
aspector
coursecontext
Nothing
submitted
CoreConcepts
Statedclearlyand
directlylinkedto
thevideo
Stated,butless
clearlylinkedtothe
video
Coreconcepts
muddy;poorly
linkedtothe
video
Nothing
submitted
Analogy
Seriousthought
foranalogy;
analogylinkedto
video
Partialanalogythat
partiallyworks;
weaklinktovideo
Pooranalogy
thatdoesnot
mimicthe
video;nolink
tothevideo
Nothing
submitted
Improvements
Commentsleadto
thoughtfulideas
toimprovevideo
Commentshelpful
butlessdirectedto
specificareasfor
improvement
Commentsdo
notaddress
specificareas
for
improvement
Nothing
submitted
Submitonpapertomeinclassby4thNovember2015.
Noelectronicsubmissionaccepted.
EGEE 430/ME 430
Introduction to Combustion
Fall 2015
Assignment #6
Chemical Kinetics
1. In a global, single-step mechanism for butane combustion, the reaction order with respect to butane is 0.15 and with respect to oxygen is 1.6. The rate coefficient can be expressed in Arrhenius form: the pre-exponential factor A is 4.16E09 (in SI units), and the activation energy EA is 125,000 kJ/kmol; the temperature exponent is equal to zero. What are the units of A? Write an expression for the rate of butane destruction, d[C4H10]/dt.
2. Using the results of problem 1, determine the numerical value of the volumetric mass oxidation rate of butane (in kg/m3-s) for a fuel-air mixture with an equivalence ratio of 0.9, temperature of 1200 K, and pressure of 1 atm.
3. Consider the four-step elementary reaction mechanism discussed in lecture and in the textbook for CO oxidation, in the case where there is water present. How many chemical rate equations are needed to determine the chemical evolution of a system defined by this mechanism? Write an expression for the time rate of change of hydroxyl radical concentration, in terms of rate coefficients and species molar concentrations. Consider each elemen ...
5. the reaction order with respect to butane is 0.15 and with
respect to oxygen is 1.6. The rate coefficient can be expressed
in Arrhenius form: the pre-exponential factor A is 4.16E09 (in
SI units), and the activation energy EA is 125,000 kJ/kmol; the
temperature exponent is equal to zero. What are the units of A?
Write an expression for the rate of butane destruction,
d[C4H10]/dt.
2. Using the results of problem 1, determine the numerical value
of the volumetric mass oxidation rate of butane (in kg/m3-s) for
a fuel-air mixture with an equivalence ratio of 0.9, temperature
of 1200 K, and pressure of 1 atm.
3. Consider the four-step elementary reaction mechanism
discussed in lecture and in the textbook for CO oxidation, in the
case where there is water present. How many chemical rate
equations are needed to determine the chemical evolution of a
system defined by this mechanism? Write an expression for the
time rate of change of hydroxyl radical concentration, in terms
of rate coefficients and species molar concentrations. Consider
each elementary reaction to be a reversible reaction.
4. The temperature and pressure of a mixture of gases can be
raised rapidly (effectively instantaneously) by passing a shock
wave through the mixture. See Example 4.4 in Turns 3rd
edition, for example. This is useful for studying chemical
kinetics, and can be simulated using CHEMKIN. Here we are
not interested in the physics of compressible flows, but rather in
the chemical kinetics that start after the shock wave passes
through the mixture, and continue until the system eventually
reaches steady state. The shock wave essentially sets the initial
pressure and temperature of the mixture to sufficiently high
values that the chemical reactions can begin to proceed at
nontrivial rates.
Here you are to use the GRI-Mech 3.0 chemical mechanism and
6. corresponding thermodynamic data. This is a state-of-the-art
chemical mechanism that has been developed for natural-gas
combustion, including detailed NOx chemistry (see
http://www.me.berkeley.edu/gri_mech/version30/text30.html
and Chapter 5 of Turns 3rd edition). Here we are interested
primarily in the NOx chemistry. The chemical mechanism file
(grimech3.0_chem.inp) and thermodynamic properties file
(grimech3.0_therm.dat) have been posted on ANGEL by the
instructor.
Follow the same general sequence of operations as you did in
earlier CHEMKIN assignments. Don’t forget to update/save at
appropriate steps in the process.
Tube Reactors.” It might be useful to have a look at the
corresponding CHEMKIN help files.
the “Pre-Processing” panel, specify the GRI-Mech 3.0
chemistry set given above.
o In the “Reactor Physical Properties” tab:
Correction.
egin Time = 0.0 s; End Time = 0.02 s (20 ms).
o In the “Reactant Species” tab, specify Initial Reactant
Fractions corresponding to standard engineering dry air: 21%
O2, 79% N2.
o Use the default tolerance values.
o Specify a Maximum Time Step Size of 0.001 s.
o Check the Output in Molar Concentration box.
7. o Specify a Time Interval for Printing and a Time Interval for
Saving
Solution
to be 0.001 s.
at the exercise, replacing a small amount of the N2 in
the Initial Reactant Fractions with H2O: 21% O2, 79% N2, 1%
H2O.
What are the initial pressure and temperature of the system
immediately after the shock wave passes through, in each case
(dry air, air with H2O)? Precise values can be found in the
output files.
How do the pressure and temperature vary with time after the
shock has passed through?
What are the final pressure and temperature of the system when
the system reaches steady state, in each case (dry air, air with
H2O)?
Comment on the differences that you observe between the dry
air case and the air with H2O case. Can you explain the
differences? Remember that NO and NO2 are the primary
pollutants of concern.
8. Attach the following plots for each of the two cases (dry air, air
with H2O):
Temperature and pressure (both on the same plot) versus time
Use different y-axis scales for T and p, so that the plot is
legible (see help files if you have trouble figuring out how to do
this)
Mole fractions versus time for all species present in >10-8 mole
fraction
This should be a very small subset of the 53 species in the
mechanism
Don’t put all species in one plot
Exercise judgment in how many species to include in each plot
Group species having similar mole fraction values in each plot
Use the same y-axis scale for all species on each plot
The plots must be legible
Attach the CHEMKIN output files for the two cases, edited to
remove the intermediate steps between the initial condition (t =
0.0 s) and the final solution (t = 0.02 s).
