b. Balancing Reactions: A number of combustion problems involve simply balancing the overall chemical reaction. All combustion daemons  have the Reaction Panel as the default panel as shown in Fig. 1 below. The I/O Panel contains instructions for using the Reaction Daemon.

The local control panel contains an Action Menu with a number of action items such as Balance Reaction, Initialize, Theoretical Air, etc.

Below the control panel, there are three blocks of variables where the reactants - fuels and oxidizers -  and the products are specified. Notice that the default choice of oxidizer is air and that of products are CO2, H2O(g) and N2. 

To illustrate some of the frequently used features, suppose we are interested in the theoretical (stoichiometric) reaction between methane and air. Choose CH4 from the species menu of the fuel block.  Simply choose Theoretical Air from the Action Menu and the reaction gets balanced. 1 kmol of CH4 reacts with 9.52 kmol of air - 1 kmol of air is treated as a mixture of 0.21 kmol of O2 and 0.79 kmol of N2 - producing 1 kmol CO2, 2 kmol H2O and 7.52 kmol N2. The air fuel ratio appears on the Message Panel. To know the breakup of air between O2 and N2, choose Air->O2,N2 and the oxidizer panel now contains the amount of O2 and N2 in kmols. 

Click on the Mass button and all the kmols are converted to the mass basis (kg or lbm depending on the choice of units, SI or English). The reaction is now expressed in terms of 16 kg of CH4. To convert it to the basis of 1 kg of CH4, choose Normalize from the Action Choice. 

To balance a reaction with known amount of excess or deficient air, enter the percent excess air (or deficient air) in the InputParameter widget and choose Excess Air from the Action Choice. Notice that the daemon automatically posts left over oxygen on the products panel. Remember that in a reaction where a fuel reacts with 300% theoretical air, the excess air is only 200%. 

Suppose we would like to balance a reaction between 1 kmol of CH4 and 5 kmol of O2 producing CO2, H2O and O2. Super-init all the panels (note the default species), choose CH4 as the fuel, enter 1 kmol by clicking the check box, get rid of Air as the oxidizer by clicking the Air checkbook twice, choose O2 as oxidizer, enter 5 kmol as the O2 amount, choose O2 as an additional product of the reaction, and select Balance Reaction. 
The same method can be used if the amounts are known in terms of species mass. 

For ideal (therefore,  perfect) gases, species volumes are proportional to the corresponding molal amount. If a volumetric product analysis is given, the same method can be used for balancing the reaction (see the Applications section).

To evaluate chememical properties of a gas mixture, the mixture can be set up (with masses or moles specified) as a products mixture. In that case the mixture composition can be read using Read As Is item in the Action Menu.

On the States panel (Fig. 2), State-1, 2 and 3 are keyed to  Fuel, Oxidizer and Products mixtures respectively. For example, if you select State-2, Oxidizer is also automatically selected. Notice that the properties  m or mdot   and M are posted based on the reaction (or mixture) specified on the Reaction Panel. Enter the known properties (p, T, etc.) and 
Calculate a state in the same manner as with any State Daemon.  The default amount of mass ( m or mdot ) can be overwritten if necessary. Starting with Version 7.0 the combustion daemon supports aglebraic equations; for instance, one can write h3 as '=(m1*h1+m2*h2)/(m1+m2)' for evaluation of the adiabatic flame temperature.

For steady flow combustion chambers (steady flow combustion daemon), generally, p1=p2=p3. Notice that kinetic energy need not be assumed negligible in order to evaluate the states completely.

For the closed process daemons, separate evaluation of  fuel and oxidizer states may require use of partial pressure or partial volume. For instance, supppose methane is kept in a rigid container with theoretical amount of air. The Reaction Panel produces the following result: 1 kmol methane reacts with 9.524 kmol of Air for a theoretical reaction. If the total pressure is 100 kPa, then p1= 100*1/10.524, the partial pressure of methane and p2= 100=p1. On the other hand, if the total volume is known, say 10 m^3, then Vol1=10*1/10.524 and Vol2=10-Vol1.

Using expressions such as =(m1*h1+m2*h2)/(m1+m2) for h3 one can directly evaluate the adiabatic flame temperature T3. Similarly, isentropic state can also be evaluated (say, for a nozzle in which complete combustion reactions takes place). Use of the Process or Device Panel makes it easier to analyze the complete system.

c. Process/Device Panel: On the Process Panel , there are two begin states -   bA- and bB-States  and a single finish or f-State . Load the completely or partially evaluated states. Enter the known values of Q and/or W and calculate. Super-Calculate to update all the answers. For the calculation of adiabatic flame temperature, for instance, Q=W=0 and T3 is calculated as e3 is evaluated from the energy equation (see the custom equation on the Process Panel, Fig. 3) and posted back to State-3. 

The Device Panel of the steady state combustion daemon work in a similar fashion. There are two inlet states for Fuel and Oxidizer -   i1- and i2-States   and a single exit or e-State . Load the completely or partially evaluated anchor states. For an isentropic device with no work output (say, a  nozzle) enter Qdot=Wdot_ext=Sdot_gen=0. Super-Calculate to completely evaluated the states including Vel3, which may be the desired unknown. 

c. I/O Panel: On the I/O Panel you can enter expressions such as =m1*h1+m2*h2-m3*h3 to evaluate the heat of combustion, for instance. In addition the Panel recongnizes any algebraic expression using the Microsoft Excell format. Super-Calculate produces a detailed output for the recently calculated solution on this panel. 
 

d. Parametric Study: The Super-Calculate buttons updates all calculations. So, after evaluating a desired quantity, say, the adiabatic flame temperature, the solution can be repeaed for a different fuel quite easily. Simply uncheck the fuel in the Reaction Panel, select the new fuel(s) and Super-Calculate. The new reaction will be balanced using the action displayed on the Action Menu, all states and analyses will be repeated and a new value of T3 will be found. 

f. Presence of Solids or Liquids: The fuel mixture can cotain liquid or even solid speicies. The products may contain liquid form of H2O. In a mixture that contains gases and solids/liquids, the volume occupied by the condensed phase is neglected.

g. Mixture Properties: A mixture of up to eight species can be created in the Reaction Panel as products. The amounts can be specified in mass or molar basis. Using the Read As Is item in the Action Menu, the mixture can be read in. In the  States Panel states 3, 4... etc. can be used to model the products mixture. The Gibb's function g  for the mixture is also evaluated as part of the state.

h. Your Input: The examples in the Applications section will help you get started. If you notice any inconsistency or error, or would like a particular aspect of the daemon explained a bit further, do not hesitate to write to the author using the Comments page.