# Combustion reaction - discrepancy between hand calc. and computer sim

• engineer23
In summary, there is a discrepancy between the hand calculation and computer simulation of the combustion reaction C2H4O (liquid) --> CO + 0.5CH4 + 0.5H2 + 0.25C2H4. The hand calculation did not take into account dissociation of products at higher pressure, which can lead to a higher flame temperature. However, the difference of 36% between the hand calculation and computer simulation may be too large. The reaction at equilibrium is 2CH4 --> 2H2 + C2H4, but it is unclear if this is factored into either calculation. Additionally, it is unclear if the computer simulation takes into account the starting liquid state or if it
engineer23
Combustion reaction -- discrepancy between hand calc. and computer sim

I am considering the reaction C2H4O (liquid) --> CO + 0.5CH4 + 0.5H2 + 0.25C2H4
I calculated the flame temperature when the reactant is at 298 K and 20 atm using H(reactants) = H(products) to get Tfinal = 945 K.
I then used a combustion software package and got a flame temp. of 1289 K.

By LeChatelier's principle, it makes sense that dissocation of products decreases with increasing pressure (as the equilibrium shifts toward the reacants). My hand calculation did not take dissociation into account -- less dissociation at higher pressure means a higher flame temperature. But 36% higher? Is this reasonable or too large a discrepancy between simple hand calculation and the direct numerical sim?

The reaction at equilibrium is 2CH4 --> 2H2 + C2H4. Does this figure into the hand calc. or computer calc. somehow?

Does the computer calculation take into account that you start of with a liquid? Was it constant pressure combustion which program did u use to model?

I always like this program http://navier.engr.colostate.edu/tools/equil.html to do equil calculations with however I could not get a result for the above reaction maybe you have more luck.

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## 1. What is a combustion reaction?

A combustion reaction is a type of chemical reaction that occurs when a substance reacts with oxygen to produce heat and light. This process is also known as burning and is a common way for energy to be released from fuel sources.

## 2. What is the discrepancy between hand calculations and computer simulations in combustion reactions?

The discrepancy between hand calculations and computer simulations in combustion reactions is due to the complexity and variability of real-world conditions. Hand calculations often use simplified models that do not take into account all the factors that can affect a combustion reaction, while computer simulations can incorporate more variables and provide more accurate predictions.

## 3. Why is it important to understand the discrepancy between hand calculations and computer simulations in combustion reactions?

Understanding the discrepancy between hand calculations and computer simulations in combustion reactions is important for accurately predicting and controlling the outcome of these reactions. This knowledge can also help improve and refine computer simulation models to better reflect real-world conditions.

## 4. How can the discrepancy between hand calculations and computer simulations in combustion reactions be minimized?

The discrepancy between hand calculations and computer simulations in combustion reactions can be minimized by using more advanced and accurate computer simulation models, as well as incorporating more variables and real-world conditions into the calculations. It is also important to validate the simulation results with experimental data.

## 5. What are some factors that can contribute to the discrepancy between hand calculations and computer simulations in combustion reactions?

Some factors that can contribute to the discrepancy between hand calculations and computer simulations in combustion reactions include the presence of impurities in the fuel, incomplete mixing of fuel and oxygen, and heat transfer effects. Other factors include variations in temperature, pressure, and flow rates, as well as the presence of catalysts and other substances that can affect the reaction.