Combustion reaction - discrepancy between hand calc. and computer sim

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SUMMARY

The discussion centers on the combustion reaction of C2H4O, where a hand calculation estimated a flame temperature of 945 K at 20 atm, while a combustion simulation yielded 1289 K. The discrepancy arises from the hand calculation's failure to account for product dissociation, which is influenced by pressure according to LeChatelier's principle. The participant questions whether a 36% difference is reasonable and seeks clarification on the role of equilibrium reactions and the initial state of the reactants in both calculations.

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  • Understanding of combustion thermodynamics
  • Familiarity with LeChatelier's principle
  • Knowledge of chemical equilibrium reactions
  • Experience using combustion simulation software
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  • Research the impact of pressure on combustion reactions
  • Learn about product dissociation in high-pressure environments
  • Explore the use of equilibrium calculation tools like the one from Colorado State University
  • Investigate the differences between hand calculations and numerical simulations in combustion analysis
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Chemical engineers, combustion researchers, and students studying thermodynamics and reaction kinetics will benefit from this discussion.

engineer23
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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?
 
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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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