Explanation Express the theoretical combustion equation of octane with stoichiometric amount of air. C 8 H 18 ( g ) + a th ( O 2 + 3.76 N 2 ) → 8 CO 2 + 9 H 2 O + 3.76 a th N 2 (I) Here, octane gas is C 8 H 18 , stoichiometric coefficient of air is a th , oxygen is O 2 , nitrogen is N 2 , carbon dioxide is CO 2 and water is H 2 O . Express the stoichiometric coefficient of air by O 2 balancing. a th = 8 + 4.5 = 12.5 Substitute 12.5 for a th in Equation (I). C 8 H 18 ( g ) + 12.5 ( O 2 + 3.76 N 2 ) → 8 CO 2 + 9 H 2 O + 3.76 × 12.5 N 2 C 8 H 18 ( g ) + 12.5 ( O 2 + 3.76 N 2 ) → 8 CO 2 + 9 H 2 O + 47 N 2 (II) Express the heat transfer from the combustion chamber. − Q ¯ out = ∑ N P ( h ¯ f o + h ¯ − h ¯ o ) P − ∑ N R ( h ¯ f o + h ¯ − h ¯ o ) R = ∑ N P ( h ¯ f o + h ¯ 1000 K − h ¯ 298 K o ) P − ∑ N R ( h ¯ f o ) R (III) Here, number of moles of products is N P , number of moles of reactants is N R , enthalpy of formation is h ¯ f . Express total mole numbers initially present in the combustion chamber from ideal gas relation. N 1 = P 1 ν 1 R a T 1 (IV) Here, initial pressure is P 1 , initial volume is ν 1 , universal gas constant of air is R a and initial temperature is T 1 . Express the amount of moles of octane burned. N C 8 H 18 , burned = N 1 1 + 12.5 N air (V) Here, number of moles of air is N air . Express the heat transfer from the combustion chamber during this process. Q out = N C 8 H 18 , burned Q ¯ out (VI) Conclusion: Refer Equation (II), and write the number of moles of products. N P , CO 2 = 8 kmol N P , H 2 O = 9 kmol N P , N 2 = 47 kmol Here, number of moles of product carbon dioxide, water, and nitrogen is N P , CO 2 , N P , H 2 O , and N P , N 2 respectively. Refer Equation (II), and write the number of moles of reactant. N R , C 8 H 18 = 1 kmol Here, number of moles of product octane is N R , C 8 H 18 . Perform unit conversion of temperature at state 1 from degree Celsius to Kelvin. T 1 = 25 °C = ( 25 + 273 ) K = 298 K Refer Appendix Table A-18, A-19, A-20, A-23 and A-26 and write the property table for products and reactants as in Table (1)

8th Edition

ISBN: 8220100257056

Author: CENGEL

Publisher: YUZU

See similar textbooks

Concept explainers

Properties of Pure Substances

A substance with fixed chemical composition throughout is called a pure substance like water, air, and nitrogen. A pure substance does not have to be a single element or compound. A mixture of two or more phases of a pure substance is also a pure substan…

Videos

Question

Chapter 15.7, Problem 68P

To determine

The heat transfer from the combustion chamber during this process.

Expert Solution & Answer

Want to see the full answer?

Check out a sample textbook solution

See solution

Chapter 15.7, Problem 67P

Chapter 15.7, Problem 69P

Students have asked these similar questions

Liquid propane (C3H8) enters a combustion chamber at 25°C at a rate of 0.05 kg/min where it is mixed and burned with 50 percent excess air that enters the combustion chamber at 7°C. An analysis of the combustion gases reveals that all the hydrogen in the fuel burns to H2O but only 90 percent of the carbon burns to CO2, with the remaining 10 percent forming CO. If the exit temperature of the combustion gases is 1500 K, determine 1-The balanced chemical equation for the actual process 2-Air- Fuel ratio 3-The mass flow rate of air

Using Hess' Law, calculate for the heat of combustion of a 1.5 liter propene (C3H6) at 14.5 psi and 80.6°F that is completely burned in air. Assume that all the water produced during the reaction is in liquid state. The standard enthalpy of formation of propene, C3H6 is +20.6 kJ/mol. The heats of formation of CO₂(g) and H₂O(l) are -394 kJ/mol and -285.8 kJ/, respectively.

Octane gas (C8H18) and atmospheric air are supplied to a combustion chamber at 25°C at the stoichiometric air/fuel ratio. The combustion takes place adiabatically under steady-flow condition. The change in velocity and the work transfer can be assumed negligible. The Enthalpy of Combustion of octane gas at 25°C is – 5,116,180 kJ/kmol (when H2O in the combustion products is in vapor phase). Determine with aid of the Table on Page 26, the final temperature of the combustion products.

Chapter 15 Solutions

EBK THERMODYNAMICS: AN ENGINEERING APPR

Ch. 15.7 - How does the presence of N2 in air affect the...Ch. 15.7 - Prob. 2P Ch. 15.7 - Prob. 3P Ch. 15.7 - Is the airfuel ratio expressed on a mole basis...Ch. 15.7 - Prob. 5P Ch. 15.7 - Prob. 6P Ch. 15.7 - Prob. 7P Ch. 15.7 - What does 100 percent theoretical air represent?Ch. 15.7 - Consider a fuel that is burned with (a) 130...Ch. 15.7 - Are complete combustion and theoretical combustion...

Knowledge Booster

Learn more about

Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.

The heat transfer from the combustion chamber during this process.

Solution Summary: The author explains the theoretical combustion equation of octane with stoichiometric amount of air.

Concept explainers

Videos

The heat transfer from the combustion chamber during this process.

Want to see the full answer?

Chapter 15 Solutions