This problem relates to oxy-fuel combustion - when a hydrocarbon fuel is burned in pure oxygen and the products consist of only carbon dioxide and water. Consider an oxy-fuel spark-ignition engine operating according to the ideal Otto cycle. We will only look at the constant volume combustion step of the cycle. To limit the maximum temperature of the cycle, pure carbon dioxide from the exhaust is cooled down to the ambient air temperature and used to dilute the fresh fuel-oxygen mixture. The fuel is liquid iso-octane (C3H18) and the engine operates at equivalence ratio of 0.9. The fuel-Oz-CO2 mixture enters the engine at ambient conditions and is compressed adiabatically to 18 atm and 530K. Assume that the reactants and products behave as ideal gases. The following species enthalpies are provided hat T=530K (KJ/mol) h, at T=3100K (KI/mol) CH3 CO2 H2O 02 -167.1 -383.9 -250.1 7.0 -234.4 -109.7 102.0 (A) Assuming complete combustion, what should the mole fraction of CO2 in the reactants be to limit the post-combustion temperature to 3100 K? What is the post- combustion pressure? (4)