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Tham khảo tài liệu 'mechanical engineers data handbook episode 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 140 MECHANICAL engineer s data handbook Mixture strength Ms x 100 R Weak mixture Ais 100 Rich mixture Afs 100 Therefore E - X 100 3.16.2 Combustion equations The following are the basic equations normally used for combustion processes. A table of elements and compounds is given. Carbon c O2 - CO2 2C O2 - 2CO Hydrogen 2H2 o2 - 2H2O Sulphur s o2 - SO2 Typical hydrocarbon fuels C4H8 6O2 - 4CO2 4H2O c h o 3O2 - 2CO2 3H2O Carbon with air assuming that air is composed of 79 nitrogen and 21 oxygen by volume 79. __79. c o2 ÝÝ N2 - CO2 Y N2 by volume __ 28x79. __ 28x79. 12C 32 o2 N2 - 44 co2 N2 by mass since the molecular weights of c o2 CO2 and N2 are 12 32 44 and 28. 3.16.3 Molecular weights of elements and compounds The molecular weights of elements and compounds used in combustion processes are listed in the table. Element Formula Approximate molecular weight Benzene C6H6 78 Butane C4H o 58 Carbon c 12 Carbon monoxide co 28 Carbon dioxide co2 44 Ethane c2h6 30 Ethanol c2h5oh 46 Ethene c2h 28 Hydrogen h 2 Methane ch4 16 Methanol ch oh 32 Nitrogen n2 28 Octane CbH18 114 Oxygen o2 32 Pentane c5h12 72 Propane c3h8 44 Propene cX 42 Sulphur s 32 Sulphur monoxide so 48 Sulphur dioxide so2 64 Water steam h2o 18 Engine exhaust and flue gas analysis If the analysis includes the H2O as steam produced by the combustion of hydrogen it is known as a wet analysis . Usually the steam condenses out and a dry analysis is made. 3.16.4 Solid and liquid fuels Let C c 1 H2 0 O2 n N2 S s all by mass. __ . . . . 2.67c 8 1 s-o Stoichiometric air fuel ratio R ----233------- If X 0.84c 0.3135s 0.357n 0.0728ER 27.4R y x 5 i using 0 for a stoichiometric air fuel ratio THERMODYNAMICS AND HEAT TRANSFER 141 Combustion products volume co2 h2o so2 o2 n2 Wet analysis 84- 500- _ s 31.3- 2-28 35.7n 274OK y y y 3 y Dry analysis 841 X 0 s 31.3- X 7.28EK 35.7n 2740R X X 3.16.5 Hydrocarbon fuels solid and liquid Weak mixture Let C c 1 H2 both by mass. _ 2.67c 8h Then R.- g - X-084 0.0728ẾR. 27.4R y X
