Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
ME 525: Combustion Session 1 Today Course Administration Introduction: Applications and Fundamentals Outline Begin Review of Background material
Course Administration Instructor: Jay P. Gore firstname.lastname@example.org Teaching Assistants:Indraneel Sircar email@example.com Home Work:Ten Homework problems assigned with a one week to ten days gap – answers to be emailed to the instructor with copies to TA Instructor Office Visits: For one hour after class or by appointment Encourage Study Groups: Will be formed after review of student self-introductions. Submit names of up to 5 classmates you would like in your study group.
Student Self-Introductions Name and Email: . Degree Objective (Ph.D. or M. S.): . Advisor: . Research Topic: . Course Background:Circle the appropriate course numbers or the word equivalent and the word senior or the word grad • ME500 or ME300 or equivalent senior or grad thermodynamics • ME505 or ME315 or equivalent senior or grad heat transfer • ME509 or ME309 or equivalent senior or grad fluid mechanics • MA527 or MA 528 or equivalent senior or grad first year math • ME581 or equivalent senior or grad numerical methods • Names of five (or as many as you know) classmates who you would like in your study group
Grading • Two Midterm Examinations: 30% • Final Examination (Comprehensive): 30% • Text Book Home Work Problems: 20%. • Special Project(s): 20%.
Text Book • An Introduction to Combustion: Concepts and Applications, Third Edition, McGraw Hill by Stephen R. Turns • Download Software at www.mhhe.com/turns3e • Other software may need to be used for Homework problems and special problems • Study groups will have opportunity to share combustion related web links, combustion videos, interesting combustion related news items with Professor Gore for his screening, sharing with the class
Applications of Combustion • Power plants Coal, Diesel, Natural Gas • Manufacturing Mining and ore melting, combustion synthesis, heat treatment, boiling and purification. • Transportation: Air, Space, Land, Rivers, Sea, and Ocean Otto, Diesel, Rankine and Brayton cycles • HVAC and other Appliances • Fire Safety Forest, residential, automobile
Combustion Design Issues • Fuel for a given power rating efficiency, heat rejected, exhaust product composition • Oxidizer or air needed for a given power rating Mining and ore melting, combustion synthesis, heat treatment, boiling and purification. • Pollutants produced and their long term and short term impact • Cost of pollutant and pollution control • Pressure and temperature rise and control and containment design • Ignition, extinction, turndown, speed, pressure oscillation, noise, odor, and fire safety
Combustion Fundamentals- 1 • Combustion is an exothermic chemical reaction between a fuel and an oxidizer in which chemical energy stored in molecular bonds is released in the form of sensible energy. • Most fuels currently in use are hydrocarbon fossil fuels with coal being the most used and most criticized fuel. • Most oxidizer currently in use is oxygen from air. • Combustion products generally include CO2, H2O, CO, H2, N2, and excess O2. • Soot, unburned HC and NOx pressure oscillation, noise, and odor. • Combustion may involve material in solid, liquid, vapor and superheated gas state.
Stoichiometric Chemical Reaction • Generic fuel: CxHyOz , Molecular weight = (12x+y+16z) g/mol or kg/kmol. eg. CH4 and CH3OH • Molecular weight of CH4= 12.011+4*(1.00794) = 12.011+4.03176=16.04876 kg/kmol • Saves a lot of time and effort to make engineering assumption like: MWCH4 = 16 kg/kmol • CxHyOz + S (O2+ 3.76 N2) = xCO2 + y/2H2O + 3.76SN2 • S = moles of O2 from air needed for complete combustion of CxHyOz. • S=x+y/4-z/2. So for CH4, S=2; for generic paraffin CnH2n+2, S=n+(n+1)/2=1.5n+0.5; and for a generic paraffin alcohol CnH2n+1OH, S=n+(n+1)/2-1/2=1.5n • For Propane: S = 5; Propanol: C3H7OH, S = 4.5
Combustion Fundamentals - 2 • Fuel pyrolysisand vaporization must occur first for solid/liquid fuels. • Mixing at various length scales of the combustor, flow and molecular scales occurs next prior to the molecular scale chemical reaction. • If mixing promoted first and then ignition and flame stabilization is promoted, then a mode of combustion defined as premixed combustion prevails. • If mixing occurs simultaneously with ignition and reaction then a mode of combustion defined as non-premixed (diffusion) combustion prevails. • Combination of premixed and diffusion combustion prevails in flame stabilization region. • Flameless combustion may occur in certain devices.
Combustion Fundamentals - 3 • Combustion is an energy transfer process in which a portion of the stored molecular bond energy of a working substance (reactants taken together) is transformed into sensible energy of the chemically transformed working substance, transferred in the form of heat and/or work for useful purposes and/or transferred to another working substance as heat. • The properties of the working substance that typically change as a result of combustion include: • Internal energy: dus=cvdT, • enthalpy: dhs= dus+ vdP + Pdv=cpdT; • enthalpy including enthalpy change of state: dhs= dus+ vdP + Pdv + hfg • enthalpy including enthalpy change associated with chemical bonds • Nomenclature and units Us= sensible internal energy kJ us= specific sensible internal energy kJ/kg Hs = sensible enthalpy kJ hs = specific sensible enthalpy kJ/kg T = temperature, K
Combustion Fundamentals - 4 Nomenclature and units P = pressure or force per unit area kN or kN/m2 = kPA Us= sensible internal energy kJ us= specific sensible internal energy kJ/kg Hs = sensible enthalpy kJ hs = specific sensible enthalpy kJ/kg Hfg= enthalpy change associated with phase change kJ hfg = specific enthalpy change associated with phase change kJ/kg cv = constant volume specific heat, kJ/kg-K cP= constant pressure specific heat, kJ/kg-K HHV= Higher heating value of a fuel, kJ/kg. Energy removed after complete combustion of the fuel to products to bring the products to the same temperature as the reactants and associated condensation of the resulting water vapor. LHV= Lower heating value of a fuel , kJ/kg. Energy removed after complete combustion of the fuel to products to bring the products to the same temperature as the reactants but without condensation of the water vapor in the products.