{"id":2264,"date":"2024-08-04T21:23:26","date_gmt":"2024-08-04T21:23:26","guid":{"rendered":"https:\/\/workhouse.sweetdishy.com\/?p=2264"},"modified":"2024-08-04T21:23:26","modified_gmt":"2024-08-04T21:23:26","slug":"thermodynamics-of-combustion","status":"publish","type":"post","link":"https:\/\/workhouse.sweetdishy.com\/index.php\/2024\/08\/04\/thermodynamics-of-combustion\/","title":{"rendered":"Thermodynamics of Combustion"},"content":{"rendered":"\n<h3 class=\"wp-block-heading\"><strong>Properties of Mixtures<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The thermal properties of a pure substance are described by quantities including internal energy,&nbsp;<em>u<\/em>, enthalpy,&nbsp;<em>h<\/em>, specific heat,&nbsp;<em>C<\/em><em><sub>p<\/sub><\/em>, etc.<\/li>\n\n\n\n<li>Combustion systems consist of many different gases, so the thermodynamic properties of a mixture result from a combination of the properties of all of the individual gas species.<\/li>\n\n\n\n<li>The ideal gas law&nbsp;is assumed for gaseous mixtures, allowing the ideal gas relations to be applied to each gas component.<\/li>\n\n\n\n<li>Thermodynamic properties can be defined as either&nbsp;mass basis or mole basis<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image\"><a href=\"https:\/\/1.bp.blogspot.com\/-1NBfn_mtv6w\/Xs3eSqKLxLI\/AAAAAAAAMS0\/d349XRbrxbkAaOTwholWbZYwuxIH_ockgCK4BGAsYHg\/Mixture_Properties.jpg\"><img decoding=\"async\" src=\"https:\/\/1.bp.blogspot.com\/-1NBfn_mtv6w\/Xs3eSqKLxLI\/AAAAAAAAMS0\/d349XRbrxbkAaOTwholWbZYwuxIH_ockgCK4BGAsYHg\/w640-h195\/Mixture_Properties.jpg\" alt=\"\"\/><\/a><\/figure>\n\n\n\n<p><strong>For more details click here:<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><em><a href=\"https:\/\/chem.libretexts.org\/Bookshelves\/General_Chemistry\/Map%3A_Chemistry_-_The_Central_Science_(Brown_et_al.)\/10%3A_Gases\/10.6%3A_Gas_Mixtures_and_Partial_Pressures\" target=\"_blank\" rel=\"noreferrer noopener\">Gas Mixtures and Partial Pressures<\/a><\/em><\/li>\n\n\n\n<li><em><a href=\"https:\/\/www.informit.com\/articles\/article.aspx?p=2436662&amp;seqNum=6\" target=\"_blank\" rel=\"noreferrer noopener\">Basic of Volume Fraction and Mole Fraction<\/a><\/em><\/li>\n<\/ol>\n\n\n\n<p><em>Note: Refer to the book of \u201c<a href=\"https:\/\/cfdflowengineering.com\/references\/\">Thermodynamic\u201d for mixture properti<\/a>es in reactive flows<\/em><\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>&nbsp;Combustion Stoichiometry<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>&nbsp; &nbsp; &nbsp;&nbsp;&nbsp;Air contains 21 mol percent O<sub>2<\/sub>&nbsp;and 79 mol percent of N<sub>2&nbsp;<\/sub>by volume<\/li>\n\n\n\n<li>&nbsp; &nbsp; &nbsp; &nbsp;For a given combustion device, say a piston engine, how much fuel and air should be injected in order to completely burn both?&nbsp;<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image\" id=\"attachment_4490\"><img decoding=\"async\" src=\"https:\/\/cfdflowengineering.com\/wp-content\/uploads\/2020\/02\/Methane-gas-combustion-reaction--300x54.jpg\" alt=\"Methane gas combustion reaction\" class=\"wp-image-4490\"\/><figcaption class=\"wp-element-caption\">Methane gas combustion reaction<\/figcaption><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;This question can be answered by balancing the combustion reaction equation for a particular fuel.<\/li>\n\n\n\n<li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;A&nbsp;<strong>stoichiometric mixture&nbsp;<\/strong>has the&nbsp;exact amount of fuel and oxidizer such that after combustion is completed,&nbsp;all the fuel and oxidizer are consumed to form products.&nbsp;<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image\" id=\"attachment_4491\"><img decoding=\"async\" src=\"https:\/\/cfdflowengineering.com\/wp-content\/uploads\/2020\/02\/Methane-gas-combustion-reaction-with-stoichiometry-300x71.jpg\" alt=\"Methane gas combustion reaction with stoichiometry\" class=\"wp-image-4491\"\/><figcaption class=\"wp-element-caption\">Methane gas combustion reaction with stoichiometry<\/figcaption><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Combustion stoichiometry for&nbsp;general hydrocarbon fuel, C<sub>\u03b1<\/sub>H<sub>\u03b2<\/sub>O<sub>\u03b3<\/sub>, with air, can be expressed&nbsp;<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image\" id=\"attachment_4492\"><img decoding=\"async\" src=\"https:\/\/cfdflowengineering.com\/wp-content\/uploads\/2020\/02\/Combustion-stoichiometry-for-general-hydrocarbon-fuel-300x34.jpg\" alt=\"\u00a0Combustion stoichiometry for general hydrocarbon fuel\" class=\"wp-image-4492\"\/><figcaption class=\"wp-element-caption\">Combustion stoichiometry for general hydrocarbon fuel<\/figcaption><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>&nbsp;Methods of Quantifying Fuel and Air Content of Combustible Mixtures<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Fuel-Air Ratio (FAR):&nbsp;<\/strong>The fuel-air ratio,&nbsp;<em>f<\/em>, is given by<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/1.bp.blogspot.com\/-xDVLpKXYtL8\/Xs3iApzxqEI\/AAAAAAAAMUQ\/WoyReSVhriMoIiXqNOlP0hZbpzYpeBosgCK4BGAsYHg\/s320\/FAR_defn.jpg\" alt=\"Fuel Air ratio for combustion\"\/><figcaption class=\"wp-element-caption\">Fuel Air ratio for combustion<\/figcaption><\/figure>\n\n\n\n<p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; where&nbsp;<em>m<\/em><em><sub>f<\/sub><\/em>&nbsp;and&nbsp;<em>m<\/em><em><sub>a<\/sub><\/em>&nbsp;are the respective masses of the fuel and the air.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>For a stoichiometric mixture<\/strong><\/p>\n<\/blockquote>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/1.bp.blogspot.com\/-0wPDR5gGx_A\/Xs3hggeVidI\/AAAAAAAAMT8\/wd3017tbYyUIvfSVBLQjbel6ze6ept0swCK4BGAsYHg\/w640-h70\/Stochiometry_2.3.jpg\" alt=\"For a stoichiometric mixture hydrocarbon reaction\"\/><figcaption class=\"wp-element-caption\">For a stoichiometric mixture hydrocarbon reaction<\/figcaption><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li>&nbsp; &nbsp; &nbsp; &nbsp;The fuel-air-ratio (FAR)&nbsp; for above reaction is given as<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image alignleft\"><a href=\"https:\/\/1.bp.blogspot.com\/-WOsNG0logvw\/Xs3ilvvQ9zI\/AAAAAAAAMUo\/jXiR_1CbBjoo92fbsxoT9UyQEycCyAJsACK4BGAsYHg\/FAR_stoich.jpg\"><img decoding=\"async\" src=\"https:\/\/1.bp.blogspot.com\/-WOsNG0logvw\/Xs3ilvvQ9zI\/AAAAAAAAMUo\/jXiR_1CbBjoo92fbsxoT9UyQEycCyAJsACK4BGAsYHg\/s320\/FAR_stoich.jpg\" alt=\"\"\/><\/a><\/figure>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;where&nbsp;<em>M<\/em><em><sub><em><sub>f<\/sub><\/em><\/sub><\/em>&nbsp;and&nbsp;<em>M<\/em><em><sub><em><sub>air<\/sub><\/em><\/sub><\/em>&nbsp;(~28.84&nbsp;<em>kg\/<\/em><em>kmol<\/em>) are the average masses per mole of fuel and air, respectively. The range of&nbsp;<em>f<\/em>&nbsp;is bounded by zero and one.<\/p>\n<\/blockquote>\n\n\n\n<ul class=\"wp-block-list\">\n<li>&nbsp; &nbsp; &nbsp; &nbsp;Most hydrocarbon fuels have a stoichiometric fuel-air ratio,&nbsp;<em>f<\/em><em><sub>s<\/sub><\/em>, in the range of&nbsp;0.05\u20130.07<\/li>\n<\/ul>\n\n\n\n<p><strong>&nbsp;The air-fuel ratio (AFR);&nbsp;<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>&nbsp; &nbsp; &nbsp; &nbsp; AFR&nbsp;&nbsp;<\/strong>is also used to describe a combustible mixture and is simply the reciprocal of FAR,&nbsp;<\/li>\n<\/ul>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>AFR = 1\/FAR =&nbsp;<em>1\/f&nbsp;<\/em><\/strong><\/p>\n<\/blockquote>\n<\/blockquote>\n<\/blockquote>\n\n\n\n<ul class=\"wp-block-list\">\n<li>For most hydrocarbon fuels, AFR is&nbsp; 14-20: that means&nbsp; 14\u201320 kg of air is required to achieve&nbsp; complete combustion of one&nbsp; kg&nbsp; fuel<\/li>\n<\/ul>\n\n\n\n<p><strong>Equivalence Ratio (<\/strong><strong><em>\u03d5<\/em><\/strong><strong>)<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>&nbsp; &nbsp; &nbsp; Normalizing the actual fuel-air ratio (FAR) by the stoichiometric fuel-air ratio provides&nbsp; the equivalence ratio,<\/li>\n<\/ul>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;\u03d5<em>&nbsp; = FAR<\/em><em><sub><em><sub>a<\/sub><\/em><\/sub><\/em><em>\/FAR<\/em><em><sub><em><sub>s<\/sub><\/em><\/sub><\/em>&nbsp;&nbsp;<\/p>\n<\/blockquote>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/1.bp.blogspot.com\/-h0SOdD70wR8\/Xs3kwrti_6I\/AAAAAAAAMVM\/Tn_Mkn42UfkX3MaJqzZ6fiQEDVjy6YHnQCK4BGAsYHg\/s320\/Equivalent_ratio.jpg\" alt=\"\u00a0Equivalence Ratio for combustion\"\/><figcaption class=\"wp-element-caption\">Equivalence Ratio for combustion<\/figcaption><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;The subscript, s denotes the values at the stoichiometric condition.<\/li>\n<\/ul>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><em>\u03d5<\/em>&nbsp;&lt;1 is a lean mixture,<\/p>\n<\/blockquote>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><em>\u03d5<\/em>&nbsp;= 1 is a stoichiometric mixture,<\/p>\n<\/blockquote>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><em>\u03d5<\/em>&nbsp;&gt;1 is a rich mixture.<\/p>\n<\/blockquote>\n<\/blockquote>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><\/p>\n<\/blockquote>\n\n\n\n<p><strong>Stoichiometric and&nbsp; Excess air<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>&nbsp; &nbsp; &nbsp;The minimum amount of air that supplies the required amount of oxygen for the complete combustion of a fuel is called the&nbsp;stoichiometric or theoretical air<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li>&nbsp; &nbsp; &nbsp;The amount of air in excess of the stoichiometric air is called&nbsp;<strong>excess air<\/strong>. It is usually expressed in terms of the stoichiometric air as percent excess air. The amount of air less than&nbsp;stoichiometric&nbsp;is called a deficiency of air<\/li>\n\n\n\n<li>&nbsp; &nbsp; &nbsp;<strong>Percent Excess Air<\/strong>:&nbsp;The amount of air in excess of the stoichiometric amount is&nbsp;called excess air. The percent excess air, %EA, is defined as<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image\" id=\"attachment_4493\"><img decoding=\"async\" src=\"https:\/\/cfdflowengineering.com\/wp-content\/uploads\/2020\/02\/Formula-for-excess-air-over-the-stoichiometric-amount-300x95.jpg\" alt=\"Formula for excess air over the stoichiometric amount\" class=\"wp-image-4493\"\/><figcaption class=\"wp-element-caption\">Formula for excess air over the stoichiometric amount<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Properties of Mixtures For more details click here: Note: Refer to the book of \u201cThermodynamic\u201d for mixture properties in reactive flows &nbsp;Combustion Stoichiometry &nbsp;Methods of Quantifying Fuel and Air Content of Combustible Mixtures &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; where&nbsp;mf&nbsp;and&nbsp;ma&nbsp;are the respective masses of the fuel and the [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":2211,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[374],"tags":[],"class_list":["post-2264","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-fuels-and-combustion"],"jetpack_featured_media_url":"https:\/\/workhouse.sweetdishy.com\/wp-content\/uploads\/2024\/08\/thermodynamics-1.png","_links":{"self":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/2264","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/comments?post=2264"}],"version-history":[{"count":1,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/2264\/revisions"}],"predecessor-version":[{"id":2265,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/2264\/revisions\/2265"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media\/2211"}],"wp:attachment":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media?parent=2264"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/categories?post=2264"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/tags?post=2264"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}