Course Specifications A Basic Information Course Title: Heat Engine and Combustion (B) Code:MPE321 Lecture: 2 Tutorial: 2 Practical: 0 Total: 4 Program on which the course is given: B.Sc. Mechanical Engineering (Power) Major or minor element of program: Major Department offering the program: Mechanical Engineering Department Department offering the course: Mechanical Engineering Department Academic year / level: Third Year / Second Semester Date of specifications approval: 10/5/2006 B- Professional Information 1- Overall aims of course By the end of the course the students will be able to: Identify the different types of fuels and their properties. - Understand the concepts and principles of the chemical reactions. - Understand the basic principles of the chemical and the phase equilibrium. - Apply the first and second law of thermodynamics on chemical reactions. - Know the different types of flames and their theories. - Know the construction and operation of the industrial furnaces and their applications. - Know the factors affecting the furnaces performance. 2-Intended Learning Outcomes (ILOs) a) Knowledge and Understanding: a.5) Methodologies of solving engineering problems, data collection interpretation. a.8) Current engineering technologies as related to disciplines. a.13) Fundamentals of thermal and fluid processes. a.18) Mechanical power and energy engineering contemporary issues. a.19) Basic theories and principles of some other engineering and mechanical engineering disciplines providing support to mechanical power and energy disciplines 2-Intended Learning Outcomes (ILOs) b) Intellectual Skills b.1) Select appropriate mathematical and computerbased methods for modeling and analyzing problems. b.5) Assess and evaluate the characteristics and performance of components, systems and processes b.7) Solve engineering problems, often on the basis of limited and possibly contradicting information. b.11) Analyze results of numerical models and appreciate their limitations. b.13) Evaluate mechanical power and energy engineering design, processes, and performance and propose improvements. 2-Intended Learning Outcomes (ILOs) Professional and Practical Skills c.1) Apply knowledge of mathematics, science, information technology, design, business context and engineering practice to solve engineering problems. c.12) Prepare and present technical reports. c.16) Describe the basic thermal and fluid processes mathematically and use the computer software for their simulation and analysis. 1-Intended Learning Outcomes (ILOs) General and Transferable Skills d.3) Communicate effectively. d.4) Demonstrate efficient IT capabilities. d.7) Search for information and engage in lifelong self learning discipline. 3- Contents No Topic 1 Fuel types and properties Chemical reactions Theoretical and actual combustion processes Enthaply of formation, enthalpy of reaction 1st and 2nd law analysis of combustion processes Chemical equilibrium Chemical equilibrium (continued) Phase equilibrium 2 3 4 5 6 7 8 No. of hours 2 2 2 2 2 2 2 ILOs Teaching / learning methods and strategies Lecture Lecture – tutorial a.8, c.12,d.4,d.7 a.5, a.13, b.5, b.7, b.13, c.1 Assessment method Report Assignment a.5, a.13, b.5, b.7, b.13, c.1 a.5, a.13, b.5, b.7, b.13, c.1 a.13,b.7, c.1 a.13,b.7, c.1 Lecture – tutorial Assignment Lecture – tutorial Quiz Lecture – tutorial Lecture – tutorial Assignment Quiz a.13,b.7, c.1 Lecture – tutorial Assignment Assignment 9 Laminar premixed flames 2 Mid-term exam a.8,a.13,a.19,b.7, c.1, Lecture – tutorial c.12,c.16, d.3,d.7 Quiz - Report Laminar diffusion flames 2 a.8,a.13,a.19,b.7, c.1, c.12,c.16, d.3,d.7 Lecture – tutorial 10 Turbulent premixed and nonpremixed flames Assignment 2 a.8,a.13,a.19,b.7, c.1, c.12,c.16, d.3,d.7 Lecture – tutorial 11 Introduction to industrial furnaces Assignment 2 a.8,a.13,a.19,b.7, b.13, c.1,c.12, d.4, d.7 Lecture – tutorial 12 Heat transfer in industrial furnaces Quiz 2 a.8,a.13,a.19,b.7, b.13, c.1,c.12, d.4, d.7 Lecture – tutorial 13 Saving energy in industrial furnacs Assignment - Report 2 a.8,a.13,a.19,b.7, b.13, c.1,c.12, d.4, d.7 Lecture – tutorial 14 15 Final exam Teaching and Learning Methods __√__ Lectures _____ Practical training / laboratory _____ Seminar / workshop ____ Class activity __√__ Tutorial _____ Case study __√__ Assignments / homework Other : Self study Student Assessment Methods ________ Assignments to assess knowledge and intellectual skills. . ________ Quiz to assess knowledge, intellectual and professional skills. ________ Mid-term exam to assess knowledge, intellectual, professional and general skills. ________ Oral exam to assess knowledge, intellectual, professional and general skills. ________ Final exam to assess knowledge, intellectual, professional and general skills. Other: Self study to assess knowledge, intellectual, professional and general skills. 1.Assessment schedule Assessment 1 on weeks 2, 5, 9, 11 Assessment 2 Quizzes on weeks 4, 6, 10, 13 Assessment 3 Mid-term exam on week 8 Assessment 4 Oral Exam on week 14 Assessment 5 Final exam on week 15 Weighting of Assessments Mid- Term Examination Final- Term Examination Oral Examination Practical Examination Semester Work Other Total 15% 05% 05% 100% 15% 60% 00% 8- List of References 8.1- G. Van Wylen, R. Sonntag and C. Borgnakke, "Fundamentals of Classical Thermodynamics", Jhon Wiley &Sons. 1994. 8.2-.Yunis, A. Cengle, and Michael A. Boles, “Thermodynamics- an Engineering Approach” Fifth edition, 8.3-.J. Warnatz · U. Maas · R.W. Dibble, “Combustion”, Springer-Verlag Berlin Heidelberg 1996, 1999, 2001 Facilities Required for Teaching and learning Lecture room Presentation board, computer and data show Course coordinator: Course instructor: Head of department: Prof. Dr. Ramadan Y. Sakr Prof. Dr. Ramadan Y. Sakr Prof. Dr. Maher G. A. Higazy Date: 26/10/ 2011 Fuels & Fuels Properties Lecture 1 Crude Oil Found in rock formations that were ocean floors. Organic matter from seas became trapped by sediments at ocean floor. Progressing cracking of the molecules and elimination of oxygen turned organic matter into petroleum. Crude Oil Petroleum is made of 86% carbon and 14% hydrogen. Hydrocarbon molecules are accompanied by dirt, water, sulfur and other impurities. Crude oil must be refined to produce suitable engine fuels. Fig. 5.1: Molecular Structures of Some Hydrocarbon Fuel Families Fig. 5.2: Flow Diagram for Typical Petroleum Refinery Fig. 5.3: Distillation Curve for Crude Oil. Distillation Temperatures 30 to 230 C for Gasoline 230 to 370 C for Diesel Most refineries utilize “cracking units” where catalysts at high temperatures and pressures crack the larger hydrocarbon molecules into smaller ones shifting production towards gasoline. Fractionating towers allow smaller molecules to condense out at cooler temperatures in the upper portion of the tower. Ideal Combustion All of the H in fuel is converted to H20. All of the C in fuel is converted to CO2. Air is 21% O and 79% N by volume. Combustion of Gasoline Stoichiometric Air/Fuel Mixture For gasoline… 3.51 11.54 A/ F 15.1 : 1 1 Table 5.2: Representative Fuel Molecules Fig.1-1 Aliphatic hydrocarbons Fig.1-2 Alicyclic and aromatic hydrocarbo Fig. 1-3 Structural formulae for oxygenous hydrocarbons Fig. (1-4) Boiling graph for gasoline and diesel fuel, as well as kerosene and water Definition of the octane number (ON) for gasoline fuels For the determination of ignition performance, we use a so-called comparison fuel, i.e. a two component fuel consisting of The octane number is defined as the isooctane fraction of the comparison fuel. Definition of the cetane number (CN) for diesel fuels In determining ignition performance, we use a comparison fuel, which is, in this case, a two component fuel composed of: A fuel can be considered as a finite resource of chemical potential energy, i.e., energy stored in the molecular structure of particular compounds that may be released via complex chemical reactions. Some of the basic ideal combustion engineering characteristics of a fuel include: High energy density (content) High heat of combustion (release) Good thermal stability (storage) Low vapor pressure (volatility) Nontoxicity (environmental impact) THE FUEL-ENGINE INTERFACE Gasoline Engine Exhaust SI engines are often operated with “rich” air/fuel mixtures to produce more power – inadequate oxygen supply results in production of CO (not all carbon is converted to CO2). Even with lean mixtures, CO is still produced. DO NOT OPERATE GASOLINE ENGINES IN CONFINED SPACES!!! Diesel Air/Fuel Ratios Stoichiometric air/fuel mixture for CI engines 14.9:1. However, most CI engines are operated with a leaner air/fuel ration and therefore free oxygen is often found in the exhaust. Diesel Engine Exhaust Small quantities of unburned fuel escape in gaseous form. At high temperatures N reacts with O to form NO and NO2 (together these are known as NOx). Federal government has established limits on CO, NOx and unburned hydrocarbon in engine exhaust – Tier I through IV Regulations. Emission Regulations (EPA) Example 5.1 What is the air/fuel ratio and the exhaust products when ethanol is used as an engine fuel? Solution C2 H 6O 3O2 11.28 N 2 11.28 N 2 2CO2 3H 2O 1(46) 3(32) 11.28(28) 11.28(28) 2(44) 3(18) 1 2.087 6.866 6.866 1.913 1.174 A / F (2.087 6.866) / 1 8.95 General Combustion Equations Equations are cast in a form that includes a measure of “richness,” A / Fstoich A / Factual where f is the “richness” term. General Combustion Equations The “General Combustion Equation” is, C x H y Oz U O2 3.76 U N 2 3.76 U N 2 R CO2 V CO W O2 y H 2O 2 where x, y and z are the relative number of atoms of C, H and O, respectively; and U, R, V and W are defined in the following relationships. General Combustion Equations y z U x 4 2 R x when 1 1 R x 2u1 when 1 V 0 when 1 1 V 2U 1 when 1 1 W U 1 when 1 W 0 when 1 General Combustion Equations The actual A/F ratio becomes, 137.3U A / Factual 12 x y 16 z General Combustion Equations The theoretical dry exhaust gas concentrations (volumetric basis) become, 3.76U CONC N 2 T R CONCCO2 T V CONCCO T W CONCO2 T 3.76U T R V W Blended Fuels Blended fuels are common – for example blends of 10 % ethanol and 90% gasoline are used to meet EPA requirements for oxygenated fuels in regions of the country with impaired air quality. Blended Fuels The composite fuel molecule can be estimated using, s fsmp rs p f p ms where the “p” subscript denotes the primary fuel, and “s” the secondary; and variable f is the faction (decimal form) of either fuel. Blended Fuels The resulting composite fuel molecule becomes, C xc H yc Ozc where xc rs xs xp yc rs ys yp zc rs zs zp Octane Ratings Octane is a measure of gasoline’s resistance to “knock.” “Knock” is the uncontrolled release of energy when combustion initiates somewhere other than the spark plug. Symptoms of engine “knock” include an audible “knocking” or “pining” sound under acceleration. Fig. 5.5: Knock in SI engines. Causes of Engine Knock Knock is caused when the temperature in the cylinder reaches the self ignition temperature (SIT) of the end gases. The end gases do not readily ignite, rather there is an ignition delay caused by preflame reactions. Engine knock is more prevalent under conditions that include: Lean air/fuel ratios High compression ratios Methods to Reduce Engine Knock Use wedge shaped combustion chambers to cool end gases more readily. Use gasoline with higher octane ratings – these ratings are associated with gasoline that has few straight chain carbons have longer ignition delay times. Octane Rating Measurement Procedure developed by the Cooperative Fuels Research Committee (CFR). The committee proposed a single cylinder SI engine to measure octane – the CFR engine has an adjustable compression ratio. Engine is driven at a constant speed with an electric motor. Octane Rating Measurement Octane ratings are obtained by comparing fuel in question to iso-octane (Octane Rating of 100) and heptane (Octane Rating of 100). CR is adjusted until “knocking” is detected with fuel being tested. Blends of iso-octane and heptane are tested until the same level of knock is obtained. Octane rating is % of iso-octane in test blend. Fig. 5.6: CFR Engine Octane Ratings CFR developed initial method (Motor Octane Number – MON). ASTM developed a new method (Research Octane Number – RON). RON octane ratings are 8 points low than MON for most gasoline. Most retailers report the Anti-Knock Index which is an average of MON and RON. Octane ratings of fuel are adjusted for elevation – lower atmospheric pressure reduces the tendency for engine knock to occur. Cetane Ratings and CI Engines Octane rating is not a good way to predict “knock” in CI engines. Combustion in diesel engines consists of a two part delay – physical and chemical. Physical - the fuel is injected and atomized. Chemical - process proceeds with a preflame chemical reaction, similar to that of SI engines. Fig. 5.7: Critical Compression Ratios and Temperatures Combustion Process Pre-Mix Combustion – prepared mixture burns rapidly after compression ignition. Diffusion Combustion – fuel vapor diffuses into burn-out zones from one side while oxygen diffuses from the other sustaining the combustion process. Diffusion process is much slower than the pre-mix. Pre-mix generate characteristic diesel rattle. Fig. 5.8: Energy release from CI fuels. Altering Knock in CI Engines Ignition delay controls the relative release of energy between the two phases of combustion – a longer delay results in more energy produces in the pre-mix phase. Since “knock” occurs when more energy is released at the start of combustion, it follows that “knock” is reduced with short delay periods. Cetane Ratings Cetane rating are an indication of the fuel’s anti-knock resistance for CI engines. Fuels with high cetane ratings are created by increasing the proportion of long chain molecules, thereby reducing the ignition delay. Fuels with high Octane Rating have low cetane ratings! Cetane Ratings CFR cetane rating process is similar to the Octane process with a couple of differences: Cetane and hyptamethylnonane reference fuels. are the Hyptamethylnonane has a cetane rating of 15. Effect of Cetane Rating If cetane rating is too low, the ignition delay results in hard starting (combustion after piston is moving downward) and characteristic ”white smoke.” High cetane ratings start the combustion process to soon, and some the fuel is not volatized and does not burn. “Black smoke” in heavily loaded engines is a symptom of high cetane ratings. Minimum cetane rating for CI engines is 40 according to SAE. Commercial fuels seldom exceed 50. Cetane rating should never exceed 60. Table 5: limiting values for diesel fuels. Fuel Properties Standards Organizations SAE – Society of Automotive Engineers ASTM – American Society for the Testing of Materials API – American Petroleum Institute Specific Gravity A measure of the density of liquid fuels at 15.6 C as compared with water at the same temperature. API devised the following scale, 141.5 API 131.5 SG o where SG is the specific gravity. A hydrometer, calibrated in APIo, is used to measure the specific gravity. Fig. 5.9: Fuel hydrometer. Heating Value of Fuel Determined using bomb calorimeter. Bomb calorimeter measures “low heating value” – void of energy required to evaporate water. “High heating value” is found by adding the latent heat of vaporization of water to “low heating value.” Table 5.4: Properties of selected fuels. Heating Value Estimates for Petroleum Fuels Heating values are estimated from the API gravity, H g 42,860 93 API 10 (kJ / kg) H n 0.7190 H g 10,000 (kJ / kg) where Hg is the gross (high) heating value and Hn is the net (low) heating value. Fuel Volatility Volatility refers to the ability of the fuel to vaporize at lower temperatures. Reid vapor pressure and distillation curves are indicators of fuel volatility. Reid vapor pressure (RVP) is a standardized test using bomb calorimeter at 37.1 C – pressure is measured using a suitable gage. Fuel Volatility Prior to 1990 winter gasoline volatility ranged from 60 to 80 kPa. Summer gasoline was 10 to 15 kPa lower to reduce the potential for vaporization. Clean Air Act (1990) limits maximum vapor pressures to 56 kPa in the large Northern U.S. cities and 49 kPa in large Southern U.S. cities. Distillation Tests 100 ml sample is distilled. Fuel temperature is recorded for first condensed drop (boiling point), and then at 10 ml intervals during the distillation process. T10, T50 and T90 temperatures are important to engine characteristics which include easy of starting, warm-up, and crankcase dilution and fuel economy, respectively. Fig. 5.10: Fuel distillation aparataus. Adjusting Distillation Temperatures Gasoline sold during the winter must be more volatile for easy starting in the winter. Gasoline sold for use in high elevations must be less volatile to avoid “vapor lock” in the summer. Volatility is adjusted by adding butane and lighter hydrocarbons. Adjusting Distillation Temperatures For diesel engines: Low T10 values aids cold weather starting. Low T50 values minimize smoke and odor. Low T90 values reduce crankcase dilution and improve fuel economy. Fig. 5.11: Distillation curves. Fuel Viscosity Viscosity is a measure of the flow resistance of liquid. Fuel viscosity must be high enough to insure good lubrication of injection pump mechanisms in CI engines. Fuel viscosity must be low enough to insure proper atomization at the time of injection. Cloud and Pour Points Cloud point is the temperature at which crystals begin to form in the fuel. Pour point is the temperature at which the fuel ceases to flow. Cloud point are typically 5 to 8 C higher than pour point, Not an issue for gasoline. Values are important for diesel. Fuel Impurities - Sulfur Sulfur oxides – can convert to acids which corrode engine parts and cause increased wear. Assessed by immersing copper strip in fuel for three hours, then comparing corrosion to standard strips. Fuel Impurities - Ash Ash – small solid particles or water-soluble metals found fuels. Defined as un-burned fuel residue left behind. Can cause accelerated wear of close-fitting injection system parts. Fuel Impurities – Water and Sediment Moisture can condense in fuel storage tanks, or seep in from underground leaks. Fuel should be bright and clear, and visibly free of water and sediment. Fuel Impurities - Gum Gum can form in gasoline, leaves behind deposits on carburetors. Gum is dissolved by gasoline – more prevalent in gasoline that is made by cracking. Antioxidants are now added to both diesel and gasoline to extend storage life without gum formation. Fuel Additives Until 1970, gasoline contained TEL (tetraethyl lead). TEL was used as an octane booster. MTBE (methyl tertiary butyl ether) is often substituted as an octane booster – could be phased out/banned by EPA soon. Table 5.5: Gasoline additives Fuel Storage Fuels classified according to flammability – gasoline is more dangerous with a flash point of -40 C. Major concern with regard to environmental contamination Fig. 5.12: Lubricating Theory F f f Fn Fig. 5.13: Action of Journal Bearings a) at rest, b) in mixed-film lubrication, and c) in hydrodynamic lubrication Fig. 5.14: Newtonian Viscosity v F A h Fig. 5.15: Cannon-Fenske Viscometer Reporting of Viscosity Kinematic viscosity (n) is reported as, where m is absolute (or dynamic) viscosity, and r is the fluid mass density. Typical Units Centipoise (cP) was the popular unit of dynamic viscosity. 1 cP 1 mPa s Centistoke (cSt) was the popular unit of kinematic viscosity. 1 cSt 1 mm / s 2 Table 5.6: SAE Motor Oil Classification Motor Oil Service Ratings “S”- SERVICE CLASSIFICATIONS FOR GASOLINE ENGINES SH- For 1994 Gasoline Engine Service -- Classification SH was adopted in 1992 and recommended for gasoline engines in passenger cars and light trucks starting in 1993 model year. This category supercedes the performance requirements of API SG specification for 1989-1992 models, which is now obsolete. Applications that call for an API service classification SG can use the SH specification. The specification addresses issues with deposit control, oxidation, corrosion, rust and wear and replaces. SJ- For 1997 Gasoline Engine Service -- Classification SJ was adopted in 1996 and recommended for gasoline engines in passenger cars and light trucks starting in 1997 model year. Applications specifying API SH can use the newer API SJ service classification. Note that where applicable certain letters in the sequence will be skipped to prevent confusion with other standards. In this case, SI was skipped since industrial oils are currently rated according to SI classifications. SL- For 2001 and Newer Gasoline Engine Service- Current Spec. -Recommended for gasoline engines in passenger cars and light trucks starting in July 2001. SL oils are engineered to provide improved high temperature deposit control and lower oil consumption. Applications specifying API SJ can use the new API SL service classification. Note that some SL rated oils may also meet the latest ILSAC specification and/or qualify as energy conserving. SL is the latest specification. Motor Oil Service Ratings “C”- COMMERCIAL CLASSIFICATIONS FOR DIESEL ENGINES CF-For 1994 Off-Road Indirect Injected Diesel Engine Service -- API Service Category CF denotes service typical of off-road, indirect injected diesel engines and other diesel engines that use a broad range of fuel types, including those using fuel with higher sulfur content (over 0.5% wt sulfur fuel). Effective control of piston deposits, wear and corrosion of copper-containing bearings is essential for these engines, which may be naturally aspirated, turbocharged or supercharged. Oils designated for this service may also be used when API Service Category CD or CE is recommended. CF is a current specification. CF-2- FOR 1994 Severe Duty 2-Stroke Cycle Diesel Engine Service -- API Service Category CF-2 denotes service typical of two-stroke cycle engines (such as Detroit Diesel) requiring highly effective control over cylinder and ring-face scuffing and deposits. Oils designated for this service have been in existence since 1994 and may also be used when API Service Category CD-II is recommended. These oils do not necessarily meet the requirements of CF or CF-4, unless they pass the test and performance requirements for these categories. CF-2 is a current specification. CF-4- For 1990 Diesel Engine Service -- Service typical of severe duty turbocharged, 4-stroke cycle diesel engines, particularly late models designed to give lower emissions. These engines are usually found in on-highway, heavy-duty truck applications. API CF-4 oils exceed the requirement of CE category oils and can be used in place of earlier CC, CD and CE oils. CF-4 oils provide for improved control of piston deposits and oil consumption. The CF-4 classification meets Caterpillar’s 1k engine requirements, as well as earlier Mack Trucks (T-6 & T-7) and Cummins (NTC-400) multi-cylinder engine test criteria. When combined with the appropriate “S” category, they can be used in gasoline and diesel powered cars and light trucks as specified by the vehicle and/or engine manufacturer. Motor Oil Service Ratings CG-4- For 1995 Severe Duty Diesel Engine Service -- API Service Category CG-4 describes oils for use in high speed, four-stroke cycle diesel engines used in highway and off-road applications, where the fuel sulfur content may vary from less than 0.05% by weight to less than 0.5% by weight. CG-4 oils provide effective control over high temperature piston deposits, wear, corrosion, foaming, oxidation stability and soot accumulation. These oils are especially effective in engines designed to meet 1994 exhaust emissions standards and may also be used in engines requiring API Service Categories CD, CE and CF-4. Oils designated for this service have been in existence since 1995. CG-4 is a current specification CH-4- For 1999 Severe Duty Diesel Engine Service -- API Service Category CH-4 describes oils for use in high speed, four-stroke cycle diesel engines used in highway and off-road applications. CH-4 oils provide effective control over engine deposits, wear, corrosion, oxidation stability and soot accumulation. These oils are especially effective in engines designed to meet 1999 emission standards and may also be used in engines requiring API Service Category CG-4. Oils designated for this service have been in existence since 1999. CH-4 oils are engineered for use with diesel fuels ranging in sulfur content up to 0.5% weight. CH-4 is a current specification. CL-4- For 2002 Severe Duty Diesel Engine Service -- API Service Category CL-4 describes oils for use in those high speed, four-stroke cycle diesel engines designed to meet 2004 exhaust emissions standards and was implemented in October 2002. These oils are engineered for all applications where diesel fuel sulfur content is up to 0.05% by weight. These oils are very effective at sustaining engine durability where EGR ( Exhaust Gas Recirculation) and other exhaust emissions systems are used and provide for optimum protection in the areas of corrosive wear, low and high temperature stability, soot handling properties, piston deposit control, valvetrain wear, oxidative thickening and foaming and viscosity loss due to shear. API CL-4 oils are superior in performance to those meeting APICH-4, CG-4 and CF-4 and can be used and will effectively lubricate diesel engines specifying those API service Classifications. Table 5.8: Lubricating Oil Additives Fig. 5.16: Pressure-Feed and Splash Lubrication System.