Class Notes on Thermal Energy Conversion System For the students of Civil & Rural 3rd semester Ramesh Khanal Assistant Professor Nepal Engineering College Bhaktapur, Nepal 2015 Class Notes on Thermal Energy Conversion System Course Structure MEC 209.3: Thermal Energy Conversion System (3-1-2) Theory Practical Total Sessional 30 20 50 Final 50 - 50 Total 80 20 100 Course Objective The objective of this course is to make the students familiar with air standard cycles, principle and systems of internal combustion engines and fuels and their combustion properties. Course Contents: 1. Gas Power Cycles and Reversibility (6 hours) Introduction; Air Standard Efficiency of a Cycle; Thermodynamic Reversibility; Carnot’s Cycle; Otto Cycle and actual pV diagram for Otto Cycle; Diesel Cycle and actual pV diagram for Diesel Cycle; Dual Combustion Cycle; Comparison of Otto, Diesel and Dual Combustion Cycles; Brayton Cycle; Stirling Cycle. 2. Reciprocating Steam Engine: (5 hours) The Rankine Cycle; Comparison of Rankine and Carnot’s Cycle; Rankine Cycle applied to steam engine plant; Rankine Cycle on TS diagram; Steam Engine Indicators; Hypothetical and Actual Indicator Diagram of Steam Engine. 3. Internal Combustion Engines (7 hours) Introduction; Classification of Internal Combustion Engines; Working Cycles of Internal Combustion Engines; Two Stroke Cycle Petrol and Diesel Engines; Four Stroke Cycle Petrol and Diesel Engines; Basic Parameters of Internal Combustion Engines; Components of Internal Combustion Engines. 4. Performance of Internal Combustion Engines (12 hours) Indicated Power, Brake Power, Mean Effective Pressure; Engine Efficiency; Heat Balance for Internal Combustion Engines; Power, Torque, Speed Relationship; Specific Fuel Consumption; Gasoline and Gaseous Fuel Systems: carburation system, temperature and altitude effects, gaseous fuel storage, air-mixing, relative efficiency; Ignition Systems: spark ignition engines, conventional system- primary and secondary circuits, electronic ignition, comparison and effects on engine performance, compression ignition engines, fuel injector characteristics, engine output and efficiency; Cooling Systems: liquid (water/anti-freeze) coolant, dry and wet liners corrosion inhibitors, air cooling, temperature limitations, fan power requirement, comparative advantage of liquid and air cooling system; Lubrication i Class Notes on Thermal Energy Conversion System System: lubrication requirements of spark ignition and compression ignition engines, low pressure splash lubrication system, high pressure gear pumps and distribution system. 5. Reciprocating Air Compressor (8 hours) Primary Components of a Reciprocating Air Compressor; Reciprocating Compression, Clearance Volume Effects, p-V diagram and work done; Volumetric and Adiabatic Efficiencies, Compression Process on T-s Diagram; Multi-stage compression, Intercooling, Optimum pressure distribution Work done, Representation of p-V and T-s diagram; Positive Displacement Compressor Types, Axial flow compressors, Roots Blower, Rotary compressors. 6. Fuels and Combustion (7 hours) Introduction; Classification of Fuels; Solid Fuels; Liquid Fuels; Gaseous Fuels; Calorific and Heating Values of Fuels; Determination of Calorific Values for Solid, Liquid and Gaseous Fuels; Combustion Equations for Hydrocarbon Fuels; Combustion in Spark Ignition and Compression Ignition Engines; Pre-Ignition and Ignition Delays; Detonation and Effects of Operating Variables on Detonation. Total Lectures 45 hours Laboratories: Five laboratory Exercises to be performed in this course, as stated hereunder: i. Studies on Parallel Flow and Counter Flow Heat Exchangers ii. Performance Evaluation of Reciprocating Air-Compressor iii. Study of Systems and Components of Internal Combustion Engines iv. Performance Testing of Spark Ignition Engine: Ignition Timing, Fuel Combustion, Losses, Mechanical Efficiency, Air-Fuel Ratio, Volumetric Efficiency, Compression Ratio, Exhaust Emission, Energy Balance v. Performance Testing of Compression Ignition Engine: BMEP, Injection Timing, Fuel Consumption, Losses, Mechanical Efficiency, Air-Fuel Ratio, Volumetric Efficiency, Compression Ratio, Exhaust Emission, Energy Balance Tutorial: Problem Solving and Assignments Text Books and References: i. J.B. Heywood. Internal Combustion Engine Fundamentals. McGraw Hill Book Co. ii. C.R. Ferguson. Internal Combustion Engine. Wiley Publishers (latest edition). iii. P.L. Ballaney. Thermal Engineering (Heat Engines). Khanna Publishers, New Delhi. ii Class Notes on Thermal Energy Conversion System Content Chapter 1. Gas Power Cycles and Reversibility ..................................................................................... 1 1.1 Introduction ................................................................................................................................... 1 1.2 Air standard efficiency of a cycle .................................................................................................. 1 1.3 Thermodynamic reversibility ....................................................................................................... 2 1.4 Carnot cycle .................................................................................................................................... 2 1.5 Brief introduction to petrol and diesel engine operation .......................................................... 4 1.6 Approximation of real cycle with air standard cycle .................................................................. 5 1.7 Otto cycle ........................................................................................................................................ 6 1.8 Diesel cycle ..................................................................................................................................... 8 1.9 Dual cycle ..................................................................................................................................... 11 1.10 Comparison of Otto, Diesel and Dual cycle ................................................................................ 13 1.11 Brayton cycle ............................................................................................................................... 17 1.12 Stirling Cycle ................................................................................................................................ 20 Chapter 2. Reciprocating Steam Engine ............................................................................................... 32 2.1 Rankine cycle ............................................................................................................................... 32 2.2 Mean temperature of heat addition ........................................................................................... 33 2.3 Comparison of Rankine and Carnot cycle .................................................................................. 34 2.4 Effect of pressure and temperature on Rankine cycle ............................................................. 35 2.5 Working principle of reciprocating steam engine .................................................................... 36 2.6 Steam engine indicators .............................................................................................................. 37 2.7 Hypothetical indicator diagram ................................................................................................. 37 2.8 Hypothetical and actual indicator diagram ............................................................................... 39 Chapter 3. Internal Combustion Engine ............................................................................................... 45 3.1 Introduction ................................................................................................................................. 45 3.2 Classification of IC engines ......................................................................................................... 46 3.3 Working cycle of IC engines ........................................................................................................ 46 3.4 Valve timing diagram of four stroke IC engine ......................................................................... 49 3.5 Components of IC engines .......................................................................................................... 51 3.6 Parts common to SI engine ......................................................................................................... 54 3.7 Parts common to CI engine ......................................................................................................... 55 3.8 Basic engine parameters ............................................................................................................. 55 Chapter 4. Performance of Internal Combustion Engine .................................................................... 57 4.1 Mean effective pressure (MEP) .................................................................................................. 57 4.2 Indicated power (IP) ................................................................................................................... 57 iii Class Notes on Thermal Energy Conversion System 4.3 Brake power (BP) ........................................................................................................................ 58 4.4 Engine efficiencies ......................................................................................................................