IC Engines & Gas Turbines Flashcards

Academic Standards and Course Overview

• Program and Regulation: R22 B.Tech. Mechanical Engineering syllabus.
• Course Title: IC ENGINES & GAS TURBINES.
• Academic Level: B.Tech. II Year II Semester.
• Institution: JNTUH Hyderabad.
• Course Credits and Teaching Schedule:
  • Lectures ($L$): 3
  • Tutorials ($T$): 0
  • Practical ($P$): 0
  • Credits ($C$): 3
• Pre-requisite Knowledge: Proficiency in Thermodynamics is required prior to this course.

Course Objectives

• Component Understanding: To provide a comprehensive explanation of the components and systems that constitute Internal Combustion (IC) Engines.
• Combustion Analysis: To analyze the various stages of combustion to enhance IC engine performance, specifically focusing on fuel economy and the control of emissions within global, environmental, and social contexts.
• Performance Evaluation: To facilitate the understanding and evaluation of performance analysis for major IC engine systems and their practical applications.
• Compressor Explorations: To explore the mechanical components and working principles of various compressors including rotary, reciprocating, dynamic, and axial types.
• Gas Turbine Significance: To establish the significance of gas turbines in the modern context of power generation.

Course Outcomes

Upon successful completion of the course, students will be able to:

• Working Principles: Elaborate on the working principles and structural classifications of IC Engine systems.
• Combustion Exploration: Explore the detailed stages of combustion in Spark Ignition ($SI$) and Compression Ignition ($CI$) engines, including the identifying factors that influence combustion quality.
• Testing Proficiency: Numerically evaluate testing procedures and the various performance parameters associated with IC engines.
• Compressor Mechanics: Explain the specific functions and working principles of rotary, reciprocating, and dynamic axial compressors.
• Gas Turbine Analysis: Demonstrate an understanding of gas turbine working principles, classifications, and thermodynamic analysis processes.

Unit I: I.C. Engine Fundamentals and Systems

• General Classification: Structural and operational classifications of engines (by fuel, cycle, ignition, cooling, etc.).
• Working Principles:
  • Four-Stroke Engine: Involves the four distinct strokes: Suction, Compression, Power (Expansion), and Exhaust, completed in two revolutions of the crankshaft.
  • Two-Stroke Engine: Completes the power cycle in only one revolution of the crankshaft, utilizing ports instead of valves.
  • SI vs. CI Engines: Detailed comparison between Spark Ignition ($SI$) engines and Compression Ignition ($CI$) engines.
• Timing Diagrams:
  • Valve Timing Diagram: Graphic representation of the opening and closing of intake and exhaust valves relative to the crankshaft position ($TDC$ and $BDC$).
  • Port Timing Diagram: Specific to two-stroke engines, showing the timing of intake, transfer, and exhaust port operations.
• Cycle Analysis:
  • Air-Standard Cycles: Theoretical cycles (like Otto, Diesel, and Dual) assuming air as the working fluid with constant specific heat ($C_p$ and $C_v$).
  • Air-Fuel Cycles: Improved analysis considering the variation of specific heats, dissociation, and actual gas properties.
  • Actual Cycles: Analysis incorporating real-world losses such as time loss, heat loss, and blowdown loss.
• Engine Systems:
  • Fuel Systems for SI Engines: Detailed study of Carburetors (venturi principle and mixture requirements) and modern Fuel Injection Systems.
  • Fuel Systems for CI Engines: Comprehensive look at Diesel fuel injection systems, including pumps and injectors.
  • Ignition Systems: Battery ignition, magneto ignition, and electronic ignition timing.
  • Cooling Systems: Air cooling (fins) and water/liquid cooling (radiators, thermostats).
  • Lubrication Systems: Mist, splash, and pressure lubrication methods.
• Chemical Thermodynamics:
  • Fuel properties (Volatility, calorific value, viscosity).
  • Combustion Stoichiometry: Mathematical calculation of the exact air-fuel ratio ($AFR$) required for complete combustion: $\text{Fuel} + n(\text{O}_2 + 3.76\text{N}_2) \rightarrow \text{CO}_2 + \text{H}_2\text{O} + 3.76n\text{N}_2$.

Unit II: Combustion in SI and CI Engines

• Spark Ignition (SI) Engines:
  • Normal Combustion: Flame propagation from the spark plug throughout the chamber.
  • Flame Speed: The importance of flame velocity and the effects of engine variables (turbulence, fuel-type, temperature).
  • Abnormal Combustion: Detailed study of Pre-ignition and Knocking ($detonation$) in SI engines.
  • Fuel Rating: Identification of fuel requirements and the use of Octane Numbers and anti-knock additives.
  • Combustion Chambers: Requirements and types of SI engine combustion chambers.
• Compression Ignition (CI) Engines:
  • Four Stages of Combustion: Ignition delay (1), Uncontrolled combustion (2), Controlled combustion (3), and Afterburning (4).
  • Delay Period: Calculation and importance of the ignition delay period.
  • Diesel Knock: Causes and remedies for knocking in CI engines, contrasted with SI knock.
  • Air Movement and Turbulence: The necessity for suction-induced, compression-induced, and combustion-induced turbulence to ensure proper mixing.
  • Chamber Designs: Comparison between Open and Divided (Pre-combustion) chambers.
  • Diesel Fuel Rating: Requirements and Cetane Number rating.

Unit III: Performance Testing and Reciprocating Compressors

• Parameters of Performance:
  • Measurement techniques for cylinder pressure, fuel consumption, and air intake.
  • Exhaust gas composition analysis.
  • Power Calculations:
    • Brake Power ($BP$): Measured at the output shaft, typically using a dynamometer: $BP = \frac{2 \times \tau \times N \times \tau}{60,000} \text{ kW}$.
    • Indicated Power ($IP$): Power generated inside the cylinder.
    • Frictional Losses: Difference between $IP$ and $BP$, often determined via the Morse Test or Willan’s line.
• Heat Balance Sheet: A full accounting of the energy input from fuel versus energy output (useful work, heat to cooling water, heat to exhaust gases, and radiation losses).
• Compressor Classification:
  • Distinction between Fans, Blowers, and Compressors based on pressure ratios.
  • Positive displacement vs. Dynamic types.
  • Reciprocating vs. Rotary types.
• Reciprocating Compressors:
  • Work Required: Mathematical derivation for work: $W = \frac{n}{n-1} P_1 V_1 [(\frac{P_2}{P_1})^{\frac{n-1}{n}} - 1]$.
  • Efficiencies: Isothermal efficiency and Volumetric efficiency.
  • Clearance Volume: The effect of clearance volume on air delivery.
  • Staged Compression: Advantages of multi-stage compression, including under-cooling (inter-cooling) and the condition for minimum work: $P_i = \text{sqrt}(P_1 \times P_2)$.

Unit IV: Rotary and Dynamic Compressors

• Rotary Compressors (Positive Displacement):
  • Roots Blower: Mechanical details and principle of operation.
  • Vane Sealed Compressor: Working principles and efficiency considerations.
• Centrifugal Compressors (Dynamic):
  • Mechanical details: Impeller, diffuser, and casing.
  • Energy Transfer: Velocity and pressure variations throughout the compressor.
  • Impeller Blades: Influence of radial, forward, and backward leaning blades.
  • Losses and Factors: Slip factor ($\text{slip}$), Power input factor, Pressure coefficient, and Adiabatic coefficient.
  • Velocity Diagrams: Construction and analysis of velocity triangles for power calculation.
• Axial Flow Compressors:
  • Mechanical details and stage-by-stage principle of operation.
  • Velocity Triangles: Analysis of energy transfer per stage.
  • Degree of Reaction ($R$): Definition and its effect on stage design.
  • Performance Metrics: Work done factor, Isentropic efficiency, and Polytropic efficiency calculations.

Unit V: Gas Turbines

• Gas Turbine Plants: Overview of simple plants, including Closed Cycle and Open Cycle configurations.
• Thermodynamic Cycles:
  • Constant Pressure Cycle (Brayton Cycle): Ideal logic and cycle efficiency: $\text{Eff} = 1 - \frac{1}{r_p^{\frac{\nu-1}{\nu}}}$.
  • Constant Volume Cycle: Theoretical considerations.
• Cycle Parameters:
  • Work Ratio: Ratio of net work to turbine work.
  • Optimum Pressure Ratio: Determination of the pressure ratio that yields maximum specific work output.
  • Performance Analysis: Evaluation of parameters in both ideal and actual cycles (considering isentropic efficiencies of the compressor and turbine).

Recommended Resources

• Textbooks:
  1. I.C. Engines by V. Ganesan, 4th Edition, McGraw Hill.
  2. Thermal Engineering by Mahesh M Rathore, Tata McGraw Hill, 2010.
• Reference Books:
  1. Applied Thermodynamics for Engineering Technologists by Eastop & McConkey, Pearson.
  2. Fundamentals of Classical Thermodynamics by Vanwylen G.J. and Sonntag R.E., Wiley Eastern.
  3. Internal Combustion Engines Fundamentals by John B. Heywood, McGraw Hill Ed.