Enternal combustion

• The purpose of internal combustion engines (diesel and petrol) is to convert the chemical energy available in hydrocarbon fuel CxHy to mechanical energy or any other type of desired energy such as electric energy and heat energy
• Both petrol and diesel engines are internal combustion engines (I.C.Es.) working on either the two or four stroke cycle

  
• Internal combustion engine types

  • Spark ignition engine
  • Diesel engine
  • Gas turbine engine

  
• Most internal combustion engines are reciprocating engines having piston that reciprocate back and forth in cylinders internally within the engine

  
• Engine designs

  • V6 engine with six cylinders
  • In-line engine with four cylinders
• Gas turbine engine

  • Working cycle of a turbo-jet engine

  
• Spark ignition (S.I.) engine

  The combustion process occurs by spark plug
• Compression ignition (C.I.) engine

  The combustion process starts when the air-fuel mixture self-ignites due to high temperature caused by high compression

  
• Four-stroke cycle engine

  • 4 stroke engine completes 2 rotations of the crankshaft after completing one cycle
  • Power is produced once every 4 strokes of the piston
• Two-stroke cycle engine

  • 2 stroke engine completes 1 rotation of crankshaft after completing one cycle
  • Power is produced once during 2 strokes of the piston
• Engine valve locations

  • Valves in block (flat head), also called L Head engine
  • Valves in head (overhead valve), also called I Head engine
  • One valve in head (usually intake) and one in block, also called F Head engine
• Reciprocating engine


  • Engine has one or more cylinders in which pistons reciprocate back and forth
  • The combustion chamber is located in the closed end of each cylinder
  • Power is delivered to a rotating output crankshaft by mechanical linkage with the pistons

  
• Rotary engine


  • Engine is made of a block (stator) built around a large nonconcentric rotor and crankshaft
  • The combustion chambers are built into the nonrotating block
• Reciprocating engine cylinder arrangements

  • Single cylinder
  • In-line
  • V-Engine
  • Opposed cylinder engine
  • W-Engine
  • Opposed Piston Engine
• Angle between banks of cylinders

  • Can be anywhere from 15° to 120°, with 60°–90° being common
• V engines


  • Usually have even numbers of cylinders from 2 to 20 or more
• Opposed cylinder engine

  Two banks of cylinders opposite each other on a single crankshaft (a V engine with a 180° V)
• Opposed cylinder engines

  • Common on small aircraft and some automobiles with an even number of cylinders from two to eight or more
• Flat engines


  Another name for opposed cylinder engines (e.g., flat four)
• 1. Engine

  Engines of two different cylinder arrangements have been classified as W engines in the technical literature. One type is the same as a V engine except with three banks of cylinders on the same crankshaft.
• Opposed Piston Engine

  Two pistons in each cylinder with the combustion chamber in the center between the pistons. A single combustion process causes two power strokes at the same time, with each piston being pushed away from the center and delivering power to a separate crankshaft at each end of the cylinder.
• Radial Engine


  • Engine with pistons positioned in a circular plane around a central crankshaft. The connecting rods of the pistons are connected to a master rod which, in turn, is connected to the crankshaft. A bank of cylinders on a radial engine almost always has an odd number of cylinders ranging from 3 to 13 or more.
• Naturally Aspirated

  No intake air pressure boost system
• Supercharged

  Intake air pressure increased with the compressor driven off of the engine crankshaft
• Turbocharged


  Intake air pressure increased with the turbine–compressor driven by the engine exhaust gases

  
• Crankcase compressed

  Two-stroke cycle engine which uses the crankcase as the intake air compressor
• Methods of Fuel Input for Spark Ignition (S.I.) Engines

  • Carburetted
  • Multipoint port fuel injection: One or more injectors at each cylinder intake
  • Throttle body fuel injection: Injectors upstream in intake manifold
  • Gasoline Direct Injection: Injectors mounted in combustion chambers with injection directly into cylinders

  
• Fuels Used

  • Gasoline
  • Diesel oil or fuel oil
  • Gas, Natural gas, and Methane
  • Liquefied Petroleum Gas (LPG)
  • Alcohol – Ethyl, and Methyl
• Types of Cooling

  • Air cooled
  • Water cooled
• From Equations (20) and (21), we can get

  1. 𝑉𝑖/𝑉 = 𝑛𝑖/𝑛 = 𝑋𝑖

  2. ∑ 𝑉𝑖 = ∑ 𝑋𝑖𝑉

  3. ∑ 𝑉𝑖 = 𝑉
• Amagat–Leduc law of additive volume

  Equation (24)
• Total internal energy of the mixture U

  1. 𝑈 = 𝑈1 + 𝑈2 + 𝑈3 + ... + 𝑈𝐾 = ∑ 𝑈𝑖

  2. 𝑈 = ∑ 𝑚𝑖𝑢𝑖

  3. 𝑈 = ∑ 𝑛𝑖𝑢̅𝑖
• Internal energy on mass basis

  𝑢 = ∑ 𝑚𝑖/𝑚 𝑢𝑖 = ∑ 𝑋̅𝑖𝑢𝑖
• Internal energy on molar basis

  𝑢̅ = ∑ 𝑛𝑖/𝑛 𝑢̅𝑖 = ∑ 𝑋𝑖𝑢̅𝑖
• Enthalpy of the mixture

  1. 𝐻 = ∑ 𝑚𝑖ℎ𝑖, ℎ = ∑ 𝑚𝑖/𝑚 ℎ𝑖 = ∑ 𝑋̅𝑖ℎ𝑖

  2. ℎ̅ = ∑ 𝑛𝑖/𝑛 ℎ̅𝑖 = ∑ 𝑋𝑖ℎ̅𝑖
• Entropy of the mixture

  1. 𝑆 = ∑ 𝑚𝑖𝑠𝑖, 𝑠 = ∑ 𝑚𝑖/𝑚 𝑠𝑖 = ∑ 𝑋̅𝑖𝑠𝑖

  2. 𝑠̅ = ∑ 𝑛𝑖/𝑛 𝑠̅𝑖 = ∑ 𝑋𝑖𝑠̅𝑖
• Specific heat at constant volume (CV)

  𝐶𝑉 = (𝜕𝑢/𝜕𝑇)𝑉
• Specific heat at constant volume (CV) on mass basis

  𝐶𝑉 = 1/𝑚 ∑ 𝑚𝑖(𝜕𝑢/𝜕𝑇)𝑉 = ∑ 𝑚𝑖/𝑚 𝐶𝑉𝑖 = ∑ 𝑋̅𝑖𝐶𝑉𝑖
• Specific heat at constant volume (CV) on molar basis

  𝐶𝑉̅̅̅̅ = ∑ 𝑛𝑖/𝑛 𝐶𝑉𝑖̅̅̅̅ = ∑ 𝑋𝑖𝐶𝑉𝑖̅̅̅̅
• Specific heat at constant pressure (CP)

  𝐶𝑃 = (𝜕ℎ/𝜕𝑇)𝑃