Internal Combustion Engine Principles

Principles of Internal Combustion Engine

• A heat engine is a machine that converts heat into useful work by burning fuel.
• There are two types of heat engines: external combustion engines and internal combustion engines.
• In an external combustion engine, the combustion of fuel takes place outside the cylinder, and the heat is generated in a boiler.
• In an internal combustion engine, the combustion of fuel takes place inside the cylinder, and the heat is generated within the cylinder.
• The internal combustion engine uses the expansive force of gases produced by burning fuel within the cylinder to convert the generated heat into useful power.

Types of Combustion in Internal Combustion Engine

• There are two ways combustion takes place within the cylinder:
  • Constant Volume Combustion (CVC): rapid explosion of the air-fuel mixture within the cylinder, ignited by a spark.
  • Constant Pressure Combustion (CPC): slow burning of fuel injected into highly compressed heated air contained in the cylinder.

Advantages of Internal Combustion Engine

• More mechanical simplicity and lower weight/power ratio.
• No need for auxiliary equipment, such as boiler and condenser.
• Can be started and stopped in a short time.

Components of Internal Combustion Engine

• Connecting Rod: made of drop-forged steel, with an I-beam type section, connecting the piston to the crankshaft.
• Crankshaft: connected to the piston through the connecting rod, converts the linear motion of the piston into the rotational motion of the flywheel.
• Engine Bearings: anti-friction bearings that support the crankshaft and camshaft, capable of withstanding high speed, heavy load, and high temperatures.
• Valves: allow air to enter the cylinder and exhaust gases to escape, operated by the camshaft.
• Camshaft: operates the valves, with separate cams for the inlet and exhaust valves, driven by the crankshaft.
• Flywheel: maintains uniform engine speed by carrying the crankshaft through the intervals when it is not receiving power from a piston.

Selection of Tractor

• Factors to consider when selecting a tractor:
  • Land holding: 1 hp for every 1 hectare of land.
  • Cropping pattern: less than 1.0 hectare/hp for multiple crops.
  • Soil condition: tractor with less wheel base, higher ground clearance, and low overall weight for lighter soil.
  • Climatic condition: air-cooled engines for hot and high-altitude areas.
  • Repairing facilities: availability of dealer with technical skills for repair and maintenance.
  • Running cost: tractors with less specific fuel consumption.
  • Initial cost and resale value: consider the resale value and initial cost.

Control Board or Dash Board of a Tractor

• Components of the control board:
  • Main switch
  • Throttle lever
  • Decompression lever
  • Hour meter
  • Light switch
  • Horn button
  • Battery charging indicator
  • Oil pressure indicator
  • Water temperature gauge

Tractor Tyres and Front Axle

• Tyres: available in many sizes with ply ratings, indicating comparative strength.
• Front axle: unit on which front wheels are mounted, comprising idler wheels for steering.

Hitching System of Tractor Drawn Implements

• Types of tractor-drawn implements:
  • Trailed type: pulled and guided from a single hitch point.
  • Semi-mounted type: attached to the tractor along a hinge axis.
  • Mounted type: attached to the tractor, controlled directly by the tractor steering unit.

Important Terms Connected with Tractors

• Wheelbase: horizontal distance between the front and rear wheels.
• Ground clearance: height of the lowest point of the tractor from the ground surface.
• Track: distance between the two wheels of the tractor on the same axle.
• Turning space: diameter of the smallest circle described by the outermost point of the tractor.
• Cage wheel: wheel or attachment with spaced cross bars for improving traction in wet fields.

Power Tiller

• A prime mover controlled by an operator walking behind it.
• Also known as a hand tractor or walking-type tractor.
• Originated in Japan in the 1920s, with the first successful model designed in 1947.
• Power tiller is a single-axle walking-type tractor, with an optional riding seat.