Steam and Internal Combustion Engines: Principles and Parts

Thermodynamics and Thermal Energy

Thermodynamics studies thermal energy and its transformation into other forms of energy. An external combustion engine is a system where combustion takes place outside the engine.

The Newcomen steam engine utilized a rectilinear alternative motion to pump water from mines and canals. In 1769, engineer James Watt perfected the design by converting it into rotary motion using a crank mechanism.

Basic Elements of the Steam Engine

• Piston and Cylinder: The cylinder is the part of the machine where steam pressure expands. It consists of a metal body containing a cylindrical disk called a plunger that fits the internal wall and moves in a rectilinear alternative motion. A cylindrical bar, or stem, is attached to the piston and exits through an adjusted hole. When steam enters the cylinder, a mechanism called the dealer pushes the piston, moving the stem toward the other end before returning to its original position to restart the cycle.
• The Crank: A bar attached to one end of the stem that allows for rotation at a joint. The other end turns a wheel called the flywheel through a crank.
• The Flywheel: A thick, heavy wheel that maintains momentum through inertia. This is often connected via a belt pulley to transmit circular movement to a shaft located along the busbars.
• The Watt Governor: A mechanism that rotates while the machine is running to maintain a constant speed. It uses two rotating balls that move vertically to regulate the system.

The Steam Turbine

The steam turbine converts potential thermal energy into kinetic energy. The available potential thermal energy is the difference between the state of steam entering the turbine and its state upon exit, known as the thermal jump.

Steam produced in a boiler reaches the turbine and passes through a crown of fixed blades called the distributor. The steam then hits curved blades on the rotor, generating torque that causes the axis to rotate. Steam turbines are classified as:

• Impulse: When steam expansion takes place entirely in the stator.
• Reaction: When steam expansion initiates in the stator and completes in the rotor.

Internal Combustion Engines

In internal combustion engines, combustion occurs inside a combustion chamber. These engines rely on a series of controlled explosions, often called explosion engines. They are categorized by their ignition method:

• Spark-Ignition (Otto Cycle): Consumes gasoline or pressurized liquefied gas.
• Compression Ignition (Diesel Cycle): Operates via high-pressure compression.

These engines may operate on a two-stroke or four-stroke cycle.

Combustion Engine Components

The Cylinder Head: An iron or light aluminum alloy piece that serves as the upper lid for the cylinders.