Steam machine

Classification Of Alternative Engines

Classification of alternative engines

Alternative engines can be classified in many different ways. The main forms of classification are the following:

  • According to the arrangement of the cylinders in the engine
  • According to the displacement
  • According to the compression ratio
  • According to the diameter and stroke ratio
  • According to the number of movements of each cycle

Classification according to the arrangement of the cylinders

A typical way of classifying the reciprocating engine is to use the number and arrangement of the cylinders. In this way we have:

  • Linear alternative motor. The inline engine is a motor with all the cylinders aligned in the same row, without displacements. They have been used in motorcycles, automobiles, locomotives and airplanes. It is usually available in configurations of 2, 4, 5 and 6 cylinders.
  • Alternative engine in V. The engine in V is an arrangement in which the cylinders are grouped into two blocks or rows of cylinders, where they form a letter V. All the cylinders converge on the same crankshaft.â €
  • Radial alternative engine. It is also known as a star engine. This alternative engine is a type of arrangement in which the cylinders are located radially with respect to the crankshaft, forming a star.

Classification of alternative engines according to displacement

Another way to classify the alternative engines is to do it depending on the cubic capacity.

The displacement is the total volume of displacement of gas by the pistons that move in the cylinders. Usually the displacement is measured in liters or cubic centimeters. In other words, displacement is the geometric volume occupied by the set of pistons from the bOttom dead center (PMI) to the highest (PMS), also called top dead center. The displacement gives a good measure of the working capacity that an engine can have.

Classification according to the compression ratio

Another criterion for classifying the different types of reciprocating engine is to do it by means of its compression ratio.

The compression ratio is the relation between the volume of the cylinder. Another way to express it would be the moment when the piston is at the bOttom of its stroke (bOttom dead center), and the volume when the piston is at the top of its stroke (top dead center).

This compression ratio affects the performance of Stirling engines and internal combustion engines. In the case of internal combustion engines, on this website we analyze the Otto cycle for the gasoline engine and the diesel cycle for the diesel engine.

Classification according to diameter and stroke ratio

The diameter / stroke ratio is the ratio of the diameter of the piston, or hole, to the length of the stroke inside the cylinder, or stroke. Depending on this relationship we have:

  • Alternative square motors: If this relation is close to 1.
  • Overriding alternative motors: If the diameter / stroke ratio is greater than 1, that is, the hole is larger than the stroke.
  • Sub-squared alternetical motors: If the ratio is less than 1, that is, the stroke is larger than the hole.

Classification depending on the number of movements in each cycle

This classification of the alternative engines depends on their operating cycle. In them two types of motor are distinguished.

  • The two-stroke engine.
  • The four-stroke engine.
  • The six-stroke engine. This type of cycle is very unusual.

Internal combustion engines work through a sequence of admission movements and elmination of gases in the cylinder. These movements are repeated cyclically and an engine is said to be 2-stroke, 4-stroke or 6-stroke depending on the number of steps necessary to complete a cycle.


Published: March 13, 2018
Last review: March 12, 2018