Chapter 1 Basic structure and principle of the engine Section 1 Overall construction Those machine that can make some form of energy into mechanical energy can be called the engine,such as heat engines,hydraulic engines and wind engines. Heat engine is the machine that can make the heat generated by burning fuel into mechanical energy.Heat engines are divided into two categories:external combustion and internal combustion heat engines. The combustion of fuel is out of the engine that is called the external combustion heat engine;the combustion of fuel is directly in the internal engine known as the internal combustion heat engine. 1.Classification of Internal Combustion Engine (1)Classified by the type of fuel. (2)Classified by the way of fire. (3)Classified by the number of working cycle trips. (4)Classified by the number of cylinders and arrangement. (5)Classified by the way of cooling. (6)Classified by the way of inlet. 械电子工程学度 Automobile and Tractor Northwest A&F University Automobile and Tractor Northwest A&F University Chapter 1 Basic structure and principle of the engine Those machine that can make some form of energy into mechanical energy can be called the engine， such as heat engines, hydraulic engines and wind engines. Heat engine is the machine that can make the heat generated by burning fuel into mechanical energy. Heat engines are divided into two categories: external combustion and internal combustion heat engines． The combustion of fuel is out of the engine that is called the external combustion heat engine; the combustion of fuel is directly in the internal engine known as the internal combustion heat engine. 1. Classification of Internal Combustion Engine (1) Classified by the type of fuel. (2) Classified by the way of fire. (3) Classified by the number of working cycle trips. (4) Classified by the number of cylinders and arrangement. (5) Classified by the way of cooling. (6) Classified by the way of inlet． Section 1 Overall construction