Mechanical knowledge base: "Internal combustion engine"

An internal combustion engine is a heat engine that mixes liquid or gaseous fuel with air and then directly enters the internal combustion engine to generate heat energy and convert it into mechanical energy. The internal combustion engine has the characteristics of small size, small mass, easy movement, high thermal efficiency, and good starting performance. However, the internal combustion engine generally uses petroleum fuel, and the emitted exhaust gas has a high content of harmful gases.

Introduction to the internal combustion engine

An internal combustion engine is a kind of power machinery. It is a heat engine that directly converts the heat energy emitted by the combustion of the fuel inside the machine into power.

The internal combustion engine in a broad sense includes not only a reciprocating piston type internal combustion engine, a rotary piston type engine, and a free-piston type engine, but also a rotary impeller type gas turbine, a jet engine, etc., but the so-called internal combustion engine means a piston type internal combustion engine.

Piston-type internal combustion engines are most commonly used as reciprocating pistons. The piston type internal combustion engine mixes fuel and air and burns in its cylinder, and the released thermal energy causes the high temperature and high pressure gas in the cylinder. The gas expansion pushes the piston to work, and then outputs the mechanical work through a crank-link mechanism or other mechanism to drive the driven machine to work.

Common diesel engines and gasoline engines convert internal energy into mechanical energy by changing the internal energy through work.

Composition of internal combustion engine

The components of the reciprocating piston internal combustion engine mainly include a crank connecting rod mechanism, a body and a cylinder head, a gas distribution mechanism, an oil supply system, a lubrication system, a cooling system, and a starting device.

The cylinder is a cylindrical metal part. The sealed cylinder is the source of the work cycle and power generation. Each cylinder with a cylinder liner is installed in the body, and its top end is closed with a cylinder head. The piston can reciprocate in the cylinder liner and close the cylinder from the lower part of the cylinder, thus forming a sealed space where the volume changes regularly. The fuel burns in this space, and the generated gas power drives the piston movement. The reciprocating movement of the piston pushes the crankshaft through the connecting rod for rotation, and the crankshaft then outputs power from the flywheel end. The crank-link mechanism consisting of a piston group, a connecting rod group, a crankshaft, and a flywheel is the main part of the internal combustion engine transmission power.

The piston group consists of a piston, a piston ring, a piston pin, and the like. The piston has a cylindrical shape and is equipped with a piston ring to seal the cylinder when the piston reciprocates. The above several piston rings are called gas rings, which are used to close the cylinder and prevent gas leakage in the cylinder. The lower ring is called the oil ring and is used to scrape the excess oil on the cylinder wall to prevent the oil from intruding. cylinder. The piston pin has a cylindrical shape. It penetrates into the pin hole of the piston and the small head of the connecting rod to connect the piston and the connecting rod. The large end of the connecting rod is divided into two halves and is connected by a connecting rod screw which is connected to the crank pin of the crankshaft. When the connecting rod is working, the small end of the connecting rod reciprocates along with the piston. The large end of the connecting rod rotates with the crank pin around the axis of the crankshaft, and the shaft between the heads of the connecting rods makes a complex swinging motion.

The role of the crankshaft is to convert the reciprocating motion of the piston into a rotary motion, and the work done by the expansion stroke is transmitted through the flywheel mounted on the rear end of the crankshaft. The flywheel can store energy so that the other strokes of the piston can work normally and the crankshaft can rotate evenly. In order to balance the inertial force and to reduce the vibration of the internal combustion engine, a balancing device is also mounted on the crankshaft crankshaft.