Marine diesel engine is a kind of diesel engine used on ships. Its working principle is as follows:
A stream of fresh air is pumped into the engine cylinder and then compressed to high pressure by the moving piston. When air is compressed, its temperature rises, so that it can ignite the fine fuel injected into the cylinder. The combustion of fuel adds more heat to the charged air, causing expansion, forcing the generator piston to do work on the crankshaft, and then driving the propeller of the ship through other shafts.
The operation between two fuel injections is called the duty cycle. In a four-stroke diesel engine, this cycle needs to be completed through four different strokes of the piston, namely intake, compression, expansion and exhaust. If we combine intake and exhaust with compression and expansion, a four-stroke engine becomes a two-stroke generator.
When the piston rises from the bottom of its stroke (that is, the bottom dead center), the two-stroke cycle begins, at which time the air inlet on the cylinder side opens. At this time, the exhaust valve is also opened, fresh air is filled into the cylinder, and the residual exhaust gas of the last stroke is blown out through the opened exhaust valve. The valve burst.
When the piston moves to about one-fifth of its stroke in the morning, it closes both the intake and exhaust valves, so the temperature and pressure rise to very high values.
When the piston reaches the top of its stroke (i.e. top dead center), the fuel valve injects the fuel into the high-temperature air in the cylinder in the form of fine mist, and the fuel burns immediately, and the heat makes the pressure rise rapidly. In this way, the expanding gas forces the piston to move downward in the power stroke.
When the piston moves down to a little more than half of the stroke, the exhaust valve opens, and the high-temperature gas begins to flow out through the exhaust valve due to its own pressure, assisted by the fresh air entering the air inlet. With the further downward movement of the piston, the air inlet opens. Then, another cycle begins.
In a two-stroke engine, the crankshaft rotates once to make a power stroke, while in a four-stroke engine, it needs to rotate twice to make a power stroke, which is why a two-stroke engine can do about twice as much work as a four-stroke engine under the same size. In current practical use, the output power of a two-stroke engine is about 80% higher than that of a four-stroke engine with the same cylinder diameter and speed. With the increase of engine power, two-stroke generator is widely used as the main engine of large ships. Since 19 19 Cummins introduced the first Cummins marine diesel engine when it was founded, Cummins has been committed to the research and development and production of marine diesel engines. 1925, the company put the first fully enclosed marine diesel engine on the market; By 1970s, V903, V504 and V 555 series marine diesel engines occupied the dominant position in the market. In 1980s, Cummins produced series B and C diesel engines; 1993, marine engine headquarters moved to Charlestown, South Carolina, USA. Since then, the sales of marine engines have been continuously refurbished. By 1998, the Cable Explorer equipped with four Cummins diesel engines had set a new global navigation record.
At present, Cummins marine engine has four design centers and three research and development centers around the world, and its products cover the power range of 60 HP to 6000 HP. Moreover, because of its exquisite size, compact structure, simple installation and quick after-sales service, it is widely used in recreational ships such as yachts and fishing boats, commercial ships such as tugboats, tugboats and work boats, and even oil production platforms and military and police ships. Nowadays, we are not only satisfied with providing diesel engines to our customers, but also will realize more' providing power'.
Cummins Marine Machinery Department is located in Shanghai because Shanghai is one of the three major shipbuilding bases in China. The engine department includes application engineers, marketing personnel and after-sales service personnel, all of whom are engineers majoring in mechanical or shipbuilding design. They can only take up their posts after strict professional training and obtaining the certificate of professional engine technician. Among them, application engineers keep close contact with ship design units and shipyards, participate in the construction and design of ships using Cummins engines or auxiliary machines, and are responsible for providing optimized design schemes. Marketing and after-sales service personnel work closely with other departments of Cummins in China, for example, a complete workflow has been formed in Shanghai Free Trade Zone, and efficient results have been achieved.