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Applied mechanics |Прикладная механика

Lesson 8

Read the text: Operation

All internal combustion engines depend on the exothermic chemical process of combustion: the reaction of a fuel, typically with the oxygen from the air, although other oxidizers such as nitrous oxide may be employed. 

The most common modern fuels are made up of hydrocarbons and are derived mostly from petroleum. These include the fuels known as diesel fuel, gasoline and petroleum gas, and the rarer use of propane gas. Most internal combustion engines designed for gasoline can run on natural gas or liquefied petroleum gases without major modifications except for the fuel delivery components. Liquid and gaseous biofuels, such as ethanol and biodiesel (a form of diesel fuel that is produced from crops that yield triglycerides such as soybean oil) can also be used. Some can also run on hydrogen gas.

All internal combustion engines must achieve ignition in their cylinders to create combustion. Typically engines use either a spark ignition (SI) method or a compression ignition (CI) system. In the past, other methods using hot tubes or flames have been used. Electrical/gasoline-type ignition systems (that can also run on other fuels, as previously mentioned) generally rely on a combination of a lead-acid battery and an induction coil to provide a high-voltage electrical spark to ignite the air-fuel mix in the engine's cylinders. This battery can be recharged during operation using an electricity-generating device such as an alternator or generator driven by the engine. Gasoline engines take in a mixture of air and gasoline and compress to less than 185 psi and use a spark plug to ignite the mixture when it is compressed by the piston head in each cylinder.

     Diesel Engine ignition systems, such as the diesel engine and HCCI engines, rely solely on heat and pressure created by the engine in its compression process for ignition. The compression that occurs is usually more than three times higher than a gasoline engine. Diesel engines will take in air only, and shortly before peak compression, a small quantity of diesel fuel is sprayed into the cylinder via a fuel injector that allows the fuel to instantly ignite. HCCI type engines will take in both air and fuel but continue to rely on an unaided auto-combustion process due to higher pressures and heat. This is also why diesel and HCCI engines are also more susceptible to cold starting issues, though they will run just as well in cold weather once started. Most diesels also have battery and charging systems; however, this system is secondary and is added by manufacturers as luxury for ease of starting, turning fuel on and off (which can also be done via a switch or mechanical apparatus), and for running auxiliary electrical components and accessories. Most old engines, however, rely on electrical systems that also control the combustion process to increase efficiency and reduce emissions.

1. Match the left part with the right

2. Complete the sentences with the suggested words: luxury, charging, fuel, auxiliary

Most diesels also have battery and _______ systems; however, this system is secondary and is added by manufacturers as _______ for ease of starting, turning _______ on and off (which can also be done via a switch or mechanical apparatus), and for running _______ electrical components and accessories.