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an internal-combustion engine with compression ignition. Ignition occurs in the cylinder of a diesel when fuel is injected into air heated to a high temperature as a result of compression by the piston. The diesel is named after the German engineer R. Diesel, who built the first engine with compression ignition in 1897. The diesel operates on fuel that is considerably cheaper than gasoline. There are also gas engines that operate on the diesel cycle.
Diesels are among the most economical heat engines. The specific fuel consumption of the best diesels is about 190 g per kilowatt-hr [g/(kW·hr)J, or 140 g per hp-hr [g/(hp·hr)], but for most types of diesels it does not exceed 270 g/(kW·hr), or 200 g/(hp·hr), at nominal power. Such fuel-consumption figures correspond to an efficiency of 31–44 percent (the efficiency of carburetor internal-combustion engines is usually 25–30 percent). The speed of shaft rotation in a diesel is usually 100–3,000 rpm, and only in isolated instances does it reach 4,000-4,500 rpm. Increases in the speed of rotation of a diesel are limited by the time required for carburetion and combustion of the fuel. Detonation does not occur in a diesel, so that the cylinder diameter is virtually unlimited, and in ship diesels it may be as great as 1 m; the power of a single unit exceeds 30,000 kW (40,000 hp). The weight per unit of power in a diesel is 3–80 kg/kW (2-60 kg/hp). The service life of a diesel is 5,000-80,000 hours.
Diesels are classified in terms of their combustion chamber design. In diesels with an open combustion chamber, the fuel is evenly distributed throughout the chamber in the process of carburetion by a large number of jets. In swirl-chamber diesels a stream of air is twisted as it is forced into the swirl chamber in the compression process, and the fuel is injected into the rapidly spinning vortex. In precombustion diesels, carburetion is produced by the entry of air and fuel to the main combustion chamber from the precombustion chamber, which is caused by the onset of combustion and the increased pressure in the precombustion chamber. Carburetion from a film is typical of the “chamber-in-piston” design, where fuel is supplied to the wall of the chamber and its vapors are caught up by the swirling air and well mixed.
Diesel engines are of various designs. Switch engines and ships in the USSR use V-12 diesels with water cooling and gas-turbine supercharging. The main diesel locomotives are vertical in-line two-stroke diesels with uniflow scavenging. Slow-speed ship diesels are the largest: for example, a two-stroke, in-line diesel with combined valve-and-port scavenging made by the Burmeister og Wain firm in Denmark has cylinders 840 mm in diameter, a piston stroke of 1,800 mm, a weight of 885 tons, and a height of 12.1 m. Ship diesels are often of the crosshead type. They sometimes operate without crankshafts. Less frequently, W-shaped or X-shaped diesels are used—that is, instead of two cylinder blocks as in a V-shaped diesel, these engines have three or four blocks. There are also star-shaped diesels with radially placed cylinders, and even multistar types (blocks of stars) with up to 42 or more cylinders.
Diesels are widely used. Their most extensive use is in tractor construction; their use is becoming more widespread in motor-vehicle design. About 50 percent of the locomotives in the USSR are diesels, as are most locomotives in the USA. Motor ships with diesel and diesel-electric drive have virtually replaced steamships in the river fleet. Diesels power mobile military equipment, such as tanks and rocket launchers. They are extensively used as mobile and stationary power generators in regions far from electric power lines. Diesels are being improved by increasing unit power, speed of revolution, reliability, and service life and by expanding the assortment of fuels used (multifuel engines).
REFERENCESDizeli: Spravochnik. Edited by V. A. Vansheidt. Moscow-Leningrad, 1964.
Ustroistvo i rabota porshnevykh i kombinirovannykh dvigatelei, 2nd ed. Moscow, 1970.
Ricardo, H. R. The High-speed Internal-combustion Engine. London, 1955.
D. N. VYRUBOV and V. P. ALEKSEEV