1、本科 生毕业 设计（论文）外文翻译 1 A diesel engine works 【 Abstract】 In diesel engine cylinder, the piston part of the cycle in the compressed gases, and in another part of the work cycle of the combustion gas mixture within the cylinder so the piston top surface expansion high pressure (about 116 120Kgf/cm2)under
2、 high temperature (about 569C) gas role, and the pressure through the piston pin, connecting rod to the crankshaft. Can be seen that the piston is a long time under high temperature and high pressure in continuous reciprocating motion of the load, its load and working conditions were appalling. Duri
3、ng the design process of the piston will be designed to ensure long-term stability of the work piston. The design of the work done by a brief introduction as follows:Diesel Engine Piston 180C reasonable processing technology is important, the role of parts and technology program analysis, preparatio
4、n of rough form and process manufacturing line, through the analysis, comparison, use of the relative concentration of processing programs, and ultimately more reasonable to determine the mechanical line processing. The development process of rough line the main consideration, finishing arrangements
5、, choice of processing methods, centralized and decentralized processes, such as processing the order requirements. Then determine the allowance, process size, after the analysis of the characteristics of the process, select the appropriate processing equipment and technical equipment. Calculated lo
6、ok-up table to determine the next major piston cutting process and the mapping of processes card, the design of the final fixture. Fixture design, it is necessary to take various aspects into account, the strict requirements of the fixture a direct impact on the surface of the workpiece processing p
7、osition accuracy. Therefore, the machine tool design fixture design is an important task is the processing of one of the most active. During the graduation project in a specially designed positioning accuracy, simple structure and easy-to-use precision pin hole boring jig. Keywords: Piston； Technolo
8、gy； processing equipment； cutting； Fixture Any type of machine that obtains mechanicalenergy directly from the expenditure of the chemical energy of fuel burned in a combustion chamber that is an integral part of the engine. Four principal types of internal-combustion engines are in general use: the
9、 Otto-cycle engine, the diesel engine, the rotary engine, and the gas turbine. For the various types of engines employing the principle of jet propulsion, see Jet Propulsion； Rocket. The Otto-cycle engine, named after its inventor, the German technician Nikolaus August Otto, is the familiar gasoline
10、 engine used in automobiles and airplanes； the diesel engine, named after the French-born German engineer Rudolf Christian Karl Diesel, operates on a different principle and usually uses oil as a fuel. It is employed in electric-generating and marine-power plants, in trucks and buses, and in some au
11、tomobiles. Both Otto-cycle and diesel engines are manufactured in 本科 生毕业 设计（论文）外文翻译 2 two-stroke and four-stroke cycle models.The essential parts of Otto-cycle and diesel engines are the same. The combustion chamber consists of a cylinder, usually fixed, that is closed at one end and in which a clos
12、e-fitting piston slides. The in-and-out motion of the piston varies the volume of the chamber between the inner face of the piston and the closed end of the cylinder. The outer face of the piston is attached to a crankshaft by a connecting rod. The crankshaft transforms the reciprocating motion of t
13、he piston into rotary motion. In multicylindered engines the crankshaft has one offset portion, called a crankpin, for each connecting rod, so that the power from each cylinder is applied to the crankshaft at the appropriate point in its rotation. Crankshafts have heavy flywheels and counterweights,
14、 which by their inertia minimize irregularity in the motion of the shaft. An engine may have from 1 to as many as 28 cylinders. The fuel supply system of an internal-combustion engine consists of a tank, a fuel pump, and a device for vaporizing or atomizing the liquid fuel. In Otto-cycle engines thi
15、s device is either a carburetor or, more recently, a fuel-injection system. In most engines with a carburetor, vaporized fuel is conveyed to the cylinders through a branched pipe called the intake manifold and, in many engines, a similar exhaust manifold is provided to carry off the gases produced b
16、y combustion. The fuel is admitted to each cylinder and the waste gases exhausted through mechanically operated poppet valves or sleeve valves. The valves are normally held closed by the pressure of springs and are opened at the proper time during the operating cycle by cams on a rotating camshaft t
17、hat is geared to the crankshaft. By the 1980s more sophisticated fuel-injection systems, also used in diesel engines, had largely replaced this traditional method of supplying the proper mix of air and fuel. In engines with fuel injection, a mechanically or electronically controlled monitoring syste
18、m injects the appropriate amount of gas directly into the cylinder or inlet valve at the appropriate time. The gas vaporizes as it enters the cylinder. This system is more fuel efficient than the carburetor and produces less pollution. In all engines some means of igniting the fuel in the cylinder m
19、ust be provided. For example, the ignition system of Otto-cycle engines described below consists of a source of low-voltage, direct-current electricity that is connected to the primary of a transformer called an ignition coil. The current is interrupted many times a second by an automatic switch cal
20、led the timer. The pulsations of the current in the primary induce a pulsating, high-voltage current in the secondary. The high-voltage current is led to each cylinder in turn by a rotary switch called the distributor. The actual ignition device is the spark plug, an insulated conductor set in the w
21、all or top of each cylinder. At the inner end of the spark plug is a small gap between 本科 生毕业 设计（论文）外文翻译 3 two wires. The high-voltage current arcs across this gap, yielding the spark that ignites the fuel mixture in the cylinder. Because of the heat of combustion, all engines must be equipped with
22、some type of cooling system. Some aircraft and automobile engines, small stationary engines, and outboard motors for boats are cooled by air. In this system the outside surfaces of the cylinder are shaped in a series of radiating fins with a large area of metal to radiate heat from the cylinder. Oth
23、er engines are water-cooled and have their cylinders enclosed in an external water jacket. In automobiles, water is circulated through the jacket by means of a water pump and cooled by passing through the finned coils of a radiator. Some automobile engines are also air-cooled, and in marine engines
24、sea water is used for cooling. Unlike steam engines and turbines, internal-combustion engines develop no torque when starting, and therefore provision must be made for turning the crankshaft so that the cycle of operation can begin. Automobile engines are normally started by means of an electric mot
25、or or starter that is geared to the crankshaft with a clutch that automatically disengages the motor after the engine has started. Small engines are sometimes started manually by turning the crankshaft with a crank or by pulling a rope wound several times around the flywheel. Methods of starting lar
26、ge engines include the inertia starter, which consists of a flywheel that is rotated by hand or by means of an electric motor until its kinetic energy is sufficient to turn the crankshaft, and the explosive starter, which employs the explosion of a blank cartridge to drive a turbine wheel that is co
27、upled to the engine. The inertia and explosive starters are chiefly used to start airplane engines. The ordinary Otto-cycle engine is a four-stroke engine； that is, in a complete power cycle, its pistons make four strokes, two toward the head (closed head) of the cylinder and two away from the head.
28、 During the first stroke of the cycle, the piston moves away from the cylinder head while simultaneously the intake valve is opened. The motion of the piston during this stroke sucks a quantity of a fuel and air mixture into the combustion chamber. During the next stroke, the piston moves toward the
29、 cylinder head and compresses the fuel mixture in the combustion chamber. At the moment when the piston reaches the end of this stroke and the volume of the combustion chamber is at a minimum, the fuel mixture is ignited by the spark plug and burns, expanding and exerting a pressure on the piston, w
30、hich is then driven away from the cylinder head in the third stroke. During the final stroke, the exhaust valve is opened and the piston moves toward the cylinder head, driving the exhaust gases out of the combustion chamber and leaving the cylinder ready to repeat the cycle. The efficiency of a modern Otto-cycle engine is limited by a number of factors, including losses by cooling and by friction. In general, the efficiency of such engines is
