The heat engine, in order to achieve energy conversion, first through the combustion process of the chemical energy into heat energy, and then the heat energy into mechanical energy. In steam power equipment, realize the first step in the boiler, the second step is to implement in a steam engine or turbine in steam power equipment is still. The important significance, but due to the large unit power equipment weight, so the requirements of equipment to some occasions moving, especially as a means of transport engine, steam power equipment is too heavy. So, starting from the end of the eighteenth Century, has the power to make fuel can be burned in the cylinder, to reduce engine weight. The chemical energy into heat energy and heat energy into mechanical energy power machine two processes in cylinder is called the engine. To the actual use of the internal combustion engine until the second half of the nineteenth Century was made.
In 1876, the German engineer Otto (N.A.Ono, 1832 - 1891) made with gas for four stroke internal combustion engine fuel, thereafter, turbine quickly improved, and it has been applied more and more widely.
The four stroke engine of Otto cycle is known to the solid circulation, or is called the constant volume heat engine cycle, as shown in Figure 2 - 3 - 3 (a) in Figure 2 - 3 - 3 (b) is the cycle of P - V diagram and corresponding to four cycle diagram.O is a 1 suction
Process, then the cylinder suction gas (or gas) and air mixtures. Get to the point of "1", the intake valve closed, the piston reaches BDC, and then to move in the opposite direction of.1 - 2 is the compression process, the mixed gas is compressed, the piston will reach a point on "2", mixed the gas is ignited by the spark. Because the mixed gas has reached a high temperature in the process of compression ignition combustion, very quickly, the piston is not downward movement, a rapid rise in cylinder pressure, the combustion process of 2 - 3 shows, this close to constant volume heating. The "3" points. 3 - 4, the end of combustion process, work out the gas expansion. "4", the piston reaches BDC again, the exhaust valve open, the cylinder pressure suddenly dropped to slightly higher than the atmospheric pressure.4 o 'exhaust process
The internal combustion engine, state change working experience is the open cycle is very complex. In order to facilitate the process of internal combustion engine thermodynamic analysis, can make the following idealized
Hypothesis:
(1) the suction process outside the required driving power and exhaust of the push work can be considered positive and negative phase offset, thus neglected. In fact, because the near atmospheric pressure exhaust and suction, and this part of power than the entire cycle of the work is quite small, so this simplification can think is reasonable.
(2) the combustion process as heat source heating process of refrigerant, and process of 2 -- 3 can be considered constant volume heating process.
(3) between the outside world and ignore the working medium in the compression and expansion in the process of heat exchange, so the process of 1 - 2 and 3 - 4 can be regarded as adiabatic compression and process
The expansion process.
(4) exhaust and suction process with a constant volume heat release process replacing, as if there is no air no air intake, thus, the loop into a closed loop.
In the simplified L, lit the strict y graph of ideal cycle type four stroke internal screw machine as shown in Figure 2 - 3 - 4 shows, as shown in the figure, the constant volume heating cycle consists of two constant volume process and two |
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