柴油发动机中NO的激光诊断检测方案(尾气检测)

In 1897 Rudolf Diesel (1858-1913) demonstrated a new type of internal combustion (i.c.) engine in which the high compression pressure of about 35 times the atmospheric pressure led to a sufficiently high temperature to cause the auto-ignition of kerosine. Ever since diesel engines remained popular owing to their relatively high efficiencies and their ability to combust a large variety of fuels predominantly containing heavier crude oil components (i.e., longer aliphatic hydrocarbon chains). The original engines were 4-stroke engines in which one complete engine cycle takes two revolutions of the crank shaft. The latter transforms the translational energy of the piston in the cylinder into more convenient rotational energy with respect to vehicle propulsion. As schematically depicted in figure 1.1, in the first stroke the piston moves downwards in the cylinder and ambient air is taken in above the piston (inlet stroke). In the second stroke the inlet valve is closed and the piston moves upwards compressing the intake air (compression stroke). Just before the piston reaches its Top Dead Centre (TDC) fuel is sprayed in the combustion chamber and combustion takes place driving the piston downwards again in the third stroke (expansion stroke). Finally, the exhaust valve opens and the piston moves upwards again in the fourth stroke (exhaust stroke) pushing the combustion gases out of the cylinder. In later years 2- stroke diesel engines were developed in which, by using the space of the crank case below the piston as well, the work usually done in four strokes is now performed by one revolution of the crank shaft. Around 1940 the first turbo-charging diesel engines were developed in which the energy contained in the exhaust gases is used to compress the intake air in order to boost the power of the engines.