IMPROVING THE ACCURACY OF SYSTEMS FOR GRAVIMETRIC CONTROL OF PARTICULATE MATTER IN EXHAUST GASES OF TRANSPORT DIESEL ENGINES

The requirements of regulatory documents - UNECE Regulations R-49, R-96, international standard ISO 8178, etc. were analyzed regarding the technical characteristics and conditions of use of reference full-flow and alternative partial-flow systems (tunnels) for diluting the exhaust gases of transport diesel engines with air and carrying out gravimetric control of the content of solid particles in them. The world and domestic experience of operating dilution tunnels of various types - full-flow with 1st and 2nd dilution lines and partial-flow mini- and micro-tunnels and partial-flow mini- and micro-tunnels were studied, which made it possible to establish empirical dependencies for evaluating the degree of influence of the temperature regimes of gas sampling on the accuracy of measurements of mass emissions particulate matter in different modes of diesel operation. Mathematical models have been developed to determine the sample temperatures of diluted exhaust gases in tunnels of various types and to estimate the resulting measurement error of the normalized average operational emission of diesel particulate matter - the PM indicator. Based on the results of environmental tests of transport diesel engines 1Ch12/14 and 4ChN12/14 according to the 13-step ESC test cycle and developed mathematical models, calculation studies were carried out to assess the effect on the accuracy of a mini-tunnel with a diameter of 10 cm and a micro-tunnel with a diameter of 3 cm of the sampling temperature regimes, which were compared with a reference tunnel with a diameter of 46 cm. The research results proved the expediency of adjusting the temperature of the sample in the micro-tunnel to increase its accuracy by eliminating the significant methodical errors of measuring the PM indicator, which amount to -1.6 ... -1.7%. It was established that in the mini-tunnel the corresponding errors are not significant and amount to -0.3 ... -0.4%, which indicates that there is no need to adjust the temperature of the sample in this system.