Mathematical modeling of diesel engine operation mode influence on mass emission of particulate matter with exhaust gases using microtunnel

Abstract

The work is devoted to solving an urgent scientific and prac-tical task: establishing mathematical models that describe the effect of op-erating modes of diesel engines on the content in the exhaust gases of a dangerous pollutant – particulate matter (PM). The purpose of the work has been to create and study the accuracy and practical suitability of the calcu-lation method estimating concentrations and emissions with exhaust gases PM by means of mathematical modeling of the influence on them of param-eters that determine steady-state and unsteady diesel operation modes. The following research methods have been used in the work, such as: analysis and synthesis of information, mathematical modeling, experimental studies, and computational experiment. The studies have been carried out on the basis of the motor stand of a 4ChN12/14 autotractor diesel equipped with a partial-flow system for diluting EG with air – MKT-2 microtunnels. Mea-surements of mass and volume concentrations – cpt (g/kg) and Cpt (g/mn3), mass – PTmass (g/h) and specific – PTp (g/kWh) PM emissions have been carried out by the gravimetric method with errors of ± 3 .. 10% in accor-dance with the requirements of regulatory documents – ISO8178 standard, UNECE Rules R-49, R-96, etc. The parameters, which determine the mode of operation of the diesel engine, have been considered: during the studyof the steady-state modes – the number of revolutions of the engine crank-shaft (n, min-1) and the load (L,%); in the study of unsteady modes – the parameters n and L and the rate of change over time – Δn/Δt and ΔL/Δt. As a result of studying concentrations and emissions PM at steady operation modes, the type has been ed and the most reliable regression depen-dence has been established – a second-order polynomial model that allows us to estimate the values of Cpt, PTmass and PTp in the ranges of variation of the parameters n and L – 1000 ... 2000 min-1 and 25 ... 100%. The RSM of the established dependencies when determining the indicated values is comparable with the errors of microtunnels MKT-2 and is ± 0.0042 g/mn3, ± 2.02 g/h, ± 0.077 g/kWh. A dependence for indirectly determining the mass concentration of PM in the exhaust gases at unsteady diesel operating modes, which are characterized by a duration of 10 ... 30 s and ranges of variation of the parameters n, L, Δn/Δt and ΔL/Δt, given in dimensionless form: 0.4 ... 0.8, 0.3 ... 1.0, -0.2 ... 0.2 and -0.35 ... 0.35, respectively, has been established. The deviation of the calculated and experimental data when using this dependence is ± 0.005 ... 0.006 g/kg, which is comparable with the sensitivity limit of MKT-2. A satisfactory accuracy and practical suitability of the indirect optical-gravimetric method for controlling PM concentrations and emissions at steady-state diesel engine operating modes were proposed and experimentally confirmed.