Abstract
Key words:
Critical flow, Venturi nozzle, Particulate emission, Full - flow dilution tunnel
ABSTRACT:
This paper presents the design methods of the full flow dilution tunnel and the critical flow venturi for the measurement of the particulate emission of CI engine. At the beginning, the appropriate type of dilution tunnel had been chosen, based on the international standards, user's needs and possibilities of the manufacturer and its co-operants. During the design process, a vast amount of restrictions specified in the standards for emission and venturis had to be taken into account. The necessary data which were required for the generation of basic concept were obtained from the numerous emission tests performed in the IMR Institute. A short algorhytm of calculation of the specific CFV venturi is also presented. Specific attention is paid to the problems of the measurement of particulate emission using the dilution method (the variations in the temperatures and composition of gases, mechanical pollutants in the gases), which makes impossible the adoption of the unique thermodynamic and flow parameters. Therefore, a method of evaluation for the two extreme cases which are expected during the tests is adopted, with the necessary data provided from the former emission measurements performed in the IMR Institute. It was shown that the variations of the physical and chemical properties of gases from one extreme case to the other have the influence which can not be neglected on the final results of the calculation of the tunnel and the venturi. Also both cases are significantly different from the results obtained for the gases whose thermodynamic parameters were accessible in the standards and literature.