The Numerical Analysis Of The Diesel Exhaust Particulate Test System

The impact of the energy crisis prompts diesel vehicles which has a hugeadvantage of power and economy occupy an increasing proportion, while the diesel hasa major flaw in particulate emissions. It requires high-precision measurement system.Most of the domestic diesel engine research and production units usually buy foreignequipments, which domestic research institutes cann’t afford it. For the features ofschool internal combustion engine laboratory building, this topic is based on theGB17691-2001regulatory requirements, develops low-cost and high-precision dieselparticulate test system to meet the school diesel exhaust particulate fileds of teachingand research needs.Aimed at the LF4105ZQ diesel engine, according to the diesel particulate testsystem requirements of GB17691-2001, we establish the basic structure size of thediesel exhaust particulate test system. In accordance with the constant dilution ratiodesigning ideas, using hydrodynamic theory, we complete the relevant equipmentsselection. We also complete the design of the overall structure of the system.The diesel exhaust particulate test system consists of two parts, dilution andsampling part. To meet the temperature and uniformity requirement of the dilutedexhaust gas, the dilution part uses a low static pressure dilution technique of venturitube. With the Ansys Workbench CFD fluid calculation module, we carry out parameterstructure numerical calculation to the dilution part of the diesel exhaust particulatemeasurement system. Analyze the structure of the venturi tube size and the dilution partflow filed difference, regard the speed and energy loss of the mixed gas as theevaluation index, we determine the optimal structure of the dilution part.With ANSYS FUENT software to study the sampling location of the dilutedexhaust gas under the optimal venturi tube. Using the density-based solver,semi-implicit SIMPLE algorithm, based on the finite volume method and thenon-responsive component transport equation, energy equation, k-eturbulence modeland low Reynolds number near-wall treatment, we analyze the three-dimensional steadyflow of the dilution tunnel. By observing the the proportion of diesel exhaust fromdifferent cross section and considering the heat exchange, turbulence, we determine theoptimal sampling location.In order to explore the adaptability of the designed structure of the dilution part todifferent diesel engines, we compare the exhaust dilution numerical results of threedifferent diesel engines under rated speed, including the velocity field, temperature fieldand species transport, etc. The results show that the design of this shunting dilution sampling system is reasonable. It can be used for particulate measurements for smalldiesel engine of displacement of about2~4L.According to the sampling requirements, we design the sampling part. We alsocalculate the effective sampling rate of the sampler. Use a porous medium model toanalog the three-dimensional model of filter paper for numerical calculation.Regardingthe permeation rate and the flow resistance of the sampler as the evaluation index, wedetermine the optimal structure of the sampler.Through the above work, the topic establishes the diesel exhaust particulate testsystem for research and teaching in schools. It lays a good foundation for furtherstudying particle emission law and takeing strategies to control the particle emissions. Ithas an important significance.