Study Of The Dynamic Characteristics Of Particulate Matter In Leakage Current Particulate Matter Sensor On Diesel Engine

With the fast development of the technology,diesel engine is popular in so many fields,such as engineering machinery,agricultural machinery and transportation.However,there is a large amount of particulate matter emission in the working process of the diesel engine,which is caused by the incomplete combustion of diesel.The diesel particulate filter(DPF)is widely used to reduce the emission of particles.To test the performance of DPF and obtain the particle concentration,one particle sensor is installed downstream of DPF.In this paper,the working principle of new leakage current particulate matter sensor was studied through numerical simulation and experiment.The structure parameters of the sensor were optimized and the measurement accuracy was improved by comparing the dynamic characteristics of particles in different sensors.Firstly,the geometrical model and grid model of the particulate matter sensor were established in the Comsol Multiphysics software.The initial conditions and boundary conditions were determined by diesel engine bench test and calculation.In this paper,the ?-? turbulent flow model,the particle tracing for fluid flow model and the static electrostatic model were selected to establish the three-dimensional calculation of the particulate matter sensor by Comsol Multiphysics software.The simulation results were compared with the experimental date to verify the accuracy of the simulation model.The simulation showed that the gradient of the velocity distribution was sharp at the inlet of the particle sensor,and larger the electrode spacing of the sensor was,more obvious the gradient of the velocity distribution was.It was obvious that the velocity of the exhaust inside the sensor was lower than that in the exhaust pipe.The exhaust velocity was lower with a larger electrode spacing or a longer electrode length.The velocity field distribution,electric field distribution and the motion condition of the particulate matter in the sensor were simulated based on the simulation model.The direction of the electric field was from the high voltage electrode to the ground field along the radial direction,and the strength magnitude ofthe electric field reduced along the direction of electric field.The velocity of negatively charged particle was larger than that of positively charged particle,while that of neutral particle fell in between.The motion trend of charged particles to two electrodes was more obvious with narrower electrode spacing or larger electrode voltage.Secondly,the test bench was set up to study the variety of signal output of the sensor with the electrode space and electrode length,based on the signal variable method.In the process of experiment,the electrode was applied with 1kV voltage and the load of the engine was varying while the rotating speed is fixed.It was found that the signal voltage of the particle sensor increased with the increasing load of diesel engine.While the engine condition was fixed,the signal voltage increased with the increasing electrode length,however,reduced with the increasing electrode spacing.Finally,the effects of electrode space,electrode length and engine load on the performance of the sensor were analyzed by combining the simulation and experiment results.It was concluded that the performance of particulate matter sensor was optimal while the electrode space was 1.25 mm and electrode length was 12.5 mm with the electrode voltage ranging from 1000 V to 1500 V.