Study On The Mechanism Of Ultrafine Particle Acoustic Agglomeration And Its Explore On CI Engine

Compression ignition engine, with its high thermal efficiency andbetter fuel economy, gradually has been widely used in various types of cars,but its more particle emissions, especially the particles with smaller size,make it difficult to meet the requirements of increasingly stringent emissionregulations.Acoustic agglomeration technology, as a pre-treatment for eliminatingparticle emissions, it has been studied in the past nearly one hundred years.But most of the researches are still in the stage of theoretical exploring, stillexisting a big gap from the actual industrial application. There is hardly anyrelevant research used in compression ignition engin, especially the acousticagglomeration using ultrasound. In order to meet the increasingly stringentemission regulations, the experimental research on ultrafine particle acousticagglomeration of compression ignition engine was explored. In this experimental study, ultrasound was chosen as a sound source.And the sound waves acted on the aerosol with a lot of ultrafine particles onthe small-scaled experimental bench. SMPS (Scanning Mobility ParticleSizer) was used to measure the particle number. By this experimental study,we got more experience for practical application.The impact of some parameters such as the acoustic intensity, the timeof acoustic agglomeration and initial particle number concentration on theefficiency of acoustic agglomeration were studied. From which we knewthat:(1) In the working condition with high acoustic intensity, acousticagglomeration had an excellent effect, could effectively reduce the ultrafineparticle number concentration, effectively reduced more than70%of theparticles with the bigger PM (peak size is184.3nm) and35%of the particleswith the smaller PM (peak size is26.4nm). And with the increase of acousticintensity, the efficiency of acoustic agglomeration improved.(2) As the timeof acoustic agglomeration increased, the efficiency of acousticagglomeration could be well improved. For example, when the time ofacoustic agglomeration increased from9s to18s, to the bigger particles size(peak size is184.3nm), the efficiency of acoustic agglomeration increasedfrom57.9%to91.4%, to the smaller particles size (peak size is26.4nm), theefficiency of acoustic agglomeration increased from26.7%to56.1%.(3) Initial particle number concentration had some impact on the efficiency ofthe acoustic agglomeration. The bigger initial particle number concentration,the higher efficiency of acoustic agglomeration would be got.(4) Theacoustic agglomeration was verified on the diesel engine test bench. As theacoustic intensity changing from152.6dB to158.6dB, the efficiency of theacoustic agglomeration was improved from11.6%to37.8%. As the durationof acoustic agglomeration increased, the efficiency of acousticagglomeration was well improved. When the time of acoustic agglomerationincreased from9s to27s, the efficiency of acoustic agglomeration increasedfrom29.4%to50.3%.