Development Of A Diesel Particulate Partial-Flow&Dynamic Dilution Sampling System

To carry out the study of diesel exhaust particulate, we should first needa particulate dilution sampling system complying with the internationalemission testing regulations. Currently there are two internationally popularcategories of dilution sampling system, one for full-flow dilution samplingsystem and the other for partial-flow dilution sampling system, which has beenwidely used in the particle detection and study because of its smaller sizeand lower cost compared with the full-flow dilution sampling system. Now ourcountry hasn’t launched such products, so we mainly purchased from abroaddirectly, but it is difficult to meet the domestic demand just by introduction.Our research group decided to develop a set of diesel particulate partial-flow&dynamic dilution sampling system, according to our own development needs.If technically feasible, it may also be the choice of numerous domesticenterprises, universities, research institutes and others. The entire systemhas the potential of high control precision, low testing and maintenance coststhough without mass flow-meter and exhaust concentration analyzer.Firstly, this paper established the research program of the partial-flow&dynamic dilution sampling system, elaborated how it works and the functionsof various components and connection relations, and deduced the conversionformula of specific particulate emission based on the system. According to thetechnical requirements of GB17691-2005for dynamic system, I selected the modelof required devices and complete the structural design and installation ofvarious features.Secondly，in order to simplify the experimental operation, to improve theefficiency of the experiment, and to real-time monitor the working status ofthe system, this dilution sampling system used upper and lower computerseparated design. PC control software was independently developed with VisualBasic6.0, it is divided into six main regions: serial port configuration,single filter test, multi filter test, system diagram, system status display and set differential pressure target value, status bar. Besides, control systemhardware circuit design has been completed, and the used sensors and actuatorswere online calibrated and debugged, which laid the foundation for the nextaccurate measurement of the sensor and proportional valve opening signal. Inthis paper, I has also formulated the control strategy of the system, andcompleted the C Programming Language of lower machine, which constituted thesoftware infrastructure of the whole control system together with the PC controlinterface. In addition, the study made use of the RS232serial communicationprotocol and the costumed data formats to achieve two-way data transmissionbetween the upper and lower computer.Finally, we conducted the on-site commissioning of the system, the openingand closing of the two solenoid valve of both sampling path and bypass passageare determined entirely by the sampling and bypass time of the upper computerprogram interface, which respond timely and promptly. Each sensor and controlprogram was running normally, PWM Channel Duty Register value monitored by datawindow1in the CodeWarrior debugger interface and the actual proportional valveinput voltage measured with a multimeter can adjust in accordance with the PIDalgorithm. But in the process of debug, proportional valve Ⅰ, Ⅱ showeddifferent degrees of failure, which caused that the commissioning work can notproceed, to be able to continue debugging tasks and evaluation experiments whenall problems are resolved, the fifth chapter briefly introduced the testprograms, apparatus and equipment used when I utilized the system for the dieselexhaust particulate measurement.