The Research On The Real Time Whole Field Particle Image Velocimetry And Sizer Technology

On the Diesel engines, the spray characteristics of the fuel injector have an important impact on combustion process. The droplets diameter affects the quality of air-fuel mixture, so it is very important to measure the droplets diameter distribution in a spray. On the study of the diesel spray characteristics, usually in the hope that the droplet size can be measured while obtaining the droplet velocity, it is of great significance on the micro fuel atomization mechanism. Based on the binocular vision and particle image gray difference method, a new system was developed, which can measure the particle size and flow field velocity simultaneously - PIVS (Particle Image Velocimertry & Sizer) system, and then the system was tested throught some experiments. The main working of this paper is summarized as follows.1. According to Mie scattering theory, based on the use of different laser intensity gray difference method of particle size measurement, a new method based on binocular vision and the particle image gray difference method was proposed, the measurement model has been established to derive the relationship between particle image gray and particle size. In this system, two digital cameras are used to capture images from different shooting angle, according to Mie scattering theory, at different scattering angle, laser scattering intensity is different, so two pictures with different particle gray scale can be captured by the two cameras. At last, the method has been tested by actual experiments, verified the validity and feasibility of the method.2. Proposed a new velocity measurement method based on binocular vision and autocorrelation. In the use of velocity autocorrelation measurement, one of the biggest problems is the "ambiguity" of the speed direction, by using two cameras, the problem can be eliminated. And in accordance with the method the software was programmed, the system has been tested by measuring the simulation data and experimental data.3. Based on the binocular vision, a new method was proposed to match the particle images. When using the particle image gray difference to measure the particle size distribution, the match of the images in two pictures of the same particle is the core issue of this method. As two digital cameras are used to capture images, one digital camera is set up at a shooting angle of 90 degrees, to capture double-exposure images; another digital camera is set up at a shooting angle of 60 degrees, to capture single exposure pictures. Exposure frequency and shooting angle are both different, so the matching of particle images is very hard. Under this condition, according to the requirements of imagery system, a new particle images matching method was proposed, and then this matching method was tested on the experiments.4. Developed the PIVS corresponding hardware and software system. PIVS system mainly consists of hardware system(including photography and imaging system) and software system(including processing and control system). Hardware system is a dual-camera, double-exposure photography system, and the required pictures can be successfully captured on this system; based on C++ digital image processing technology and database technology, image processing and control system has been developed, and the usage of the software system including image acquisition, storage, handling and process control, and eventually flow velocity vector information and the particle size distribution information can be measured by this system.5. The PIVS system was testified. The system has been tested by three steps: velocity measurement, particle size calculation and both in the same field. The reliable and effectiveness of the PIVS system was validated.