The spray pattern of a fuel injector is a key factor in the mixing of the fuel with the air. One effective means of determining the fuel distribution in the spray is to collect the fuel in tubes, from various regions of the spray. The amount of fuel in the tubes is measured. These measurements are used to create diagrams and curves which graphically represent the fuel distribution within the spray. The term “Patternator” has come to mean a device which determines the spray distribution, in the sense that the device determines the pattern of the spray.
The objective of this paper is to describe the operation, features, and performance of an automated patternator designed and built at Michigan Technological University for Ford Motor Company. The patternator system was constructed for rapid determination of the spray pattern in order to expedite the development of automotive port fuel injectors.
In order to obtain satisfactory resolution of the spray distribution, a grid of 256 tubes in a 16 by 16 square pattern was selected. Each tube is about 20 cm long with an internal diameter of 0.584 cm. An empty tube rack is placed under the fuel injector in the filling station. The spray from the fuel injector is directed upon the square 16 x 16 array of test tubes held in its enclosure. Clearance between the tubes allows the spray to flow through the tube rack. An exhaust system removes the remaining spray and air mixture. Visual observation of various sprays indicated that the presence of the tube rack does not significantly change the spray pattern. The fuel injector is operated until the fluid level approaches the top of the fullest tube. The operator places the tube rack on the weighing station and starts the computer program. The computer controls the measuring station and automatically determines the weight of fluid in each tube. All weight data is saved on a hard disk for use in plotting or for export to a floppy disk. The operator can select various plots. The weighing station is also used to measure the empty tube rack, to determine the tare weight, prior to the spray test.