Experimental investigation of effects of nozzle seat wear and deformation on diesel injector function

Common rail piezo injectors are an advanced fuel injection system used in today's diesel engine applications and are constantly being developed to meet decreasing emission regulations. Particularly, some parameters such as injection pressure, bringing the fuel into the combustion chamber at the right time, in the right quality and in the right position are becoming increasingly important. At this point, a new injector design emerges in Bosch for use in new engines. One of the most critical points of the new design is the changes that occur in both nozzle needle and body seat area with the operation of the engine. In order to ensure that the amounts of fuel injected and thus the emissions emitted are consistent throughout the life of the engine, it is necessary to reduce these changes as much as possible. In this thesis, the progression of the changes that occur in nozzle seat area and the optimized process developed as a solution are investigated experimentally using the engine tests with combustion. The experiment consists of two engine tests with 400 hours duration. At 0, 20, 200 and 400 hours, the nozzle analyzes by taking the surface profiles of the needle and body seat area and injector function measurements were performed. According to the test results, the injection quantity of un- optimized nozzles increases starting from 20 hours due to the change of nozzle body seat surface, while the injection quantity of optimized nozzles decreases starting from 20 hours due to wear on the needle although there is no change in the nozzle body seat surface. With the increase in the injection quantity, two injections close to each other can be combined and this creates a risk for the injection pattern. Therefore, it has been found that optimization is more advantageous and it was decided to continue with the alternative having optimized process.