Methods and Devices for Measuring the Waveform of Large Friction Forces and Energy between the Bodies and Needles of Injector Nozzles of Marine Piston Combustion Engines

<div>In marine combustion engines, it is important to minimize fuel consumption and reduce toxic emissions. One method to achieve this is minimizing friction losses in the injection subsystem, which is why measuring them is necessary.</div> <div>Some friction force values in precision pairs are so high that they require specialized methods and measurement stations. This article presents innovative methods and devices for measuring high friction and high power forces between the body and the needle of injector nozzles in the presence of a lubricant. The scientific method consists of increasing the load applied to the needle pin located in the nozzle body until it is completely ejected from the body. The devices that determine the course and maximum value of the friction force utilize test benches for dynamic tensile strength testing samples, employing specially designed and manufactured holders.</div> <div>When the fastening of the pin holder proved insufficient due to slippage, a semicircular groove was made around the circumferential needle pin. Round balls were inserted into the pin’s innovative mounting screw holes, recessed into the circumferential groove by about half their diameter, which is an important contribution by the authors. The maximum friction force was determined from the recorded signal, depending on the displacement or time waveform.</div> <div>The friction force depends on the needle’s position relative to the nozzle body; therefore, it is recommended to take measurements in at least four planes and compute the average. Different friction force values are caused by errors in the roundness and concentricity of the injector nozzle body guide part relative to the needle, as well as deposit formation.</div> <div>This article presents the influence of the state of the friction surfaces, as determined by modern geometric measurements of the cooperating elements, including computed tomography scans and silicone casts, on the maximum friction force value and modeling.</div>