WEAR ANALYSIS OF BY PASS VALVES APPLIED ON REGULATED-TWO-STAGES TURBOCHARGER

The new emission legislations, demand, from vehicle manufactures, the development of technologies to improve fuel consumption and pollutants emission. Following this trend, the turbocharging systems innovate together and release new turbocharger architectures in the market. One of them is the regulated-two-stages Turbocharger, which delivers higher efficiency in a broader engine speed range. In this system, there are two turbochargers, the High and Low Pressure stages. The former has a bigger influence on the low engine speeds, and the latter in the higher engine speed. Between both stages there is a ByPass valve that allows the gas flow to reach the Low Pressure stage, when needed. In this paper, a wear analysis to understand the wear rate between shaft and bushing of the Bypass valve is presented. This study started in two fronts, the first one is on the wear measurements of high mileage components. Using a precise tridimensional equipment, shaft and bushing had their diameters measured along the whole length over 20.000 points. This data was the input to study the wear profile, depth and shape. As well as predict contact area and total wear volume. The second front is based on measurements of forces and displacements acting on the pair shaft-bushing. These measurements were performed on real vehicle running a representative application where wear was detected. The dynamic interaction between these forces and the shaft and bushing was essential to explain the wear behavior and understand the influence of each force component. All this experimental data was used as input to the wear equation, developed from wear theory and can be used to evaluate impact of new designs