Transparent Housing Design & Water Based Lubrication For Future Marine Drives

Sammanfattning

This thesis addresses lubrication challenges in marine transmissions through two complementary studies aimed at improving system transparency and evaluating sustainable lubrication alternatives. The primary objectives were to enable real-time visualization of oil flow in the IPS 10 transmission and to assess the viability of a water-based lubricant in the DPH driveline under realistic operating conditions. For the IPS 10 system, a transparent housing was designed using Accura ClearVue material to enable oil flow observation during operation. Four structural components were redesigned: the upper gear cover, upper gear housing, intermediate housing, and lower gear housing. These redesigns focused on removing non-essential features to improve visibility while preserving all functional interfaces, such as sealing surfaces, alignment features, and mounting points. Three mounting flange concepts were developed and evaluated using Finite Element Method (FEM) analysis: Half Circle, Simple Design, and Generative Design Extension (GDX). All concepts demonstrated structural integrity, with maximum stress values remaining below the allowable limit of 23 MPa, calculated with a safety factor of 2. The GDX concept exhibited the highest displacement value at 0.64 mm (compared to 0.31 mm for the Half Circle concept) but offered significant advantages in weight reduction and manufacturing cost due to its optimization for additive manufacturing. The final designs are complete and ready for selection and implementation based on Volvo Penta’s preferences. The second part of the thesis involved a lubricant comparison between a conventional synthetic oil (Mobil 75W140) and a water-based alternative (Transmission 150), developed in collaboration with Sustainalube. The test was conducted on a dedicated rig replicating realistic load and speed conditions. Prior to testing, the system was flushed with a cleaning fluid, and the water-based lubricant was subjected to a sequence of cycles at increasing speeds and torque levels. The lubricant performed satisfactorily at low to moderate loads, up to 30% of maximum torque. However, during the fifth cycle at 80% load (equivalent to 674 Nm), the test was terminated due to mechanical noise. Post-test inspection revealed metal-to-metal contact and visible gear wear, indicating failure of the lubricant film under high stress. Contributing factors included the water-based lubricant's lower pressure-viscosity coefficient (measured at <5 GPa⁻¹ compared to ~20 GPa⁻¹ for the synthetic oil), residual contamination from previous oils, and foaming issues resulting in air entrapment and seal leakage. This work contributes to a better understanding of lubrication mechanisms in marine transmissions and highlights the current limitations of water-based lubricants under high-load conditions. In parallel, a transparent gearbox housing was developed, offering a practical platform for future flow visualization and experimental research. Recommended future work includes improved surface cleaning protocols, further evaluation of influencing factors on water-based lubricant performance under high load, and consideration of their suitability for lower-load marine driveline applications as a step toward sustainable solutions.