New solutions for gearing optimization through lubrication and cooling performance

Different types of lubrications are utilized in transmission systems to lubricate tribological contacts in order to minimize churning loss and dissipate frictional heat. This project concerns optimization of jet and splash lubrications in truck transmission system to rise efficiency and lubricant in meshing areas using particle-based computational fluid dynamics (CFD). Because of insufficient oil impingement in meshing gears, besides oil immersion additional railways on top gears, inside input and shifting shafts are provided which in some cases can act as jets. This novelty can meet expectation to deliver acceptable amounts of lubricants to critical places in transmission system. In order to study lubrication system elaborately, shafts are analyzed separately and modifications to existing designs for casing, spline, radial channel and jet angle are carried out to ameliorate cooling process with respect to high efficiency. For increasing numerical simulation accuracy and speed, Moving Particle Semi-Implicit (MPS) method, has been taken into account. The advantage of particle-based approach is the ability to simulate lubrication process by omitting mesh generation leading to higher accuracy and minimizing time required. Using this method, exact oil velocity, number of density and pressure are achieved giving the opportunity to determine wet area with high precision. With respect to the MPS method, heat transfer between oil and different components are achieved and their temperatures can be measured. The bearings are of the most vulnerable parts of transmission systems and their failure accounts for a major part of danger. Therefore, with considering all moments generated in ball bearing, internal heat generation is calculated and thermal stress of the ball bearing in input shaft experiencing high load and temperature is analyzed. The churning losses are calculated and compared for every shafts according to the oil viscosity and rotational speeds. Lubrication, heat dissipation as well as churning loss play vital role in functionality of gearbox and therefore well-designed lubrication would rise longevity avoiding failures, hence investigating alternate lubrication system can be conducted considering this thesis results.