Energy Analysis of High-Dynamic Components: Model Development and Experimental Evaluation for Needle Roller Bearings and Wet Clutches (Energie analyse van hoogdynamische componenten: Modelopbouw en experimentele evaluatie voor naaldlagers en natte koppelingen)

In recent years, there has been a growing concern regarding the increasing prices and requirements of energy around the globe. One of the largest and cost effective ways to tackle this issue is by improving the energy efficiency of components/systems. This leads to a reduced total cost of ownership of machines, lower fossil fuel dependency and reduced greenhouse gas emissions.In this thesis two critical high-dynamic components, namely bearings and wet clutches are subjected to detailed energy analysis. Bearings are commonly used component in machines/systems, whereas the wet clutches find application in most of the transmission devices. In addition, these components are considered as significant contributors to the overall energy losses in machines/systems. In view of the critical nature of these two components with regard to energy losses, research is still ongoing to understand the loss mechanisms and to improve the energy efficiency of these components.The needle roller bearing lubricated with a solid-grease is popularly used in applications where there is a demand for high load-carrying capacity, low space requirements and where access to bearings are difficult for maintenance purpose. Nevertheless an appropriate model for calculating the energy losses in needle roller bearings lubricated with solid-grease does not exist. In case of the wet clutch, the mechanisms causing energy losses differ according to the state (engaged or disengaged) of the clutch. When a wet clutch undergoes engagement, the frictional effect (asperity contact torque) is mostly dominant and governs the energy losses. On the other hand, when the wet clutch is in disengaged condition, the viscous effect responsible for producing drag torque is considered as energy loss. The energetic behavior of wet clutches can be examined through modeling and dedicated experiments. For modeling wet clutch engagement cycles, the required characteristics/parameters of the friction model for capturing the dynamic friction phenomena along with the realization of variation in normal force as well as ATF (automatic transmission fluid) temperature observed in wet clutches are unknown. On the other hand, the existing models as well as the experimental data related to drag torque in disengaged wet clutches do not consider the real operating conditions such as variable ATF flow rate and rotational states of the disks for the higher clutch speed range.To overcome these short-comings, this thesis aims to study the energy losses in these two critical components through model development and experimental characterization. This work is helpful in building energy efficient machines/systems.The first contribution redefines the parameters of the Palmgren and SKF® models for predicting power losses in needle roller bearings lubricated with solid-grease. The updated models are applicable for both constant and varying speed profiles under constant loading conditions. In addition, a generic methodology has been proposed in order to verify and update the state-of-the-art models for predicting the power losses of any bearing type with any lubrication condition.The second contribution proposes an extended Reset-Integrator friction model for investigating the energetic (power and energy flow) behavior of wet clutches. The adaptation includes the experimentally determined stribeck function, viscous effect and the delay in actuation pressure signal. The friction torque generated by the extended model is dependent on the relative velocity, normal load and the ATF temperature. The model is validated with experimental results in both the time and the frequency domain. The developed model can also be used to study wet clutch vibration characteristics. By further analyzing the sets of experimental results, it is confirmed that the amplitude of shudder vibration is independent of the amplitude of applied contact pressure fluctuation. The third contribution through experiments and modeling provides a global view on the performance and energetic behavior of wet clutches with degradation and different initial driving energy levels. For this purpose, experiments are performed using an advanced SAE#2 test setup designed and built by our industrial collaborator, Dana Spicer Off Highway, Belgium. The simulation model incorporates an existing adapted form of the GMS friction model (for studying effects of degradation) and the developed extended Reset-Integrator friction model (for studying effects of initial driving energy levels). On the basis of the obtained results, some important conclusions are drawn regarding the design aspects of wet clutches such as COF (coefficient of friction), engagement duration, engagement torque, power and energy.Experimental characterization of drag torque in disengaged wet clutches is carried out, constituting a fourth contribution. For this purpose, experiments are performed using an advanced SAE#2 test setup designed and built by our industrial collaborator, Dana Spicer Off Highway, Belgium considering real operating conditions of wet clutches. By analyzing the obtained experimental results, the relationship between the amount by which the parameters such as ATF flow rate, ATF temperature, disk size and disks rotational states are varied and the corresponding change in the drag torque is established. In addition, a general description of the qualitative behavior of the drag torque in function of clutch speed is proposed and the associated physical phenomena are explained.A mathematical model based on continuity and Navier-Stokes equations, considering laminar flow in the gap between the disks, is developed as the fifth contribution to estimate the drag torque in disengaged wet clutches. The model validation results suggest that the model is capable of predicting the drag torque under real clutch conditions of variable flow rate and disks rotation states for the higher clutch speedrange.

Jaar van publicatie:2014

Toegankelijkheid:Closed