Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering
Transport Technology

G.P.M. Hof Theory and Simulation of Fluid Couplings
Masters thesis, Report 2002.TT.5658, Transport Engineering and Logistics.

In the area of drive technology it often occurs that the form of power supplied by an energy source (motor) does not comply with the form of power required by the energy consumer (load). To overcome this problem, hydrodynamic couplings can be used to convert the energy supply into a usable form.

The main components of a hydrodynamic coupling, also called fluid coupling, are two bladed wheels, that is an outer wheel (pump wheel) and inner wheel (turbine wheel), and a shell. The pump wheel is connected to the motor. The torque transmitted by the drive motor is converted into kinetic energy of the operating fluid. In the turbine wheel, which is connected to the driven machine, this kinetic energy is converted back into mechanical energy. The transmitted coupling torque always equals the input torque.

To realize a higher relief of the drive motor during start up, a smoother start of the driven machine and a better efficiency of the drive system, the fluid coupling can be equipped with a delay-fill chamber and annular chamber. By using these auxiliary chambers, the amount of operating fluid that takes part in the torque transfer can be changed during operation.

Determination of the nominal operating point of a drive system (the nominal operating speed and nominal operating torque) is relatively simple. Also, the insight of the qualitative start up characteristics of the drive system can be estimated without much difficulty. However, it is quite complicated to determine the quantitative characteristics of the start up process and the dynamic behaviour of the whole drive system. To make a proper estimation of the start up performance of the drive system, it is almost insurmountable to do this without any aid of computer software.

Software, called T-Cycle, is available to determine the behaviour of a simple drive system for several operating characteristics. However, this software is not suitable for detailed calculations on the operating characteristics of a drive train. Therefore, a new software tool, called TurboSIM, has been developed and programmed. TurboSIM is capable of simulating the operating characteristics of a drive system, consisting of a motor, a hydrodynamic coupling, a reduction gear and a machine. These elements are connected to each other with shafts and flexible couplings. By using a dynamic model (with mass, damping and stiffness properties for all drive system components) the new software can be used to optimise the design of a drive system, already in the design stage, by means of parameter variation.

Verification of TurboSIM shows that qualitative operation of the new software is satisfying. The validation of the software is done by means of a comparison of simulation results with measured data of a test stand. This evaluation shows that there is a significant difference between the results of the simulation software and the results of the test stand. It is very likely that this deviation is the consequence of a simplification of the model of the fluid distribution at the coupling's start up.

Reports on Transport Engineering and Logistics (in Dutch)
Modified: 2004.06.20; , TU Delft / 3mE / TT / LT.