Abstract
KEYWORDS
Brake master cylinder, brake liquid flow, VSC, parametric model, CFD.
ABSTRACT
In the design of brake master cylinders, one important task is the calculation of the dimensions of the flow channels that provide a target mass flow from the brake liquid reservoir, needed for the correct performance of the VSC (Vehicle Stability Control) pump. The objective of this paper is to present a parametric simulation model that allows designers to easily modify and select the main dimensions and fluid properties in order to achieve the target flow rates in different pressure and temperature conditions. First, CFD simulations were run on different central valve master cylinder designs, in order to calculate the volume flow rates and the pressure drop distribution along the different parts of the system in a variety of conditions. The CFD calculations were validated with experimental flow measurements and then used to analyse the dependence flow vs. pressure and identify the critical flow regions. Then, using the equations of internal viscous incompressible flow, the flow resistance of the critical regions, the pressure drop through the different parts of the circuit and the total volume flow rates were calculated for some of the CFD simulated cases. The parameters for these analytical equations are the fluid properties and the main typical dimensions of the different parts of the cylinder. The analytical results were compared with the CFD results, in order to validate the results of the parametric equations. Finally, a parametric model was prepared, with the main dimensions and fluid properties as inputs and the pressure drops and flow rates as outputs. This parametric model constitutes a very helpful and easy-to-use design tool for quickly selecting the dimensions of the parts that yield the desired flow rates.