Comparison Of Different Gas Models To Calculate The Spring Force Of a Hydropneumatic Suspension.

Simulation models are widely used to determine the performance and feasibility of a system before it goes into production, and in many cases the use of computer models can reduce the production cost and duration of a project significantly.  When developing a model some compromise must always be made between computational efficiency and the accuracy of the model.  This study compares the performance of three ideal gas (IG) law variations (IG with the energy equation (EE), Isothermal and Adiabatic), and two real gas approaches (Benedict Webb Rubin (BWR) equation with and without the EE).  These models are compared to experimental data, and both the BWR and IG models with the EE offers a significant improvement in correlation compared to the models without the EE.  The real gas approach offers a small improvement over the IG approach.  The best (BWR with EE) and worst (IG Isothermal) models are then used to model the suspension forces in a full vehicle model.  The data is again compared to experimental results and the difference in correlation for the two models is relatively small.  Due to the complexity and computational expense of including the EE, it is only recommended for cases where the accuracy of the suspension displacement is crucial.  Similarly the real gas approach is also recommended only where the accuracy of the suspension displacement is of great importance.