# Research Developments of Aerostatic Thrust Bearings: A Review
## 3 Advances in Static Performance
### The Discharge Coefficient
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Year** & **Focus** & **Evaluation** & **Methodology** & **Bearing Type** & **Restrictor** & **Major Conclusions** \\
**Author** & **Parameters** & **Crideria** & & & & **Type** & **Experimentally** \\
2018 & \
\begin{tabular}{c} Office diameter \\ and position, \\ supply pressure \\ \end{tabular} & Load capacity, air consumption & Experiments and numerical model & Rectangular pad & Annular orifices &
\begin{tabular}{c} Experimentally \\ demonstrated the numerical \\ model; investigated the \\ performance of rectangular \\ aerostatic pads \\ \end{tabular} \\ \hline
2018 & \
\begin{tabular}{c} Restrictor type, \\ film thickness, \\ orifice diameter, \\ and material \\ parameters \\ \end{tabular} & Load capacity, stiffness & Experiments and CFD simulation & Circular pad & Office, porous, multiple restrictor &
\begin{tabular}{c} The stiffness and stability of \\ thrust pad aerostatic \\ bearings are significantly \\ influenced by the geometric \\ and material parameters \\ \end{tabular} \\ \hline
2018 & \begin{tabular}{c} Parameter of \\ Ratio, Q. [1] \\ \end{tabular} & \begin{tabular}{c} Load capacity, \\ stiffness, mass \\ flow rate \\ \end{tabular} & \
\begin{tabular}{c} Experiments and \\ CFD simulation \\ \end{tabular} & Annular bearing &
\begin{tabular}{c} Proved the reliability of \\ proposed parametric \\ computational fluid \\ dynamics model and \\ genetic optimization \\ algorithm \\ \end{tabular} \\ \hline
2019 & \begin{tabular}{c} Structure, supply \\ pressure, film \\ thickness \\ \end{tabular} & \begin{tabular}{c} Load capacity, \\ stiffness, and \\ straightness \\ \end{tabular} & \begin{tabular}{c} Experiments and \\ FDM model \\ \end{tabular} & \
\begin{tabular}{c} Aerostatic \\ bearing \\ guideways \\ \end{tabular} &
\begin{tabular}{c} Office \\ restrictor \\ and four- orifice gas bearings \\ \end{tabular} \\ \hline
2019 & \begin{tabular}{c} Geometrical \\ parameters \\ \end{tabular} & \begin{tabular}{c} Load carrying \\ capacity, stiffness, \\ and mass flow \\ rate \\ \end{tabular} & \
\begin{tabular}{c} Experiments and \\ lumped \\ parameters model \\ \end{tabular} & Rectangular pads & Annular orifices &
\begin{tabular}{c} Analyzed the effect of \\ geometrical parameters on \\ the pad’s behavior \\ \end{tabular} \\ \hline
2019 & \begin{tabular}{c} Eccentricity ratio, \\ design \\ parameters \\ \end{tabular} & \begin{tabular}{c} Load capacity, \\ pressure \\ distribution, air \\ consumption, \\ stiffness \\ \end{tabular} & \
\begin{tabular}{c} FDM model and \\ CFD simulation \\ \end{tabular} & Double-pad & Annular arrives &
\begin{tabular}{c} Calculated the load-carrying \\ capacity (LCC) of bearing; \\ analyzed the relationship \\ between eccentricity ratio, \\ design parameters, and \\ static stiffness \\ \end{tabular} \\ \hline
2020 & \
\begin{tabular}{c} Supply hole \\ position, number, \\ and diameter, \\ supply pressure \\ \end{tabular} & Load capacity, air consumption & Genetic algorithm & Rectangular pad & Annular orifices &
\begin{tabular}{c} Presents an optimization \\ approach for multiple \\ orifice aerostatic pad \\ \end{tabular} \\ \hline \end{tabular}
\end{table} 
Table 1: Cont. orifice. The results showed that the major difference was the value of the critical pressure ratio between the conventional model and this model. For an orifice-type restrictor, the recommended value of the critical pressure ratio was between 0.35 and 0.4.