2024-08-10 00:00:00 Ellipse Law: a easy tool to calculate pressures, mass flow and temperatures for off-design conditions in turbomachinery. Ellipse Law calculates Stodola‘s Cone Law (also known as "The Law of the Ellipse") for turbomachinery. At the beginning of the 20th century, Aurel Stodola (1859 – 1942) discovered the relationship between inlet pressure, outlet pressure and mass flow in steam turbines for various operating conditions.