> Woolf led himself astray with an entirely unsound theoretical model for the inner workings of his engine: he believed that steam at twenty pounds per square inch (psi) would expand to twenty times its volume before equaling the pressure of the atmosphere, steam at thirty psi would expand thirty times, and so on ad infinitum.

This seems to to exaggerate the incorrectness of Woolfs model. Assuming that the temperature is held constant (which apparently was stipulated in Woolf's patent) this is true according to the ideal gas law.

It is not clear where Woolf's model breaks down, but this part seems reasonable.

It is possible that the temperature was not held constant in his device, and, working off of the caloric theory of heat, assumed that the issue was leakage of either the original steam gas or of the caloric. In a sense, losing heat (caloric) would be to Woolf's model the same thing as having a leak.