Читать книгу Agitator Design for Gas-Liquid Fermenters and Bioreactors - Gregory T. Benz - Страница 80

Impellers operating in turbulent flow have variable loads created on each blade, and a variable net side load, which is transmitted to the shaft and creates a bending moment. This was described in Chapter 3, under the heading of Dimensionless Force. In general, fermenters have very high agitation intensity, raising the value of the Dimensionless Force, even when ungassed.

When gas is introduced, the forces for radial impellers typically double. For axial impellers in up‐pumping mode, the forces can more than double. In down‐pumping mode, or when liquid level passes through an impeller, the loads can be triple; sometimes even more. We will discuss these issues in more detail in Chapters 5 and 17.