Jet Penetration

The jets formed by distributors are originating from tubes inserted at various angles within the bed walls. This flow of the jet and its penetration length are studied because of:

  1. The high jet velocity in the orifice, up to 180 m/s, in experiments, but with a velocity of 30-40 m/s in commercial distributors entrain solids, which provides a great energetic action of the jet of sand and a rapid erosion from any surface;
  2. The attrition of friable solids in beds occurring primarily in the jets. In addition, knowledge of the action of the jets will help in controlling the distribution of solids in the bed;
  3. The rapid changes in chemical and physical level, for example: combustion, gasification, flame reaction, granulation, coating, devolatilization.

Jet penetration lengths:

To an orifice in a flat plate, the length of the jet penetration Lj is defined by Filla et al. (1983) as the distance between the plate and the center of bubble to the instant at which the release of the jet occurs (Figure 3).

Figure 3 - Jet penetration lengths

For tubes pointed up (tuyere) in fluidized beds, Hirsan et al. (1981) noted that the length of the jet fluctuated greatly, which led the authors to define the lengths of the jets, minimum (Lmin) and maximum LB), and Lj as a further penetration of bubbles jet. For a simple hole, Yates et al. (1984) proposed the following correlation to calculate the length of the jet depending on the diameter of the orifice:

It is concluded that, to predict the jet penetration length for a particular application, choose the correlation for conditions that are closer to your system and apply it with caution.