3. Results and discussion

3.1. Flow patterns of the blade unit

The flow pattern and transformation of that under two types of liquid arrangement methods of the blade unit are discussed in this section. To compare the results with similar research, the gas and liquid quantities are characterized by the gas-phase kinetic energy factor (F s) and the liquid-phase spray density (L W). The liquid film is evenly distributed on the surface of the sieve plate unit under the overflow distribution; therefore, the liquid spray density is the same as that under the spray distribution. The kinetic energy factor of the gas phase and the spray density are calculated as follows:
(1)
(2)
Here, u g represents the apparent velocity;L is the volume of the liquid phase; A is the area of the cross-section of the fluid, which equals πr2/4. According to the experimental setup of Tang [25], the range of the operating conditions is determined: gas-phase kinetic energy factor:F s: 0.4–4 (m/s*(kg/m3)0.5), gradient: 0.4 (m/s*(kg/m3)0.5); liquid spray density: L W: 26–260 m3/(m2*h).

3.1.1. Flow patterns in overflow distribution

The liquid phase is dyed with rhodamine B solution to observe the flow patterns. Canon EOS 70D is used to take photos of the flow pattern. The exposure time is 1/4000 s, and the ISO is 3200. An LED spotlight (5MT-100W) is applied as a camera light source. Under the overflow distribution, the flow patterns of the blade unit can be defined as three types based on the characteristics of the rotational and perforated flow of the gas-liquid two-phase flow system. They are bilateral film flow (BFF), continuous perforated flow (CPF), and dispersed-mixing flow (DMF) under the spray distribution, and film and jet flow (FJF) and jet and mixed flow (JMF) under spray distribution.
3.1.1.1. BFF