Chapter 2
Bubbling Properties in Pulsed Fluidised
Beds
This chapter discusses the response of flow patterns and bubbling properties in a
quasi-2D, pulsed, gas-solid bubbling fluidised bed to the variations in an oscillatory
gas flow. The experimental results demonstrate that bubbling behaviour can be modified via modulated periodic flows. Compared to steady flow fluidised beds, pulsed
beds possess the advantages to manipulate several bubble properties, such as size,
rising velocity and coexisting number in the domain, and, therefore, impose modifications to the system behaviour. For a certain range of oscillatory flows, structured
flows emerge and regulate the spatial arrangement of bubbles. As a result of structuring, the flow of bubbles becomes largely predictable and can be more precisely
controlled and tailored in both temporal and spatial dimensions, providing a new
class of fluidisation.
2.1 Introduction
For bubbling gas-solid fluidised beds, overall solid mixing and transport process
primarily rely on bubbling behaviour, which is complex and inherently unstable [3,
16]. Over the last decades, enormous efforts have been made in investigating how
to bring in extra flexibilities to control the system hydrodynamics and decouple
conflicting experimental parameters. In the category of means to modify gas-solid
interactions, pulsating the gas flow in fluidisation provides a non-invasive approach
to generate a more homogeneous gas-solid suspension, and, in particular, mitigate
attrition, erosion, and elutriation [15].
Pulsation can be realised either temporally or spatially. Without altering the flow
rate, one could relocate the gas stream entering beds via different sections of the
distributor plate periodically. For example, a stream can be pumped at a constant
velocity through a continuous rotating disc with certain opening areas, thereby
creating a spatially pulsed flow [10]. Control of the opened areas in a rotating
disc is able to effectively adjust the flow patterns [12]. Temporal pulsation is more
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
K. Wu, Dynamically Structured Flow in Pulsed Fluidised Beds, Springer Theses,
https://doi.org/10.1007/978-3-030-68752-6_2
35
Bubbling Properties in Pulsed Fluidised
Beds
This chapter discusses the response of flow patterns and bubbling properties in a
quasi-2D, pulsed, gas-solid bubbling fluidised bed to the variations in an oscillatory
gas flow. The experimental results demonstrate that bubbling behaviour can be modified via modulated periodic flows. Compared to steady flow fluidised beds, pulsed
beds possess the advantages to manipulate several bubble properties, such as size,
rising velocity and coexisting number in the domain, and, therefore, impose modifications to the system behaviour. For a certain range of oscillatory flows, structured
flows emerge and regulate the spatial arrangement of bubbles. As a result of structuring, the flow of bubbles becomes largely predictable and can be more precisely
controlled and tailored in both temporal and spatial dimensions, providing a new
class of fluidisation.
2.1 Introduction
For bubbling gas-solid fluidised beds, overall solid mixing and transport process
primarily rely on bubbling behaviour, which is complex and inherently unstable [3,
16]. Over the last decades, enormous efforts have been made in investigating how
to bring in extra flexibilities to control the system hydrodynamics and decouple
conflicting experimental parameters. In the category of means to modify gas-solid
interactions, pulsating the gas flow in fluidisation provides a non-invasive approach
to generate a more homogeneous gas-solid suspension, and, in particular, mitigate
attrition, erosion, and elutriation [15].
Pulsation can be realised either temporally or spatially. Without altering the flow
rate, one could relocate the gas stream entering beds via different sections of the
distributor plate periodically. For example, a stream can be pumped at a constant
velocity through a continuous rotating disc with certain opening areas, thereby
creating a spatially pulsed flow [10]. Control of the opened areas in a rotating
disc is able to effectively adjust the flow patterns [12]. Temporal pulsation is more
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
K. Wu, Dynamically Structured Flow in Pulsed Fluidised Beds, Springer Theses,
https://doi.org/10.1007/978-3-030-68752-6_2
35