LAUSR

Abstract Electrical capacitance tomography with airflow injection system (ECT-AIS) has been developed for controlling particle distribution in pneumatic conveyance in order to maintain homogeneous downstream particle distribution e n do t + τ with a delay time τ even under inhomogeneous upstream particle distribution e n up t . ECT-AIS is composed of two ECT sensors for monitoring e n up t and for evaluating e n do t + τ after injecting airflow. The airflow is injected to the conveyance pipe by activating a solenoid valve of airflow injection system (AIS) to control the homogeneous e n do t + τ in the case that the spatial standard deviation of permittivity distribution at the upstream ECT sensor e SD up t which is calculated from e n up t and the spatial mean permittivity 〈 e n up 〉 t is greater than the threshold value δ. With this developed ECT-AIS, three different experiments are performed under different particle loading ratios (ϕ = 0.25, 0.50 and 0.75) with air flow rate Qa = 0.75 kg/s, 0.50 kg/s and 0.25 kg/s. As e n up t is homogeneous, e n do t + τ is also homogeneous. While e n up t was inhomogeneous, e n do t + τ was homogeneously distributed due to airflow injection. To evaluate the homogeneity of e n do t + τ , the spatial mean permittivity 〈 e n up 〉 t in upstream sensor is compared with 〈 e n do 〉 t + τ in downstream sensor and the two results were evaluated with the measured pressures p n up t and p n do t . As a results, e SD do t + τ is less than or equal to δ so that 〈 e n do 〉 t + τ is homogeneous after airflow injection. Based on Darcy–Weisbach equation, as the particles are homogeneous, the pressure is lower than that in inhomogeneous distribution. According to the relationship between mean permittivity and pressure, e n do t + τ is successfully controlled in homogeneous conditions by ECT-AIS.