Experimental Study On Atmospheric Pressure Surface Dielectric Barrier Discharge Plasma Actuator For Airflow Control

The Atmospheric pressure discharge plasma airflow control,as a kind of novel active airflow control technology,has shown a wide application prospects in promoting the aerodynamic performance of the aircrafts.In recent years,surface dielectric barrier discharge(SDBD)has become a popular research topic in airflow control field due to some specific features of its plasma actuator,such as simple structure with no moving parts,easier application without changing the existing aerodynamic structure,low power consumption and rapid response.It is an important research direction to improving the Electro-hydro-dynamic(EHD)effect generated by SDBD plasma actuator for better airflow control applications.In order to enable the actuator to be effectively applied in the practical engineering field,it is of great significance to promote the dynamic performance of the actuator by changing the control parameters,optimizing the actuator structure,changing the driven power supply and further exploring the underlying physical mechanism.Experimental studies on the SDBD plasma actuator performance optimization are carried out,with a purpose to improve the EHD effect induced by SDBD plasma actuator and explore the physical mechanism behind the experimental phenomena.The equipments and measurement devices used in the experimental studies are firstly introduced,and then the studies on parameters optimization of SDBD plasma actuator driven by single-AC high voltage and plasma actuator performance driven by dual high voltage—"AC high voltage superimposed with a pulse bias voltage" are carried out.In the single-AC driven case,the influences of the AC peak-peak voltage and encapsulated electrode width on the actuator-induced airflow velocity and thrust force are mainly studied,and the effects of the dielectric plate material,dielectric plate thickness and electrode gap on the actuator-induced thrust force are briefly investigated.In the dual high voltage driven case,the performance of the plasma actuator driven by "AC high voltage superimposed with a positive or negative pulse bias" is firstly studied,and then the studies on the plasma actuator performance driven by "AC high voltage superimposed with a synchronous positive pulse bias" are further carried out.The main contents are as follows:1.The effects of AC peak-peak voltage on the actuator-induced airflow velocity and thrust force are investigated.The voltage and current waveforms,the dielectric plate surface potential distribution,the discharge images and Schileren images are measured to explore the underlying physical mechanism.The experimental results show that the airflow velocity and thrust force increase with the AC peak-peak voltage.The reason is that increasing the AC peak-peak voltage can strengthen the external electric field and increase the surface charge accumulation,which will further benefit more oxygen negative ions migrating downstream the dielectric surface and eventually induce higher airflow velocity and thrust force.2.The encapsulated electrode width of the SDBD plasma actuator is changed to study the airflow acceleration behavior.The discharge plasma extension pictures,dielectric surface potential distribution,actuator-induced airflow characteristics(time-averaged ionic wind velocity,thrust force and Schlieren images)are investigated experimentally.The results show that the encapsulated electrode width can significantly affect the distribution of the surface potential,and the spatial electric field formed by the surface charge accumulation can significantly affect the applied electric field.As a result,the maximum airflow velocity and thrust force increase with the encapsulated electrode width.3.Experimental studies on the SDBD plasma actuator performance driven by dual high voltage—"AC high voltage superimposed with a positive or negative pulse bias" are carried out.The effects of pulse voltage,pulse repetition frequency(PRF)and pulse width on the actuator-induced airflow velocity and thrust force are investigated.The experimental results show that,compared with the single-AC driven case,the "AC high voltage superimposed with a positive pulse bias voltage"(ACPP)driven mode can significantly improve the actuator-induced airflow velocity and thrust force,while the actuator performance is little changed when the actuator is driven by "AC high voltage superimposed with a negative pulse bias voltage"(ACNP).The electrical and optical properties of the AC discharge are measured to explore the underlying airflow acceleration mechanism,with and without applying a pulse bias voltage signal.The measured results reveal that the applied positive pulse bias voltage can increase the glow-like discharge and applied negative pulse bias voltage can increase the filamentary discharge in the following AC discharge cycle.Glow-like discharge contributes most to the generation of airflow and thrust force while filamentary discharge contributes little to airflow and thrust force generation,this might be the main reason that the performance of actuator driven by ACPP is better than that by ACNP.Moreover,the Schlieren images further indicate that the applied pulse bias voltage exerts its effects on the SDBD actuator performance by affecting the AC discharge.4.The performance of the SDBD plasma actuator driven by "AC high voltage superimposed with a synchronous positive pulse bias voltage" is further studied.The positive pulse bias voltage signal is chosen to superimpose on the AC trough phase,at which the thrust force enhancement is most significant.The thrust force and power consumption changing with AC voltage and pulse voltage are measured,and the thrust force efficiency is calculated.The physical mechanism behind the thrust force changes is analyzed by measuring the electrical characteristics,optical properties and surface potential distribution.The experimental results show that the actuator performance can be increased significantly after superimposing the positive pulse bias voltage,the maximum thrust force can be promoted four times and the thrust efficiency can be doubled.Moreover,when the filamentary discharge occurs in the glow-like discharge region,the thrust force will still slightly increase with the pulse voltage.The phenomena can be mainly attributed to the charge accumulation effects of the positive pulse discharge.The surface potential measurement results reveal that the spatial electric field formed by the surface charge accumulation after positive pulse discharge can significantly affect the applied electric field,and the strengthened spatial electric field perhaps has an offset effect on the shielded external electric field.As a result,the thrust force can still slightly increase with the pulse voltage after filamentary discharge occurring.