**4.4 Further improve the anti**−**/de-icing performance of the DBD plasma-based approach with a duty-cycle modulation technique**

As described above, with the same power input, the DBD plasma-based approach was demonstrated to be more effective in preventing ice accretion over the airfoil surface, in comparison with the conventional electrical heating method. The anti−/de-icing performance of the DBD plasma-based approach can be further improved through optimization of the design paradigms of the plasma actuation in the terms of plasma actuation modes (i.e., AC-DBD vs. ns-DBD plasma actuation) [38], the layout design of the plasma actuator over the airfoil surface [36], the applied voltage and frequency, etc. [51]. As an example of the attempts to optimize the DBD plasma actuation for improved anti−/de-icing performance, a duty-cycled modulation concept was utilized by leveraging the unique feature of fast response time for the DBD plasma actuation (*i.e.*, on the order of 10 ~ 100 ms) in terms of momentum transfer [28] and thermal effects [47] induced by plasma discharges. **Figure 12** shows a schematic of the duty-cycle modulation from a continuous DBD plasma actuation to a duty-cycled DBD plasma actuation. Various frequencies of the duty-cycled DBD plasma actuation were examined to evaluate the effects of the duty cycle frequency on the thermal characteristics of the DBD plasma actuation [39].

**Figure 13** shows the comparison of the acquired ice accretion images and the corresponding IR thermal imaging results with the DBD plasma actuators being operated at different duty-cycled frequencies. The experimental study was conducted under the same icing test condition of the test conditions of *U*∞ = 40 m/s, *T*∞ = −5°C and *LWC* = 1.0 g/m3 . While the maximum instantaneous power inputs *An Experimental Investigation on the Thermodynamic Characteristics of DBD Plasma… DOI: http://dx.doi.org/10.5772/intechopen.100100*

### **Figure 12.**

*A schematic of the modulation from a continuous plasma actuation to a duty-cycled plasma actuation for improved anti*−*/de-icing performance.*

**Figure 13.** *Comparison of duty-cycled DBD plasma actuations modulated with different duty-cycle frequencies.*

supplied to the plasma actuator were different for the cases with different dutycycle modulation frequencies, the total power consumptions over a given period of time were kept at the same level for all the compared cases. It is clearly seen that, the cases with duty-cycled plasma actuations show much better anti−/de-icing performance (i.e., with the plasma region being completely free of ice), in comparison to that of the continuous plasma actuation (i.e., the baseline case shown at the most left side of **Figure 13**). As the duty cycle frequency increases, much less rivuletsshaped ice features were found to form over the airfoil surface. Since the surface temperatures for the cases with the duty cycled DBD plasma actuations are much higher than that of the baseline case with continuous plasma actuation, the increase in the duty cycle frequency was found to further enhance the thermal effects of the DBD plasma actuation, resulting in higher temperatures over the airfoil surface, as revealed quantitatively from the acquired IR thermal imaging results. The

enhanced thermal effects of the duty-cycled DBD plasma actuation at higher duty cycle frequencies was demonstrated to be able to further improve the anti−/de-icing performance of the DBD-plasma-based approach for aircraft icing mitigation.
