Results
This study was able to successfully demonstrate through the use of analytical calculations that Knudsen pumps can be used in the operation of boundary layer suction. Boundary-layer calculations showed that, for a flat plate, the addition of suction can reduce the drag coefficient over the laminar part of the wing by 23%. Although the laminar part of the wing was only approximately 1.2% of the wings’ average chord length without suction, the improvement is still considered to be significant when considering the scale of the Airbus A380’s operations. In order to achieve this improvement in drag coefficient, a suction velocity of 0.2m/s was required. It should be noted that this is only relative to one suction hole; in practice many suction holes will be implement. For the given suction conditions, a required pressure difference of 3kPa was calculated.
It was determined that a conventional pump would require 187W power input in order to provide the required suction pressure, however due to the nature of Knudsen pumps, this power input is not required and can therefore be used as an estimation of the potential power savings that can be gained if Knudsen pumps use instead of conventional pumps. By analysing how the net pressure difference varied with the design parameters of the Knudsen pump, an effective solution could be determined which met the required suction pressure. Theoretically Knudsen pumps can be connected in series to increase the pressure difference. In this study, a 6-stage configuration was observed to provide a net pressure difference of 3.34kPa.
From a theoretical point of view, the study was particularly successful in demonstrating that a Knudsen pump can be effectively used in the operation of boundary layer suction. The results are encouraging in the sense of potential benefits and it leaves many additional possibilities for further improvement and research. A key point which is not elaborated in this study is how the temperature input into the Knudsen pump can be created. The aircraft de-icing or air conditioning systems are possible solutions to this problem which can be further researched. This study simply focused on the two dimensional flat plate theories for the boundary layer suction. A more accurate representation of the benefits could be achieved through the incorporation of a three-dimensional aerofoil.
A more detailed analysis of our results can be found in our technical report, along with the Knudsen Pump and Boundary Layer models, linked below.
It was determined that a conventional pump would require 187W power input in order to provide the required suction pressure, however due to the nature of Knudsen pumps, this power input is not required and can therefore be used as an estimation of the potential power savings that can be gained if Knudsen pumps use instead of conventional pumps. By analysing how the net pressure difference varied with the design parameters of the Knudsen pump, an effective solution could be determined which met the required suction pressure. Theoretically Knudsen pumps can be connected in series to increase the pressure difference. In this study, a 6-stage configuration was observed to provide a net pressure difference of 3.34kPa.
From a theoretical point of view, the study was particularly successful in demonstrating that a Knudsen pump can be effectively used in the operation of boundary layer suction. The results are encouraging in the sense of potential benefits and it leaves many additional possibilities for further improvement and research. A key point which is not elaborated in this study is how the temperature input into the Knudsen pump can be created. The aircraft de-icing or air conditioning systems are possible solutions to this problem which can be further researched. This study simply focused on the two dimensional flat plate theories for the boundary layer suction. A more accurate representation of the benefits could be achieved through the incorporation of a three-dimensional aerofoil.
A more detailed analysis of our results can be found in our technical report, along with the Knudsen Pump and Boundary Layer models, linked below.
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