PhD thesis gives the aircraft industry new methods to reduce emissions

​By utilising the design framework developed as part of Marcus Lejon’s PhD thesis, highly efficiency compressors can be designed which would contribute to reduce emissions of greenhouse gases from aviation.
​Aircraft engine manufacturers strive to improve current state of the art designs through continuous development efforts. By improving existing designs and exploring new alternatives, the goal is to reduce the fuel consumption. 

To achieve a low fuel consumption, turbofan engines should operate at a high overall pressure ratio which is commonly achieved by an axial compressor. An axial compressor consists of a set of consecutive stages, each consisting of a rotating and stationary blade row. While a compressor should operate with a high-pressure ratio, it should not operate too close to its stability limit where surge can occur. Care must be taken when designing a compressor so that it can operate safely and with high efficiency. If the pressure increase across the compressor is high, it may be operating close to its stability limit. Beyond this point, surge can occur, a dangerous phenomenon where the performance drops and the flow through the compressor may even reverse direction. 

”My work has focused on a framework for designing the low-pressure system of an aircraft engine. To determine an appropriate degree of complexity to include in the computational model, and to determine an appropriate measure to quantify stability of a compressor.” says Marcus Lejon. 

Furthermore, aspects which may be detrimental to performance have been investigated, namely the impact of geometric variations which occur from the manufacturing process of a compressor blade and surface degradation from in-service use. 

As a part of his work, he has determined an appropriate measure for stability and applied it in the design of a three-stage compressor with high efficiency and stability. 

“This exercise showed the versatility of the method by designing different stages, and demonstrated that the proposed stability measure worked well in the design phase” says Marcus Lejon 

By utilising the design framework developed, highly efficiency compressors can be designed which would contribute to reduce emissions of greenhouse gases from aviation. The design framework and the method used to analyse manufacturing variations will be used at GKN Aerospace, the collaborative partner in his project. 

Marcus Lejon will present and defend his PhD thesis Aerodynamic design framework for low-pressure compression systems June 8 at 10.00 in lecture hall HA2.

Published: Mon 04 Jun 2018.