The reliability of modern gas turbine engines is largely due to careful damage tolerant design a method of structural design based on the assumption that flaws (cracks) exist in any structure and will continue to grow with usage. With proper monitoring, largely in the form of periodic inspections at conservative intervals reliability and safety is maintained. These methods while reliable can lead to the early retirement of some components and unforeseen failure if design assumptions fail to reflect reality. With improvements to sensor and computing technology there is a growing interest in a system that could continuously monitor the health of structural aircraft as well as forecast future damage accumulation in real-time. Through the use of two-dimensional and three-dimensional numerical modeling the initial goals and findings for this continued work include: (a) establishing measurable parameters directly linked to the health of the blade and (b) the feasibility of detecting accumulated damage to the structural material and thermal barrier coating as well as the onset of damage causing structural failure.

The cooling systems in a gas turbine are especially important as the turbine blades and vanes are exposed to extreme temperatures. The relatively cool air is extracted from the compressors and fed to the turbines to cool the turbine blades. The manufacturing of these blades and channels used to cool is especially complicated using conventional manufacturing techniques. Additive Manufacturing (AM) gives the designer much more freedom to design core components. The AM technique currently explored is the Selective Laser Melting process (SLM). The surface area is exposed to the cooling airflow by using lattice structures which can be manufactured at relative ease using AM. This thesis will provide some insights into using AM parts for the cooling, by analyzing the pressure drop that could be expected from superalloys that are manufactured using AM. The surface roughness is an inherent property of the AM components therefore it would be interesting to analyze a turbulent flow through AM channels (CM247LC and INCONEL 939). The thesis deals with turbulent flows as the airflow used for cooling in the gas turbine is most likely turbulent.  The friction factor (Darcy–Weisbach friction factor) is used to relate the impact of the surface roughness to the pressure drop. The results from the previous experiments are contrasted as the flow in the previous experiments was assumed to be fully developed but in reality, it was not. And the accuracy of the previous results to the actual fully developed flow will shed some light on the feasibility of the flow analysis techniques used in the previous experiments. It is found that the previous experimental results for the CM247LC TPs have good agreement with current experimental results but INCONEL 939 exhibits significant deviation. The possible reasons for the deviations are directly linked to the assumptions made to calculate the minor losses. The Test Pieces (TP) analyzed in this thesis have varying length to diameter (L/D) ratios and the impact of the variation of different L/D ratios is analyzed along with varying pressure ratios. Where the flow resistance increases with an increase in L/D and pressure ratio. The technique to accommodate the compressibility of the airflow is also explored in this thesis. Finally, reasons for the manifestation of anomalies are discussed. The probability of the compressibility effects of the airflow on the anomalies was found to be quite high, and concluding remarks are provided.

Wind turbines have been utilized for centuries to harness energy from the wind. Commercial wind turbine blades are typically made from composite materials, which are difficult to recycle, leading to blades ending up in landfills at the end of their lifecycle. Additionally, these materials contribute to microplastic pollution. In response to growing environmental concerns, there has been an increased focus on addressing such issues. The Swedish company SeaTwirl AB develops offshore vertical-axis wind turbines (VAWT), and this study focuses on optimizing the weight of a blade from a new 10-15 MW VAWT concept using steel as the material. Steel has long been recyclable, making it an interesting material for wind turbine blades. The specific steel used in this study is the ultra-high-strength steel "Strenx 1300" from SSAB, which is not only extremely durable but is also expected to be fossil-free by 2026, by implementation of the manufacturing technology HYBRIT. The study found that a single blade made from Strenx 1300, when designed and optimized for 35 years of operational use, would weigh approximately 193.4 tonnes and would require 6016.8 meters of welds with a fatigue class of FAT 125. A rough estimation of the weight of a fiberglass VAWT of the same size resulted in approximately 300 tonnes. Therefore, this study concludes that it may be feasible to construct a commercially competitive VAWT blade using environmentally friendly, fossil-free steel. This approach would make wind energy a more sustainable energy source without the problems of recyclability and microplastic pollution. / Vindkraftverk har använts i århundraden för att utvinna energi från vinden. Kommersiella vindkraftverksblad tillverkas vanligtvis av kompositmaterial, vilket är svårt att återvinna och leder till att bladen hamnar på soptippar vid slutet av deras livscykel. Dessutom bidrar dessa material till mikroplastföroreningar. Som svar påväxande miljöproblem har det därför blivit ett ökat fokus på denna typ av frågor. Det svenska företaget SeaTwirl AB utvecklar vertikalaxliga vindkraftverk (VAWT) för offshore-användning, och denna studie fokuserar på att optimera vikten av ett blad från ett nytt 10-15 MW VAWT-koncept med stål som material. Stål har länge varit återvinningsbart, vilket gör det till ett intressant material för vindkraftverksblad. Det specifika stål som används i denna studie är det höghållfasta stålet "Strenx1300" från SSAB, som inte bara är extremt hållbart, men också förväntas bli fossilfritttill 2026, tack vare implementeringen av tillverkningsteknologin HYBRIT. Studien visade att ett enskilt blad tillverkat av Strenx 1300, när det är utformat och optimerat för 35 års driftstid, skulle väga cirka 193,4 ton och kräva 6016,8 meter svets med en utmattningsklass FAT 125. En grov uppskattning av vikten av en VAWT av samma storlek i glasfiber resulterade i cirka 300 ton. Därför drar denna studie slutsatsen att det kan vara möjligt att konstruera ett kommersiellt konkurrenskraftigt VAWT-blad med miljövänligt, fossilfritt stål. Detta tillvägagångssätt skulle göra vindenergi till en mer hållbar energikälla utan problemen associerade med återvinning och mikroplaster.

Vortex generator jets (VGJs) have been found to be an effective method of active separation control on the suction side of a low pressure turbine (LPT) blade at low Reynolds numbers. The flow mechanisms responsible for this control were studied and documented in order to provide a basis for future improvements in LPT design. Data were collected using a stereo PIV system that enabled all three components of velocity to be measured. Steady VGJs were injected into a laminar boundary layer on a flat plate (non-separating boundary layer) in order to more fully understand the characteristics and behavior of the produced vortices. Both normal (injected normal to the wall) and angled (injected at 30° pitch and 90° skew angles to the freestream) jets were studied. The steady jets were found to create vortices that swept the low momentum fluid up from the boundary layer while transporting high momentum freestream fluid towards the wall, a phenomenon that provides the ingredients for flow control. Pulsed VGJs were then injected on a flat plate with an applied adverse pressure gradient equivalent to that experienced by a commonly tested LPT blade. This configuration was used to study the effectiveness of the flow control exhibited by both normal and angled jets on a separating boundary layer. Time averaged results showed similar boundary layer separation reduction for both normal and angled jets; however, individual characteristics suggested that the control mechanism of the two injection angles is distinct. Steady and pulsed VGJs were then applied to a new aggressive LPT blade design to explore the effect of the jets on a separating boundary layer along the curved blade surface. Steady injection provided flow control through freestream entrainment, while pulsed jets created a two-dimensional, spanwise disturbance that reduced the separated area as it traveled downstream. A detailed fluid analysis of the uncontrolled flow around the blade was performed in order to identify the separation and reattachment points and the area of transition. This information was used as a basis for comparison with the VGJ cases to determine flow control effectiveness.

No description available.