Detailed Experimental Study of the Flow in a Turbine Rear Structure at Engine Realistic Flow Conditions

A good aerodynamic design of the turbine rear structure (TRS) is crucial for improving efficiency and reducing emissions from aero-engines. This paper presents a detailed experimental evaluation of an engine realistic TRS which was studied in an engine-realistic rig at Chalmers University of Technology, Sweden. The TRS test section was equipped with three types of outlet guide vanes (OGVs) which are typical of modern state-of-the-art TRS: regular vanes, thickened vanes, and vanes with an engine mount recess (a shroud bump). Each of the three vane geometries was studied under on-design and off-design conditions at a fixed flow Reynolds number of 235,000. The study shows that the off-design performance of the TRS strongly depends on the presence of the local flow separation on the OGV suction side near the hub, which is greatly affected by the vane pressure distribution and inlet conditions. Similarly, the OGVs with increased thickness and with a vane shroud bump are shown to affect the performance of the TRS by influencing the losses on the OGV suction side near the hub. Furthermore, the presence of the bump is shown to have a noticeable upstream influence on the outlet flow from the low-pressure turbine and a noticeable downstream influence on the outlet flow from the TRS

Experimental and Numerical Study of Laminar-Turbulent Transition on a Low-Pressure Turbine Outlet Guide Vane

This work presents an experimental and numerical investigation on the laminar-turbulent transition and secondary flow structures in a Turbine Rear Structure (TRS). The study was executed at engine representative Reynolds number and inlet conditions at three different turbine load cases. Experiments were performed in an annular rotating rig with a shrouded low-pressure turbine upstream of a TRS test section. The numerical results were obtained using the SST k–ω turbulence model and the Langtry- Menter γ–θ transition model. The boundary layer transition location at the entire vane suction side is investigated. The location of the onset and the transition length are measured using IR thermography along the entire vane span. The IR-thermography approach was validated using hot-wire boundary layer measurements. Both experiments and CFD show large variations of transition location along the vane span with strong influences from endwalls and turbine outlet conditions. Both correlate well with traditional transition onset correlations near midspan and show that the transition onset Reynolds number is independent of the acceleration parameter. However, CFD tends to predict an early transition onset in the midspan vane region and a late transition in the hub region. Furthermore, in the hub region, CFD is shown to overpredict the transverse flow and related losses.Disclaimer:\ua0The content of this article reflects only the authors’ view. The Clean Sky 2 Joint Undertaking is not responsible for any use that may be made of the information it contains

Experimental and numerical flow analysis of an engine-realistic state-of-the-art turbine rear structure

This paper presents experimental and numerical CFD studies of the aerodynamics of a turbine rear structure (TRS). The TRS test geometry is an engine-realistic state-of-the-art design with a polygonal outer case, recessed engine mount bumps, and three different vane types: regular vanes, bump vanes in bump sectors, and thick vanes. Using three different sector types simultaneously was found to be crucial for the inlet boundary conditions. Experiments were performed in a modern rotating test facility with an LPT stage upstream of the TRS. A Reynolds number of 350,000 was used, representative of a TRS in a narrow-body geared turbofan engine. The TRS performance was analyzed both at on- and off-design conditions and a thorough side-by-side comparison of CFD and experiments was performed. Static-pressure-distributions, turning and outlet flow-angles, wakes and losses, and surface-flow visualizations and outlet total pressure contours are presented. The thick vane showed good aerodynamic performance, similar to the regular vane. For the bump vane, the mount bumps were found to generate additional local separations and secondary flows, resulting in extra losses. In the regions with strong secondary flows CFD over-predicts the wakes, whereas the wakes around midspan, where secondary flows have a smaller influence, are predicted well

Experimental and Numerical Flow Analysis of an Engine-Realistic State-of-the-Art Turbine Rear Structure

This paper presents experimental and numerical CFD studies of the aerodynamics of a turbine rear structure (TRS). The TRS test geometry is an engine-realistic state-of-the-art design with a polygonal outer case, recessed engine mount bumps, and three different vane types: regular vanes, bump vanes in bump sectors, and thick vanes. Using three different sector types simultaneously was found to be crucial for the inlet boundary conditions. Experiments were performed in a modern rotating test facility with an LPT stage upstream of the TRS. A Reynolds number of 350,000 was used, representative of a TRS in a narrow-body geared turbofan engine. The TRS performance was analyzed both at on- and off-design conditions and a thorough side-by-side comparison of CFD and experiments was performed. Static-pressure-distributions, turning and outlet flow-angles, wakes and losses, and surface-flow visualizations and outlet total pressure contours are presented. The thick vane showed good aerodynamic performance, similar to the regular vane. For the bump vane, the mount bumps were found to generate additional local separations and secondary flows, resulting in extra losses. In the regions with strong secondary flows CFD over-predicts the wakes, whereas the wakes around midspan, where secondary flows have a smaller influence, are predicted wel

Correlations within and between Markets and Commodities

With a growing interaction between markets, when all markets and exchanges are being inuenced by the globalisation, the correlations between markets and com- modity exchanges becomes an interesting topic. How are they related to each other is the question this study tries to answer. The study includes a large number of the largest national stock markets and some of the most important commodities trades world wide. Correlations analyses are conducted among these securities to find out what relationships that exists, sometime it also tries to pose possible reasons to the relationships. Data time series for 33 di_erent national stock markets and 17 commodities are analysed in terms of rate of return and standard deviation. Correlation analyses are conducted for the markets as well for the commodities, also correlations between the markets and the commodities are analysed. The study includes time series data updated both daily and quarterly for analysing both short and long term behaviours and relationships. Some of the interesting results are presented below. During the time analysed, the study suggests that the Moroccan stock market and Gold have been the best per- forming assets in terms of risk adjusted return measured on a quarterly basis. If risk is not considered, the developing markets Brazil, Russia and Turkey have been the most lucrative investments. It can be shown in the study that the western countries are closely connected to each other. Markets for closed off countries such as China and Saudi Arabia show very little correlation to other markets. The American mar- kets inuences the most eastern countries, much more than the other way around. Metals used in alloys important for the industry have higher correlations to each other and towards the markets than other commodities, i.e. other metals, energy sources and soft goods that also are included in the study

Intermediate View Interpolation of Stereoscopic Images for 3D-Display

This thesis investigates how disparity estimation may be used to visualize an object on a 3D-screen. The first part looks into different methods of disparity estimation, and the second part examines different ways to visualize an object from one or several stereo pairs and a disparity map. Input to the system is one or several stereo pairs, and output is a sequence of images of the input scene but from more angles. This sequence of images can be shown on Setred AB's 3D-screen. The system has high real time demands and the goal is to do the disparity estimation and visualization in real time. In the first part of the thesis, three different ways to calculate disparity maps are implemented and compared. The three methods are correlation-based, local structure-based and phase-based techniques. The correlation-based methods cannot satisfy the real-time demands due to the large number of 2D-convolutions required per pixel. The local structure-based methods have too much noise and cannot satisfy the quality requirements. Therefore, the best method by far is the phase-based method. This method has been implemented in Matlab and C and comparisons between the different implementations are presented. The quality of the disparity maps is satisfying, but the real-time demands cannot yet be fulfilled. The future work is therefore to optimize the C code and move some functions to a GPU, because a GPU can perform calculations in parallel with the CPU. Another reason is that many of the calculations are related to resizing and warping, which are well-suited to implementation on a GPU

On Exergy and Aero Engine Applications

Aero engine performance analysis is highly multidimensional using various measures of component performance such as turbomachinery and mechanical efficiencies, and pressure loss coefficients. Using conventional performance analysis, relying on only the first law of thermodynamics, it is possible to understand how the performance parameters affect the component performance, but not how the component performance relates to the system performance. A comprehensive framework has been detailed to analyze an aero engine in one common currency by complementing the analysis with the second law of thermodynamics. As it yields a measure of the lost work potential in every component it is used to relate the component performance to the system performance. The theory includes a more detailed layout of all the terms that apply to a propulsion unit than presented before and is here adopted to real gases to be used in state of the art performance codes. The theory is also extended upon by presenting the installed rational efficiency, a true measure of the propulsion subsystem performance, including the installation effects of the propulsion subsystem as it adds weight and drag that needs to be compensated for in the performance assessment.The exergy methodology is applied to a modern direct-drive two-spool turbofan, chosen for its dominating market share in modern commercial aviation. The loss sources during an aircraft mission are then assessed and yield the major contributors in the entropy generated during combustion, the thermal energy leaving the nozzle and the exhaust nozzle kinetic energy that is not contributing to the thrust. Radical technology that can be utilized to address each specific loss are thereafter detailed. This includes intercooled and recuperated cycles, reheated cycles, bottoming Rankine cycles, pulse detonation combustion, piston topped composite cycles, nutating disc combustion, and open rotor and other ultra high bypass architectures