Updating Turbomachinery Aerodynamics Teaching On an Undergraduate Course Using 3D Design Tools

This paper outlines the update of a turbomachinery course to cover 3D aerodynamics using a Reynolds Averaged-Navier Stokes solver. Prior to the activities outlined in this paper the course was taught in a conventional way with a series of lectures and a timed, written, open book examination in a formal exam setting. Students were equipped with a calculator and set of notes including correlations from Howell and Soderberg. This limited the depth of any aerodynamic problem they could get through and so they were restricted to simple design or analysis exercises.The genesis of the course update was the release in 2017 of “MULTALL OPEN” [1] a freely available turbomachinery design system and this was adopted as the course software - although other software choices were considered.Students now produce two turbomachinery designs during the course. These are both based on the J85 turbojet - largely to keep cycle calculations to a minimum but it was also important to ensure that students recognise that they were completing a real engineering task. The first task was a 3D aerodynamic design of multi-stage turbine which includes compressible flow, tip clearance and stacking techniques such as lean or sweep. The second task was a midspan (2D) compressor design. Assessment was by means of a short report where the best students report on their design choices, provide critical analysis of the design using appropriate post-processing techniques and compare their designs to the state of the art in the wider literature.As well as describing the successes and challenges of the update to 3D design methods the paper provides some guidance for educators thinking about adopting a similar approach

Internal wave observations off Isle Verte

A comparison is made between series of high frequency internal waves observed in the St. Lawrence estuary from an aircraft and in a field program at a later date. Wave generation is associated with the propagation of a warm surface front during each ebb flow. The number of waves, as evidenced by surface slicks, is thought to vary as does the stability of the upper layer of the water column

Experiments in a rotating source-sink annulus

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August, 1971An experimental investigation of the different flow regimes in a rotating source-sink annulus is described. Both the steady and transient velocities are measured over a large range of Ekman Reynolds number and Rossby number. Differing probe configurations are used to investigate the corresponding motions in spatially separated regions of the annulus. The steady interior circulation field exhibits a strong dependence on the imposed flux values. The non-dimensional circulation increases with radius over a certain radial range for higher system Rossby number. The observed profile changes are related to the existence of an unstable Ekman layer at some inner radial position. The thickness of the observed Ekman layers is typically 85% of the theoretical scale height. For higher local Reynolds number (ReL), the thickness is generally much smaller. The width of the sidewall boundary layer adjacent to the sink increases with larger system Rossby number. Adjacent to the source, the radial boundary layer is wider than that at the sink wall. Observed oscillations are separable into three types. For ReL > 50, instability waves are observed in the Ekman layer flow. In the same Re range, inertial oscillations are detected in the interior region of the annulus. The observed inertial wave frequency at differing radial positions is explained by incorporating Doppler shift corrections and taking account of the steady circulation profiles. The radial wavelength of the inertial waves corresponds to the length of the Class A Ekman layer instabi1ity. For small values of Re and local Rossby number, an axisymmetric disturbance, with a characteristic frequency slightly greater than therotation rate, is observed at the outer radial positions

Applying wind simulations for planning and operation of real-time thermal ratings.

Real-time thermal ratings (RTTRs) are an emerging technology that allows the rating of electrical conductors to be estimated using real-time local weather observations. In many cases this leads to a very significant (typically 50%-100%) increase in rating with respect to conventional approaches. Conductor rating is heavily influenced by wind speed and direction. Consequently, in this paper, computational wind simulations commonly employed by the wind energy industry have been applied to inform rating estimation during network planning and operation. This provides an exciting opportunity to allow the identification of determining conductor spans to inform network designers of the rating potential of different conductor routes to estimate the additional wind energy that could be accommodated through the enhanced line rating and to allow intelligent placement of the monitoring equipment required to implement RTTR. The wind simulation data were also used to allow more accurate estimation of conductor ratings during operation. Two case studies taken from actual trial sites in the U.K. are presented to demonstrate that these techniques can provide a real world benefit

The influence of condenser pressure variation and tip leakage on low pressure steam turbine exhaust hood flows

This paper aims to highlight the importance of the accurate computational modelling of both the inlet and outlet exhaust hood boundary conditions. The computations presented are calculated using the public domain low pressure exhaust diffuser test case proposed by Burton in 2012. The original test case did not include the effect of tip leakage on diffuser flows, but this paper describes the inclusion of tip leakage and the results are shown to be in line with the outputs produced by other authors. The key advance in this paper is that calculations were conducted with a representative condenser pressure gradient caused by the temperature variation inside the condenser tube nest. It is shown that accurately modelling the exit boundary calculation has a large influence on the flow structure and a smaller influence on the pressure recovery inside the exhaust diffuser. This influence is smaller than that seen by other authors when including unsteady effects or accounting for the circumferential non-uniformity of the turbine exit flow but will need to be included in design calculations as diffuser design advances

Investigating Endwall-Blade Fillet Radius Variation to Reduce Secondary Flow Losses

In turbomachinery the joint between a turbine blade and the endwall often involves a fillet. Previous studies show that this fillet significantly influences the secondary flows despite regularly being omitted from simulation and testing, specifically that a uniform fillet radius of 16% axial chord increased endwall losses by 10%. It was proposed that a variable radius fillet could reduce secondary flows and the associated endwall losses. This paper describes a computational study to determine what variable radius fillet is required for optimal performance in the cascade. The variable radius fillet ranges from 0.5% to 16% of axial chord and was found using a genetic algorithm optimisation. Although this is a computational study the design offers physically plausible mechanisms by which the extra losses introduced by fillets may be reduced. This paper also suggests a generalised rule of fillet radius variation to minimise endwall losses. A large radius is required on the leading edge that reduces slowly along the pressure side but rapidly on the suction side such that the smallest permitted radius is applied to the suction side. A medium radius is required at the trailing edge

The benefits of turbine endwall profiling in a cascade

Non-axisymmetric profiled endwalls have been shown to reduce losses and secondary flow both in cascades and in rig tests. This paper presents experimental results which quantify the benefits of loss reduction in the cascade with particular attention to accuracy. The paper compares the benefits achieved in experiment to the results predicted by computational fluid dynamics (CFD). The results show that both the experiment and CFD give significant reductions in secondary flow. A reduction of 31 per cent in secondary loss has been measured for the best case, but the CFD gives only a small reduction in loss. Previous studies on the planar endwall have shown significant areas of transitional flow, so the surface flow has been studied with the aid of surface-mounted hot films. It was concluded that the loss reductions were not due to changes in regions of laminar and turbulent flow

Financial health indicators: an analysis of financial statement information to determine the financial health of DoD contractors

MBA Professional ReportPrior to awarding a contract, government contracting officers must be able to determine the financial health of prospective contractors. In fact, according to the Federal Acquisition Regulation (FAR) 9.104- 1(a), the very first general requirement to being considered a responsible prospective contractor is to show adequate financial resources to perform the contract or the ability to obtain financing. The purpose of this research is to identify a financial assessment framework that could assist DOD contracting officers with determining the financial health of potential DOD contractors. This research study may help DOD contracting officers determine the financial health of potential contractors prior to awarding a contract. The findings of this study provide a recommended framework that a contracting officer could follow in order to assess the financial health of a prospective contractor. The framework includes a ratio analysis using selected ratios compiled by this study, as well as a comparative analysis using industry average driven data. The framework also incorporates horizontal and vertical analyses, as well as bankruptcy and fraud analyses. The financial assessment framework created in this study is a comprehensive financial health assessment tool that can be utilized by DOD contracting officers.http://archive.org/details/financialhealthi1094551703Lieutenant Commander, United States NavyLieutenant, United States NavyLieutenant, United States NavyApproved for public release; distribution is unlimited