Testing and Analysis of a Boundary Layer Turbine in Steam Conditions

Partners: Wesley Turbines

Many turbines require high temperatures to operate economically. An alternative to conventional turbines are Tesla turbines which utilise a bladeless design. Wesley Turbines have designed and built a kilowatt scale prototype based on the Tesla design, with the aim of operating on waste heat sources at low capital costs. Testing of the turbine has been conducted at Durham University to assess the technical viability of the design, and to provide a robust data set to inform on technology development decisions. Initial tests were conducted in the Durham University Blow Down Facility, using dry air, to provide baseline properties and assess the integrity of the design. Following design improvements, a steam test rig was established, and the turbine tested under operational conditions. Analytical and finite element models have been used to supplement these experimental results and provide full performance maps of the turbine operating in steam conditions.

Entropy Generation Rate for Profiled Endwall Design in Turbines

Secondary flow losses in turbomachinery are associated with the presence of skin friction on endwalls and the development of flow vorticity, and act to decrease efficiency. Profiled End Walls (PEWs) provide a solution to reducing secondary losses. Entropy generation rate, a measure of local loss production, was used for the first time as a variable for the iterative design optimisation of Profiled End Walls (PEWs). Computational fluid dynamics was used to solve the Reynolds-Averaged Navier-Stokes equations in three dimensions. A genetic algorithm was designed, with 3000 PEWs evaluated to achieve a design with a 10% reduction in entropy generation rate. This design was validated through experiments in the Durham Cascade, retrofitted with a hydraulically smooth PEW. Using Entropy generation rate as a variable for PEW design was shown to be a viable approach to reduce secondary losses and improve turbine efficiency.

Modelling the Impact of Leading-Edge Erosion Progression on The Electricity Produced by Wind Turbines

Partners: Ørsted and Siemens Gamesa Renewable Energy

Description: Erosion on wind turbine blades occurs toward blade tips due to high-speed particle impacts, with blade tip-speeds of around 100ms-1. Impacts alter the surface geometry which adversely affects the aerodynamic flow and reduces Annual Energy Production (AEP). An issue affecting owners is understanding how erosion, and AEP losses change over time. Traditional and novel methods were combined to produce an analytical model to predict changes to blade surface geometry caused by rain erosion. The model was validated against offshore windfarm inspection data. Experiments in the Durham 2m wind tunnel, and 2D computational fluid dynamics were used to establish a method of calculating expected AEP losses under varied climatic conditions during wind turbine operation. Impact Acceleration Account (IAA) funding was secured to transfer the models developed into an industry tool for optimising maintenance operation planning. This tool was delivered to Ørsted at the project’s conclusion. The project received an award for the IAA project with the best career development support.

Formation and Evolution of Vortex Rings with Weak to Moderate Swirl, and their Implications for Enhancing Vortex Ring Circulation

Description: Vortex rings occur in a variety of natural situations, from volcanic eruptions to aspects of blood transfer during the cardiac cycle, but also have applications from drug delivery to optimising fuel compression in nuclear fusion. This aim of this work was to address a gap in the literature by studying the influence of adding swirl on vortex ring flow dynamics and the effect of preceding vortex rings enhancing vortex ring formation. A Finite Volume Method approach was taken using computational fluid dynamics software OpenFOAM to numerically model vortex ring propagation. Experiments in the Durham Multifunctional Jet generator were conducted to supplement the computational results by using a dual phase piston-cylinder arrangement to generate vortex rings with swirl, alongside stereoscopic Particle Image Velocimetry to calculate the 3D velocity fields.

Flow Around Stationary and Oscillating Polygonal Cylinders

Vortex shedding around structures can cause large-amplitude vibrations, and large structural forces. Vortex Induced Vibrations (VIVs) are therefore relevant in many engineering applications such as offshore strictures and tall buildings. Traditionally research has largely been confined to circular cylinders. This project focussed on the vortex shedding properties of polygonal cylinders with the aim of comparing responses with circular cylinders to assess their suitability in applications where circular cylinders are traditionally used. This project undersaw repurposing the Durham Recirculating Wind Tunnel for improved flow conditioning and PIV testing to further analyse VIVs. Both 3D computational fluid dynamics studies and experiments in the newly commissioned wind tunnel were undertaken to assess polygonal cylinder flow dynamics. It was identified that flow separation occurs on the corners of the polygon, presenting new applications in the control of vortex shedding. Strong VIV amplitudes on the pentagonal cylinder also highlighted their potential in bladeless wind turbines.

CONFLOWS – Control of FLOating Wind Farms with Wake Steering (phase 1)

Partners: DNV, NREL, Marine Power Systems

As wind energy is predicted to occupy an increasing proportion of the energy-mix, floating offshore wind is considered to have the largest untapped potential, as recently reported by the International Energy Agency (IEA), with an estimated capacity of 2TW off the USA coasts alone. A strong interest has been given to the use of Wind Farm Control (WFC) strategies to optimise production by controlling the whole wind farm as an integrated system. Wake steering is currently regarded as the most promising. It consists of intentionally yawing some wind turbines to deflect the wake away from downstream turbines. This study will focus on investigating the technical and economic feasibility of using wake steering in floating offshore wind farms, where each turbine is operated using optimised set-points calculated for the operational conditions at the site.