Approaches for rejuvenating the natural product discovery process from Streptomyces

In 1940, a bacterial enzyme was identified which was capable of destroying penicillin (Abraham & Chain, 1940). This discovery actually predated both the awarding of the Nobel Peace Prize in Medicine and Physiology for its discovery and the year it became available over the counter for the first time in the United States by five years (Gaynes, 2017). In short, Antimicrobial Resistance (AMR) is a phenomenon that has long plagued the field of natural product drug discovery. To attempt to overcome come this, it is imperative that the natural product discovery field is shunted forward by the continued advancement of microbial culturing methods and analytical tools (Atanasov et al., 2021). This work contributes towards the rejuvenation of natural product drug discovery by describing new methods for eliciting potentially novel antimicrobial specialised metabolites, as well as outlining metabologenomic methods for analysing the resultant datasets. [See thesis text for references].In 1940, a bacterial enzyme was identified which was capable of destroying penicillin (Abraham & Chain, 1940). This discovery actually predated both the awarding of the Nobel Peace Prize in Medicine and Physiology for its discovery and the year it became available over the counter for the first time in the United States by five years (Gaynes, 2017). In short, Antimicrobial Resistance (AMR) is a phenomenon that has long plagued the field of natural product drug discovery. To attempt to overcome come this, it is imperative that the natural product discovery field is shunted forward by the continued advancement of microbial culturing methods and analytical tools (Atanasov et al., 2021). This work contributes towards the rejuvenation of natural product drug discovery by describing new methods for eliciting potentially novel antimicrobial specialised metabolites, as well as outlining metabologenomic methods for analysing the resultant datasets. [See thesis text for references]

Experimental studies of orbital electron capture

Abstract Not Provided

Conjugate Modelling Of A Closed Co-Rotating Compressor Cavity

Robust methods to predict heat transfer are vital to accurately control the blade-tip clearance in compressors and the radial growth of the disks to which these blades are attached. Fundamentally, the flow in the cavity between the co-rotating disks is a conjugate problem: the temperature gradient across this cavity drives large-scale buoyant structures in the core that rotate asynchronously to the disks, which in turn governs the heat transfer and temperature distributions in the disks. The practical engine designer requires expedient computational methods and low-order modeling. A conjugate heat transfer (CHT) methodology that can be used as a predictive tool is introduced here. Most simulations for rotating cavities only consider the fluid domain in isolation and typically require known disk temperature distributions as the boundary condition for the solution. This paper presents a novel coupling strategy for the conjugate problem, where unsteady Reynolds averaged Navier–Stokes (URANS) simulations for the fluid are combined with a series of steady simulations for the solid domain in an iterative approach. This strategy overcomes the limitations due to the difference in thermal inertia between fluid and solid; the method retains the unsteady flow features but allows a prediction of the disk temperature distributions, rather than using them as a boundary condition. This approach has been validated on the fundamental flow configuration of a closed co-rotating cavity. Metal temperatures and heat transfer correlations predicted by the simulation are compared to those measured experimentally for a range of engine-relevant conditions.</p

Investigation of Reverse Swing and Magnus Effect on a Cricket Ball Using Particle Image Velocimetry

Lateral movement from the principal trajectory, or &ldquo;swing&rdquo;, can be generated on a cricket ball when its seam, which sits proud of the surface, is angled to the flow. The boundary layer on the two hemispheres divided by the seam is governed by the Reynolds number and the surface roughness; the swing is fundamentally caused by the pressure differences associated with asymmetric flow separation. Skillful bowlers impart a small backspin to create gyroscopic inertia and stabilize the seam position in flight. Under certain flow conditions, the resultant pressure asymmetry can reverse across the hemispheres and &ldquo;reverse swing&rdquo; will occur. In this paper, particle image velocimetry measurements of a scaled cricket ball are presented to interrogate the flow field and the physical mechanism for reverse swing. The results show that a laminar separation bubble forms on the non-seam side (hemisphere), causing the separation angle for the boundary layer to be increased relative to that on the seam side. For the first time, it is shown that the separation bubble is present even under large rates of backspin, suggesting that this flow feature is present under match conditions. The Magnus effect on a rotating ball is also demonstrated, with the position of flow separation on the upper (retreating) side delayed due to the reduced relative speed between the surface and the freestream

A Model of Mass and Heat Transfer for Disc Temperature Prediction in Open Compressor Cavities

Accurate prediction of heat transfer in compressor cavities is crucial to the design of efficient and reliable aircraft engines. The heat transfer affects the thermal expansion of the compressor rotor and, in turn, the tip clearance of the compressor blades. This paper presents a novel, physically-based predictive theoretical model of heat transfer and flow structure in an open compressor cavity, which can be used to accurately calculate disc temperatures. The radially higher region of the cavity is dominated by buoyancy effects created by the temperature difference between the hot mainstream flow and the axial through flow used to cool the turbine. Strong interaction between the air in the cavity and this through flow creates a mixing region at low radius. For a given geometry, the heat transfer and flow physics are governed by four parameters: the rotational Reynolds number Re ϕ, the buoyancy parameter βΔT, the compressibility parameter χ, and the Rossby number Ro. The model quantifies both the buoyancy- and throughflow-induced mass and heat transfer, producing a reliable prediction of the disc and air temperatures. The model takes into account a two-fold effect of the throughflow: being entrained into the cold radial plumes directly and creating a toroidal vortex in the radially lower region of the cavity. The exchange of mass between the cavity and throughflow is related to the mass flow rate in the radial plumes in the buoyancy-induced region, considering the effect of flow reversal at low Ro. The model is validated using data collected in the Bath Compressor Cavity Rig and can be incorporated in engine design codes to robustly compute the thermal stress and expansion of the compressor rotor, contributing to more efficient engine designs.</p

Influence of Flow Coefficient on Ingress Through Turbine Rim Seals

Rim seals are critical in terms of limiting the temperature of highly-stressed engine components but function with a penalty to the power output and contribute to entropy gain stemming from mixing losses in the turbine. Ingress through rim seals is influenced by the presence of rotor blades and stator vanes, and the mainstream flow coefficient in the annulus that determines the corresponding swirl. This paper presents an experimental study of ingress upstream and downstream of the rotor disc in a 1.5-stage rig with double radial clearance rim seals. Two rotor discs were used, one with blades and one without, and two platforms were used downstream of the rotor, one with vanes and one without. Tests were conducted at two rotational speeds and a range of flow conditions was achieved by varying the annulus and sealing mass flow rates. Concentration effectiveness, swirl and steady pressure measurements separated, for the first time, the influence of the blades and vanes on ingressover a wide range of flow conditions. Measurements on the downstream stator platform provide added insight into the complex interaction between the egress and the mainstream.Measurements of unsteady pressure revealed the presence of large-scale structures, even in the absence of blades. The number and speed of the structures was shown to depend on the flow coefficient and the purge flow rate

Flow Instability Effects Related to Purge through a Gas Turbine Chute Seal

This paper investigates flow instabilities inside the cavity formed between the stator and rotor disks of a high-speed turbine rig. The cavity rim seal is of chute seal design. The influence of flow coefficient on the sealing effectiveness at constant purge flow rate through the wheel-space is determined. The effectiveness at different radial positions over a range of purge flow conditions and flow coefficients is also studied. Unsteady pressure measurements have identified the frequency of instabilities that form within the rim seal, phenomena which have been observed in other studies. Frequencies of these disturbances, and their correlation in the circumferential direction have determined the strength and speed of rotation of the instabilities within the cavity. Large scale unsteady rotational structures have been identified, which show similarity to previous studies. These disturbances have been found to be weakly dependent on the purge flow and flow coefficients, although an increased purge reduced both the intensity and speed of rotation of the instabilities. Additionally, certain uncorrelated disturbances have been found to be inconsistent (discontinuous) with pitchwise variation.QC 20220503</p

A New Interpretation of Hot Gas Ingress Through Turbine Rim Seals Influenced by Mainstream Annulus Swirl

Rim seals are fitted at the periphery of the stator and rotor disks to reduce the adverse effects of hot gas ingress on highly stressed turbine components limited by temperature. Ingress is induced by rotational effects such as disk pumping, as well as by asymmetric pressure-driven unsteady phenomena. These influences superpose to form a complex flow-physics problem that is a challenge for computational fluid dynamics. Engine designers typically use practical low-order models that require empirical validation and correlating parameters. This paper identifies the swirl ratio in the mainstream annulus as a dominant characterizing parameter to predict ingress. This is a new interpretation that is supported by extending a low-order model based on turbulent transport using an effective eddy mixing length based on the difference in swirl between the annulus and seal clearance. Experimental measurements were made using a 1.5-stage turbine rig at low Reynolds number. The influence of annulus swirl ratio was investigated over a range of flow conditions and two rim-seal geometries, with the ingress quantified using CO 2tracer concentration in the sealing flow. The concentration data were complemented by measurements in the annulus using a five-hole aerodynamic probe.</p

Measurement of Heat Transfer and Flow Structures in a Closed Rotating Cavity

Buoyancy-induced flow occurs inside the rotating compressor cavities of gas turbines. These cavities are usually open at the inner radius, but in some industrial gas turbines, they are effectively closed. This paper presents measurements of the disk heat transfer and rotating flow structures in a closed cavity over a wide range of engine relevant conditions. These experimentally derived distributions of disk temperature and heat flux are the first of their kind to be published. The radial distribution of the nondimensional disk temperature virtually collapsed onto a single curve over the full experimental range. There was a small, monotonic departure from this common curve with increasing Reynolds number; this was attributed to compressibility effects where the core temperature increases as the rotational speed increases. These results imply that, if compressibility effects are negligible, all rotating closed cavities should have a disk temperature distribution uniquely related to the geometry and disk material; this is of important practical use to the engine designer. Unsteady pressure sensors detected either three or four vortex pairs across the experimental range. The number of pairs changed with Grashof number, and the structures slipped relative to the rotating disks by less than 1% of the disk speed.</p