A power electronic controlled dump load with negligible harmonics for accurate loading used in testing small wind turbines

Permanent magnet synchronous generators (PMSG) are at the core of small scale wind power generators manufactured by a wide range of manufacturers in different configurations: vertical or horizontal axis blades, with various geometries and aerodynamics of the blades; by installing these small scale wind turbines in very large numbers at household levels, it is expected that these will make a positive contribution to the increase of renewable energy generation, reducing the use of fossil fuels that are blamed for climate change. However, a proper evaluation of the technical specification of these small scale wind generators in various weather conditions is necessary in order to assess the full potential of benefits. This paper reports on the implementation and testing of a power electronic dump load that allows continuously adjustable loading of a PMSG with sinusoidal currents and have the capability to self synchronize to its frequency/speed whilst avoiding transient/loosing of synchronism

Experimental investigation into droplet impingement upon moving films using high speed video and thermal imaging

Aeroengine bearing chambers are geometrically complex, typically containing shafts, bearings, seals and stationary components. Oil is supplied for lubrication and cooling and so the chamber contains a highly rotating two-phase (oil/air) flow where the oil is typically present as droplets, ligaments, mist and films. These films may be thick or thin and film speed varies with chamber location. It is desirable to know a priori the outcome of a droplet-film impact event in terms of mass, momentum and energy transfer. There is a significant body of research on the interaction between droplets and static films. The experimental parameter space has been characterised on the basis of film thickness and impact parameter to predict the outcome of an impingement. The impingement of droplets on moving films has only begun to be investigated over the last decade and consequently models have not yet been developed and the parameter space has barely begun to be characterised. Within this paper results are presented from an experimental study in which water droplets of 3 mm and 3.8 mm at 20°C falling under the influence of gravity impinged onto water films flowing down an inclined plane. Film temperature was 30°C and film thicknesses were between 2.3 mm and 4.2 mm. High speed imaging was used to determine the impingement outcomes and cavity morphology. A high speed infrared camera was used to determine the extent of the thermally affected region and its temperature behaviour. We find that by using the resultant droplet velocity (combining droplet and film velocities) the film impingement outcomes can be characterised into regions very similar to those for static films. The data is presented as a function of splashing parameter and non-dimensional film thickness. It was observed that for these impacts on supercritical films (Fr > 1) there is less propensity for secondary droplet formation through jet breakup than on static and subcritical films (Fr < 1). Data was obtained for extent of the thermally affected region. It was found that the cooler droplet liquid spreads over the inside of the crater before heating up to film temperature. Development of crater shape and size was also studied and data compared to established models for droplet impact on deep static films. During the initial stages of an impact crater area increases similarly to that for static films although the crater shape itself is less similar and is asymmetrical due to the film motion

Application of high speed filming techniques to the study of rearwards melt ejection in laser drilling

Melt ejection is the dominant material removal mechanism in long, ms, pulse laser drilling of metals, a process with applications such as the drilling of cooling holes in turbine blades. Droplets of molten material are ejected through the entrance hole and, after breakthrough, through the exit hole. High speed filming is used to study the ejected material in order to better understand how this debris may interact with material in the immediate vicinity of the drilled hole. Existing studies have quantified various aspects of melt ejection, however they usually focus on ejection through the entrance hole. This work concentrates on rear melt ejection and is relevant to issues such as rear wall impingement. A 2kW IPG 200S fibre laser is used to drill mild steel. High speed filming is combined with image analysis to characterise the rearward-ejected material. Particle size and velocity data is presented as a function of drilling parameters. It is concluded that high speed filming combined with image analysis and proper consideration of process limitations and optimisation strategies can be a powerful tool in understanding resultant debris distributions

Study of gas-sheared liquid film in horizontal rectangular duct using high-speed LIF technique: Three-dimensional wavy structure and its relation to liquid entrainment

© 2014 The Authors. The flow of a liquid film sheared by high velocity gas stream in a horizontal rectangular duct was investigated using a high-speed laser-induced fluorescence technique. Measurements of local film thickness were resolved in both longitudinal and transverse coordinates with high spatial and temporal resolution. It was found that the generation of fast and slow ripples by the disturbance waves was qualitatively the same as it was observed earlier in completely different conditions. The transverse size and curvature of the disturbance waves and ripples were measured. A relationship between the three-dimensional structure of ripples on top of disturbance waves and the two mechanisms of liquid entrainment, known as 'bag break-up' and 'ligament break-up', is proposed

Study of bubbles entrapped into a gas-sheared liquid film

The surface of a thick liquid film under strong gas shear is covered by large-scale disturbance waves and small-scale ripples. Disruption of these ripples on top of disturbance waves by the gas stream leads to the creation of droplets that are entrained into the gas core and may deposit back onto the film surface. In addition, gas may be entrapped by the liquid film in the form of bubbles of various sizes. In this work, the study of gas bubble creation was performed in a horizontal rectangular duct using the brightness- based laser-induced fluorescence technique. With this technique, the instantaneous height of the liquid film was measured with a 40 μm spatial resolution over a 51 mm by 20 mm area at speeds of 10 kHz. The entrapped bubbles and entrained/depositing droplets are detectable in the data and can thus be studied simultaneously with the waves on the film surface. Several scenarios of bubble entrapment and collapse were identified and discussed. The dynamics of entrapped bubbles was studied quantitatively using an automatic processing algorithm, confirming and elucidating the results of qualitative observations. The effect of the flow parameters on the bubbles concentration, velocity and size distributions was studied separately for the bubbles inside the disturbance waves and inside the thin base film between the dis- turbance waves. It was shown that the bubbles are mostly created due to oblique impacts of droplets at the base film and are accumulated by the disturbance waves. A small number of bubbles of larger size are created in front of disturbance waves and remain inside the disturbance waves. The velocity of the bubbles is affected by the velocity of the surrounding liquid. Using the bubbles as tracers, a profile of longitudinal liquid velocity was constructed and a noticeable increase of wall shear under the rear slopes of disturbance waves was found

Comparison of disturbance wave parameters with flow orientation in vertical annular gas-liquid flows in a small pipe

The interfacial wave structure of the liquid film in both upward and downward annular gas-liquid flows in an 11.7 mm pipe were investigated using the Brightness Based Laser Induced Fluorescence technique (BBLIF). Film thickness measurements were carried out with high spatial and temporal resolution between 330 and 430 mm from the inlet, where the properties of disturbance waves are almost stabilised. Using a tracking algorithm to detect disturbance waves, a full characterisation in terms of their velocity, frequency, longitudinal size and spacing was carried out. Direct comparison between both flow orientations while testing the same flow conditions shows that although the flow orientation does not affect the velocity of disturbance waves, the fraction of film surface occupied by the disturbance waves is smaller in upwards flow. Thus, more liquid travels in the base film in upwards flow, which is consistent with the base film thickness measurements. These observations, together with qualitatively different behaviour of ripple wave velocity in upwards and downwards flows, studied using 2D Fourier analysis, indicate that the role of gravity is much more important on the base film than on disturbance waves. This supposedly occurs due to a local decrease in the interfacial shear stress on the base film surface because of the resistance of the disturbance waves to the gas stream in upward flow

Clinical heterogeneity associated with KCNA1 mutations include cataplexy and nonataxic presentations

Mutations in the KCNA1 gene are known to cause episodic ataxia/myokymia syndrome type 1 (EA1). Here, we describe two families with unique presentations who were enrolled in an IRB-approved study, extensively phenotyped, and whole exome sequencing (WES) performed. Family 1 had a diagnosis of isolated cataplexy triggered by sudden physical exertion in multiple affected individuals with heterogeneous neurological findings. All enrolled affected members carried a KCNA1 c.941T>C (p.I314T) mutation. Family 2 had an 8-year-old patient with muscle spasms with rigidity for whom WES revealed a previously reported heterozygous missense mutation in KCNA1 c.677C>G (p.T226R), confirming the diagnosis of EA1 without ataxia. WES identified variants in KCNA1 that explain both phenotypes expanding the phenotypic spectrum of diseases associated with mutations of this gene. KCNA1 mutations should be considered in patients of all ages with episodic neurological phenotypes, even when ataxia is not present. This is an example of the power of genomic approaches to identify pathogenic mutations in unsuspected genes responsible for heterogeneous diseases

Study of the impacts of droplets deposited from the gas core onto a gas-sheared liquid film

The results of an experimental study on droplet impactions in the flow of a gas-sheared liquid film are presented. In contrast to most similar studies, the impacting droplets were entrained from film surface by the gas stream. The measurements provide film thickness data, resolved in both longitudinal and transverse coordinates and in time together with the images of droplets above the interface and images of gas bubbles entrapped by liquid film. The parameters of impacting droplets were measured together with the local liquid film thickness. Two main scenarios of droplet-film interaction, based on type of film perturbation, are identified; the parameter identifying which scenario occurs is identified as the angle of impingement. At large angles an asymmetric crater appears on film surface; at shallow angles a long, narrow furrow appears. The most significant difference between the two scenarios is related to possible impact outcome: craters may lead to creation secondary droplets, whereas furrows are accompanied by entrapment of gas bubbles into the liquid film. In addition, occurrence of partial survival of impacting droplet is reported

A study of droplet impact on static films using the BB-LIF technique

This paper presents results of single droplet impacts on films of different height taken using the Brightness Based Laser Induced Fluorescence technique (BB-LIF). The dynamics of drop impingement such as the shape of the cavity, residual film thickness are investigated and analysed with a time-resolution of 0.1 ms and spatial resolution of 70 um. Additionally a variation of the BB-LIF technique is used to investigate the change in profile of the droplet liquid during the inertial self-similar regime. The results of the analysis show that present models predicting initial development of the cavity show good agreement. Suggested amendments for some of the constants for cavity width and residual film thickness are proposed based on the film thickness, that fit better with published data. The development of the profile of the droplet liquid demonstrates that for thin liquid films, the droplet liquid behavior with strong similarity to droplet impact on dry solid surfaces. It is noted that for some of the measured parameters, the use of the film height as the lengthscale gives a better fit

Incomplete inhibition of phosphorylation of 4E-BP1 as a mechanism of primary resistance to ATP-competitive mTOR inhibitors

The mammalian target of rapamycin (mTOR) regulates cell growth by integrating nutrient and growth factor signaling and is strongly implicated in cancer. But mTOR is not an oncogene, and which tumors will be resistant or sensitive to new ATP-competitive mTOR inhibitors now in clinical trials remains unknown. We screened a panel of over 600 human cancer cell lines to identify markers of resistance and sensitivity to the mTOR inhibitor PP242. RAS and PIK3CA mutations were the most significant genetic markers for resistance and sensitivity to PP242, respectively; colon origin was the most significant marker for resistance based on tissue type. Among colon cancer cell lines, those with KRAS mutations were most resistant to PP242, while those without KRAS mutations most sensitive. Surprisingly, cell lines with co-mutation of PIK3CA and KRAS had intermediate sensitivity. Immunoblot analysis of the signaling targets downstream of mTOR revealed that the degree of cellular growth inhibition induced by PP242 was correlated with inhibition of phosphorylation of the translational repressor 4E-BP1, but not ribosomal protein S6. In a tumor growth inhibition trial of PP242 in patient-derived colon cancer xenografts, resistance to PP242 induced inhibition of 4E-BP1 phosphorylation and xenograft growth was again observed in KRAS mutant tumors without PIK3CA co-mutation, compared to KRAS WT controls. We show that, in the absence of PIK3CA co-mutation, KRAS mutations are associated with resistance to PP242 and that this is specifically linked to changes in the level of phosphorylation of 4E-BP1