Gas turbine combustor with integrated ash removal for fine particulates

This paper examines the performance of a novel design of combustor for utilising variable calorific value fuel gases as produced by many biomass gasification processes. An integral ash removal system is incorporated into the combustor to reduce the need for subsequent hot gas or other cleanup systems. The combustor is of cyclonic design with tangential inlets for air, start-up fuel and gasification products. Flame stability for low calorific value gases can be enhanced via the use of ceramic/refractory lined sections if required, with the system operating under lean combustion at all times to minimise NOx. Pressure drop of the cyclonic system is minimised by the use of a tangential outlet, as are combustion instabilities, as large central recirculation zones are avoided and associated instabilities like the precessing vortex core. Ash removal from the system is important to minimise damage to turbine components. Two regions are used for particle removal. The first is the base of the unit of a conventional hopper design, and the other, a unique vortex collector pocket (VCP) carefully positioned by the tangential off-take to take advantage of the accelerating tangential flow into the off-take. This paper focuses on the use of CFD to optimise the combustion performance of the combustor run under different operating conditions as well as the removal of coarse and fine material from the flow

Energy from biomass and the use of small direct fired gas turbine systems

This paper discusses the context for the use of biomass for electricity generation in the UK and similar markets and evaluates the possibility of using cyclonic gasification coupled to small gas turbine systems. In the UK the Government has strongly pushed for a significant increase in the use of renewable energy for electricity generation with only very modest success, nearly 3% coming from this source at present, predominantly hydro and wind. Subsidy for the early tranches of these systems came from an elevated price for generated electricity, but since attempts at price convergence with that pertaining with conventional fossil fuel generation systems has occurred the number of biomass systems being constructed and their net generating capacity has not increased in line with other technologies. Although utilisation technologies exist, and are well proven technologically in Scandinavia, when translated to markets such as the UK, give generating costs which are not competitive with other forms of renewable energy. Problems have arisen with many systems, being predominantly due to fouling/slagging, the different nature of the fuels, and elevated moisture content. In this context this paper describes an EU sponsored programme of work to develop a simple cyclone gasifier and combustor which can produce a medium calorific fuel gas for materials such as sawdust, retain up to about 80% of the total ash/residues in the system, and fire simple, low cost gas turbines for power generation. The system is shown to have a very wide operating range and can handle sawdust with significant quantities of material up to 4mm in size, whilst tolerating significant variation in moisture content and capturing very significant quantities of the ash/particulate matter as well as volatile species

Identification of cell cycle-regulated Drosophila microtubule-associated proteins using quantitative mass spectrometry

The microtubule network is the central framework in multiple cellular processes. The microtubule array undergoes dramatic changes as cells progress through the cell cycle. In mitosis the interphase microtubule array is reorganised into the dynamic mitotic spindle which mediates chromosome segregation. This reorganisation is coordinated by microtubule associated proteins (MAPs). However, little is known about the cell cycle regulation of MAPs and how it plays a role in mitotic spindle formation. In this thesis, I describe the development of a method to determine the profiles and relative quantities of MAPs purified from mitotic and interphase Drosophila culture cells. This method utilises mass spectrometry combined with stable isotope labelling by amino acids in cell culture (SILAC) for protein quantification. This study identified MAPs whose association with microtubules increased during mitosis and revealed a new mitotic MAP, which I have named NuMAP. NuMAP localises to the nucleus in interphase and to microtubules only in mitosis, covering the entire spindle. Truncation analysis identified two protein domains sufficient but not essential for nuclear localisation and one C-terminal domain vital for microtubule localisation. Interestingly, creation of an interphase cytoplasmic pool indicated that the interphase form of NuMAP has low affinity for microtubules, suggesting a cell cycle-related post-translational modification. A deletion mutant of the NuMAP gene was generated by P element excision and will be valuable to define the role of NuMAP in fly development

Experimental investigation of the effects of fuel diffusive injectors on premixed swirling flames

The demand for alternative fuels has increased significantly during the previous decades in order to reduce pollutants and increase the amount of energy that can be generated from non-fossil fuels. However, the use of new fuels faces many issues especially the problem of stability of operation which sometimes can cause severe damages to the system hardware. Thus the development of flexible combustion systems for gas turbines becomes urgent in order to achieve high reliability with these new sources of energy. Swirl stabilized combustion is the most widely spread deployed technology used to stabilize and control combustion in gas turbines and numerous other systems. However, the interaction of the swirling flows with the burner geometries is very complex and it has been proved that any change in the burner geometry can affect the flow field inside the combustion chamber, close to the burner mouth and downstream the combustion zone. Most burners are generally provided with a diffusive injector that centrally delivers well-known fuels allowing the stabilization of the system previous to entirely premixed conditions. Moreover, the injector anchors the central recirculation zone formed downstream of the nozzle. However, the use of injectors can also affect the stability limits of the system, especially the propagation of flashback through changes of shape of the shear layer since other structures such as the Combustion Induced Vortex Breakdown are suppressed due to the presence of this central body. However, the characterization of the flow and its impacts on the propagation of these and other flashback structures using different injectors has been briefly documented. Thus, this paper presents a series of experiments using a well-characterized tangential swirl burner to determine the impact of different central injector geometries on the flow field characteristics which directly affect the flow stagnation point downstream of the burner mouth and consequently the propagation of the Combustion Induced Vortex Breakdown. Results show how the use of various injectors and swirl numbers can impact on the flashback limits with a minimum outside diameter before which the Combustion Induced Vortex Breakdown is altered

Fuel quality impact analysis for practical implementation of corn COB gasification gas in conventional gas turbine power plants

Practical implementation of alternative fuels in gas turbine facilities is a challenging step towards cleaner and more responsible energy production. Despite numerous technical, economical and legal obstacles, possibilities for partial or complete substitution of fossil fuels are still subject of profound research. From all possible solutions, one with high acceptance is the symbiosis of existing gas turbine technologies and new ways of waste biomass energy utilization through firing or co – firing of biomass gasification gas. Therefore, the practical implementation of corn cob gasification gas with CO2 recirculation in gas turbines is analyzed in this paper. The followed methodology approaches this solution through two different scenarios each with 5 different cases. In the first scenario fuel mass flows are kept constant regardless of the fuel quality change consequence of the corn cob gas share, while in the second scenario fuel volume flows are assumed constant. Fuel quality refers to fuel composition which affects heat capacity, as well as physical and chemical characteristics of fuel. Impact of fuel composition changes on combustion product characteristics was analyzed using CHEMKIN PRO with GRI–Mech 3.0. Finally, fuel quality impacts on a gas turbine power plant performance are analyzed using a numerical model of a physical cycle that enables the simulation of a 3.9 MW experimentally correlated gas turbine. The results show that utilization of corn cob gasification gas is possible through co-firing with natural gas with acceptable values without modification of the fuel system or gas turbine

Experimental and theoretical investigation of the effect of rotating circular cylinder speed on the lift and drag forces

Flow past a circular cylinder is a problem for understanding flow around bluff bodies. This flow has been studied both experimentally and numerically of laminar infinite flow of viscous incompressible fluid around a rotating circular cylinder at Reynolds number 80,120,160 and dimensionless rotation rate, α , (ratio of cylinder surface speed to the free stream velocity) varying from 0 to 6 has been carried out. Navier–Stokes and continuity equations were solved numerically by using finite volume technique is conducted with ANSYS CFX 15 package program. High Speed Photography and LDV, present new experimental results for correlation purposes, captured the flow profile. Rotation can be used as a drag reduction technique. Comparison with previous studies showed good agreement

Computational Fluid Dynamic Studies of Vortex Amplifier Design for the Nuclear Industry—I. Steady-State Conditions

In this study the effects of changes to the geometry of a vortex amplifier are investigated using computational fluid dynamics (CFD) techniques, in the context of glovebox operations for the nuclear industry. These investigations were required because of anomalous behavior identified when, for operational reasons, a long-established vortex amplifier design was reduced in scale. The aims were (i) to simulate both the anomalous back-flow into the glovebox through the vortex amplifier supply ports, and the precessing vortex core in the amplifier outlet, then (ii) to determine which of the various simulated geometries would best alleviate the supply port back-flow anomaly. Various changes to the geometry of the vortex amplifier were proposed; smoke and air tests were then used to identify a subset of these geometries for subsequent simulation using CFD techniques. Having verified the mesh resolution was sufficient to reproduce the required effects, the code was then validated by comparing the results of the steady-state simulations with the experimental data. The problem is challenging in terms of the range of geometrical and dynamic scales encountered, with consequent impact on mesh quality and turbulence modeling. The anomalous nonaxisymmetric reverse flow in the supply ports of the vortex amplifier has been captured and the mixing in both the chamber and the precessing vortex core has also been successfully reproduced. Finally, by simulating changes to the supply ports that could not be reproduced experimentally at an equivalent cost, the geometry most likely to alleviate the back-flow anomaly has been identified

Coherent structure impacts on blowoff using various syngases

Swirl stabilized combustion is one of the most successful technologies for flame and nitrogen oxides control in gas turbines. However, complex fluid dynamics and lean conditions pose a problem for stabilization of the flame. The problem is even more acute when alternative fuels are used for flexible operation. Although there is active research on the topic, there are still various gaps in the understanding of how interaction of large coherent structures during the process affect flame stabilization and related phenomena. Thus, this paper approaches the phenomenon of lean premixed swirl combustion of CH4/H2/CO blends to understand the impacts of these fuels on flame blowoff. An atmospheric pressure generic swirl burner was operated at ambient inlet conditions. Different exhaust nozzles were used to alter the Central Recirculation Zone and observe the impacts caused by various fuel blends on the structure and the blowoff phenomenon. Methane content in the fuel was decreased from 50% to 10% (by volume) with the remaining amount split equally between carbon monoxide and hydrogen. Experimental trials were performed using Phase Locked PIV. The Central Recirculation Zone and its velocity profiles were measured and correlated providing details of the structure close to blowoff. The results show how the strength and size of the recirculation zone are highly influenced by the fuel blend, changing stability based on the carbon-hydrogen ratios. Nozzle effects on the shear flow and Re numbers were also observed. Modelling was carried out using the k-ω SST CFD model which provided more information about the impact of the CRZ and the flame nature close to blowoff limit. It was observed that the model under-predicts coherent structure interactions at high methane fuel content, with an over-prediction of pressure decay at low methane content when correlated to the experimental results. Thus, complex interactions between structures need to be included for adequate power prediction when using very fast/slow syngas blends under lean conditions

How online sexual health services could work; generating theory to support development.

BACKGROUND: Online sexual health services are an emerging area of service delivery. Theory of change critically analyses programmes by specifying planned inputs and articulating the causal pathways that link these to anticipated outcomes. It acknowledges the changing and contested nature of these relationships. METHODS: We developed two versions of a theory of change for an online sexual health service. The first articulated the theory presented in the original programme proposal and the second documented its development in the early stages of implementation through interviews with key programme stakeholders. RESULTS: The programme proposal described an autonomous and empowered user completing a sexual health check using a more convenient, accessible and discreet online service and a shift from clinic based to online care. The stakeholder interviews confirmed this and described new and more complex patterns of service use as the online service creates opportunities for providers to contact users outside of the traditional clinic visit and users move between online and clinic based care. They described new types of user/provider relationships which we categorised as: those influenced by an online retail culture; those influenced by health promotion outreach and surveillance and those acknowledging the need for supported access. CONCLUSIONS: This analysis of stakeholder views on the likely the impacts of online sexual health services suggests three areas for further thinking and research. 1. Co-development of clinic and online services to support complex patterns of service use. 2. Developing access to online services for those who could use them with support. 3. Understanding user experience of sexual health services as increasing user autonomy and choice in some situations; creating exclusion and a need for support in others and intrusiveness and a lack of control in still others. This work has influenced the evaluation of this programme which will focus on; mapping patterns of use to understand how users move between the online and clinic based services; barriers to use of online services among some populations and how to overcome these; understanding user perceptions of autonomy in relation to online services

Can Internet-Based Sexual Health Services Increase Diagnoses of Sexually Transmitted Infections (STI)? Protocol for a Randomized Evaluation of an Internet-Based STI Testing and Results Service.

BACKGROUND: Ensuring rapid access to high quality sexual health services is a key public health objective, both in the United Kingdom and internationally. Internet-based testing services for sexually transmitted infections (STIs) are considered to be a promising way to achieve this goal. This study will evaluate a nascent online STI testing and results service in South East London, delivered alongside standard face-to-face STI testing services. OBJECTIVE: The aim of this study is to establish whether an online testing and results services can (1) increase diagnoses of STIs and (2) increase uptake of STI testing, when delivered alongside standard face-to-face STI testing services. METHODS: This is a single-blind randomized controlled trial. We will recruit 3000 participants who meet the following eligibility criteria: 16-30 years of age, resident in the London boroughs of Lambeth and Southwark, having at least one sexual partner in the last 12 months, having access to the Internet and willing to take an STI test. People unable to provide informed consent and unable to read and understand English (the websites will be in English) will be excluded. Baseline data will be collected at enrolment. This includes participant contact details, demographic data (date of birth, gender, ethnicity, and sexual orientation), and sexual health behaviors (last STI test, service used at last STI test and number of sexual partners in the last 12 months). Once enrolled, participants will be randomly allocated either (1) to an online STI testing and results service (Sexual Health 24) offering postal self-administered STI kits for chlamydia, gonorrhoea, syphilis, and HIV; results via text message (short message service, SMS), except positive results for HIV, which will be delivered by phone; and direct referrals to local clinics for treatment or (2) to a conventional sexual health information website with signposting to local clinic-based sexual health services. Participants will be free to use any other interventions or services during the trial period. At 6 weeks from randomization we will collect self-reported follow-up data on service use, STI tests and results, treatment prescribed, and acceptability of STI testing services. We will also collect objective data from participating STI testing services on uptake of STI testing, STI diagnoses and treatment. We hypothesise that uptake of STI testing and STI diagnoses will be higher in the intervention arm. Our hypothesis is based on the assumption that the intervention is less time-consuming, more convenient, more private, and incur less stigma and embarrassment than face-to-face STI testing pathways. The primary outcome measure is diagnosis of any STI at 6 weeks from randomization and our co-primary outcome is completion of any STI test at 6 weeks from randomization. We define completion of a test, as samples returned, processed, and results delivered to the intervention and/or clinic settings. We will use risk ratios to calculate the effect of the intervention on our primary outcomes with 95% confidence intervals. All analyses will be based on the intention-to-treat (ITT) principle. RESULTS: This study is funded by Guy's and St Thomas' Charity and it has received ethical approval from NRES Committee London-Camberwell St Giles (Ref 14/LO/1477). Research and Development approval has been obtained from Kings College Hospital NHS Foundation Trust and Guy's and St Thomas' NHS Foundation Trust. Results are expected in June 2016. CONCLUSIONS: This study will provide evidence on the effectiveness of an online STI testing and results service in South East London. Our findings may also be generalizable to similar populations in the United Kingdom. TRIAL REGISTRATION: International Standard Randomized Controlled Trial Number (ISRCTN): 13354298; http://www.isrctn.com/ISRCTN13354298 (Archived by WebCite at http://www.webcitation.org/6d9xT2bPj)