Recent Submissions

  • Large eddy simulation of the flow past a circular cylinder at super-critical Reynolds numbers

    Ahmadi, Mohammad; Yang, Zhiyin; University of Derby (ASME, 2020-09)
    Turbulent flow past a circular cylinder at super-critical Reynolds numbers is simulated using large eddy simulation in this study. A novel combination of O- and H-grid structures is used to reduce mesh cells and, in turn, the computational cost. To investigate the influence of sub-grid scale (SGS) models on the accuracy of simulations, four different SGS models are applied to simulate the flow. In this study, the effect of mesh resolution near the wall on the accuracy of results is also evaluated by applying different y+ values at the wall. The results show that due to the complexity of the flow around the cylinder particularly at high Reynolds numbers, using very high resolution mesh near the cylinder wall, can not guarantee the accuracy of results and other parameters such as mesh resolutions at the top and bottom shear layers and the wake shortly behind the cylinder should be considered appropriately.
  • Assessment of drag reduction devices mounted on a simplified tractor-trailer truck model

    Charles, Terrance; Yang, Zhiyin; Lu, Yiling; Coventry University; University of Derby (Shahid Chamran University of Ahvaz, 2020-09-14)
    Aerodynamic drag reduction of tractor-trailer combination trucks is critically important to improve their fuel consumption which consequently results in lower emissions. One practical method to reduce aerodynamic drag of a truck is by mounting drag reduction devices on the truck. This paper presents a numerical study of turbulent flow over a simplified tractortrailer truck with different drag reduction devices mounted on the truck using the Reynolds Averaged Navier-Stokes (RANS) approach to assess the effectiveness of those devices in drag reduction around the tractor-trailer gap region. Three cases with different drag reduction devices have been studied and significant drag reduction (above 30%) has been achieved for all three cases. Detailed analysis of the flow field has been carried out to understand drag reduction mechanisms, and it shows that no matter what drag reduction devices are deployed the drag reduction is mainly due to the reduced pressure on the front face of the trailer, and a small proportion of the drag reduction is due to the reduced turbulent kinetic energy in the gap region.
  • Optimal design of cold roll formed steel channel sections under bending considering both geometry and cold work effects

    Qadir, Sangar; Nguyen, Van Bac; Hajirasouliha, Iman; Cartwright, Brian; English, Martin; University of Derby; University of Sheffield; Hadley Industries plc (Elsevier, 2020-09-17)
    Optimal design of a structural member is a design process of selecting alternative forms to obtain its maximum strength while maintaining the same weight, leading to the most economical and efficient structure. Amongst steel structures, cold rolled steel ones can effectively gain this requirement as they are thin-walled structures that offer the high ratio of strength over weight. However, the design is very challenging as these members are prone to buckling and failure at low loads. In this paper, the buckling and ultimate strength of cold rolled channel sections was studied using numerical modelling. In order to improve the section strength, the development of various alternative cold rolled formed sections included additional bends such as intermediate stiffeners. The section strength was optimised through a practical approach which altered the stiffener’s position and shape and searched for maximum buckling and ultimate strength under bending. In this approach, a nonlinear Finite Element model was first developed for an industrial channel beam subjected to four-point bending tests and this model was validated against experimental test data. The verified model was then used to conduct a parametric study in which the effects of a stiffener’s properties on the section strength including its position, shape, size and material properties by the cold work at bends were investigated in detail. Several different cold rolled channel sections having intermediate stiffeners at web and flanges with and without the cold work effect on material properties at the stiffener’s bends were considered for this investigation. In addition, a design method, the Direct Strength Method (DSM), was utilised to take into account the effects of a stiffener’s properties on the section strength and results were compared with the Finite Element modelling results. It was found that some significant improvements were obtained for the section strength of the optimised sections in comparison to the original sections. An optimal shape for the channel section with maximum ultimate strength in distortional buckling could be obtained with both the stiffeners’ position, shape, size and quantity, and the cold work effect. The cold work effect was found most significant in the cases of changing the width of the web stiffeners and the position of the flange stiffeners. It also revealed that, the currently available DSM beam design curve for distortional buckling provided good agreement in predicting buckling load and ultimate strength capacity for most of the considered sections with and without the cold work effect included; however, the DSM provided overestimate results compared to the Finite Element model results in the sections with web intermediate stiffeners, in particular, when the tip of web intermediate stiffener moved away from the web-flange junction in the horizontal direction.
  • Comprehensive review of the recent advances in PV/T system with loop-pipe configuration and nanofluid

    Cui, Yuanlong; Zhu, Jie; Zoras, Stamatis; Zhang, Jizhe; University of Derby; University of Nottingham; Shandong University (Elsevier, 2020-08-24)
    Solar photovoltaic/thermal technology has been widely utilized in building service area as it generates thermal and electrical energy simultaneously. In order to improve the photovoltaic/thermal system performance, nanofluids are employed as the thermal fluid owing to its high thermal conductivity. This paper summarizes the state-of-the-art of the photovoltaic/thermal systems with different loop-pipe configurations (including heat pipe, vacuum tube, roll-bond, heat exchanger, micro-channel, U-tube, triangular tube and heat mat) and nanoparticles (including Copper-oxide, Aluminium-oxide, Silicon carbide, Tribute, Magnesium-oxide, Cerium-oxide, Tungsten-oxide, Titanium-oxide, Zirconia-oxide, Graphene and Carbon). The influences of the critical parameters like nanoparticle optical and thermal properties, volume fraction, mass flux and mass flow rates, on the photovoltaic/thermal system performance are for the optimum energy efficiency. Furthermore, the structure and manufacturing of solar cells, micro-thermometry analysis of solar cells and recycling process of photovoltaic panels are explored. At the end, the standpoints, recommendations and potential future development on the solar photovoltaic/thermal system with various configurations and nanofluids are deliberated to overcome the barriers and challenges for the practical application. This study demonstrates that the advanced photovoltaic/thermal configuration could improve the system energy efficiency approximately 15%–30% in comparison with the conventional type whereas the nanofluid is able to boost the efficiency around 10%–20% compared to that with traditional working fluid.
  • Computational analysis of turbulent flow over a bluff body with drag reduction devices

    Abikan, Adam; Yang, Zhiyin; Lu, Yiling; University of Derby (University of Ahvaz, 2020-08-23)
    Reducing aerodynamic drag of heavy trucks is crucially important for the reduction of fuel consumption and hence results in less air pollution. One way to reduce the aerodynamic drag is the deployment of drag reduction devices at the rear of trucks and this paper describes a numerical study of flow over a bluff body with rear drag devices using the Reynolds-Averaged-Navier-Stokes (RANS) approach to investigate the drag reduction mechanisms and also to assess accuracy of the RANS approach for this kind of flow. Four cases, a baseline case without any drag reduction devices and three cases with different drag reduction devices, have been studied and the predicted mean and turbulent quantities agree well with the experimental data. Drag reduction varies hugely from a few percent in one case to more than 40% in another case and detailed analysis of flow fields has been carried out to understand such a difference and to elucidate the drag reduction mechanism, which ultimately can lead to better design of future drag reduction devices.
  • Variation in Rayleigh wave ellipticity as a possible indicator of earthflow mobility: a case study of Sobradinho landslide compared with pile load testing

    Hussain, Yawar; Cardenas-Soto, Martin; Moreira, César; Rodriguez-Rebolledo, Juan; Hamza, Omar; Prado, Renato; Martinez-Carvajal, Hernan; Dou, Jie; Clemson University (USA); Universidad Nacional Autónoma de México; et al. (Universidad Nacional de Colombia, 2020-04-01)
    Rainfall-induced landslides pose a significant risk to communities and infrastructures. To improve the prediction of such events, it is imperative to adequately investigate the rainfall-dependent dynamics (leading to fluidization) and any associated internal sliding along shear planes within clayey slopes. Therefore, the present study adopted ambient noise analysis based on the Horizontal to Vertical Spectral Ratio (HVSR) method, to measure the seasonal variation of Rayleigh wave ellipticity as an indicator for the internal deformation and transition in the material state. The methodology was applied to an existing landslide, where variations in soil stiffness and internal sliding were expected to occur in response to rainfall. To improve the interpretation of the HVSR results (and hence the prediction of landslide’ reactivation by rainfall), HVSR measurements were also conducted on a field-scale pile load test. The pile test allowed a comparison of the seismic data generated by the soil movement along shear planes. The HVSR curves of this field test showed two frequency peaks with no changes in the resonance. In comparison with the data obtained from the landslide, the resultant HVSR curves showed three frequency patterns: ubiquitous (2Hz), landslide (4-8Hz), and flat (no peak). However, the HVSR curves did not show any response to the expected seasonally induced variations in the landslide mass because of the relatively short data acquisition. Nevertheless, time-lapse HVSR is a promising technique that can complement other geophysical methods for improving landslide monitoring.
  • Progress in utilisation of waste cooking oil for sustainable biodiesel and biojet fuel production

    Goh, Brandon Han Hoe; Chong, Cheng Tung; Ge, Yu Qi; Ong, Hwai Chyuan; Ng, Jo-Han; Bo, Tian; Ashokkumar, Veeramuthu; Lim, Steven; Seljak, Tine; Józsa, Viktor; et al. (Elsevier, 2020-08-13)
    The increase in human consumption of plant and animal oils has led to the rise in waste cooking oil (WCO) production. Instead of disposing the used cooking oil as waste, recent technological advance has enabled the use of WCO as a sustainable feedstock for biofuels production, thereby maximising the value of biowastes via energy recovery while concomitantly solving the disposal issue. The current regulatory frameworks for WCO collection and recycling practices imposed by major WCO producing countries are reviewed, followed by the overview of the progress in biodiesel conversion techniques, along with novel methods to improve the feasibility for upscaling. The factors which influence the efficiency of the reactions such as properties of feedstock, heterogenous catalytic processes, cost effectiveness and selectivity of reaction product are discussed. Ultrasonic-assisted transesterification is found to be the least energy intensive method for producing biodiesel. The production of bio-jet fuels from WCO, while scarce, provide diversity in waste utilisation if problems such as carbon chain length, requirements of bio-jet fuel properties, extreme reaction conditions and effectiveness of selected catalyst-support system can be solved. Technoeconomic studies revealed that WCO biofuels is financially viable with benefit of mitigating carbon emissions, provided that the price gap between the produced fuel and commercial fuels, sufficient supply of WCO and variation in the oil properties are addressed. This review shows that WCO is a biowaste with high potential for advanced transportation fuel production for ground and aviation industries. The advancement in fuel production technology and relevant policies would accelerate the application of sustainable WCO biofuels.
  • The potential use of geophysical methods to identify cavities, sinkholes and pathways for water infiltration

    Hussain, Yawar; Uagoda, Rogerio; Borges, Welitom; Nunes, José; Hamza, Omar; Condori, Cristobal; Aslam, Khurram; Dou, Jie; Cárdenas-Soto, Martín; Clemson University (USA); et al. (MDPI AG, 2020-08-14)
    The use of geophysical characterization of karst systems can provide an economical and non-invasive alternative for extracting information about cavities, sinkholes, pathways for water infiltration as well as the degree of karstification of underlying carbonate rocks. In the present study, three geophysical techniques, namely, Ground Penetrating Radar (GPR), Electrical Resistivity Tomography (ERT) and Very Low Frequency Electromagnetic (VLFEM) methods were applied at three different locations in relation to fluvial karst, which is listed as an environmentally sensitive area in Rio Vermelho, Mambaí, Goiás, Brazil. In the data acquisition phase, the GPR, direct-current (DC) resistivity and VLFEM profiles were obtained at the three locations in the area. Data were analyzed using commonly adopted processing workflows. The GPR results showed a well-defined lithology of the site based on the amplitude of the signal and radar typologies. On the other hand, the inverted resistivity cross-sections showed a three-layered stratigraphy, pathways of water infiltration and the weathered structures in carbonate (Bambui group). The interpretation of VLFEM as contours of current density resulted from Fraser and Karous–Hjelt filters, indicated the presence of conductive structures (high apparent current density) that might be linked to the weathered carbonate and other conductive and resistive anomalies associated with the water-filled and dry cavities (cave), respectively. The results encourage the integrated application of geophysical techniques such as the reconnaissance for further detailed characterization of the karst areas.
  • A review of in-situ grown nanocomposite coatings for titanium alloy implants

    Gunputh, Urvashi Fowdar; Le, Huirong; Pawlik, Marzena; University of Derby (MDPI AG, 2020-04-21)
    Composite coatings are commonly applied to medical metal implants in order to improve biocompatibility and/or bioactivity. In this context, two types of titanium-based composite coatings have been reviewed as biocompatible and anti-bacterial coatings. The different composites can be synthesised on the surface of titanium using various methods, which have their own advantages and disadvantages. Moving with the smart and nanotechnology, multifunctional nanocomposite coatings have been introduced on implants and scaffolds for tissue engineering with the aim of providing more than one properties when required. In this context, titanium dioxide (TiO2) nanotubes have been shown to enhance the properties of titanium-based implants as part of nanocomposite coatings.
  • Performance comparison of resin-infused thermoplastic and thermoset 3D fabric composites under impact loading

    Choudhry, Rizwan Saeed; Shah, S. Z. H.; Megat-Yusoff, P.S.M.; Karuppanan, S.; Ahmad, F.; Sajid, Z.; Gerard, P.; Sharp, K.; Universiti Teknologi PETRONAS, Malaysia; University of Derby (Elsevier, 2020-07-29)
    In this paper, the impact performance of a novel resin-infused acrylic thermoplastic matrix-based 3D glass fabric composite (3D-FRC) has been evaluated and compared with thermoset based 3D-FRC under single as well as recurring strike low velocity impact (LVI) events. The single impact tests revealed that the thermoplastic-based 3D-FRC exhibits up to 45% reduced damage area and can have up to 20% higher impact load-bearing capacity (peak force). The damage mode characterization showed that damage transition energy required for micro to macro damage transition is 27% higher, and back face damage extension is up to 3 times less for thermoplastic-based 3D-FRC. Meanwhile, the recurring strike impact test highlights that the thermoplastic-based 3D-FRC experiences a 50% less damaged area, better structural integrity, and survived more strikes. The comparison of single and repeated LVI tests have also allowed us to present a design criterion for estimating the safe number of repeated LVI events for a given impact energy. The superior impact resistance of thermoplastic-based 3D-FRC is attributed to their higher interlaminar fracture toughness, a tougher fiber-matrix interface, matrix ductility, and unique failure mechanism of yarn straining, which is not present in thermoset composites.
  • Rutting resistance of asphalt pavement mixes by Finite Element modelling and optimisation

    Phuong Ngo, Chau; Nguyen, Van Bac; Nguyen, Thanh Phong; Bay Pham, Ngoc; Le, Van Phuc; Hung Nguyen, Van; University of Transport and Communications, Campus in Ho Chi Minh City, Vietnam; University of Derby (Bilingual Publishing Co., 2020-01-14)
    Asphalt pavement rutting is a major safety concern and is one of the main distress modes of asphalt pavement. Research into asphalt pavement mixes that provide strong resistance for rutting is considered of great significance as it can help provide extended pavement life and significant cost savings in pavement maintenance and rehabilitation. The objectives of this study are to develop numerical models to investigate the rutting of asphalt concrete pavements and to find optimal design of asphalt pavement mix for rutting resistance. Three-dimensional Finite Element models were first developed to simulate both the axial compression and wheel track testing in which a visco-elastic-plastic material model was used to predict the rutting of the asphalt concrete pavements. A strain hardening creep model with the material parameters developed from experimental testing was employed to model the time-dependent characteristics of the asphalt concrete pavements. The results were validated against the previous experimental wheel track test results of different pavement mixes. Finally, optimisation techniques using the Design Of Experiments method were applied to the simulation rutting results by varying creep parameters to identify their effects on rutting resistance in order to obtain an optimal asphalt pavements mixes. The results of this paper clearly demonstrate an efficient and effective experimental-numerical method and tool set towards optimal design for asphalt concrete pavements for rutting resistance.
  • Experimental and numerical study on soot formation in laminar diffusion flames of biodiesels and methyl esters

    Tian, Bo; Anxiong, Liu; Chong, Cheng Tung; Fan, Luming; Ni, Shiyao; Jo-Han, Ng; Stelio, Rigopoulos; Kai, Luo; Hochgreb, Simone; University of Derby; et al. (Elsevier, 2020-08-05)
    Biodiesel and blends with petroleum diesel are promising renewable alternative fuels for engines. In the present study, the soot concentration generated from four biodiesels, two pure methyl esters, and their blends with petroleum diesel are measured in a series of fully pre-vapourised co-flow diffusion flames. The experimental measurements are conducted using planar laser induced-incandescence (LII) and laser extinction optical methods. The results show that the maximum local soot volume fractions of neat biodiesels are 24.4% - 41.2% of pure diesel, whereas the mean soot volume fraction of neat biodiesel cases was measured as 11.3% - 21.3% of pure diesel. The addition of biodiesel to diesel not only reduces the number of inception particles, but also inhibits their surface growth. The discretised population balance modelling of a complete set of soot processes is employed to compute the 2D soot volume fraction and size distribution across the tested flames. The results show that the model also demonstrates a reduction of both soot volume fraction and primary particle size by adding biodiesel fuels. However, it is not possible to clearly determine which factors are responsible for the reduction from the comparison alone. Moreover, analysis of the discrepancies between numerical and experimental results for diesel and low-blending cases offers an insight for the refinement of soot formation modelling of combustion with large-molecule fuels.
  • The impact of industry 4.0 on sustainability and the circular economy reporting requirements

    Takhar, Sukhraj; Liyanage, Kapila; University of Derby (Inderscience, 2020-06-18)
    The traditional linear economic system focuses on the mass production of products, using available resources, at the lowest possible cost. Sustainability recognises the impact of dwindling natural resources, as a result of mass production and directs us towards the use of more sustainable resources. The circular economy (CE) proposes the adoption of an open loop manufacturing system where products are designed using resources which enable products to be repaired, reused, repurposed and recycled. To analyse the impacts of sustainability and CE initiatives, accurate data needs to be collected. Industry 4.0 promotes interconnectivity, enabling real-time data collection, communication and data analytics. This paper contributes to existing literature by identifying a research gap on how sustainability and CE model data reporting needs may be met using Industry 4.0 technologies. Using a literature review and survey on real-world adoption, a set of reporting requirements for sustainability and CE models are identified. The conclusions provide an assessment of how Industry 4.0 may aid reporting needs.
  • Synthesis of single-walled carbon nanotubes in rich hydrogen/air flames

    Zhang, Cen; Tian, Bo; Chong, Cheng Tung; Ding, Boning; Fan, Luming; Chang, Xin; Simone, Hochgreb; University of Cambridge; University of Derby; Shanghai Jiao Tong University (Elsevier, 2020-06-27)
    We explore the production of single-walled carbon nanotubes (CNTs) in a stream surrounded by rich premixedlaminar H2/air flames using a feedstock containing ethanol and ferrocene. The as-produced nanomaterialswere characterised by Raman spectroscopy, transmission electron microscopy, scanning electron microscopyand X-ray diffraction. A formation window of equivalence ratios of 1.00–1.20 was identified, and single-walledCNT bundles with individual CNTs of an average diameter of 1 nm were observed. The formation of CNTswas accompanied by the production of highly crystalline Fe3O4nanoparticles of a size of 20–100 nm. Theinvestigation of the limiting factors for the CNT synthesis was carried out systematically, assisted by numericalmodelling. We conclude that the key factors affecting CNT synthesis are the surrounding flame temperatures and the concentration of carbon available for CNT nucleation.
  • Energy performance and life cycle cost assessments of a photovoltaic/thermal assisted heat pump system

    Cui, Yuanlong; Zhu, Jie; Zoras, Stamatis; Qiao, Yaning; Zhang, Xin; University of Derby; University of Nottingham; China University of Mining and Technology; Cranfield University (Elsevier, 2020-06-26)
    A photovoltaic/thermal module assisted heat pump system is investigated in this paper, which provides electrical and thermal energy for a domestic building. In-depth evaluation on the system energy production is conducted based on the finite difference method for a long-term operating period. The 25 years’ system life cycle cost is assessed via the Monte Carlo simulation under the Feed-in Tariff (FiT) and Renewable Heat Incentive schemes, the annual energy savings, income and payback period (PBP) are compared for the FiT and Smart Export Guarantee (SEG) schemes. The technical analysis results illustrate that the system is able to fulfil the building thermal and electrical energy demands from April to October and from May to August, respectively, and the extra electricity of 229.47 kWh is fed into the grid. The economic assessment results clarify that the system achieves a net present value (NPV) of £38,990 and has a PBP of 4.15 years. Meanwhile, the economic sensitive analyses reveal that the high discount rate reduces the system NPV whereas the high investment cost causes a long PBP to realize the positive NPV. Compared with the SEG scheme, the FiT is the most cost-effective method for renewable electricity generation and has the shortest PBP.
  • Numerical study of the coupling between the instantaneous blade loading/power of an axial wind turbine and upstream turbulence at high Reynolds numbers

    Ahmadi, Mohammad H.B.; Yang, Zhiyin; University of Derby (Elsevier BV, 2020-07-06)
    Little is known about how the range of scales in the approaching turbulent flow can interact dynamically with wind turbines and influence its ability to produce power. Here, a numerical study of a horizontal-axis wind turbine at different Reynolds numbers (corresponding to different tip speed ratios) has been conducted to investigate the instantaneous turbine response to upstream turbulence. A computational approach, combining large eddy simulation with actuator line modelling, is adopted. Comparison between Power Spectral Density (PSD) of the turbine thrust/power and PSD of the velocity at the rotor plane and one rotor diameter upstream of it confirms that there is a coupling between the instantaneous turbine thrust/power and the upstream turbulence (one diameter upstream of the turbine) for frequencies below a critical frequency. Furthermore, it has been shown for the first time, that PSD of the turbine thrust/power and the velocity PSD at the rotor plane are very similar, indicating that the instantaneous turbine thrust/power and the velocity at the rotor plane are coupled for all frequencies. This means that the PSD of velocity at the rotor plane or shortly behind it can provide interesting information for the instantaneous turbine loads that are very important for the turbine operational life.
  • Quantification of carbon particulates produced under open liquid pool and prevaporised flame conditions: Waste cooking oil biodiesel and diesel blends

    Chong, Cheng Tung; Tian, Bo; Jo-Han, Ng; Fan, Luming; Wong, Kang Yao; Hochgreb, Simone; Shanghai Jiao Tong University; University of Derby; University of Southampton Malaysia; University of Cambridge (Elsevier, 2020-03-13)
    The soot volume fraction (SVF) of waste cooking oil (WCO) biodiesel and blends was quantified and compared under the same total carbon flow rate via two experimental setups, namely prevaporised diffusion jet flames and pool flames using extinction calibrated laser induced-incandescence (LII). The spatial SVF distribution shows that for diesel-rich fuels, soot formation peaks near the flame and is convected downstream, whereas biodiesel flames show a more evenly distributed SVF at the flame center region. An increase in biodiesel fraction in diesel results in a reduced propensity for soot, as evident in both pool and vapour flames. Comparison of the radial profiles of SVF along the centerline shows broader SVF profiles for pool flames, reflecting the longer residence times for soot diffusion and growth compared to vapour flames, which reflected the lower mass flux for the pool burner. The total soot produced from pool flames was found to be higher than vapour flame by a factor of two for the same fuel mass consumption rate. WCO biodiesel exhibited the lowest total SVF value regardless of flame type owing to the combined effects of lack of aromatic compounds and fuel chemistry. The soot primary particle sizes produced by WCO biodiesel show lower mean diameter values by a factor of approximately 1.5 compared to diesel-produced soot. The pool flames produced carbon particulates of larger mean diameter by around 22% and 8% for diesel and WCO biodiesel, respectively, relative to the counterpart vapour flames, as a result of extended soot surface growth period.
  • Dual-fuel operation of biodiesel and natural gas in a model gas turbine combustor

    Chong, Cheng Tung; Chiong, Meng-Choung; Ng, Jo-Han; Tran, Manh-Vu; Medina, Agustin Valera; Józsa, Viktor; Tian, Bo; Shanghai Jiao Tong University; Meng-Choung Chiong; University of Southampton Malaysia; et al. (ACS Publications, 2020-02-17)
    The dual-fuel combustion characteristics of palm biodiesel/methyl esters (PME) and natural gas (NG) in a model gas turbine swirl flame burner are investigated at a thermal power of 9.3 kW. The PME is atomized into a spray, while the gaseous NG is premixed with the main bulk swirling air before entering the combustion chamber. The dual-fuel PME/NG flame structure is similar to the single-fuel PME, where the sooty flame brush is noticeably absent. The PME and PME/NG flames emit higher peak intensity of OH* and CH* radicals as compared to diesel at the same equivalence ratio. Dual-fuel operation results in lower NO but higher CO at ϕ = 0.9 as compared to pure diesel and PME spray flames. The higher CO emission level for dual-fuel is attributed to poor mixing and incomplete combustion as a result of reduced air flow. At a leaner operation of ϕ = 0.65, enhanced turbulence due to higher bulk air flow results in improved mixing, lowering the overall CO but increasing the NO emissions because of the more intense flame core. The study shows that optimization of the multiphase dual-fuel injection system is needed to achieve low emissions in a gas turbine combustor.
  • Development of a beam optimization method for absorption-based tomography

    Yu, Tao; Tian, Bo; Cai, Weiwei; Shanghai Jiao Tong University, Shanghai, China; University of Cambridge (The Optical Society, 2017-03-07)
    Absorption tomography is an imaging technique that has been used simultaneously to image multiple scalar parameters, such as temperature and species concentration for combustion diagnostics. Practical combustors, such as internal combustion engines and gas turbine engines, only allow limited optical access, and typically a few (ca. 20-40) beams are available to probe the domain of interest. With such limited spatial sampling, it is non-trivial to optimize beam arrangement for a faithful reconstruction. Previous efforts on beam optimization rely on either heuristic/empirical methods lacking rigorous mathematical derivation or were derived by assuming certain prior information in the tomographic inversion. This paper aims to develop an approach that is expected to be especially useful when prior information is not easily available or intended to be included in the inversion processes. We demonstrate that the orthogonality between rows of the weight matrix directly correlates with reconstruction fidelity and can be used as an effective predictor for beam optimization. A systematic comparison between our method and the existing ones in the literature suggests the validity of our method. We expect this method to be valuable for not only the absorption tomography but also other tomographic modalities.
  • Planar 2-color time-resolved laser-induced incandescence measurements of soot in a diffusion flame

    Tian, Bo; Zhang, C.; Gao, Y.; Hochgreb, S.; University of Cambridge (Taylor and Francis, 2017-09-22)
    Planar two-dimensional two-color time-resolved laser-induced incandescence (2D-2C-TiRe-LII) is employed to investigate soot formation in a standard ethylene laminar diffusion flame. The time resolution of the 2D LII signal is realized by shifting the delay time of ICCD cameras. The two-color configuration is applied to measure the peak temperature of soot particles immediately after the laser pulse rather than using the energy balance to compute . The Sauter mean diameter D32 and the corresponding distribution width parameter σ of the measured soot particles is extracted by using an error minimization method. The method shows that a range of possible geometry mean particle diameters and corresponding distribution width parameters are also possible solutions, and further information on realizable particle size distribution widths is necessary to narrow down the extracted diameter.

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