PhD, EngD, DM and MSc by research theses (Silsoe)

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Open Access
An adaptive grid algorithm for computational shock hydrodynamics
(Cranfield University, 1991-01) Quirk, J. J.; Roe, P. L.
During the development of computational methods that solve time dependent shock hydrodynamic problems, two underlying strategies have emerged that enable flow features to be resolved clearly. One, employ a numerical scheme of inherently high resolution, usually a second-order Godunov-type method. Two, locally refine the computational mesh in regions of interest. It has been demonstrated by Berger & Collela that a combination of both strategies is necessary if a solution of very high resolution is sought. The present study combines Roe's flux-difference splitting scheme with an adaptive mesh refinement algorithm developed from the ideas of Berger. The result being a general purpose scheme that can fully resolve complicated flows but which requires only modest computing power. The material in this thesis reflects three broad aims. First, to explain the methodology and intricacies of our scheme. Compared to non-adaptive methods our scheme is undeniably complicated, for it contains many elements which must be carefully co-ordinated. Second, to vindicate this complexity. To this end, computational results are presented which are comparable in resolution to Schlieren photographs, yet the calculations were performed on a small desktop workstation. Third, to give sufficient details of our implementation so as to allay the apprehensions of any person who might wish to code up the scheme.
Open Access
Advanced diffusion coatings for improved oxidation and corrosion performance
(Cranfield University, 2001-08) Amperiawan, G.; Nicholls, J. R.
Research to investigate advanced diffusion coatings for improved oxidation and hot corrosion resistance was conducted. The aim was to build on the performance of the standard aluminide on the nickel-base super alloy IN738LC. The main emphasis of this investigation was to examine the effects of adding small quantities of yttrium to the coating as well as to produce a platinum-modified aluminide diffusion coating which is accepted as the best industrial standard for diffusion aluminides at present. A pack diffusion process was used to produce the coatings in this current study. A standard aluminide coating was modified with a small YCI3 (0.5 Wt.%) addition to the pack, producing an aluminising-yttrising pack. In the platinum-modified altuninide coating process, a sample was coated with several microns of platinum using a sputtering technique prior to the aluminising process. The pack used in this platinum modified aluminide process was a standard aluminising pack. The performance of these modified coatings during oxidation and high temperature corrosion was evaluated. Promising results were obtained, which demonstrated that both platinum and yttrium modified aluminide coatings had beneficial effects on the oxidation performance of the coatings compared to the standard aluminide coating. However, they were found to work in different ways, to improve resistance to oxidation and hot corrosion resistance. The platinum modified aluminide extends the later stage of the coating life by reduces the amount of spall, whist yttrium modified aluminide reducing the amount of spall in the early stage of the coating life and increases the critical oxide thickness before the onset of spallation. From these results, the production of a combined platinum-yttrium modified aluminide coating would be expected to show improved oxidation and hot corrosion resistance throughout the life of the coating. This could be another direction for future work.
Open Access
Agricultural tractor powertrains: Fundamental characteristics and opportunities for intelligent control
(Cranfield University, 2005-07-08) Sayer, David; Scarlett, A. J.; Godwin, R. J.
The use of microprocessor-based control systems on agricultural tractors has eased operator burden by allowing changes to tractor and implement settings to be made with little physical effort. However, maintaining the optimum tractor-implement settings whilst encountering the variable nature of agricultural conditions still requires a high level of operator skill, partly due to the need to adjust individual sub-system controllers. CAN-bus communication between electronically controlled vehicle sub. systems provided a new opportunity to enhance vehicle powertrain operation, by intelligently integrating control of the sub-systems. The aim of the project was to develop ways to improve the operational characteristics of a tractor powertrain, by investigating system behaviour, and identifying opportunities for intelligent control. Market research was undertaken which highlighted power-split continuously variable transmissions as a credible alternative to powershift-type transmissions in specific specialist applications where the additional purchase price could be justified. However, there is little scientific evidence to suggest that there are significant improvements in overall vehicle performance to be gained through the use of a CVT tractor compared to a well operated powershift-type transmission. Improvements to gearshift quality and more intelligent use of the powertrain control features could ensure powershift-type transmissions remain competitive for the foreseeable future. A dynamic mathematical powertrain model was developed for a lOOkW, 16 speed semi-powershift transmission, four wheel drive tractor based on fundamental Newtonian principles. With the addition of implement models, this allowed accurate representation of the tractor-implement system and provided a platform to develop improved vehicle control strategies. Validation of the model with experimental data showed it was an accurate representation of the real system. The steady state and transient field performance of the tractor operating with a mouldboard plough, a power harrow and a laden trailer was determined for a number of tractor-implement configurations across a range of conditions. This provided a David Sayer, 2005 Cranfield University, Silsoe 11 large dataset for this vehicle for use in this, and other investigations. The level of powertrain loading for field experiments was found to be influenced by soil type, implement working width and depth as well as forward speed and engine speed. For the road investigation, the surface quality and terrain were major influencing factors on performance. It was found there was considerable variation in tractor response to the different gearshift types experienced in the semi-powershift transmission: the non-powershift changes being severe, particularly during downshifts; double-swap powershifts were markedly more severe than single-swap shifts. A unique investigation of the tractor driveline torque loss characteristics across the full operating spectrum using the axle dynamometer identified that the torque losses for this transmission are predominantly speed, rather than torque related. A mathematical model was developed to predict driveline torque losses from transmission output speed, flywheel torque and the number of power-transmitting gears in mesh. The axle dynamometer was also used to successfully replicate field loading patterns in real time. Throughout this investigation a number of undesirable powertrain characteristics were identified. Potential improvements to vehicle performance through the development of solutions to these characteristics have been made either through analysis of field data, experiments with the axle dynamometer, or using the developed mathematical model.
Open Access
Aircraft conceptual design decision through operational modelling
(Cranfield University, 2005) Harasani, W.; Smith, Howard
Aircraft manufacturing is not only a difficult business but also a very competitive one, the consequences of any drop in sales would cost billions, loss of jobs, and maybe an economical failure. Therefore, concentrating on just flight performance and adding new technologies just because they exit is not enough to win the airlines attention, especially the flow cost carriers. Manufactures must be able to convince operators that the application of a new design or technology will produce a favourable change in the bottom line of their balance sheets and not just a reduction in fuel burn. Aircraft designers must put more emphasis on what happens to the aircraft after it leaves the assembly line, through the designed life operation cycle of the aircraft with the airline customer, quality should be built in to the aircraft. Knowing what are the airline's concerns, how the aircraft with a given design behaves, and the issues that the airline has, is vital. Firstly, it is important to know what are the issues that the airline has, the costumer (airlines) needs are identified, and, since fleet planning is the top level decision making department in the airline in which a decision is made to buy one aircraft over the other, it is important to understand the process and the elements that are involved in fleet planning. So fleet planning was studied. Second different technologies for the design have been looked at and selected. Then the aircraft, airline, airport, and air traffic control are studied, as well as the interaction between them. A key element of the research is a simulation program DEBOS that has been built to see the impact of the different design technologies and concepts through the operation of a simulation fleet size of 23 aircraft. The Boeing777 aircraft has been chosen to be the base line of the study. Finally, it was found that a given technology with improved performance, or a new concept, would improve the aircraft attractiveness only if it has better life cycle behaviour characteristics.
Open Access
Aircraft parameter estimation by estimation - before - modelling technique
(Cranfield University, 1995-11) Hoff, J. C.; Cook, M. V.
The use of the estímation-before-modellíng (EBM) two step identification procedure for the determination of aircraft aerodynamic derivatives from flight test data is analysed and illustrated. In the first step of the identification procedure the usual Extended Kalman Filter (EKF) associated with the Modified Bryson-Frazíer (MBF) smoother is compared with a new alterative filtering and smoothing process. The new smoother is simpler and less computationally demanding than the MBF smoother. However, its main advantage is that it enables simultaneous data smoothing with state derivative estimation, thereby avoiding the need for a separate differentiation algorithm. The new smoother differentiator has an important feature that is the determination of the noise characteristics of the measurement signal under analysis prior to the smoothing process. This is done by variance matching between the theoretical and measured autocorrelation of the innovation process generated by a Kalman filter. The new technique is compared with the old one by determining the aerodynamic models for a EMB-312 Tucano dutch roll manoeuvre. It is demonstrated that the new smoother may be used to replace the MBF. Otherwise the new technique is used in the analysis of the Handley Page Jetstream-100 aircraft low speed controls free phugoid trying to identify the contribution of the power Variation observed during the phugoid to the stability of the oscillation. Finally the models obtained from the phugoid analysis are reprocessed using the Total Least Square regression and the results are compared with those from the ordinary Least Square formulation.
Open Access
Aluminide-based coatings for turbine blade internal cooling passages
(Cranfield University, 2004-10) Long , K.; Nicholls, J. R.
The development of aero-gas turbines is moving towards more efficient engines with higher pressure ratios and increased Turbine Entry Temperatures. This leads to increases in overall turbine blades temperatures which has resulted in the widescale development of turbine blades with film cooling and Thermal Barrier Coatings (TBCs) which reduce the metal temperature of the blade. The air used for film cooling is directed around the blade by internal passages within the blade, current engines are experiencing hot corrosion in areas of these internal passages, even with internal aluminide coatings. The trend for more efficient engines means that corrosion of the internal passages will become more common, coupled with the inability to inspect the internal passages of turbine blades in service, results in a requirement for an improved coating for the internal passages of turbine blades. The aim of this study was to develop a coating which provides improved corrosion and oxidation performance over a standard vapour aluminide on single crystal CMSX-4 turbine blades material. The coating needs to be compatible with the Rolls- Royce bond coat and the Rolls-Royce manufacturing strategy. The study investigated a number of additions which could be used to improve the performance of an aluminide coating. Silicon was selected as the optimum addition on the basis of performance and ease of deposition. The work then assessed the influence of various production parameters on the formation of a silicon-aluminide coating. It was possible to control the level of silicon deposited in the coating. Performance testing, using cyclic oxidation and salt recoat hot corrosion tests, of various silicon aluminides developed in this programme demonstrated at least a doubling in life compared with vapour aluminide coatings.
Open Access
Analysis of sweet corrosion profiles
(Cranfield University, 1990-05) Esfahani, A.; Strutt, J. E.
The sweet corrosion profiles of X-52 carbon steel in 0.l% NaCl at 30, 40, 50 and 60°C were analysed. The corrosion tests lasted for a period of one month. They were performed using a flow loop under a total gas pressure of 1 atm. containing carbon dioxide (99.95% & 100 vpm O2). The corrosion profiles were obtained by scanning the corroded surfaces with a stylus. The results were analysed and compared with linear polarisation resistance (LPR) data. lt has been found that the (LPR) data at 40°C, i the absence of significant pitting, progressively underestimated the actual metal loss values. It has been proposed that the above discrepancy is due to the occurrence of small scale localised corrosion. The above effect was found to be exaggerated at 60°C, where extensive pitting occurred. Attempts to find a correlation between the (LPR) measurements and the actual metal loss distributions were unsuccessful. Furthermore, although sudden increase of the instantaneous corrosion rates for passive samples appeared to signal the onset of localised attack, i the absence of prior knowledge of the relative spread of the localised corrosion, it was not possible to quantify the observed errors. The range of the metal loss distributions was found to increase with time. This was most notíceable at 60°C. The progress of localised corrosion therefore, appears to have extended the distributions towards the extreme values. It has been proposed that, in the absence of severe pitting, the sweet corrosion profiles can be approximated by the Weibull statistical function. For pitted samples, where the localised attack resulted i metal loss on different scales, the upper 10% of the values were also found to be approximated by the Weibull function. The Weibull function was used for predicting the progress of the metal loss values with time. The analysis of the top 10% values, for pitted surfaces at 60°C, however, suggested the occurrence of an accelerating rate of attack. The original model was therefore improved to provide a time dependent sweet corrosion model. It has been estimated that the corrosion rate at 60°C increases with time at intervals of approximately 8 days. The effect of methanol on the sweet corrosion of X-52 carbon steel in 1% NaCl was also studied under stagnant conditions at 4, 40 and 60°C. The partial pressure of carbon dioxide was maintained at 0.3 bar. lt has been found that the corrosion rate decreases with increasing methanol concentration. The data was used to develop a predictive model within the range of 10 to 60% vol. methanol.
Open Access
Application of a hydrological model in a data-poor tropical West African catchment: a case study of the Densu Basin of Ghana
(Cranfield University, 2005-11) Bekoe, Emmanuel Obeng; Holman, Ian P.
This thesis reports on the suitability of using a hydrological model to predict the impact of future catchment changes on the surface water resources of tropical West African catchments, as a basis for sustainable watershed management strategies. The economically-important but data-poor Densu Basin (2100km2) in Ghana is used as a case study. Prior to the identification of an appropriate model, a range of model selection criteria to achieve the research objectives were developed, which included minimum data requirements. Following a review of available models, the ACRU hydrological model was chosen using these selection criteria. As this is the first use of the ACRU model in the Tropics, a sensitivity analysis was performed to gain a better understanding of the correspondence between the data and the physical processes being modelled and to inform future data collection priorities. The most sensitive parameters identified were rainfall; soil water content at field capacity and monthly crop coefficients. The sensitive parameters were different from those previously identified for semi arid regions, thereby improving the wider understanding of the behaviour of the ACRU model in a new climatic region of Africa for future studies. Although the ACRU model performed well during calibration (e.g. Nash and Sutcliff Efficiency > 0.8), it performed poorly during the validation period (e.g. NSE < 0.5). Aggregation of the daily output to monthly averages improved the performance appraisal statistics to a level where the model is appropriate for longer term water management issues such as irrigation planning and water supply planning. However, the prediction of the hydrological consequences of future catchment changes using the model could not be performed due to the variable model performance. A detailed analysis of input data quality and model performance identified a number of contributory reasons which included the poor distribution of available data from rain gauges and evaporation stations, poor data management and problems with groundwater processes within ACRU. Recommendations to the Densu River Basin Management Board to address the main problem area of data quality include ensuring that all data (new as well as existing) is subject to QC/QA procedures, the development of data archiving / back-up systems, making historical data available to the wider hydrological community; and guidance on deriving model inputs from available data for future modellers. Finally recommendations on which areas need further study during future research using the ACRU model are given.
Open Access
Application of a vane-recessed turbular-passage casing treatment to a multistage axial-flow compressor
(Cranfield University, 2001-11) Akhlaghi, M; Elder, R. L.
The current study investigates a range of issues relating to the use of a vane-recessed tubular-passage casing treatment as a passive stall control technique in a multistage axial-flow compressor. The focus of the research was to determine whether such a treatment could delay the initiation of stall at lower mass flow rates as well as providing the most beneficial improvement in flow characteristics without sacrificing compressor efficiencies. Specific objectives of this study were to examine possible improvements or deterioration in the flow characteristics including stall margin, peak pressure rise coefficients and maximum efficiency in a multistage axial flow compressor. A casing treatment in addition to several spacer rings was developed from two initial designs and tested on the first stage of a low speed three-stage axial-flow compressor with a (0.7) hub to tip diameter ratio. The treatment configuration consisted of three parts: an outer casing ring, with a tubular shaped passage on the inside diameter, a set of 120 evenly spaced curved vanes, and a shroud or inner ring. The casing treatment was positioned following the inlet guide vanes upstream and partly covering the tip of the rotor blades. The main parts of the casing treatment including the recessed vanes in addition to some of the spacer rings were manufactured from high quality acrylic. Eight additional spacer rings of various shapes and geometry were added. The first ring held and partly covered the IGVs, in front of the casing treatment. The rotor tip exposure ratio was thought to have a significant impact on the effectiveness of the casing treatment. Therefore the other seven rings were used to provide the desired uncovered region of the rotor tip axial chord of about 10% in order to provide a range of exposures of (23.2%, 33.3%, 43.4%, 53.5%, 63.6%, 73.7%, and 83.8%). The results showed significant improvements in stall margin in all treated casing configurations along with insignificant efficiency sacrifices in some compressor builds. About (28.56%) of stall margin improvement in terms of corrected mass flow rate was achieved using a casing treatment with a (33.3%) rotor tip exposure. The compressor build with (0.535) rotor exposure ratios was the best configuration in terms of efficiency gain and loss characteristics. This build was able to provide the highest values of the maximum efficiencies in comparison with the performance achieved from the solid casing. An improvement of (1.81%) in the maximum efficiency in terms of the overall total-total pressure ratio, in association with a (22.54%) stall margin improvement in terms of the corrected mass flow rates were achieved by the application of this treatment configuration. The improvement in the peak pressure rise coefficients in terms of the overall total-total pressure ratio, obtained from this build was (2.33%). The compressor configuration using a casing treatment with a (0.636) rotor exposure ratio was the best build in terms of the pressure rise coefficients. This configuration was able to provide highest value of the peak pressure rise in comparison with the characteristics achieved from the datum build. An improvement of (2.65%) in the peak pressure rise coefficient in terms of the overall total-total pressure ratio, in association with a (22.49%) improvement in stall margin in terms of the corrected mass flow rates was achieved from this casing treatment build. The improvement in maximum efficiency in terms of the overall total-total pressure ratio, obtained from this build was (1.03%). The results suggest that the vane-recessed tubular-passage casing treatment designed as part of this investigation achieved the objectives, which were established for the research. In the majority of instances it not only produced gains in flow range, pressure rise coefficients and efficiencies, but also enabled the rotating stall, which developed at much lower mass flow rates in the compressor, to become progressive rather than abrupt.
Open Access
Application of ion exchange for ammonium removal from municipal wastewaters
(Cranfield University, 2007-01) Thornton, A.; Parsons, Simon
Traditional methods of ammonium removal from municipal wastewaters rely on naturally occurring biological processes, where ammonium is converted into less harmful substances before being released into the environment. These processes are extremely effective at nitrogen removal but are less responsive to shock loads, in which case they can fall short of achieving the required effluent quality. In recent years research has been conducted into the possibility of using ion exchange technology as a complementary process for the. removal of ammonium from wastewater streams. Much of the research has been concerned with the .performance of naturally occuring materials, zeolites, with much of the work being undertaken at laboratory scale using synthetic solutions. This study investigates the performance of the modified media, MesoLite, using real and synthetic solutions, at both laboratory and pilot scale, in the presence of competing cautions. Initial studies were performed under batch conditions to assess the effect of a number of parameters such as contact time, solution ammonium concentration and pH on the uptake of ammonium on to MesoLite. This was followed by a investigation into a number of design parameters under dynamic conditions, leading to a pilot scale examination of the potential of the process to be used for the application of removing ammonium from low concentration wastewater treatment works effluents. Subsequent experiments were performed pilot scale to investigate the benefit of using the ion exchange process for ammonium removal from high strength liquors arising from the sludge dewatering process. Results indicate that a range of parameters affects the performance of the media and optimum performance is observed at high ammonium concentrations with increased contact time at pH 6-7. Results also show that MesoLite was successful in removing ammonium from high concentration sludge liquors, giving a total capacity of 47-51 g + -1 + -1 NH4 N kg and a operational capacity of 27 36 g NH4 N kg . The treatment of low concentration effluents return a total capacity of 19 g NI-14+-N kg`1 and a operational capacity of 9.5 g NI-14+-N kg`1. However, this reduced capacity is offset by the significant increase run time, from 1.5 to 22 days, and a increase in the amount of liquid treated from 140 bed volumes to in excess of 6000 bed volumes.
Open Access
The application of land evaluation technique in the north-east of Libya
(Cranfield University, 2006-08-10T13:45:00Z) Nwer, Bashir Ahmad Bashir; Hallett, Stephen; Brewer, Timothy R.
Land evaluation is a prerequisite to achieving optimum utilisation of available land resources for agricultural production. The principal purpose of land evaluation is to predict the potential and the limitations of land for changing use. Food security is one of the most important issues of agriculture policy in Libya. The country aims to obtain self‐sufficiency for its in agricultural products which contribute largely to the diet of most of the population. Therefore, eighty per cent of water transferred from aquifer‐sourced in the south of the country to the north, is planned for agriculture development. Cereal crops such wheat, barley, maize and sorghum are given the highest priority. There is, therefore, a pressing need to develop an optimal land evaluation method to identify in which part of a region these selected crops could e grown favourably. The model should be developed in accordance with the priorities of the Libyan Government in developing a practical and applicable land evaluation system that can be used by the average computer user. The FAO Framework was selected to conduct the land suitability assessment. This selection was based upon extensive and critical review of land evaluation methodologies and an evaluation of the objectives for and of the data available for study area. The FAO framework is a set of guidelines rather than a classification system, and model used builds upon this.
Open Access
The application of metrics to the measurement of quality systems
(Cranfield University, 1995-01) Williamson, A.; Vella, A. D.
Quality system auditing has been a topic of much recent discussion but there has not been a commensurate amount of research on how the audit process can make more effective use of auditor time and improve the quality of their judgements. An approach certification bodies and their clients may adopt is to measure the quality system activities of the client, and use these measurements (or metrics) to improve their understand of the quality system. If these metrics were available to auditors, they could identify the strengths and weaknesses of the quality system and assist in deciding if the client complies with ISO 9000. This could make the audit process more cost-effective and focused. A detailed study of the current auditing process used by certification bodies, and a survey of auditors, identified the quality system activities that provide the most confidence that the company has a compliant quality system. The "quality loop" activities of internal audit/management review and corrective action were found to be both the most important activities in showing compliance and provide the basis of metrics that can inform the auditor about the state of health of these activities. Metrics capable of measuring the other quality system activities required by ISO 9000 are identified, and their effectiveness in monitoring the quality system is discussed. The research shows that metrics concerned with the quality loop can provide useful information to an auditor and can help them in reaching a judgement. It is also shown that the use of metrics is constrained by organisational and technical factors, such as the size of the organisation being measured and the correspondence between the activity being measured and the requirements of ISO 9000.
Open Access
Application of the ecosystem functions framework to community woodlands
(Cranfield University, 2007-02) Agbenyega, Olivia; Burgess, Paul J.; Cook, M. V.
The UK government provides financial incentives to land owners who promote community use of newly-planted woodlands. De Groot et al. (2002) have developed a framework for classifying ecosystem functions. This research applies this framework to identify and describe perceptions of the function, use and value of community woodlands in order to inform local management and government policy. The research was an exploratory and descriptive case study with an initial flexible and final fixed stage. A poplar wood (Pegnut Wood) and two mixed-broadleaf woodlands(Clapham Park Wood and Reynolds Wood), all planted in Bedfordshire between 1993 and 1998, provided the case studies. Data collection methods included semi-structured interviews, self-administered structured questionnaires, direct observation, modelling of tree data and review of secondary documents. In total 172 out of 400 local residents, 20 on-site visitors, and 8 other stakeholders (owners, government institutions and conservation groups) gave responses. The primary motivations of the owners for establishing the woods were production, information and habitat functions. However financial cost-benefit analyses indicated negative returns to owners without government grants. In the first set of interviews 43- 58% of the local respondents at each site described the selected woods and community woods as “very important”. There was a significant positive association between nearness to the woods and level of importance. Those who visited the woods placed greatest emphasis on the use of the woods for exercise and recreation (48-64%), and as a wildlife habitat (50-52%). Using the ecosystem function framework, local respondents at Pegnut Wood and Clapham Park Wood placed greatest value on habitat (29-39%) and information functions (33-38%) and lowest value on regulation (14-19%), production (5-8%) and negative functions (7-8%). Respondents at Reynolds Wood placed the greatest relative importance on negative functions (36%). Across the three sites, local respondents placed the greatest relative value on the use of the woodlands as a habitat for wild plants and animals (14%) and to provide landscape beauty (12%). A second set of interviews, focussed on the recreational use of the woodlands, showed that the main purpose for visiting the woods was walking (median frequency of once a month and duration of between 31-60 minutes). Fifteen out of 88 respondents indicated that they were willing to contribute to support the woods. Many of those not in favour felt such support was a government responsibility. Overall, owners, local residents, government and local conservation groups showed similar relative valuations of the different functions and uses of community woodlands, indicating that there was substantial scope for working together. The research showed that it was useful to apply the ecosystem functions framework to community woodlands. It provided a structure for analysing planting objectives and it encouraged a focus on indirect uses. Stakeholders recognised potential negative functions of the woodland, and it proved useful to include these in the framework. We note the challenges in recognising and placing a high value on the regulation function amongst the range of stakeholders. The framework also helped to identify synergies and tensions between stakeholders without the need for monetising values.
Open Access
Applications of volatile fingerprint sensor arrays for rapid detection of environmental contaminants
(Cranfield University, 2005-03) Canhoto, Olinda; Aldred, David; Magan, Naresh
The electronic nose (e-nose) technology has rapidly evolved in the past decade with a range of applications in the food industry, medical diagnosis, and recently environmental monitoring. This is the first time that this technology has been examined in detail for a range of specific environmental applications including: detection of low concentrations of bacterial, fungal and heavy metal contaminants in potable water; analyses of changes in the microbial activity of soil samples amended with heavy metals; and the detection of fungal contaminants in paper samples from library material. In some studies comparisons between different e-nose systems has also been carried out. The e-nose system based on a conducting polymer (CP) sensor array Bloodhound (BH114) was able to detect different bacterial species (Escherichia coli, Pseudomonas aeruginosa and Enterobacter aerogenes), initially inoculated in tap, reverse osmosis and bottled water with a concentration of 102 cells mL-1, after 24 hrs incubation. In the presence of low concentrations (0.5 ppm) of a mixture of heavy metal ions including cadmium, lead and zinc, the volatile pattern produced by the bacterial species was discriminated from that where no metal was added, probably due to a change in the microbial metabolism. The Bloodhound e-nose system was also used to detect fungal spores of Aspergillus fumigatus, Fusarium culmorum and a Penicillium species, inoculated in water samples. The initial concentrations were 102 – 105 spores mL-1. Good discrimination was observed between the control samples after 24 hrs incubation at 25oC. After 48 hrs incubation, it was possible to differentiate between the various spore concentrations present in water samples. Good reproducibility was achieved as results from different days were consistent and data could be pooled and combined for analysis. A comparative study was performed with three e-nose instruments, two of them had CP sensor arrays (Bloodhound (BH-114); Neotronics (eNOSE 4000), and the third was a metal oxide (MO) sensor-based system, the NST 3220. The experiments carried out with the CP based-systems showed similar results when analysing water samples contaminated with 104 and 102 bacterial cells mL-1 after 24 hrs incubation. Both CP and MO based e-nose systems could differentiate control water samples from those contaminated with both bacteria and fungal spores. GC-SPME analyses confirmed the results obtained with the e-nose system of metal ions and bacterial cells in water samples. At-line studies were performed with the MO array-based system (NST 3220), for the detection of contamination episodes. E. coli and P. aeruginosa cells were used as contamination agents for tap and reverse osmosis sterile water, in two concentration levels, 102 and 106 cells mL-1. The samples collected downstream in a simulated watercourse, were analysed by the e-nose over a period of 1-2 hrs. The results suggested the potential of this technique to monitor episodes of bacterial cells at a low concentration in water samples. Experiments performed in soil samples artificially and naturally contaminated with heavy metal ions were analysed with the MO-based e-nose system. Results indicated that for artificially contaminated soil samples, after 40 days incubation the control samples could be discriminated from those containing 3 and 100 ppm of metal ions. For naturally contaminated soils, the sensor array was only able to separate samples containing a high concentrations of metal ions. Headspace analysis of cellulose-based agar showed good discrimination between Aspergillus terreus, A. hollandicus and Eurotium chevallieri, after 20 hrs incubation at 25oC. An increase in the incubation period to 40 hrs resulted in better separation between the control and fungal treatments. In situ studies performed on paper samples suggested that the e-nose was able to discriminate between control samples and paper inoculated with 103 fungal spores mL-1. The substrate was a determinant factor in the headspace analysis of microbial species. It was shown that the same fungal species produced different volatile profiles according to the growth substrate.
Open Access
At-line testing of chlorophenol and chloroanisole contaminants in commercial wine production.
(Cranfield University, 2004-09) Nicholls, C. R.; Saini, S.; Setford, S.
The research described in this thesis concerns the development of at-line test procedures for the detection of trace levels of chlorophenols and chloroanisoles in wine and related materials. Competitive ELISA assays were developed and optimised for pentachlorophenol and pentachloroanisole to enable the detection of chlorophenols and chloroanisoles in the range 0.1 to 100ng/ml in purified sample extracts, using antibodies supplied by the French consortium partner, Diaclone, together with synthesised conjugate materials, based on the enzyme horseradish peroxidase. The cross reactivity of the assay towards chlorophenol and chloroanisole congeners in wine was investigated and the pentachlorophenol assay was selected as the most efficient antibody to detect and quantify both chlorophenol and chloroanisole congeners. The use of synthetic receptors based on molecularly imprinting technology was also investigated for pentachlorophenol and pentachloroanisole, and a new assay format (Displacement Imprinted Polymer Analysis (DIPRA)) was established to measure chlorophenols in contaminated materials at a concentration range of 0.1 to 50 Âµg/ml, based on the displacement of a reporter molecule rebound to the synthetic receptor sites. Two alternative reporter molecules were synthesised by linking a pentachlorophenol derivative (2,3,5,6-tetrachloro-4-hydroxy phenoxy acetic acid) to the enzyme horseradish peroxidase or 7-amino-4-methylcoumarin-3-acetyl hydrazide. Alternative hyphenated sample extraction and purification methods based on solid phase extraction, steam distillation and liquid/liquid partition were evaluated to enable the ELISA and DIPRA test methods to be employed using the limited facilities of a local winery laboratory. The application of the procedures to the analysis of sample types such as wine, corks and packaging materials was undertaken to investigate the suitability of the test methods for inclusion in quality control and incident analysis protocols.
Open Access
Automated off-line programming for Rapid Prototyping using Gas Metal Arc Welding
(Cranfield University, 1995-06) Ribeiro, A. F. M.; Norrish, J.; McMaster, R.
Rapid Prototyping is a recent CAD/CAM based manufacturing technique which produces prototypes of components in a fraction of the time normally required. This technique normally involves drawing the part as a 3 Dimensional solid model using a CAD program and then 'printing' it in 3 Dimensions. The raw material can be a photopolymer or thermoplastic which solidifies when in contact with light. Other materials are available although producing the final parts a 100% metal is not very usual. Some disadvantages of these techniques are: a) 100% metal prototypes cannot normally be made directly. b) only prototypes can be produced instead of the final component. c) machine size limits the size of the final component. d) very thin layers are deposited. This makes the build up more time consuming and mostly suitable to small components. The main objective of this work was to overcome these disadvantages by creating a new Rapid Prototyping technique using Robot Fusion Welding. In the pre-production phase, it is important to make a prototype not only for visualisation but also to test and assess it in its real function. Therefore, prototyping in resin a component which is going to be made in metal has no use for assessing purposes. This technique, besides making the prototype in metal can also be used as a production technique to make the real usable final component. It even allows the use of different metals along its structure in the welding filler wire is changed. This makes it possible to have different structural characteristics in the same component a required. None of the slicing algorithms developed for other Rapid Prototyping processes were applicable to this new technique and therefore a new slicing concept (and routine) was created specifically. I addition, an interface for off-line programming and quality documentation was evolved. The technique developed has been tested by fabricating several 'test' components and both the dimensional accuracy and component integrity have been evaluated and proved to be successful.
Open Access
Bioaugmentation for the improvement of nitrification in wastewater treatment
(Cranfield University, 1993-07) Stephenson, Dianne; Stephenson, Tom
The literature relating to nitrification in wastewater treatment and bioaugmentation as a method to enhance wastewater treatment processes is reviewed. The use of a commercially available bioaugmentation product (based on a Nitrosomonas culture), which claimed to enhance nitrification in biological wastewater treatment was investigated.The product was tested in full scale trials, in shake flask experiments and its efficacy modelled using a simple activated sludge simulation. At full scale trickling filter plants a bioaugmentation product designed to enhance BOO removal was also tested. This product increased BOO removal by up to 7% in the recovery period following low temperature. The Nitrosomonas culture improved percentage ammonia removal by nearly 10% in trickling filters even at low temperatures of 6.5°C. A maximum improvement of 20% occurred at one trickling filter site at higher temperatures. At activated sludge sites the Njtrosomonas culture improved the nitrifying ability of the activated sludge, as assessed by the laboratory standard method, and at one site noticeably improved percentage ammonia removal during periods of high dosing. At one site the maximum improvement was an increase of 22% in percentage ammonia removal during high dosing. However the operational parameters, loads, hydraulic retention time, mixed liquor suspended solids, sludge age and temperature had a great effect on nitrification. If better process control was applied at one of the works the plant would have had little trouble nitrifying i.e. lower loads, higher HRT, MLSS and sludge age during low temperatures. Sludge wastage regimes contributed greatly to the failure to nitrify. It was found that the activity of the Nitrosomonas culture increased with temperature and acclimatisation and decreased on inoculation into activated sludge. The product facilitated nitrification when inoculated into non-nitrifying activated sludge. Ammonia removal increased with size of inoculum. The simple dynamic model described showed the development of a Njtrosomonas population from inoculation with the Nitrosomonas culture. The model showed that the effectiveness of a bioaugmentation product in activated sludge would depend on the amount of nitrifiers returned to the aeration basin more than other operational factors. The model predicted full nitrification at one of the full scale sites within three days. Bioaugmentation did enhance nitrification at full scale works. However, dosage rates required for improvement meant that conventional methods such as better process control or retrofitting would be economically more feasible.
Open Access
The biogeochemical origins and plant-availability of potentially toxic elements in sediment from the Thames Estuary
(Cranfield University, 2005-08) Shand, Ishbel; Kirk, Guy
In this thesis I investigate the biogeochemical origins and plant availability of potentially toxic elements (PTEs) in sediments dredged from the Thames Estuary. The sediments were pumped from the Thames into silt lagoons on the Rainham Marshes between 1961 and the late 1970s. They are fine-textured and rich in organic matter. The results show that PTE concentrations in the sediments are strongly positively correlated with nitrogen concentrations, and are highly inter-correlated. It is known that this distribution pattern is restricted to ancient and modern sediments from near coastal environments, and hence a link with estuarine processes is suggested. Subsequent investigation showed that the dredgings came from the Thames maximum turbidity zone, and that the lagoons represent a chronological record of changes in sediment quality during a period when dissolved oxygen in the water column rapidly increased. Analysis of one 5 m core from a lagoon showed that there were concurrent substantial changes in the relative proportions of clay, silt and sand in the sediment A novel mechanism is proposed, whereby the textural changes and PTE/organic matter correlation result from mineral dissolution and re-precipitation within flocs in the water column of the maximum turbidity zone. This is mediated by microbial consortia, and is driven by the requirement for Fe(III) as a terminal electron acceptor by dissimilatory iron-reducing bacteria. Potentially toxic elements released from mineral carrier phases are subsequently complexed by various components of the organic fraction or incorporated into secondary minerals and evenly distributed throughout the sediment by tidal action. Published data from historical, geological, hydrological and microbiological science are presented in support of this hypothesis. Foliar concentrations of PTEs in plants grown in the sediments were lower than those predicted by current models, probably because of strong sorption of these elements on sediment solids.
Open Access
Biomass effects on membrane bioreactor operations
(Cranfield University, 2004-10) Germain, E. A. M.; Stephenson, Tom
Diverse operating parameters were investigated for their effects on biomass characteristics, membrane fouling and aeration efficiency in submerged membrane bioreactors (MBRS). The characteristics of the solid phase of the biomass were affected by the biomass state (unstabilised, stabilising and stabilised) and by the SRT and HRT, whereas the characteristics of the liquid phase appeared to be more dependent on inuent composition and strength. Under operating conditions at constant SRT and HRT, the biomass characteristics reached their stabilised state aer 1.0±0.3 SRT. The impact of membrane aeration, permeate flux and biomass characteristics was determined for biomass at unstabilised state and at stabilised state. A transitional permeate flux was observed between 16.5 and 22 l.m`2.h`l, below which no significant fouling was observed regardless of the permeate flux, membrane airflow velocity and biomass characteristics. Above transitional flux, membrane fouling increased and was affected by the permeate flux, the membrane aeration velocity and parameters either characterising the liquid or the solid phase of the biomass depending on the carbohydrate concentration of the liquid phase. A comparison of ne and coarse bubble aeration efficiency for biomass at unstabilised state and at several airflow rates established that ne bubble aeration was more efficient in tem of oxygen transfer rate, but led to similar values to coarse bubble aeration for ot-factor. The effects of airflow rate and biomass characteristics on oxygen transfer coefficient and ot-factor were determined for biomass coming from pilot and full scale submerged MBRS treating municipal and industrial wastewaters. Solids concentrations (correlated to viscosity), COD concentration of the liquid phase, carbohydrate concentration of the EPS and volumetric airflow rate were found to affect the aeration efficiency parameters. A transitional solids concentration existed around 15 g.L", above which low or no oxygen transfer occurred.
Open Access
carbonate scale formation and control
(Cranfield University, 2005-03) MacAdam, Jitka; Parsons, Simon
Scale formation in domestic appliances is a widespread problem in the UK. This project has focussed on calcium carbonate scale formation in electric showers. A literature survey identified that CaCO; deposition on heated surfaces could be controlled by chemical or non chemical methods, each with various degrees of effectiveness. One of the most effective control methods was the addition of chemicals, although this may not be the most suitable option for the domestic environment. So here the chemical inhibitors tested were used for a benchmark for all the other studies. Two laboratory tests were involved t allow u to study CaCO; precipitation and scale formation. The effect of chemical additives on CaCO; precipitation was investigated using a jar tester. The longest delay to precipitation was obtained by polyacrylic acid dosing, closely followed by zinc. To study CaCO; formation on a heated surface, a rapid scaling test was developed. This test was conducted at 42°C and 70°C to examine and compare a range of treatment options, including chemical dosing, electrolytic, magnetic and electronic water conditioning and low fouling surfaces. From the options examined, the most successful was electrolytic dosing of zinc/copper media with over 95% reduction in scaling at both temperatures. Further, the use of low fouling surfaces, such as Diamond - like carbon coating could also potentially be used in electric showers. Reduction in scaling achieved on this surface was on average 68%. Surface properties of the materials were analysed using an atomic force microscope and their relationship with the scaling behaviour of the surfaces examined. The scaling rates at both temperatures typically increased with increasing adhesion force but no clear relationship was found between the roughness of the surfaces and their scaling behaviour. The relationship between CaCO3 precipitation and scale formation in synthetic solution and natural hard water was also explored here. The induction period in natural hard water was 55 minutes longer and the scaling rate 40% lower than i synthetic hard solution of similar composition. In addition, two shower test rigs, one based at Cranfield University and the other in Attleborough were used in this study. These were used primarily to enable the compilation of background data on scale formation in electric showers, where it was found that the design of the unit has a significant influence on the scale formation. The test rig was also used t test the strategies identified during the laboratory phase of the work. It was found that electrolytic zinc dosing reduced scaling by up to 54%, depending on the shower unit design.

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