7,320 research outputs found
Low speed axial compressor design and evaluation : High speed representation and endwall flow control studies
No full textThis Thesis reports the design, build and test of two sets of blading for the
Cranfield University low speed research compressor. The first of these was a datum low
speed design based on the fourth stage of the DERA high speed research compressor
C 147. The emphasis of this datum design was on the high-to-low speed transformation
process and the evaluation of such a process through comparing detailed flow
measurements from both compressors.
Area traverse measurements in both the stationary and rotating frame of reference
were taken at Cranfield along with overall performance, blade surface static pressure and
flow visualisation measurements. These compare favourably with traverse and
performance measurements taken on C147 before commencement of the PhD work.
They show that despite the compromises made during the transformation process, due to
both geometric and aerodynamic considerations, both the primary and secondary flow
features can be successfully reproduced in the low speed environment.
The aim of the second design was to improve on the performance of the datum
blading through the use of advanced '3D' design concepts such as lean and sweep. The
blading used nominally the same blade sections as the datum, and parametric studies
were conducted into various lean/sweep configurations to try to optimise the blade
performance. The final blade geometry also incorporated leading edge recambering
towards the fixed endwalls of both the rotor and stator. The '3D' blading demonstrated a
1.5% increase in efficiency (over the datum blading) at design flow rising to around 3%
at near stall along with an improvement in stall margin and pressure rise characteristic.
The design work was completed using the TRANSCode flow solver for both the
blade-to-blade solutions (used in the SI-S2 datum design calculation) and the fully 3D
solutions (for the advanced design and post datum design appraisal). The 3D solutions
gave a reasonable representation of the mid-span and main 3D flow features but failed to
model the corner and tip clearance flow accurately. An interesting feature of the low
speed flowfield was the circumferential variation in total pressure observed at exit from
all rotors for both designs. This was not present at high speed and represents one of the
main differences between the high and low speed flow. Unsteady modelling of mid-
height sections from the first stage indicate that part of this variation is due to the
potential interaction of the rotor with the downstream stator while the remainder is due
to the wake structure from the upstream stator convecting through the rotor passage.
Finally, the implications for a high speed design based on the success of the 3D low
speed design are considered
Authors' attitudes to, and awareness and use of, a university institutional repository.
No full textThis article reports the findings of an author study at Cranfield University. The study investigated authors' publishing behaviours, attitudes, concerns, and their awareness and use of their institutional repository (IR), Cranfield QUEprints. The findings suggest that despite a reasonable amount of advocacy many authors had not heard of QUEprints and were not aware of its purpose. Once explained, all authors saw at least one benefit to depositing a copy of their work to QUEprints, but many were unsure how to deposit, preferring to depend on the Library to do the work. The authors voiced few concerns or conditions regarding the inclusion of their work in QUEprints, but felt that it would be an extra, inconvenient step in their workload. This research led to the development of the Embed Project which is investigating how to embed the IR into the research process and thereby encourage more authors to deposit their work
Controllability of road vehicles at the limits of tyre adhesion
No full textThe research project 'Controllability of Road Vehicles at the Limits of Tyre Adhesion'
(CROVLA) was established to investigate how tyre and chassis properties contribute
to the handling characteristics and stability of vehicles operating at or near to the limit
condition. The project involved the Department of Transport, SP Tyres UK Limited,
Jaguar Cars and Cranfield University.
An extensive proving ground test program of typical limit handling tests provided
characteristic driver input and vehicle response data for a variety of vehicle
configurations. The test data analysis was based on the concept of correlation. Cross-
correlation coefficients and average response time delays were obtained for various
pairs of quantities, namely steering angle and torque for the input and yaw rate and
lateral acceleration for the response. The predictability of the vehicle response was
evaluated by the rate by which the correlation coefficients change with severity.
Analogous to the proving ground work, vehicle dynamics simulations were carried
out. Two programs were employed to study the steady state performance and the
transient limit handling behaviour.
The `Steady State Cornering Model' was used to confirm some basic suspension
design rules established for optimising the lateral adhesion of a suspension design.
The importance of controlling camber and vehicle jacking by an appropriate
suspension design was identified.
A detailed vehicle model was built-up using the simulation code AUTOSIM. After
validating the model against proving ground data, some parametric studies were
conducted to quantify the effects of suspension and tyre properties on the transient
limit response behaviour.
Proving ground and simulation results suggest that response time lags and cross-
correlation coefficients in combination with other handling parameters can be used as
objective quality measures. The results quantified to what extent tyre and chassis
modifications change the limit handling behaviour
Outcome predictors of co-operative R & D in Europe: organisational capabilities and cultures
No full textThis research investigates organisational capabilities and cultures of both partners as
potential explanatory factors of co-operative R&D projects outcomes.
Contributions to theory are (1) a justification for the existence of organisational
capabilities and 'world views', (2) a parsimonious typology of 'world views' and (3) a
method to measure organisational capabilities.
The survey covers 514 projects in the electronics industry, in Germany, France, the
United Kingdom and Finland. It obtains 120 full answers, each of which coupling
responses from a matched pair of project managers having co-operated on the same
R&D project. The survey refers to the organisation's capabilities, to those of the partner,
to its 'world view', and to project outcomes.
None of the traditional explanatory factors (geographic distance, difference in
nationality, size or legal status, strategic compatibility) has any significant influence on
any of the outcomes being studied (save one).
The explanatory factors introduced by the research (organisational capabilities and
'world views') have a significant influence on almost all outcomes being considered of
the co-operative R&D projects: attainment of concrete results, compliance with budget
and schedule, creation and transfer of knowledge, learning (modification of
capabilities). Cultural diversity, 'absorptive capacity', and teaching effects, selective
according to the capability in question, are evidenced. Commonalities between partners
are shown to be more important than distance. These results validate empirically
organisational capabilities and 'world views' as descriptors of inter-organisational
capabilities, and their operationalisation
Contributions to resource and environmental risk management
No full textThe rest of this DSc thesis is made up of published articles, as listed in the PDF attached to this record.This thesis charts a research journey through the disciplines of waste chemistry,
environmental risk assessment, policy analysis and corporate risk governance since
award of the candidate’s PhD in 1990. The insights gained present a distinctive
perspective on resource and environmental risk management - assessments of risk must
reflect our understanding of the science and evidence that supports them; and the
protection of public and environmental health, as an overarching motive, requires
greater prominence if the confidence of citizens in the Government and industry
handling of risk is to be secured.
Waste management is risk management and without an understanding of the
fundamental science and engineering of wastes and how they behave in the
environment, process technologies for their treatment can not be optimised, nor
regulatory oversight designed properly to protect public health and the environment.
The candidate’s research on the chemical characterisation of complex wastes and their
interaction with soils, waters and air, offers a more optimistic assessment of these
risks, at least within developed nations. This said, technical assessments of risk are
insufficient, in isolation, to secure the confidence of communities, investors, or the
wider citizenry. The motives and values of process operators and regulators that
oversee operations are as critical as technical demonstrations of environmental safety.
The recent contributions in this thesis examine organisational competencies in
preventative risk management, specifically within the water sector as it responds to
international calls for improved risk governance.
In concert, the candidate’s contributions and practical achievements in resource
and environmental risk management reported here represent a unique and substantive
body of problem-oriented research, directed at reconciling societal unease about waste
with our responsibilities for its safe management. Significant insights are made on the
reuse of hazardous and carbonaceous wastes, on the characterisation, fate and transport
of hydrocarbons in the environment, on the practice of environmental risk assessment
and the organisational competencies required to manage risk to the levels of
stakeholder confidence expected in the 21
st
century
Technology Transfer for Development: Insights from the Introduction of Low Cost Water Well Drilling Technology to Uganda
No full textThird World development theory and practice are changing so rapidly that it is
important to critically examine the fashions of today before they become history. This
thesis considers the development, transfer, early adoption and sustainable use of
technology, coupled with private sector participation in rural water supply provision.
Improving water supplies for rural communities is one of the key challenges
faced by development interventionists today. Lack of low cost, off the shelf technology
for local enterprise which can provide affordable shallow wells for rural communities is
one barrier to facilitating improvements.
This thesis is based on research undertaken in Uganda to develop and transfer
low cost water drilling technology in the context of decentralisation and privatisation
policies. An extensive range of literature has been drawn together into 16 principles
which guide technology transfer and development intervention. These principles are reexamined
in the light of analysis of first hand experiences of undertaking a technology
transfer project and interviews with stakeholders regarding their attitudes and
perceptions.
The research found that technology transfer is a cross-disciplinary and cross
cultural process in which the linkages between the technology, context, individuals,
organisations and beneficiaries need to be firmly established. Ugandan business and
local Government culture plays a major role in facilitating successful technology
uptake. Dealing with the risks associated with low cost groundwater technology is
fundamental for its wider adoption. The process of technology transfer is important,
particularly as high levels of stakeholder participation may compromise the delivery of
outputs, at least in the short term.
In terms of future challenges, this thesis shows that, culture, governance and
equity need to be closely examined in relation to private sector participation in rural
infrastructure provision. Private sector participation can conflict with community
participation. How to adequately support innovation in Sub-Saharan Africa while
harmonising development interventions is a challenge to the development community
Reducing deep soil compaction through strain modification under different wheel arrangements
No full textNew mechanisation methods associated with increasing loads have the potential to
cause undesirable deep compaction, which is difficult, expensive and in some cases
impossible to alleviate. Avoiding or reducing the risk of deep compaction seems to be
the most straightforward solution to compaction management.
Previous research indicates that some benefits can be achieved through interactions
between cultivation tines or other implements, in terms of the magnitude of forces and
the extent of soil deformation. Interaction within wheel arrangements could have
benefits for reducing deep soil compaction.
This study aimed to reduce the risk of deep soil deformation by locally modifying soil
conditions through interactions in order to increase soil resistance and hence load
support in the surface layers. To test the hypothesis, the research was based on soil
mechanics theories and failure mechanisms related to bearing capacity in order to
identify the major factors influencing load support and soil displacement. The nature
of soil failure patterns, interaction behaviour, soil deformation and load/sinkage
relationships were investigated under a wide range of dual and triple spaced
footings/wheels configurations. Small-scale tests using rectangular plates were firstly
conducted in a glass-sided tank. These initial tests were followed by larger-scale tests
in a soil bin and in the field under different soil conditions using actual wheels, spaced
and positioned as in the footing tests.
The results indicate that it is possible to reduce soil displacement at depth by
increasing load support in the soil surface layers through the interaction between
spaced wheel arrangements. It was shown that different interaction modes occurred
under dual configurations depending on the spacing between them. A locally
compacted zone was created between the wheels under dense interaction conditions,
increasing surface support. Surface support was increased further through a surcharging effect achieved by
placing a third footing/wheel between and higher than the side wheels (triple
arrangement). The central static interaction zone maximised the surface resistance
locally under these configurations. Although single wide section wheels such as Terra
tyres can tolerate higher loads at lower pressures, from a soil failure point of view,
this is usually associated with large active and passive failure zones inducing deeper
soil deformation. Triple spaced wheel arrangements with similar diameter wheels kept
soil displacements shallower whilst carrying a similar load to a single very wide
wheel with the same overall contact pressure. Reductions of up to 50% in the depth of
soil displacement were achieved with the triple arrangements for the same load. These
spaced arrangements can therefore be recommended as promising replacement for
single wide wheel under heavy machinery application in practical situations.
Benefits from the spaced arrangements are achieved in two ways: firstly by increasing
surface support through creating locally compacted zones and secondly by reducing
the size of active and passive failure zones causing shallower deformations.
Stony soils provide more surface support than stoneless soils and also non-uniform
soil with a denser layer at tillage depth can tolerate a greater load for a given sinkage
compared with uniform homogenous soil.
A mathematical model was developed to predict the vertical force under interacting
shallow footings and showed an acceptable level of agreement with the experimental
results. The model can be used to estimate the extent of the rupture distance of the
side passive planes to assist in identifying appropriate spacings and interaction modes
for spaced wheel arrangements
The experience of college undergraduates : degrees of transformation
No full textFollowing discussions with staff (7), successive and
progressive individual interviews were held throughout
their course with a small group of undergraduates (8)
taking a combined studies degree in a college of higher
education. Data were not confined to the course but took
a broad view, including their formal and informal lives
and the interplay between them. What the informants
faced and how they changed are all clearly illustrated.
The students' experiences are described and analysed
using a concept of transformation as achievement and
process. This concept is compared with other theories of
transformation in the educational literature. It is
argued that the students faced three phases of exposure:
social exposure, the need to be accepted in a new
setting; academic exposure, having to take seriously the
formal judgements of tutors and sustain the will to
study; and the 'final' phase of personal exposure, self-
awareness and letting go of dependence. Commitment,
routine and support were central to success.
Although the concept of education which informs it must
reflect the values of the writer, the argument is firmly
grounded in the data. To obtain an authentic portrayal,
the critical incident technique was deployed in an
extended way, through a form of questioning, which, it
is suggested, could itself have a part to play in the
tutorial role.
The study contributes to a fuller understanding of
students' college careers by offering an holistic
perspective and filling a gap in higher education
research. It was based on data from a few informants in
a small distinctive college at a particular time, but
its possible wider relevance for theory and practice are
discussed
Driver attitude and attribution : implications for accident prevention
No full textThis study involved self-completion questionnaire-based surveys in which a total of almost
1800 respondents took part. Attributional bias identified by previous research in relation to
drivers' causal attributions for road accidents (Preston & Harris, 1965; Clay, 1987) was
more fully explored with the aid of both objectively and subjectively culpable driver samples.
Banks et al (1977) demonstrated the utility of distinguishing drivers according to culpability
in relation to accident fatalaties. The current study examined the utility of distinguishing
subjectively culpable, non-culpable, and non-accident driver groups in relation to road
accidents with a variety of consequences, in relation to factors which may predispose drivers
to accident involvement. This study involved a large sample of drivers who were
representative of the general population of licenced drivers in Britain, and specifically
focussed samples which allowed the influence of objective and subjective culpability to be
ascertained, while a relatively small cross-cultural survey allowed a focus on young drivers
(up to 25 years), involving Victorian (Australian) licenced drivers and a sub-sample of young
British drivers drawn from the main British sample.
The main objectives of the current study were to evaluate drivers' awareness of their potential
for active accident avoidance, exploring attribution issues raised by previous research and
examining factors which may contribute to road accidents in relation to self-reported accident
involvement and culpability and their implications for accident prevention.
The main findings were that drivers seemed to have a tendency to attribute more
responsibility to "other drivers" than to themselves for accidents in which they had been
involved, and to consider that such other drivers had more scope for accident avoidance than
they did themselves. Such tendencies, although very considerably reduced, were not
eradicated within the driver group deemed culpable by traffic police investigative teams.
These findings were broadly consistent with those of Clay (1987) and Preston & Harris
(1965), suggesting a lack of awareness of personal influence on accident occurrence, at least
to some degree, with implications for accident prevention, the quality of social interaction in
the driving environment (Knapper & Cropley, 1980), and the driver's potential to learn from
experience.
Perhaps more importantly, the other major finding was that clear distinctions could
nonetheless be made between drivers in accordance with self-reported accident involvement
and culpability in relation to driver affect/state, self-perception, attributions for accident
causation, and attitudinal/behavioural tendencies, in a manner which seemed to be meaningful
in terms of driver susceptibility to accident risk. Ile pattern of response for accident
involvement and culpability effects was then examined in relation to the norms which
emerged for age and sex, while the effects of driving experience duration and intensity were
examined separately. The second point of focus on any distinctive features of younger driver
risk, also allowed assessment of generalizability of findings across cultures, to some degree.
The findings appear to have considerable implications for the development of effective
accident prevention strategies, while suggesting that further exploration of drivers' causal
attribution bias in relation to road accidents and distinctions between drivers according to
subjective culpability may offer considerable safety benefits
Two Combustor Engine for Military Applications
No full textThe key requirements for military aircraft are high survivability and mission
success rate: the former will “exponentially” increase the latter. The survivability
of the aircraft depends crucially on its performance and energy signatures, to
which its propulsion system contributes significantly. Therefore this imposes
demands upon future propulsion systems for a better aerothermodynamics
performance with a lower energy signature.
However, the performances
achievable with conventional engine cycles
may be reaching their limits.
Therefore, the author was motivated to investigate the potential of the two combustor
engine for military fighter
applications; with respect to its
aerothermodynamics performance and infrared signature.
An extensive literature survey was conducted to identify the uptodate
research for the two combustor
engine. Based on the collected information,
systematic approaches were formatted with proven analytical methodologies for
conducting the present study. A proven conventional engine (i.e. F100PW229
engine, based on “open publication”),
for powering military fighter aircraft, was
selected for benchmarking purposes in order to identify the prospect of the two combustor
engine. With an engine performance-simulation
program of high
fidelity and a detail engine model, the accuracy of the predictions of the engines’
performances are greatly improved. The key contribution is the establishment on
the influences of the two combustor
engine on the performances of the selected
fighter aircraft, in particular the transient behaviour, steady state
flight
characteristics (e.g. flight envelope)
and infrared signatures. This research relates
the performance of the two combustor
engine to that of the aircraft, which was not
found in any uptodate
publication. The availability of this research will allow
engine and aircraft studies to include two combustor
solution in a more secure
way than it was possible.
In this investigation, the main analytical tool employed is a Cranfield
University inhouse
developed engine performance-simulation
program,
TURBOMATCH. The author has implemented various subprograms
to interface
with TURBOMATCH in order to conduct specific simulations, e.g. transient behaviour
predictions. All the analyses have been undertaken using data from the
published literature
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