1,721,061 research outputs found
Multi-disciplinary performance studies on propulsion system integration for military aircraft.
Full text linkMilitary aircraft propulsion systems represent one of the most challenging sectors of jet engine design: Operating at an extremely variable environment strongly influenced by aircraft aerodynamics, these engines should pack high thrust output at the minimum possible size without compromising reliability and operating cost. In addition, the multidisciplinary nature of military aircraft operations frequently introduces contradicting performance objectives which are hard to incorporate to engine design. All the above are combined with the very high cost of engine development, necessitating proper selections early in the design phase to ensure the success of the development process and the viability of new engine concepts.
Despite the significant volume of research in the field and perhaps due to the sensitivity of the data involved, studies published to date are focused on rather specific topics without addressing the full multidisciplinary aircraft-propulsion system integration problem. In order to achieve this, a new synthesis of methods needs to be established combining aspects and contributions from
different areas of research.
This project investigates the development of a new methodology for interconnecting engine preliminary design to aircraft operational requirements. Under this scope, a representation of a generic military airframe is constructed and combined with engine performance models and simulation tools to investigate propulsion system effects on aircraft mission performance and survivability. More specifically, the project’s contributions in the field of military aircraft propulsion system integration are focused on three domains:
• A new military aircraft representation modelling critical aspects of the interaction between the aircraft and the propulsion system: Aircraft aerodynamics, airframe/propulsion system aerodynamic interference, IR and noise signature. The model has low computational requirements and is suitable for use in the context of large-scale parametric studies and trajectory optimization cases.
• New simulation-based techniques for estimating climb performance and assessing the mission capabilities of aircraft/engine configurations in realistic mission scenarios. Points of novelty within the developed methods include a multi-objective formulation to the climb trajectory problem, a technique for Altitude-Mach tracking, an expansion of the Energy-Manoeuvrability (E-M) technique allowing for the concurrent optimization of the aircraft trajectory and engine schedule and the introduction of minimum noise and IR trajectories for military aircraft.
• The quantification of propulsion system effects on aircraft survivability, taking into account both the aircraft’s IR signature and aircraft/missile kinematic performance. This is achieved through a combination of an aircraft IR model with kinematic simulations of missile-vs-aircraft and aircraft-vs-aircraft which are used to measure an aircraft’s susceptibility to attacks, along with its own ability to attack manoeuvring targets.
The above methods are developed and validated using published data and applied to investigate aircraft performance trends in a series of test cases where the effectiveness of different propulsion system designs is evaluated in a variety of simulated mission tasks. The results successfully demonstrate the developed methods’ ability to quantify the relation between aircraft performance and engine design, providing a basis for understanding the performance trade-offs that result from the adoption of different propulsion system configurations, to maximize the efficiency of the powerplant design process.PhD in Aerospac
The effects of bleed on gas turbine performance.
Full text linkComparison of the alternative method against a compressor ’splitting’ method showed comparable, and at off-design conditions, better, results can be obtained with the need for extensive manual model adjustment that the splitting method requires. This method has been implemented in 0-D cycle analysis software, which uses thermodynamic principles and component maps to calculate engine performance. Such a model tends to be used to analyse the overall effects of a component change on the engine cycle in a rapid and low-complexity manner (at a range of off-design conditions), whilst still producing a satisfactory level of accuracy. In the initial stages of a design project, the quick analysis and results from the 0-D software are essential to narrow down design choices and to analyse off-design performance. In this respect, the alternative method offers an enhancement to current methods for modelling bleed in the gas turbine.
Using this method to vary bleed stage and amount has been shown to change the engine running line and hence surge margin. This method can be used to produce three-dimensional plots showing the combined effect of bleed amount and offtake stage location at a range of fixed parameters according to the user requirements (e.g. fixed speed, temperature or massflow).PhD in Aerospac
Mechatronics numerical modelling for integrated turbo-electric techno-economic environmental risk assessment
No full textPilidis, Pericles - Associate SupervisorLong-term targets from the aerospace administration are to have cleaner, cost-efficient, and more performance-efficient transportation. The National Aeronautics and Space Administration (NASA) has proposed several solutions to hybrid technology, of which the turbo-electric distributed propulsion (TeDP) model is one of the latest promising models. This research project presents numerical modelling of the integrated TeDP model through the method of assisting technical performance, considering the economic and environmental risks. The contribution to numerical modelling is an integrated electrical module on the academic multidisciplinary Cranfield University gas-turbine TurboMatch® simulation tool with the projected method. In piloting this project, the outcome of this work advances the knowledge of TeDP and the future technology of aviation-distributed propulsion.
Moreover, a proper simulation tool to assist TeDP and ‘more electric aviation’ has been upgraded in TurboMatch. In addition, an integrated development environment (IDE) extension for TurboMatch was developed to investigate the electrical grid in TeDP. This work presents a toolkit for assessing the power and efficiency profiles of the electrical network specified for TeDP. From the given level of thrust, the methodology was used to evaluate and optimise the electrical network. A number of integration electric propulsion models were developed to demonstrate the assisting method for redundancy and reliability improvement. The total goal was to initialise the features of the TeDP mechatronics and electrical grid with the best technical, economic, and environmental solutions for the greatest efficiency.
The implication of this research is to understand the concept of TeDP using the use-case study of NASA’s N3-X conceptual proposal for project progress validation. The contribution knowledge lies in the area of the numeric model and the method to assist TeDP using the devised techno-economic environmental risk assessment (TERA) concept. The project inputs focus on future long-term goals for intelligent TeDP.PhD in Aerospac
Gas turbine performance studies for LH₂-fuelled engines.
Full text linkThe aim of this Individual Research Project is to lay solid foundations for the investigation of liquid hydrogen utilisation in aero gas turbines employing Cranfield University’s Turbomatch software.
To this day, including key components like heat exchangers is considerably limited in this software. As heat exchangers are believed to be vital in order to take advantage of the unique properties of liquid hydrogen, this thesis aims to create the possibility to carry out investigations in this field without depending on similar tools from outside Cranfield University.
To do so, a code is created in Matlab to serve as a heat exchanger library in which key parameters like outlet temperatures, overall pressure drops or geometrical characteristics are calculated in a split second. This code is validated, and results obtained from it are shown, compared and discussed.
Different engine configurations are modelled in Turbomatch (in which the location of the heat exchangers is varied from one model to the other). The outputs from the code are introduced in these Turbomatch models and simulations are run. Results from these simulations are plotted and analysed, highlighting the impact of these heat exchangers according to the location they are on.
Finally, some conclusions are extracted from all of the above and recommendations for future researches are listed.MSc by Research in Thermal Powe
The impact of heat transfer effects on civil aircraft engine transient performance
No full textPilidis, Pericles - Associate SupervisorDuring gas turbine transient manoeuvre, heat transfer occurs between the fluid
and metal. This results in various heat transfer effects, including heat soakage,
tip clearance, and change in component performance map. These will cause heat
loss and change in component flow characteristic and efficiency, which further
affect gas turbine transient performance. In this work, a comprehensive heat
transfer model including heat soakage, tip clearance and compressor map
modification has been developed. The proposed heat soakage model improves
the current state-of-the-art model by establishing a comprehensive thermal
network with the consideration of the combustor temperature distribution and
cooling technologies including film cooling, internal cooling, and thermal barrier
coatings. Additionally, the proposed novel compressor map modification model
can derive numerical correlations for compressor maps based on movement of
compressor speed line and map scaling, enabling the modification of adiabatic
maps to non-adiabatic maps during transient simulations. It improves the current
compressor map modification models by ensuring both flexibility and accuracy.
The developed heat transfer model has been integrated into Cranfield gas turbine
simulation platform Turbomatch, enhancing the realism of transient simulations.
The accuracy of the proposed model has been validated against data from public
sources, simulation platforms, and experimental results. A sensitivity analysis has
also been conducted to assess the impact of various assumptions on heat flow
rate estimation. The impact of heat transfer to overall engine’s performance has
been demonstrated by simulating transient operation of a turbojet and two
turbofan engines to demonstrate the effects of heat transfer on gas turbine
transient performance. Comparing with the conventional heat soakage method,
the application of the improved models can capture a delay on engine’s response
beyond the one simulated by the existing methods. This is a result of considering
the combustor temperature distribution and cooling technologies, not included in
the conventional heat soakage models. For the impact of heat transfer effect on
compressor characteristic and performance, a 4% reduction in compressor surge
margin is observed during a hot reslam transient manoeuvre, as a result of
movement in compressor speed line due to heat transfer effect.PhD in Aerospac
Techno-economic studies of environmentally friendly Brayton cycles in the petrochemical industry
Full text linkBrayton cycles are open gas turbine cycles extensively used in aviation and
industrial applications because of their advantageous volume and weight
characteristics. With the bulk of waste exhaust heat and engine emissions
associated, there is need to be mindful of environmentally-friendliness of these
engine cycles, not compromising good technical performance, and economic
viability.
This research considers assessment of power plants in helicopters, and aeroderivative
industrial gas turbines combined-heat-and-power (ADIGT-CHP) in the
petrochemical industry. Thus, it consists of two parts: part A focuses on
performance analysis of helicopter gas turbines, while part B entails technoeconomic
and environmental risk assessment of ADIGT-CHP in the
petrochemical industry. The investigation encompasses comparative
assessment of simple cycle (SC) and advanced gas turbine cycle options
including the component behaviours and the environmental and economic
analysis of the systems. The advanced cycles considered include: recuperated
(RC), intercooled (IC), intercooled-recuperated (ICR), and low pressure
compressor zero-staged (LPC-ZS), cycles.
The helicopter engines are analysed and subsequently converted to small-scale
ADIGT engines. Also, modelling combined-heat-and-power (CHP)
performances of small-scale (SS), and large-scale (LS) ADIGT engines is
implemented. More importantly, a large part of the research is devoted to
developing a techno-economic model for assessing, predicting, and comparing
viability of simple and advanced cycle ADIGT-CHP in the petrochemical
industry in terms of net present value (NPV), internal rate of return (IRR), and
simple payback period (SPBP). The techno-economic performances of the
ADIGT-CHP cycles are measured against the conventional case of grid power
plus on-site boiler. Besides, risk and sensitivity of NPV with respect to uncertain
changes in grid electricity cost, gas fuel cost, emission cost, and electricity
export tariff, are investigated. Two case studies underlie the development of the
techno-economic model. One case study demonstrates the application of the
model for large-scale (LS) ADIGT-CHP, and the other for small-scale (SS)
ADIGT-CHP, all in the petrochemical industry. By so doing, techno-economic
and environmental risk analysis framework (a multi-disciplinary preliminary
design assessment tool comprising performance, emissions, economic, and risk
modules) is adapted to ADIGT-CHP in the petrochemical industry, which is the
aim of this research.
The investigation and results led to the conclusions that advanced cycle
helicopter and ADIGT engines exhibit higher thermal efficiencies than simple
cycle, and that savings exist in operational costs of ADIGT-CHP above the
conventional case. Thus, for both SS ADIGT-CHP, and LS ADIGT-CHP cases,
all ADIGT-CHP cycles are profitable than the conventional case. For LS ADIGT-
CHP category, the IC ADIGT-CHP is the most profitable, whereas for SS
ADIGT-CHP category, the RC ADIGT-CHP is the most profitable. The
contribution to knowledge of this research is the development of a technoeconomic
model for assessing, predicting, and comparing viability of simple and
advanced cycle ADIGT-CHP in the petrochemical industry in terms of NPV,
SPBP, and IRR over the conventional case of grid power plus on-site boiler. A
second contribution is the derivation of simple and advanced cycle small-scale
ADIGT and ADIGT-CHP from helicopter engines.
Cont/D
Research on environmentally friendly fire suppression systems for aircraft cargo.
Full text linkIt is widely known in the aviation community that the use of Halon1301 as fire
suppression agent has been banned as it presents high ozone depleting
potential. This fact dictates that there is a necessity for fire suppression systems
replacement on all existing aircraft within a limited timeframe. So far, Nitrogen
(IG-100) was proven to be the most promising replacement agent for future
aviation. The present research project attempts to assess the handling,
performance and installation of a Nitrogen (IG-100) fire suppression system on
aircraft cargo in order to accelerate the transition to Halon-free systems. The
research has been conducted under the umbrella of the EU Clean Sky 2 (CS2)
“Environmentally Friendly Fire Suppression System for Cargo using Innovative
Green Technology” (EFFICIENT) project.
The methods used to achieve the project targets are based on analytical and
numerical 3D-CFD modelling as well as both in-house and public domain
experimental information of respective cargo fire suppression systems.
Additionally, they are aligned with FAA requirements and follow the Minimum
Performance Standard (MPS) required for testing and certification. The Nitrogen
(IG-100) system design space exploration focused on the examination of
exchange rates between parameters such as the number and location of
discharge nozzles and ventilation ports with the system effectiveness, operability
and safety. The resulted fire suppression system design was also used for the
development of the detailed design and operation strategy of the Cranfield in-
house test rig as well as the experimental testing and procedures, the risk
assessment and installation cost estimation.
The outcomes of CFD simulations presented satisfactory agreement with the
theoretically expected analytical calculations. Additionally, they were validated
against the experimental data coming from the above mentioned Cranfield based
test rig. The data regarded No-Fire and Open Surface Liquid Fire tests using Jet-
A fuel. Both CFD and experiments showed that system achieved the desired
average Oxygen concentration within 60 seconds discharge, while maintaining it
below 16% for more than 45 minutes, satisfying the FAA MPS. Additionally, the
average overpressure level inside the compartment remains within limits both
during and after agent discharge. Finally, based on their comparison, numerical
model adaptations and calibration are suggested in order to improve modelling
fidelity and simulation accuracy.
The proposed Nitrogen based design suggests minimum modifications to the
already existing Halon1301 based systems in order to accelerate the
replacement process. Furthermore, the system provides ease in handling and
operation with capabilities of minimising Nitrogen wastage by varying the agent
mass used based on the level of the cargo load and the nature of its content.
Finally, recommendations for future improvements regarding the system
response time, the fire protection time, the weight and complexity are included.PhD in Aerospac
Design space exploration of gas turbine based ship propulsion systems
Full text linkThe conceptual design of a ship propulsion system, developed during the early
stages of the overall ship design process, has a very large impact on the overall
design and performance of a ship. Gas turbines are often utilized for warship
propulsion systems designed to fulfil requirements of high ship speed and power
density. To achieve a high overall system-level efficiency, gas turbines are often
used in combined architectures with diesel engines along with geared, electric or
hybrid transmission systems driving multiple propulsors. The process for the
development of the conceptual design for such ‘combined’ systems, designed to
achieve multiple and often conflicting design objectives, is significantly more
complex compared to that for systems where a single-engine drives a propulsor.
A number of approaches are currently used in practice towards the conceptual
design of a ship, ranging from manual ‘design lanes’ based iterative approaches,
to computerized overall ‘ship as a system’ design synthesis approaches.
Towards the conceptual design of the propulsion system, both these approaches
pose their own limitations, wherein the approach of the manual iterative design
process relies heavily on the preferences of experts and approximations based
on past experience; while the ship design synthesis approach usually yields good
results generally if the candidate propulsion architectures are based on existing
designs.
This research work proposes a model-based process for the design space
exploration using a model-based ‘Techno-economic & Environmental Risk
Assessment’ (TERA) approach. To undertake feasibility and performance
analysis of the candidate propulsion system architectures, the process involves
building performance models of the candidate propulsion system architectures at
this very early stage the overall design process of the ship and utilizing the
generated results as the basis of design related decisions.
For undertaking the performance modelling of the multiple candidate propulsion
system architectures, an agile modelling and simulation framework was
considered essential that could handle the complexity of ‘combined’ propulsion
plants. To achieve this, a component-based modelling software, ‘Poseidon +’,
has been developed as a part of the present work which enables 0-D modelling
of gas turbine engines as well as the entire propulsion system in the same
framework. A key aspect of this work was the development of an algorithm that
analyses the direction of the torque transmission across the complex
transmission system of ‘combined’ plants, based solely on the based on the
states of the engine and clutches.
For undertaking TERA, a suite of ‘Multiple-Criteria Decision-Making’ (MCDM)
methods were selected and applied to select a compromise solution from
competing propulsion system architectures, using a combination of performance
data generated from simulation of developed models, and comparative expert
opinions-based metrics for information not available early in the ship design
process. To execute the MCDM procedure, a methodology of deriving weights of
the competing design criteria using a combination of hierarchal and network
structure, considering the degree of relationships between the design criteria, has
been demonstrated.
The overall proposed approach for design space exploration of gas turbine based
‘combined’ ship propulsion systems has been demonstrated towards the
conceptual design analysis of two notional ship designs. The results of the
analysis show the effectiveness of the proposed procedure for design space
exploration of ship propulsion systems.PhD in Aerospac
Implications of military aircraft’s mission optimal performance on gas turbine engine life expectancy
No full textDevaiah, Nalianda - Associate SupervisorGas turbine engines have a crucial role in evaluating military aircraft performance.
Operating in a range of missions and environmental conditions, they are
subjected to an excessively demanding usage often reaching their operating
limits. The impact prediction on engine components degradation of this adverse
usage requires a multi-disciplinary approach to best capture its effects.
This master thesis investigates the implications of optimal mission performance
on the degradation of military gas turbine engines. The research focuses on the
degradation of first stage of the high-pressure turbine caused by the failure
mechanisms of creep, low cycle fatigue and high cycle fatigue, each acting
independently on the turbine blades.
By exploring the implications of mission performance on engine degradation, this
study provides valuable insights for optimizing mission execution strategies and
improving operational efficiency in military aviation.
Through a comprehensive analysis, several key findings have been identified. It
was observed that as the turbine entry temperature (TET) decreases, the
stresses on the turbine blade have a disproportionately greater effect on the
overall damage. This suggests that maintaining optimal TET levels is crucial for
mitigating engine degradation, as an increase of 0.005% in blade temperature
can lead to 40% more thrust, 100% more fuel consumption but can reduce life by
18% in Creep, 15% in LCF and 14% in HCF.
In addition, the study reveals that the use of afterburner though having similar
thermo-mechanical stresses upon the blades with the maximum dry setting, the
extensive usage in a mission can significantly impact the life consumption. A
mission with 40% less overall duration can present an up to 40% reduced life
expectancy.
Lastly, the investigation highlights the significant differences in life consumption
during several optimal climb paths. A time optimized profile is found to be the
most damage inflicting having 3 times less lifespan than noise and IR optimized
paths. A life expectancy of only 80 flight hours is predicted for the usage applied
on this profile resulting from the impact of low cycle fatigue contribution.
This research contributes to the field of military-related costs by shedding light on
the operational availability of gas turbine engines.MSc by Research in Aerospac
Water ingestion effects on gas turbine engine performance
Full text linkAlthough gas turbine engines are designed to use dry air as the working fluid,
the great demand over the last decades for air travel at several altitudes and
speeds has increased aircraft’s exposure to inclement weather conditions.
Although, they are required to perform safely under the effect of various
meteorological phenomena, in which air entering the engine contains water,
several incidents have been reported to the aviation authorities about power
loss during flight at inclement weather. It was understood that the rain ingestion
into a gas turbine engine influences the performance of the engine and
particular the compressor and the combustor.
The effects of water ingestion on gas turbine engines are aerodynamic,
thermodynamic and mechanical. These effects occur simultaneously and affect
each other. Considering the above effects and the fact that they are timedependent,
there are few gas turbine performance simulation tools, which take
into account the water ingestion phenomenon.
This study is a new research of investigating theoretically the water ingestion
effects on a gas turbine performance. It focuses on the aerodynamic and
mechanical effects of the phenomenon on the compressor and the combustor.
The application of Computational Fluid Dynamics (CFD) is the basic
methodology to examine the details of the flow in an axial compressor and how
it is affected by the presence of water. The calculations of water film thickness,
which is formed on the rotor blade, its motion (direction and speed) and the
extra torque demand, are provided by a code created by the author using
FORTRAN programming language. Considering the change in blade’s profile
and the wavy characteristics of the liquid film, the compressor’s performance
deterioration is calculated.
The compressor and combustor’s deterioration data are imported to a gas
turbine simulation code, which is upgraded to calculate overall engine’s
performance deterioration. The results show a considerable alteration in
engine’s performance parameters and arrive at the same conclusions with the
relevant experimental observations
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