CERES :: Browsing by Author "Lawson, Craig P."

Browsing by Author "Lawson, Craig P."

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Open Access
Aircraft thermal management: Practices, technology, system architectures, future challenges, and opportunities
(Elsevier, 2021-11-12) van Heerden, Albert S. J.; Judt, David M.; Jafari, Soheil; Lawson, Craig P.; Nikolaidis, Theoklis; Bosak, D.
The provision of adequate thermal management is becoming increasingly challenging on both military and civil aircraft. This is due to significant growth in the magnitude of onboard heat loads, but also because of their changing nature, such as the presence of more low-grade, high heat flux heat sources and the inability of some waste heat to be expelled as part of engine exhaust gases. The increase in the use of composites presents a further issue to address, as these materials are not as effective as metallic materials in transferring waste heat from the aircraft to the surrounding atmosphere. These thermal management challenges are so severe that they are becoming one of the major impediments to improving aircraft performance and efficiency. In this review, these challenges are expounded upon, along with possible solutions and opportunities from the literature. After introducing relevant factors from the ambient environment, the discussion of the challenges and opportunities is guided by a simple classification of the elements involved in thermal management systems. These elements comprise heat sources, heat acquisition mechanisms, thermal transport systems, heat rejection to sinks, and energy conversion and storage. Heat sources include both those from propulsion and airframe systems. Heat acquisition mechanisms are the means by which thermal energy is acquired from the sources. Thermal transport systems comprise cooling loops and thermodynamic cycles, along with their associated components and fluids, which move the heat from the source to the sinks over potentially large distances. The terminal aircraft heat sinks include atmospheric air, fuel, and the aircraft structure. In addition to the discussions on these different elements of thermal management systems, several topics of particular priority in aircraft thermal management research are deliberated upon in detail. These are thermal management for electrified propulsion aircraft, ultra-high bypass ratio geared turbofans, and high power airborne military systems; environmental control systems; power and thermal management systems; thermal management on supersonic transport aircraft; and novel modelling and simulation processes and tools for thermal management.
Open Access
Aircraft wing build philosophy change through system pre-equipping of major components
(Society of Automotive Engineers, 2016-09-27) Judt, David M.; Forster, Kevin; Lockett, Helen L.; Lawson, Craig P.; Webb, Philip
In the civil aircraft industry there is a continuous drive to increase the aircraft production rate, particularly for single aisle aircraft where there is a large backlog of orders. One of the bottlenecks is the wing assembly process which is largely manual due to the complexity of the task and the limited accessibility. The presented work describes a general wing build approach for both structure and systems equipping operations. A modified build philosophy is then proposed, concerned with large component pre-equipping, such as skins, spars or ribs. The approach benefits from an offloading of the systems equipping phase and allowing for higher flexibility to organize the pre-equipping stations as separate entities from the overall production line. Its application is presented in the context of an industrial project focused on selecting feasible system candidates for a fixed wing design, based on assembly consideration risks for tooling, interference and access. Further industrial, human and cost factors are discussed to establish project competiveness. The main findings show a potential to reduce assembly time of systems equipping operations by 30% together with a lower ergonomic impact score. The paper also presents design rules derived from the case study towards a system design for a pre-equipping build philosophy. Primarily, cross component interfaces should be avoided as much as possible. Access for phase one structural operations need to be considered as well as major component jig pickup points. To increase system installation independence, layout considerations of components should lead to sufficient access to all components at any installation stage.
Open Access
Analytical investigation into the effects of nitrogen enriched air bubbles to improve aircraft fuel system water management
(SAGE, 2017-11-19) Terada, Yuri; Lawson, Craig P.; Shahneh, Amir Z.
In the aircraft fuel system, water–ice contamination within fuel tanks has been one of the most serious challenges. This issue was highlighted in 2008 by an accident triggered by restricted fuel flow due to the ice formation within the system. The on-board inert gas generation system, which is already installed on some aircraft to prevent the outbreak of fire in the fuel tank, is a potentially feasible method to improve the water management. This paper focuses on the impact of bubbles from the on-board inert gas generation system system on water in the fuel tank. In order to explore the bubble effect, the relationship between orifice configuration and bubble parameter was investigated by means of mathematical models and existing experimental data. Moreover, by combining a MATLAB code and the introduced bubble model, the effect of bubble size and rising speed on the water contamination in the fuel tank was observed. For the water absorption process, a new model was introduced using a mass transfer coefficient. Finally, this article concludes that the amount of accumulated water is dependent on the bubble size and rising speed, and an optimal bubble size or speed is predictable once the coefficient has been obtained.
Open Access
The application of a new research and development project selection model in SMEs.
(Elsevier Science B.V., Amsterdam., 2006-02-01T00:00:00Z) Lawson, Craig P.; Longhurst, Philip J.; Ivey, Paul C.
The work reported in this paper investigates Research and Development (R&D) project selection models, focusing on the application of a new hybrid project selection model in a UK based engineering Small to Medium-sized Enterprise (SME). Work is done to enable the new project selection model to be applied in an SME and the model is then field tested. Field test results provide insight into the barriers to the adoption of such a model in an SME, either as a decision support tool or as a knowledge acquisition and learning tool. Insights are gained into the suitability and limits that exist within SMEs for the use of such decision support models. As an outcome of the field test results a simple R&D project portfolio cash-flow tracking method is proposed.
Open Access
Application of an automated aircraft architecture generation and analysis tool to unmanned aerial vehicle subsystem design
(SAGE Publications, 2014-11-19) Judt, David M.; Lawson, Craig P.
The work presents the application of a new computational framework, addressing future preliminary design needs for aircraft subsystems. The ability to investigate multiple candidate technologies forming subsystem architectures is enabled with the provision of automated architecture generation, analysis and optimisation. The core aspects involve a functional decomposition, coupled with a synergistic mission performance analysis on the aircraft, architecture and component level. This may be followed by a complete enumeration of architectures combined with a user-defined technology filtering and concept ranking procedure. In addition, a novel hybrid heuristic optimiser, based on ant colony optimisation and a genetic algorithm, is employed to produce optimal architectures in both component composition and design parameters. The framework is applied to the design of a regenerative energy system for a long endurance high altitude unmanned aerial vehicle, considering various emerging technologies. A comparison with the traditional design processes and certification requirements is made as well as technology trends summarised and substantiated.
Open Access
Behaviour of water in jet fuel: a literature review
(Elsevier Science B.V., Amsterdam., 2013-07-31T00:00:00Z) Baena-Zambrana, S.; Reppeto, S. L.; Lawson, Craig P.; Lam, Joseph K.-W.
This review gives a detailed account of the different types of water contaminated fuel and the conditions that bring about each form of contamination. It also considers studies that have been done to date that investigate the physics behind the behaviour of water in different hydrocarbons and jet fuel at low temperatures.
Open Access
Capacitance Tip Timing Techniques in Gas Turbines
(Cranfield University, 2003-11) Lawson, Craig P.; Ivey, Paul C.
The vibration of turbomachinery blades is an important phenomenon to understand, observe and predict and is the reason for developing a tip timing measurement system. Vibration leads to High Cycle Fatigue (HCF), which limits blade durability and life. HCF can result in blade failure, having expensive consequences for the engine involved. The traditional method for monitoring blade vibration under test conditions is to use blade mounted strain gauges. However, strain gauges are costly and time consuming to install. They have a limited operating life as they are subjected to the harsh on-engine conditions. Only a limited number of blades can be monitored with strain gauges as the number that can be used is limited by the number of channels in the slip ring or telemetry. They can also interfere with the assembly aerodynamics. Consequently non-intrusive alternative techniques such as tip timing are sought. Capacitance probe based clearance measurement systems see widespread use in turbomachinery applications to establish rotor blade tip clearance. This thesis reports investigations into an alternative and additional use in aero-engine rotor blade tip timing measurement for these commercially available systems. Tip clearance is of great importance in the gas turbine industry; this is clear from the fact that gas turbine efficiency has an inverse relationship with tip clearance. Large tip clearance leads to large leakage flows, hence low efficiency, thus the common use of the capacitance probe clearance measurement technique in monitoring turbomachinery. Optical systems have been successfully used to measure rotor blade tip timing on test rigs with several optical probes mounted equally spaced around the turbomachine casing. However, there are practical problems associated with mounting such monitoring systems on in-service jet engines. Optical probes require high maintenance to keep the lenses clean, probably incorporating a purge air system to keep the lenses from fouling. Such impracticalities and added weight make it unlikely that an optical probe based tip timing system will be fitted on an in-service engine in the foreseeable future. In this thesis the scope for a dual use sensor to measure both turbomachinery tip clearance and tip timing is investigated. Since it is impractical to measure blade tip clearance with an optical probe, then the obvious choice for such a sensor is a capacitance probe. Therefore, a commercially available FM capacitance probe based blade tip clearance measurement system is used in a series of tip timing practical investigations. The equipment and instrumentation designed, assembled and produced to facilitate this investigation is documented. These include the development of an optical once per revolution sensor and the design of an independent vibration measurement system based on blade mounted strain gauges. Through an extensive body of experimental work the practicalities in this alternate use of the tip clearance measurement equipment have been assessed. System responses pertaining to tip timing measurement have been investigated, characterised and quantified. The accuracy by which tip timing can be measured using the system has been reported through the findings of an experimental programme carried out on a full-sized, low-speed compressor. Specifically, dual capacitance probe tip timing derived vibration amplitudes have been compared to those derived from blade mounted strain gauge signals. Sources of error have been identified and quantified. Amplitudes were found to agree within the calculated error bands. Instantaneous resonant blade vibrations measured through single capacitance probe tip timing have been correlated with strain gauge derived vibration levels. This has also been done as the rotor traverses blade resonant speed. In this case the vibration phase change across resonance expected from theory was successfully detected through tip timing. Also, the accuracy by which blade time of arrival can be determined by using capacitance probe tip timing has been assessed using a precision OPR sensor and a non-vibrating compressor rotor blade. The characteristics of a DC capacitance probe based clearance measurement system's response to movement in 3D space in proximity to a blade tip have been mapped. Detection of small vibrations have also been investigated in a series of static impulse tests.
Open Access
Development of an automated aircraft subsystem architecture generation and analysis tool
(Emerald, 2015-12-01) Judt, David M.; Lawson, Craig P.
Purpose – The purpose of this paper is to present a new computational framework to address future preliminary design needs for aircraft subsystems. The ability to investigate multiple candidate technologies forming subsystem architectures is enabled with the provision of automated architecture generation, analysis and optimization. Main focus lies with a demonstration of the frameworks workings, as well as the optimizers performance with a typical form of application problem. Design/methodology/approach – The core aspects involve a functional decomposition, coupled with a synergistic mission performance analysis on the aircraft, architecture and component levels. This may be followed by a complete enumeration of architectures, combined with a user defined technology filtering and concept ranking procedure. In addition, a hybrid heuristic optimizer, based on ant systems optimization and a genetic algorithm, is employed to produce optimal architectures in both component composition and design parameters. The optimizer is tested on a generic architecture design problem combined with modified Griewank and parabolic functions for the continuous space. Findings – Insights from the generalized application problem show consistent rediscovery of the optimal architectures with the optimizer, as compared to a full problem enumeration. In addition multi-objective optimization reveals a Pareto front with differences in component composition as well as continuous parameters. Research limitations/implications – This paper demonstrates the frameworks application on a generalized test problem only. Further publication will consider real engineering design problems. Originality/value – The paper addresses the need for future conceptual design methods of complex systems to consider a mixed concept space of both discrete and continuous nature via automated methods.
Open Access
Environmental Impact Assessment, on the Operation of Conventional and More Electric Large Commercial Aircraft
(2013-09-17T00:00:00Z) Seresinhe, R.; Lawson, Craig P.; Sabatini, Roberto
Global aviation is growing exponentially and there is a great emphasis on trajectory optimization to reduce the overall environmental impact caused by aircraft. Many optimization techniques exist and are being studied for this purpose. The CLEAN SKY Joint Technology Initiative for aeronautics and Air transport, a European research activity run under the Seventh Framework program, is a collaborative initiative involving industry, research organizations and academia to introduce novel technologies to improve the environmental impact of aviation. As part of the overall research activities, "green" aircraft trajectories are addressed in the Systems for Green Operations (SGO) Integrated Technology Demonstrator. This paper studies the impact of large commercial aircraft trajectories optimized for different objectives applied to the on board systems. It establishes integrated systems models for both conventional and more electric secondary power systems and studies the impact of fuel, noise, time and emissions optimized trajectories on each configuration. It shows the significant change in the fuel burn due to systems operation and builds up the case as to why a detailed aircraft systems model is required within the optimization loop. Typically, the objective in trajectory optimization is to improve the mission performance of an aircraft or reduce the environmental impact. Hence parameters such as time, fuel burn, emissions and noise are key optimization objectives. In most instances, trajectory optimization is achieved by using models that represent such parameters. For example aircraft dynamics models to describe the flight performance, engine models to calculate the fuel burn, emissions and noise impact, etc. Such techniques have proved to achieve the necessary level of accuracy in trajectory optimization. This research enhances previous techniques by adding in the effect of systems power in the optimization process. A comparison is also made between conventional power systems and more electric architectures. In the conventional architecture, the environmental control system and the ice protection system are powered by engine bleed air while actuators and electrics are powered by engine shaft power off-takes. In the more electric architecture, bleed off take is eliminated and the environmental control system and ice protection system are also powered electrically through engine shaft power off takes.
Open Access
Formation flight investigation for highly efficient future civil transport aircraft
(Cambridge University Press, 2016-06-13) Durango, G. J.; Lawson, Craig P.; Shahneh, Abolghasem Zare
Formation flight could greatly assist the air transport industry in tackling the challenges of environmental impact, excessive reliance on fuel and overcapacity. Previous studies have shown drag reductions leading to significant fuel savings for aircraft in formation relative to their solo flight. Safety is guaranteed with the use of extended formation distances, and practical implementation issues could be solved in the near future. Since studies so far have focused on existing aircraft configurations and technology, a case study using a strut-braced wing airliner was carried out to ascertain its applicability to less conventional craft. The present results did not indicate such clear-cut benefits. If formation flight is to be successful and beneficial for the next generations of aircraft, it will be vital to consider its interaction with new technologies developed for highly efficient operation, in particular those aimed at reduction of aircraft drag such as laminar flow, and to do so early in the design of aerospace vehicles and wider systems.
Open Access
Framework for integrated dynamic thermal simulation of future civil transport aircraft
(AIAA, 2020-01-05) van Heerden, Albert S. J.; Judt, David M.; Lawson, Craig P.; Jafari, Soheil; Nikolaidis, Theoklis; Bosak, David
The development of increasingly more electric systems and ultra high bypass ratio turbofan engines for civil transport aircraft is projected to bring forth critical challenges regarding thermal management. To address these, it is required that the thermal behavior of the complete propulsion-airframe unit is studied in an integrated manner. To this purpose, a simulation framework for performing integrated thermal and performance analyses of the engines, airframe, and airframe systems, is presented. The framework was specifically devised to test novel integrated thermal management solutions for future civil aircraft. In this paper, the discussion focuses mainly on the thermal modeling of the wing and fuel. A highly flexible approach for creating wing thermal models by means of assembling generic thermal compartments is introduced. To demonstrate some of the capabilities, a case study is provided that involves thermal analysis of a single-aisle airplane with ultra high bypass ratio engines. Results are provided for fuel temperatures across flights in standard, hot, and cold days and for different airframe materials. Engine heat sink temperatures and input power to the engine gearboxes, both important parameters needed to design thermal management systems, are also presented.
Open Access
Multidisciplinary Optimisation Framework for Minimum Rotorcraft Fuel and Air Pollutants at Mission Level
(Royal Aeronautical Society, 2013-07-31T00:00:00Z) Linares, Carlos; Lawson, Craig P.; Smith, Howard
Helicopters play a unique role in modern aviation providing a varied range of benefits to society and satisfying the need for fast mobility. However, environmental concerns associated with the operation of rotorcraft have increased due to envisaged growth of helicopter operations. New rotorcraft designs, innovative aero engines and all-electrical systems, which may take decades to be in service, are being developed in order to diminish rotorcraft footprint on environment. However, since there is a large number of polluting rotorcraft that are in use and will only gradually be replaced, in the near-term, improvements to minimise air quality degradation may also be possible from better use of existing rotorcraft by focusing on mission profile management. A multidisciplinary framework, intended to generate outputs for estimating rotorcraft block fuel burn and emissions, was developed. Outcomes generated with this tool were, subsequently, the basis to carry out a parametric study for assessment of light single-engine rotorcraft environmental impact, in terms of fuel burn and emissions. Single and multi-objective optimisation for minimum fuel consumption and air pollutant emissions was part of this research as well.
Open Access
Physics-based thermal model for power gearboxes in geared turbofan engines
(ASME, 2021-01-11) Jafari, Soheil; Nikolaidis, Theoklis; van Heerden, Albert S. J.; Lawson, Craig P.; Bosak, David
Ultra-High Bypass Ratio Geared (UHBRG) turbofan technology allows a significant reduction in fuel burn, noise and emissions — key metrics for aircraft engine performance. However, one of the main challenges in this technology is the large amount of waste heat generated by the Power Gearbox (PGB). Therefore, having a practical tool for precise prediction of the PGB-generated thermal loads in UHBRGs is becoming a necessity. Such a tool would assist in analyzing engine performance, as well as ensuring that engine physical limitations/restrictions are not breached (e.g. over-temperature in fuel and oil, cocking, etc.). This paper presents a methodological approach to mathematically model the waste heat generated by a PGB on a UHBRG for different points on a typical flight profile. To do this, the total power loss in a PGB system is firstly defined as the summation of load-dependent and load-independent losses. Physics-based equations for each heat loss mechanism are introduced and, through a combination of the associated equations, a simulation model for the thermal loads calculation in PGBs is developed. In addition, the heat losses and efficiency of the PGB has been analyzed across a simulated flight. The developed PGB model calculates the main power losses generated in a gear reduction system of a turbofan engine. It is found that in a typical flight, the heat loss generated by the PGB can reach about 80% of the total waste heat generated by the engine. The values of the mechanical efficiency calculated by the tool at different flight points are above 97% which is in good agreement with publicly available data for planetary gearboxes. This tool is intended to be utilized by engine thermal management system designers to predict and analyze the heat loads generated by the PGB at different flight conditions
Open Access
A practical method to account for seal friction in aircraft hydraulic actuator preliminary design
(SAGE, 2016-05-10) Agarwal, Naresh K.; Lawson, Craig P.
Seals are used in hydraulic actuators or any other hydraulic devices to prevent passing of hydraulic fluid from one chamber to another, or to prevent external leakage and entry of any foreign contaminants. The primary function of any hydraulic actuator is to efficiently use hydraulic power to drive a load experienced during movement of control surfaces or movable aircraft structure. Efficient sealing helps in achieving this, but with its own friction which should be as minimal as possible. Thus, the estimation of seal friction force has crucial significance in hydraulic actuators, especially in flight control actuators that demand high performance and dynamic behavior characteristics while efficiently driving the load. This paper details the methodology adopted for theoretical estimation of total seal friction force of actuator as well as description of experimental test set-up and test method followed to record the total friction value at different positions of the actuator. The theoretical estimation was done using empirical formulae and graphs for predicting seal friction force by considering the effects of seal squeeze, hydraulic pressure, seal dimensions, seal material and then interpolating the same for the specific type of seals used. An experimental study is also presented in this paper, which can be conducted to validate the theoretically estimated value after building up of development prototypes. The validation is necessary as seal friction force calculation during design phase is an approximation and accurate friction of every seal is difficult to measure as it depends on a number of parameters. Thus, this paper explains the subject issue with the help of a case study which provides the theoretical estimation as well as its validation through an experiment to study this significant aspect of a hydraulic actuator design.
Open Access
Turbomachinery blade vibration amplitude measurement through tip timing with capacitance tip clearance probes
(Elsevier Science B.V., Amsterdam., 2005-01-01T00:00:00Z) Lawson, Craig P.; Ivey, Paul C.
Turbomachinery blade vibrations can cause High Cycle Fatigue, which reduces blade life. In order to observe this vibration a nonintrusive monitoring system is sought. The vibration can be detected by measuring blade tip timing since in the presence of vibration the blade timing will differ slightly from the passing time calculated from rotor speed. Much research and development has gone into investigating the ability of optical probes to achieve this. However, this paper looks at the potential for a dual use capacitance probe sensor to measure both tip timing and tip clearance. This paper provides new insights into the ability of a commercially available capacitance probe tip clearance measurement system for application as a non-intrusive turbomachinery blade tip timing measurement device. This is done by correlating capacitance probe tip timing results with simultaneously measured blade-mounted strain gauge vibration results and precise rotational speeds. Blade tip vibration amplitudes are measured using capacitance probes and compared to strain derived vibration levels. Thus the characterisation and quantification of the performance of the capacitance probe system when measuring blade vibration on a full-sized low-speed research compressor is analysed and reported.

Browsing by Author "Lawson, Craig P."

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