The low-noise optimisation method for gearbox in consideration of operating conditions

This paper presents a comprehensive procedure to calculate the steady dynamic response and the noise radiation generated from a stepping-down gearbox. In this process, the dynamic model of the cylindrical gear transmission system is built with the consideration of the time-varying mesh stiffness, gear errors and bearing supporting, while the data of dynamic bearing force is obtained through solving the model. Furthermore, taking the data of bearing force as the excitation, the gearbox vibrations and noise radiation are calculated by numerical simulation, and then the time history of node dynamic response, noise spectrum and resonance frequency range of the gearbox are obtained. Finally, the gearbox panel acoustic contribution at the resonance frequency range is calculated. Based on the conclusions from the gearbox panel acoustic contribution analyses and the mode shapes, two gearbox stiffness improving plans have been studied. By contrastive analysis of gearbox noise radiation, the effectiveness of the improving plans is confirmed. This study has provided useful theoretical guideline to the gearbox design

Performance Optimisation of a Geared Turbofan with Intercooler and Regenerator

With the enormous growth of the worldwide air traffic, many voices rise demanding urgent measures against climate changes. Therefore, the environmental and climate concerns are challenging and promoting the aviation sector to adopt innovative strategies and promising developments. Some of these advances, in the propulsion field, aim for more efficient engines that are less fuel dependent and that pollute less (noise and emissions). In this context, the continuous evolution for even more eco-friendly aeroengines, includes the proposal of introducing heat exchangers to meet the challenges of the future. Thus, this dissertation focuses on implementing an intercooler and/or a regenerator in a turbofan to understand the engine’s behaviour, as well as the influence of these two components in the performance parameters, more accurately, to assess the possibility of decreasing fuel consumption without jeopardizing thrust. To accomplish all this, a modern geared turbofan is used as the baseline engine, because this type of engine allows to reach high values of bypass ratios, as well as improves component efficiency and it weighs less than a conventional turbofan, so the extra weight from the heat exchangers have less impact. Furthermore, several engine parameters, such as bypass ratio, fan pressure ratio, compressor pressure ratio and turbine inlet temperature, are varied and theirs impacts on the performance parameters analysed (specific thrust and thrust specific fuel consumption) for each configuration. Besides the parametric study, a performance optimisation of all the four configurations – conventional GTF (Geared Turbofan), GTF with intercooler, GTF with regenerator and GTF with intercooler and regenerator - is done with the help of a genetic algorithm provided by the MATLAB software. The results showed that the conventional configuration is the best option, because it was the configuration with the lowest values of TSFC for a given specific thrust. Nevertheless, if the main concern is power production, production and maintenance costs than fuel costs, then the configuration with only the intercooler might be an interesting option, because it reached high values of specific thrust at lower turbine inlet temperatures. Additionally, if the turbine inlet temperature increases, then the regenerator effect is more pronounced, which might result in lower values of TSFC than the ones of the conventional configuration for the same amount of specific thrust.Com o enorme crescimento do tráfego aéreo mundial, muitas vozes se erguem a exigir medidas urgentes contra as alterações climáticas. Portanto, as preocupações ambientais estão a desafiar e impulsionar o setor da aviação a adotar estratégias inovadoras e desenvolvimentos promissores. Alguns desses avanços, no campo da propulsão, visam motores mais eficientes, com menor consumo de combustível, menores emissões de gases poluentes e menor ruído. Dito isto, a contínua evolução por motores aeronáuticos mais amigos do ambiente, poderá passar pela introdução de permutadores de calor, de modo a responder aos desafios do futuro. Assim sendo, esta dissertação tem como principal objetivo a implementação de um intercooler e/ou regenerador num turbofan, para entender o comportamento do motor, bem como a influência destes dois componentes nos parâmetros de desempenho. Mais concretamente, pretende-se avaliar a possibilidade de diminuir o consumo do combustível sem comprometer a tração. Para que isto seja possível, um motor moderno turbofan com caixa redutora (GTF) é utilizado como motor base, pois este tipo de motor permite atingir valores de razão de bypass elevados, bem como melhorar a eficiência dos componentes e pesar menos que um turbofan convencional, o que implica que o peso extra dos permutadores de calor tenha menos impacto. Nesta dissertação vários parâmetros do motor, como razão de bypass, razão de pressão da fan, razão de pressão do compressor e temperatura de entrada da turbina, são variados e seus impactos nos parâmetros de desempenho analisados (tração específica e consumo específico de tração) para cada configuração. Para além deste estudo paramétrico, realizase também a otimização do desempenho de todas as configurações - GTF convencional, GTF com intercooler, GTF com regenerador e GTF com intercooler e regenerador – com o auxílio de um algoritmo genético disponível no software MATLAB. Os resultados revelaram que a configuração convencional é a melhor opção, na medida em que é a que apresenta os valores mais baixos de TSFC para um dado valor de tração especifica. No entanto, se a principal preocupação é produção de energia e custos associados com a produção e a manutenção, do que custos de combustível então a configuração com apenas o intercooler apresenta-se como uma escolha interessante, pois permite trações específicas elevadas a baixas temperaturas de entrada na turbina. Por fim, caso se verifique uma tendência no aumento da temperatura de entrada na turbina, então o efeito do regenerador é mais significativo, o que muito provavelmente conduzirá a configuração com regenerador a ter valores de TSFC inferiores aos da configuração convencional para o mesmo valor de tração específica

The application of time encoded signals to automated machine condition classification using neural networks

This thesis considers the classification of physical states in a simplified gearbox using acoustical data and simple time domain signal shape characterisation techniques allied to a basic feedforward multi-layer perceptron neural network. A novel extension to the signal coding scheme (TES), involving the application of energy based shape descriptors, was developed. This sought specifically to improve the techniques suitability to the identification of mechanical states and was evaluated against the more traditional minima based TES descriptors. The application of learning based identification techniques offers potential advantages over more traditional programmed techniques both in terms of greater noise immunity and in the reduced requirement for highly skilled operators. The practical advantages accrued by using these networks are studied together with some of the problems associated in their use within safety critical monitoring systems.Practical trials were used as a means of developing the TES conversion mechanism and were used to evaluate the requirements of the neural networks being used to classify the data. These assessed the effects upon performance of the acquisition and digital signal processing phases as well as the subsequent training requirements of networks used for accurate condition classification. Both random data selection and more operator intensive performance based selection processes were evaluated for training. Some rudimentary studies were performed on the internal architectural configuration of the neural networks in order to quantify its influence on the classification process, specifically its effect upon fault resolution enhancement.The techniques have proved to be successful in separating several unique physical states without the necessity for complex state definitions to be identified in advance. Both the computational demands and the practical constraints arising from the use of these techniques fall within the bounds of a realisable system

A technoeconomic risk assessment of conventional aero-gas turbines: technological limits and future directions

Increasing environmental awareness, uncertain economic climates and fluctuating fuel prices have led to airlines investigating the means to lower aircraft fuel burn, emissions and noise, while maintaining the highest possible safety standards. This is done in order to reduce operating costs as well as a desire to offer customers more environmentally responsible transport options. The jet engine has been a fundamental part of passenger aircraft travel and has evolved to become more efficient and quiet. With an aim to improve the overall efficiency of the gas turbine, the industry has consistently sought to improve thermal and propulsive efficiency. Higher thermal efficiencies have been achieved through increased overall pressure ratios and the turbine entry temperatures, while higher propulsive efficiencies has been achieved through increase in bypass ratios. Conventional technology is however reaching the limits of any further improvements. This study seeks to investigate these design limits for the conventional aero gas turbine and focusses on the propulsion system of short to medium range jet aircraft, specifically catering to low cost airline operations in Europe. A techno-economic risk analysis approach was followed through the utilisation of a flexible multi-disciplinary framework. This allows a multitude of critical parameters and factors to be investigated and their effects established. Some of the key parameters investigated include the effect of design optimisation on SFC, mission fuel burn, engine sizes and weights. By first quantifying the current design parameters and associated constraints for the selected conventional propulsion system, an optimisation study is carried out to identify the possible design limits to which the conventional technology may be pushed. It is therefore possible to then quantify the maximum benefit available to this mature technology and also to further identify which future technologies may offer the most benefits for a particular airline market strategy. The key contribution to knowledge from this study is to therefore provide a techno-economic risk assessment of an optimised conventional high bypass ratio turbofan and establish the design limits that may be needed to achieve further benefits from conventional designs. The study is undertaken from an operator/airline perspective and further quantifies the point at which the investment opportunity of a novel technology justifies the risks associated with it. This study has shown that there is still potential for fuel burn improvement from the evolution of the conventional turbofan. This improvement could be up to 15-20% when compared to technology of the year 2000. This is shown to be achieved through improvement material and design of the high pressure compressor spool, aimed at essentially reducing weight and diameters. The study also includes a qualitative discussion on novel, disruptive technologies, and the risks associated with their introduction as future propulsion systems

Optimisation of the vehicle transmission and the gear-shifting strategy for the minimum fuel consumption and the minimum nitrogen oxide emissions

The paper outlines a computationally efficient analytical method for evaluating the fuel consumption and the nitrogen oxide emissions during manoeuvres pertaining to the New European Driving Cycle. An integrated optimisation procedure is also included in the analyses with minimisation of the brake specific fuel consumption and minimisation of the nitrogen oxide emissions as objective functions. A set of optimum gear ratios are determined for a four-speed transmission, a five-speed transmission and six-speed transmission as the governing parameters in the optimisation process. The analysis highlights the determination of gear-shifting objective-driven strategies based on the minimisation of either of the declared objective functions. A reduction of 7.5% in the brake specific fuel consumption and a reduction of 6.75% in nitrogen oxide emissions are attainable in the best-case scenario for a six-speed transmission and a gear-shifting strategy based on the lowest brake specific fuel consumption for the case of an engine. The novel integrated analytical simulations and multi-objective optimisation have not been hitherto reported in literature. It provides the opportunity for an objective intelligent-based approach to the use of gear shift indicator technology. The results of this study also show that transmission optimisation can act as an effective and inexpensive mean to enhance the fuel efficiency and to reduce the emissions

Multi-disciplinary preliminary design assessments of pusher counter-rotating open rotors for civil aviation

As a consequence of fuel cost escalation and increased stringent engine emission regulations, interest in counter-rotating open rotor engines (CRORs) has been renewed. R&D efforts are currently ongoing to develop the technologies required to ensure the appropriate levels of structural integrity, noise, vibrations and reliability. The assessment of the impact of the main low pressure preliminary design and control parameters of CRORs on mission fuel burn, certification noise and emissions is necessary to identify optimum design regions. These assessments aid the development process when compromises need to be performed as a consequence of design, operational or regulatory constraints. These assessments are not possible with the state-of-the-art aero-engine preliminary design simulation tools. Novel 0-D performance models for counter-rotating propellers (CRPs) and differential planetary gearboxes, as well as 1-D and 0-D performance models for counter-rotating turbines (CRTs) were developed and verified using available data. These models were used to create 0-D pusher geared (GOR) and direct drive (DDOR) open rotor engine performance simulation modules allowing the independent definition of the design and operation of each of the two counter-rotating parts of the CRP and CRT. A multi-disciplinary preliminary design simulation framework was built using the novel engine performance modules together with dedicated CROR aircraft performance, engine geometry and weight, gaseous emissions and certification noise simulation modules. Design space exploration and trade-off studies were performed and minimum fuel burn design regions were identified for both the pusher GOR and DDOR. A 160 PAX aircraft flying a business mission of 500 NM was chosen for these studies. Based on the assumptions made, the main conclusions of these studies are as follows. · Fuel burn reductions of ~1-2% are possible through optimised propeller control · The propeller diameter for minimum mission fuel burn lies between 4.26 and 4.7 m · The design nozzle pressure ratio for minimum mission fuel burn lies between 1.55 and 1.6 · CRPs with 13 or 14 blades per propeller provide minimum mission fuel burn · Increasing spacing between the propellers reduces noise significantly (~6 EPNdB for each certification point) with a relatively small fuel burn penalty (~0.3-0.5%) · Relative to unclipped designs, 20% clipped CRPs reduce flyover noise by at least 2.5 EPNdB and approach noise by at least 4.5 EPNdB. The corresponding fuel burn penalty is ~2 % for a GOR and ~3.5% for a DDOR. · Sideline and flyover noise can be reduced by increasing the diameter of the CRP and appropriately controlling CRP rotational speeds. Approach noise can be reduced by either reducing the diameters or the rotational speeds of the propellers. · The rotational speed of the forward propeller for minimum noise is higher than that for minimum mission fuel burn for all the studied CROR designs. · Regardless of clipping, reducing the rotational speed of the rear propeller relative to the forward propeller reduces noise and, to a certain limit, also mission fuel burn. (further reductions in rotational speed would have an adverse effect on fuel burn) · An increase in the number of blades results in an increase in certification noise. The main recommendations for further work are as follows. · Integrating the 1-D CRT model with the 0-D DDOR performance model in order to assess the impact of different CRT design criteria at engine and mission levels · Developing preliminary design methods to account for changes in aircraft weight and aerodynamics due to changes in engine design and required cabin noise treatment

Racing car coastdown analysis

Coastdown testing is a proven method for the determination of vehicle drag coefficients for road cars whilst the vehicle is in its normal operating environment. A method of achieving this has been successfully developed at Loughborough University of Technology over the past few years. This study is concerned with the adaptation of the technique to the specific application of a contemporary Formula One racing car, this work was undertaken in conjunction with the Benetton Formula One racing team. [Continues.

An investigation into hybrid power trains for vehicles with regenerative braking

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Bearing signal separation enhancement with application to helicopter transmission system

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Bearing vibration signal separation is essential for fault detection of gearboxes, especially where the vibration is nonstationary, susceptible to background noise, and subjected to an arduous transmission path from the source to the receiver. This paper presents a methodology for improving fault detection via a series of vibration signal processing techniques, including signal separation, synchronous averaging (SA), spectral kurtosis (SK), and envelope analysis. These techniques have been tested on experimentally obtained vibration data acquired from the transmission system of a CS-29 Category A helicopter gearbox operating under different bearing damage conditions. Results showed successful enhancement of bearing fault detection on the second planetary stage of the gearbo

Power transmission systems: from traditional to magnetic gearboxes

L'abstract è presente nell'allegato / the abstract is in the attachmen