Search

In this paper, a multi-objective optimization strategy for efficient design of turbomachinery blades using sparse active subspaces is implemented for a turbofan stage design. The proposed strategy utilized sparse polynomial chaos expansion on a limited dataset to generate a function from which the differential and the covariance matrix can be obtained. Active subspace was used to compute the active variables via singular value decomposition and a hybrid polynomial correlated function expansion was used to construct a surrogate model on the active subspace. Coupled with freeform method and multi-objective genetic algorithm, an automated optimization loop was run at a single operating condition. An improvement in stage efficiency and total pressure ratio of 2.97% and 1.15% was achieved for the optimum design compared with the baseline. Additionally, total pressure loss coefficient decreased by 5.88%, exit flow angle by 34.65% and shock strength by 5.32%. The coupled effect of change in stagger angle, forward sweep, forward lean, and chord length reduced the recirculation at the hub, and blockage at the shroud due the tip leakage flow by decreasing the blade loading. The threshold value hyperparameter was found to be the most influential and must be accurately determined. [ABSTRACT FROM AUTHOR]

In a time when low emission solutions and technologies are of utmost importance regarding the sustainability of the aviation sector, this publication introduces a reduced-order physics-based model for combustion chambers of aeroengines, which is capable of reliably producing accurate pollutant emission and combustion efficiency estimations. The burner is subdivided into three volumes, with each represented by a single perfectly stirred reactor, thereby resulting in a simplified three-element serial chemical reactor network configuration, reducing complexity, and promoting the generality and ease of use of the model, without requiring the proprietary engine information needed by other such models. A tuning method is proposed to circumvent the limitations of its simplified configuration and the lack of detailed geometric data for combustors in literature. In contrast to most similar frameworks, this also provides the model with the ability to simultaneously predict the combustion efficiency and all pollutant emissions of interest ( N O x , C O and unburnt hydrocarbons) more effectively by means of implementing a detailed chemical kinetics model. Validation against three correlation methods and actual aeroengine configurations demonstrates accurate performance and emission trend predictions. Integrated within two distinct combustion chamber low-emission preliminary design processes, the proposed model evaluates each new design, thereby displaying the ability to be employed in terms of optimizing a combustor's overall performance given its sensitivity to geometric changes. Overall, the proposed model proves its worth as a reliable and valuable tool for use towards a greener future in aviation. [ABSTRACT FROM AUTHOR]

A very fast reduced order model is developed to monitor aeroengines condition (defining their degradation from a baseline state) in real time, by using synthetic data collected in specific sensors. This reduced model is constructed by applying higher-order singular value decomposition plus interpolation to appropriate data, organized in tensor form. Such data are obtained by means of an engine model that takes the engine physics into account. Thus, the method synergically combines the advantages of data-driven (fast online operation) and model-based (the engine physics is accounted for) condition monitoring methods. Using this reduced order model as surrogate of the engine model, two gradient-like condition monitoring tools are constructed. The first tool is extremely fast and able to precisely compute the turbine inlet temperature 'on the fly', which is a paramount parameter for the engine performance, operation, and maintenance, and can only be roughly estimated by the engine instrumentation in civil aviation. The second tool is not as fast (but still reasonably inexpensive) and precisely computes both the engine degradation and the turbine inlet temperature at which sensors data have been acquired. These tools are robust in connection with random noise added to the sensor data and can be straightforwardly applied to other mechanical systems. [ABSTRACT FROM AUTHOR]

As a successful engineering entrepreneur, William Weir took on government positions in the First World War and played a leading role in increasing British aircraft production in 1917–1918. The British Cabinet believed at the time that his policies were highly effective, a conclusion picked up in later historiography that dubbed him the 'architect of air power', responsible for 'dazzling' production results. This article looks afresh at Weir's aeronautical career in the First World War, and highlights hitherto neglected quality problems with British aeroengines, and cost overruns in airframe production, which heavily qualify the apparently high levels of aircraft production attributed to him. [ABSTRACT FROM AUTHOR]

In a time when low emission solutions and technologies are of utmost importance regarding the sustainability of the aviation sector, this publication introduces a reduced-order physics-based model for combustion chambers of aeroengines, which is capable of reliably producing accurate pollutant emission and combustion efficiency estimations. The burner is subdivided into three volumes, with each represented by a single perfectly stirred reactor, thereby resulting in a simplified three-element serial chemical reactor network configuration, reducing complexity, and promoting the generality and ease of use of the model, without requiring the proprietary engine information needed by other such models. A tuning method is proposed to circumvent the limitations of its simplified configuration and the lack of detailed geometric data for combustors in literature. In contrast to most similar frameworks, this also provides the model with the ability to simultaneously predict the combustion efficiency and all pollutant emissions of interest (NOx, CO and unburnt hydrocarbons) more effectively by means of implementing a detailed chemical kinetics model. Validation against three correlation methods and actual aeroengine configurations demonstrates accurate performance and emission trend predictions. Integrated within two distinct combustion chamber low-emission preliminary design processes, the proposed model evaluates each new design, thereby displaying the ability to be employed in terms of optimizing a combustor’s overall performance given its sensitivity to geometric changes. Overall, the proposed model proves its worth as a reliable and valuable tool for use towards a greener future in aviation.

A very fast reduced order model is developed to monitor aeroengines condition (defining their degradation from a baseline state) in real time, by using synthetic data collected in specific sensors. This reduced model is constructed by applying higher-order singular value decomposition plus interpolation to appropriate data, organized in tensor form. Such data are obtained by means of an engine model that takes the engine physics into account. Thus, the method synergically combines the advantages of data-driven (fast online operation) and model-based (the engine physics is accounted for) condition monitoring methods. Using this reduced order model as surrogate of the engine model, two gradient-like condition monitoring tools are constructed. The first tool is extremely fast and able to precisely compute the turbine inlet temperature ‘on the fly’, which is a paramount parameter for the engine performance, operation, and maintenance, and can only be roughly estimated by the engine instrumentation in civil aviation. The second tool is not as fast (but still reasonably inexpensive) and precisely computes both the engine degradation and the turbine inlet temperature at which sensors data have been acquired. These tools are robust in connection with random noise added to the sensor data and can be straightforwardly applied to other mechanical systems.

As the core process of case-based reasoning (CBR), case retrieval is the foundation for CBR success, and the quality of case retrieval depends on the case similarity measure. We improved the CBR system for aeroengine fault diagnosis by embedding the attitudinal Choquet integral (ACI) and 2-order additive measure to consider attribute interactions and decision makers' attitudes. The enhanced case retrieval method can not only integrate the local similarity, attribute importance, and interaction between attributes, but also incorporate the attitude of the decision maker, thus producing more comprehensive and reasonable global similarity and high-quality recommendations. An experimental study of aeroengine fault diagnosis and comparisons with other similarity aggregation methods were performed to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

As the core process of case-based reasoning (CBR), case retrieval is the foundation for CBR success, and the quality of case retrieval depends on the case similarity measure. We improved the CBR system for aeroengine fault diagnosis by embedding the attitudinal Choquet integral (ACI) and 2-order additive measure to consider attribute interactions and decision makers’ attitudes. The enhanced case retrieval method can not only integrate the local similarity, attribute importance, and interaction between attributes, but also incorporate the attitude of the decision maker, thus producing more comprehensive and reasonable global similarity and high-quality recommendations. An experimental study of aeroengine fault diagnosis and comparisons with other similarity aggregation methods were performed to demonstrate the effectiveness of the proposed method.

Nowadays, there is an ever growing interest for gas turbine and aeroengines prognostics. The capability to assess not only the current state of an asset, but also to be able to predict its remaining useful life (RUL), and hence to perform condition-based maintenance (CBM) —if, and only when, it is needed— can represent a huge deal in the manufacturer profits. Against the plethora of data-driven methods that have arisen in the past few years, there is still some knowledge to be gained in terms of understanding the underlying phenomenology of engine degradation. In fact, it is certainly a non-trivial problem, to realize what has happened to the rotating components of an engine just by observing the pressure being measured by certain sensor rise, or some other temperature measured along the main gas-path decrease its value. In this regard, model-based approaches —and, in particular, gas path analysis (GPA)— can assist us in gaining such knowledge. In this paper, a non-linear GPA technique is revisited, introducing some novelties to the solver, and making use of current computational methods and resources, to establish a solid 'foundation' that will serve as the basis for further research. [ABSTRACT FROM AUTHOR]

This study aims to minimize the mechanical, chemical and thermal damages on the blades of a compressor used in aerospace engines by developing a superhydrophobic coating on the blade surface. In the absence of any information in open literature for the fabrication of such coatings, an one-step plasma spray process was implemented. For this, a well mixed powder of Ni and Ti was used as feedstock material. The superhydrophobicity characteristic of the coating was confirmed by the measurement of the contact (165°) and sliding angles (8 ± 1°) by the sessile drop technique. The adhesion test of the coating showed the high force of adhesion at the interface with a failure limit of 40.85 MPa. Furthermore, the abrasion test depicted an excellent abrasion resistance of the coating. These two investigations indicated that the coatings had a very high mechanical durability. The coatings also showed an excellent thermal stability up to 400 °C. Beyond this temperature (at 600 and 900 °C), the superhydrophobic characteristic changed for hydrophobic. The pH and corrosion tests were also performed to assess the chemical stability of coatings. They showed that the coatings retained the superhydrophobic property for pH ranging between 9.5 and 2.4. Beyond this range, at pH = 10 and pH = 2, the contact angles were 138° and 143°, respectively. In addition, the coatings exhibited a better corrosion resistance than the substrate and coatings developed by using other deposition techniques. [ABSTRACT FROM AUTHOR]

• A cross-disciplinary assessment method is built by stochastic dynamics and thermodynamics. • Stochastic dynamics is first used to improve the assessment accuracy in a onboard aeroengine. • A full-dimensional observation equation is given through complete theoretical deduction. • Optimal operation inputs for degraded aeroengines are constructed by mechanism and data. • The proposed method is free from multi-source uncertainty interference and has higher accuracy. Gas path deterioration seriously reduces the reliability of aeroengine systems. Accurate observation of gas path deterioration parameters is the key to ensuring the reliable operation and safety control of aeroengines. It is a significant challenge to accurately observe the deterioration state under multi-source uncertainties. This work provides a novel assessment technique to accurately master the gas path deterioration from the perspective of stochastic dynamics for the first time, in contrast to the previous assessment schemes based on the aerothermodynamics model and filtering theory. Based on the state parameters and stochastic optimal inputs, a full-dimensional performance observation equation is created. The construction of the stochastic optimal inputs ensures the tracking of the gas path deteriorating state through the negative feedback of state parameters and the rectification of measurement data. The observation principle and algorithm are also thoroughly presented. Three common deterioration modes serve as proof of the proposed method's effectiveness. The evaluation accuracy is increased by at least 22.75% when compared to the conventional method, and the maximum improvement rate reaches 52.45%. The proposed method is free from multi-source uncertainty interference and has higher accuracy and robustness. It offers a fresh approach to master gas path deterioration and ensures safe and reliable operation. [ABSTRACT FROM AUTHOR]

The effects of heat loss on the structure of laminar flamelets, which are the constitutive elements of turbulent flames under the most common operating conditions, are investigated for typical aeronautical gas-turbine operating conditions at take-off. The magnitude of heat loss is quantified via the 'enthalpy defect' measured with respect to an adiabatic flame. A procedure to generate laminar flamelets with an assigned enthalpy defect at the boundaries is devised and applied to nonpremixed propane/air flames, as propane reproduces the essential features of higher hydrocarbon combustion. It is found, contrary to commonly held beliefs, that the enthalpy defect has a significant effect on the concentration not only of minor species, but also of main reaction products. Such effects are found in general to be more pronounced for fuel-rich conditions. An impact is anticipated on the formation rate of nitric oxides. The effects of scalar dissipation rate are also discussed. [ABSTRACT FROM AUTHOR]

This study is concerned with the thrust regulation and safety protection problem for aeroengines, and a state-based switching control strategy is proposed. Specifically, the multiloop switching control framework of aeroengines is first presented, and the framework is based on switching logic and bumpless transfer. Then for the key technologies, a switching logic design that can determine which candidate controller should be put in feedback loop with the plant to achieve a desired regulation or protection performance is given. Moreover, an extended bumpless transfer design is developed for the switched system with time-varying delay and external disturbance, which can ensure that the aeroengine multiloop system performs a smooth transition at the subcontroller transfer moment. Finally, the proposed switching control strategy is applied to an aeroengine control model. As a case study, the simulations are performed to show an excellent thrust regulation and over-temperature protection performance. [ABSTRACT FROM AUTHOR]

Lean direct injection (LDI) is one of the most promising low NOxcombustion concepts for aero-engines. This work reports turbulent reacting spray modeling in a single-element LDI combustor to determine a validated numerical framework that can be used to model such complex combustion systems involving highly swirling flows, droplet breakup, and combustion. Different sub-models are employed within a numerical framework to characterize the spray processes involved in the primary atomization and secondary breakup regimes. The sensitivity of the associated breakup model parameters to the predicted behavior is investigated, thereby fine tuning the sub-models for turbulent spray combustion in LDI. The two-way coupling accomplishes the interactions between the liquid and gas phases and the respective phase properties are analyzed. The size and distribution of drops are computed at various locations and the results are compared with the measurements. The work demonstrates that modeling of primary atomization improves the overall predictions of both gas phase and spray. The validation with the measurements reflects that the numerical framework implemented in this study is able to characterize the effects of highly swirling flows with strong turbulence on spray velocity and size distribution, and strong momentum exchange between the gas and liquid phases. [ABSTRACT FROM AUTHOR]

In order to experimentally study the cooling characteristics of different compound cooling configurations in reverse flow combustor, three kinds of compound cooling configurations are designed. The research results from the experimental study for the test pieces show that; (1) There is an obvious effect of the blowing ratio on the cooling effectiveness, the bigger the blowing ratio, the better the cooling effectiveness. (2) Different cooling configurations show different cooling characteristics in the different section of reverse flow combustor. (3) For the reverse flow combustor, the cooling effectiveness of impingement+reversed convection+film cooling configuration and impingement+cocurrent convection+film cooling configuration have a great change. However, the cooling effectiveness change of impingement+effusion configuration is smooth, which means the temperature of reverse flow combustor is more even than that of the other cooling configurations. [ABSTRACT FROM AUTHOR]

Advances in the efficiency of the aeroengine have led to an increase in combustion and exhaust gas temperatures. Although superalloys have been developed to withstand these high temperatures, additional cooling of the components is often necessary. This is achieved through thousands of closely spaced cooling holes drilled into the components. Laser drilling offers economical advantages over other non-conventional drilling techniques (e. g. electrical discharge machining). The key limitations and the areas requiring further investigation to develop the laser drilling process to meet future aeroengine requirements have been identified. Principal areas include the development and investigation of laser barrier methods when drilling through increasingly complicated and smaller cavities, the successful drilling of lower angled effusion holes and the increased use of laser drilling to produce the cooling holes in rotating components. More recent designs of the aeroengine have incorporated thermal barrier coatings, sprayed onto the components to further protect against high temperatures. Successful laser drilling through these coatings, with particular attention to preventing spalling of the coatings also requires more research. Each of these areas will need to be addressed while, at the same time, decreasing the overall drilling times. [ABSTRACT FROM AUTHOR]