Improving sustainability with simpler alloys Li, Xiuyan; Lu, K
Science (American Association for the Advancement of Science),
2019-May-24, 2019-05-24, 20190524, Letnik:
364, Številka:
6442
Journal Article
Recenzirano
The high performance of alloy materials can be maintained with compositional “plainification”
The hardening of copper by alloying with tin and lead in the Early Bronze Age (∼4000 BCE) is one of the ...earliest recorded examples of improving material performance by tailoring composition. Today, many high-performance applications, from jet engines to computer chips, use alloys that may contain almost any element in the periodic table. However, increasing the number of components in alloyed materials makes their production and recycling more difficult and comes at the risk of resource exhaustion of scarce or rare-to-source elements. The associated increase in material costs may lead to only modest property enhancements. The sustainability of alloying-based strategies is part of a general problem for many materials systems (
1
). Substantial efforts have focused on reducing alloying, especially substituting toxic and rare-to-source elements in materials, as exampled by initiatives such as the Element Strategy Initiative in Japan, started in 2008, and the “plainification of materials” in China, effective in 2018.
•Hybrid systems combining batteries, fuel cells, jet engines are proposed.•The reduction rate of fuel cell weight slows with decreasing fuel utilization.•The endurance is 19.6 h with specific fuel ...consumption of 15.32 g/s/kN.•The flight envelops are limited by the force balance and fuel cell temperature.•The weight ratios of fuel cells, motors and batteries are 15%, 12% and 8%.
Hybridization of power sources by combining their performance advantages and balancing disadvantages is becoming a feasible solution during the process of designing electricity propulsion systems on aircraft. Novel hybrid propulsion and power (HPP) systems combining batteries, fuel cells, jet engines are proposed in this paper, which can respectively provide high thrust and low thrust specific fuel consumption in the take-off and cruise segment. The mathematical models are built and the main parts are validated to determine the performance and size parameters of these components. The main conclusions are as follows: (1) Under the cruise segment, the reduction rate of fuel cell weight slows with decreasing fuel utilization. Meanwhile, the thrust and thrust specific fuel consumption are both increased. These values of 4 kN and 15.32 g/s/kN are reached to achieve the endurance of 19.6 hours. (2) The speed characteristic of the HPP system is complicated, but the thrust of the system is almost only affected by air mass flow with varying altitudes. It can vary from 100% to about 50% by adjusting the fuel flow rate in the afterburner. (3) The flight envelop of the aircraft are limited by the thrust/drag balance and fuel cell operating temperature. The highest operating altitude is about 27.5 km, with a maximum working Mach number of 1.8. (4) The weight ratios of the fuel cell, motor, battery, and fuel loaded are 15%, 12%, 8%, and 56%. Most of the fuel (89%) is consumed in the cruise segment.
To understand the elemental characteristics of the exhaust particles from a jet aircraft, we performed an element analysis using an in-air PIXE system of the different lubrication oils of a jet ...engine (Mobil Jet Oil II, Mobil Jet Oil 254 and Eastman Turbo Oil 2380) and the jet fuel (JET A-1) to determine the effects on the exhaust particles. A high concentration (1,400–2,500 wt.-ppm) of P was detected from the analyzed three oil samples. The high concentration of P is probably due to the tricresyl phosphate (TCP: C
2
1
H
2
1
O4P) contained in the oil samples. The S concentrations of the JET A-1 fuel samples with different collection dates were in the range of
<
10 to 530 wt.-ppm. These results aid in determining the component features of nanoparticles emitted from an aircraft.
We describe results of in situ observations of a 1‐ to 2‐min‐old contrail in the vortex phase generated from soot‐rich exhaust (>1015 emitted soot particles per kilogram of fuel burned). Simultaneous ...measurements of soot (EIsoot) and apparent ice (AEIice) particle number emission indices show a pronounced anticorrelation in the vertical contrail profile. AEIice decrease by about 75% with increasing distance below the contrail‐producing aircraft, while EIsoot increase by an equivalent relative fraction, therefore strongly suggesting ice particle formation to be soot‐controlled and losses to be caused by sublimation. Quantifying these losses in measurements helps to validate and improve contrail parameterizations used to estimate the climate impact of contrails and contrail cirrus. Our study further demonstrates the challenges in the performance and interpretation of particle measurements in young contrails and lends itself to suggestions for improving contrail data evaluation.
Plain Language Summary
Detailed understanding of climatic effects of aircraft contrails and the clouds evolving from them requires accurate in situ measurements. We took measurements in a young persistent contrail that formed at 10 km altitude. We found that a substantial fraction of contrail ice particles is lost shortly after they formed from emissions of copious soot particles from aircraft jet engines. While these results are not entirely unexpected and can be explained by sublimation associated with adiabatic heating in descending aircraft wake vortices, experimental verification is challenging. Importantly, our results increase confidence in the current understanding of processes governing contrail ice formation, growth, and sublimation during early development stages. We provide guidance on quantifying ice particle number concentrations in young contrails and how to relate them to particle emissions. We expect our results to be also beneficial to future studies addressing properties and climate impact of contrails originating from using alternative jet fuels or novel engine technologies.
Key Points
Results of aircraft measurements of microphysical properties in a young, soot-rich contrail are presented
We found a pronounced reduction of ice particle numbers in lower wake regions
Vertical profiles of soot and ice particle numbers are consistent with soot-controlled ice formation
The Hotter the Engine, the Better Perepezko, John H.
Science (American Association for the Advancement of Science),
11/2009, Letnik:
326, Številka:
5956
Journal Article
Recenzirano
Alloys based on molybdenum or niobium may allow the high-temperature components of jet engines to run hotter and more efficiently.
Jet turbine engines have benefited from decades of development of ...nickel-based superalloys, which have allowed a steady increase in engine operating temperatures and led to improved performance and efficiency. However, operating temperatures are now reaching limits posed by the melting temperatures (
T
m
) of these materials. New materials, including alloys based on metals with higher melting points, such as molybdenum (Mo) and niobium (Nb) alloyed with silicon (Si), are now being seriously examined as alternatives by academic and industrial groups.
In this paper, a neural network-based fault detection and isolation (FDI) scheme is presented to detect and isolate faults in a highly nonlinear dynamics of an aircraft jet engine. Towards this end, ...dynamic neural networks (DNN) are first developed to learn the input–output map of the jet engine. The DNN is constructed based on a multi-layer perceptron network which uses an IIR (infinite impulse response) filter to generate dynamics between the input and output of a neuron, and consequently of the entire neural network. The trained dynamic neural network is then utilized to detect and isolate component faults that may occur in a dual spool turbo fan engine. The fault detection and isolation schemes consist of multiple DNNs or parallel bank of filters, corresponding to various operating modes of the healthy and faulty engine conditions. Using the residuals that are generated by measuring the difference of each network output and the measured engine output various criteria are established for accomplishing the fault diagnosis task, that is addressing the problem of fault detection and isolation of the system components. A number of simulation studies are carried out to demonstrate and illustrate the advantages, capabilities, and performance of our proposed fault diagnosis scheme.
•It is important to study the interpretability of prognostics models.•We analyze the interpretability of Linear Regression, Multi-Layer Perceptron, and Echo State Network.•SHAP values are monotonic, ...trendable, and prognosable.
Maintenance decisions in domains such as aeronautics are becoming increasingly dependent on being able to predict the failure of components and systems. When data-driven techniques are used for this prognostic task, they often face headwinds due to their perceived lack of interpretability. To address this issue, this paper examines how features used in a data-driven prognostic approach correlate with established metrics of monotonicity, trendability, and prognosability. In particular, we use the SHAP model (SHapley Additive exPlanations) from the field of eXplainable Artificial Intelligence (XAI) to analyze the outcome of three increasingly complex algorithms: Linear Regression, Multi-Layer Perceptron, and Echo State Network. Our goal is to test the hypothesis that the prognostics metrics correlate with the SHAP model's explanations, i.e., the SHAP values. We use baseline data from a standard data set that contains several hundred run-to-failure trajectories for jet engines. The results indicate that SHAP values track very closely with these metrics with differences observed between the models that support the assertion that model complexity is a significant factor to consider when explainability is a consideration in prognostics.
•Spray performance of GTL and Jet A-1 fuels are different at hot ambient conditions.•Far-field spray cone angle of GTL fuel is higher than that of the Jet A-1 fuel.•Liquid sheet breakup dynamics of ...GTL fuel is different from Jet A-1 fuel.•Spray velocities are comparable between the GTL and Jet A-1 fuels.
Gas-to-liquid (GTL) jet fuel, a liquid fuel synthesized from natural gas, has recently gained significant global attention due to its cleaner combustion characteristics when compared to the conventional jet fuels. The critical physical and chemical properties of GTL fuels are different from those of the conventional fuels, which in turn, influence the atomization, combustion, and eventually, the emission characteristics of the fuel in a jet engine. To this end, this work investigates the non-reacting near-nozzle spray performance of GTL and conventional Jet A-1 fuels using a pressure-swirl nozzle at elevated ambient conditions, which are relevant to practical combustors in a jet engine. The macroscopic spray features, such as spray cone angle, liquid sheet dynamics, and the sheet velocity, are determined using the high-speed imaging and shadowgraph technique. The ambient gas pressure is varied from 100 to 1300 kPa, and the ambient gas temperature is varied from 300 to 375 K, while the pressure difference across the nozzle is kept constant, in order to study their effect on the spray characteristics. The results show that the ambient gas pressure has a significant impact on the spray dynamics when compared to that of the ambient gas temperature, in the range examined in this work. The comparison of macroscopic spray results between the conventional and alternative jet fuels shows that the far-field spray cone angle for the GTL jet fuel is higher than those of the Jet A-1 fuel. Furthermore, in the near nozzle region, the sheet breakup region for the GTL jet fuel is slightly longer than that of the conventional fuel under the conditions studied.
PDF
