The aerothermodynamic cycle optimal design of a turbofan engine

To ensure that the aerothermodynamic cycle design of a turbofan engine is more accurate, efficient, and provide a reliable decision-making basis for engine designers, the multi-objective particle swarm optimization (MOPSO) method was used to optimize the aerothermodynamic performance parameters of the turbofan engine at multiple design points (MDPs). Fuel consumption rate and the specific thrust were considered as optimization targets. The thrust requirements and cycle parameter constraints under each working state were comprehensively considered to obtain the optimal performance boundary of the engine, the corresponding cycle parameters, and the correlations between different requirements and constraints. The results showed that the MOPSO algorithm could accurately and completely obtain the optimal performance boundary surface of the engine in the feasible region and the corresponding cycle parameter value. The feasible region obtained by the aerothermodynamic cycle design at MDPs was more accurate and effective than the design at a single design point.

Estimation of the vitrified canister production for a PWR fleet with the CLASS code

This article presents an assessment of fuel cycle parameter impact on waste production through the prism of vitrified container and minor actinide masses, using a scenario simulated with the CLASS code. The number of canister introduces a new focus on waste production estimation for a nuclear fleet, as it helps to set the repository size for deep geological disposal of high level waste. To evaluate the number of canisters, dedicated developments to model a simplified waste vitrification unit in the CLASS package are presented. It relies on artificial neural network estimations of decay heat, α radiation and mass content, for different material flow coming from reprocessing and sent to vitrification. Then, the studied scenario considers a transition from a PWRs plutonium mono-recycling fleet to a plutonium multi-recycling fleet. Vitrified waste container production is calculated as a function of different material reprocessing options. Simulations shows that up to 19% variation may be observed (in 2060) in canisters’ total number depending on the different assumptions. Impact of vitrification parameters such as the size of buffer before vitrification is also analysed and the importance of mixing material coming from MOX and MIX spent fuels with material from UOX spent fuels is clearly established.

A Study of Two Variable Cycle Engine Concepts for High Speed Civil Aircraft

High speed civil aircraft has become a promising field with the development of globalization. The propulsion system is an indispensable part of the aircraft. Conventional engines have difficulty meeting the performance requirement of the high-speed civil aircraft. In this article, two variable cycle engines were studied to preliminarily as aircraft propulsion system. Their performance and matching mechanism were analyzed and compared with each other. Firstly, the cycle parameters design was conducted to explain the principle of cycle parameter determination for the high-speed civil aircraft. Secondly, the control law of variable geometry components was studied to optimize engine performance during supersonic cruising. Finally, the throttling process with constant airflow was studied to solve the problem of thrust surplus during subsonic cruising. According to this study, given same cycle parameters, the engine with variable fan stage can produce equal or slightly higher thrust with slightly less fuel consumption than the engine with core-driven-fan stage. The engine with core-driven-fan stage has advantages in aero-dynamical stabilities. It can also throttle to slightly lower thrust level during subsonic cruising. Considering the advantages in performance and derived development comprehensively, the engine with variable fan stage is a better option for high speed civil aircraft.

Thermodynamic Design of a Small-Scale Gas Turbine Engine Family

The paper presents a procedure for selecting work cycle parameters and describes thermodynamic design of a small-scale gas turbine engine family consisting of a small-scale gas turbine engine and a gas turbine plant comprising a free turbine driving a power generator, on the basis of a standardized gas generator. In order to select reasonable work cycle parameter values for the small-scale gas turbine engine and gas turbine plant we used a non-linear optimisation technique accounting for functional and parametric constraints as implemented in the ASTRA CAE software. Calculation results allowed us to plot the locally optimal work cycle parameter regions for the small-scale gas turbine engine and gas turbine plant according to the efficiency criteria for both engines, which are specific fuel consumption and net energy conversion efficiency. Taking the constraints into account, we selected reasonable values for the standardized gas generator parameters within the compromise region obtained, specifically the turbine inlet temperature and compressor pressure ratio. Our quantitative results show how the efficiency indices decline in the engine family featuring a standardized gas generator as compared to engines equipped with individually tailored gas generators. Designing a standardized gas generator in advance makes it possible to decrease engine development costs and time, ensure a higher reliability and a lower cost of production.

The duty cycle in Functional Electrical Stimulation research. Part II: Duty cycle multiplicity and domain reporting

In part I of this review, we introduced the duty cycle as a fundamental parameter in controlling the effect of electrical stimulation pulse trains on muscle structural and functional properties with special emphasis on fatigue. Following on from a survey of the literature, we discuss here the relative ability of intermittent and continuous stimulation to fatigue muscle. In addition, pertinent literature is explored on a more deeper level, highlighting contentions regarding the duty cycle across studies. In response to literature inconsistencies, we propose frameworks upon which the duty cycle parameter may be specified. We present the idea of domain reporting for the duty cycle, and illustrate with practical examples. In addition we dig further into the literature and present a set of notations that have been used by different researchers to report the duty cycle. We also propose the idea of the duty cycle multiple, which together with domain reporting, will help researchers understand more precisely duty cycles of electrical stimulation. As a case study, we also show how the duty cycle has been looked at by researchers in the context of pressure sore attenuation in patients. Together with part I, it is hoped that the frameworks suggested provide a complete picture of how duty cycle has been discussed across the literature, and gives researchers a more trans-theoretical basis upon which they may report the duty cycle in their studies. This may also lead to a more precise specification of electrical stimulation protocols used in patients.