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The aircraft is subjected to high-temperature and high-pressure conditions during flight, which renders it susceptible to the occurrence of creep phenomenon. Several academics have conducted extensive research on this issue. This research paper provides a comprehensive overview of the existing literature on creep phenomena in aircraft engines. First, several classical creep calculation models are enumerated and categorized as creep life calculation, creep-fatigue life calculation, and creep deformation calculation. Studies on creep phenomena are conducted in various components of aircraft engines, such as the engine’s turbine blades, turbine disks, and combustion chambers. The creep behavior of turbine blades in aircraft engines has been extensively researched. Furthermore, the protective measures aimed at mitigating creep are presented. Materials with high creep resistance can be used, and alternative fuels could be implemented. This paper provides an in-depth analysis of the advantages of creep in aircraft, presented in a favorable perspective. Finally, the prospective future research direction is discussed.

Polymer‐based membrane technology holds immense promise for CO2 separation. However, it faces persistent challenges, including the high CO2 pressure‐induced plasticization and permeability‐selectivity trade‐offs, which significantly hinder the development of polymeric membranes. To tackle this issue, we synthesized a novel polyimide 6FDA‐DAT:DABA(6FDD) containing triptycene and carboxylic groups. Upon de‐carboxylation induced cross‐linking, the membrane demonstrated a simultaneous enhancement of gas permeability and selectivity. Specifically, compared to the uncross‐linked 6FDD, the 400°C‐24 h cross‐linked membrane exhibited a remarkable increase in CO2 permeability by 177% (93.1 Barrer) and a significant rise in CO2/CH4 selectivity by 47% (57.5), reaching the CO2/CH4 upper bound. More importantly, the cross‐linked membrane displayed vastly improved CO2 plasticization resistance, withstanding up to 42 bar of CO2 feed pressure. The design of decarboxylated cross‐linked membranes in this work paves the way for creating high‐performing and plasticization‐resistant membranes with potential applications in high‐pressure CO2 separations. [ABSTRACT FROM AUTHOR]

Influenced by topography, geological conditions, and environmental factors, the alignment design of long‐distance tunnels frequently incorporates curved tunnel segments. When subjected to obliquely incident transverse SV seismic waves, curved tunnels exhibit more complex patterns of stress and deformation, which could become pivotal in governing the seismic safety of the tunnel compared to their straight counterparts. This paper presents a numerical simulation on the response characteristics of curved tunnels subjected to obliquely incident lateral seismic SV waves. Curved tunnels exhibit more complex deformation under oblique SV wave incidence compared to vertical incidence, with notable increases in axial tensile deformation and shear deformation, both axially and in‐plane, as the angle of incidence rises. While vertical incidence primarily induces lateral bending, oblique incidence results in bending influenced by both wave direction and incidence angle, necessitating advanced seismic design considerations for tunnel integrity. The bending moment distribution in curved tunnels under oblique incidence displays nonuniformity and localized concentration. The findings underscore the importance of considering the oblique incident angle in the design and analysis of curved tunnels for seismic safety. [ABSTRACT FROM AUTHOR]

This study presents a novel cooling-power-desalination combined cycle for recovering shipboard diesel exhaust heat, integrating a freezing desalination sub-cycle to regulate the ship's cooling-load fluctuations. The combined cycle employs ammonia–water as the working fluid and efficiently utilizes excess cooling capacity to pretreat reverse osmosis desalination. By adjusting the mass flow rate of the working fluid in both the air conditioning refrigeration cycle and the freezing desalination sub-cycle, the combined cycle can dynamically meet the cooling-load demand under different working conditions and navigation areas. To analyze the cycle's performance, a mathematical model is established for energy and exergy analysis, and key parameters including net output work, comprehensive efficiency, and heat exchanger area are optimized using the MOPSO algorithm. The results indicate that the system achieves optimal performance when the generator temperature reaches 249.95 °C, the sea water temperature is 22.29 °C, and 42% ammonia–water is used as the working fluid. Additionally, an economic analysis of frozen seawater desalination as RO seawater desalination pretreatment reveals a substantial cost reduction of 22.69%, showcasing the advantageous features of this proposed cycle. The research in this paper is helpful for waste energy recovery and sustainable development. [ABSTRACT FROM AUTHOR]

The ignition and flame propagation in an axisymmetric supersonic combustor were investigated. The laser-induced plasma was employed to ignite the supersonic inflow with a speed of Mach 2.5 and a total temperature of 1486 K. A direct-connect axisymmetric model scramjet with a fully transparent glass combustor was built, which enabled the circumferential and axial flame propagation in the cavity-based axisymmetric supersonic combustor to be visualized by the high-speed photography from the endoscopic and external views, respectively. An initial flame kernel is produced by the laser-induced plasma and propagates to the cavity leading edge along the axial direction. The establishment of the cavity shear-layer flame facilitates circumferential flame propagation. The circumferential flame propagation is coupled with the axial propagation, eventually generating a loop-shaped flame with a central-hole. Acceleration of the flame propagation can be observed, especially when the global equivalence ratio is increased. A plausible explanation for the flame propagation in the axisymmetric supersonic combustor was found using URANS numerical simulation. The axisymmetric cavity generates a low-speed loop-shaped recirculation region and thickened cavity shear-layer with an appropriate local equivalence ratio, resulting in the simultaneous axial and circumferential flame propagation. The increased temperature in the cavity and the thickened cavity shear-layer during the flame propagation produce a more intense heat release and mass transfer, leading to faster flame propagation. [ABSTRACT FROM AUTHOR]

Plasma-assisted combustion (PAC) has shown excellent performance in the ignition and combustion enhancement of scramjet combustors. A multi-channel gliding arc (MCGA) plasma placed on the sidewall surface of a scramjet combustor was employed to enhance combustion near the flame blowout limit (BL) in a C 2 H 4 -fueled and cavity-based model scramjet combustor. Wall static pressure measurements, simultaneous 10 kHz CH* chemiluminescence imaging from the top and side views, optical emission spectroscopy, and discharge waveform measurements were used to elucidate the combustion physics throughout the PAC events. For the current cavity configuration and fueling condition, a general estimate of the flame BL in a rich-fuel environment was provided, in which a fuel flow rate (FFR) was 7.5 g/s. Once the FFR was exceeded, the flame was unstable and blown out, whereas the MCGA plasma demonstrated an excellent flame stabilization ability. The flame BL of the scramjet combustor in the presence of the MCGA plasma has an increase of ∼29%. Two PAC processes, including enhancement mode and re-ignition mode, were distinguished to play a vital role in extending the flame BL. The two PAC processes showed that the spark-type discharge generated by the MCGA could ignite the local fuel-rich mixture and increase the flame BL. The local ignition is dominated by the continuous accumulation of the massive flame kernels with the local fuel-rich mixture, as well as more heat and species exchanges. [ABSTRACT FROM AUTHOR]