Simulation of an aircraft thermal management system based on vapor cycle response surface model

The modern aircraft Thermal Management System(TMS)faces significant challenges due to increasing thermal loads and limited heat dissipation pathways.To optimize TMS during the conceptual design stage,the development of a modeling and simulation tool is crucial.In this study,a TMS simulation model library was created using MATLAB/SIMULINK.To simplify the complexity of the Vapor Cycle System(VCS)model,a Response Surface Model(RSM)was constructed using the Monte Carlo method and validated through simulation experiments.Taking the F-22 fighter TMS as an example,a thermal dynamic simulation model was constructed to analyze the variation of thermal response parameters in key subsystems and elucidate their coupling relationships.Furthermore,the impact of total fuel flow and ram air flow on the TMS was investigated.The findings demonstrate the existence of an optimal total fuel flow that achieves a balance between maximizing fuel heat sink utilization and minimizing bleed air demand.The adaptive distribution of fuel and ram air flow was found to enhance aircraft thermal management performance.This study contributes to improving modeling efficiency and enhancing the understanding of the thermal dynamic characteristics of TMS,thereby facilitating further optimization in aircraft TMS design.

Optimization on conventional and electric air-cycle refrigeration systems of aircraft: A short-cut method and analysis

The air-cycle refrigeration system is widely used in commercial and military aircraft,and its efficiency greatly affects aircraft performance.Nowadays,this system requires a more efficient design and optimization method.In this paper,a short-cut optimization method with high efficiency and effectiveness is introduced for both conventional and electric air-cycle refrigeration systems.Based on the system characteristics,a four-layer parameter matching algorithm is designed which avoids computational difficulty caused by simultaneous equations.Fuel penalty is chosen as the objective function of optimization;design variables are reduced based on sensitivity analysis to improve optimization efficiency.The results show that the 3-variable optimization of the conventional air-cycle refrigeration system can obtain almost the same results as the traditional 6-variable optimization in that these two optimizations can both significantly reduce the fuel penalty.However,the computer running time of the 3-variable optimization is much shorter than that of the 6-variable optimization.The optimal fuel penalty of the electric air-cycle refrigeration system is lower than that of the conventional one.This study can provide reference for optimizing the aircycle refrigeration system of aircraft.

Experimental investigation on boiling heat transfer characteristics of Al_2O_3-water nanofluids in swirl microchannels subjected to an acceleration force

Experiments were carried out to investigate the boiling heat transfer characteristics of Al_2O_3-water nanofluids in swirl microchannels under terrestrial gravity and acceleration fields. A centrifuge with a two-meter long rotational arm was used to simulate the acceleration magnitude up to 9 g and three various acceleration directions. Three test sections with different geometric parameters were applied. The volume concentration of Al_2O_3 nanoparticles with an average diameter of 13 nm was varied from 0.07% to 0.1%. The mass flow rate and vapor quality were in ranges of 3–6 kg/h and 0.4–1.0%, respectively. The effects of the mass flow rate, microchannel aspect ratio,vapor quality, nanoparticle volume concentration, and acceleration direction and magnitude were analyzed in a systematic manner. Experimental results showed that the acceleration direction and magnitude had significant influences on the boiling heat transfer. The heat transfer under configuration C was found to be superior to that under configurations A and B. Moreover, the heat transfer coefficient increased with increases of the mass flow rate and the volume concentration and decreased with the aspect ratio.

The Ancient Wellspring and the Source of the Future： The Creation of New Poetry and the New Man in Lu Xun＇s On the Power of Mara Poetry

Focusing on literary tradition and innovation, this paper examines Lu Xun＇s poetics as represented in his early treatise On the Power of Mara Poetry （Moluo shi li shuo）. As a leading writer and thinker deeply engaged in the dramatic social and cultural transformations taking place in early twentieth- century China, Lu Xun was very concerned about how to build up the New Man and new society via new literature. Advocating Maratic poets who are full of the spirit of revolt and nonconformity, Lu Xun endeavored to disturb and reinvigorate Chinese minds by bringing in foreign dynamics and energies based upon modem individualism and humanism. At the same time, Lu Xun insisted that, while moving toward a bright future, people should constantly consider China＇s prosperous past. For Lu Xun, tradition was still of great relevance in creating and nurturing new poetry, new men, and a new society. To simply lump Lu Xun together with pure anti-traditionalists is problematic. Lu Xun is commonly seen as an iconoclastic pioneer in modem China; however, I argue that Lu Xun demonstrated a dialectical reflection on the relationship between tradition and modernity. Actually, Lu Xun envisioned a process by which, galvanized by imported Maratic spirit, selected cultural legacies would undergo modem reconfiguration and revitalization.