| With the rapid development of economic society, airliner has gradually become today's popular choice in fast-paced lifestyle because of its speed and convenience.However, there are some issues about passengers' health and comfort and these are closely related to the airflow form created by a cabin loop control system. Therefore,how to design a reasonable airflow form in order to establish a safe,healthy and comfortable cabin thermal environment is very important.Under the mixed air supply method, which is the most common forms in cabin,airflow under the narrow space and dense passengers is the result of natural convection and forced convection interaction. This paper used B737-200 Seven-rows cabin mockup as the study object, analyzed the impact of natural convection and forced convection on the overall air flow and local thermal environment, and established a quantitative relationship between natural convection intensity and the cabin airflow characteristics in order to guide airflow design.Firstly, this paper reviewed the current research about the thermal environment,analysing the existing issues and the necessity to reveal the natural reasons behind the flow phenomenon. Secondly, a cabin thermal environment under cruise condition was established, measuring and studying the global and local flow field. PIV technology was used to measure and compare isothermal and non-isothermal flow field under standard air volume, qualitatively analysing the significantly impact of natural convection which was also proved by N-S momentum equations. Then, combine cabin factors affecting the flow field to derive quantitative evaluation index of natural convection and decided the multiple sets of experiments conditions. Additionally, use PIV, UA, and thermocouple to measure the overall air flow, air jet development, and thermal environment of personnel area under various operating conditions,and established quantitative relationship between the quantization index and the overall or the local environment characters in order to guide the actual design. Finally, in order to make more realistic conclusion, use the numerical model validated by experimental data to discuss the influence of low-pressure on the cabin flow field.The conclusions can be obtained that: 1. The addition of natural convection can improve the symmetry, uniformity of the flow field, and strengthen the role of the jet entrainment and weaken its attachment effect; the thermal buoyancy (natural convection) and the inertial force (forced convection) calculated by NS momentum equation was both considerable. 2. Quantitative relationship was established between a combination of Re and Ar and the air flow, air-jet characters, and personnel thermal environment under different non- isothermal conditions. First of all, at least in Re>3800 and Ar <6, it can form a complete large eddy field surrounding A/B/C passengers; secondly, Ar is inversely proportional with the speed of decay trend of non-isothermal jet center velocity; then, according to the level of jet momentum and total calories constant feature, combined with the effects of natural convection Ar can derive the jet center trajectory equation, which is in good agreement with the experimental data; Finally, global Ar enhancement improved the thermal comfort on the occupied zone,but also lead to the expansion of static area,which was not conducive to rid off thermal load and pollutants,as well as narrowing the best wind speed area of 0.1-0.2m/s; 3. The 0.8atm ambient pressure caused the improvement of the air physical parameters (thermal expansion coefficient "?"), the raise level of 6.7%of cabin heat buoyancy, which can be ignored. |
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