共查询到18条相似文献,搜索用时 109 毫秒
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燃烧室部件传热空间非均匀性对缸内燃烧的影响 总被引:1,自引:0,他引:1
将所有燃烧室部件(气缸盖-气缸套-活塞组-润滑油膜)作为一个耦合体,在对耦合体进行三维传热数值模拟的基础上,利用分区求解、边界耦合法建立缸内工作过程与燃烧室部件的三维耦合计算模型,从而实现缸内工作过程与燃烧室部件的耦合三维仿真模拟,以此考察燃烧室部件传热空间非均匀性对缸内燃烧的影响。研究结果表明,燃烧室部件传热空间非均匀性在喷雾过程几乎对燃烧没有任何影响,可以忽略不计;燃烧过程后期,这种传热空间非均匀性才越来越明显,由此可以推断,燃烧室部件传热空间非均匀性的影响在排气过程将进一步加剧。 相似文献
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积分球和漫反射板是定标常用的扩展光源,其非均匀性在不同条件下会对定标产生不同的影响。该文根据辐射传输理论和定标原理,建立数学模型,以均匀性比较差的灯-板定标系统为例,计算CCD不同像元上的辐照度和定标系数,并以理想情况和非理想情况下定标系数矩阵的相关性作为评价函数,分析非均匀性对定标的影响。结果表明,由于扩展光源的非均匀性,观测角度和光轴与漫反射板交点的位置对定标系数的影响比较大,而观测距离的影响比较小;在不同观测角度下,可以找到一个偏离值使得定标结果最接近理想结果。因此用灯-板定标系统标定成像光谱仪时根据观测角度选择合适的偏离值,可以减小定标误差。 相似文献
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直喷发动机燃油喷雾撞击壁面形成油膜,导致燃烧效率降低,颗粒物排放增加.伴随撞壁的动态传热过程对油膜蒸发具有重要影响.本文针对正戊烷、甲醇、甲醇-汽油混合燃料瞬态喷雾撞击壁面,研究了不同条件下蒸发性对燃油瞬态喷雾撞击壁面动态传热影响.结果表明,提高喷油温度可促进燃油雾化,增大喷油压力或降低喷油距离可提高液滴撞壁强度,缩短... 相似文献
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空间外差光谱仪在研制加工过程中,由于加工误差及胶合误差会使CCD接收到的干涉图存在光强分布不均匀现象,降低了变换光谱的准确性。基于对空间外差光谱仪干涉图光强非均匀性的产生机制与特点分析基础上,提出了一种干涉图非均匀性校正方法,该方法通过对实际干涉图进行单调分解、分段归一化及重新组合过程求解出光强分布函数,然后将变换光谱与光强分布函数倒数的傅里叶变换结果进行卷积来获得非均匀性校正后的光谱,最后将校正光谱进行逆傅里叶变换从而实现干涉图的非均匀性校正。将此方法应用于空间外差试验仪的近红外实测单色光干涉图的非均匀性校正,结果显示,该方法可以有效改善干涉图光强分布的非均匀性,抑制变换光谱的边频信号,通过与仿真的理想光谱对比,1 571和1 572 nm光谱校正前后噪声的减小率分别达到40.7%和24%,提高了光谱信噪比和准确性。 相似文献
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燃烧室出口辐射对气膜冷却传热影响研究 总被引:2,自引:0,他引:2
燃气轮机高温透平中包含对流/导热/辐射等复杂传热现象。本文依托高温流热固耦合实验台,提出燃烧室与透平联合计算的方法,采用数值模拟和实验对比的方式分析了平板气膜冷却的对流/导热/辐射传热特性。同时研究了不同燃气吸收系数以及不同进口辐射条件对于平板气膜冷却的表面温度分布的影响。结果表明:辐射传热是燃气轮机首级高温叶片传热特性的重要影响因素,辐射传热使得实验平板温度抬升50~70 K,燃烧室/透平联合计算方法有效地分析了燃烧室出口辐射强度对高温平板气膜冷却辐射传热的影响;高温燃气辐射特性对于平板温度分布具有明显影响。 相似文献
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Luc Potier Florent Duchaine Bndicte Cuenot Didier Saucereau Julien Pichillou 《Entropy (Basel, Switzerland)》2022,24(2)
Although a lot of research and development has been done to understand and master the major physics involved in cryogenic rocket engines (combustion, feeding systems, heat transfer, stability, efficiency, etc.), the injection system and wall heat transfer remain critical issues due to complex physics, leading to atomization in the subcritical regime and the interactions of hot gases with walls. In such regimes, the fuel is usually injected through a coaxial annulus and triggers the atomization of the central liquid oxidizer jet. This type of injector is often referred to as air-assisted, or coaxial shear, injector, and has been extensively studied experimentally. Including such injection in numerical simulations requires specific models as simulating the atomization process is still out of reach in practical industrial systems. The effect of the injection model on the flame stabilization process and thus on wall heat fluxes is of critical importance when it comes to the design of wall-cooling systems. Indeed, maximizing the heat flux extracted from the chamber can lead to serious gain for the cooling and feeding systems for expander-type feeding cycles where the thermal energy absorbed by the coolant is converted into kinetic energy to drive the turbo-pumps of the feeding system. The methodology proposed in this work to numerically predict the flame topology and associated heat fluxes is based on state-of-the-art methods for turbulent reactive flow field predictions for rocket engines, including liquid injection, combustion model, and wall treatment. For this purpose, high-fidelity Large Eddy Simulation Conjugate Heat Transfer, along with a reduced kinetic mechanism for the prediction of chemistry, liquid injection model LOx sprays, and the use of a specific wall modeling to correctly predict heat flux for large temperature ratio between the bulk flow and the chamber walls, is used. A smooth and a longitudinally ribbed combustor configuration from JAXA are simulated. The coupling strategy ensures a rapid convergence for a limited additional cost compared to a fluid-only simulation, and the wall heat fluxes display a healthy trend compared to the experimental measurements. An increase of heat transfer coherent with the literature is observed when walls are equipped with ribs, compared to smooth walls. The heat transfer enhancement of the ribbed configuration with respect to the smooth walls is coherent with results from the literature, with an increase of around of wall heat flux extracted for the same chamber diameter. 相似文献
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Cooling technology is facing new challenges with the increase of electronic equipment power onboard aircraft. The traditional heat sink based on high-altitude bleed air does not satisfy this increase of cooling demands. In this article, an air/air-type skin heat exchanger is studied for cooling aircraft electronic equipment. It uses outside high-altitude cold air rather than bleed air as a heat sink. This cooling technology can effectively remove the heat load of high-power electronic devices without greatly increasing aircraft performance penalty. To assess its high-altitude heat transfer performance, an experimental prototype was designed and made. Some experiments were conducted on a ground experimental test. The heat transfer criteria formulas were obtained for both the side air in the skin heat exchanger and its convective heat transfer coefficients. Based on these experimental analyses, the heat transfer performances of the skin heat exchanger in a high-altitude cruise condition are deduced when it is assumed to be installed at an unfavorable position and a favorable position, separately. This work tries to provide a technical support for its future onboard application. 相似文献