面向绿色制造的高效冷却技术及其试验

绿色制造和高效加工是21世纪先进制造业的必然趋势,为实现绿色高效加工,本文提出了一种新型的绿色高效冷却技术——低温气动喷雾射流冲击冷却技术,通过低温气流运载少量冷却液以喷雾射流冲击的形式到达加工区实现强化换热,将加工区的换热水平提高到一个全新的水平.瞬态实验结果表明,在射流速度40 m/s、靶距10 mm的射流条件下,这种冷却方式可提供的临界热流密度高达60W/mm^2,相对于磨削发生烧伤的临界热流密度提高了6倍以上.     

逆升压电子设备冷却系统的微机控制

逆升压电子设备冷却系统具有两种冷却方式─—冲压空气冷却方式和空气循环冷却方式，必须要有一套控制机构来自动选择系统的冷却方式。文中分析了以往的机械传动控制方法和基于三点温度的微机控制方法，并指出这两种控制方法的缺点。最后提出一种新的基于飞行高度及马赫数的微机控制方法。     

穿透式冷板的传热分析

对航空电子设备上采用的空心冷板冷却系统的传热特性进行了分析求解，得到了空心冷板稳态温度分布表达工和功率－温度－流量关系式，可作为空心冷板系统的设计依据，建立了空心冷板失效的动态温度模型，得到的温度－时间响应特性可用于评估冷板系统耐热冲击性能。     

Thermal-structural analysis of regenerativelycooled thrust chamber wall in reusable LOX/Methane rocket engines

To predict the thermal and structural responses of the thrust chamber wall under cyclic work,a 3-D fluid-structural coupling computational methodology is developed.The thermal and mechanical loads are determined by a validated 3-D finite volume fluid-thermal coupling computational method.With the specified loads,the nonlinear thermal-structural finite element analysis is applied to obtaining the 3-D thermal and structural responses.The Chaboche nonlinear kinematic hardening model calibrated by experimental data is adopted to predict the cyclic plastic behavior of the inner wall.The methodology is further applied to the thrust chamber of LOX/Methane rocket engines.The results show that both the maximum temperature at hot run phase and the maximum circumferential residual strain of the inner wall appear at the convergent part of the chamber.Struc tural analysis for multiple work cycles reveals that the failure of the inner wall may be controlled by the low-cycle fatigue when the Chaboche model parameter γ3 =0,and the damage caused by the thermal-mechanical ratcheting of the inner wall cannot be ignored when γ3 ＞ 0.The results of sen sitivity analysis indicate that mechanical loads have a strong influence on the strains in the inner wall.     

Numerical simulations of water spray on flame deflector during the four-engine rocket launching

This paper aims to study on the cooling effect with two types of water spray nozzle on the flame deflector during the four-engine launch vehicle take-off. To accurately simulate the two-phase flow of the rocket gas with multispecies and the water spray, the three-dimensional compressible Navier-Stokes equations, discrete ordinates methods and realizable k-Ɛ turbulence model are used to establish the rocket supersonic plumes impact model. The Eulerian dispersed phase (EDP) model was used to simulate the water spray into the exhaust gas. The accuracy and effectiveness of the gas-liquid flow model are verified by a good agreement between simulation results and experimental data. On this basis, a series of numerical simulation studies under different water injection position are performed. The results show that the high temperature regions, along the axis of engines on the deflector plate, have no significant temperature decreasing effect by water spray from the nozzles mounted on the apex of the deflector, and the high temperature converts a large quantity of water into vapor near the plume boundary, which would decrease the flow conductivity. With the cooling spray nozzle fixed directly to the deflector plate, the temperature decrease effect is obvious and the effect of thermal shock on deflector plate induced by exhaust plume is reduced, so that it can prevent the flame deflector from thermal ablation. The study results provide indepth information and engineering guidance for designing the water spray systems and increasing the safety of the launch process.     

高主流湍流度下密度比对涡轮导叶全气膜冷却特性的影响

为了研究高主流湍流度下二次流密度比对涡轮导叶全气膜冷却特性的影响,使用热色液晶测量了在主流湍流度为15%,二次流密度比为1.0和1.5下三维涡轮导叶的气膜冷却效率和换热系数。二次流与主流质量流量比为7.0%和12.5%。结果表明:二次流密度比增大可以降低冷气射流的动量,小流量比工况下,在叶片前缘和压力面前半段,动量较低的二次流在高主流湍流度的影响下更易耗散,增大二次流密度比使冷却效率明显降低;大流量比工况下,二次流动量降低使气膜孔后区域冷气贴附性增强,气膜冷却效率和冷气覆盖效果均得到提升。小流量比工况下,二次流密度比增大对叶片表面换热的影响较小;大流量比工况下,二次流密度比增大使吸力面中弦区域和压力面后半段的平均换热系数比分别降低15%和25%。     

无沸腾区机载喷雾冷却实验关联式研究

主要开展4种不同结构热沉表面无沸腾区机载喷雾冷却实验关联式的研究.在总结前人工作经验并搭建实验台完成实验的基础上,提出了影响喷雾冷却性能的4个无量纲参数,且通过实验数据处理得到各个热沉表面的努塞尔数无量纲关联式.给出的光滑热沉表面实验关联式的预测值与实验值偏差在±8.5%以内,并分析了各个量纲对实验关联式精度的影响.对于钻孔表面,引入传热强化系数对关联式进行修正,使得关联式的预测值能够落在偏差±15%内.另外单独给出了槽道热沉表面的实验关联式,该关联式不受槽道结构及数量的影响,且适用于水、盐类及醇类溶液.      

塞锥气膜冷却对二元塞式喷管红外特征的影响

为了研究二元塞式喷管塞锥壁面多斜孔气膜冷却对喷管红外特征的影响,设计了带冷却结构的喷管试验模型,测量了吹风比从0增加到1时的塞锥壁面温度、喷管出口截面处喷流温度以及喷管红外辐射强度.结果表明：随着吹风比的增加,气膜冷却效率逐渐提高,最大达到0.68;喷管出口截面在中心区域喷流的温度逐渐降低,最大降幅为14%;喷管红外辐射强度逐渐降低,在0°方位角上最大降低52.8%,在90°方位角上最大降低13%.     

新型翅片式减涡器减阻特性数值研究

为了降低压气机径向引气过程中的压力损失,在设计出新型翅片单元结构的基础上,研究了新型翅片单元结构对径向引气压力损失的影响规律,对不同转速、新型翅片结构的去旋系统开展了数值研究,得到了不同工况下压气机共转盘腔径向引气的流场结构及压力损失分布曲线。研究结构表明:新型翅片单元结构能够抑制盘腔内气流旋流比,降低引气压力损失;翅片单元通道宽度和高度均存在最佳值使得减涡器减阻效果较好,在优选结构翅片单元通道宽度L=0.78,通道高度R3=0.97的条件下,其减阻效果较简单盘腔模型提高86.5%。高低翅片结构能起到较好的减阻效果,随着单侧翅片高度的升高减阻效果逐渐增强,在本文结构下增加单侧翅片高度L1=0.3时减阻效果最优,且A侧或B侧翅片增加带来的减阻效益相同。一方面,最优高低翅片结构其减阻性能相比于简单盘腔模型、典型翅片式减涡器模型以及翅片单元通道宽度L=0.78,通道高度R3=0.97的结构模型分别提高87.5%,29%,7.8%;另一方面,最优高低翅片结构能够减轻翅片单元的质量,具有较高的工程应用价值。     

高湍流度时全气膜涡轮叶片表面冷却和换热特性的实验研究

为获得高主流湍流度时全气膜涡轮叶片表面的冷却和换热特性,在跨声速风洞中实验研究了质量流量比(MFR)和主流雷诺数(Re)对叶片表面气膜冷却效率和换热系数比的影响。在叶片前缘布置了5排圆形孔,在吸力面和压力面分别布置了3排和6排圆形孔,实验结果由嵌入在叶片中截面的热电偶测得。实验中基于弦长的主流雷诺数的范围为3.0×105～9.0×105,叶栅出口马赫数Ma为0.8, MFR的范围是5.5%～12.5%,主流湍流度Tu为14.7%。实验结果表明:主流雷诺数升高显著增强了叶片表面的换热,使层流边界层到湍流边界层的转捩位置提前。对于吸力面S/C0.2的区域(S/C为当地弧长与弦长之比),气膜冷却效率受MFR影响明显,当MFR大于7.7%时提高MFR会导致气膜冷却效率降低;该区域的换热系数比在中低雷诺数时受MFR影响较小,在高雷诺数时随MFR升高而升高。压力面S/C-0.7区域的气膜冷却效率随MFR升高而升高,-0.7S/C-0.4区域的气膜冷却效率受MFR影响较小,对于整个压力面而言,MFR升高提高了叶片表面的换热系数。相对于叶片其它区域,压力面后半段区域和吸力面的气膜冷却效率受雷诺数影响较大。