The Theory And Applied Research On Platelet Transpiration Cooling

In the forty years after the concept of platelet transpiration cooling has been introduced, hundreds of platelet devices were invented and adapted. Platelet devices are fabricated by stacking several metallic or non-metallic thin sheets, which are etched with flow passages, into predetermined configuration along with the means of diffusion welding or other molding techniques. The platelet technology has the advantages of high capability of thermal controlling, accurate distributaries, flexible design and fabrication, and convenient for automation in production. And today, it presents extreme vitality because of the development of laser etching, in particular, etching to the corrosion-proofed metal platelet, and technique of diffusion welding. Along with the progress of the thermal protection research of liquid rocket engine chamber, with the adoption of typical platelet diffusion transpiration cooling device, the researches of platelet technology used for fluid flow controlling and fuel transpiration injection are improved further. Take a platelet-style fluid mixer as an example, various fluids flow in from adjacent minute slots of platelet structural wall in turn to realize cross-bedded transpiration injection, metering passages are used to control the flux of those fluids to ensure the process of cross-bedded inflow fluids, then even mixture mixes in small chamber which desired temperature and pressure are is achievable. In the recent two decades, the studies of platelet technology are advanced, however, they are focusing on one fluid mediator only to research the platelet transpiration cooling. Therefore, the researches of platelet cross-bedded transpiration mixing and transpiration injection about different fluids are hardly to be taken and they are waiting to be developed in desperation. Hence, this dissertation takes profound research of the theory of the platelet transpiration cooling, discusses elementarily on the configuration of gaps or slots in the cross-bedded platelet transpiration injection and makes applied research on the minute slots cross-bedded transpiration injection devices.Furthermore, the treatise includes some main researches as follows.1. Summary of the technique and relevant theories of typical platelet transpiration cooling, progress of domestic and foreign research of platelet devices and the experiences of fabricating platelets. It reviews domestic and foreign researches on platelet transpiration cooling technique, introduces late-model platelet devices in our motherland and overseas, such as typical platelet transpiration cooling devices, platelet style mixture and high speed propulsions, and also briefly describes craftwork of platelet devices.2. Study on the thermal transferring feature and fluid flow in passages on inner wall of typical platelet transpiration cooling devices. On the basis of macro-scale theory and the establishment of high temperature thermal transferring model in a typical transpiration cooling device with distributed passages, there are some researches have been done, such as figuring out resolutions to obtain and analyze the temperature of structural platelet and injecting fluid from distributed passages; finding out the relationship among coefficient of thermal conductivity, perimeter of coolant, flux of thermal flow of inner walls, geometric perimeter of distributed passages, structural platelet temperature and depth of hot dip; showing up some designing methods of platelet metering passages and discussing flow resistance character of passages just as metering passages and main passages.3. Analyzing thermal transferring character of distributed passages according to micro-scale theory. Along with the N-S equation and energy equation, micro-scale calculating model for flow and thermal transferring is set up with adoption of shifting edge condition relevant to the speed gradient of close-to-wall fluid and temperature varying edge condition relevant to the temperature gradient of close-to-wall fluid. Under all these, temperature distributing momentum in structural platelets and minute passages are measurable. On the other hand, the same issues are also taking under macro-scale theory, and comparing the outcomes with the ones from prior analysis.4. Taking analysis on the evaporation and combustion rate of hemispherical droplet of cross-bedded platelet transpiration. By utilizing the bispherical coordinates, the evaporation and combustion questions of hemispherical mediators in the outlet of a hole structure platelet transpiration are solved; the relationships among the evaporation and combustion rate of a hemispherical transpiration in a intensive hole structure platelet and the distance of adjacent holes, size of holes, environmental temperature and transpiration mediators are discussed, analytic solution of molecular diffusion of arbitrary hemispherical droplet are obtained, and the evaporation ratio, combustion rate and change momentum of hemispherical droplet transpiration are accounted under various conditions.5. Doing the study of the character of transpiration mediator flow and combustion in cross-bedded platelet transpiration slot structure, and providing theoretic base and design sample for conducting design of relevant mixture and combustion devices. For discussing the mixing and combustion of cross-bedded minute slot platelet transpiration injection, different fluids are chosen, as transpiration fluids, going through the cross-bedded minute slot platelet transpiration injection device to complete thorough mixing and combustion. With the help of setting up a typical cross-bedded minute slot platelet transpiration model, analysis of fluid mixture and combustion are obtainable, as well as the distribution of transpiration fluid constituents, distribution of temperature and fluid flux of inner wall in such a device.6. Thermodynamic coupling researches are carrying on towards sheets in distribution passages of platelet transpiration cooling. As for the thermal wrinkling issues of platelets, the relationships between each of three figures, which are temperature of platelets, thickness of sheets, and width of minute slots, are comparing with the deflexed critical compressive stresses. Analytic solution of unevenly thermal wrinkling issues of platelets in distributed flowing region is gained by using Galerkin method and bulking trial function, which satisfies the need of geometric boundary condition and static boundary condition rigorously. Analysis of the distortion and the stability under minor disturbing forces of be-heated platelets in various thicknesses; the height of different distributing passages; and be-heated platelet distortion under the condition of many diverse widths of rip strips are obtained by the use of finite-element method. The static analyzing method of platelet thermal wrinkling is testified through platelet thermal wrinkling experimental verification system, which is composed of heating-up membranes and clamp apparatus with V-shape vessels.7. Progressing discussion on application of analytic methods of platelet transpiration cooling. With the consideration of the special composition of many identical and similar structures of the construction of the platelet transpiration cooling device, automatic designing researches with perimeter variation methods are taking on platelet transpiration cooling units. Basing on the theory of platelet transpiration cooling, the analysis of cross-bedded platelet hemispherical droplets transpiration and of fluid mixture flow and combustion of cross-bedded platelet transpiration with minute slot structure are used in the studies of fluid mixing mechanism and cross-bedded transpiration injection combustion. And then, design considerations and theory foundations are obtained for the research on the cross-bedded minute slot platelet mixing and combustion devices.