A HYBRID CRYOGENIC COOLING SYSTEM FOR AN EXTENDED LIFE-TIME IR-SPACE TELESCOPE

Abstract Film-cooling jets behavior in a combustor chamber is deeply affected by swirling flow interactions and unsteadiness; on the other hand, the jets behavior has a direct impact on different phenomena such as cooling capabilities and ignition. For these reasons, an in-depth characterization of the film-cooling flows in the presence of a swirling main flow and demands dedicated time-resolved analyses. The experimental setup consists of a nonreactive single-sector linear combustor simulator installed in an open-loop wind tunnel. It is equipped with a swirler and a multiperforated plate to simulate the effusion cooling system of the liner. The rig is scaled with respect to the engine configuration to increase spatial resolution and to reduce the characteristic frequencies of the unsteady phenomena. Time-resolved particle image velocimetry (TRPIV) was exploited for the investigation testing different values of liner pressure drop. In addition, numerical investigations were carried out to gain a deeper insight of the behavior highlighted by the experiments and to assess the capability of computational fluid dynamics (CFD) in predicting the flow physics. In this work, the stress-blended eddy simulation (SBES) approach implemented in ansys fluent was adopted. Oscillations of the jets and intermittent interactions of the mainstream with the wall of the liner and hence with the film development have been investigated in detail. The results demonstrate how an unsteady analysis of the flow structures that characterize the jets, the turbulent mixing of coolant flows, and the interaction between mainstream and cooling jets is strictly necessary to have a complete knowledge of the behavior of the coolant, which in turn affects combustor operability and life time.

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Numerical Study of the Effects of Injection Fluctuations on Liquid Nitrogen Spray Cooling

Processes ◽

10.3390/pr7090564 ◽

2019 ◽

Vol 7 (9) ◽

pp. 564 ◽

Cited By ~ 1

Author(s):

Rong Xue ◽

Yixiao Ruan ◽

Xiufang Liu ◽

Liang Chen ◽

Liqiang Liu ◽

...

Keyword(s):

Liquid Nitrogen ◽

Cooling System ◽

Numerical Study ◽

Spray Cooling ◽

Volume Averaging ◽

Cryogenic Cooling ◽

Droplet Distribution ◽

Cooling Effects ◽

Spray Field ◽

Lower Temperature

Spray cooling with liquid nitrogen is increasingly utilized as an efficient approach to achieve cryogenic cooling. Effects of injection mass flow rate fluctuations on the evaporation, temperature distribution, and droplet distribution of a spray field were examined by employing a validated Computational Fluid Dynamics (CFD) numerical model. The numerical results indicated that injection fluctuations enhanced the volume-averaging turbulent kinetic energy and promoted the evaporation of the whole spray field. The strengthened mass and heat transfer between the liquid nitrogen droplets and the surrounding vapor created by the fluctuating injection led to a lower temperature of the whole volume. A relatively smaller droplet size and a more inhomogeneous droplet distribution were obtained under the unsteady inlet. The changes of the frequency and the amplitude of the fluctuations had little effects on the overall spray development. The results could enrich the knowledge of the relation between the inevitable fluctuations and the overall spray development and the cooling performance in a practical spray cooling system with cryogenic fluids.

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A study of central cryogenic cooling system for the comet rendezvous spacecraft

10.2514/6.1981-1099 ◽

1981 ◽

Keyword(s):

Cooling System ◽

Cryogenic Cooling

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Thermal Effects on the Structure and Characteristics of Plasma Sprayed Self-Fluxing Alloys

Thermal Spray 2000: Proceedings from the International Thermal Spray Conference ◽

10.31399/asm.cp.itsc2000p1377 ◽

2000 ◽

Author(s):

G. Bertrand ◽

C. Malavolta ◽

F. Tourenne ◽

B. Hansz ◽

C. Coddet ◽

...

Keyword(s):

Plasma Spray ◽

Mechanical Characteristics ◽

Cooling System ◽

Thermal Spraying ◽

Heating System ◽

Cryogenic Cooling ◽

Precise Control ◽

Heating And Cooling ◽

Mechanical Deformations ◽

Plasma Sprayed

Abstract In general, thermal spraying involves high temperatures that can be deleterious for the microstructure and deformation of the substrate. As a consequence, the use of a cooling system during spraying is often necessary. Meanwhile, in some cases, a too low surface temperature can induce a loss of properties, in particular concerning adherence and coating density. Therefore, it would be sometimes interesting to combine pre-heating and cooling stages with the plasma spray. A specific process, named HeatCool, was developed and patented to ensure a precise control of the temperature at the spraying location. The present work was focused on the study of the influence of pre-heating and cryogenic cooling conditions on the microstructure and mechanical characteristics of NiCrFeBSi self-fluxing alloy deposited by d.c. plasma spray technique. Firstly, a comparison between air and CO2 cooling was conducted to assess the efficiency corresponding to the specific use of cryogenic CO2. The main characteristics studied were the microhardness, roughness, porosity, mechanical deformations, morphology and crystallographic structures. Optimising the cooling methods and conditions combined with the process parameters improved microhardness of the plasma sprayed metal alloy and induced lower strain deformation of the substrate. Secondly, the pre-heating system was added to the device and the HeatCool process was evaluated. The process was demonstrated to be an efficient mean to enhance the structural and mechanical characteristics of coatings made of self-fluxing alloy.

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