A method to minimize the intake of exhaust air in a climate control system in livestock premises

This paper presents a method of aerodynamic separation of supply-exhaust airflows in a supply and exhaust climate control unit for livestock facilities in order to minimize back suction. The air removed from livestock buildings contains a large amount of moisture, carbon dioxide, ammonia, hydrogen sulfide and other harmful gases and in mine units, the outlet and inlet openings are located close enough, which is why exhaust air can be sucked together with the supply air. The paper presents a set of measures to minimize back suction. In particular, the distance between the supply and exhaust openings is substantiated. Moreover, it was proposed to give an additional velocity to the exhaust air due to the energy of natural traction. In order to solve this problem, a nozzle with a convergence angle of 45 ° was installed at the outlet of the unit. The effectiveness of the proposed solution was tested experimentally and it was found that when the inlet and outlet openings were located at a distance of more than 0.5 m, as well as when the exhaust jet was given a velocity of 3 m / s, the amount of back suction did not exceed 5%.

Automated detection of hot-gas path defects by Support Vector Machine based analysis of exhaust density fields

Defects in the hot-gas path of aero engines have been shown to leave typical signatures in the density distribution of the exhaust jet. These signatures are superposed when several defects are present. For improved maintenance and monitoring applications, it is important to not only detect that there are defects present but to also identify the individual classes of defects. This diagnostic approach benefits both, the analysis of prototype or acceptance test and the preparation of Maintenance, Repair, and Overhaul. Recent advances in the analysis of tomographic Background-Oriented Schlieren (BOS) data have enabled the technique to be automated such that typical defects in the hot-gas path of gas turbines can be detected and distinguished automatically. This automation is achieved by using Support Vector Machine (SVM) algorithms. Choosing suitable identification parameters is critical and can enable SVM algorithms to distinguish between different defect types. The results show that the SVM can be trained such that almost no defects are missed and that false attributions of defect classes can be minimized.

On subsonic near-wake flows of a space launcher configuration with various base geometries

Buffet/buffeting as load imposing mechanism on the base structures of space launcher has been of strong interest ever since it was found as partially responsible for the failed flight 157 of Ariane 5. Several studies suggested that the base region is most excited at Mach 0.8. A preceding study of the current series on base flow effects revealed a differing excitation in comparison to the other subsonic Mach number cases. It featured an especially pronounced excitation in the recirculation region. Thus, the current work attempts to answer the question why this case appears to be distinct. This is done by decreasing the relative nozzle length and focusing on the Reynolds stress distribution. The research question is approached by experiments in the ‘Vertical Test Section Cologne’ (VMK) on a base model with supersonic, over-expanded exhaust jet exposed to an ambient flow at Mach 0.8 and a Reynolds number of $$1.4\cdot 10^6$$ 1.4 · 10 6 . Data are acquired by means of particle image velocimetry (PIV) and high-speed schlieren imaging. The results reveal that a most unfavorable configuration appears to exist, which is if the mean shear layer reattachment takes place just on the tip of the nozzle. Graphic abstract

Passive autocatalitic recombiner characteritics calculation during severe accident on AES-2006 NPP

A modern NPP is equipped by containment to hold radioactive substances and ionizing radiation bounded as design margins prescribe. Hydrogen mitigation system is used to protect containment against hydrogen fire and detonation. The system includes a scope of passive autocatalitic recombiners. Hydrogen is transformed into water, passing through said recombiners. The reaction occurs on catalyst surface. The main catalyst material is a palladium doped platinum. Hydrogen mitigation system parameters during severe accident are of interest. Wise admitted for NPP full scale tests are impossible, so the main analysis are calculations. Recombiner consists of catalytic block and stuck. The stuck provides reagents feeding and products evacuation enhancing natural convection transport. A model for calculations is suggested for recombiner with a plate-type catalyst block. The two free parameters of the model are chemical reaction intensity on catalyst and unit drag. Said parameters are estimated experimental data based on. Passive autocatalitic recombiner characteritics during severe ac- cident on AES-2006 NPP are calculated. The unit capacity is found not less that specification points. Catalyst temperatures, even the mean one, are above 500 °С, exhaust jet temperature exceeds 150 °С. Hydrogen content is high in the jet. Capacity increases linearly with hydrogen concentration at the unit entrance. Atmospheric temperature influence is low. Hydrogen mitigation system overall capacity is constant for uniform or not uniform hydrogen distribution in the containment. The calculated data may be used for recombiner work estimation during accident on AES-2006 NPP.

Rocket Wake Flow Interaction Testing in the Hot Plume Testing Facility (HPTF) Cologne

Rocket wake flows were under investigation within the Collaborative Research Centre SFB/TRR40 since the year 2009. The current paper summarizes the work conducted during its third and final funding period from 2017 to 2020. During that phase, focus was laid on establishing a new test environment at the German Aerospace Center (DLR) Cologne in order to improve the similarity of experimental rocket wake flow–jet interaction testing by utilizing hydrogen–oxygen combustion implemented into the wind tunnel model. The new facility was characterized during tests with the rocket combustor model HOC1 in static environment. The tests were conducted under relevant operating conditions to demonstrate the design’s suitability. During the first wind tunnel tests, interaction of subsonic ambient flow at Mach 0.8 with a hot exhaust jet of approx. 920 K was compared to previously investigated cold plume interaction tests using pressurized air at ambient temperature. The comparison revealed significant differences in the dynamic response of the wake flow field on the different types of exhaust plume simulation.

On the subsonic near-wake of a space launcher configuration with exhaust jet

The Ariane 5 failure flight 157 made clear that the loads in the base region of space launcher configurations were underestimated and its near-wake dynamics required more attention. In the recent years, many studies have been published on buffet/buffeting in the critical high subsonic flow regime. Nevertheless, not much experimental data are available on the interaction of the ambient flow with an exhaust jet over a wide subsonic Mach number range. Further, a preceding study without exhaust jet revealed questions regarding a similar distribution of the velocity and Reynolds stress in the near-wake if scaled with the reattachment length. Consequently, a generic space launcher configuration featuring a cold, supersonic, over-expanded jet is investigated experimentally in the vertical test section Cologne (VMK) by means of particle image velocimetry (PIV) for five subsonic Mach numbers ranging from 0.5 to 0.9 with corresponding Reynolds numbers between $$Re_{\text {D}}=0.8\times 10^6$$ReD=0.8×106 to $$1.6\times 10^6$$1.6×106. The velocity and Reynolds stress distribution are provided for the near-wake flow and additionally for the incoming boundary layer. Just as in the preceding study, self-similar features are found in the flow field as long as the separated shear layer reattaches on the solid nozzle wall. Substantial changes are then measured for an alternating (hybrid) reattachment between the solid nozzle wall and supersonic exhaust jet as found for Mach 0.8, one of them being the increased axial turbulence in the recirculation bubble due to a ‘dancing’ large-scale, clockwise-rotating vortex. Graphic abstract