Experimental study of a cavitating centrifugal pump during fast starts-up

The start-up of rocket engine turbopumps is generally performed only in a few seconds. It implies that these pumps reach their nominal operating conditions after only a few rotations. During these first rotations of the blades, the flow evolution in the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed evolution. These phenomena progressively become negligible when the steady behavior is reached. The pump transient behavior induces significant pressure fluctuations which may result in partial flow vaporization, i.e. cavitation. An existing experimental test rig has been updated in the LML laboratory (Lille, France) for the start-ups of a centrifugal pump. The study focuses on cavitation induced during the pump start-up. Instantaneous measurement of torque, flow rate, inlet and outlet unsteady pressures, and pump rotation velocity enable to characterize the pump behavior during rapid starting periods. Three different types of fast start-up behaviors have been identified. According to the final operating point, the start-up is characterized either by a single drop of the delivery static pressure, by several low-frequency drops, or by a water hammer phenomenon that can be observed both a the inlet and outlet of the pump. A physical analysis is proposed to explain these three different types of transient flow behavior

ETUDE DES ECOULEMENTS INSTATIONNAIRES DANS UNE POMPE EN REGIME DE DEMARRAGE OU EN REGIME ETABLI

PARIS-Arts et Métiers (751132303) / SudocSudocFranceF

Is hybrid cardiac rehabilitation superior to traditional cardiac rehabilitation?

International audienceBackground: The current COVID-19 pandemic imposes changes in the management of cardiac pathologies. Cardiac rehabilitation needs to define new protocols to welcome patients back. In connection with the observations of the European Association of Preventive Cardiology, the choice of cardiac tele-rehabilitation appeared to be unavoidable.Aim: This retrospective research based on data from the Program for the Medicalisation of Information Systems (PMSI) and the electronic medical record analyzes the effect of Hybrid Cardiac Rehabilitation.Methods: One hundred and ninety-two patients (29 females and 163 males) with an average of 56.9 years old (±10.3) were able to benefit from a Hybrid Cardiac Rehabilitation program. The data concerning the Stress Test and the Wall Squat Test were collected.Results: We have noticed that patients had improved their cardiorespiratory capacity on the initial and final Stress Test 6.6 (±1.8) MET to 8.2 (±1.9) MET (p < 0.0001). We also found that patients improved lower limb muscle strength 75.1 (±44.8) seconds to 105.7 (±49.7) seconds (p < 0.0001).Conclusions: Hybrid Cardiac Rehabilitation protocols can be set up in this pandemic situation. The programme effectiveness appears to be comparable to the traditional model. However, additional studies are needed to determine the effectiveness of this programme in the long term