Ricardo Noguera

Experimental Analysis of an Axial Inducer Influence of the Shape of the Blade Leading Edge on the Performances in Cavitating Regime

We analyze, from experimental results, the influence of the shape of the leading edge and its sharpening on the cavitating behavior of an inducer. The studied inducer is designed according to a methodology developed at LEMFI. Successive cutting and sharpening (four cuts, which modify up to 20 percent of the blade chord at the tip), were made to modify the shape of the leading edge. For the various geometries, the experimental results obtained on the LEMFI test rig are presented as follows. Noncavitating Regime.- Overall performances at 1450 rpm. Cavitating Regime.- (1) The development of the cavitation versus the cavitation number, (2) the description of the various cavitation pictures, and (3) the pressure fluctuations measured at the wall at 150 mm downstream of the trailing edge for various flow: rates and inlet pressures. The CFD simulations carried out under CFX-Blade Gen + on this range of inducers are presented to explain certain aspects observed

Numerical Turbulent Simulation of the Two-Phase Flow (Liquid/Gas) Through a Cascade of an Axial Pump

The main goal of the present work is to establish the analysis of a numerical turbulent simulation of an axial pump cascade under two-phase flow presence of liquid and gas, coupled with the κ-e turbulent model. This knowledge is very important for different applications, for example in the oil industry. indeed, the transport of two-phase flow (oil and gas) that comes from the well implies the utilization of separation and treatment facilities before pumping. It means that a number of economical resources are involved in this kind of industrial operation. Therefore, depending on the function optimization of this type of two-phase pump, it would permit the substitution of the traditional expensive facilities, in addition to energy cost savings. In order to predict the fluid dynamics characteristics of an axial pump cascade under two-phase flow conditions with a view to improving its performance, the present research will describe a multifluid model in order to solve the momentum equations (Navier-Stokes) coupled with the continuity equation. Here, we will use a modified κ-e turbulent model, taking into account the viscosity of the liquid phase and the compressibility of the gas phase, using the CFD simulator: CFX-4.0

3D Quasi-Unsteady Flow Simulation in a Centrifugal Pump: Comparison With the Experimental Results

A 3D-CFD simulation of the impeller and volute casing of a centrifugal pump has been performed using commercial codes CFX 5.5 and CFX-TASCflow 2.12. The pump has an specific speed of 32 (metric units) and an outside impeller diameter of 400 mm. First, a 3D-flow simulation for the isolated impeller with a structured grid is presented. A sensitivity analysis regarding grid quality and turbulence models were also performed. A 3D quasi-unsteady flow simulation of the impeller-volute assembly is presented, as well. This flow simulation was carried out for several impeller blades and volute tongue relative positions. As a result, the radial thrust on the pump shaft were calculated for different flow rates. Experimental test were carried out in order to compare theoretical pressure fluctuations with the experimental ones measured by various unsteady pressure sensors placed on the impeller shroud and volute. The qualitative and quantitative results ratify numerical predictions.Copyright

Modeling and Analysis of a Turbojet Fuel System

In aeronautics, two of the main key design drivers are the reduction of the fuel consumption and the reduction of its environmental impact. These two considerations are taken into account by both aircraft and engine manufacturers. On the engine regulation system level, the first objective is reached by reducing its mass. The second one can be achieved with a more advanced fuel system. This paper deals with the control of a new fuel system of a turbojet. In comparison with classical fuel systems, a hydraulic equipment of the original system has been removed to reduce the mass, which means that standard control of the turbojet is no more effective. After modeling the new system, its couplings are studied and a controller is designed. This paper is organized as follows: Section II introduces the system and its functioning; the dynamic model is described in Section III and Section IV presents the design of the control system and its performances. Section V compares different methods of simulation, in order to find the most effective one for the system. At last, conclusions are presented in Section VI.

Numerical Study on Pressure Fluctuations Reduction in Centrifugal Pumps: Influence of Radial Gap and Splitter Blades

Numerical study was carried out in four centrifugal pumps to analyze the effects of adding splitters and incrementing the radial gap in order to decrease the pressure fluctuations at the blade passage frequency. It is well known that in this kind of pump, the interactions between the flow leaving the impeller and entering the volute generate fluctuating pressures which propagate toward the inlet and the discharge of the pump. These pulsations are mainly associated to the blade passage frequency presenting high amplitudes near the volute tongue and at impeller discharge. Four configurations were analyzed using numerical simulations; the first is the reference pump which will be optimized and the others are the optimized ones. The numerical modelling was performed at the same flow rate having to vary in some cases the rotational speed to reach the operating point. During the calculations, the pressure signals were recorded by virtual sensors placed at several locations of the pump then they were analyzed and processed by means of the Fast Fourier Transform. The pressure fluctuations were plotted and compared between the four configurations, showing clearly the fact of varying the blades number and the radial gap influence significantly on their reduction.

Numerical Performance Prediction and Experimental Validation of an Axial Pump Under Two-Phase Flow (Liquid/Gas)

The main goal of the present work is to establish the tools of the analysis and performance prediction of an axial pump stage under two-phase flow presence of liquid and gas. This knowledge is very important for different applications, for example in the oil industry. The transport of two-phase flow (oil and gas) that comes from the well implies the utilization of separation and treatment facilities before they are pumping. It means that a lot of economical resources are involved in this kind of industrial operation. Therefore, depending on the function optimization of this type of two-phase pumps, it would permit the substitution of the traditional expensive facilities in addition with energy cost savings. In order to predict the fluid dynamics characteristics of an axial pump stage under two-phase flow conditions and in view to improve its performance, the present research will describe a multi-fluid model in order to solve the momentum equations (Navier-Stokes) coupled with the continuity equation. Here, we will take into account the viscosity of the liquid phase and the compressibility of the gas phase, using the CFD simulator: CFX 4.0. Finally, an experimental facility was designed and built to test one axial pump of two stages. Therefore, experimental data is shown in order to validate the previous numerical results obtained.Copyright

Decentralized Control: Application to a Turboprop Engine

This paper proposes a straightforward and systematic way of designing a decentralized control. The main setup steps are the interaction analysis, the decoupling of the interactions, and the design of the controllers. The proposed procedure is applied on identified models of a turboprop engine. The interaction analysis leads to the choice of a decentralized strategy with a full compensator. On each operating point, an inverted decoupler is selected in order to reduce interactions, and PI controllers are designed using an analytical method. The control laws robustness is then ensured using the structured singular value approach. Finally, control laws performances are validated using the non-linear simulation model of turboprop engine.

Numerical Investigation of Viscous Flow in Three Centrifugal Pumps

Centrifugal pump performance is affected when pumping viscous liquids, requiring a larger power input than the same pump handling water. In applications of chemical, civil, environmental, and mechanical engineering that involve centrifugal pumps, it is a challenge to accurately estimate and even more of a challenge to improve their performance when handling viscous liquids. When accurate performance data is needed, difficult experiments must be conducted with the operating viscous flow. The extension of the applicability of numerical techniques for solving fluid dynamics (CFD) permits the consideration of these tools as a definite possibility for predicting the performance of centrifugal pumps with viscous flows. The purpose of this study is to perform a 3D-CFD steady-state simulation of three different configurations of centrifugal pumps. The first is an impeller-diffuser pump (ns = 19) taken from an ESP model. The second is a Francis Pump-Turbine (ns = 28). Finally, the third configuration possesses an impeller and volute (ns = 32). The objective is to characterize and evaluate their performances with four different fluids from 1 to 420 cSt. These are: water at 25°C, SAE10 and SAE30 oils, and Fuel Oil Medium (FOM). For water flow conditions, the numerical results were compared with experimental data, and found to be consistent with global performance parameters. With regard to the higher viscosity fluids, the CFD calculation was compared with those obtained through the standard empirical method (ANSI/HI9.6.7). This resulted in good agreement between the performance results. The commercial software ANSYS-CFX was used for the CFD calculations.The resulting pump performance curve (head, hydraulic efficiency and power output) is consistent with that expected by theory. In general, as the viscosity of fluids increases, the hydraulic energy losses increase. Of the three pumps, slip factor for SAE30 oil was larger for all volumetric flows since it features the best guidance of the flow in the impeller blade passage. For the ns32 pump and the pump-turbine ns28, the volute losses rose from water to FOM, just like the impeller hydraulic losses. For these two turbo machines, the impeller losses were larger than volute losses. For the pumps with volute, the effects of fluid viscosity on the radial forces were evaluated. It was found that the radial forces decrease when the viscosity increases. This paper attempts to contribute to a better understanding of fluid dynamics within centrifugal pump impellers handling viscous fluids, and intends to shed more light on the approaches that performance prediction models should follow in the future.Copyright