scholarly journals Automotive compressor: effect of an electric throttle in the upstream circuit on the surge limit

2018 ◽  
Vol 234 ◽  
pp. 03006 ◽  
Author(s):  
Pierre Podevin ◽  
Amélie Danlos ◽  
Michaël Deligant ◽  
Plamen Punov ◽  
Adrian Clenci ◽  
...  
Keyword(s):  
Transient Analysis ◽  
Gasoline Engine ◽  
Transient Operation ◽  
Flow Rates ◽  
Transient Conditions ◽  
Lower Flow ◽  
Throttle Valve ◽  
Compressor Surge ◽  
Surge Line ◽  
Set Up

On vehicles equipped with a turbocharged engine, there is a risk of compressor surge. This surge generates instabilities that lead to driving inconvenience, or even mechanical failure of the supercharging system. In general, the surge appears rather in transient operation: sudden closing of the throttle valve on gasoline engine, regulation of the EGR on diesel engine linked also to turbine regulation (VNT device or Waste Gate). On a turbocharger test stand, we set up the surge line in a “conventional way”: stationary experiments. Then we set up this line in transient conditions for different positions of an electric throttle placed upstream the compressor. It appears that: the surge limit is pushing back to lower flow rates when it is determined in transient; the surge limit is pushing back to lower flow rates when closing the throttle valve. The tests were carried on by the transient analysis of the surge during a quick closing-opening of the electric throttle valve.

Determination of trace concentrations of copper by FIA-FAAS after preconcentration on chelating sorbents

1989 ◽  
Vol 54 (7) ◽  
pp. 1785-1794 ◽  
Author(s):  
Vlastimil Kubáň ◽  
Josef Komárek ◽  
Zbyněk Zdráhal
Keyword(s):  
Sampling Frequency ◽  
Copper Determination ◽  
Flow Rates ◽  
Sample Injection ◽  
Injection Flow ◽  
Chelating Sorbents ◽  
Set Up ◽  
Trace Concentrations ◽  
Better Than

A FIA-FAAS apparatus containing a six-channel sorption equipment with five 3 x 26 mm microcolumns packed with Spheron Oxin 1 000, Ostsorb Oxin and Ostsorb DTTA was set up. Combined with sorption from 0.002M acetate buffer at pH 4.2 and desorption with 2M-HCl, copper can be determined at concentrations up to 100, 150 and 200 μg l-1, respectively. For sample and eluent flow rates of 5.0 and 4.0 ml min-1, respectively, and a sample injection time of 5 min, the limit of copper determination is LQ = 0.3 μg l-1, repeatability sr is better than 2% and recovery is R = 100 ± 2%. The enrichment factor is on the order of 102 and is a linear function of time (volume) of sample injection up to 5 min and of the sample injection flow rate up to 11 ml min-1 for Spheron Oxin 1 000 and Ostsorb DTTA. For times of sorption of 60 and 300 s, the sampling frequency is 70 and 35 samples/h, respectively. The parameters of the FIA-FAAS determination (acetylene-air flame) are comparable to or better than those achieved by ETA AAS. The method was applied to the determination of traces of copper in high-purity water.

Leakage Flow Investigations on a Through-Wall Crack Related to Thermal Fatigue of Nuclear Power Plant Piping

2017 ◽  
Author(s):  
Stefan Schmid ◽  
Rudi Kulenovic ◽  
Eckart Laurien
Keyword(s):  
Experimental Data ◽  
Nuclear Power ◽  
Numerical Models ◽  
Measurement Techniques ◽  
Experimental Investigations ◽  
Leakage Flow ◽  
Test Rig ◽  
Reduced Pressure ◽  
Flow Rates ◽  
Set Up

For the validation of empirical models to calculate leakage flow rates in through-wall cracks of piping, reliable experimental data are essential. In this context, the Leakage Flow (LF) test rig was built up at the IKE for measurements of leakage flow rates with reduced pressure (maximum 1 MPA) and temperature (maximum 170 °C) compared to real plant conditions. The design of the test rig enables experimental investigations of through-wall cracks with different geometries and orientations by means of circular blank sheets with integrated cracks which are installed in the tubular test section of the test rig. In the paper, the experimental LF set-up and used measurement techniques are explained in detail. Furthermore, first leakage flow measurement results for one through-wall crack geometry and different imposed fluid pressures at ambient temperature conditions are presented and discussed. As an additional aspect the experimental data are used for the determination of the flow resistance of the investigated leak channel. Finally, the experimental results are compared with numerical results of WinLeck calculations to prove specifically in WinLeck implemented numerical models.

Assessment of Radius of Investigation of Pressure Transient Analysis in Highly Heterogeneous Reservoirs

2021 ◽  
Author(s):  
Murat Zeybek ◽  
Lei Jiang ◽  
Hadrien Dumont
Keyword(s):  
Transient Analysis ◽  
Numerical Models ◽  
Heterogeneous Systems ◽  
Layered Systems ◽  
Pressure Transient ◽  
Heterogeneous Reservoirs ◽  
Geological Features ◽  
Heterogeneous Formations ◽  
Set Up ◽  
New Generation

Abstract The radius of investigation (ROI) of pressure transient analyses has been traditionally assessed using analytical formulations with basic reservoir parameters for homogenous systems. Numerous studies aimed to improve ROI formulations to incorporate all reservoir and testing parameters such as gauge resolution and rate for more accurate ROI assessments. However, new generation wireline formation testers aim to improve deep transient tests with significant developments in gauge resolution and increasing rate. Challenges still remain in heterogeneous formations such as shaly sands and carbonate reservoirs. In this study, detailed conceptual high-resolution numerical models are set up, including comprehensive reservoir and measurement parameters, to investigate more realistic ROI assessments in layered heterogeneous systems without and with hydraulic communication. Several conceptual examples are presented in layered systems with permeability contrasts. In addition, deviation from infinite-acting radial flow (IAFR) and pressure propagation in highly heterogeneous layered systems are investigated to detect the presence of geological features, including closed boundary systems and the presence of a fault in the proximity of wellbore.

scholarly journals Powder flow down a vertical pipe: the effect of air flow

2002 ◽  
Vol 459 ◽  
pp. 317-345 ◽  
Author(s):  
Y. BERTHO ◽  
F. GIORGIUTTI-DAUPHINÉ ◽  
T. RAAFAT ◽  
E. J. HINCH ◽  
H. J. HERRMANN ◽  
...  
Keyword(s):  
Small Diameter ◽  
Stationary Flow ◽  
Momentum Conservation ◽  
Wall Friction ◽  
Particle Fraction ◽  
Friction Forces ◽  
Flow Rates ◽  
Lower Flow ◽  
Grain Flow ◽  
Grain Distribution

The dynamics of dry granular flows down a vertical glass pipe of small diameter have been studied experimentally. Simultaneous measurements of pressure profiles, air and grain flow rates and volume fractions of particles have been realized together with spatio-temporal diagrams of the grain distribution down the tube. At large grain flow rates, one observes a stationary flow characterized by high particle velocities, low particle fractions and a downflow of air resulting in an underpressure in the upper part of the pipe. A simple model assuming a free fall of the particles slowed down by air friction and taking into account finite particle fraction effects through Richardson–Zaki's law has been developed: it reproduces pressure and particle fraction variations with distance and estimates friction forces with the wall. At lower flow rates, sequences of high-density plugs separated by low-density bubbles moving down at a constant velocity are observed. The pressure is larger than outside the tube and its gradient reflects closely the weight of the grains. Writing mass and momentum conservation equations for the air and for the grains allows one to estimate the wall friction, which is less than 10% of the weight for grains with a clean smooth surface but up to 30% for grains with a rougher surface. At lower flow rates, oscillating-wave regimes resulting in large pressure fluctuations are observed and their frequency is predicted.

Cutting Tool Temperatures in Contour Turning: Transient Analysis and Experimental Verification

1997 ◽  
Vol 119 (4A) ◽  
pp. 494-501 ◽  
Author(s):  
D. A. Stephenson ◽  
T.-C. Jen ◽  
A. S. Lavine
Keyword(s):  
Transient Analysis ◽  
Cutting Tool ◽  
Process Development ◽  
Thermal Contact ◽  
Model Development ◽  
Cutting Speed ◽  
Depth Of Cut ◽  
Transient Conditions ◽  
Trouble Shooting ◽  
Model Predictions

This paper describes a model for predicting cutting tool temperatures under transient conditions. It is applicable to processes such as contour turning, in which the cutting speed, feed rate, and depth of cut may vary continuously with time. The model is intended for use in process development and trouble shooting. Therefore, emphasis is given in the model development to enable rapid computation and to avoid the need to specify parameters such as thermal contact resistances and convection coefficients which are not known in practice. Experiments were conducted to validate the predictive model. The model predictions with two different boundary conditions bound the experimental results. An example is presented which shows the utility of the model for process planning.

scholarly journals Surge and Stall Detection Using Acoustic Analysis for Gas Turbine Hybrid Cycles

2019 ◽  
Author(s):  
Keishaly Cabrera Cruz ◽  
Paolo Pezzini ◽  
Lawrence Shadle ◽  
Kenneth M. Bryden
Keyword(s):  
Gas Turbine ◽  
Natural Frequencies ◽  
Acoustic Analysis ◽  
General Nature ◽  
Acoustic Sensors ◽  
Frequency Range ◽  
Surge Margin ◽  
Compressor Surge ◽  
Surge Line ◽  
Transient Operations

Abstract Compressor dynamics were studied in a gas turbine – fuel cell hybrid power system having a larger compressor volume than traditionally found in gas turbine systems. This larger compressor volume adversely affects the surge margin of the gas turbine. Industrial acoustic sensors were placed near the compressor to identify when the equipment was getting close to the surge line. Fast Fourier transform (FFT) mathematical analysis was used to obtain spectra representing the probability density across the frequency range (0–5000 Hz). Comparison between FFT spectra for nominal and transient operations revealed that higher amplitude spikes were observed during incipient stall at three different frequencies, 900, 1020, and 1800 Hz. These frequencies were compared to the natural frequencies of the equipment and the frequency for the rotating turbomachinery to identify more general nature of the acoustic signal typical of the onset of compressor surge. The primary goal of this acoustic analysis was to establish an online methodology to monitor compressor stability that can be anticipated and avoided.

Study on the effect of pore-scale heterogeneity and flow rate during repetitive two-phase fluid flow in microfluidic porous media

2021 ◽  
pp. petgeo2020-062
Author(s):  
Jingtao Zhang ◽  
Haipeng Zhang ◽  
Donghee Lee ◽  
Sangjin Ryu ◽  
Seunghee Kim
Keyword(s):  
Porous Media ◽  
Fluid Flow ◽  
Flow Rate ◽  
Sweep Efficiency ◽  
Residual Saturation ◽  
Flow Rates ◽  
Content Type ◽  
Lower Flow ◽  
Supplementary Material ◽  
Lower Flow Rate

Various energy recovery, storage, conversion, and environmental operations may involve repetitive fluid injection and, thus, cyclic drainage-imbibition processes. We conducted an experimental study for which polydimethylsiloxane (PDMS)-based micromodels were fabricated with three different levels of pore-space heterogeneity (coefficient of variation, where COV = 0, 0.25, and 0.5) to represent consolidated and/or partially consolidated sandstones. A total of ten injection-withdrawal cycles were applied to each micromodel at two different flow rates (0.01 and 0.1 mL/min). The experimental results were analyzed in terms of flow morphology, sweep efficiency, residual saturation, the connection of fluids, and the pressure gradient. The pattern of the invasion and displacement of nonwetting fluid converged more readily in the homogeneous model (COV = 0) as the repetitive drainage-imbibition process continued. The overall sweep efficiency converged between 0.4 and 0.6 at all tested flow rates, regardless of different flow rates and COV in this study. In contrast, the effective sweep efficiency was observed to increase with higher COV at the lower flow rate, while that trend became the opposite at the higher flow rate. Similarly, the residual saturation of the nonwetting fluid was largest at COV = 0 for the lower flow rate, but it was the opposite for the higher flow rate case. However, the Minkowski functionals for the boundary length and connectedness of the nonwetting fluid remained quite constant during repetitive fluid flow. Implications of the study results for porous media-compressed air energy storage (PM-CAES) are discussed as a complementary analysis at the end of this manuscript.Supplementary material: Figures S1 and S2 https://doi.org/10.6084/m9.figshare.c.5276814.Thematic collection: This article is part of the Energy Geoscience Series collection available at: https://www.lyellcollection.org/cc/energy-geoscience-series

Dynamic Model of Multistage Centrifugal Compressor With a Stage-by-Stage Anti-Surge Recirculating System

2021 ◽  
Author(s):  
Nicola Casari ◽  
Michele Pinelli ◽  
Alessio Suman ◽  
Matteo Manganelli ◽  
Mirko Morini ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Suction Side ◽  
System Level ◽  
Low Flow ◽  
Return Flow ◽  
Control Line ◽  
Compressor Surge ◽  
Surge Control ◽  
Surge Line

Abstract The operability region of a centrifugal compressor is bounded by the low-flow (or high-pressure ratio) limit, commonly referred to as surge. The exact location of the surge line on the map can vary depending on the operating condition and, as a result, a typical Surge Avoidance Line is established at 10% to 15% above the stated flow for the theoretical surge line. The current state of the art of centrifugal compressor surge control is to utilize a global recycle valve to return flow from the discharge side of a centrifugal compressor to the suction side to increase the flow through the compressor and, thus, avoid entering the surge region. This is conventionally handled by defining a compressor surge control line that conservatively assumes that all stages must be kept out of surge at all the time. In compressors with multiple stages, the amount of energy loss is disproportion-ally large since the energy that was added in each stage is lost during system level (or global) recycling. This work proposes an internal stage-wise recycling that provides a much more controlled flow recycling to affect only those stages that may be on the verge of surge. The amount of flow needed for such a scheme will be much smaller than highly conservative global recycling approach. Also, the flow does not leave the compressor casing and therefore does not cross the pressure boundary. Compared to global recycling this inherently has less loss depending upon application and specific of control design.

scholarly journals Post-Operative Flow-Volume Loops

1977 ◽  
Vol 5 (2) ◽  
pp. 146-148 ◽  
Author(s):  
A. Morton ◽  
P. Hansen ◽  
A. B. Baker
Keyword(s):  
Flow Volume ◽  
Lung Volumes ◽  
Flow Rates ◽  
Lower Flow

A study of flow-volume curves pre- and post-operatively demonstrated a marked difference between bronchitic and non-bronchitic patients. All bronchitic patients showed lower flow rates at low lung volumes post-operatively, when compared with their pre-operative values. Non-bronchitic patients all had higher flow rates for the same comparison.

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