Experimental Studies on the Pressure Rise in GIS by Internal Arcs with Various Material Parameters and Test Arrangements

1991 ◽  
pp. 459-465 ◽  
Author(s):  
D. König ◽  
H. Schuhmann
Keyword(s):  
Experimental Studies ◽  
Pressure Rise ◽  
Material Parameters

Computational Models for Sandwich Panels and Shells

1996 ◽  
Vol 49 (3) ◽  
pp. 155-199 ◽  
Author(s):  
Ahmed K. Noor ◽  
W. Scott Burton ◽  
Charles W. Bert
Keyword(s):  
Computational Models ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Local Buckling ◽  
Sandwich Panels ◽  
Free Vibrations ◽  
Sandwich Plates ◽  
Material Parameters ◽  
Sandwich Plates And Shells ◽  
Plates And Shells

The focus of this review is on the hierarchy of computational models for sandwich plates and shells, predictor-corrector procedures, and the sensitivity of the sandwich response to variations in the different geometric and material parameters. The literature reviewed is devoted to the following application areas: heat transfer problems; thermal and mechanical stresses (including boundary layer and edge stresses); free vibrations and damping; transient dynamic response; bifurcation buckling, local buckling, face-sheet wrinkling and core crimping; large deflection and postbuckling problems; effects of discontinuities (eg, cutouts and stiffeners), and geometric changes (eg, tapered thickness); damage and failure of sandwich structures; experimental studies; optimization and design studies. Over 800 relevant references are cited in this review, and another 559 references are included in a supplemental bibliography for completeness. Extensive numerical results are presented for thermally stressed sandwich panels with composite face sheets showing the effects of variation in their geometric and material parameters on the accuracy of the free vibration response, and the sensitivity coefficients predicted by eight different modeling approaches (based on two-dimensional theories). The standard of comparison is taken to be the analytic three-dimensional thermoelasticity solutions. Some future directions for research on the modeling of sandwich plates and shells are outlined.

scholarly journals Concrete propensity to fire spalling: testing and observations

2018 ◽  
Vol 163 ◽  
pp. 02004 ◽  
Author(s):  
Izabela Hager ◽  
Katarzyna Mróz ◽  
Tomasz Tracz
Keyword(s):  
Cement Paste ◽  
Experimental Studies ◽  
Experimental Techniques ◽  
Concrete Slabs ◽  
Cement Type ◽  
Material Parameters ◽  
Constant Content

This article presents results of fire spalling tests on small concrete slabs and studies of material parameters that may increase its occurrence. Experimental techniques enabling to study and determination of material features are presented and discussed. Experimental studies on spalling behaviour of elements were carried out on seven different concrete mixes with constant content of cement paste and mortar. Research aimed at determining influence of the following parameters: w/c ratio (0.30; 0.45; 0.60), cement type (CEM I, CEM III) and type of aggregates (riverbed gravel, granite, basalt) on fire concrete spalling. Paper discusses also the influence of cold rim that forms while testing slab-like element is subjected to one-side heating.

Numerical and Experimental Studies of Ballistic Compression Process in a Soft Recovery System

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Girijesh Mathur ◽  
Nachiketa Tiwari ◽  
Neha Chaturvedi
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Experimental Studies ◽  
Pressure Rise ◽  
Sensitivity Analyses ◽  
Design Parameters ◽  
Strong Positive Correlation ◽  
Compression Process ◽  
Recovery System ◽  
Two Parameters

Abstract A ballistic compression type soft recovery system can stop a free-flying supersonic projectile in a controlled manner. The moment such a projectile enters the System, a normal shock gets created and starts hurtling down, to kick off a train of events involving shock reflections, diaphragm rupture, shock merger, creation of new shocks and contact discontinuities, and expansion wave-shock interactions. A good understanding of these phenomena and sensitivity of the System's performance to changes in design parameters is needed to design an efficient soft recovery system. Unfortunately, not much information is available about this. The present work fills this gap. We have developed a numerical model for the system and conducted sensitivity analyses using four design parameters; pressure, molecular weight, the ratio of specific heats, and temperature of gas used in the system. We show that while there is a strong, positive correlation between the first two parameters and projectile deceleration, the other two parameters are less critical. We conducted experiments to corroborate our conclusions and improve our numerical model. Post such improvements, we found the difference between simulation and experimental data to be acceptable. Experiments also confirmed the findings of our sensitivity studies. Finally, we conducted a two-dimensional finite volume analysis to understand the reasons underlying the residual difference between our numerical and experimental data. We show that such differences are due to pressure-rise at a point once a shock passes by it, and such a rise in pressure is attributable to boundary layer effects.

scholarly journals Impact of Fischer-Tropsch diesel and methanol blended fuel on diesel engine performance

2019 ◽  
Vol 23 (5 Part A) ◽  
pp. 2651-2658
Author(s):  
Zhifei Wu ◽  
Tie Wang ◽  
Peng Zuo ◽  
Muhammad Iqbal
Keyword(s):  
Diesel Fuel ◽  
Ignition Delay ◽  
Experimental Studies ◽  
Pressure Rise ◽  
Engine Performance ◽  
Vibration Acceleration ◽  
Fischer Tropsch ◽  
Blended Fuel ◽  
The Impact ◽  
Ignition Delay Period

This paper discusses the impact of Fischer-Tropsch (F-T) diesel and methanol blended fuel, tentative engine was operated with fueled having F-T diesel and methanol blended fuel to compare the combustion and vibration characteristics. For this, 4100QBZL turbocharged diesel having parameters of F-T diesel fuel, FM5, FM10, FM15 methanol volume content was 5%, 10%, and 15%, respectively, have been selected for the experiment. Experimental studies have shown that when fueling with F-T diesel fuel, the ignition delay is shorter, the premixed combustion rate peak is lower, and vibration acceleration increases slightly than diesel fuel. Compared to the pure F-T diesel, the blended fuel has longer ignition delay period, higher the rate of pressure rise, combustion start point delayed, burning capacity increase, such as thermal efficiency is improved and vibration acceleration increased significantly.

Understanding the Flow Behavior in a Low Hub-Tip Ratio, High Aspect Ratio Contra-Rotating Axial Fan Stage

2012 ◽  
Author(s):  
Chetan S. Mistry ◽  
A. M. Pradeep
Keyword(s):  
Aspect Ratio ◽  
Total Pressure ◽  
Numerical Study ◽  
Flow Behavior ◽  
Experimental Studies ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Axial Fan ◽  
Stall Margin

This paper discusses the results of a parametric study of a pair of contra-rotating axial fan rotors. The rotors were designed to deliver a mass flow of 6 kg/s at 2400 rpm. The blades were designed with a low hub-tip ratio of 0.35 and an aspect ratio of 3.0. Numerical and experimental studies were carried out on these contra-rotating rotors operating at a Reynolds number of 1.25 × 105 (based on blade chord). The axial spacing between the rotors was varied between 50 to 120 % of the chord of rotor 1. The performance of the rotors was evaluated at each of these spacing at design and off-design speeds. The results from the numerical study (using ANSYS CFX) were validated using experimental data. In spite of certain limitations of CFD under certain operating conditions, it was observed that the results agreed well with those from the experiments. The performance of the fan was evaluated based on the variations of total pressure, velocity components and flow angles at design and off-design operating conditions. The measurement of total pressure, flow angles etc. are taken upstream of the first rotor, between the two rotors and downstream of the second rotor. It was observed that the aerodynamics of the flow through a contra rotating stage is significantly influenced by the axial spacing between the rotors and the speed ratio of the rotors. With increasing speed ratios, the strong suction generated by the second rotor, improves the stage pressure rise and the stall margin. Lower axial spacing on the other hand, changes the flow incidence to the second rotor and thereby improves the overall performance of the stage. The performance is investigated at different speed ratios of the rotors at varying axial spacing.

Role of vasopressin in clinical hypertension and congestive cardiac failure: interaction with the sympathetic nervous system

1991 ◽  
Vol 37 (10) ◽  
pp. 1828-1830 ◽  
Author(s):  
H Gavras
Keyword(s):  
Blood Pressure ◽  
Nervous System ◽  
Sympathetic Nervous System ◽  
Vascular Resistance ◽  
Blood Pressure Response ◽  
Experimental Studies ◽  
Pressure Rise ◽  
Intravenous Bolus ◽  
Sympathetic Nervous ◽  
Failure Interaction

Abstract The pressor action of vasopressin (AVP) in humans was investigated with the specific anti-vasopressor V1 antagonist d(CH2)5-O(Me)-Tyr-AVP. A single 0.5-mg intravenous bolus of this agent inhibited the pressor effect of AVP by about 80%. Normally hydrated humans had no blood pressure response to this dose, but this agent did prevent the blood pressure rise in response to exogenous AVP given in doses up to 200 milli-units/kg. Patients with severe hypertension, especially that associated with end-stage renal disease, tended to respond with moderate increases in blood pressure and plasma AVP after sodium overload and had a modest blood pressure fall (10-20 mmHg) in response to a single intravenous bolus of the AVP antagonist. Patients with an impaired sympathetic nervous system had increased sensitivity to the pressor action of AVP, in keeping with knowledge derived from experimental studies. These data suggest an interaction between AVP and alpha-adrenergic function, whereby the latter tends to attenuate the pressor action of AVP although it facilitates the release of AVP in response to various stimuli. In patients with congestive heart failure, the direct pressor action of AVP appears to contribute to increased systemic vascular resistance in about 30% of cases, i.e., those with plasma AVP concentrations well above the normal range. In these subjects, circulating AVP concentrations correlated with a decrease in vascular resistance in response to the V1 antagonist.

Effect of Speed Ratio and Axial Spacing Variations on the Performance of a High Aspect Ratio, Low Speed Contra-Rotating Fan

2012 ◽  
Author(s):  
Chetan S. Mistry ◽  
A. M. Pradeep
Keyword(s):  
Aspect Ratio ◽  
Numerical Simulations ◽  
High Aspect Ratio ◽  
Total Pressure ◽  
Experimental Studies ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Stall Margin ◽  
Low Speed

This paper explores the effect of speed ratio and axial spacing between high aspect ratio, low speed contra-rotating pair rotors on their aerodynamic performance. The blades were designed with a low hub-tip ratio of 0.35 and an aspect ratio of 3.0. Numerical and experimental studies are carried out on these contra-rotating rotors operating at a Reynolds number of 1.258 × 105 (based on blade chord). The first and second rotors were designed to develop a pressure rise of 1100 Pa and 900 Pa, respectively, for total mass flow rate of 6 kg/s when both operating at a design speed of 2400 rpm. The performance of the fan was evaluated based on variations of total pressure and flow angles at off-design operating conditions. The measurementsof total pressure rise, flow angles etc. are taken upstream of the first rotor and in between the two rotors and downstream of the second rotor. The performance of the contra rotating stage is mainly influenced by the axial spacing between the rotors and speed ratio of both the rotors. The study reveals that the aerodynamics of the contra-rotating stage and stall margin is significantly affected by both the speed ratio as well as the axial spacing between the rotors. It was found that with increasing the speed ratio, the strong suction generated by the second rotor, improves the stage pressure rise and stall margin. Lower axial spacing changes the flow incidence to the second rotor and thereby improves the overall performance of the stage. This however, is accompanied by an increased noise level. The performance is investigated at different speed ratios of the rotors at varying axial spacing. Detailed numerical simulations have been conducted using ANSYS CFX13© using mixing plane approach between rotors. Numerical simulations are compared with experimental results at off-design conditions. These results are validated using the experimental data. Numerical simulations are expected to provide deeper insight into the flow physics of contra-rotating rotors which may be difficult to capture experimentally.

An experimental investigation of a centrifugal compressor with hub vane diffusers

1997 ◽  
Vol 211 (5) ◽  
pp. 411-427 ◽  
Author(s):  
N Sitaram ◽  
J M Issac
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Coefficient ◽  
Experimental Studies ◽  
Pressure Rise ◽  
Leading Edge ◽  
Maximum Flow ◽  
Throat Region ◽  
Volume Range ◽  
Vane Diffuser

The present investigation reports results of experimental studies on a centrifugal compressor equipped with hub vane diffusers. The diffuser vane height ( h/b) is varied as follows: 0 (vaneless), 0.2, 0.3, 0.4 and 1 (vane). The experiments were carried out on a low specific speed centrifugal compressor with a radial tipped impeller with an inducer at the inlet. The measurements consist of determining performance characteristics, measuring static pressures on the hub and shroud and flow traverses with a precalibrated cobra probe at the diffuser exit over one passage at five flow coefficients, viz. φ = 0.23 (near surge), 0.34 (near peak pressure rise), 0.45, 0.60 and 0.75 (near maximum flow). The peak energy coefficient is maximum for the hub vane diffuser with an h/b ratio of 0.2. The hub vane diffusers have a wider operating range than the vane diffuser. At high flow coefficients, the static pressure rise is substantially low at the throat region of the vane diffuser as the incidence on to the vane leading edge is very high. The mass averaged static pressure coefficient is high in the low-volume range for the hub vane diffuser of h/b = 0.3, but in the high-volume range it is high for the vaneless diffuser.

Experimental Study on Different Tip Clearance of Low-Speed Axial Fan

2021 ◽  
Author(s):  
Ming Zhang ◽  
Jia Li ◽  
Xu Dong ◽  
Dakun Sun ◽  
Xiaofeng Sun
Keyword(s):  
Experimental Studies ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Signal Spectrum ◽  
Tip Clearance Flow ◽  
Low Speed ◽  
Clearance Flow ◽  
Casing Pressure

Abstract Tip clearance flow is not only the source of undesirable noise but also a potential indicator for critical operating conditions with rotating stall or surge. It can induce blade vibration, which would cause premature blade failure when the vibration is strong enough. The paper presents experimental studies on the effects of tip clearance on the stall inception process in a low-speed high-load single stage fan with different tip clearance. From the point of view of flow range, it has been proved by computations that there is an optimal gap value, and an explanation is given according to different stall mechanisms of large and small tip clearance. However, the experiment of no tip clearance is not easy to achieve. In this experiment, a wearable soft wall casing was used to achieve “zero clearance”, and an explicit conclusion was obtained. The pressure rise and efficiency are improved at small tip clearance. Instantaneous Casing Pressure Field Measurement was carried out: instantaneous casing pressure fields were measured by 9 high response pressure transducers mounted on the casing wall. At the near stall point with large tip clearance, a narrow band increase of the amplitudes in the frequency spectrum at roughly half of the blade passing frequency can be observed according to the spectrum of static pressure at points on the endwall near the leading-edge and above the rotor. This phenomenon was explained from two aspects: tip clearance flow structure and pressure signal spectrum.

Laser Based Ignition of Natural Gas-Air Mixtures

2003 ◽  
Author(s):  
Sreenath B. Gupta ◽  
Raj R. Sekar ◽  
Zhiyue Xu ◽  
Keng H. Leong ◽  
Claude B. Reed ◽  
...  
Keyword(s):  
Natural Gas ◽  
Focal Length ◽  
Single Point ◽  
Experimental Studies ◽  
Pressure Rise ◽  
Specific Power ◽  
Beam Polarization ◽  
Full Potential ◽  
Natural Gas Engines ◽  
High Specific Power

In current natural gas engines, lean operation to reduce NOx emissions along with the requirement to maintain high specific power results in in-cylinder conditions that demand spark voltages beyond the capabilities of present ignition systems. Unable to overcome such limitations, presently these engines are operated well below their full potential (about 15% less). Additionally, undue maintenance demands are placed for the upkeep of ignition systems. Laser based ignition (LBI) on the other hand, overcomes the above limitations and potentially reduces emissions and increases efficiency. Experimental studies were performed to identify such potential benefits while using lasers to ignite quiescent methane-air mixtures. Quiescent methane-air mixtures at various conditions (φ = 0.6–1.0, fill pressure = 2–20 Bar) were established in a pressure vessel and were ignited using lasers and by conventional ignition systems. Such tests showed lasers to ignite mixtures with initial pressures 30% higher than those limiting ignition by conventional ignition systems. However, extension of the lean ignition limit appeared to be marginal and was defined by φ = 0.675. Also, for single point ignition followed here, the rates of pressure rise and ignition delays were identical and did not depend upon the method of ignition. Other characteristics in terms of (a) effect of focal length, (b) effect of fuel composition, and (c) effect of laser beam polarization are presented. In practice, in-cylinder conditions such as turbulence, velocity and temperature are likely to have an additional bearing on the ignition characteristics. Such effects will be determined through future investigations.

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