scholarly journals Propagation Velocity of Flames in Inert-Diluted Stoichiometric Propane-Air Mixtures: Pressure and Temperature Dependence

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 997
Author(s):  
Venera Giurcan ◽  
Maria Mitu ◽  
Codina Movileanu ◽  
Domnina Razus ◽  
Dumitru Oancea
Keyword(s):  
Propagation Velocity ◽  
Dynamic Pressure ◽  
Initial Pressure ◽  
Pressure Increase ◽  
Velocity Variation ◽  
Flame Velocity ◽  
Gaseous Mixtures ◽  
Mild Combustion ◽  
Pressure Time ◽  
Specific Safety

The flammable propane–air mixtures raise specific safety and environmental issues in the industry, storage, handling and transportation; therefore dilution of such mixtures has gained significant importance from the viewpoint of fire safety, but also due to nitrogen oxide’s emission control through flameless/mild combustion. In this paper, the propagation of the flame in C3H8-air-diluent stoichiometric gaseous mixtures using Ar, N2 and CO2 as diluents was investigated. Data were collected from dynamic pressure-time records in spherical propagating explosions, centrally ignited. The experiments were done on stoichiometric C3H8-air + 10% diluent mixtures, at initial pressures within 0.5–2.0 bar and initial temperatures within 300–423 K. The flame velocity was determined from laminar burning velocities obtained using the pressure increase in the incipient stage of flame propagation (when the pressure increase is lower than the initial pressure). The experimental propagation velocities were compared with computed ones obtained from laminar burning velocities delivered by kinetic modeling made using the GRI mechanism (version 3.0) with 1D COSILAB package. The thermal and baric coefficients of propagation velocity variation against the initial temperature and pressure are reported and discussed.

scholarly journals Evaluation of cushions using dynamic pressure measurement

1991 ◽  
Vol 15 (3) ◽  
pp. 232-240 ◽  
Author(s):  
C. A. Bar
Keyword(s):  
Dynamic Pressure ◽  
Pressure Sores ◽  
Patient Assessment ◽  
Pressure Monitoring ◽  
Time Profiles ◽  
Pressure Time ◽  
Subject Variability ◽  
Dynamic Pressure Measurement ◽  
Ischial Tuberosities ◽  
Spinal Cord Injured

Reduction of pressures generated in the tissues overlying the ischial tuberosities is an important measure for predicting a cushion's effectiveness. In particular, the pressure-time relationship is significant in the prevention of pressure sores. In this study a dynamic pressure monitoring system was used to obtain pressure-time profiles for 25 spinal cord injured subjects. Each subject tested three types of cushion (Foam, Gel (Aberdeen) and Roho) for periods of two hours each during which routine activities were performed. Results obtained were broadly comparable with previous studies. Average pressures were: Foam 87.6mmHg (11.6kPa); Gel 68.6mmHg (9kPa) and Roho 54.6mmHg (6.7kPa). Pressure-time histograms are presented for three subjects for each cushion. These show inter-subject variability on the same cushion as well as intra-subject variability on different cushions. Therefore individual patient assessment is important in providing the most appropriate cushion. Dynamic pressure monitoring allows the pattern of pressure variation to be determined and hence the potential effectiveness of the cushion.

Sustainable inspiratory pressures over varying flows, volumes, and duty cycles

1990 ◽  
Vol 69 (5) ◽  
pp. 1875-1882 ◽  
Author(s):  
T. L. Clanton ◽  
B. T. Ameredes ◽  
D. B. Thomson ◽  
M. W. Julian
Keyword(s):  
Tidal Volume ◽  
Duty Cycle ◽  
Dynamic Pressure ◽  
Breathing Patterns ◽  
Transdiaphragmatic Pressure ◽  
Lung Inflation ◽  
Duty Cycles ◽  
Pressure Time ◽  
Endurance Tests ◽  
Normal Humans

This study identifies the influence of flow (0.5-2.0 l/s), duty cycle (0.29-0.57), and tidal volume (1.08-2.16 liters) on sustainable inspiratory muscle pressure (Pmus) and transdiaphragmatic pressure (Pdi) development. Six normal humans performed endurance tests using an isoflow method, which allowed for measurements of maximum dynamic Pmus and Pdi, with controlled lung inflation. The subjects repeated maximum dynamic voluntary inspirations for 10 min. Pressures dropped exponentially from initial measurements at rest (Pmusi or Pdi) to sustainable values (Pmus or Pdis). As flow and tidal volume increased, maximum initial and sustainable pressures decreased significantly. However, at a constant duty cycle, the sustainable dynamic pressures remained predictable fractions of initial dynamic pressures (i.e., Pmuss/Pmusi or Pdis/Pdii), regardless of changes in flow and tidal volume. In contrast, as duty cycle increased, the sustainable fractions significantly decreased for both Pdi and Pmus. For example, at a duty cycle of 0.29, Pmuss/Pmusi was approximately 0.71, and at a duty cycle of 0.57, Pmuss/Pmusi was approximately 0.62. Calculated sustainable pressure-time indexes varied significantly between 0.16 to 0.32 for Pmus and 0.11 to 0.22 for Pdi over the breathing patterns studied. We conclude that 1) the maximum dynamic pressure that can be sustained at a given duty cycle is a predictable fraction of the maximum dynamic pressure that can be generated at rest when measured under the same conditions of inspiration and 2) the sustainable fraction of initial dynamic pressure significantly decreases with increasing duty cycle.

scholarly journals EXPERIMENTAL DETERMINATION OF LAMINAR BURNING VELOCITY OF BIOGAS AT PRESSURES UP TO 5 BAR

2018 ◽  
Vol 17 (2) ◽  
pp. 03
Author(s):  
L. Pizzuti ◽  
C. A. Martins ◽  
L. R. Santos
Keyword(s):  
Equivalence Ratio ◽  
Burning Velocity ◽  
Initial Pressure ◽  
Experimental Setup ◽  
Laminar Burning Velocity ◽  
Gaseous Mixtures ◽  
Experimental Procedure ◽  
Constant Volume Combustion Chamber ◽  
Percentage Standard Deviation

This paper presents a very detailed description of a new cylindrical constant volume combustion chamber designed for laminar burning velocity determination of gaseous mixtures at ambient temperature and initial pressure up to 6 bar. The experimental setup, the experimental procedure and the determination of the range of flame radius for laminar burning determination are all described in details. The laminar burning velocity of twelve synthetic biogas mixtures has been studied. Initial pressure varying between 1 and 5 bar, equivalence ratios, f, between 0.7 and 1.1 and percentage dilution, with a mixture of CO2 and N2, between 35 and 55% have been considered. Five experiments were run for each mixture providing a maximum percentage standard deviation of 8.11%. However, for two third of the mixtures this value is lower than 3.55%. A comparison with simulation using PREMIX for both GRI-Mech 3.0 and San Diego mechanisms has provided closer agreement for mixtures with equivalence ratio closer to stoichiometry whereas for f = 0.7 the deviation is larger than 15% for all pressures. Mixtures with lower equivalence ratio, higher dilution percentage and higher initial pressure presents the lower values of laminar burning velocity.

Investigation of propagation modes and temperature/velocity variation on unstable combustion synthesis

2002 ◽  
Vol 17 (12) ◽  
pp. 3213-3221 ◽  
Author(s):  
H. P. Li
Keyword(s):  
Activation Energy ◽  
Combustion Synthesis ◽  
Combustion Front ◽  
Propagation Velocity ◽  
Combustion Temperature ◽  
Front Propagation ◽  
Combustion Reaction ◽  
Velocity Variation ◽  
Material Synthesis ◽  
Unstable Combustion

Combustion synthesis/micropyretic synthesis is a technique in which material synthesis is accomplished by the propagation of a combustion front across the sample. In some cases, the combustion front may propagate in an unstable mode where the propagation velocity and combustion temperature of the combustion front are altered periodically. In this study, the processing conditions leading to unstable combustion reaction were first studied theoretically. The boundary temperatures separating stable and unstable reactions were then determined. The numerical analysis showed that the combustion temperature and the propagation velocity changed periodically during unstable combustion. As the combustion reaction became unstable, the average propagation velocity and the oscillatory frequency of front propagation decreased. The products of unstable combustion synthesis possessed the banded structures, implying the occurrence of the unstable oscillatory propagation, as demonstrated experimentally. In this study, high activation energy combustion (Ti + 2B reaction) and low activation energy combustion (Ni + Al reaction) were both chosen to illustrate the effect of unstable combustion. It is the first time the experimental and numerical results were combined to investigate the temperature and propagation velocity variations during unstable combustion.

A Method of Seawater Sound Velocity Measurement Based on the Transit-Time

2013 ◽  
Vol 816-817 ◽  
pp. 439-442
Author(s):  
Bao Feng Zhang ◽  
Zhen Hai Liu ◽  
Xiao Ma
Keyword(s):  
Sound Velocity ◽  
Influencing Factors ◽  
High Precision ◽  
Transit Time ◽  
Precision Measurement ◽  
Propagation Velocity ◽  
Velocity Measurement ◽  
Velocity Variation ◽  
High Precision Measurement ◽  
Ultrasound Propagation

In the prospects of maritime development, the accuracy requirements of the marine sonar equipment also getting higher and higher, it is particularly important to measure the sound velocity in seawaters(ultrasound propagation velocity in seawater) in high-precision, in this experiment, basing on the seawater sound velocity variation influencing factors, proposing a method of average measuring the sound velocity of seawater based on STM32 and TDC-GP21 transit-time, The results of the experiment show that this method can be high-precision measurement of the size of the seawater sonic，meet the seawater sound velocity measurement requirements.

The gaseous oxidation of 2-methyl-but-2-ene. I. Kinetic and analytical studies

1961 ◽  
Vol 262 (1310) ◽  
pp. 318-327 ◽  
Keyword(s):  
Double Bond ◽  
Methyl Alcohol ◽  
Initial Pressure ◽  
Pressure Increase ◽  
Reaction Products ◽  
Initial Attack ◽  
Primary Reaction ◽  
Slow Combustion ◽  
Propyl Ketone ◽  
Parallel Fashion

In the slow combustion of 2-methyl-but-2-ene at ca . 250 °C, an initial pressure decrease, which represents the formation of peroxidic intermediates, is followed by an autocatalytic pressure increase during which little olefin is consumed and the main processes are break ­ down and further oxidation of primary reaction products. Acetone and acetaldehyde are the principal early non-peroxidic products and these are formed initially in equivalent quantities and in closely parallel fashion. Methyl iso propyl ketone is produced in somewhat smaller amounts and methyl alcohol, which appears comparatively late in the reaction, probably arises from the oxidation of acetaldehyde. The results suggest that the predominant mode of initial attack of the olefin is addition of oxygen to the double bond followed by decomposition of the resulting cyclic peroxides, although some hydroperoxylation also occurs.

Fuel Consumption Measurement With Pulsating Flow

2003 ◽  
Author(s):  
Thomas Flauger ◽  
Stephen A. Ifft
Keyword(s):  
Fuel Consumption ◽  
Reverse Flow ◽  
Dynamic Pressure ◽  
Pressure Variation ◽  
Velocity Variation ◽  
Injection Pump ◽  
Measurement Results ◽  
Pressure Pulses ◽  
Short Time ◽  
The Impact

This paper describes the impact of pressure pulsation on a system for fuel consumption measurement. The generation of pressure pulses by the injection pump(s) on the low pressure side of Diesel engines for power generation, ship propulsion or rail traction is described. Pressure values at the location of the fuel consumption measurement system are shown. Along with measurement results of the dynamic pressure variation over a flowmeter. The relation between pressure variation and the pulse output of the flowmeter is presented. These measurements quantify the velocity variations of the fuel. With help of the measurement results, the reason for temporary reverse flow is explained. We present a system for engine related fuel consumption measurement that withstands the impact of mechanical force caused by pressure pulses, which follows the velocity variation of the fuel and which indicates and calculates short-time reverse flow to achieve an accurate measurement result.

scholarly journals Further experiments on explosions in gaseous mixtures of acetylene, of hydrogen and of pentane

1927 ◽  
Vol 116 (775) ◽  
pp. 516-529 ◽  
Keyword(s):  
Initial Pressure ◽  
Detonation Waves ◽  
Gaseous Mixtures ◽  
Velocity Of Detonation ◽  
Set Up

An account of experiments on detonation in gaseous mixtures of acetylene and pentane has already been published. Certain further observations are here recorded as an addendum to the former papers. (a) Influence of Pressure on Velocity of Detonation . It was mentioned on p. 157 of the second paper referred to, that further measurements of the velocities of the detonation waves set up in the explosive mixtures investigated were necessary to determine the precise extent of the increase in velocity occasioned by rise of initial pressure.

Simplified Methodology for Analysis of Reflected Detonation and DDT: Part 1 — Elastic Analysis

2014 ◽  
Author(s):  
Thomas C. Ligon ◽  
David J. Gross ◽  
Stephen D. Ahnert ◽  
John C. Minichiello
Keyword(s):  
Initial Conditions ◽  
Time History ◽  
Initial Pressure ◽  
Propagation Distance ◽  
Element Model ◽  
Simplified Approach ◽  
Pressure Time ◽  
Unburned Fuel ◽  
Reflecting Surface ◽  
Peak Pressures

This paper introduces a simplified approach for analyzing local elastic hoop response of piping to reflected gaseous detonations and deflagration-to-detonation transitions (DDT). A consequence associated with gaseous explosions is the potential for DDT to occur near the end of a closed pipe or gas pocket. As an accelerating deflagration flame approaches a closed end, the unburned fuel ahead of the flame front is compressed to an elevated initial pressure. This process is often referred to as pressure piling or pre-compression, and the combination of detonation reflection with the elevated initial pressure, can produce extremely high peak pressures and large values of impulse. In this paper, the event where DDT occurs immediately ahead of the reflecting surface is referred to as a reflected-DDT (R-DDT). In addition to gas mixture and initial conditions, the peak pressure and shape of the pressure time-history associated with a reflected detonation or DDT is a function of the detonation propagation distance prior to reflection and the relative distance between the ignition location, the DDT location, and the reflecting surface. An empirical pressure time-history has been developed using pressure data from approximately 190 explosion tests using hydrogen and nitrous oxide mixtures in 2-inch and 4-inch pipe to describe events ranging from fully-developed reflected detonations to R-DDTs. The empirical model of the pressure time-history was validated by comparing measured elastic hoop strains to finite-element model predictions using the pressure time-history model. Part 2 of this paper compares the methodology to plastic response data.

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