scholarly journals Shock Tube Combustion Analysis

2021 ◽  
Author(s):  
Claudio Marcio Santana ◽  
Jose Eduardo Mautone Barros
Keyword(s):  
High Pressure ◽  
Shock Tube ◽  
Soybean Oil ◽  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Low Pressure ◽  
Pressure Chamber ◽  
Ignition Delay Times ◽  
Delay Times

The shock tube is a metal tube that the gas at low pressure and high pressure are separated by a diaphragm. When the diaphragm (make of material copper and aluminum) breaks on predetermined conditions (high pressure in this case) produces shock waves that move from the high-pressure chamber (known the compression chamber or Driver section) for low pressure chamber (known the expansion chamber or Driven section). The objective of this work is the correlate the ignition delay times of convectional Diesel and Biodiesel from soybean oil measured in a shock tube. The results were correlated with the cetane number of respective fuels and compared with the ignition delay times of Diesel and Biodiesel with cetane numbers of known. The ignition delay time of biodiesel from soybean oil was approximately three times greater than the ignition delay time of convectional Diesel. The contribution of this work is that it shows why pure biodiesel should not be used as substitutes for Diesel compression ignition engines without any major changes in the engines.

Interpretation of Flow Reactor Based Ignition Delay Measurements

2009 ◽  
Author(s):  
David Beerer ◽  
Vincent McDonell ◽  
Scott Samuelsen ◽  
Leonard Angello
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Residence Time ◽  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Flow Reactor ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Recirculation Zones

Compositional variation of global gas supplies is becoming a growing concern. Both the range and rate-of-change of this variation is expected to increase as global markets for Liquefied Natural Gas (LNG) continue to expand. Greater fuel composition variation poses increased operational risk to gas turbine engines employing lean premixed combustion systems. Information on ignition delay at high pressure and intermediate temperatures is valuable for lean premixed gas turbine design. In order to avoid autoignition of the fuel/air mixture within the premixer, the ignition delay time must be greater than the residence time. Evaluating the residence time is not a straight forward task because of the complex aerodynamics due to recirculation zones, separation regions, and boundary layers effects which may create regions where the local residence times may be longer than the bulk or average residence time. Additionally, reliable experiments on ignition delay at gas turbine conditions are difficult to conduct. Devices for testing include shock tubes, rapid compression machine and flow reactors. In a flow reactor ignition delay data are commonly determined by measuring the distance from the fuel injector to the reaction front (L) and dividing it by the bulk or average flow velocity (U) under steady flow conditions to obtain a bulk residence time which is assumed to be equal to the ignition delay time. However this method is susceptible to the same boundary layer effects or recirculation zones found in premixers. An alternative method for obtaining ignition delay data in a flow reactor is presented herein, where ignition delay times are obtained by measuring the time difference between fuel injection and ignition using high speed instrumentation. Ignition delay times for methane, ethane and propane at gas turbine conditions were in the range of 40–500 ms. The results obtained show excellent agreement with recently proposed chemical mechanisms for hydrocarbons at low temperature/high pressure conditions.

Ignition Delay Times of High Pressure Oxy-Methane Combustion With High Levels of CO2 Dilution

2017 ◽  
Author(s):  
Owen Pryor ◽  
Batikan Koroglu ◽  
Samuel Barak ◽  
Joseph Lopez ◽  
Erik Ninnemann ◽  
...  
Keyword(s):  
Shock Tube ◽  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Current Data ◽  
Validation Data ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Kinetic Mechanisms ◽  
Time Histories

Ignition delay times and methane species time-histories were measured for methane/O2 mixtures in a high CO2 diluted environment using shock tube and laser absorption spectroscopy. The experiments were performed between 1300 K and 2000 K at pressures between 1 and 31 atm. The experimental mixtures were conducted at an equivalence ratio of 1 with CH4 mole fractions ranging from 3.5%–5% and up to 85% CO2 with a bath of argon gas as necessary. The ignition delay times and methane time histories were measured using pressure, emission, and laser diagnostics. Predictive ability of two literature kinetic mechanisms (GRI 3.0 and ARAMCO Mech 1.3) was tested against current data. In general, both mechanisms performed reasonably well against ignition delay time data. The methane time-histories showed good agreement with the mechanisms for most of the conditions measured. A correlation for ignition delay time was created taking into the different parameters showing that the ignition activation energy for the fuel to be 49.64 kcal/mol. Through a sensitivity analysis, CO2 is shown to slow the overall reaction rate and increase the ignition delay time. To the best of our knowledge, we present the first shock tube data during ignition of methane under these conditions. Current data provides crucial validation data needed for development of future methane/CO2 kinetic mechanisms.

scholarly journals High-Speed Imaging and Measurements of Ignition Delay Times in Oxy-Syngas Mixtures With High CO2 Dilution in a Shock Tube

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Samuel Barak ◽  
Owen Pryor ◽  
Joseph Lopez ◽  
Erik Ninnemann ◽  
Subith Vasu ◽  
...  
Keyword(s):  
Shock Tube ◽  
Ignition Delay ◽  
Delay Time ◽  
High Speed ◽  
Ignition Delay Time ◽  
High Speed Imaging ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Syngas Combustion ◽  
End Wall

In this study, syngas combustion was investigated behind reflected shock waves in order to gain insight into the behavior of ignition delay times and effects of the CO2 dilution. Pressure and light emissions time-histories measurements were taken at a 2 cm axial location away from the end wall. High-speed visualization of the experiments from the end wall was also conducted. Oxy-syngas mixtures that were tested in the shock tube were diluted with CO2 fractions ranging from 60% to 85% by volume. A 10% fuel concentration was consistently used throughout the experiments. This study looked at the effects of changing the equivalence ratios (ϕ), between 0.33, 0.5, and 1.0 as well as changing the fuel ratio (θ), hydrogen to carbon monoxide, from 0.25, 1.0, and 4.0. The study was performed at 1.61–1.77 atm and a temperature range of 1006–1162 K. The high-speed imaging was performed through a quartz end wall with a Phantom V710 camera operated at 67,065 frames per second. From the experiments, when increasing the equivalence ratio, it resulted in a longer ignition delay time. In addition, when increasing the fuel ratio, a lower ignition delay time was observed. These trends are generally expected with this combustion reaction system. The high-speed imaging showed nonhomogeneous combustion in the system; however, most of the light emissions were outside the visible light range where the camera is designed for. The results were compared to predictions of two combustion chemical kinetic mechanisms: GRI v3.0 and AramcoMech v2.0 mechanisms. In general, both mechanisms did not accurately predict the experimental data. The results showed that current models are inaccurate in predicting CO2 diluted environments for syngas combustion.

High-Speed Imaging and Measurements of Ignition Delay Times in Oxy-Syngas Mixtures With High CO2 Dilution in a Shock Tube

2017 ◽  
Author(s):  
Samuel Barak ◽  
Owen Pryor ◽  
Joseph Lopez ◽  
Erik Ninnemann ◽  
Subith Vasu ◽  
...  
Keyword(s):  
Shock Tube ◽  
Ignition Delay ◽  
Delay Time ◽  
High Speed ◽  
Ignition Delay Time ◽  
High Speed Imaging ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Syngas Combustion ◽  
End Wall

In this study, syngas combustion was investigated behind reflected shock waves in order to gain insight into the behavior of ignition delay times and effects of the CO2 dilution. Pressure and light emissions time-histories measurements were taken at a 2cm axial location away from the end wall. High-speed visualization of the experiments from the end wall was also conducted. Oxy-syngas mixtures that were tested in the shock tube were diluted with CO2 fractions ranging from 60% – 85% by volume. A 10% fuel concentration was consistently used throughout the experiments. This study looked at the effects of changing the equivalence ratios (ϕ), between 0.33, 0.5, and 1.0 as well as changing the fuel ratio (θ), hydrogen to carbon monoxide, from 0.25, 1.0 and 4.0. The study was performed at 1.61–1.77 atm and a temperature range of 1006–1162K. The high-speed imaging was performed through a quartz end wall with a Phantom V710 camera operated at 67,065 frames per second. From the experiments, when increasing the equivalence ratio, it resulted in a longer ignition delay time. In addition, when increasing the fuel ratio, a lower ignition delay time was observed. These trends are generally expected with this combustion reaction system. The high-speed imaging showed non-homogeneous combustion in the system, however, most of the light emissions were outside the visible light range where the camera is designed for. The results were compared to predictions of two combustion chemical kinetic mechanisms: GRI v3.0 and AramcoMech v2.0 mechanisms. In general, both mechanisms did not accurately predict the experimental data. The results showed that current models are inaccurate in predicting CO2 diluted environments for syngas combustion.

scholarly journals High Pressure Shock Tube Ignition Delay Time Measurements During Oxy-Methane Combustion With High Levels of CO2 Dilution

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Owen Pryor ◽  
Samuel Barak ◽  
Joseph Lopez ◽  
Erik Ninnemann ◽  
Batikan Koroglu ◽  
...  
Keyword(s):  
Shock Tube ◽  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Current Data ◽  
Validation Data ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Kinetic Mechanisms ◽  
Time Histories

Ignition delay times and methane species time-histories were measured for methane/O2 mixtures in a high CO2 diluted environment using shock tube and laser absorption spectroscopy. The experiments were performed between 1300 K and 2000 K at pressures between 6 and 31 atm. The test mixtures were at an equivalence ratio of 1 with CH4 mole fractions ranging from 3.5% to 5% and up to 85% CO2 with a bath of argon gas as necessary. The ignition delay times and methane time histories were measured using pressure, emission, and laser diagnostics. Predictive ability of two literature kinetic mechanisms (gri 3.0 and aramco mech 1.3) was tested against current data. In general, both mechanisms performed reasonably well against measured ignition delay time data. The methane time-histories showed good agreement with the mechanisms for most of the conditions measured. A correlation for ignition delay time was created taking into account the different parameters showing the ignition activation energy for the fuel to be 49.64 kcal/mol. Through a sensitivity analysis, CO2 is shown to slow the overall reaction rate and increase the ignition delay time. To the best of our knowledge, we present the first shock tube data during ignition of methane/CO2/O2 under these conditions. Current data provides crucial validation data needed for the development of future kinetic mechanisms.

Ignition delay times of methane fuels at thrust chamber conditions in an ultra-high-pressure shock tube

2022 ◽  
Author(s):  
Michael Pierro ◽  
Andrew Laich ◽  
Justin J. Urso ◽  
Cory Kinney ◽  
Subith Vasu ◽  
...  
Keyword(s):  
High Pressure ◽  
Shock Tube ◽  
Ignition Delay ◽  
Pressure Shock ◽  
Thrust Chamber ◽  
Ultra High Pressure ◽  
Ignition Delay Times ◽  
Delay Times

Experimental Study and Modeling of Autoignition of Natural Gas/Air-Mixtures Under Gas Turbine Relevant Conditions

2005 ◽  
Author(s):  
Andreas Koch ◽  
Clemens Naumann ◽  
Wolfgang Meier ◽  
Manfred Aigner
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Ignition Delay ◽  
Delay Time ◽  
High Speed ◽  
Ignition Delay Time ◽  
Evaluation Procedure ◽  
Ignition Process ◽  
Ignition Delay Times ◽  
Delay Times

The objective of this work was the improvement of methods for predicting autoignition in turbulent flows of different natural gas mixtures and air. Measurements were performed in a mixing duct where fuel was laterally injected into a turbulent flow of preheated and pressurized air. To study the influence of higher order hydrocarbons on autoignition, natural gas was mixed with propane up to 20% by volume at pressures up to 15 bar. During a measurement cycle, the air temperature was increased until autoignition occurred. The ignition process was observed by high-speed imaging of the flame chemiluminescence. In order to attribute a residence time (ignition delay time) to the locations where autoignition was detected the flow field and its turbulent fluctuations were simulated by numerical codes. These residence times were compared to calculated ignition delay times using detailed chemical simulations. The measurement system and data evaluation procedure are described and preliminary results are presented. An increase in pressure and in fraction of propane in the natural gas both reduced the ignition delay time. The measured ignition delay times were systematically longer than the predicted ones for temperatures above 950 K. The results are important for the design process of gas turbine combustors and the studies also demonstrate a procedure for the validation of design tools under relevant conditions.

High Pressure Ignition of Boron in Reduced Oxygen Atmospheres

1995 ◽  
Vol 418 ◽  
Author(s):  
R. O. Foelsche ◽  
M. J. Spalding ◽  
R. L. Burton ◽  
H. Krier
Keyword(s):  
High Pressure ◽  
Water Vapor ◽  
Shock Tube ◽  
Ignition Delay ◽  
Peak Pressure ◽  
Reflected Shock ◽  
Ignition Delay Times ◽  
Fluorine Compounds ◽  
Delay Times ◽  
Tube Study

AbstractBoron ignition delay times for 24 μm diameter particles have been measured behind the reflected shock at a shock tube endwall in reduced oxygen atmospheres and in a combustion bomb at higher pressures in the products of a hydrogen/oxygen/nitrogen reaction. The shock tube study independently varies temperature (1400 – 3200 K), pressure (8.5, 34 atm), and ignition-enhancer additives (water vapor, fluorine compounds). A combustion chamber is used at a peak pressure of 157 atm and temperature in excess of 2800 K to study ignition delays at higher pressures than are possible in the shock tube.

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