scholarly journals Aerosol Shock Tube Designed for Ignition Delay Time Measurements of Low-Vapor-Pressure Fuels and Auto-Ignition Flow-Field Visualization

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 683
Author(s):  
Erwei Liu ◽  
Qin Liao ◽  
Shengli Xu
Keyword(s):  
Flow Field ◽  
Vapor Pressure ◽  
Shock Tube ◽  
Ignition Delay ◽  
Pressure Sensors ◽  
Local Pressure ◽  
Ignition Delay Times ◽  
Auto Ignition ◽  
Delay Times ◽  
Sequential Images

An aerosol shock tube has been developed for measuring the ignition delay times (tig) of aerosol mixtures of low-vapor-pressure fuels and for visualization of the auto-ignition flow-field. The aerosol mixture was formed in a premixing tank through an atomizing nozzle. Condensation and adsorption of suspended droplets were not observed significantly in the premixing tank and test section. A particle size analyzer was used to measure the Sauter mean diameter (SMD) of the aerosol droplets. Three pressure sensors and a photomultiplier were used to detect local pressure and OH emission respectively. Intensified charge-coupled device cameras were used to capture sequential images of the auto-ignition flow-field. The results indicated that stable and uniform aerosol could be obtained by this kind of atomizing method and gas distribution system. The averaged SMD for droplets of toluene ranged from 2 to 5 μ m at pressures of 0.14–0.19 MPa of dilute gases. In the case of a stoichiometric mixture of toluene/O2/N2, ignition delay times ranged from 77 to 1330 μs at pressures of 0.1–0.3 MPa, temperatures of 1432–1716 K and equivalence ratios of 0.5–1.5. The logarithm of ignition delay times was approximately linearly correlated to 1000/T. In contrast to the reference data, ignition delay times of aerosol toluene/O2/N2 were generally larger. Sequential images of auto-ignition flow-field showed the features of flame from generation to propagation.

Ignition delay times of low-vapor-pressure fuels measured using an aerosol shock tube

2012 ◽  
Vol 159 (2) ◽  
pp. 552-561 ◽  
Author(s):  
Daniel R. Haylett ◽  
David F. Davidson ◽  
Ronald K. Hanson
Keyword(s):  
Vapor Pressure ◽  
Shock Tube ◽  
Ignition Delay ◽  
Ignition Delay Times ◽  
Delay Times

Shockless Explosion Combustion: Experimental Investigation of a New Approximate Constant Volume Combustion Process

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Thoralf G. Reichel ◽  
Jan-Simon Schäpel ◽  
Bernhard C. Bobusch ◽  
Rupert Klein ◽  
Rudibert King ◽  
...  
Keyword(s):  
Shock Waves ◽  
Ignition Delay ◽  
Gas Turbines ◽  
Control Algorithm ◽  
Pressure Sensors ◽  
Constant Volume ◽  
Ignition Delay Times ◽  
Auto Ignition ◽  
Delay Times ◽  
Constant Volume Combustion

Approximate constant volume combustion (aCVC) is a promising way to achieve a step change in the efficiency of gas turbines. This work investigates a recently proposed approach to implement aCVC in a gas turbine combustion system: shockless explosion combustion (SEC). The new concept overcomes several disadvantages such as sharp pressure transitions, entropy generation due to shock waves, and exergy losses due to kinetic energy which are associated with other aCVC approaches such as pulsed detonation combustion. The combustion is controlled via the fuel/air mixture distribution which is adjusted such that the entire fuel/air volume undergoes a spatially quasi-homogeneous auto-ignition. Accordingly, no shock waves occur and the losses associated with a detonation wave are not present in the proposed system. Instead, a smooth pressure rise is created due to the heat release of the homogeneous combustion. An atmospheric combustion test rig is designed to investigate the auto-ignition behavior of relevant fuels under intermittent operation, currently up to a frequency of 2 Hz. Application of OH*– and dynamic pressure sensors allows for a spatially and time-resolved detection of ignition delay times and locations. Dimethyl ether (DME) is used as fuel since it exhibits reliable auto-ignition already at 920 K mixture temperature and ambient pressure. First, a model-based control algorithm is used to demonstrate that the fuel valve can produce arbitrary fuel profiles in the combustion tube. Next, the control algorithm is used to achieve the desired fuel stratification, resulting in a significant reduction in spatial variance of the auto-ignition delay times. This proves that the control approach is a useful tool for increasing the homogeneity of the auto-ignition.

Ignition and Combustion of Heavy Hydrocarbons Using an Aerosol Shock-Tube Approach

2010 ◽  
Author(s):  
Brandon Rotavera ◽  
Nolan Polley ◽  
Eric L. Petersen ◽  
Kara Scheu ◽  
Mark Crofton ◽  
...  
Keyword(s):  
Shock Wave ◽  
Vapor Pressure ◽  
Shock Tube ◽  
Gas Phase ◽  
Ignition Delay ◽  
Two Phase ◽  
Heavy Hydrocarbons ◽  
Gaseous Oxidizer ◽  
Ignition Delay Times ◽  
Delay Times

Results from a heterogeneous shock-tube approach recently demonstrated at Texas A&M University, wherein a hydrocarbon fuel is introduced in liquid phase with gaseous oxidizer, are presented. The shock tube has been designed for controlled measurement of ignition delay times, sooting phenomena, radical species concentrations, time-dependent species profiles, and nanoparticle-aided combustion using heavy hydrocarbons which are difficult to study using the traditional shock tube approach. Aerosol is generated in a high-vacuum manifold positioned 4-m from the endwall where optical and pressure-based diagnostics are stationed. The approach reduces the propensity for fuel-film deposition near the endwall avoiding optical and/or kinetic disturbances that could result. The aerosol enters the shock tube initially as a two-phase flow of liquid fuel and gaseous oxidizer/inert gas. Liquid droplets partially evaporate while resident in the shock tube, prior to shock wave generation, and are then completely vaporized behind the incident shock wave. Behind the reflected shock wave, then, resides a pure gas-phase fuel and oxidizer mixture. The primary benefit of the aerosol shock tube approach is the ability to inject fuels of low vapor pressure at high or low concentrations. The classic shock-tube approach introduces gas-phase constituents only, and has difficulty accommodating low vapor-pressure liquids, except when component partial pressures are much lower than what is usually required. In the present work, n-heptane aerosol (C7H16, Pvap, 20 °C ∼ 35 torr), was generated with O2/Ar carrier gas and dispersed in the shock tube in a uniform manner. Stoichiometric ignition delay times with temperature varied from 1240 K to 1600 K and pressure maintained near 2.0 atm are compared to gas-phase data at similar conditions and a chemical kinetic model for heptane combustion. Excellent agreement was found between the two-phase aerosol approach and the classical method involving vapor-phase n-heptane and pre-mixed gases. The measured activation energy for the stoichiometric mixture at 2.0 atm (EA = 42.3 kcal /mol), obtained with the two-phase technique, compares well with the literature value.

Application of an aerosol shock tube to the measurement of diesel ignition delay times

2009 ◽  
Vol 32 (1) ◽  
pp. 477-484 ◽  
Author(s):  
D.R. Haylett ◽  
P.P. Lappas ◽  
D.F. Davidson ◽  
R.K. Hanson
Keyword(s):  
Shock Tube ◽  
Ignition Delay ◽  
Ignition Delay Times ◽  
Delay Times

scholarly journals Shock tube ignition delay times and methane time-histories measurements during excess CO2 diluted oxy-methane combustion

2016 ◽  
Vol 164 ◽  
pp. 152-163 ◽  
Author(s):  
Batikan Koroglu ◽  
Owen M. Pryor ◽  
Joseph Lopez ◽  
Leigh Nash ◽  
Subith S. Vasu
Keyword(s):  
Shock Tube ◽  
Ignition Delay ◽  
Methane Combustion ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Time Histories

Comparison Between RCCE and Shock Tube Ignition Delay Times at Low Temperatures

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Ghassan Nicolas ◽  
Hameed Metghalchi
Keyword(s):  
Free Energy ◽  
Shock Tube ◽  
Ignition Delay ◽  
Low Temperatures ◽  
Reduction Technique ◽  
Experimental Measurements ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Constrained Equilibrium ◽  
Rate Controlled

The rate-controlled constrained-equilibrium (RCCE) method is a reduction technique based on local maximization of entropy or minimization of a relevant free energy at any time during the nonequilibrium evolution of the system subject to a set of kinetic constraints. In this paper, RCCE has been used to predict ignition delay times of low temperatures methane/air mixtures in shock tube. A new thermodynamic model along with RCCE kinetics has been developed to model thermodynamic states of the mixture in the shock tube. Results are in excellent agreement with experimental measurements.

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

scholarly journals Numerical investigations on hydrogen-enhanced combustion in ultra-lean gasoline spark-ignition engines

2019 ◽  
pp. 146808741987068 ◽  
Author(s):  
Nicolas Iafrate ◽  
Mickael Matrat ◽  
Jean-Marc Zaccardi
Keyword(s):  
Ignition Delay ◽  
Combustion Process ◽  
Spark Ignition ◽  
Combustion Stability ◽  
Spark Ignition Engines ◽  
Numerical Investigations ◽  
Ignition Delay Times ◽  
Auto Ignition ◽  
Delay Times ◽  
Combustion Speed

Performance of lean-burn gasoline spark-ignition engines can be enhanced through hydrogen supplementation. Thanks to its physicochemical properties, hydrogen supports the flame propagation and extends the dilution limits with improved combustion stability. These interesting features usually result in decreased emissions and improved efficiencies. This article aims at demonstrating how hydrogen can support the combustion process with a modern combustion system optimized for high dilution resistance and efficiency. To achieve this, chemical kinetics calculations are first performed in order to quantify the impacts of hydrogen addition on the laminar flame speed and on the auto-ignition delay times of air/gasoline mixtures. These data are then implemented in the extended coherent flame model and tabulated kinetics of ignition combustion models in a specifically updated version of the CONVERGE code. Three-dimensional computational fluid dynamics engine calculations are performed at λ = 2 with 3% v/v of hydrogen for two operating points. At low load, numerical investigations show that hydrogen enhances the maximal combustion speed and the flame growth just after the spark which is a critical aspect of combustion with diluted mixtures. The flame front propagation is also more isotropic when supported with hydrogen. At mid load, hydrogen improves the combustion speed and also extends the auto-ignition delay times resulting in a better knocking resistance. A maximal indicated efficiency of 48.5% can thus be reached at λ = 2 thanks to an optimal combustion timing.

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