A Double-Diaphragm Shock Tube for Hydrocarbon Disintegration Studies (original) (raw)

Design of a double diaphragm shock tube for fluid disintegration studies

Review of Scientific Instruments, 2008

A double diaphragm shock tube facility for studying liquid-spray atomization and combustion-related phenomena at elevated pressures and temperatures is described. The present shock tube is specifically intended for the investigation of fundamental processes related to fluid disintegration and mixing under realistic engine conditions. Special features of the facility include a variable-area driver section to compensate for shock attenuation, a square test section to allow flow visualization in the postshock region, a skimmer to dispose part of the boundary layer, a heated, fast-response injector, a fully automated gas-filling system, and a new control system and electronics. Test times of the order of 2-5 ms are possible with reflected shock pressures up to 50 bar and temperatures of 2000 K. Details on the setup design, construction and operation are given. Particular emphasis is placed on the accuracy and reproducibility of the test conditions. To that aim, qualification tests have been performed to assess the shock tube performance in terms of effectiveness of the skimmer concept, the capability to compensate for boundary layer effects and the generation of uniform and reproducible test and injection conditions.

Development of an aerosol shock tube for kinetic studies of low-vapor-pressure fuels

Combustion and Flame, 2008

A new experimental flow facility, an aerosol shock tube, has been developed to enable studies of shock wave interactions with liquid aerosols, including droplet evaporation kinetics and subsequent chemical reaction of the vapor. This technique provides a uniform spatial distribution of aerosol in the shock tube, which ensures wellbehaved shock-induced flows, and a narrow micrometer-sized aerosol size distribution that rapidly evaporates. These two features enable quantitative shock tube investigation of the chemistry of high-concentration vapor mixtures of low-vapor-pressure practical fuels and fuel surrogates. In the present experiments, the incident shock wave is used to vaporize the fuel droplets, and the reflected shock wave is used to induce ignition. We report here the first aerosol shock tube ignition delay time measurements of n-dodecane/O 2 /argon and JP-7/O 2 /argon mixtures. The measurements are found to be consistent with those made in our heated shock tube facility.

A high-pressure shock tube characterization and auto-ignition delay investigations

A high pressure shock tube "HPST" has been designed for the purpose of chemical kinetics studies at elevated pressures and temperatures. The present HPST is designed as a versatile tool and includes the features of a fast compression, optical accessibility, and capability for specie measurement. Characterization experiments establish the suitability of the tube for chemical kinetic studies and show that highly repeatable experimental conditions up to 40 bar and temperatures between 1300 and 2000 K can be obtained. As well, tailoring gas mixture in the driver section, used to obtain a longer test time, is studied in the characterization experiments. Using this facility, autoignition investigations are conducted for methane mixture (1% CH 4 ; 4% O 2 ; 95% Ar ; f=0,5) at 10, 20 and 40 bar pressures and temperatures from 1300 K up to 2000 K.

Fluid disintegration studies in a specialized shock tube

Progress in Propulsion Physics, 2011

This paper describes a double-diaphragm shock tube, designed for the experimental investigation of fundamental processes related to §uid disintegration and mixing at elevated pressures and temperatures, representative for realistic engine conditions. Special features of the shock tube include a variable-area driver section to compensate for shock attenuation and boundary layer e¨ects. In discussing the shock tube operational envelope, particular emphasis is given to the requirements to be ful¦lled to attain reproducible and accurate experimental data and to capture the most relevant features of subcritical and supercritical mixing behavior. A review of potential thermodynamic transitions for near-critical jet disintegration phenomena is presented and the main features of each disintegration mode are discussed on the basis of the shock tube experiments.

Shock Tube Study on Hydrocarbon Free Jets using High-Speed Shadowgraphy

15th AIAA International Space Planes and Hypersonic Systems and Technologies Conference, 2008

H igh-speed shadowgraphy was applied to visualise hydrocarbon spray atomisation at elevated pressures and temperatures. The experiments were performed in the quiescent post-shock region of a double-diaphragm shock tube facility. The latter was recently upgraded with a variable-area driver section to compensate for shock attenuation and is equipped with a heated, fast-response injection system. Test times were in the order of 4.5 ms with reflected-shock pressures ranging from 10-35 bar and test temperatures of 950 K. The fuel (n-dodecane) was injected right after shock reflection. After a transient start-up process, quasi-steady injection was achieved and sustained for about 2.5 ms. Fuel temperatures were varied between 373.15 and 523.15 K. The images attained at 100,000 fps were analysed with respect to the spatial and temporal dispersion of the spray. The influence of the chamber pressure and the fuel temperature on the spray break-up process was investigated. Increasing chamber pressures (chamber densities) and fuel temperatures result in an enhancement of the spray dispersion measured in terms of jet angles and therefore in a better mixing and vaporisation.

Shock Tube Study of Methylcyclohexane Ignition over a Wide Range of Pressure and Temperature

Energy & Fuels, 2009

Ignition delay times were measured for gas-phase methylcyclohexane (MCH)/O 2 /argon and MCH/air mixtures behind reflected shock waves. Initial postshock conditions covered temperatures of 795-1560 K, pressures of 1-50 atm, fuel concentrations of 0.25-2%, and equivalence ratios (φ) of 0.5-2.0. Ignition delay times were measured using side-wall pressure and CH* and OH* emission measurements. Current measurements complement past high-pressure rapid compression machine results, are in good agreement with past lowpressure shock tube data, and significantly extend the pressure range of available shock tube ignition time data. Detailed comparisons of experimental data with predictions of available MCH mechanisms are presented, and comparisons of shock tube MCH ignition delay times to those of other important jet fuel surrogates and cyclo-alkanes are discussed.

Shock Tube Combustion Analysis

Internal Combustion Engine Technology and Applications of Biodiesel Fuel, 2021

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 compress...

Ilass 08-A 068 High-Speed Visualisation of Liquid Jet Disintegration

2008

High-speed shadowgraphy was applied to visualise hydrocarbon spray atomisation at elevated pressures and temperatures. The experiments were performed in the quiescent post-shock region of a doublediaphragm shock tube facility using a heated, fast-response injection system. Test times were in the order of 4.5 ms with reflected-shock pressures ranging from 10-35 bar and test temperatures of 950 K. The fuel (n-hexane and n-dodecane) was injected right after shock reflection and quasi-steady injection was achieved and sustained for about 2.5 ms. Fuel temperature covered both suband supercritical values as it was varied between 373.15 and 523.15 K. The acquired images were analysed with respect to the spatiotemporal evolution of the spray, specifically spreading angles and penetration lengths were derived. The influence of the chamber pressure and the fuel temperature on the spray break-up process was investigated. Increasing chamber pressures (chamber densities) and fuel temperatures re...

Detonation driver for enhancing shock tube performance

Shock Waves, 2003

The development of a shock-induced detonation driver for enhancing the performance of a shock tube is described. The detonation wave is induced by the expansion of helium or air. Various gaseous fuel-oxidizer combinations are examined. This method produces a detonation wave which propagates downstream that transitions into a shock wave in the driven section. High-enthalpy flows with a maximum total temperature of 4200 K and a maximum total pressure of 34 atm in the driven tube are achieved. The problems of achieving the so-called perfectly-driven mode as well as those of inadequate fuel-oxidizer mixing are discussed.