Piezoelectric Pressure Transducers Research Articles

Experimental Evaluation of the Methane Number Measurement Procedure for Gaseous Fuel Rating

Methane Number (MN) is a fuel rating technique for gaseous fuels analogous to Octane Number. This study establishes and shares a repeatable and reproducible method for MN determination of a gaseous fuel using a modified Cooperative Fuel Research Engine (CFR). Adaptations required to convert a CFR engine for use in the MN test procedure are identified. The investigation includes allowable environmental parameters and operating variation limits. An essential aspect of the MN method involves identifying and quantifying Knock Intensity (KI) during engine operation. CFR engines, originally designed for gasoline testing, come equipped with their own knock measurement systems utilizing a capacitive detonation sensor. The original system is compared with a Fast Fourier Transform (FFT) approach that uses a piezoelectric pressure transducer. Quantification of methane number requires an accurate assessment of the reference fuel blend (CH4 + H2). A comparison is carried out between dynamic blending using mass flow meters and bracketing using certified gas bottles containing various CH4/H2 blends from a gas supplier.

Blast wave pressure measurement and analysis in air and granular media inside a shock tube using a fiber Bragg grating sensor.

In this work, we have demonstrated the use of a fiber Bragg grating (FBG) sensor to measure the pressure profile of blast waves generated inside a vertical shock tube (VST). An FBG pressure sensor probe has been designed and developed that can be incorporated into the wall of the VST. The VST facility is used to generate blast waves with decay times of the order of a few milliseconds to simulate explosive events. Pressure measurement experiments have been carried out at different incident blast wave peak pressures inside the VST. The FBG pressure sensor measurements are validated against a standard piezoelectric pressure transducer at an acquisition rate of 1MHz. The pressure signals of both sensors are found to match well with similar rise times and decay profiles. The validated FBG pressure sensor is then incorporated into a sand column mounted in the test section of the VST to measure the pressure profile of blast wave-induced stress waves in granular media. The FBG and piezoelectric pressure sensor data are compared using fast Fourier transform analysis and continuous wavelet transform. The feasibility of FBG sensors for blast pressure measurement under harsh conditions imposed inside shock tube environments is established.

Experimental investigation for the effect of bust pressure on hydrogen explosion venting

A series of experiments are carried out to investigate the effect of burst pressure on hydrogen explosion venting in a 20 L square vessel. Pressure buildup and flame evolution are recorded using piezoelectric pressure transducers, high speed camera, high speed infrared camera and schlieren system. The results show that both the maximum explosion pressure (Pmax) inside and outside the vessel increase with the increasing burst pressure, and the Pmax in the external space decreases rapidly with the increase of the distance from the vent port. Compared to the burst pressure of 0 kPa, the Pmax inside the vessel and at 1200 mm increased by 79.1 % and 153.6 %, respectively, when the burst pressure was 325 kPa. The venting flame surface during the propagation is smoother with the increasing burst pressure, the width and area of the flame also increases. There is little effect of burst pressure on the maximum flame propagation distance (Lmax), but with the increase of burst pressure, the flame propagation time is shortened and the average propagation velocity is increased. The venting flame propagation time is shortened from 5.0 ms to 3.5 ms with the burst pressure increases from 0 kPa to 325 kPa. The high temperature zone of venting flame is mainly distributed in the flame front, while the maximum flame temperature (Tmax) gradually increases with the increase of burst pressure. The increase in burst pressure results in an increase in the turbulence intensity inside the vessel and an advance in the time to stabilization inside the vessel. Furthermore, the moment at which flow backflow occurs at the vent port is advanced from 16.5 ms to 8.5 ms with the increase in burst pressure.

Combustion performance and flame front morphology of producer gas from a biomass gasification-based cookstove

The present work investigates the last phase of the biomass gasification-based cookstove, which is the combustion process of biomass producer gas (BGP). A constant volume combustion bomb and kinetic simulation are used to characterize the behavior of the biomass producer gas and its pollutant emissions under a conventional premixed combustion process. The BGP combustion processes of two types of biomasses available in Colombia (Pinus Patula and Cordia Alliodora) are studied under certain conditions of pressure, temperature, and equivalence ratio. To characterize the combustible mixture of gases obtained after biomass gasification, a combustion chamber with cylindrical geometry equipped with a Schlieren optical diagnostic system to visualize the combustion process, and a piezoelectric pressure transducer to register the instantaneous pressure are used. By visualizing the flame front, the flame propagation speed at which the flame propagates through the combustion chamber and the morphology of the flame are studied. Instantaneous pressure is the input of a two-zone diagnostic model through which variables, such as burning velocity, temperature, mass burned fraction, etc., are obtained to characterize the combustion process of the mentioned gasification gases. Experimental results are compared and complemented with kinetic modeling results obtained with the Cantera package using the Gri-Mech 3.0 and Aramko 1.3 kinetic mechanisms, in terms of laminar burning velocity and NO, NO2, CO, and CO2 exhaust emissions. Results show that Cordia Alliodora presents higher burning velocities than Pinus Patula BP. However, lower CO2 emissions are obtained during the Cordia Alliodora combustion, and NOx emissions are not influenced by the type of biomass considered.

Experimental investigation on shock wave propagation and spontaneous ignition of high-pressure hydrogen release through a sho (ϸ)-shaped extension tube into the atmosphere

The geometry of the extension tube has a great influence on the shock wave propagation and spontaneous ignition of high-pressure hydrogen release in this paper, piezoelectric pressure transducers, photodiodes and a high-speed camera are used to study the shock wave propagation and spontaneous ignition of high-pressure hydrogen released to the downstream sho (ϸ)-shaped extension tube. Experimental results show that the intensity of the leading shock wave is weakened due to the presence of branches when it propagates in the straight section of the sho-shaped tube, and a strong reflected shock wave is generated in the bend section. Spontaneous ignition is more prone to occur in the bend section than in the straight section, with a large optical signal value and long flame duration. However, due to the complex structure of the extension tube, there are still cases of the hydrogen flame extinguishing inside the tube even under high burst pressure. The flame detection time after the leading shock wave at the measured positions decreases with increasing burst pressure, and the time in the bend section is greater than that of the straight section. Radial flame expansion, flame separation, downstream flame extinction and upstream flame development, primary jet fire and secondary jet fire are successively observed outside the tube.

Düşey Milli Eksenel Bir Pompada Zamana Bağlı Akışın Deneysel Olarak İncelenmesi

Due to the changes in the system characteristics, pumps may have to be operated far away from the design point, such as in part-load or over-load operating points. Operating the pumps far away from the design point may cause fluctuations in the flow. As a result of the fluctuations mechanical problems in the pump structure may occur. In order to overcome the problem, the operating characteristics of the pump must be determined at part load operating conditions as well as design point operating condition. In this study, flow inside a vertical shaft axial flow pump is investigated experimentally. The experimental setup is designed and constructed for the laboratory tests. The pump which is designed and manufactured is tested in the test setup. The performance of the pump is determined by measuring the flow rate, inlet and outlet pressures, rotational speed and power input of the pump. The part load and over load operating regions are determined. Pressure variations are measured at various performance points with the piezoelectric pressure transducer placed in between impeller and diffuser blade passage. Simultaneously, comparisons are made with the vibration spectrums obtained in the pump.

Investigation of In-Cylinder Pressure Measurement Methods within a Two-Stroke Spark Ignition Engine

<div>This work describes an investigation of measurement techniques for the indicated mean effective pressure (IMEP) on a 55 cc single-cylinder, 4.4 kW, two-stroke, spark ignition (SI) engine intended for use on Group 1 and Group 2 remotely piloted aircraft (RPAs). Three different sensors were used: two piezoelectric pressure transducers (one flush mount and one measuring spark plug) for measuring in-cylinder pressure and one capacitive sensor for determining the top dead center (TDC) position of the piston. The effort consisted of three objectives: to investigate the merits of a flush mount pressure transducer compared to a pressure transducer integrated into the spark plug, to perform a parametric analysis to characterize the effect of the variability in the engine test bench controls on the IMEP, and to determine the thermodynamic loss angle for the engine. The results indicate that as a spark plug, the measuring spark plug is not statistically different from the stock spark plug at the 95% confidence level. The results indicate a statistically significant, 4% difference in the measured IMEP between the pressure transducer in the measuring spark plug and the flush mount transducer. The results also suggest a statistically significant difference in performance between the modified and unmodified engine heads, verifying the suppositions of other researchers who suggested that even a small modification to a combustion chamber this size could measurably affect the engine performance. While run-to-run variation resulted in a 2% to 5% variation in IMEP, a sensitivity analysis determined that 1% to 3% of that variation arose from variability in the control variables, while the remainder was caused by variation in other engine operating parameters. Between 1000 rpm and 2000 rpm, where the engine was typically motored to determine the TDC, the thermodynamic loss angle was 0.3 crank angle degrees (CAD) to 0.7 CAD, larger than loss angles observed in automotive-sized gasoline engines. The results indicate that using tabulated thermodynamic loss angles to set the TDC location of the engine using a mono-directional peak pressure method would lead to a −1% to −2.5% bias in the IMEP.</div>

Optical pressure sensing at MHz rates via collisional line broadening of carbon monoxide: uncertainty quantification in reacting flows

An optical method for high-speed line-of-sight pressure measurements using infrared laser absorption spectroscopy is presented with detailed uncertainty analysis related to thermodynamic and compositional variation in combustion environments. The technique exploits simultaneous sub-microsecond sensing of temperature and mole fraction to extract pressure from collisional line broadening at MHz rates. A distributed-feedback quantum-cascade laser near 5 upmu m in a bias-tee circuit is used to spectrally resolve multiple rovibrational transitions in the P-branch of the fundamental band of carbon monoxide, which may be seeded or nascent to reacting flows. A comprehensive approach for estimating collisional line broadening in complex combustion gas mixtures is presented. Uncertainty is quantified for a wide range of conditions, reflecting different fuels, equivalence ratios, reaction progress, and combustion modes (deflagration and detonation), which influence gas composition and temperature. The sensor was evaluated for accuracy and precision in both a high-enthalpy shock-tube facility in hydrocarbon–air ignition experiments and behind ethylene–oxygen detonation waves in a detonation-impulse tube facility at temperatures from 1500 to 3000 K and pressures from 0.5 to 10 bar. Pressure measurements were compared to measurements by piezoelectric pressure transducers and to theoretical estimates from normal-shock and Chapman-Jouguet simulations. The high-speed path-integrated optical pressure measurement offers an alternative to traditional electromechanical transducers that are constrained to values at wall boundaries and have proven unreliable in some harsh reacting flows.

Experimental characterisation and data-driven modelling of unsteady wall pressure fields induced by a supersonic jet over a tangential flat plate

This work deals with the investigation and modelling of wall pressure fluctuations induced by a supersonic jet over a tangential flat plate. The analysis is performed at several nozzle pressure ratios around the nozzle design Mach number, including slightly over-expanded and under-expanded conditions, and for different radial positions of the rigid plate. Pitot measurements and flow visualizations through the background oriented schlieren technique provided a general overview of the aerodynamic interactions between the jet flow and the plate at the different regimes and configurations. Wall pressure fluctuations were measured using a couple of piezoelectric pressure transducers flush mounted over the plate surface. The spectral analysis has been carried out to clarify the effect of the plate position on the single and multivariate wall pressure statistics, including the screech tone amplitude. The experimental dataset is used to assess and validate a surrogate model based on artificial neural networks. Sound pressure levels and coherence functions are modelled by means of a single fully connected network, built on the basis of a recently implemented fully deterministic topology optimization algorithm. The metamodel uncertainty is also quantified using the spatial correlation function. It is shown that the flow behaviour as well as the screech and broadband noise signatures are significantly influenced by the presence of the plate, and the effects on spectral quantities are correctly reproduced by the proposed data-driven model that provides predictions in agreement with the available data.

MEASUREMENT OF THE REGRESSION RATE IN A HYBRID ROCKET MOTOR BY ACQUIRING THE HELMHOLTZ FREQUENCY IN THE COMBUSTION CHAMBER

Low thrust values obtained with a hybrid rocket motor (HRM) are a consequence of the difficulty in quickly mixing the fuel and oxidizer, which is characterized by a low regression rate of the fuel grain. Therefore, the measurement of this parameter is of great importance in studies that aim at solutions for this deficiency in HRM. Several studies calculate a reliable value of the average regression rate over time by measuring the total mass of fuel before and after each burn. A method to measure instantaneous regression rate is by acquiring the Helmholtz resonance frequency in the combustion chamber. This work uses a piezoelectric pressure transducer to obtain the Helmholtz frequency mode of the combustion chamber in a laboratory scale test bench with high-density polyethylene (HDPE) and gaseous oxygen, and is based on the principle that this frequency is inversely proportional to the square-root of the chamber volume. With the chamber volume variation, the port diameter of the grain variation is obtained. In conclusion, the calculated variation of port diameter agreed well with the correlation for average regression rate, determined from mass loss during operation.

Spatiotemporal analysis of sheet and cloud cavitation and its damage potential

The cavitation regime has a substantial influence on the damage potential, thus it has to be considered in any specific investigation. For this purpose, we set up a test rig at the Technische Universität Darmstadt using a Circular Leading Edge hydrofoil (CLE) to analyse the damage potential of sheet and cloud cavitation. Exceeding a critical Reynolds number Re c, the cavitation regime transitions from harmless sheet cavitation to aggressive cloud cavitation. High-speed recordings of the cavitation regime are correlated with high frequency pressure data from a wall-mounted piezoelectric pressure transducer. Spatial and temporal content of the cavitating flow are captured applying proper orthogonal decomposition (POD) to the high-speed recordings. In order to determine the damage potential of the cavitation regime we apply a copper foil on the hydrofoil surface, on which plastic, crater-shaped deformations due to bubble collapses occur. Images of the surface are recorded before and after each run via two-dimensional Pit-Count microscopy. We correlate spatial modes from the cavitating flow field with the eroded surface rate from pitting tests leading to the result that cloud cavitation associated with increasing cloud size is more aggressive. A power law is identified where pitting rate increases with fourteenth power of the Reynolds number.

Investigation of bifurcations in cyclic combustion dynamics of a CNG-diesel RCCI engine

This study uses nonlinear dynamical and chaotic methods to investigate the cyclic combustion dynamics of a CNG-Diesel reactivity control compression ignition (RCCI) engine. The experiments of RCCI combustion mode are conducted on a single-cylinder automotive diesel engine with the development ECU. Low reactivity fuel (i.e., CNG) is injected into the intake manifold, and high reactivity fuel (i.e., diesel) is injected directly into the engine cylinder during the RCCI experiments. Mass of fuel injection per cycle and their injection events are controlled by using ECU. The engine is tested for fixed engine load and speed of 3 bar BMEP and 1500 rpm, respectively. A double diesel injection strategy is used for injecting the diesel fuel into the engine cylinder. In-cylinder pressure is measured using a piezoelectric pressure transducer on a crank angle basis with a resolution of 0.1 CAD. Combustion parameters are calculated on a cyclic basis from measured in-cylinder pressure. In this study, the effect of diesel injection timing (SOI-2) on the behavior of combustion dynamics for two different masses of port-injected CNG fuel (mc) is investigated. The CA50 time series of 1000 consecutive engine cycles is analyzed for combustion dynamics analysis using symbol sequence analysis, return maps, recurrence plots (RPs), recurrence quantitative analysis (RQA), and 0–1 test. The peaks in symbol sequence histograms and the corresponding symbol series depict the period-2 nature of the cyclic combustion dynamics at the intermediate SOI-2 of 30° and 40° bTDC. Return maps also confirm the onset of noisy period-2 bifurcation at 30° bTDC SOI-2. The dominance of deterministic period-2 characteristics is found in the cyclic combustion dynamics at 30° and 40° bTDC SOI-2 using recurrence plots. The 0–1 test method depicts stronger chaotic cyclic combustion dynamics at 20° and 50° bTDC SOI-2. In summary, the present study supports the existence of a periodic window in between the chaotic combustion for the intermediate values of SOI-2. The dominance of the deterministic characteristics makes this regime of intermediate SOI-2 values suitable for a better cycle resolved control.

Hydrogen-air explosion with concentration gradients in a cubic enclosure

An inhomogeneous hydrogen-air mixture is induced once hydrogen leakage occurs, and an explosion may be triggered due to an accidental ignition with sufficient strength. The effects of different hydrogen concentration gradients on flame behavior and overpressure were experimentally investigated in a closed cubic vessel with a volume of 0.125 m3. The transverse concentration gradients of hydrogen injected from the top face of the vessel were recorded using five oxygen sensors. A high-speed photography was employed to capture the flame shape evolution and the flame tip velocity was derived. Three piezoelectric pressure transducers were mounted on the top and side walls to measure the pressure-time profiles. The results show that the maximum overpressure in homogeneous mixtures is larger than that in inhomogeneous mixtures for fuel-lean hydrogen-air mixtures. However, the maximum overpressure in inhomogeneous mixtures is equal to or larger than that in homogeneous mixtures for fuel-rich hydrogen-air mixtures. Due to a larger difference between the upward and downward flame speeds, a mushroom-like shape flame was recorded in inhomogeneous hydrogen-air mixtures in fuel-lean to slightly fuel-rich hydrogen-air mixtures. The flame speed in two directions has the almost same value in inhomogeneous fuel-richer mixtures. The average flame speed in inhomogeneous mixtures is significantly larger than that in homogeneous mixtures for fuel-rich hydrogen air mixtures.

A Method for Estimation of Blast Performance of RDX‐IPN‐Al Annular Thermobaric Charges

AbstractThe objective of this research was to develop and to experimentally validate a method to predict the blast performance of thermobaric annular charges based on isopropyl nitrate‐aluminium and RDX‐isopropyl nitrate‐aluminium. Overpressure and thermal output were investigated in open air using piezoelectric pressure transducers, high speed visible and infrared imaging. Prediction of the explosive transformation of the annular thermobaric charge was computed by thermochemical code EXPLO5® using the Chapman‐Jouguet (ideal detonation) and non‐ideal Wood and Kirkwood (WK) detonation model. The Jones‐Wilkins‐Lee (JWL) parameters obtained in the calculations were used in hydrocode numerical simulation using AUTODYN® in order to predict the incident overpressure, total impulse and arrival time. Additional energy attributed to aluminium afterburning was used in order to simulate the post‐combustion phase. For isopropyl nitrate‐aluminium based charges, both BKW and WK models estimate correctly the peak overpressure and arrival time, while the total impulse was more accurately calculated by WK non‐ideal detonation model. For the RDX‐containing formulation, the prediction of peak overpressure, total impulse and arrival time are in agreement with the predictions obtained using WK non‐ideal detonation model with additional energy. The performances of the investigated thermobaric charges were compared with an equivalent mass charge of TNT, confirming both the expected higher total impulse and higher peak overpressures in the case of RDX‐isopropyl nitrate‐aluminium based thermobaric charges. Thermal measurements highlighted two distinct phases, an anaerobic phase and the post combustion of the thermobaric compositions. In terms of thermal output, the RDX‐isopropyl nitrate‐aluminium thermobaric based charge manifests superior performances.

Investigation into the Relationship between Super-Knock and Misfires in an SI GDI Engine

The super-knock poses new challenges for further increasing the power density of spark ignition (SI) engines. The critical factors and mechanism connecting regarding the occurrence of super-knock are still unclear. Misfire is a common phenomenon in SI engines that the mixture in cylinder is not ignited normally, which is often caused by spark plug failure. However, the effect of misfire on engine combustion has not been paid enough attention to, particularly regarding connection to super-knock. The paper presents the results of experimental investigation into the relationship between super-knock and misfires at low speed and full load conditions. In this work, a boosted gasoline direct injection (GDI) engine with an exhaust manifold integrated in the cylinder head was employed. Four piezoelectric pressure transducers were used to acquire the data of a pressure trace in cylinder. The spark plugs of four cylinders were controlled manually, of which the ignition system could be cut off as demanded. In particular, a piezoelectric pressure transducer was installed at the exhaust pipe before the turbocharger to capture the pressure traces in the exhaust pipe. The results illustrated that misfires in one cylinder would cause super-knock in the other cylinders as well as the cylinder of itself. After one cylinder misfired, the unburned mixture would burn in the exhaust pipe to produce oscillating waves. The abnormal pressure fluctuation in the exhaust pipe was strongly correlated with the occurrence of super-knock. The sharper the pressure fluctuation, the greater the intensity of knock in the power cylinder. The cylinder whose exhaust valve overlapped with the exhaust valve of the misfired cylinder was prone to super-knock.

Mitigation of Pressure Fluctuations From an Array of Pulse Detonation Combustors

Abstract An annular plenum is integrated downstream of six pulse detonation combustors arranged in a canannular configuration. The primary purpose of the plenum is the mitigation of pressure and velocity fluctuations, which is crucial for operation with a downstream turbine. The flow inside the plenum is investigated by means of flush-mounted pressure transducers arranged in the axial and circumferential directions. The test rig is operated in different firing patterns at 16.7 Hz per tube. Two firing patterns are studied to characterize the shock dynamics inside the plenum. The obtained data allows for a better understanding of shock interaction and attenuation inside the plenum, as well as the quantification of pressure fluctuations at the plenum outlet. Furthermore, a comparison is made between piezoresistive and piezoelectric pressure transducers, showing the capability of piezoresistive transducers for dynamic pressure measurements. The performance of the piezoresistive transducers allows for time-resolved measurement of both static and total pressure at the exit of the plenum. Moreover, the plenum results in a significant attenuation of the leading shock wave while redistributing its energy both spatially and temporally.

Mechano‐Optical Characterization of Extrusion Flow Instabilities in Styrene‐Butadiene Rubbers: Investigating the Influence of Molecular Properties and Die Geometry

AbstractThe extrusion flow instabilities of two commercial styrene‐butadiene rubbers are investigated as they vary in isomer content (1,4‐cis, 1,4‐trans, and 1,2 conformation) of the butadiene monomer and the molecular architecture (linear, branched). The investigated samples have similar multimodal molecular weight distribution. Two geometries of extrusion dies, slit and round capillary, are compared in terms of the type and the spatial characteristics of the flow instabilities. The latter are quantified using three methods: a highly pressure sensitive slit die, online and offline optical analysis. The highly pressure‐sensitive slit die has three piezoelectric pressure transducers (Δt ≈ 10−3 s and Δp ≈ 10−5 bar) placed along the die length. The characteristic frequency (fChar.) of the flow instabilities follows a power law behavior as a function of shear rate to a 0.5 power for both materials, . A qualitative model is used to predict the spatial characteristic wavelength (λ) of the flow instabilities from round capillary to slit dies and vice versa. Slip velocities (Vs) are used to quantify the slippage at slit and round capillary dies as well.

Experimental investigation of the effect of temperature on ignition of modified kerosene

Kerosene based hydrocarbon fuels are preferred candidates for the source of energy due to its stable properties. Based on the requirement of the combustor and the growing concern over pollutant, kerosene based fuels are modified. The fuel under investigation is a modified form of kerosene with ultra-low sulphur content. The effect of temperature on modified kerosene is studied for viscosity, surface tension, specific heat, density and ignition delay. The time delay for ignition of gas-phase mixtures of modified kerosene/oxygen have been measured using a shock tube facility. The experiments are conducted in the temperature range of 1200–1877 K, pressure range of 4–12 atm and equivalence ratio of Ø = 1.5, 1 and 0.5. The ignition delay time measurements were carried out using piezoelectric pressure transducers, which records the pressure rise due to ignition and simultaneously recording the light emission during the process of ignition using a photodiode. The ignition delay is represented as τign = 0.168841 × P−1.49 × Ø0.72 × e(14310/T)

An experimental study of detonation propagation and re-initiation for acetylene–air mixtures in a narrow channel

Detonation propagation, re-initiation, and flame propagation in acetylene–air mixtures were investigated in a channel with a transverse dimension that is comparable with the width of the detonation cell. Experiments were carried out in a channel with a square cross-section of 5 mm $$\times $$ 5 mm. The detonation wave passed from the driver section into the transparent test section. The trajectories of the propagation of glowing combustion products (high-speed image sequences) were recorded, and high-speed schlieren image sequences of the reaction zone and shock waves were obtained. The flame front velocity was measured. The intensity of the shock waves was measured with piezoelectric pressure transducers. Depending on the equivalence ratio ER, four modes of combustion propagation were detected: (1) steady detonation; (2) decay and re-initiation of detonation; (3) detonation decay and flame acceleration; and (4) detonation decay and the absence of flame acceleration. Quantitative evaluation of the boundary layer thickness was carried out. The intensity of the shock wave and the flame front velocity were analysed for different modes. It was shown that the re-initiation of detonation in a mixture of acetylene and air with $$\text {ER} = 1.6$$ is characterized by a spatial interval of $$1000\pm 50$$ mm and a time interval of $$1300\pm 100~\upmu \hbox {s}$$ .

The Influence of Ethylene Gas Concentration on LDPE/C2H4 Hybrid Explosion Process and its Severity

The influence of ethylene (C2H4) gas concentration on the LDPE dust hybrid explosion in a 20-L spherical vessel, equipped with a chemical ignitor was analysed for the determination of maximum explosion overpressure, Pmax and deflagration index, KG. The LDPEC2H4 dust hybrid explosibility was evaluated based on the Pmax development, measured by the Kistler piezoelectric pressure transducer. The adiabatic flame temperature was calculated based on ideal gas law. It is speculated that the LDPE/C2H4 explosion undergoes three-phase process, starting with the ignition, followed by flame growth and flame regression. The highest Pmax (17.9 bar) and flame temperature (5200 K) was obtained at flame growth phase, recorded at C2H4 concentration of 3 vol/vol%. It was found that the Pmax and flame temperature is dependent on C2H4 concentration. The calculated KG values in a range of 14 – 60 bar.m/ms obtained in this study, suggesting that the LDPE/C2H4 dust hybrid explosion might subject to an extreme explosion characteristic.