Experiments on duct-vented explosion of hydrogen–methane–air mixtures: Effects of equivalence ratio

Kajian tentang letupan gas/udara di dalam tangki silinder dengan panjang/garis pusat adalah 2, dilaporkan di mana tangki silinder bersambung dengan paip dengan panjang/garis pusat ialah 6. Kajian ke atas kesan tekanan koyakan penutup ventilasi dan kedudukan pencucuh dijalankan untuk mengetahui nilai tekanan maksimum di dalam tangki, halaju nyalaan gas serta halaju gas tak terbakar. Gas propana dan metana di dalam udara digunakan dalam kajian ini dengan kadar persamaan gas/udara antara 0.8 hingga 1.6. Keputusan kajian menunjukkan bahawa tekanan dan halaju nyalaan udara di dalam tangki silinder adalah lebih tinggi jika kedudukan pencucuh berada jauh dari ventilasi berbanding jika pencucuh berada pada bahagian tengah tangki. Selain itu, sebelum gas dialirkan keluar ke bahagian paip, aliran gas dihalang untuk memasuki bahagian paip disebabkan oleh aliran sonik yang terbentuk pada bukaan paip. Kata kunci: Letupan gas; tekanan koyakan penutup ventilasi; kedudukan pencucuh; aliran sonik A study of vented explosions in length/diameter (L/D) of 2 of cylindrical vessel with a duct pipe (L/D = 6) is reported. The influence of vent burst pressure and ignition locations on maximum overpressure generated inside the vessel, flame speeds and unburnt gas velocities ahead of the flame were systematically investigated. Propane and methane–air mixtures with equivalence ratio, Φ of 0.8 to 1.6 have been used. Results show that rear ignition exhibits higher maximum overpressures and flame speeds in comparison to central ignition. It is confirmed that prior to the flame entry to the duct, the flow is chocked due to the sonic flow created at the duct entrance. Key words: Vented explosion; vent burst pressure; ignition location; sonic flow

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PROPAGATION OF THE BURNING WAVE IN A PULSED DETONATION COMBUSTOR OPERATING ON MIXTURES OF HEPTANE AND JET A-1 WITH AIR AND OXYGEN AT [O2/AIR] < 1

PROGRESS IN DETONATION RESEARCH ◽

10.30826/icpcd12a21 ◽

2020 ◽

Author(s):

M. S. ASSAD ◽

◽

O. G. PENYAZKOV ◽

I. I. CHERNUHO ◽

K. ALHUSSAN ◽

...

Keyword(s):

Wave Propagation ◽

Combustion Wave ◽

Equivalence Ratio ◽

Pressure Sensors ◽

Jet Fuel ◽

Propagation Time ◽

Burning Wave ◽

Pulsed Detonation ◽

Combustion Wave Propagation ◽

Fuel Jet

This work is devoted to the study of the dynamics of combustion wave propagation in oxygen-enriched mixtures of n-heptane with air and jet fuel "Jet A-1" in a small-size pulsed detonation combustor (PDC) with a diameter of 20 mm and a length less than 1 m. Experiments are carried out after the PDC reaches a stationary thermal regime when changing the equivalence ratio (ϕ = 0.73-1.89) and the oxygen-to-air ratio ([O2/air] = 0.15-0.60). The velocity of the combustion wave is determined by measuring the propagation time of the flame front between adjacent pressure sensors that form measurement segements along the PDC.

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Interaction of equivalence ratio fluctuations and flow fluctuations in acoustically forced swirl flames

International Journal of Spray and Combustion Dynamics ◽

10.1177/17568277211015544 ◽

2021 ◽

pp. 175682772110155

Author(s):

Vincent Kather ◽

Finn Lückoff ◽

Christian O. Paschereit ◽

Kilian Oberleithner

Keyword(s):

Equivalence Ratio ◽

Transfer Functions ◽

Transport Model ◽

Mode Conversion ◽

Fuel Injector ◽

One Dimensional ◽

Flow Fluctuations ◽

Non Linear ◽

Non Local ◽

Acoustic Forcing

The generation and turbulent transport of temporal equivalence ratio fluctuations in a swirl combustor are experimentally investigated and compared to a one-dimensional transport model. These fluctuations are generated by acoustic perturbations at the fuel injector and play a crucial role in the feedback loop leading to thermoacoustic instabilities. The focus of this investigation lies on the interplay between fuel fluctuations and coherent vortical structures that are both affected by the acoustic forcing. To this end, optical diagnostics are applied inside the mixing duct and in the combustion chamber, housing a turbulent swirl flame. The flame was acoustically perturbed to obtain phase-averaged spatially resolved flow and equivalence ratio fluctuations, which allow the determination of flux-based local and global mixing transfer functions. Measurements show that the mode-conversion model that predicts the generation of equivalence ratio fluctuations at the injector holds for linear acoustic forcing amplitudes, but it fails for non-linear amplitudes. The global (radially integrated) transport of fuel fluctuations from the injector to the flame is reasonably well approximated by a one-dimensional transport model with an effective diffusivity that accounts for turbulent diffusion and dispersion. This approach however, fails to recover critical details of the mixing transfer function, which is caused by non-local interaction of flow and fuel fluctuations. This effect becomes even more pronounced for non-linear forcing amplitudes where strong coherent fluctuations induce a non-trivial frequency dependence of the mixing process. The mechanisms resolved in this study suggest that non-local interference of fuel fluctuations and coherent flow fluctuations is significant for the transport of global equivalence ratio fluctuations at linear acoustic amplitudes and crucial for non-linear amplitudes. To improve future predictions and facilitate a satisfactory modelling, a non-local, two-dimensional approach is necessary.

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Emission Characteristics for Swirl Methane–Air Premixed Flames with Ammonia Addition

Energies ◽

10.3390/en14030662 ◽

2021 ◽

Vol 14 (3) ◽

pp. 662

Author(s):

Joanna Jójka ◽

Rafał Ślefarski

Keyword(s):

Equivalence Ratio ◽

Combustion Process ◽

Great Influence ◽

Emission Characteristics ◽

Firing Rates ◽

Numerical Tests ◽

Ammonia Addition ◽

Swirl Flame ◽

Reactor Network ◽

No Emissions

This paper details the experimental and numerical analysis of a combustion process for atmospheric swirl burners using methane with added ammonia as fuel. The research was carried out for lean methane–air mixtures, which were doped with ammonia up to 5% and preheated up to 473 K. A flow with internal recirculation was induced by burners with different outflow angles from swirling blades, 30° and 50°, where tested equivalence ratio was 0.71. The NO and CO distribution profiles on specified axial positions of the combustor and the overall emission levels at the combustor outlet were measured and compared to a modelled outcome. The highest values of the NO emissions were collected for 5% NH3 and 50° (1950 ppmv), while a reduction to 1585 ppmv was observed at 30°. The doubling of the firing rates from 15 kW up to 30 kW did not have any great influence on the overall emissions. The emission trend lines were not proportional to the raising share of the ammonia in the fuel. 3D numerical tests and a kinetic study with a reactor network showed that the NO outlet concentration for swirl flame depended on the recirculation ratio, residence time, wall temperature, and the mechanism used. Those parameters need to be carefully defined in order to get highly accurate NO predictions—both for 3D simulations and simplified reactor-based models.

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Numerical investigation of injection parameters and piston bowl geometries on emission and thermal performance of DI diesel engine

SN Applied Sciences ◽

10.1007/s42452-021-04633-1 ◽

2021 ◽

Vol 3 (6) ◽

Author(s):

Ikhtedar Husain Rizvi ◽

Rajesh Gupta

Keyword(s):

Diesel Engine ◽

Thermal Performance ◽

Equivalence Ratio ◽

Fuel Injection ◽

Injection Pressure ◽

Injection Nozzle ◽

Piston Bowl ◽

Injection Parameters ◽

Nozzle Size ◽

Engine Emission

AbstractTightening noose on engine emission norms compelled manufacturers globally to design engines with low emission specially NOx and soot without compromising their performance. Amongst various parameters, shape of piston bowls, injection pressure and nozzle diameter are known to have significant influence over the thermal performance and emission emanating from the engine. This paper investigates the combined effect of fuel injection parameters such as pressure at which fuel is injected and the injection nozzle size along with shape of piston bowl on engine emission and performance. Numerical simulation is carried out using one cylinder naturally aspirated diesel engine using AVL FIRE commercial code. Three geometries of piston bowls with different tumble and swirl characteristics are considered while maintaining the volume of piston bowl, compression ratio, engine speed and fuel injected mass constant along with equal number of variations for injection nozzle size and pressures for this analysis. The investigation corroborates that high swirl and large turbulence kinetic energy (TKE) are crucial for better combustion. TKE and equivalence ratio also increased as the injection pressure increases during the injection period, hence, enhances combustion and reduces soot formation. Increase in nozzle diameter produces higher TKE and equivalence ratio, while CO and soot emission are found to be decreasing and NOx formation to be increasing. Further, optimization is carried out for twenty-seven cases created by combining fuel injection parameters and piston bowl geometries. The case D2H1P1 (H1 = 0.2 mm, P1 = 200 bar) found to be an optimum case because of its lowest emission level with slightly better performance.

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