Lean Operation of a Pulse Detonation Combustor by Fuel Stratification

2021 ◽  
Author(s):  
Fabian Habicht ◽  
Fatma Cansu Y\xe3\xbcCel ◽  
Niclas Hanraths ◽  
Neda Djordjevic ◽  
Christian Oliver Paschereit
Keyword(s):  
Pulse Detonation ◽  
Fuel Stratification

Lean Operation of a Pulse Detonation Combustor by Fuel Stratification

2020 ◽  
Author(s):  
Fabian E. Habicht ◽  
Fatma C. Yücel ◽  
Niclas Hanraths ◽  
Neda Djordjevic ◽  
Christian Oliver Paschereit
Keyword(s):  
Gas Turbines ◽  
Equivalence Ratio ◽  
Pressure Ratio ◽  
Initial Pressure ◽  
Detonation Initiation ◽  
Nox Emissions ◽  
Shock Focusing ◽  
Pulse Detonation ◽  
Lean Combustion ◽  
Fuel Stratification

Abstract Pressure gain combustion is a promising concept to substantially increase the thermal efficiency of gas turbines. One possible implementation that has been frequently investigated are pulse detonation combustors (PDCs), as they permit stable and reliable operation. At the same time, the need for part-load operation and low NOx emissions requires combustion concepts in the lean regime. However, realizing lean combustion is still very challenging in PDCs since the deflagration to detonation transition (DDT) is very sensitive to the reactant composition. The present work investigates an approach to realize lean combustion in PDC by applying fuel stratification experimentally. The scope is to find the necessary increase of fuel concentration inside the pre-detonation chamber to provide reliable DDT with respect to the overall equivalence ratio. Emission measurements in the exhaust of the PDC allow for a quantification of the NOx emissions as a function of the injected fuel profile. A valveless PDC test rig is used, which contains a shock focusing geometry for detonation initiation and is ignited by a spark plug close to the upstream end wall. The subsequent expansion of the burned gas and interaction of the flame front with turbulence leads to the formation of a leading shock inside the pre-detonation chamber, which is then focused inside a converging-diverging geometry. The successful initiation of a detonation wave by shock focusing is very sensitive to the pressure ratio across the leading shock, which can be influenced by initial pressure, reactant composition and flow velocity. Results reveal that fuel stratification allows for reliable detonation initiation at a global equivalence ratio of ϕglob = 0.65, whereas repeatable successful operation with non-stratified fuel injection is limited to ϕglob ≥ 0.85.

Lean Operation of a Pulse Detonation Combustor by Fuel Stratification

2020 ◽  
Author(s):  
Fabian Habicht ◽  
Fatma C. Yücel ◽  
Niclas Hanraths ◽  
Neda Djordjevic ◽  
Christian Oliver Paschereit
Keyword(s):  
Gas Turbines ◽  
Equivalence Ratio ◽  
Pressure Ratio ◽  
Initial Pressure ◽  
Detonation Initiation ◽  
Nox Emissions ◽  
Shock Focusing ◽  
Successful Operation ◽  
Pulse Detonation ◽  
Fuel Stratification

Abstract Pressure gain combustion is a promising concept to substantially increase the thermal efficiency of gas turbines. One possible implementation are pulse detonation combustors (PDCs), as they permit stable and reliable operation. Besides, the need for part-load operation and low NOx emissions requires combustion concepts in the lean regime. The present work investigates an approach to realize lean combustion in a PDC by applying fuel stratification experimentally. The necessary increase of fuel concentration inside the pre-detonation chamber to provide reliable DDT with respect to the overall equivalence ratio is identified. Emission measurements in the exhaust allow for a quantification of the NOx emissions as a function of the injected fuel profile. A valveless PDC test rig is used, which contains a shock-focusing geometry for detonation initiation and is ignited by a spark plug close to the upstream end wall. The subsequent expansion of the burned gas and interaction of the flame front with turbulence leads to the formation of a leading shock inside the pre-detonation chamber, which is then focused inside a converging-diverging geometry. The successful initiation of a detonation wave by shock focusing is very sensitive to the pressure ratio across the leading shock, which can be influenced by initial pressure, reactant composition and flow velocity. Results reveal that fuel stratification allows for reliable detonation initiation at a global equivalence ratio of 0.65, whereas repeatable successful operation with non-stratified fuel injection is limited to a global equivalence ratio greater than 0.85.

DETONABILITY OF FUEL-AIR MIXTURES IN TERMS OF DEFLAGRATION-TO-DETONATION TRANSITION

2020 ◽  
Author(s):  
S. M. FROLOV ◽  
◽  
V. I. ZVEGINTSEV ◽  
I. O. SHAMSHIN ◽  
M. V. KAZACHENKO ◽  
...  
Keyword(s):  
Natural Gas ◽  
Experimental Method ◽  
Pyrolysis Products ◽  
Ethylene Propylene ◽  
Pulse Detonation ◽  
Detonation Tube ◽  
Standard Pulse ◽  
Detonation Transition ◽  
Run Up ◽  
Propane Butane

A new experimental method for evaluating the detonability of fuel-air mixtures (FAMs) based on measuring the deflagration-to-detonation (DDT) run-up distance and/or time in a standard pulse detonation tube is used to rank gaseous premixed and nonpremixed FAMs by their detonability under substantially identical thermodynamic and gasdynamic conditions. In the experiments, FAMs based on hydrogen, acetylene, ethylene, propylene, propane-butane, n-pentane, and natural gas of various compositions, as well as FAMs based on the gaseous pyrolysis products of polyethylene (PE) and polypropylene (PP) are used: from extremely fuel-lean to extremely fuel-rich at normal temperatures and pressures.

Recent ASI Progress in Pulse Detonation Rocket Engine (PDRE) Hardware Development

1999 ◽  
Author(s):  
D. C. Mueller ◽  
T. E. Bratkovich ◽  
K. Lupkes ◽  
S. Henderson ◽  
J. T. Williams
Keyword(s):  
Rocket Engine ◽  
Pulse Detonation ◽  
Hardware Development ◽  
Pulse Detonation Rocket Engine

scholarly journals Optical Investigation of a Partial Fuel Stratification Strategy to Stabilize Overall Lean Operation of a DISI Engine Fueled with Gasoline and E30

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 396
Author(s):  
Cinzia Tornatore ◽  
Magnus Sjöberg
Keyword(s):  
Volume Fraction ◽  
Direct Injection ◽  
Combustion Process ◽  
Pilot Injection ◽  
Optical Investigation ◽  
Flame Kernel ◽  
Lean Combustion ◽  
Fuel Stratification ◽  
Spark Plug ◽  
Initial Flame

This paper offers new insights into a partial fuel stratification (PFS) combustion strategy that has proven to be effective at stabilizing overall lean combustion in direct injection spark ignition engines. To this aim, high spatial and temporal resolution optical diagnostics were applied in an optically accessible engine working in PFS mode for two fuels and two different durations of pilot injection at the time of spark: 210 µs and 330 µs for E30 (gasoline blended with ethanol by 30% volume fraction) and gasoline, respectively. In both conditions, early injections during the intake stroke were used to generate a well-mixed lean background. The results were compared to rich, stoichiometric and lean well-mixed combustion with different spark timings. In the PFS combustion process, it was possible to detect a non-spherical and highly wrinkled blue flame, coupled with yellow diffusive flames due to the combustion of rich zones near the spark plug. The initial flame spread for both PFS cases was faster compared to any of the well-mixed cases (lean, stoichiometric and rich), suggesting that the flame propagation for PFS is enhanced by both enrichment and enhanced local turbulence caused by the pilot injection. Different spray evolutions for the two pilot injection durations were found to strongly influence the flame kernel inception and propagation. PFS with pilot durations of 210 µs and 330 µs showed some differences in terms of shapes of the flame front and in terms of extension of diffusive flames. Yet, both cases were highly repeatable.

scholarly journals Detonation initiation by shock focusing at elevated pressure conditions in a pulse detonation combustor

2020 ◽  
Vol 12 ◽  
pp. 175682772092171
Author(s):  
Fabian E Habicht ◽  
Fatma C Yücel ◽  
Joshua AT Gray ◽  
Christian O Paschereit
Keyword(s):  
Success Rate ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Initial Pressure ◽  
Detonation Initiation ◽  
Major Influence ◽  
Mean Flow ◽  
Shock Focusing ◽  
Pulse Detonation

This work contains experimental investigations on the correlation of the detonation initiation process via a shock-focusing device with various initial pressures and mass flow rates. A pulse detonation combustor is operated with stoichiometric hydrogen--air--oxygen mixtures in single cycle operation. A rotationally symmetric shock-focusing geometry evokes the onset of a detonation by the focusing of the reflected leading shock wave, while a blockage plate at the rear end of the test rig is applied to induce an elevated initial pressure. The results show that the reactivity has a major influence on the success rate of detonation initiation. However, measurements with different blockage plates suggest that the mass flow rate has to be considered as well when predicting the success rate. Three main statements can be drawn from the results. (1) An increase in the mean flow velocity induces higher velocity fluctuations which result in a stronger leading shock ahead of the accelerating deflagration front. (2) An increase in the initial static pressure reduces the critical shock strength that must be exceeded to ensure successful detonation initiation by shock focusing. (3) Since the initial pressure is directly linked to the mass flow rate, these contrary trends can cancel each other out, which could be observed for 40% vol. of oxygen in the oxidizer. High-speed images were taken, which confirm that the detonation is initiated in the center of the converging--diverging nozzle due to focusing of the leading shock.

scholarly journals Study on Influence of Diameter on Detonation Acoustic Characteristics of Pulse Detonation Engine

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Gui-yang Xu ◽  
Chun-guang Wang ◽  
Yan-fang Zhu ◽  
Hong-yan Li ◽  
Lun-kun Gong ◽  
...  
Keyword(s):  
Acoustic Characteristic ◽  
Pulse Detonation Engine ◽  
Acoustic Characteristics ◽  
Experiment System ◽  
Pulse Detonation ◽  
Impact Noise ◽  
Maximum Duration ◽  
Detonation Engine ◽  
Set Up ◽  
Different Diameters

AbstractThe experiment system of pulse detonation engine is set up to investigate on influence of diameter on detonation acoustic characteristic. The research of detonation acoustic characteristic of pulse detonation engine for four different diameters in different angles is carried out. Results from the test show that as the PDE diameter increasing, there are increases in amplitudes of impact noise in all angles, and the growth rate of amplitude of impact noise in the 90° direction is generally greater than that in the 0° direction. The smaller PDE diameter is, the distance of most obvious directivity at 0° turning to most obvious directivity at 30° is shorter. When the distance is shorter, such as 200 mm, the duration of detonation acoustic is increasing with the increase of PDE diameter, however, when the distance is longer, such as 3000 mm, it is just the opposite. The maximum duration of detonation acoustic is appeared in 3000 mm under 30 mm PDE diameter which reaches to 1.44 ms.

A novel hybrid aircraft propulsion based on the DEA compressor—Part A: Design

2021 ◽  
pp. 095441002110253
Author(s):  
Babak Aryana
Keyword(s):  
High Performance ◽  
Static Condition ◽  
Propulsion System ◽  
Hybrid Propulsion ◽  
Pulse Detonation ◽  
Low Emission ◽  
Wide Range ◽  
Exit Nozzle ◽  
Distributed Propulsion ◽  
Detonation Process

This two-part article introduces a novel hybrid propulsion system based on the DEA compressor. The system encompasses a Pulse Detonation TurboDEA as the master engine that supplies several full-electric ancillary thrusters called DEAThruster. The system, called the propulsion set, can be categorized as a distributed propulsion system based on the design mission and number of ancillary thrusters. Part A of this article explains the design process comprising intake, compressor, detonation process, diffuser, axial turbine, and the exit nozzle. The main target is to design a high-performance low emission propulsion system capable of serving in a wide range of altitudes and flight Mach numbers that covers altitudes up to 20,000 m and flight Mach number up to the hypersonic edge. Designing the propulsion set, the design point is considered at the static condition in the sea level. Design results show the propulsion set can satisfy all requirements necessary for its mission.

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