Quantifying Unmixedness in Lean Premixed Combustors Operating at High Pressure, Fired Conditions

1997 ◽  
Author(s):  
J. C. Barnes ◽  
A. M. Mellor
Keyword(s):  
High Pressure ◽  
Characteristic Time ◽  
Low Pressure ◽  
Companion Paper ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Time Model ◽  
Cold Flow ◽  
Lean Premixed ◽  
Consistent Method

Lean premixed combustor manufacturers require premixer concepts that provide homogeneity (mixedness) of the fuel which burns in the main flame. Ideally premixer evaluation would be conducted under realistic combustor operating conditions. However, current techniques typically are limited to cold—flow, low pressure (<14 atm) conditions or comparison of measured NOx emissions with others obtained in premixed systems. Thus, a simple, consistent method for quantifying unmixedness in lean premixed combustors operating at high pressure, fired operating conditions is proposed here, using the characteristic time model developed in the companion paper.

scholarly journals Effects of Unmixedness in Piloted–Lean Premixed Gas Turbine Combustors

1997 ◽  
Author(s):  
J. C. Barnes ◽  
A. M. Mellor
Keyword(s):  
Experimental Method ◽  
Gas Turbine ◽  
Characteristic Time ◽  
Companion Paper ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Time Model ◽  
No Formation ◽  
Lean Premixed ◽  
Fuel Characteristics

The characteristic time model (CTM) represents the dominant physical subprocesses related to combustor performance in terms of characteristic times. Properly formulated, these characteristic times account for variations in combustor geometry, fuel characteristics, and operating conditions. Here, a CTM for piloted–lean premixed combustor NOx emissions is used to investigate the sensitivity of NO formation in such combustors to fuel/air unmixedness and suggests an experimental method of evaluating premixed performance under fired conditions that is discussed in the companion paper.

Characteristic Time Model Correlation of NOx Emissions From Lean Premixed Combustors

1995 ◽  
Author(s):  
Donald M. Newburry ◽  
Arthur M. Mellor
Keyword(s):  
Gas Turbine ◽  
Diffusion Flame ◽  
Characteristic Time ◽  
Equivalence Ratio ◽  
Nox Emissions ◽  
Time Model ◽  
New Model ◽  
Gas Turbine Combustors ◽  
Ratio Data ◽  
Lean Premixed

The semi–empirical characteristic time model (CTM) has been used previously to correlate and predict emissions data from conventional diffusion flame, gas turbine combustors. The form of the model equation was derived for NOx emissions from laboratory flameholders and then extended to conventional gas turbine combustors. The model relates emissions to the characteristic times of distinct combustion subprocesses, with empirically determined model constants. In this paper, a new model is developed for lean premixed (LP) NOx emissions from a perforated plate flameholder combustor burning propane fuel. Several modifications to the diffusion flame CTM were required, including a new activation energy and a more complicated dependence on combustor pressure. Appropriate model constants were determined from the data, and the correlation results are reasonable. An attempt was made to validate the new model with LP NOx data for a different but geometrically similar flameholder operating at lower pressures. The predictions are good for the low equivalence ratio data. However, a systematic error in the reported equivalence ratios may be adversely affecting the predictions of the higher equivalence ratio data through the calculated adiabatic flame temperature.

Lean Blowout Limits and NOx Emissions of Turbulent, Lean Premixed, Hydrogen-Enriched Methane/Air Flames at High Pressure

2006 ◽  
Author(s):  
P. Griebel ◽  
E. Boschek ◽  
P. Jansohn
Keyword(s):  
High Pressure ◽  
Nox Reduction ◽  
Flame Temperature ◽  
Operating Conditions ◽  
Flame Stability ◽  
Nox Emissions ◽  
Lean Blowout ◽  
Wide Range ◽  
Pure Methane ◽  
Lean Premixed

Flame stability is a crucial issue in low NOx combustion systems operating at extremely lean conditions. Hydrogen enrichment seems to be a promising option to extend lean blowout limits of natural gas combustion. This experimental study addresses flame stability enhancement and NOx reduction in turbulent, high-pressure, lean premixed methane/air flames in a generic combustor, capable of a wide range of operating conditions. Lean blowout limits (LBO) and NOx emissions are presented for pressures up to 14 bars, bulk velocities in the range of 32–80 m/s, two different preheating temperatures (673 K, 773 K), and a range of fuel mixtures from pure methane to 20% H2/80% CH4 by volume. The influence of turbulence on LBO limits is discussed, too. In addition to the investigation of perfectly premixed H2-enriched flames, LBO and NOx are also discussed for hydrogen piloting. Experiments have revealed that a mixture of 20% hydrogen and 80% methane, by volume, can typically extend the lean blowout limit by roughly 10% compared to pure methane. The flame temperature at LBO is approximately 60 K lower resulting in the reduction of NOx concentration by ≈ 35% (0.5 → 0.3 ppm/15% O2).

Lean Blowout Limits and NOx Emissions of Turbulent, Lean Premixed, Hydrogen-Enriched Methane/Air Flames at High Pressure

2006 ◽  
Vol 129 (2) ◽  
pp. 404-410 ◽  
Author(s):  
P. Griebel ◽  
E. Boschek ◽  
P. Jansohn
Keyword(s):  
High Pressure ◽  
Nox Reduction ◽  
Flame Temperature ◽  
Operating Conditions ◽  
Flame Stability ◽  
Nox Emissions ◽  
Lean Blowout ◽  
Wide Range ◽  
Pure Methane ◽  
Lean Premixed

Flame stability is a crucial issue in low NOx combustion systems operating at extremely lean conditions. Hydrogen enrichment seems to be a promising option to extend lean blowout limits (LBO) of natural gas combustion. This experimental study addresses flame stability enhancement and NOx reduction in turbulent, high-pressure, lean premixed methane/air flames in a generic combustor capable of a wide range of operating conditions. Lean blowout limits and NOx emissions are presented for pressures up to 14bar, bulk velocities in the range of 32–80m∕s, two different preheating temperatures (673K, 773K), and a range of fuel mixtures from pure methane to 20% H2∕80%CH4 by volume. The influence of turbulence on LBO limits is also discussed. In addition to the investigation of perfectly premixed H2-enriched flames, LBO and NOx are also discussed for hydrogen piloting. Experiments have revealed that a mixture of 20% hydrogen and 80% methane, by volume, can typically extend the lean blowout limit by ∼10% compared to pure methane. The flame temperature at LBO is ∼60K lower resulting in the reduction of NOx concentration by ≈35%(0.5→0.3ppm∕15%O2).

The Port Width and Position Determination for Pressure-Exchange Ejector

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Wenjing Zhao ◽  
Dapeng Hu ◽  
Peiqi Liu ◽  
Yuqiang Dai ◽  
Jiupeng Zou ◽  
...  
Keyword(s):  
High Pressure ◽  
Performance Optimization ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Operating Conditions ◽  
Maximum Deviation ◽  
Dimensionless Time ◽  
Pressure Flow ◽  
Outlet Pressure ◽  
Pressure Exchange

A pressure-exchange ejector transferring energy by compression and expansion waves has the potential for higher efficiency. The width and position of each port are essential in pressure-exchange ejector design. A dimensionless time τ expressing both port widths and the positions of port ends was introduced. A prototype was designed and the experimental system was set up. Many sets of experiment with different geometrical arrangements were conducted. The results suggest that the efficiency greatly changes with the geometrical arrangements. The efficiency is about 60% at proper port widths and positions, while at improper geometrical arrangements, the efficiency is much lower and the maximum deviation may reach about 20%. The proper dimensionless port widths and positions at different operating conditions are obtained. For a fixed overall pressure ratio, the widths of the high pressure flow inlet and middle pressure flow outlet increase as the outlet pressure increases and the low pressure flow inlet width is reduced with a larger outlet pressure. The middle pressure flow outlet (MO) opening end remains constant at different outlet pressures. The positions of the high pressure flow inlet (HI) closed end and the low pressure flow inlet (LI) open end increase with the elevation of outlet pressure, however, the distance between the HI closing end and the LI opening end is constant. The port widths and positions have a significant influence on the performance of the pressure-exchange ejector. The dimensionless data obtained are very valuable for pressure-exchange ejector design and performance optimization.

Investigation on Flowfield and Fuel/Air Premixing Uniformities of Low Swirl Injector for Lean Premixed Gas Turbines

2021 ◽  
Author(s):  
Fujun Sun ◽  
Jianqin Suo ◽  
Zhenxia Liu
Keyword(s):  
Penetration Depth ◽  
Residence Time ◽  
Gas Turbines ◽  
Structural Parameters ◽  
Combustible Mixture ◽  
Operating Conditions ◽  
Flame Stability ◽  
Nox Emissions ◽  
Auto Ignition ◽  
Lean Premixed

Abstract Based on the development trend of incorporating fuel holes into swirler-vanes and the advantages of wide operating conditions as well as low NOx emissions of LSI, this paper proposes an original lean premixed LSI with a convergent outlet. The influence of key structures on flowfields and fuel/air premixing uniformities of LSI is investigated by the combination of laser diagnostic experiments and numerical simulations. The flowfields of LSI shows that the main recirculation zone is detached from the convergent outlet and its axial dimensions are smaller than that of HSI, which can decrease the residence time of high-temperature gas to reduce NOx emissions. The fuel/air premixing characteristics show that the positions and diameters of fuel holes affect fuel/air premixing by changing the penetration depth of fuel. And when the penetration depth is moderate, it can give full play to the role of swirling air in enhancing premixing of fuel and air. In addition, the increase of the length of the premixing section can improve the uniformity of fuel/ar premixing, but it can also weaken the swirl intensity and increase the residence time of the combustible mixture within the LSI, which can affect flame stability and increase the risk of auto-ignition. Therefore, the design and selection of LSI structural parameters should comprehensively consider the requirements of fuel/air mixing uniformity, flame stability and avoiding the risk of auto-ignition. The results can provide the technical basis for LSI design and application in aero-derivative and land-based gas turbine combustors.

Development of a Liquid-Fueled, Lean-Premixed Gas Turbine Combustor

1993 ◽  
Vol 115 (3) ◽  
pp. 554-562 ◽  
Author(s):  
L. H. Cowell ◽  
K. O. Smith
Keyword(s):  
Gas Turbine ◽  
Performance Testing ◽  
Operating Conditions ◽  
Operating Parameters ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Design Variables ◽  
Lean Premixed ◽  
Annular Combustor ◽  
Injector Design

Development of a lean-premixed, liquid-fueled combustor is in progress to achieve ultra-low NOx emissions at typical gas turbine operating conditions. A filming fuel injector design was tested on a bench scale can combustor to evaluate critical design and operating parameters for low-emissions performance. Testing was completed using No. 2 diesel. Key design variables tested include premixing length, swirler angle, injector centerbody diameter, and reduced liner cooling. NOx emissions below 12 ppmv at 9 bar pressure were measured. Corresponding CO levels were 50 ppmv. An optimized injector design was fabricated for testing in a three injector sector of an annular combustor. Operating parameters and test results are discussed in the paper.

Experimental Investigation of Self-Excited Combustion Instabilities in a Lean, Premixed, Gas Turbine Combustor at High Pressure

2017 ◽  
Author(s):  
Timo Buschhagen ◽  
Rohan Gejji ◽  
John Philo ◽  
Lucky Tran ◽  
J. Enrique Portillo Bilbao ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Operating Conditions ◽  
Chamber Pressure ◽  
Dynamic Mode ◽  
Combustion Instabilities ◽  
Compression Phase ◽  
Wide Range ◽  
Lower Amplitude ◽  
Lean Premixed

An experimental investigation of self-excited combustion instabilities in a high pressure, single-element, lean, premixed, natural gas dump-combustor is presented in this paper. The combustor is designed for optical access and is instrumented with high frequency pressure transducers at multiple axial locations. A parametric survey of operating conditions including inlet air temperature and equivalence ratio has been performed, which presents a wide range of peak to peak pressure fluctuations (p′) of the mean chamber pressure (pc). Two cases, Flame A and B with p′ /pc = 28% and p′/pc = 15% respectively, both presenting self-excited instabilities at the fundamental longitudinal (1L) mode of the combustion chamber, are discussed to study the coupling mechanism between flame-vortex interactions and the acoustic field in the chamber. OH*-chemiluminescence is used to obtain a map of global heat release distribution in the combustor. Phase conditioned analysis and Dynamic Mode Decomposition (DMD) analysis is performed, to highlight the contrasting mechanisms that lead to the two distinct instability regimes. Flame interactions with shear layer vortex structures just downstream of the dump plane during the compression phase of the acoustic cycle are found to augment the instability amplitude. Flame A engages strongly in this coupling, whereas Flame B is less affected and establishes a lower amplitude limit cycle.

scholarly journals Experimental study on the effect of high-pressure and low-pressure exhaust gas recirculation on gasoline engine and turbocharger

2018 ◽  
Vol 10 (11) ◽  
pp. 168781401880960 ◽  
Author(s):  
Xianqing Shen ◽  
Kai Shen ◽  
Zhendong Zhang
Keyword(s):  
High Pressure ◽  
Fuel Consumption ◽  
Gasoline Engine ◽  
Exhaust Gas Recirculation ◽  
Low Pressure ◽  
Operating Conditions ◽  
Exhaust Gas ◽  
Partial Load ◽  
Recirculation System ◽  
Gas Recirculation

The effects of high-pressure and low-pressure exhaust gas recirculation on engine and turbocharger performance were investigated in a turbocharged gasoline direct injection engine. Some performances, such as engine combustion, fuel consumption, intake and exhaust, and turbocharger operating conditions, were compared at wide open throttle and partial load with the high-pressure and low-pressure exhaust gas recirculation systems. The reasons for these changes are analyzed. The results showed EGR system of gasoline engine could optimize the cylinder combustion, reduce pumping mean effective pressure and lower fuel consumption. Low-pressure exhaust gas recirculation system has higher thermal efficiency than high-pressure exhaust gas recirculation, especially on partial load condition. The main reasons are as follows: more exhaust energy is used by the turbocharger with low-pressure exhaust gas recirculation system, and the lower exhaust gas temperature of engine would optimize the combustion in cylinder.

Sign in / Sign up

Export Citation Format

Share Document