Auto-Ignition of Gas Turbine Lubricating Oils in a Shock Tube Using Spray Injection

Abstract In choosing the lubricating oil for a gas turbine system, properties such as viscosity, viscosity index, corrosion prevention, and thermal stability are chosen to optimize turbine longevity and efficiency. Another property that needs to be considered is the lubricant's reactivity, as the lubricant's ability to resist combustion during turbine operation is highly desirable. In evaluating a method to define reactivity, the extremely low vapor pressure of these lubricants makes conventional vaporization by heating impractical. To this end, a new experiment was designed and tested to evaluate the reactivity of lubricating oils using an existing shock-tube facility at Texas A&M University equipped with an automotive fuel injector. This experiment disperses a pre-measured amount of lubricant into a region of high-temperature air to study auto-ignition. To ensure proper dispersal, a laser extinction diagnostic was used to detect the lubricant particles behind the reflected shock as they are dispersed and vaporized. An OH* chemiluminescence diagnostic was used to determine ignition delay time. Using this method, various 32-, 36-, and 46-weight lubricants identified as widely used in the gas turbine industry were tested. Experiments were conducted in post-reflected shock conditions around 1370 K (2006 ºF) and 1.2 atm, where ignition delay time, peak OH* emission, and time-to-peak values were recorded and compared. Ignition was observed for all but one of the lubricants at these conditions, and mild to strong ignition was observed for the other lubricants with varying ignition delay times.

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Auto-Ignition of Gas Turbine Lubricating Oils in a Shock Tube Using Spray Injection

Volume 4A: Combustion, Fuels, and Emissions ◽

10.1115/gt2020-14987 ◽

2020 ◽

Author(s):

Sean P. Cooper ◽

Zachary K. Browne ◽

Sulaiman A. Alturaifi ◽

Olivier Mathieu ◽

Eric L. Petersen

Keyword(s):

Shock Tube ◽

Gas Turbine ◽

Ignition Delay ◽

Delay Time ◽

Ignition Delay Time ◽

Lubricating Oil ◽

Fuel Injector ◽

Lubricating Oils ◽

Reflected Shock ◽

Auto Ignition

Abstract In choosing the lubricating oil for a gas turbine system, properties such as viscosity, viscosity index, corrosion prevention, and thermal stability are chosen to optimize turbine longevity and efficiency. Another property that needs to be considered is the lubricant’s reactivity, as the lubricant’s ability to resist combustion during turbine operation is highly desirable. In evaluating a method to define reactivity, the extremely low vapor pressure of these lubricants makes conventional vaporization by heating impractical due to the high temperatures and fuel cracking as well as issues with preferential vaporization. To this end, a new experiment was designed and tested to evaluate the reactivity of lubricating oils using an existing shock-tube facility at Texas A&M University equipped with an automotive fuel injector. This experiment disperses a pre-measured amount of lubricant into a region of high-temperature air to study auto-ignition. To ensure proper dispersal, a laser extinction diagnostic was used to measure the lubricant particles behind the reflected shock as they are dispersed and vaporized. An OH* chemiluminescence diagnostic measuring light emitted during combustion at around 306 nm was used to determine ignition delay time. Pressure was also measured at the sidewall and endwall positions for test repeatability and exothermicity of the experiments. The methods were validated by conducting experiments with ethanol and comparing the results to previous heated shock-tube experiments conducted in the same facility. Using this method, various 32-, 36-, and 46-weight lubricants identified as widely used in the gas turbine industry were tested. Experiments were conducted in post-reflected shock conditions around 1370K (2006 °F) and 1.2 atm, where ignition delay time, peak OH* emission and time-to-peak values were recorded and compared. Ignition was observed for all but one of the lubricants at these conditions, and mild to strong ignition was observed for the other lubricants with varying ignition delay times.

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Ignition Studies of C1–C7 Natural Gas Blends at Gas-Turbine Relevant Conditions

Volume 4B: Combustion, Fuels, and Emissions ◽

10.1115/gt2020-15826 ◽

2020 ◽

Author(s):

Amrit Bikram Sahu ◽

A. Abd El-Sabor Mohamed ◽

Snehasish Panigrahy ◽

Gilles Bourque ◽

Henry Curran

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Ignition Delay ◽

Delay Time ◽

Ignition Delay Time ◽

Gas Mixtures ◽

Auto Ignition ◽

Wide Range ◽

Detailed Kinetic Model ◽

Sensitization Effect

Abstract New ignition delay time measurements of natural gas mixtures enriched with small amounts of n-hexane and n-heptane were performed in a rapid compression machine to interpret the sensitization effect of heavier hydrocarbons on auto-ignition at gas-turbine relevant conditions. The experimental data of natural gas mixtures containing alkanes from methane to n-heptane were carried out over a wide range of temperatures (840–1050 K), pressures (20–30 bar), and equivalence ratios (φ = 0.5 and 1.5). The experiments were complimented with numerical simulations using a detailed kinetic model developed to investigate the effect of n-hexane and n-heptane additions. Model predictions show that the addition of even small amounts (1–2%) of n-hexane and n-heptane can lead to increase in reactivity by ∼40–60 ms at compressed temperature (TC) = 700 K. The ignition delay time (IDT) of these mixtures decrease rapidly with an increase in concentration of up to 7.5% but becomes almost independent of the C6/C7 concentration beyond 10%. This sensitization effect of C6 and C7 is also found to be more pronounced in the temperature range 700–900 K compared to that at higher temperatures (> 900 K). The reason is attributed to the dependence of IDT primarily on H2O2(+M) ↔ 2ȮH(+M) at higher temperatures while the fuel dependent reactions such as H-atom abstraction, RȮ2 dissociation or Q.OOH + O2 reactions are less important compared to 700–900 K, where they are very important.

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Ignition of Lean Methane-Based Fuel Blends at Gas Turbine Pressures

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2720543 ◽

2007 ◽

Vol 129 (4) ◽

pp. 937-944 ◽

Cited By ~ 65

Author(s):

Eric L. Petersen ◽

Joel M. Hall ◽

Schuyler D. Smith ◽

Jaap de Vries ◽

Anthony R. Amadio ◽

...

Keyword(s):

Activation Energy ◽

Temperature Dependence ◽

Gas Turbine ◽

Chemical Kinetics ◽

Ignition Delay ◽

Delay Time ◽

Ignition Delay Time ◽

Ignition Time ◽

Fuel Blends ◽

Reflected Shock

Shock-tube experiments and chemical kinetics modeling were performed to further understand the ignition and oxidation kinetics of lean methane-based fuel blends at gas turbine pressures. Such data are required because the likelihood of gas turbine engines operating on CH4-based fuel blends with significant (>10%) amounts of hydrogen, ethane, and other hydrocarbons is very high. Ignition delay times were obtained behind reflected shock waves for fuel mixtures consisting of CH4, CH4∕H2, CH4∕C2H6, and CH4∕C3H8 in ratios ranging from 90/10% to 60/40%. Lean fuel/air equivalence ratios (ϕ=0.5) were utilized, and the test pressures ranged from 0.54 to 30.0atm. The test temperatures were from 1090K to 2001K. Significant reductions in ignition delay time were seen with the fuel blends relative to the CH4-only mixtures at all conditions. However, the temperature dependence (i.e., activation energy) of the ignition times was little affected by the additives for the range of mixtures and temperatures of this study. In general, the activation energy of ignition for all mixtures except the CH4∕C3H8 one was smaller at temperatures below approximately1300K(∼27kcal∕mol) than at temperatures above this value (∼41kcal∕mol). A methane/hydrocarbon–oxidation chemical kinetics mechanism developed in a recent study was able to reproduce the high-pressure, fuel-lean data for the fuel/air mixtures. The results herein extend the ignition delay time database for lean methane blends to higher pressures (30atm) and lower temperatures (1100K) than considered previously and represent a major step toward understanding the oxidation chemistry of such mixtures at gas turbine pressures. Extrapolation of the results to gas turbine premixer conditions at temperatures less than 800K should be avoided however because the temperature dependence of the ignition time may change dramatically from that obtained herein.

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The Measurement and Prediction of Gaseous Hydrocarbon Fuel Auto-Ignition Delay Time at Realistic Gas Turbine Operating Conditions

Volume 2: Turbo Expo 2005 ◽

10.1115/gt2005-68736 ◽

2005 ◽

Cited By ~ 3

Author(s):

G.-J. M. Sims ◽

A. R. Clague ◽

R. W. Copplestone ◽

K. R. Menzies ◽

M. A. MacQuisten

Keyword(s):

Kinetic Model ◽

Gas Turbine ◽

Ignition Delay ◽

Test Section ◽

Delay Time ◽

Ignition Delay Time ◽

Chemical Kinetic ◽

Operating Conditions ◽

Chemical Kinetic Model ◽

Auto Ignition

Auto-ignition delay time measurements have been attempted for a variety of gaseous fuels on a flow rig at gas turbine relevant operating conditions. The residence time of the flow rig test section was approximately 175 ms. A chemical kinetic model has been used in Senkin, one of the applications within the Chemkin package, to predict the auto-ignition delay time measured in the experiment. The model assumes that chemistry is the limiting factor in the prediction and makes no account of the fluid dynamic properties of the experiment. Auto-ignition delay time events were successfully recorded for ethylene at approximately 16 bar, 850K and at equivalence ratios between 2.6 and 3.3. Methane, natural gas and ethylene (0.5 < φ < 2.5) failed to auto-ignite within the test section. Model predictions were found to agree with the ethylene measurements, although improved qualification of the experimental boundary conditions is required in order to better understand the dependence of auto-ignition delay on the physical characteristics of the flow rig. The chemical kinetic model used in this study was compared with existing ‘low temperature’ measurements and correlations for methane and natural gas and was found to be in good agreement.

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Shock Tube Study of Nitric Oxide Addition on Ignition Delay Time of n-Dodecane/Air Mixture

31st International Symposium on Shock Waves 1 ◽

10.1007/978-3-319-91020-8_15 ◽

2019 ◽

pp. 143-149

Author(s):

Jiankun Shao ◽

Yangye Zhu ◽

Chris Almodovar ◽

David F. Davidson ◽

Ronald K. Hanson

Keyword(s):

Nitric Oxide ◽

Shock Tube ◽

Ignition Delay ◽

Delay Time ◽

Ignition Delay Time ◽

Oxide Addition ◽

Tube Study

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A Numerical Study on the Low Limit Auto-Ignition Temperature of Syngas and Modification of Chemical Kinetic Mechanism

Volume 3A: Fluid Applications and Systems ◽

10.1115/ajkfluids2019-5432 ◽

2019 ◽

Author(s):

Seung Eon Jang ◽

Jin Park ◽

Sang Hyeon Han ◽

Hong Jip Kim ◽

Ki Sung Jung ◽

...

Keyword(s):

Low Temperature ◽

Temperature Region ◽

Ignition Delay ◽

Delay Time ◽

Ignition Delay Time ◽

Kinetic Mechanism ◽

Chemical Kinetic ◽

Numerical Results ◽

Auto Ignition ◽

Chemical Kinetic Mechanism

Abstract In this study, the auto ignition with low limit temperature of syngas has been numerically investigated using a 2-D numerical analysis. Previous study showed that auto ignition was observed at above 860 K in co-flow jet experiments using syngas and dry air. However, the auto ignition at this low temperature range could not be predicted with existing chemical mechanisms. Inconsistency of the auto ignition temperature between the experimental and numerical results is thought to be due to the inaccuracy of the chemical kinetic mechanism. The prediction of ignition delay time and sensitivity analysis for each chemical kinetic mechanism were performed to verify the reasons of the inconsistency between the experimental and numerical results. The results which were calculated using the various mechanisms showed significantly differences in the ignition delay time. In this study, we intend to analyze the reason of discrepancy to predict the auto ignition with low pressure and low temperature region of syngas and to improve the chemical kinetic mechanism. A sensitive analysis has been done to investigate the reaction steps which affected the ignition delay time significantly, and the reaction rate of the selected reaction step was modified. Through the modified chemical kinetic mechanism, we could identify the auto ignition in the low temperature region from the 2-D numerical results. Then CEMA (Chemical Explosive Mode Analysis) was used to validate the 2-D numerical analysis with modified chemical kinetic mechanism. From the validation, the calculated λexp, EI, and PI showed reasonable results, so we expect that the modified chemical kinetic mechanism can be used in various low temperature region.

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Ignition-Delay Time Measurements of Heavy Hydrocarbons in an Aerosol Shock Tube

AIAA Scitech 2020 Forum ◽

10.2514/6.2020-2144 ◽

2020 ◽

Author(s):

Joshua Hargis ◽

Sean Cooper ◽

Olivier Mathieu ◽

Bing Guo ◽

Eric L. Petersen

Keyword(s):

Shock Tube ◽

Ignition Delay ◽

Delay Time ◽

Ignition Delay Time ◽

Heavy Hydrocarbons

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Interpretation of Flow Reactor Based Ignition Delay Measurements

Volume 2: Combustion, Fuels and Emissions ◽

10.1115/gt2009-60268 ◽

2009 ◽

Cited By ~ 3

Author(s):

David Beerer ◽

Vincent McDonell ◽

Scott Samuelsen ◽

Leonard Angello

Keyword(s):

High Pressure ◽

Gas Turbine ◽

Residence Time ◽

Ignition Delay ◽

Delay Time ◽

Ignition Delay Time ◽

Flow Reactor ◽

Ignition Delay Times ◽

Delay Times ◽

Recirculation Zones

Compositional variation of global gas supplies is becoming a growing concern. Both the range and rate-of-change of this variation is expected to increase as global markets for Liquefied Natural Gas (LNG) continue to expand. Greater fuel composition variation poses increased operational risk to gas turbine engines employing lean premixed combustion systems. Information on ignition delay at high pressure and intermediate temperatures is valuable for lean premixed gas turbine design. In order to avoid autoignition of the fuel/air mixture within the premixer, the ignition delay time must be greater than the residence time. Evaluating the residence time is not a straight forward task because of the complex aerodynamics due to recirculation zones, separation regions, and boundary layers effects which may create regions where the local residence times may be longer than the bulk or average residence time. Additionally, reliable experiments on ignition delay at gas turbine conditions are difficult to conduct. Devices for testing include shock tubes, rapid compression machine and flow reactors. In a flow reactor ignition delay data are commonly determined by measuring the distance from the fuel injector to the reaction front (L) and dividing it by the bulk or average flow velocity (U) under steady flow conditions to obtain a bulk residence time which is assumed to be equal to the ignition delay time. However this method is susceptible to the same boundary layer effects or recirculation zones found in premixers. An alternative method for obtaining ignition delay data in a flow reactor is presented herein, where ignition delay times are obtained by measuring the time difference between fuel injection and ignition using high speed instrumentation. Ignition delay times for methane, ethane and propane at gas turbine conditions were in the range of 40–500 ms. The results obtained show excellent agreement with recently proposed chemical mechanisms for hydrocarbons at low temperature/high pressure conditions.

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