Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “combustion research”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Challenges to Laser-Based Imaging Techniques in Gas Turbine Combustor Systems for Aerospace Applications

Increasingly severe constraints on emissions, noise and fuel efficiency must be met by the next generation of commercial aircraft powerplants. At NASA Lewis Research Center (LeRC) a cooperative research effort with industry is underway to design and test combustors that will meet these requirements. To accomplish these tasks, it is necessary to gain both a detailed understanding of the combustion processes and a precise knowledge of combustor and combustor sub-component performance at close to actual conditions. To that end, researchers at LeRC are engaged in a comprehensive diagnostic investigation of high pressure reacting flowfields that duplicate conditions expected within the actual engine combustors. Unique, optically accessible flame-tubes and sector rig combustors, designed especially for these tests. afford the opportunity to probe these flowfields with the most advanced, laser-based optical diagnostic techniques. However, these same techniques, tested and proven on comparatively simple bench-top gaseous flame burners, encounter numerous restrictions and challenges when applied in these facilities. These include high pressures and temperatures, large flow rates, liquid fuels, remote testing, and carbon or other material deposits on combustor windows. Results are shown that document the success and versatility of these nonintrusive optical diagnostics despite the challenges to their implementation in realistic systems.

Locke, Randy J.↗
DOE OSTI2020

Probing the low-temperature chemistry of methyl hexanoate: Insights from oxygenate intermediates

Understanding the combustion of methyl esters is crucial to elucidate kinetic pathways and predict combustion parameters, soot yields, and fuel performance of biodiesel, however most kinetic studies of methyl esters have focused on smaller, surrogate model esters. Methyl hexanoate is a larger methyl ester approaching the chain length of methyl esters found in biodiesel and has not received as much research attention as other smaller esters. The purpose of this work is to present the first atmospheric pressure combustion data of methyl hexanoate, CH 3 CH 2 CH 2 CH 2 CH 2 COOCH 3 . Mixtures of 2% methyl hexanoate in O 2 and N 2 are studied using a plug flow reactor at atmospheric pressure, wall temperatures from 573 to 973 K, residence times from roughly 1-2 s., and fuel equivalence ratios of 1, 1.5, and 2. Exhaust gases are analyzed by a gas chromatograph-mass spectrometer system and species mole fractions are presented. Here, the literature model shows satisfactory agreement with the experimental species profiles and improvements for future mechanistic studies are suggested. In particular, this work proposes new unimolecular decomposition pathways of methyl hexanoate to form methanol or methyl acetate. Furthermore, the experiment detected three unsaturated esters that are direct products of the low temperature oxidation chemistry and it provides more insight into branching ratios for the formation of methyl hexanoate radicals and for the decomposition of hydroperoxyalkyl radicals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Deactivation trends of Pd/SSZ-13 under the simultaneous presence of NO, CO, hydrocarbons and water for passive NO x adsorption

Pd-functionalized chabazite (Pd/SSZ-13) was evaluated for passive NO x adsorption (PNA) using low temperature combustion with diesel (LTC-D) reaction feed of the “United States Driving Research and Innovation for Vehicle efficiency and Energy sustainability” (U.S.DRIVE) protocol. Notably as per the protocol conditions, 12% O 2 + 6% CO 2 + 6% H 2 O was flown in all cases. NO-uptake studies in the presence of the LTC-D feed showed a systematic decline with (NO:Pd)molar changing from 0.5 to 0.4 after 10 trials. Control experiments showed more pronounced decline for NO + CO case, with appreciable intial (NO:Pd)molar value of 0.4 yet comparable-to-the-LTC-D-feed decline after 8 trials. CO-induced particle formation and larger extent of particle sintering was also evident from TEM analysis. Other controls did not exhibit trial-dependent deactivation as(NO:Pd)molar values were constant, at 0.3, 0.2, 0.5 and 0.2 for the NO, NO+H 2 , NO + unsaturated hydrocarbon (C 2 H 4 , C 3 H 6 ) and NO + saturated HC (C 3 H 8 , C 10 H 22 ) feeds respectively. In addition to these quantitative differences, desorption behaviors are qualitatively different. While only one major desorption event is observed for the full LTC-D, NO+ CO and NO+ unsaturated HC-controls, desorption occurs in two distinct stages for NO, NO + saturated HCs and initial-NO+H 2 trials. This arises due to inherent differences in Pd sites while exposed to these chemically distinct feeds. Furthermore, presence of reducing agents such as CO and unsaturated HCs in the feed result in almost complete elimination of lower, sub-200 °C desorption peak. The higher temperature desorption peaks, at > 300 °C is associated with NO strongly bound to ionic Pd sites and are prevalent under reducing conditions. Using DRIFTS also, three complexes leading to PNA are assigned, [O = N–Pd 2 +(OH)–Z], [O = N–Pd 2 +(Z2)] and [O = N–Pd 2 +(H 2 O)y–Z] with the latter being clearly observed upon water exposure. Pd/SSZ-13 showed higher hydrocarbon trapping than the SSZ-13 counterpart.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Soot Formation and Growth in Toluene/Ethylene Combustion Catalyzed by Ruthenium Acetylacetonate

Ruthenium-based compounds are efficient catalysts to enhance combustion performance and suppress soot emission. However, systematic mechanism and in-situ research on reducing soot are rarely addressed. In this study, ruthenium acetylacetonate (Ru(C 5 H 7 O 2 ) 3 , Ru(acac) 3 ) was utilized as the catalyst precursor in different concentration conditions to investigate its impacts on the size, volume, and morphology of the soot particles in the ethylene flames with central toluene injection. The soot particles were detected by in-situ small-angle X-ray scattering (SAXS) and ex-situ transmission electron microscopy (TEM). This study confirms that Ru(acac) 3 can suppress the surface growth for the primary soot particles, but no significant change of the morphology has been discovered for the aggregates. Compared with the undoped flame, the volume of the soot particles in the Ru(acac) 3 -doped flames is lower and the particle size is smaller, indicating a valid inhibition effect of Ru(acac) 3 on the soot emission by affecting its surface growth and oxidation process. In conclusion, despite the remarkable distinction between the undoped and doped flames, no obvious difference is found between the flames with different catalyst concentrations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1989

Hypersonic propulsion

The paper reviews the whys and hows of the concept of supersonic combustion for hypersonic propulsion. Attention is given to the problem areas, the current research and development efforts, and their implications. The operating boundary of the SCRAMJET is reasonably well defined. The paper also explores some air-breathing alternatives that may go beyond SCRAMJETS.

Cheng, SIN-I.↗
NASA NTRS1999

Control of Mixing and Reactive Flow Processes

The interdisciplinary field of reactive flow control is one that holds a great deal of promise for the optimization of complex phenomena occurring in many practical systems, ranging from automobile and gas turbine engines to environmental thermal destruction systems. The fundamental underpinnings of combustion control, however, require a detailed level of understanding of complex reactive flow phenomena, and, in the case of closed-loop active control, require the ability to sense (monitor) and actuate (manipulate) flow processes in a spatially distributed manner in "near real time". Hence the ultimate growth and success of the field of reactive flow control is intimately linked: 1) to advances in the understanding, simulation, and model reduction for complex reactive flows, 2) to the development of experimental diagnostic techniques, in particular, to the development of physically robust sensors, and 3) to the development of a framework or frameworks for generation of closed loop control algorithms suitable for unsteady, nonlinear reactive flow systems. The present paper seeks to outline the potential benefits and technical challenges that exist for mixing and combustion control in fundamental as well as practical systems and to identify promising research directions that could help meet these challenges.

Karagozian, A. R.↗
NASA NTRS2001

Reaction Mechanisms and Particle Interaction in Burning Two-Phase Systems

The main objective of this research is to understand the mechanisms by which particle interactions affect ignition and combustion in the two-phase systems. Combustion of metal aerosols representing the two-phase systems is carried out in the microgravity environment enabling one to avoid the buoyant flows that mask the particle motion due to the particle-particle interaction effects. In addition, relatively large, e.g., 100 micron diameter particles can be used, that remain aerosolized (i.e., do not fall down as they would at normal gravity) so that their behavior ahead, behind, and within the propagating flame can be resolved optically. An experimental apparatus exploiting this approach has been designed for the 2.2-s drop tower microgravity experiments. A typical experiment includes fluidizing metal particles under microgravity in an acoustic field, turning off the acoustic exciter, and igniting the created aerosol at a constant pressure using a hot wire igniter. The flame propagation and details of the individual particle combustion and particle interactions are studied using high-speed movie and video cameras coupled with microscope lenses to resolve individual particles. Recorded flame images are digitized and various image processing techniques including flame position tracking, color separation, and pixel by pixel image comparisons are employed to understand the processes occurring in the burning aerosols. Condensed combustion products are collected after each experiment for the phase, composition, and morphology analyses. New experiments described in this paper address combustion of Ti and Al particle clouds in air and combustion of Mg particle clouds in CO2. In addition, microgravity combustion experiments have been conducted with the particles of the newly produced Al-Mg mechanical alloys aerosolized in air.

Dreizin, Edward L.↗
NASA NTRS2003

STS-107 Flight Day 13 Highlights

This video shows the activities of the STS-107 crew on flight day 13 of the Columbia orbiter's final mission. The crew members include: Rick Husband, Commander; William McCool, Pilot; Kalpana Chawla, David Brown, Michael Anderson, Laurel Clark, Mission Specialists; Ilan Ramon, Payload Specialist. The primary activities of flight day 13 are spaceborne experiments, including troubleshooting undertaken by Mission Specialist Chawla on the Water Mist Fire Suppression (MIST) experiment. Chawla performs troubleshooting tasks relayed to her by Mission Control. She shows Mission Control the location of air and water in a transparent hose that is part of the atomizer on the exterior of the combustion module. She also changes the atomizer head. All six Space Technology and Research Students (STARS) experiments are profiled in the video. These experiments are on ants, crystal growth in a chemical garden, fish embryos, carpenter bees, spiders, and silkworms. The video also includes a view of the southeast Texas coast near Houston, and a view of Portugal, Spain, Gibraltar, Morocco, and the Sahara Desert. The video ends with an explanation of roses at Mission Control which commemorate astronauts who have died on missions.

Source record↗
NASA NTRS1977

Composite propellant combustion modeling studies

A review is presented of theoretical and experimental studies of composite propellant combustion. The theoretical investigations include a model of the combustion of a nonmetallized ammonium perchlorate (AP) propellant (noting time scales for vapor-phase combustion and the condensed phase) and response functions in pressure-coupled oscillations. The experimental studies are discussed with reference to scale-modeling apparatus, flame standoff distance versus velocity as a function of pressure, and results from T-burner firings of a nonmetallized AP/polysulfide propellant. Research applications including problems with nitramine propellants, the feasibility of stop-restart rockets with salt quench, and combustion problems in large boosters are outlined.

Ramohalli, K.↗
NASA NTRS1995

Microgravity research opportunities for the 1990s

The Committee on Microgravity Research (CMGR) was made a standing committee of the Space Studies Board (SSB) and charged with developing a long-range research strategy. The scientific disciplines contained within the microgravity program, and covered in this report, include fluid mechanics and transport phenomena, combustion, biological sciences and biotechnology, materials science, and microgravity physics. The purpose of this report is to recommend means to accomplish the goal of advancing science and technology in each of the component disciplines. Microgravity research should be aimed at making significant impacts in each discipline emphasized. The conclusions and recommendations presented in this report fall into five categories: (1) overall goals for the microgravity research program; (2) general priorities among the major scientific disciplines affected by gravity; (3) identification of the more promising experimental challenges and opportunities within each discipline; (4) general scientific recommendations that apply to all microgravity-related disciplines; and (5) recommendations concerning administrative policies and procedures that are essential to the conduct of excellent laboratory science.

Source record↗
NASA NTRS2003

National Combustion Code Validated Against Lean Direct Injection Flow Field Data

Most combustion processes have, in some way or another, a recirculating flow field. This recirculation stabilizes the reaction zone, or flame, but an unnecessarily large recirculation zone can result in high nitrogen oxide (NOx) values for combustion systems. The size of this recirculation zone is crucial to the performance of state-of-the-art, low-emissions hardware. If this is a large-scale combustion process, the flow field will probably be turbulent and, therefore, three-dimensional. This research dealt primarily with flow fields resulting from lean direct injection (LDI) concepts, as described in Research & Technology 2001. LDI is a concept that depends heavily on the design of the swirler. The LDI concept has the potential to reduce NOx values from 50 to 70 percent of current values, with good flame stability characteristics. It is cost effective and (hopefully) beneficial to do most of the design work for an LDI swirler using computer-aided design (CAD) and computer-aided engineering (CAE) tools. Computational fluid dynamics (CFD) codes are CAE tools that can calculate three-dimensional flows in complex geometries. However, CFD codes are only beginning to correctly calculate the flow fields for complex devices, and the related combustion models usually remove a large portion of the flow physics.

Iannetti, Anthony C.↗
DOE OSTI2021

An Experimental and Numerical Investigation to Characterize the Low-Temperature Heat Release in Stoichiometric and Lean Combustion

This work reports on an experimental and modeling study on the low-temperature heat release (LTHR) characteristics for three RON 90 binary blends (n-heptane blended with isooctane, toluene and ethanol) in a Cooperative Fuel Research (CFR) engine at lean and stoichiometric conditions that are representative of homogeneous charge compression ignition (HCCI) and spark-ignition (SI) end-gas combustion conditions, respectively. An analysis of the end-gas temperature-pressure (T-P) trajectories was performed to identify the intake conditions leading to similar T-P trajectories between the two lambdas for each fuel blend. A heat release analysis was then conducted for the identified cases, where fuel-to-fuel differences in LTHR were identified and found to be sensitive to the operating condition. Simulations were conducted for these cases using a recently updated chemical kinetic model and a 0-D engine model, where good qualitative and reasonable quantitative agreements in LTHR were obtained. Sensitivity analysis was also performed directly on the rates of LTHR, to understand the controlling chemical reactions of LTHR, providing further insights into the fuel-to-fuel differences. The results demonstrate the significant promoting effect of n-heptane on LTHR rates, while inhibiting effects were seen for ethanol and toluene. Also highlighted was the importance of H atom abstraction reactions from the chemistry of each fuel component, which could lead to contradictory fuel behavior depending on the locations of the H site of the abstraction reaction due to the different ensuing pathways for the primary fuel radicals.

LTHR, RON 90 binary blends, sensitivity analysis↗
NASA NTRS1984

Research on aviation fuel instability

Current aircraft turbine fuels do not present a significant problem with fuel thermal stability. However, turbine fuels with broadened properties or nonpetroleum derived fuels may have reduced thermal stability because of their higher content of olefins, heteroatoms, and trace metals. Moreover, advanced turbine engines will increase the thermal stress on fuels because of their higher pressure ratios and combustion temperature. In recognition of the importance of this problem, NASA Lewis is currently engaged in a broadly based research effort to better understand the underlying causes of fuel thermal degradation. The progress and status of our various activities in this area are discussed. Topics covered include: nature of fuel instability and its temperature dependence, methods of measuring the instability, chemical mechanisms involved in deposit formation, and instrumental methods for characterizing fuel deposits. Finally, some preliminary thoughts on design approaches for minimizing the effects of lowered thermal stability are briefly discussed.

Baker, C. E.↗
NASA NTRS1992

Nonintrusive spectroscopic techniques for supersonic/hypersonic aerodynamics and combustion diagnostics

This paper presents an overview of the primary nonintrusive diagnostic techniques being developed by the NASA Langley Research Center to address the validation needs of Computational Fluid Dynamic (CFD) codes. The techniques include absorption in the UV and IR, Laser Induced Fluorescence, electron beam fluorescence, and a number of scattering techniques including Rayleigh, spontaneous Raman, and several coherent Raman spectroscopies. Most of the techniques are highly specialized, require complex data interpretation, and can satisfy only a few of the CFD needs. For these reasons, the evolving trend in flowfield diagnostics appears to favor a mode in which the diagnostic researcher, the experimental aerodynamicist, and the CFD community jointly define experiments based on the aeronautical requirements and on available diagnostic techniques.

Exton, R. J.↗
NASA NTRS1998

Annual Research Briefs, 1998

The topics contained in this progress report are direct numerical simulation of turbulent non-premixed combustion with realistic chemistry; LES of non-premixed turbulent reacting flows with conditional source term estimation; measurements of the three-dimensional scalar dissipation rate in gas-phase planar turbulent jets; direct simulation of a jet diffusion flame; on the use of interpolating wavelets in the direct numerical simulation of combustion; on the use of a dynamically adaptive wavelet collocation algorithm in DNS (direct numerical simulation) of non-premixed turbulent combustion; 2D simulations of Hall thrusters; computation of trailing-edge noise at low mach number using LES and acoustic analogy; weakly nonlinear modeling of the early stages of bypass transition; interactions between freestream turbulence and boundary layers; interfaces at the outer boundaries of turbulent motions; largest scales of turbulent wall flows; the instability of streaks in near-wall turbulence; an implementation of the v(sup 2) - f model with application to transonic flows; heat transfer predictions in cavities; a structure-based model with stropholysis effects; modeling a confined swirling coaxial jet; subgrid-scale models based on incremental unknowns for large eddy simulations; subgrid scale modeling taking the numerical error into consideration; towards a near-wall model for LES of a separated diffuser flow; on the feasibility of merging LES with RANS (Reynolds Averaging Numerical simulation) for the near-wall region of attached turbulent flows; large-eddy simulation of a separated boundary layer; numerical study of a channel flow with variable properties; on the construction of high order finite difference schemes on non-uniform meshes with good conservation properties; development of immersed boundary methods for complex geometries; and particle methods for micro and macroscale flow simulations.

Spinks, Debra↗
NASA NTRS2000

Control for NOx Emissions from Combustion Sources

The Environmental Program Office at the Kennedy Space Center is interested in finding solutions and to promote research and development (R&D) that could contribute to solve the problems of air, soil, and groundwater contamination. This study is undertaken as part of NASA's environmental stewardship program. The objective of this study involves the removal of nitrogen oxides from the flue gases of the boilers at KSC using hydrogen peroxide. Phase 1 of this study have shown the potential of this process to be used as an alternative to the current methods of treatment used in the power industry. This report summarizes the research done during the ten-week summer program. During this period, support has been given to implement the modifications suggested for Phase 2 of the project, which focus on oxidation reactions carried at lower temperatures using an ultraviolet source. The redesign and assembly of the modifications for the scrubbing system was the main objective of this research.

PozodeFernandez, Maria E.↗
NASA NTRS2022

An Investigation Into Some Important Aspects of Droplet Breakup/Vaporization Behavior Caused By a Gas Flow (Both Nonreacting & Detonative Combustion) in a Shock Tube

As a part of the rotating detonation engine (RDE) technology enablement project at NASA Glenn Research Center (GRC), an effort was undertaken to extend our current computational capabilities of OpenNCC in some important ways with the implementation of a modeling approach to account for the droplet breakup caused by a shock-induced gas motion, & a vaporization model valid over a wide range of pressure conditions encountered in multiphase detonation. With the modified code, a study was undertaken to investigate the individual droplet behavior followed by the passage of a shock front. The study is carried out by tracking a sparse group of droplets to gain some understanding of shock induced droplet behavior under various shock strengths & fuel injector conditions. The study also looks into the effect of randomization involved in determining the droplet breakup outcomes. Over a wide range of sub-critical conditions examined, larger droplets are observed to undergo significant changes in droplet behavior following their breakup. However, smaller droplets (10 µm or less ) remain unaffected by any shock induced breakup. In a follow-on work, we investigated the impact of shock and droplet interaction in a detonation study involving both gaseous as well as gas/liquid (droplet clouds) fuel/air stoichiometric mixtures in a simple 3D shock-tube configuration. The droplet clouds are made up of different initial droplet sizes of either 6, 10, or 30 µm. We also investigated the individual droplet behavior followed by the passage of a detonation front. The results represent conditions that lead to both overdriven and C-J (ChapmanJouguet) detonations. Under both test conditions, most of the droplet vaporization is completed within a short distance (duration) behind the detonation front & well within the region of complete combustion observed in a corresponding equivalent gas-phase fuel/air mixture. The impact of the shock-induced droplet breakup is found to be significant in the calculations involving the 30-µm droplets. Subsequent to the breakup, the drop sizes vary from 1 to 10 µm. Another factor that contributed to the observed rapid vaporization is the result of vaporization taking place under supercritical conditions. The overall detonation properties of various droplet clouds (made up of different initial sizes) are similar to those observed in a corresponding gaseous fuel/air mixture. In the calculation involving a gaseous fuel, the calculated C-J detonation velocity is 1822 m/s involving Jet-A/air and φ = 1. In the overdriven detonation, it is 2044 m/s. In the calculations involving droplet clouds, the corresponding detonation velocities are lower. The impact of increased droplet size is primarily seen in a higher reduction in the detonation velocity.

shock/droplet interaction↗
NASA NTRS2005

National Combustion Code Used To Study the Hydrogen Injector Design for Gas Turbines

Hydrogen, in the gas state, has been proposed to replace Jet-A (the fuel used for commercial jet engines) as a fuel for gas turbine combustion. For the combustion of hydrogen and oxygen only, water is the only product and the main greenhouse gas, carbon dioxide, is not produced. This is an obvious benefit of using hydrogen as a fuel. The situation is not as simple when air replaces oxygen in the combustion process. (Air is mainly a mixture of oxygen, nitrogen, and argon. Other components comprise a very small part of air and will not be mentioned.) At the high temperatures found in the combustion process, oxygen reacts with nitrogen, and this produces nitrogen oxide compounds, or NOx--the main component of atmospheric smog. The production of NOx depends mainly on two variables: the temperature at which combustion occurs, and the length of time that the products of combustion stay, or reside, in the combustor. Starting from a lean (excess air) air-to-fuel ratio, the goal of this research was to minimize hot zones caused by incomplete premixing and to keep the residence time short while producing a stable flame. The minimization of these two parameters will result in low- NOx hydrogen combustion.

Iannetti, Anthony C.↗