Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 27 for “"Lean-burn"”.
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Multi-fidelity strategies for lean burn combustor design
In combustor design and development, the use of unsteady computational fluid dynamics (CFD) simulations of transient combustor aero-thermo-dynamics to provide an insight into the complex reacting flow-field is expensive in terms of computational time. A large number of such high-fidelity reactive …
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Nanocomposites for nitrogen oxide emissions control in lean-burn engines
(cont.) reducing agent than propane in the SCR of NO. Pt-Rh/CuO/A1₂O₃ nanocomposites capable of adsorbing SO₂ in oxygen-rich environment as metal sulfates and releasing SO₂ in reducing atmosphere were synthesized with sequential precipitation technique. These CuO-based sorbents possessed excellent …
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Combustion optimization in a hydrogen-enhanced lean burn SI engine
Lean operation of spark ignition (SI) automotive engines offers attractive performance incentives. Lowered combustion temperatures inhibit NO[sub]x pollutant formation while reduced manifold throttling minimizes pumping losses, leading to higher efficiency. These benefits are offset by the reduced …
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Knock behavior of a lean-burn hydrogen-enhanced engine concept
Experiments to identify the knock trends of lean gasoline-air mixtures, and such mixtures enhanced with hydrogen (H2) and carbon monoxide (CO), were performed on a single-cylinder research engine with boosting capability. The experimental method used to investigate knock trends consisted of …
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Fundamental studies of flame propagation in lean-burn natural gas engines
<p>Lean-burn natural gas engines offer enhanced thermal efficiencies and reduced soot and NOx emissions. However, cycle-to-cycle variability in combustion that can result from unreliable ignition, variability in equivalence ratio and quenching is a challenge. Reliability of ignition can be improved …
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Predicting the behavior of a lean-burn hydrogen-enhanced engine concept
(cont.) Lean operation of a spark ignition (SI) internal combustion engine (ICE) offers attractive performance incentives. Lowered combustion temperatures inhibit formation of nitrogen oxides (NOx), while reduced intake manifold throttling minimizes pumping losses leading to higher efficiency. …
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Effects of Fuel Split Ratio on NOₓ Emissions of a Lean-burn Staged Combustor
… demand in the near future, aircraft-based lean-burn staged combustion becomes a promising solution in reducing NOₓ emissions. This thesis investigates the effects of a lean-burn staged combustor’s fuel split ratio and staging threshold on the NOₓ emissions for both a sea-level static …
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Lean-burn characteristics of a gasoline engine enriched with hydrogen from a plasmatron fuel reformer
… to a gasoline fueled spark ignition engine the lean limit of the engine can be extended. Lean running engines are inherently more efficient, and have the potential for significantly lower NOx emissions. Hydrogen addition reduces the combustion variability. In this engine concept supplemental …
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Investigation to direct ethanol injection in spark ignition gasoline engines
… timing setting (15 CAD BTDC), knock margin and lean conditions was carried out to assess EDI+GPI’s effectiveness. The impacts of EDI+GPI on engine control parameters, such as start of injection (SOI) timing and spark timing, were also evaluated in order to best match this new fuelling system to …
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Gas engines for domestic engine-driven heat pumps
… on operational and design variables and that a lean, fast-burning combustion process in a slow speed engine coupled with careful control of other operating variables had the potential for improving efficiency, reducing emissions, and lowering frictional losses and noise levels with enhanced …
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Quantification of Velocity at the Sparkplug in a Lab Scale Combustion Chamber
Lean burn has been considered an effective strategy to improve the thermal efficiency of spark-ignition engines. Under lean or diluted conditions, however, the combustion speed is reduced. Therefore, to speed up the combustion, in-cylinder turbulence is induced which may impede the spark …
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The development of ceria-based catalysts for automotive after-treatment applications
… engine technology is being directed towards lean burn operation, involving higher air-fuel ratios in order to improve thermal efficiency. In turn, the operating temperature of modern engines is being reduced, providing less of the heat energy required to activate the catalysts in the …
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Addressing nonlinear combustion instabilities in highly dilute spark ignition engine operation
… engine efficiency, in the form of either lean burn (air dilution) or EGR (inert dilution). High levels of charge dilution, however, lead to cyclic variability that is largely deterministic in nature. The determinism and nonlinear nature of the system indicate that it should be possible to …
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Oxidation catalyst degradation in the exhaust stream of a large bore 2-stroke natural gas engine
Lean burn 2-stroke natural gas engines are commonly used for power generation and gas compression. These engines, however, contribute to air pollution primarily through emissions of carbon monoxide, volatile organic compounds and some unburned hydrocarbons. Oxidation catalysts aid in reducing these …
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Simulation of turbulent flames relevant to spark-ignition engines
… emissions, whilst improving the fuel economy. Burning fuel in excess of air, or lean-burn combustion, is a promising alternative to conventional combustion, and can achieve these requirements simultaneously. However, lean-burn combustion poses new challenges, especially for internal combustion …
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Combustion quality and regimes for standard and alternative fuels
… issue of PM emissions. This study investigated lean-burn GDI combustion of ethanol-gasoline blends in an optical engine and tested a novel injector and combustion chamber design, in order to obtain better atomization and hence better air/fuel mixing, as well as an overall lean air/fuel mixture …
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Active combustion control : modeling, design and implementation
… thermoacoustic instability, which occurs under lean burn conditions close to the flammability where most emissions and efficiency benefits are achieved, and near stoichiometry where often high power density can be realized. This instability is undesirable because the accompanying large pressure …
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Impact of Water Injection on Emissions of Nitrogen Oxides from Aircraft Engines
… combustor is more than those running on lean burn configurations. For shorter range missions under 3000 km, the weight penalty due to carrying the additional water on the airplane is offset by the performance benefit of water injection upstream of the compressors depending on the amount …
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Autoignition and emission characteristics of gaseous fuel direct-injection compression-ignition combustion
… benefits. However, current homogeneous-charge lean-burn engines suffer from impaired efficiency and high unburned fuel emissions. Natural gas direct-injection engines offer the potential of diesel-like efficiencies, but require further research. To improve understanding of the autoignition and …
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Robust Control of Input-Delay Linear Parameter-Varying (LPV) Systems
… Ratio (AFR) control in Spark-Ignition (SI) lean-burn engines and automated Mean Arterial Blood Pressure (MAP) regulation for the clinical resuscitation of hypotensive patients. In our second approach, time-domain techniques are employed to stabilize input-delay LPV systems characterized via …
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