An Experimental Investigation of Advanced Diesel Combustion Strategies for Emissions Reductions in a Heavy-duty Diesel Engine at High Speed and Medium Load PDF Download
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Author: William L. Hardy
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ISBN:
Category :
Languages : en
Pages : 494
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Author: William L. Hardy
Publisher:
ISBN:
Category :
Languages : en
Pages : 494
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Author: Luke R. Staples
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ISBN:
Category :
Languages : en
Pages : 478
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Author: Yong Sun
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ISBN:
Category :
Languages : en
Pages : 234
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Author: Nathaniel Bryce Oliver
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Category :
Languages : en
Pages :
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The expected growth in the heavy-duty transportation sector necessitates the development of engine technologies able to increase efficiency and reduce emissions without sacrificing power output. Previous research has demonstrated that reducing heat transfer losses from the cylinder can enable significant efficiency gains in Diesel engines. The high in-cylinder temperatures generated in this engine architecture enable the use of low-cetane fuels with the potential for low-soot operation. Low soot emissions allow the equivalence ratio to be increased to stoichiometric which increases power, and could allow the existing Diesel aftertreatment system to be replaced with a less-expensive three-way catalyst. Natural gas is a promising candidate for stoichiometric, high-temperature, Diesel-style combustion. Its high hydrogen-to-carbon ratio should be able to reduce both soot and carbon dioxide emissions, and its wide distribution as a commercial and residential fuel provides existing infrastructure to speed deployment in transportation applications. This thesis demonstrates stoichiometric, Diesel-style combustion of neat methane as a single-component surrogate for natural gas. It explores the challenges of injecting a gaseous fuel at high pressures, and demonstrates the fuel's capacity for low emissions. It then provides a preliminary investigation into multiple-injection strategies for controlling combustion behavior and emissions in a stoichiometric, high-temperature engine architecture. First, fuel system hardware is developed to enable gaseous operation and preliminary experimentation is accomplished with methane. A fuel compression system is designed to supply methane at pressures suitably high to achieve good mixing and short injection durations, and a solenoid-actuated Diesel fuel injector is modeled and modified to inject methane at these pressures. This fuel injection system is then implemented on a single-cylinder engine. An insulated piston face, air cooled head, and intake preheating achieve suitable start of injection temperatures to ignite methane. Intake preheating is varied at low equivalence ratios to determine the sensitivity of engine performance to temperature at the lowest-load, lowest-temperature conditions of interest. A sweep of equivalence ratio demonstrates soot emissions roughly four times the current EPA limit for heavy-duty vehicles and combustion efficiencies of approximately 92% at stoichiometric fuel loading. High soot levels and low combustion efficiencies are also seen at the lowest equivalence ratios investigated. This suggests poorly mixed combustion, and poor injector performance. Second, injector dynamics are examined in greater detailed, and emissions performance is characterized with improved injector performance. High-speed Schlieren imaging is able to determine the injection dynamics contributing to high low-load emissions. A parametric modeling investigation suggests that reducing the injector plunger length is able to remove flow rate oscillations seen at long injection durations, and that the addition of dry friction is able to reduce the magnitude of low-momentum post injections occurring after injector closing. Dry friction is implemented using PTFE O-rings installed between the injector body and plunger. Imaging is used to confirm that a shortened plunger is able to remove long-duration oscillations, and to determine the number of O-rings necessary to suitably reduce post injection magnitude. The improved injector is used to repeat the sweep of equivalence ratios and demonstrates improved soot emissions at all operating conditions. Most notably, low-load soot emissions are reduced by more than a factor of ten, demonstrating the effectiveness of improved injector performance for improving emissions. Techniques for further improving injector performance and potential changes to injector design are discussed. Finally, the prospects for controlling combustion in a stoichiometric, low heat rejection Diesel engine using multiple injections are discussed and experimentally investigated. The applications and effects of multiple injection strategies in traditional Diesel engines are explored, and their potential extension to stoichiometric engines is discussed. Methanol engine operation enables the use of a fast-actuating piezoinjector and the realization of short injection pulses. A range of two-injection strategies are implemented in order to determine the sensitivity of engine operation to pilot, split-main, and post-injection timing and duration. Small pilot injections are found to have control authority over rate of pressure rise and peak pressure and show some promise for improving combustion efficiency. Post injections demonstrate authority over peak pressure and combustion efficiency. All of these effects are accomplished with minimal impact on engine work output. The experiments of this thesis demonstrate that, even with course control of injection, high-temperature, stoichiometric combustion of methane is able to greatly reduce soot emissions over traditional Diesel engines. Improved injector dynamics and the implementation of multiple injection strategies further improve emissions and combustion performance, suggesting substantial room for refinement of the technology and motivating the continued development of injector hardware and injection strategies. The ability to operate a Diesel engine at stoichiometric fueled only by natural gas and to employ a three-way catalyst for emissions abatement makes this strategy a clean, efficient, high-torque, and low-cost solution for heavy-duty transportation.
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Languages : en
Pages :
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The goal of the present technology development was to increase the efficiency of internal combustion engines while minimizing the energy penalty of meeting emissions regulations. This objective was achieved through experimentation and the development of advanced combustion regimes and emission control strategies, coupled with advanced petroleum and non-petroleum fuel formulations. To meet the goals of the project, it was necessary to improve the efficiency of expansion work extraction, and this required optimized combustion phasing and minimized in-cylinder heat transfer losses. To minimize fuel used for diesel particulate filter (DPF) regeneration, soot emissions were also minimized. Because of the complex nature of optimizing production engines for real-world variations in fuels, temperatures and pressures, the project applied high-fidelity computing and high-resolution engine experiments synergistically to create and apply advanced tools (i.e., fast, accurate predictive models) developed for low-emission, fuel-efficient engine designs. The companion experiments were conducted using representative single- and multi-cylinder automotive and truck diesel engines.
Author: Bing Hu
Publisher:
ISBN:
Category :
Languages : en
Pages : 140
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Author: Rahul Jhavar
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Category :
Languages : en
Pages : 154
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Author: Alexander Knafl
Publisher:
ISBN: 9783836465755
Category : Technology & Engineering
Languages : en
Pages : 164
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The development of low-temperature premixed compression ignition (PCI) combustion strategies and the performance of diesel oxidation catalysts (DOe are presented in this work. At moderate loads, low-temperature PCI combustion is shown to significantly reduce engine-out oxides of nitrogen (NOX) and soot emissions compared to a conventional diesel combustion strategy. The PCI load-range is limited by soot emissions at high engine loads and excessive carbon monoxide (CO), hydrocarbon (He emissions and low exhaust gas temperatures low engine loads. DOC formulations are investigated on a gas bench reactor using surrogate exhaust gas mixtures containing CO, O2, H2O, n1H24, C2H4 and N2. Light-off tests show delayed catalyst light-off in the presence of PCI exhaust. CO and HC are converted to 100% and 98% respectively under fully lit conditions. Engine experiments agree well with reactor experiments. DOC formulations containing zeolites adsorb HC at low temperatures. HC speciation shows that HCs of carbon number five and higher are trapped on zeolite at low temperatures. CO conversion is 100% through the fully active catalyst; HC conversion is lower compared to the reactor experiments.
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Languages : en
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Abstract : Among the various alternative fuels, natural gas is considered as a leading candidate for heavy-duty applications due to its availability and applicability in conventional internal combustion diesel engines. Compared to their diesel counterparts natural gas fueled spark-ignited engines have a lower power density, reduced low-end torque capability, limited altitude performance, and ammonia emissions downstream of the three-way catalyst. The dual fuel diesel/natural gas engine does not suffer with the performance limitations of the spark-ignited concept due to the flexibility of switching between different fueling modes. Considerable research has already been conducted to understand the combustion behavior of dual fuel diesel/natural gas engines. As reported by most researchers, the major difficulty with dual fuel operation is the challenge of providing high levels of natural gas substitution, especially at low and medium loads. In this study extensive experimental and simulation studies were conducted to understand the combustion behavior of a heavy-duty diesel engine when operated with compressed natural gas (CNG) in a dual fuel regime. In one of the experimental studies, conducted on a 13 liter heavy-duty six cylinder diesel engine with a compression ratio of 16.7:1, it was found that at part loads high levels of CNG substitution could be achieved along with very low NOx and PM emissions by applying reactivity controlled compression ignition (RCCI) combustion. When compared to the diesel-only baseline, a 75% reduction in both NOx and PM emissions was observed at a 5 bar BMEP load point along with comparable fuel consumption values. Further experimental studies conducted on the 13 liter heavy-duty six cylinder diesel engine have shown that RCCI combustion targeting low NOx emissions becomes progressively difficult to control as the load is increased at a given speed or the speed is reduced at a given load. To overcome these challenges a number of simulation studies were conducted to quantify the in-cylinder conditions that are needed at high loads and low to medium engine speeds to effectively control low NOx RCCI combustion. A number of design parameters were analyzed in this study including exhaust gas recirculation (EGR) rate, CNG substitution, injection strategy, fuel injection pressure, fuel spray angle and compression ratio. The study revealed that lowering the compression ratio was very effective in controlling low NOx RCCI combustion. By lowering the base compression ratio by 4 points, to 12.7:1, a low NOx RCCI combustion was achieved at both 12 bar and 20 bar BMEP load points. The NOx emissions were reduced by 75% at 12 bar BMEP while fuel consumption was improved by 5.5%. For the 20 BMEP case, a 2% improvement in fuel consumption was achieved with an 87.5% reduction in NOx emissions. At both load points low PM emissions were observed with RCCI combustion. A low NOx RCCI combustion system has multiple advantages over other combustion approaches, these include; significantly lower NOx and PM emission which allows a reduction in aftertreatment cost and packaging requirements along with application of higher CNG substitution rates resulting in reduced CO2 emissions.
Author: Ryan Michael Nevin
Publisher:
ISBN:
Category :
Languages : en
Pages : 470
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