Characterization of the Effects of Ducted Fuel Injection in a Compression Ignition Engine PDF Download
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Author: Christopher William Nilsen
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Category :
Languages : en
Pages : 0
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Ducted fuel injection (DFI) has been proposed as a strategy to enhance the fuel/charge-gas mixing within the combustion chamber of a direct-injection mixing-controlled compression-ignition engine. The concept involves injecting each fuel spray through a small tube within the combustion chamber to facilitate the creation of a leaner mixture in the autoignition zone, relative to a conventional free-spray configuration (i.e., a fuel spray that is not surrounded by a duct). This dissertation investigates the effects of ducted fuel injection on engine-out emissions and efficiency with two-orifice and four-orifice injector tips across a wide range of conditions. A numerical study contributes to the understanding of the fluid flow effects of DFI. The experiments in chapter two use a two-orifice fuel injector to test two duct configurations relative to conventional diesel combustion. The result is that DFI is confirmed to be effective at curtailing engine-out soot emissions. It also breaks the tradeoff between emissions of soot and nitrogen oxides (NO[subscript x]) by simultaneously attenuating soot and NO[subscript x] with increasing dilution. The third chapter expands on the second by comparing ducted fuel injection to conventional diesel combustion over a wide range of operating conditions and at higher loads (up to 8.7 bar gross indicated mean effective pressure) with a four-orifice fuel injector. This chapter is achieved through sweeps of intake-oxygen mole-fraction, injection duration, intake pressure, start of combustion timing, fuel-injection pressure, and intake temperature. Ducted fuel injection is shown to curtail engine-out soot emissions at all tested conditions. Under certain conditions, ducted fuel injection can attenuate engine-out soot by over a factor of 100. In addition to producing significantly lower engine-out soot emissions, ducted fuel injection enables the engine to be operated at low-NO[subscript x] conditions that are not feasible with conventional diesel combustion due to high soot emissions. The fourth chapter explores 1.1 bar IMEP[subscript g] (low load) conditions and 10 bar IMEP[subscript g] (higher-load) conditions with the same four-orifice fuel injector as in chapter three. DFI and CDC are directly compared at each operating point in the study. At the idle condition, the intake dilution was swept to elucidate the soot and NO[subscript x] performance of DFI in this new load range. This expands the range of conditions over which DFI has been shown to attenuate soot formation. It also shows that DFI enables low-NO[subscript x], low-load operation that is not achievable with CDC due to excessive soot formation at high dilution levels. The fifth chapter uses a numerical model to develop the understanding of the fluid flow effects of DFI. This enabled studies of entrainment and mixing that would have been much more challenging to do in an experiment. This showed that DFI enhances charge gas entrainment before the duct and blocks entrainment inside of the duct. Mixing is enhanced by the duct, which resulted in lower peak equivalence ratios at the end of the duct.
Author: Christopher William Nilsen
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Ducted fuel injection (DFI) has been proposed as a strategy to enhance the fuel/charge-gas mixing within the combustion chamber of a direct-injection mixing-controlled compression-ignition engine. The concept involves injecting each fuel spray through a small tube within the combustion chamber to facilitate the creation of a leaner mixture in the autoignition zone, relative to a conventional free-spray configuration (i.e., a fuel spray that is not surrounded by a duct). This dissertation investigates the effects of ducted fuel injection on engine-out emissions and efficiency with two-orifice and four-orifice injector tips across a wide range of conditions. A numerical study contributes to the understanding of the fluid flow effects of DFI. The experiments in chapter two use a two-orifice fuel injector to test two duct configurations relative to conventional diesel combustion. The result is that DFI is confirmed to be effective at curtailing engine-out soot emissions. It also breaks the tradeoff between emissions of soot and nitrogen oxides (NO[subscript x]) by simultaneously attenuating soot and NO[subscript x] with increasing dilution. The third chapter expands on the second by comparing ducted fuel injection to conventional diesel combustion over a wide range of operating conditions and at higher loads (up to 8.7 bar gross indicated mean effective pressure) with a four-orifice fuel injector. This chapter is achieved through sweeps of intake-oxygen mole-fraction, injection duration, intake pressure, start of combustion timing, fuel-injection pressure, and intake temperature. Ducted fuel injection is shown to curtail engine-out soot emissions at all tested conditions. Under certain conditions, ducted fuel injection can attenuate engine-out soot by over a factor of 100. In addition to producing significantly lower engine-out soot emissions, ducted fuel injection enables the engine to be operated at low-NO[subscript x] conditions that are not feasible with conventional diesel combustion due to high soot emissions. The fourth chapter explores 1.1 bar IMEP[subscript g] (low load) conditions and 10 bar IMEP[subscript g] (higher-load) conditions with the same four-orifice fuel injector as in chapter three. DFI and CDC are directly compared at each operating point in the study. At the idle condition, the intake dilution was swept to elucidate the soot and NO[subscript x] performance of DFI in this new load range. This expands the range of conditions over which DFI has been shown to attenuate soot formation. It also shows that DFI enables low-NO[subscript x], low-load operation that is not achievable with CDC due to excessive soot formation at high dilution levels. The fifth chapter uses a numerical model to develop the understanding of the fluid flow effects of DFI. This enabled studies of entrainment and mixing that would have been much more challenging to do in an experiment. This showed that DFI enhances charge gas entrainment before the duct and blocks entrainment inside of the duct. Mixing is enhanced by the duct, which resulted in lower peak equivalence ratios at the end of the duct.
Author: Cory Andrew Adams
Publisher:
ISBN:
Category :
Languages : en
Pages : 188
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Varying the fuel stratification during gasoline compression ignition (GCI) combustion has been shown to impact important combustion parameters and emissions. The effect of varied injection pressure and injection timing on the fuel stratification and formation of nitric oxide (NOx) emissions was studied at two engine operating conditions. At a 1500 revolutions per minute (rpm) engine condition, a 100 bar increase in injection pressure required a 1.4o crankangle retard of the injection timing to maintain constant NOx emissions. The required injection timing shift to maintain constant NOx emissions at a 1900 rpm condition for a 100 bar increase in injection pressure was 2.5o crankangle. A skip-firing injection strategy illustrated the importance of the second injection in creating fuel stratification and promoting ignition for GCI combustion. The effects of injected fuel mass variability on combustion stability were investigated using a randomized injection strategy. Analysis showed that the injected fuel mass uncertainty required to induce combustion instability was between 3.2-4.8%. Three-dimensional computational fluid dynamics (CFD) and a one-dimensional (1-D) turbulent jet model were used to analyze the fuel-air mixing. A quasi-steady jet timescale was used to non-dimesionalize the time after start of injection. The ability of the timescale to collapse the jet vapor penetration and fuel-mass-weighted PDF of mixture fraction/equivalence ratio were evaluated for a variety of conditions at times significantly after end of injection. The quasi-steady jet timescale reasonably collapsed jet vapor penetration for various injection pressures but did not collapse the fuel-mass-weighted PDFs of equivalence ratio at times of interest during transient changes to the ambient gas density unless changes in spray spreading angle are accounted for. The 1-D jet model was benchmarked to CFD and evaluated at different conditions to analyze the assumptions of the 1-D model. A sensitivity analysis of the 1-D model was conducted. The 3-D CFD results are utilized to analyze the connection between the fuel-air distribution and the engine-out NOx emissions at the constant-NOx engine operating conditions. Computational fluid dynamics results showed similar equivalence ratio distributions resulted in relatively constant NOx emissions.
Author: Hongsheng Guo
Publisher: Frontiers Media SA
ISBN: 2889666212
Category : Technology & Engineering
Languages : en
Pages : 125
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Category :
Languages : en
Pages :
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Abstract : The characteristics of gasoline sprayed directly into combustion chambers are of critical importance to engine out emissions and combustion system development. The optimization of the spray characteristics to match the in-cylinder flow field, chamber geometry, and spark location are vital tasks during the development of an engine combustion strategy. Furthermore, the presence of liquid fuel during combustion in Spark-Ignition (SI) engines causes increased hydrocarbon (HC) emissions [1]. Euro 6, LEVIII, and US Tier 3 emissions regulations reduce the allowable particulate mass significantly from the previous standards. LEVIII standards reduce the acceptable particulate emission to 1 mg/mile [2]. A good Direct Injection Spark Ignited (DISI) strategy vaporizes the correct amount of fuel at the proper point in the engine cycle with the proper in-cylinder air flow for optimal power output with minimal emissions. The opening and closing phases of DISI injectors is crucial to this task as the spray produces larger droplets during both theses phases. This work focuses on the results from a novel method to investigate fuel behavior upon closing of the fuel injector. A Design of Experiments (DOE) was used to determine the effect of pressure, temperature, and pulse-width of the fuel spray after the closing event. Experiments determined that the primary source of controlling the droplet size and the mass post injector closing for a given injector was the temperature. It was found that the end of injection behavior is a highly dynamic, complex event including, but not limited to, effects from the injector design, deposit concentration, and fuel type.
Author:
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Category :
Languages : en
Pages : 10
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Author: John Storey
Publisher:
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Category :
Languages : en
Pages : 11
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Author:
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Category :
Languages : en
Pages :
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Natural gas has a high auto-ignition temperature, therefore natural gas engines use an ignition source to promote combustion. The high-pressure direction-injection (HPDI) systems available use small diesel injections prior to the main gas injection. A new series of HPDI injectors have been developed that inject diesel and gas simultaneously through the same holes. In order to understand and control injection and combustion behavior in an engine, it is essential to understand how injection mass is related to the diesel/gas ratio and injection command parameters. Three prototype injectors are examined. "Prototype B" most closely resembles a standard J36 HPDI injector, but has a modified diesel needle that injects diesel internally into a common diesel/gas reservoir. Prototypes "CS & CSX" have the diesel needle eliminated and replaced with a flow restrictor. The pressure difference between the diesel and the gas controls the quantity of diesel injected. A single pulse width (GPW) for the gas needle controls the fuel quantities. An injection visualization chamber (IVC) was developed for flow measurements and optical characterization of injections into a chamber at pressures up to 80 bar. Diesel and natural gas are replaced by VISCOR® and nitrogen to study non-reacting flows. A novel feature of the IVC is a retracting shroud that allows the injector to reach steady-state prior to imaging. For low commanded injection duration (GPW less than 0.60 ms), the relation between GPW and injected mass is non-linear, for all injectors tested. For gas pulse widths greater than 0.65 ms the Co-injectors exhibit approximately linear behavior with higher diesel fuelling quantities lowering gas flow quantities. All Co-injectors are compared to baseline gas flow quantities of a standard J36 to show design difference effects on flow quantities. The sensitivity of gas flow to diesel in injection quantities, as well as the discharge coefficient are computed and theoretically modeled for each.
Author:
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ISBN:
Category : Combustion
Languages : en
Pages :
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The goal of this study is to assess conventional and low temperature dual fuel combustion in light- and heavy-duty multi-cylinder compression ignition engines in terms of combustion characterization, performance, and emissions. First, a light-duty compression ignition engine is converted to a dual fuel engine and instrumented for in-cylinder pressure measurements. The primary fuels, methane and propane, are each introduced into the system by means of fumigation before the turbocharger, ensuring the air-fuel composition is well-mixed. Experiments are performed at 2.5, 5, 7.5, and 10 bar BMEP at an engine speed of 1800 RPM. Heat release analyses reveal that the ignition delay and subsequent combustion processes are dependent on the primary fuel type and concentration, pilot quantity, and loading condition. At low load, diesel-ignited propane yields longer ignition delay periods than diesel-ignited methane, while at high load the reactivity of propane is more pronounced, leading to shorter ignition delays. At high load (BMEP = 10 bar), the rapid heat release associated with diesel-ignited propane appears to occur even before pilot injection, possibly indicating auto-ignition of the propane-air mixture. Next, a modern, heavy-duty compression ignition engine is commissioned with an open architecture controller and instrumented for in-cylinder pressure measurements. Initial diesel-ignited propane dual fuel experiments (fumigated before the turbocharger) at 1500 RPM reveal that the maximum percent energy substitution (PES) of propane is limited to 86, 60, 33, and 25 percent at 5, 10, 15, and 20 bar BMEP, respectively. Fueling strategy, injection strategy, exhaust gas recirculation (EGR) rate, and intake boost pressure are varied in order to maximize the PES of propane at 10 bar BMEP, which increases from 60 PES to 80 PES of propane. Finally, diesel-ignited propane dual fuel low temperature combustion (LTC) is implemented using early injection timings (50 DBTDC) at 5 bar BMEP. A sweep of injection timings from 10 DBTDC to 50 DBTDC reveals the transition from conventional to low temperature dual fuel combustion, indicated by ultra-low NOx̳ and smoke emissions. Optimization of the dual fuel LTC concept yields less than 0.02 g/kW-hr NOx̳ and 0.06 FSN smoke at 93 PES of propane.
Author: John Andrew Roberts
Publisher:
ISBN:
Category :
Languages : en
Pages : 193
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Gasoline compression ignition (GCI) combustion is a promising solution to address increasingly stringent efficiency and emissions regulations imposed on the internal combustion engine. However, the high resistance to auto-ignition of modern market gasoline makes low load compression ignition operation difficult. The most comprehensive work focused on low load GCI operation has been performed on multi-cylinder research engines where it is difficult to decouple effects of the combustion event from air-handling and system level parameters (e.g., intake pressurization and exhaust gas recirculation (EGR)). Further, most research has focused on technology applications (e.g., use of variable valve actuation or supercharging) rather than fundamental effects, making identification of influential factors difficult. Accordingly, there is a need for detailed investigations focused on isolating the critical parameters that can be used to enable low load GCI operation. A full factorial parametric study was completed to isolate the effects of intake temperature, EGR rate, and fuel reactivity on low load performance. A minimum intake pressure metric was used to compare these parameters. This allowed combustion phasing and load to be held constant while isolating the experiment from fuel injection effects. The effort showed that increasing intake temperature yields a linear reduction in the minimum intake pressure required for stable operation. Adding a small amount of diesel fuel to gasoline improved combustion stability with minimal need for energy addition through intake pressurization. The minimum intake pressure requirement also showed very good correlation with the measured research octane number of the fuel. However, increasing the fuel reactivity with diesel fuel, caused NOx emissions to increase. Response model analysis was used to determine the intake conditions required to maintain NOx levels that may not require lean NOx after treatment. The combination of diesel fuel blending and EGR allowed NOx levels to be reduced to near zero values with the minimum intake pressurization required. A detailed investigation into the effects of EGR showed that, for a given fuel, there is a maximum EGR rate that allows for stable operation, which effectively constrains the minimum NOx prior to aftertreatment. Accordingly, a method that enables the variation of the fuel reactivity on demand is an ideal solution to address low load stability issues. Metal engine experiments conducted on a single cylinder medium-duty research engine allowed for the investigation of this strategy. The fuels used for this study were 87 octane gasoline (primary fuel stream) and diesel fuel (reactivity enhancer). Initial tests demonstrated load extension down to idle conditions with only 20% diesel by mass, which reduced to 0% at loads above 3 bar indicated mean effective pressure (IMEPg). Engine performance over a mode weighted drive cycle was completed based on work by the Ad-Hoc fuels committee [1] to demonstrate the performance of various levels of fuel blending for five primary modes of operation encompassing low load to high load. Lastly, several simulated transient drive cycle were analyzed to investigate the consumption rate of the reactivity enhancer. A response model was fit to the experimental data and exercised over the load based drive cycle. Results showed that the diesel consumption could be reduced to additive levels over a 10k mile oil change interval, lower than typical diesel exhaust fluid (DEF) consumption levels, which presents a pathway to a full-time GCI engine. Experimental efforts used a minimum intake pressure metric to evaluate the auto-ignition quality of seven fuels, including two pump fuels and five FACE gasolines in a GCI engine. The results showed that research octane number (RON) trends well with the intake pressure required to achieve a desired ignition delay at low-temperature conditions, which are representative of a boosted GCI engine. At higher temperature intake conditions poor correlation is observed between RON and intake pressure requirement. Effects of octane sensitivity were dominated by the general reactivity of fuel as characterized by RON. The Octane Index and K-factors were regressed for each operating condition, and good correlation was seen between the Octane Index and the intake pressure requirement. Main effects analysis of the impact of general properties of the fuel (RON, motor octane number (MON), and sensitivity (S)) on the intake pressure requirement showed that RON was the only statistically significant parameter. Analysis of the main effects of fuel composition on intake pressure requirement showed some trends, but none were statistically significant. This indicates that the auto-ignition quality of the fuel is not characterized by variations in any single species. Analysis of the stable start-of-injection (SOI) timing injection window showed that both RON and sensitivity describe stability at low temperatures. In general, a fuel with a higher RON will have a smaller stable SOI window than a lower RON fuel. Additionally, fuels with the same RON and different sensitivities will behave differently. Analysis showed that, for a given RON, a low sensitivity fuel would tend to have a wider operating window than a high sensitivity fuel. Analysis of the heat release for the experimental cases showed that this is due to the presence of low-temperature chemistry. Fuels that suppress low-temperature chemistry did not show low-temperature heat release (LTHR) and had a narrower stability window. At high temperatures, LTHR was suppressed for all fuels, as the temperature in the jet exceeded the ceiling temperature for low-temperature oxidation.
Author: Krishna Mohan Singh
Publisher: Springer Nature
ISBN: 9819971772
Category :
Languages : en
Pages : 931
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