WO2011053819A2 - Composition and method for reducing nox and smoke emissions from diesel engines at minimum fuel consumption - Google Patents
Composition and method for reducing nox and smoke emissions from diesel engines at minimum fuel consumption Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L1/00—Liquid carbonaceous fuels
- C10L1/04—Liquid carbonaceous fuels essentially based on blends of hydrocarbons
- C10L1/08—Liquid carbonaceous fuels essentially based on blends of hydrocarbons for compression ignition
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
- F02D19/0602—Control of components of the fuel supply system
- F02D19/0607—Control of components of the fuel supply system to adjust the fuel mass or volume flow
- F02D19/061—Control of components of the fuel supply system to adjust the fuel mass or volume flow by controlling fuel injectors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
- F02D19/0639—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels
- F02D19/0649—Liquid fuels having different boiling temperatures, volatilities, densities, viscosities, cetane or octane numbers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
- F02D19/08—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed simultaneously using pluralities of fuels
- F02D19/082—Premixed fuels, i.e. emulsions or blends
- F02D19/085—Control based on the fuel type or composition
- F02D19/087—Control based on the fuel type or composition with determination of densities, viscosities, composition, concentration or mixture ratios of fuels
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
- F02M2200/95—Fuel injection apparatus operating on particular fuels, e.g. biodiesel, ethanol, mixed fuels
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
- F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
- F02M26/23—Layout, e.g. schematics
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M31/00—Apparatus for thermally treating combustion-air, fuel, or fuel-air mixture
- F02M31/02—Apparatus for thermally treating combustion-air, fuel, or fuel-air mixture for heating
- F02M31/12—Apparatus for thermally treating combustion-air, fuel, or fuel-air mixture for heating electrically
- F02M31/13—Combustion air
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/30—Use of alternative fuels, e.g. biofuels
Definitions
- the present invention relates generally to diesel fuels and engine performance and, more particularly, to a composition and method for reducing NOx and smoke emissions from diesel engines at minimum fuel consumption.
- NOx nitrogen oxides
- the present invention is directed to a method for reducing NOx and smoke emissions from a diesel engine at minimum fuel consumption comprising: (a) determining a cetane number for at least one diesel fuel or blending component for a diesel fuel; (b) determining the temperature for distillation of 50 percent (T50) and optionally the slope (which is defined as the difference obtained by subtracting the temperature for distillation of 10 percent of the fuel or blending component (T10) from the temperature for distillation of 90 percent of the fuel or blending component (T90)) of the distillation curve for each aforesaid fuel or blending component; (c) setting a value for each independent engine control for the aforesaid diesel engine by: (i) establishing a number of fuel property inputs, the fuel property inputs each being representative of at least one of a distillation temperature of each fuel, a cetane number of each fuel, and a distillation slope for each fuel; (ii) establishing a number of engine performance inputs, the engine performance inputs each corresponding to
- the present invention provides a diesel fuel composition for reducing NOx and smoke emissions from a diesel engine at minimum fuel consumption comprising: at least one diesel fuel or blending component for a diesel fuel having a combination of a low T50 in the range of from 190°C to 280°C, a high cetane number in the range of from 31 to 60, and optionally a high distillation curve slope in the range of from 58°C to 140°C, which combination is effective to produce a combination of the lowest NO x and smoke emissions at the lowest fuel consumption at independent engine control values for the diesel engine that are optimum to afford production of a combination of the lowest NO x and smoke emissions at the lowest fuel consumption.
- the present invention provides a method for reducing NOx and smoke emissions from a diesel engine at minimum fuel consumption, comprising the step of adding to the diesel engine at least one diesel fuel or blending component for a diesel fuel having a combination of a low T50 in the range of from 190°C to 280°C and a high cetane number in the range of from 31 to 60, which combination is effective to afford a combination of the lowest NO x and smoke emissions at the lowest fuel consumption at independent engine control values for the diesel engine that are optimum to afford production of a combination of the lowest NO x and smoke emissions at the lowest fuel consumption, whereby the NOx and smoke emissions from the diesel engine are reduced by at least 10% and 15%, respectively.
- Figure 1 contains plots of the distillation curves for the various fuels that were used to develop models for selection of an ideal fuel.
- Figure 2 is a plot of the correlations of the estimated values of the normalized fuel specific NO x versus the measured data.
- Figure 3 is a plot of the correlations of the estimated values of the normalized smoke emissions versus the measured data.
- Figure 4 is a plot of the correlations of the estimated values of the normalized gross indicated specific fuel consumption versus the measured data.
- Figure 5 is a plot of the correlations of the estimated values of the normalized peak cylinder pressure versus the measured data.
- Figure 6 is a plot of the correlations of the estimated values of the normalized crank angle for 50 percent cumulative heat release versus the measured data.
- Figure 7 is a plot of the ratio of the estimated model coefficient to the standard error for each independent engine control and fuel property with regard to its effect on the normalized fuel specific NO x emission.
- Figure 8 is a plot of the ratio of the estimated model coefficient to the standard error for each independent engine control and fuel property with regard to its effect on the normalized smoke emission.
- Figure 9 is a plot of the ratio of the estimated model coefficient to the standard error for each independent engine control and fuel property with regard to its effect on the normalized gross indicated fuel specific consumption.
- Figure 10 is a plot of the ratio of the estimated model coefficient to the standard error for each independent engine control and fuel property with regard to its effect on the normalized peak cylinder pressure.
- Figure 11 is a plot of the ratio of the estimated model coefficient to the standard error for each independent engine control and fuel property with regard to its effect on the normalized crank angle for 50 percent cumulative heat release.
- Figure 12 is a plot of the normalized fuel gisfc versus the normalized fs NO x for two fuels with regard to the effect of fuel properties and engine controls on the NO x -/gisfc tradeoff.
- Figure 13 is a contour plot of the normalized fuel specific NO x emissions (on the Z axis) as a function of T50 and intake side oxygen concentration (on the Y and X axes, respectively).
- Figure 14 is a contour plot of the normalized fuel specific NO x emission (on the Z axis) as a function of T50 and cetane number (on the Y and X axes, respectively).
- Figure 15 is a contour plot of the normalized smoke (on the Z axis) as a function of T50 and intake side oxygen concentration (on the Y and X axes, respectively).
- Figure 16 is a contour plot of the normalized smoke (on the Z axis) as a function of T50 and slope of the distillation curve (on the Y and X axes, respectively).
- Figure 17 is a contour plot of the normalized gross indicated specific fuel consumption (on the Z axis) as a function of cetane number and air-fuel ratio (on the Y and X axes, respectively).
- a refinery In order to meet common fuel specifications such as volatility and cetane number, a refinery must blend a number of refinery stocks derived from various units in the refinery. For example, at a grossly simplified level, the primary means of modifying the boiling point curve is through the addition of polyaromatic stocks, while the primary means of modifying cetane is the addition of mono- or poly-aromatics and the use of a cetane improver.
- fuel chemistry can be significantly altered in meeting fuel specifications. Additionally, fuel specifications are seldom changed in isolation, and the drive to meet one specification of one property may have a deleterious effect on other specified properties. Blending fuels is a complex science, and it is seldom possible to alter individual properties without also altering other properties.
- the present invention involves the influence of diesel fuel properties on the combustion and emissions performance of diesel engines, in particular, light-duty diesel engines operating at ultra-low NO x levels. Furthermore, the present invention differentiates the effect of fuel properties and engine controls, and separates out the individual contribution of fuel volatility, ignition quality and the dispersion in the distillation temperature range (which is represented by the slope, as defined hereinabove, of the distillation curve), and demonstrates that NO x and smoke emissions are impacted by the mid-distillation temperature and cetane number. It should also be noted that, in the practice of the present invention, emissions of unburnt hydrocarbons and carbon monoxide are below legislated emissions limits.
- the regression-based multivariate models developed to determine the functional relationships between engine outputs and fuels and engine control levers in the present invention indicate that lower mid-distillation temperatures that were achieved by a reduction in the poly- aromatic content of the fuel provides significant reduction of NO x and smoke emissions.
- Increasing cetane member, which correlates with lowering mono-aromatic content, provides a small benefit of a reduction of NO x emissions.
- the present invention also demonstrates that the effect of fuel properties on select heat release characteristics such as peak cylinder pressure ("pep") and on combustion phasing is not significant from the regression models.
- pep peak cylinder pressure
- the simultaneous selection of fuel property values and engine control settings to afford the best combination of NO x emissions and fuel consumption tradeoff in the present invention indicates significant fuel consumption and NO x emission improvements to the extent of approximately 7 percent and 20 percent, respectively, from that for the baseline ULSD.
- the present invention is directed to a method for reducing NOx and smoke emissions from a diesel engine at minimum fuel consumption, comprising: (a) determining an ignition property such as a cetane number in accordance with ASTM method D613 or alternate measures of ignition quality, such as a derived cetane number by ASTM methods D6890 or D7170 or a calculated cetane index by ASTM methods D976 or D4737, which are calculated from distillation and density properties of the fuel, all of which ignition properties will be denoted as "cetane number" for this description for at least one diesel fuel or blending component for a diesel fuel; (b) determining the T50, and optionally the slope of the distillation curve for each fuel or blending component, for example by ASTM method D86; (c) setting a value for each of the following independent engine controls for the diesel engine by (i) establishing a number of fuel property inputs, the fuel property inputs each being representative of at least one of a distillation temperature of each fuel, a cetane number of each
- the present invention is also directed to a diesel fuel composition for reducing NOx and smoke emissions from a diesel engine at minimum fuel consumption, comprising: at least one diesel fuel or blending component for a diesel fuel having a combination of a low T50 in the range of from 190°C to 280°C, preferably 190°C to 255°C; a high cetane number in the range of from 31 to 60, preferably from 40 to 60; and optionally a high distillation curve slope in the range of from 58°C to 140°C, preferably from 80°C to 140°C, which combination is effective to produce a combination of the lowest NO x and smoke emissions at the lowest fuel consumption at independent engine control values for the diesel engine that are optimum to afford production of a combination of the lowest NO x and smoke emissions at the lowest fuel consumption.
- the independent engine control values for the diesel engine are set by: (i) establishing a number of fuel property inputs, the fuel property inputs each being representative of at least one of a distillation temperature of each fuel, a cetane number of each fuel, and a distillation slope for each fuel; (ii) establishing a number of engine performance inputs, the engine performance inputs each corresponding to at least one of: fuel amount per cylinder, fuel timing, a ratio between fuel and air, a fuel pressure, a gas temperature, a gas pressure, an EGR flow, oxygen content of an engine gas flow, engine speed, and engine load; (iii) generating engine control information as a function of the fuel property inputs and the engine performance inputs; and (iv) accessing the engine control information to regulate the engine controls to afford production of a combination of the lowest NOx and smoke emissions at the lowest fuel consumption, such that NOx and smoke emissions from the diesel engine are reduced by at least 10% and 15 %, respectively.
- the present invention also provides a method for reducing NOx and smoke emissions from a diesel engine at minimum fuel consumption, comprising the step of adding to the diesel engine at least one diesel fuel or blending component for a diesel fuel having a combination of a low T50 in the range of from 190°C to 280°C and a high cetane number in the range of from 31 to 60, which combination is effective to afford a combination of the lowest NO x and smoke emissions at the lowest fuel consumption at independent engine control values for the diesel engine that are optimum to afford production of a combination of the lowest NO x and smoke emissions at the lowest fuel consumption, whereby the NOx and smoke emissions from the diesel engine are reduced by at least 10% and 15%, respectively.
- the independent engine control values are set as described above.
- the ranges for the preferred low T50 and high cetane number combinations, as well as the additional high distillation curve slope and ranges are the same as described above.
- the method and composition of the present invention are illustrated using fuels that were blended from several intermediate refinery blend streams (i.e., blending components for a diesel fuel) and combinations of finished distillate fuels from several refineries (i.e., diesel fuels). These blends and finished fuels represent different processing methods and crude oil sources. A total of eleven different experimental diesel fuels obtained from intermediate refinery blends streams and combinations of finished distillate fuels from four refineries were used.
- Variables chosen for the set of fuels employed included cetane numbers, boiling point distribution, aromatics content and cetane improver.
- the eleven different experimental diesel fuels obtained from intermediate refinery blends streams and combinations of finished distillate fuels from the four refineries demonstrated variations in three properties: cetane number, aromatic content and distillation temperatures. Fuels having three levels of cetane numbers of approximately 35, 45 and 55 were employed. The fuels employed had boiling point distributions that are within the range of either No. 1 or No. 2 diesel fuel (as required in ASTM D975 Standard Specification for Diesel Fuel Oils), with roughly three levels of T10 and two levels of T90, which represent the temperatures to achieve 10% and 90% distillation, respectively.
- the aromatics contents of the fuels employed were adjusted as necessary to meet cetane and boiling point values and varied from about 20% to about 50%.
- 2-Ethyl hexyl nitrate was employed as the cetane improver additive in order to compensate for lower cetane numbers that resulted from the use of high boiling point aromatic stocks in order to modify the boiling point distributions in several of the fuels.
- the test fuels are labeled as baseline, C, D, F, G, H, I, J, K, C+, D+.
- the baseline fuel is a typical, market available, No. 2 diesel fuel or ULSD blend.
- the two fuels with a "plus" symbol (C+ and D+) represent the ones which contain a cetane improver in significant quantities providing a cetane number boost of almost 9 over their base blends (C and D).
- a cetane improver is an additive used to increase the cetane level without altering other fuel properties. Typical formulations of these additives include peroxides and nitrates. Ethyl hexyl nitrate was used as the improver in the fuels C+ and D+.
- Figure 1 plots the distillation curves for the various fuels.
- the baseline fuel has the distillation of a typical No. 2 diesel fuel, while fuels D and K are the regular No. 1 diesel fuel.
- the fuel H has a much higher T10 compared to the others, whereas fuel G with a low T10 is lighter than the typical kerosene. From the distillation plot in Figure 1, in the region spanning the 10-90% distillate levels, the curves appear rather linear. In this study, the slope between T10 and T90, and T50 are adopted to indicate fuel volatility.
- regression models were developed for relevant performance and emissions parameters following experiments varying engine control settings and fuel properties using a single cylinder engine. These parameters included fuel specific NOx (“fsNOx”), smoke, gross indicated fuel consumption (gisfc), peak cylinder pressure (“pep”), exhaust manifold temperature, crank angle for 50% cumulative heat release (“CA50”) and others.
- fsNOx fuel specific NOx
- gisfc gross indicated fuel consumption
- pep peak cylinder pressure
- CA50 crank angle for 50% cumulative heat release
- the engine response is the sum of the functions fi and f 2 , and may include NO x content of exhaust, smoke (soot) content of exhaust, a fuel consumption measure, such as gross indicated fuel consumption (gisfc) or brake specific fuel consumption (bsfc), engine gas temperature such as exhaust temperature, an engine gas pressure such as engine differential pressure, NO x , peak cylinder pressure (pep), exhaust manifold temperature, crank angle for 50% cumulative heat release (CA50) and/or an engine gas flow rate - to name just a few examples among others.
- a fuel consumption measure such as gross indicated fuel consumption (gisfc) or brake specific fuel consumption (bsfc)
- engine gas temperature such as exhaust temperature
- an engine gas pressure such as engine differential pressure, NO x , peak cylinder pressure (pep)
- exhaust manifold temperature such as engine differential pressure, NO x , peak cylinder pressure (pep)
- CA50 cumulative heat release
- Non-limiting examples or engine control levers or "engine controls” include one or more of: injected fuel amount, number and timing of injection stages, a ratio between air and fuel, a fuel rail pressure, an engine gas temperature, an engine gas pressure, an engine gas flow, oxygen content of intake air, engine speed, and engine load.
- fuel characteristics include, but are not limited to: distillation temperature of the fuel (such mid- distillation temperature, T50), a cetane number of the fuel, a distillation slope for the fuel, aromatic content of the fuel, density of the fuel, and heating value of the fuel.
- the regression model of Equation (1) relates fuel properties and engine controls to the engine responses. Regression models were developed for relevant performance and emissions parameters following experiments varying engine control settings and fuel properties as further described and used to determine calibration parameters for engine control.
- Equation (3) the equations for other engine responses such as smoke and bsfc are set forth in Equations (4) and (5), respectively:
- Equation (2) A set of terms representing fuel properties added to the right hand side of Equation (2) results in Equation (1) above:
- Equation (1) can be extended as set forth in Equation (6) as follows:
- Equation (7) represents a combined model capturing the effect of engine control levers and fuel properties and can be subjected to the same optimization process to determine the optimal control liner settings hereinabove.
- the computational approach described here helps in the following ways: (1) it enables the determination of an "ideal" fuel, and (2) it facilitates a "fuel- flexible" diesel engine when used with the appropriate control strategies which permit real-time dynamic estimation of the relevant fuel properties and on-board adjustments to deliver the best fuel efficiency. Given the generalities used in the present approach, it is applicable across a range of engine platforms and fuel types (including biodiesel).
- calibration tables for engine control are generally static in nature, being initially loaded during manufacture and updated infrequently - typically during service, overhaul or upgrade (if ever).
- the model of Equation (1) can be implemented to change engine performance during operation by accounting for fuel effects.
- the fuel terms in f 2 were (1) chosen appropriately to capture either the physical property effects or the chemistry-induced changes correctly, and (2) inspected for orthogonality, and the least correlated variables were selected for modeling.
- Fuel properties were correlated owing to the coupled relationships between physical features like cetane number and distillation characteristics with chemical attributes such as aromatics content. Owing to the presence of hundreds of hydrocarbon species, using merely a chemical type and molecular size to characterize a given fuel is difficult. Hence, it is essential to identify a perfectly orthogonal set of independent fuel properties to analyze fuel impact on engine behavior. Hence, the least correlated fuel properties need to be isolated and included for regression modeling.
- Table 2 shows simple correlations between select fuel properties: distillation characteristics (T10, T50, T90, and slope), cetane number, mono-, poly-, and total aromatic content, density and heating value. The density and heating values track the impact of fuel chemistry on physical fuel characteristics.
- the numbers in the table represent the R-value, which is a quantitative measure of the degree of linear relationship between two variables, with fractions approaching +1 or -1 signifying a strong linear relationship.
- the variable-pairs which have absolute R-values greater than or equal to 0.6 are highlighted in the table.
- the three distillation temperatures (T10-90) are all correlated to one another and with the poly-aromatic content.
- the cetane number is correlated with the mono- and the total aromatic content.
- the poly-aromatic content is strongly correlated with the fuel density and heating value indicating that heavy fuels tend to have a greater fraction of poly-aromatic stocks and a lower heating value as indicated previously.
- the cetane, T50 and the slope do not show any significant correlation and qualify as terms in the function f 2 in Equation (1). Therefore, the regression model reveals the relative significance of volatility, ignition quality and the distillation temperature change on engine performance and emissions and uncovers the relative sensitivity of engines response to the cetane, T50 and slope.
- a Cummins 6.7 L ISB (1-6) engine modified for single cylinder operation was heavily instrumented to enable precise control and monitoring of critical parameters and used extensively for advanced combustion studies owing to the ability to achieve precise control and measurement of the test parameters.
- the details of the ISB engine are listed in Table 3.
- the cylinder block was that of a multi-cylinder engine, but only one of the cylinders underwent combustion.
- the engine was run on an AVL dynamometer.
- the composition, temperature, humidity and mass flow rate of the fresh air were carefully controlled.
- the intake fresh air was conditioned and its flow regulated through high-precision control valves prior to being mixed with the cooled exhaust gas recirculation ("EGR") stream.
- EGR exhaust gas recirculation
- An electronically controlled high pressure Bosch common rail system provided the fuel injection.
- EGR Almost independent control of EGR, mass flow rate, pressure difference across the engine and the fresh airflow was accomplished by the use of two surge tanks - one each for the intake and the exhaust side.
- the intake manifold temperature was controlled by means of electric heating elements located upstream of the intake surge tank.
- the rate of EGR was measured real time by means of a wide-band oxygen sensor (made by ECM) installed near the engine intake manifold, and controlled by actuating the EGR flow control valve.
- the coolant and lubricating systems were external to the engine and maintained temperatures, pressures and flow rates consistent with realistic multi-cylinder engine operation. Each fuel was thoroughly stirred prior to the commencement of the test and was pumped into the engine fuel tank from a barrel through an external lift pump. The engine system was also completely purged before the start of a new fuel test.
- the fresh air mass flow rate was measured by means of a MicroMotion ELITE model coriolis flow meter. Fuel flow rate was calculated using a load-cell based balance system.
- the in-cylinder combustion processes were studied through the use of a high-precision KISTLER water-cooled pressure transducer and recorded and analyzed. Gaseous emissions were measured on both the intake and exhaust side using a multi-function bench made by California Analytical Instruments. Measurements for the exhaust-side NO x , CO, 0 2 , and unburnt hydrocarbon (“UHC”) species were made using appropriate analyzers, and an AVL415 was used to record smoke data.
- UHC unburnt hydrocarbon
- the air-handling system variables included the fresh air-fuel ("AF") ratio and the EGR fraction
- the fuel system levers involved the start of the main injection event, the rail pressure, the pilot injection quantity and the separation between the pilot and the main events.
- the engine was run on a constant-speed mode, and the fueling quantities were held constant by manually adjusting the injector opening durations (also referred to as "ontimes").
- the post fueling ontime and the duration between the start of the main- and the post- was kept constant in this study.
- the total charge flow and the intake manifold pressure were allowed to float.
- the engine experiments involved perturbations of the control parameters to achieve an ultra-low NO x combustion process.
- TDC top dead center
- a two-level, full-factorial, central composite approach was selected for the design of the statistical experiment and the corresponding test plan was executed for each fuel using the statistics package ⁇ .
- Each fuel test involved 90 points representing different levels and combinations of the independent engine control parameters.
- Equation (1) The models for the various engine responses in Equation (1) were formulated such that first function fi is quadratic in the engine control parameters.
- first function fi is quadratic in the engine control parameters.
- a first-order form was used for fuel properties that were least aliased or least correlated as determined previously.
- the two cetane improved fuels C+ and D+ were removed from the regression model and examined separately. The least-squares method was used to fit the models of the form indicated in Equation (1).
- the models for select engine parameters namely fs NO x , smoke, gisfc, pep, and CA50 are presented in their normalized forms through Figures 2-6.
- the normalization was done as a fraction of highest value encountered in the experimental range.
- the gisfc predictions were still accurate in view of their percentage standard deviations (taken as the ratio of the standard deviation between correlation and experimental data divided by the mean of the test data) being close to repeatability of the measurement, which was determined to be around 2%.
- Normalized fs NO x observed is the actual result from the engine test.
- Normalized fs NO x calculated is the result calculated from the mathematical model using the indicated engine operating parameters and fuel properties.
- Normalized gisfc observed is the actual result from the engine test, and “Normalized gisfc calculated” is the result calculated from the mathematical model using the indicated engine operating parameters and fuel properties.
- each model was examined and filtered to include only those terms with a p-value less than 0.05, indicating a 95% confidence on their statistical significance.
- a parameter called t-statistic (defined as the ratio of the estimated model coefficient to the standard error for every term) was computed and inspected for each model. The larger the absolute t-statistic for the term, the more likely the term is significant.
- Figures 7-11 show the absolute t-statistic against their respective engine or fuel parameters for the four responses under consideration.
- the regression model uses the intake oxygen concentration as a surrogate for EGR.
- the strongest dependency for the normalized NO x emission ( Figure 7) is with the intake oxygen concentration: the higher the latter, the lower the diluent mass and hence the greater the NO x .
- the model captures the well established first-order relationships between engine-out NO x and other control parameters.
- the fresh air-fuel ratio, rail pressure, EGR, and the pilot quantity, as well as main injection timing all affect NO x to varying degrees.
- the fuel properties with the most influence on NO x are T50 and to a smaller extent, cetane number.
- a blank value against the "slope" label indicates its relative insignificance in the NO x model.
- Figure 8 shows the first order "significant" terms for smoke: air-fuel ratio and intake 0 2 concentration relate to smoke emissions primarily through their influence on the composition of the intake charge. Among the fuel properties, T50, and to a smaller degree, the slope, appear to impact smoke.
- Figure 9 presents the direct influence of fuel properties on fuel consumption. Furthermore, gisfc is dominated by the influence of engine control parameters over fuel effects. A more advanced main injection timing and higher air-fuel ratio drive improved fuel consumption accompanied with weaker effects for all three fuel properties: T50, cetane number and slope. The two combustion characterization parameters pep and CA50 both appear to be relatively immune to fluctuations in fuel properties (Figures. 10-11).
- the optimization was performed using a gradient-based algorithm for non-linear multivariable responses by invoking the standard function "fmincon" available in the commercial package MATLAB.
- This function uses initial starting values for the various independent variables to converge on an optimal solution through numerical iterations. Around 100 random starting points were assigned to the optimizer for multiple runs to ensure that complete design space for the independent variables was swept, and also to determine a "global" optimum instead of the "local” one.
- Complex response surfaces involving multiple dimensions for the independent variables, and containing linear, square and cross-product terms sometimes produced local inflection points which may not represent the true optimum of the function.
- Table 6 provides the results for the optimization conducted to determine the lowest gisfc, presenting the optimal engine control settings and the "ideal" fuel properties.
- the resultant solution satisfied all the prescribed emissions and mechanical constraints listed in Table 4.
- the optimal engine calibration calls for a high air-fuel ratio, low intake oxygen concentration, high rail pressure, advanced main injection timing, small pilot quantity and a moderate separation between the pilot and the main events.
- a low intake oxygen concentration is a key enabler for NO x reduction.
- Higher air-fuel ratios and elevated rail pressures relate to smoke mitigation: the latter typically providing for greater spray penetration, smaller droplet diameters, and faster vaporization.
- Small pilot quantities aid reductions in combustion noise through early charge-stratification whereas advanced injection timings enhance fuel consumption.
- the optimal fuel properties represent a low T50, a high cetane number and a moderate distillation slope. Fundamentally, these fuel property values suggest a general preference for a more volatile fuel with enhanced ignition quality and are consistent with the relationships captured in the individual models.
- Figure 12 plots the NO x -gisfc tradeoff (in normalized units) comparing three cases: (1) the lowest gisfc possible with the "ideal" fuel properties in Table 6 and optimal engine control settings in Table 6, (2) the best gisfc at the lowest possible ⁇ fixing the fuel properties to that of the baseline, and (3) the NO x -gisfc combination obtained when the optimum engine calibration in Table 6 for the "ideal" fuel is applied to the fuel properties of the baseline fuel in Table 1.
- Table 7 provides a detailed listing of the three different cases showing the engine responses along with the control settings and fuel properties. The information from Table 6 (representing case 1) is repeated in Table 7 and compared to that of cases 2-3. Table 7
- cases 1 and 2 associate the optimum engine performance and emissions achieved between the "ideal” and the baseline fuels and relative benefits realized using the former.
- the “optimal” engine settings for the two fuels though, are different. From Figure 12, the baseline fuel could not be optimized at the same NO x level as that of the "ideal” one.
- the optimization to determine the best gisfc for the baseline fuel (case 2) was done by progressively relaxing the NOx constraint until a converged solution was achieved. The difference in NO x between the two fuels was around 20% as indicated in the figure, and represents a significant departure in emissions behavior.
- the gisfc obtained with the baseline fuel was almost 7% higher than that of the "ideal" fuel.
- case 2 makes use of a retarded main injection timing and a slightly lower rail pressure. The difference in the main injection timing explains some of the gisfc deviation between the baseline and the "ideal" fuels. Therefore, the engine could not be optimized to bring the baseline fuel into performance with case 1 to reduce NO x emissions at minimum fuel consumption.
- case 3 was run by fixing the appropriate lever positions in the respective models for NOx, smoke and gisfc to those of case 1 (or "ideal" fuel).
- the advanced timing and a marginal increase in rail pressure for case 3 bring the fuel consumption within about 1% nearer to that of the "ideal" fuel in case 1, but the baseline fuel causes a significant increase in the NO x emissions and a slight rise in the smoke, as indicated in Table 7.
- case 3 illustrates a reduction in NO x emissions of 41% and a reduction in smoke emissions of 18% when using the "ideal" fuel.
- the NO x benefit in-turn can be leveraged (with further optimization) to slightly increase the EGR rate and advance the main injection timing to enhance fuel efficiency.
- these fuel consumption enhancements represent a substantial improvement to the fuel tank mileage.
- Figures 13-17 provide contour plots for the normalized forms of NO x , smoke and gisfc as a function of select variables or first-order model terms identified to have the strongest effect on each of them as identified in Figures 7-9, respectively.
- the model parameters which are not a part of the x- or the y- axes have been fixed at the optimal settings for the "ideal" fuel provided in Table 6.
- a contour plot of NO x as a function of intake oxygen concentration and T50 (Figure 13) confirms the well established and strong relationship between NO x and EGR. A lower T50 causes NO x to go down, though not as sharply as with EGR.
- Figure 14 shows the variation of NO x as a function of cetane number and T50.
- a combination of lowering T50 and increasing cetane number appears to provide a significant reduction moving from the top left hand corner of the plot (high T50 and low cetane) to the bottom right hand region.
- the effect of T50 appears to be stronger than that of cetane.
- Figure 15 represents the variation of smoke as a function of intake oxygen concentration and T50. Similar to the trend in NO x , a reduction in T50 results in a smoke reduction. The influence of EGR is opposite to that for NO x : higher intake oxygen fractions (and hence lower EGR rates) contribute to lower smoke emissions and is attributed to enhanced oxygen availability for the soot combustion.
- Figure 16 illustrates that the distillation slope of the fuel appears to have a minor effect on smoke emission. Steeper boiling curves provide a smoke benefit which is much weaker than the benefit provided by decreasing values of T50.
- Figure 9 illustrates that the regression model for gisfc is dominated by the engine control variables over the fuel properties.
- Cetane number and, to a smaller extent, the distillation slope are identified as the significant first order terms in the gisfc model.
- Figure 17 shows the variation of gisfc as a function of air-fuel ratio and cetane number.
- a change in air-fuel ratio spanning 18-23 causes gisfc to go down by nearly 6.5% moving from the left to the right of the plot.
- Table 9 compares two fuels with identical T50 and slope, but significantly different cetane numbers.
- the drop in NO x by 10% with a higher cetane fuel is consistent with the model results presented in Figures 7 and 13.
- the NO x emissions reduction of 10% compared to the baseline is the effect of fuel F's higher cetane number.
- the engine control settings were the same for both fuels, although they were not the optimized engine settings. Hence, the engine-out NO x is not comparable to Table 7 values.
Abstract
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NZ599867A NZ599867A (en) | 2009-10-30 | 2010-10-29 | Composition and method for reducing nox and smoke emissions from diesel engines at minimum fuel consumption |
RU2012121933/07A RU2012121933A (en) | 2009-10-30 | 2010-10-29 | COMPOSITION OF DIESEL FUEL AND METHOD FOR REDUCING NOx EMISSIONS AND SOOT FROM DIESEL ENGINE (OPTIONS) |
AU2010313280A AU2010313280A1 (en) | 2009-10-30 | 2010-10-29 | Composition and method for reducing NOx and smoke emissions from diesel engines at minimum fuel consumption |
EP10774395A EP2494172A2 (en) | 2009-10-30 | 2010-10-29 | Fuel composition and method for reducing nox and smoke emissions from diesel engines at minimum fuel consumption |
CN2010800587379A CN102859156A (en) | 2009-10-30 | 2010-10-29 | Composition and method for reducing NOX and smoke emissions from diesel engines at minimum fuel consumption |
ZA2012/03464A ZA201203464B (en) | 2009-10-30 | 2012-05-17 | Composition and method for reducing nox and smoke emissions from diesel engines at minimum fuel consumption |
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US9181878B2 (en) * | 2011-12-19 | 2015-11-10 | Honeywell International Inc. | Operations support systems and methods for calculating and evaluating engine emissions |
JP5585670B2 (en) * | 2013-01-18 | 2014-09-10 | トヨタ自動車株式会社 | Control device for internal combustion engine |
US9556845B2 (en) * | 2013-03-12 | 2017-01-31 | Ecomotors, Inc. | Enhanced engine performance with fuel temperature control |
CN109219736A (en) | 2016-06-09 | 2019-01-15 | 高准公司 | The fuel consumption of the mixture of fuel and water calculates |
JP2018200035A (en) * | 2017-05-29 | 2018-12-20 | 株式会社デンソー | Control device of fuel evaporation system and fuel evaporation system |
US10215112B1 (en) * | 2017-09-08 | 2019-02-26 | GM Global Technology Operations LLC | Method and system for controlling an internal combustion engine |
JP6895399B2 (en) * | 2018-02-06 | 2021-06-30 | 株式会社日立製作所 | Machine control device |
CN111259493B (en) * | 2020-02-09 | 2022-08-02 | 吉林大学 | Vehicle emission model modeling method suitable for intelligent network vehicle emission control |
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JP4450083B2 (en) * | 2008-03-13 | 2010-04-14 | トヨタ自動車株式会社 | Cetane number estimation method |
WO2011053905A1 (en) * | 2009-10-30 | 2011-05-05 | Cummins Inc. | Engine control techniques to account for fuel effects |
AU2010313294A1 (en) * | 2009-10-30 | 2012-05-31 | Bp Corporation North America Inc. | Composition and method for reducing NOx emissions from diesel engines at minimum fuel consumption |
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