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Effects of Fuel Injection Timing in the Combustion of Biofuels in a Diesel Engine at Partial Loads
Abstract
Methyl and ethyl esters of vegetable oils have become an important source of renewable energy with convenient applications in compression-ignition (CI) engines. While the use of biofuels results in a reduction of CO, particulate matter, and unburned hydrocarbons in the emissions, the main disadvantage is the increase of nitrogen oxides (NO x) emissions. The increase in NO x emissions is attributed to differences in chemical composition and physical properties of the biofuel, which in turn affect engine operational parameters such as injection delay and ignition characteristics. The effects of fuel injection timing, which can compensate for these changes, on the performance and emissions in a single cylinder air-cooled diesel engine at partial loads using canola methyl ester and its blends with diesel are presented in this study. The engine is a single cylinder, four stroke, naturally aspirated, CI engine with a displacement volume of 280 cm 3 rated at 5 HP at 3600 rpm under a dynamometer load. It was equipped with a pressure sensor in the combustion chamber, a needle lift sensor in the fuel injector, and a crank angle sensor attached to the crankshaft. Additionally, the temperature of the exhaust gases was monitored using a thermocouple inside the exhaust pipe. Pollutant emissions were measured using an automotive exhaust gas analyzer. Advanced, manufacturer-specified standard, and delayed injection settings were applied by placing shims of different thicknesses under the injection pump, thus, altering the time at which the high-pressure fuel reached the combustion chamber. The start of injection was found to be insensitive to the use of biofuels in the engine. The late injection timing of the engine provided advantages in the CO and NO emissions with a small penalty in fuel consumption and thermal efficiency.
... The agriculture sector makes a major contribution to diesel consumption [5,6] as heavy machinery uses diesel as a fuel [7]. Moreover, automotive diesel engines share 26% of total greenhouse gas emissions into the environment, which is an unignorable threat to the stability of the Earth [8][9][10]. This has motivated researchers to investigate alternative fuels, such as hydroxy gas (HHO) for the versatile dual-fuel ...
... The HHO generation system included AC supply, load controller, transformer, rectifier, reactor, and bubbler. The maximum production capacity Processes 2021, 9,1355 4 of 18 of the unit was 10 L/min. Potassium hydroxide (KOH) was used as a catalyst owing to its higher solubility and affinity for water [22,37]. ...
... Processes 2021,9, 1355 ...
In this study, the response surface methodology (RSM) optimization technique was employed for investigating the impact of hydroxy gas (HHO) enriched diesel on performance, acoustics, smoke and exhaust gas emissions of the compression ignition (CI) engine. The engine was operated within the HHO flow rate range of 0–10 L/min and engine loads of 15%, 30%, 45%, 60% and 75%. The results disclosed that HHO concentration and engine load had a substantial influence on the response variables. Analysis of variance (ANOVA) results of developed quadratic models indicated the appropriate fit for all models. Moreover, the optimization of the user-defined historical design of an experiment identified an optimum HHO flow rate of 8 L/min and 41% engine load, with composite desirability of 0.733. The responses corresponding to optimal study factors were 25.44%, 0.315 kg/kWh, 117.73 ppm, 140.87 ppm, 99.37 dB, and 1.97% for brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), CO, HC, noise, and smoke, respectively. The absolute percentage errors (APEs) of RSM were predicted and experimental results were below 5%, which vouched for the reliable use of RSM for the prediction and optimization of acoustics and smoke and exhaust emission characteristics along with the performance of a CI engine.
... The increasing heat energy (kJ) with successive crank angles can be seen from Figs. 16–18 for compression ratios of 16, 17 and 18. The minimum value of the cumulative heat release corresponds to the zero crossing of Net heat release [16,17]. The magnitude of heat energy is found to be high for increase of loads and increase in compression ratios. ...
... The rate of pressure rise was calculated on finding the slope of pressure with respect to the crank angle. Net heat release is found using the following equation [17][18][19]And the above equation can be written as ...
... The increasing heat energy (kJ) with successive crank angles can be seen from Figs. 16?18 for compression ratios of 16, 17 and 18. The minimum value of the cumulative heat release corresponds to the zero crossing of Net heat release [16,17]. The magnitude of heat energy is found to be high for increase of loads and increase in compression ratios. ...
The importance of diesel engines for human application is growing day by day. The engine operating parameters also play a key role in tuning the engine conforming to the better performance and emission standards. The effect of varying the compression ratios has more impact on the performance, emission and combustion parameters. In this study, single cylinder direct injection CI engine was tested on varying the compression ratios of 18, 17 and 16 at varying loads. The combustion and performance variation on reducing the compression ratios were investigated clearly. Reduction in brake thermal efficiency and increase in exhaust gas temperatures were observed when compression ratio was reduced from 18 to 16. The brake specific fuel consumption was increased on reducing the compression ratio. Reduction of peak cylinder pressure was observed on reduction of compression ratio and the ignition delay period increased on reducing the compression ratio. The peak heat release rate was closer to TDC on increasing compression ratios from 16 to 18. The rate of pressure rise was also investigated and showed maximum of 5.38 bar/°CA and minimum of 0.78 bar/°CA on above compression ratios. Cumulative heat release was also evaluated in this study showing higher heat energy for higher loads and compression ratios. The performance and combustion parameters on the useful compression ratio of 18 were also justified.
... The biodiesel usage in the U.S alone is expected to reach 4000 million gallons (15000 million liters) in 2030. Hence, a comprehensive knowledge of the effects of biodiesels and their blends on NO x is required for the use Journal of Energy and Environmental Sustainability, 1 (2016) [67][68][69][70][71][72][73][74][75][76] of biodiesels to become prevalent. Therefore, it is crucial to understand the effects of fuel properties and operating characteristics of the engines on biodiesel NO x emission to develop enhanced mitigation and abatement techniques. ...
... Hence, the authors suggested that retarding the injection timing was a potential way of reducing NO x emissions. In agreement with this claim, a reduction in brake-specific NO x emission index was observed with the retarded start of combustion (SOC) timing for SME/diesel blends [Moscherosch et al., 2010] and CME/diesel blends [Sequera et al., 2011]. ...
Biodiesels are produced by the transesterification of corresponding triglyceride feedstocks of vegetable (example: soybean, canola, palm, karanja) or animal fat sources. Currently, the leading feedstocks are soybean oil in the U.S., canola oil and rapeseed oil in Canada and Europe, and palm, karanja, jatropha and other oils in Asia. Due to the cost and production considerations of these biodiesels, blending biodiesels with the petroleum fuels appears to be a prudent option in the near-term. The use of biodiesels in compression ignition engines results generally in a reduction in the emissions of carbon monoxide (CO), hydrocarbons (HC), and particulate matter (PM), but a slight increase in the oxides of nitrogen (NOx) emission. The reported NOx emissions do not exhibit definitive trends and the results are significantly influenced by many factors, including engine type and design, test cycle, start of injection, ignition delay, fuel composition, adiabatic flame temperature, radiative heat transfer, fluid dynamics and combustion phasing. Due to appreciable variations in the physical properties and the highly nonlinear nature of the combustion process, the NOx emission with biodiesel blends does not vary monotonically with the percentage of biodiesel in the blend. Hence, the intricate dependence of NOx on biodiesel and its blending effect cannot be completely explained under all engine type and operating conditions. Although the literature contains several studies on the performance and emissions of compression ignition engines fueled with neat biodiesels, the information on the effects of blends is scattered and has not yet achieved a definitive
status to explain the blending effect on NOx. Hence, this work was motivated to review the available data with respect to the NOx emission from engines fueled with the petroleum diesel/biodiesel blends.
... Its tree is native to the Indian subcontinent, but is now grown all over the world. There have been a number of experimental studies during the last two decades dealing with the production and utilization of biodiesel produced from Jatropha, Karanja, and other oils [10][11][12][13][14][15][16][17][18][19]. A variety of engines have been employed to investigate the performance and emission characteristics of these fuels. ...
Biofuels produced from nonedible sources that are cultivated on marginal lands represent a viable source of renewable and carbon-neutral energy. In this context, biodiesel obtained from Jatropha and Karanja oil seeds have received significant interest, especially in South Asian subcontinent. Both of these fuels are produced from nonedible plant seeds with high oil content, which can be grown on marginal lands. In this research, we have investigated the performance and emission characteristics of Jatropha and Karanja methyl esters (biodiesel) and their blends with diesel. Another objective is to examine the effect of long-term storage on biodiesel's oxidative stability. The biodiesels were produced at Indian Institute of Technology Kanpur, (IIT Kanpur), India, and the engine experiments were performed in a single cylinder, four-stroke, compression ignition engine at Argonne National Laboratory (ANL), Chicago. An endoscope was used to visualize in-cylinder combustion events and examine the soot distribution. The effects of fuel and start of injection (SOI) on engine performance and emissions were investigated. Results indicated that ignition delay was shorter with biodiesel. Consequently, the cylinder pressure and premixed heat release were higher for diesel compared to biodiesel. Engine performance data for biodiesel (J100, K100) and biodiesel blends (J30, K30) showed an increase in brake thermal efficiency (BTE) (10.9%, 7.6% for biodiesel and blend, respectively), brake specific fuel consumption (BSFC) (13.1% and 5.6%), and nitrogen oxides (NOx) emission (9.8% and 12.9%), and a reduction in brake specific hydrocarbon emission (BSHC) (8.64% and 12.9%), and brake specific CO emission (BSCO) (15.56% and 4.0%). The soot analysis from optical images qualitatively showed that biodiesel and blends produced less soot compared to diesel. The temperature profiles obtained from optical imaging further supported higher NOx in biodiesels and their blends compared to diesel. Additionally, the data indicated that retarding the injection timing leads to higher BSFC, but lower flame temperatures and NOx levels along with higher soot formation for all test fuels. The physicochemical properties such as fatty acid profile, cetane number, and oxygen content in biodiesels support the observed combustion and emission characteristics of the fuels tested in this study. Finally, the effect of long-term storage is found to increase the glycerol content, acid value, and cetane number of the two biodiesels, indicating some oxidation of unsaturated fatty acids in the fuels.
... Its tree is native to the Indian subcontinent, but is now grown all over the world. There have been a number of experimental studies during the last two decades dealing with the production and utilization of biodiesel produced from Jatropha, Karanja, and other oils10111213141516171819. A variety of engines have been employed to investigate the performance and emission characteristics of these fuels. ...
Biodiesel has emerged as one of the most promising alternative fuel to mineral diesel in last two decades globally. Lower blends of biodiesel emit fewer pollutants, while easing pressure on scarce petroleum resources, without sacrificing engine power output and fuel economy. However, diesel engines emit significant amount of particulate matter (PM), most of which are nanoparticles. Due to the adverse health impact of PM emitted by compression ignition (CI) engines; most recent emission legislations restrict the total number of particles emitted, in addition to PM mass emissions. Use of biodiesel leads to reduction in PM mass emissions; however, the particle size-numbers distribution has not been investigated thoroughly. In this paper, PM emission characteristics from Karanja biodiesel blends (KB20 and KB40) in a modern common rail direct injection (CRDI) engine used in a sports utility vehicle (SUV) with a maximum fuel injection pressure of 1600â €‰bar have been reported. This study also explored comparative effect of varying engine speeds and loads on particulate size-number distribution, particle size-surface area distribution, and total particulate number concentration from biodiesel blends vis-à-vis baseline mineral diesel. This study showed that particulate number emissions from Karanja biodiesel blends were relatively higher than baseline mineral diesel.
... It is evident that gas oil or diesel fuel is one of industrial fuels. Content of gas oil could be improved by manufacturing technology and premium quality of oil [2]. Gas oil has some disadvantages for application in a diesel engine. ...
The current paper reviews the effects of the oxygenated and nitrogenated additives to see the results of the physicochemical efficiency and performance through engine tests work by gas oil mixtures. The oxygenated compounds used in the formulations compose of 2-methoxy ethyl ether (MXEE), nitromethane, and nitroethane. The presence of ethanol and MXEE significantly alter the characteristics of flash point and distillation curve behaviors and marking up the cetane number, improving the fuel's performance in engine tests. The fuel formulations comprising 2-5% v/v additives, 5-10% v/v ethanol, and diesel 90-95% v/v were produced. The soot formation can be reduced by more than 50%, 30%, and 27% by application of the diesel formulations; E-NE5-10, E-NM5-10, and E-MX5-10, respectively. [DOI:10.1115/1.4007483]
... Most studies dealing with biodiesel reported higher emissions of NO x as documented by EPA [31]. The increase in NO x emissions could be attributed to differences in chemical composition and physical properties of the biodiesel, which in turn affect engine operational parameters such as injection delay and ignition characteristics [32]. However, some studies also reported a decrease in NO x emissions with emphasis in fuel properties, pretreatment or refining, and the types of feedstocks [33][34][35]. ...
The study aims to investigate the real-time engine performance in terms of brake power, thermal efficiency and emission characteristics of a diesel engine. Waste vegetable oil samples were collected from several sources, mixed, and refined before transesterification. Test fuels include ultralow sulfur diesel and seven waste cooking oil biodiesel blends. Real-time data acquisition of engine performance was implemented using LABVIEW program while following the society of automotive engineers (SAE) power test code. Results showed that acid number was reduced by 99% after refining. NOx has reduced by 33% while thermal efficiency increased by 7.5% when using waste vegetable oil biodiesel.
... That is, on one hand, the diesel vehicle users have to pay much more money on the vehicle/engine and fuel; on the other hand, many engine manufacturers might be obsolete by the regulation because of their limited engine development abilities and the market supply capacity of the common rail injection system and SCR system. Content of gas oil could be improved by manufacturing technology and premium quality of oil [6]. ...
In this article, a 2102QB diesel engine was retrofitted to run on DME. The effects of EGR on the DME engine power output, DME fuel consumption, and emission characteristics were investigated. Experimental results show that, DME engine power and fuel economy are both improved. The stoichiometric air/fuel ratio of DME is 9/1. DME engine can run properly if the air/fuel ratio is leaner than that due to the introduction of EGR. Only under fuel rich conditions, DME engine power output, fuel economy, HC and CO emissions become worse. NOx emissions can be reduced easily by the use of EGR.
Based on the experimental data, the specific NOx emissoin was calculated and then it was used to set the rate of EGR under the ESC 13 operating conditions. By the designed EGR strategies, the DME engine NOx emissions under ESC operating conditions meets the requirement of Euro IV and V. At the mean time, HC and CO emissions of the DME engine were evaluated. The increase of CO and HC emissions require oxidation after treatment to meet their own standards. © 2014 American Institute of Chemical Engineers Environ Prog, 2014 34: 881–889, 2015
... The recent increase of world oil price and the growing awareness of environmental problems associated with the use of petroleum fuels, have led to the renewed interest in alternative fuel12345. DME is one of the most promising alternative fuels for compression ignition engines. DME has a simple molecular structure (CH3-O-CH3) with high oxygen content and cetane number, and no C-C bond in its molecule. ...
To investigate the effects of fuel temperature on the injection process in the fuel-injection pipe and the combustion characteristics of compression ignition (CI) engine, tests on a four stroke, direct injection dimethyl ether (DME) engine were conducted. Experimental results show that as the fuel temperature increases from 20 to 40 °C, the sound speed is decreased by 12.2%, the peak line pressure at pump and nozzle sides are decreased by 7.2% and 5.6%, respectively. Meanwhile, the injection timing is retarded by 2.2 °CA and the injection duration is extended by 0.8 °CA. Accordingly, the ignition delay and the combustion duration are extended by 0.7 °CA and 4.0 °CA, respectively. The cylinder peak pressure is decreased by 5.4%. As a result, the effective thermal efficiency is decreased, especially for temperature above 40 °C. Before beginning an experiment, the fuel properties of DME, including the density, the bulk modulus, and the sound speed were calculated by "ThermoData." The calculated result of sound speed is consistent with the experimental results.
Primary alcohols such as methanol, ethanol, and butanol have exhibited excellent potential as possible alternative fuels for spark ignition (SI) engines because they are renewable, cleaner and safer to store and transport. However, it remains important to investigate the technical feasibility of adapting these primary alcohols in existing SI engines. In this research, a multi-point port fuel injection (MPFI) system equipped SI engine was used for assessing and comparing the combustion, performance, and emission characteristics of various alcohol-gasoline blends (gasohols) vis-à-vis baseline gasoline. The experiments were performed for different engine loads at rated engine speed. Experimental results exhibited relatively superior combustion characteristics of the engine fueled with gasohol than the baseline gasoline, especially at medium engine loads. Among different test fuels, the methanol-gasoline blend (GM10) exhibited relatively more stable combustion characteristics than the ethanol-gasoline blend (GE10) and butanol-gasoline blend (GB10). In this study, relatively superior engine performance of the gasohol-fueled engine was observed at all engine loads and speeds. GB10 exhibited the highest brake thermal efficiency (BTE), followed by GM10 amongst all test fuels. The effect of improved combustion was also reflected in the emission characteristics, which exhibited that GB10 emitted relatively lower carbon monoxide (CO) and hydrocarbons (HC) than other test fuels. GB10 emitted relatively higher nitrogen oxides (NOx) than GM10 and GE10. Unregulated emission results exhibited that the engine fueled with gasohols emitted relatively lower sulfur dioxide (SO2), ammonia (NH3), and various saturated and unsaturated HCs than the baseline gasoline. The GM10-fuelled engine was relatively more effective in reducing unregulated emissions among all test fuels. This study concluded that methanol and butanol blending with gasoline resulted in superior engine performance and reduced harmful emissions in MPFI transport engines. This offered an excellent option to displace fossil fuels partially and reduce emissions simultaneously.
This study investigates the effect of compression ratio (CR: 16, 17, standard 17.5, 18) and injection timing (IT: 21 ˚CA, standard 23 ˚CA, 25 ˚CA) of a single cylinder direct injection diesel engine having power output 3.5 kW at rated speed 1500 rpm fueled by an optimal Nahar methyl ester blend (NME40). For NME40/CR18, the BTE is improved by 1.09% and EGT is lowered by 2.98% compared to NME40 at standard engine settings, at full load. The HC, CO, and smoke emission decreased for NME40/CR18 by about 15.38%, 21.5%, and 0.5% compared to NME40 at standard setting, whereas it is reduced by 25.45%, 23.73%, and 3.4% compared to diesel respectively at full load. At full load, the NOx emission for NME40/CR18 lowered by 4.73% compared to diesel. Combustion analysis reveals that higher CR has positive impact on cylinder peak pressure. Lower ID observed for higher CR and retarded IT operation.
Fuel injection timing is an important control parameter for engine combustion optimization and emissions control. However, the actual fuel injection timing is different from the nominal one commanded by the electronic control unit, due to the system hydraulic lag or the possible communication malfunction. In this study, a simple estimate approach based on the injector inlet pressure is proposed to capture four critical characteristic instants at the start and end of injection. The critical characteristic moments estimated using this pressure-based approach are validated against those determined by the actual injection rate profiles, in the context of different single or split injection processes. The comparison revealed that the characteristic injection moments estimated by the injector inlet pressures and those determined by the actual injection rate profiles have a satisfactory agreement, certifying the broad applicability and reliability of this pressure-based approach in the detection of the real fuel injection start and end time.
The use of diesel engines is increasing rapidly thanks to their superior fuel economy, higher efficiency and excellent reliability. The energy crisis of fossil fuel depletion, rising price of diesel and environmental degradation have triggered a search for clean, sustainable and alternative fuels for internal combustion engines. Biodiesel is one of the most promising and demanding alternative fuels because it is a biodegradable, non-toxic and renewable fuel. In the present work, an experimental investigation on the effect of injection timing on engine performance, emissions and combustion characteristics with coconut oil methyl ester (CME) was conducted in a high-pressure common-rail direct injection diesel engine. The tests were performed at constant speed of 2000 rpm and 50% throttle position operation. The test fuels included baseline diesel fuel and two different fuel blends of CME (B20 and B40). The injection timing was varied from -4 to 8 °ATDC (with two degree crank angle interval) measured from standard main injection timing of 2 °ATDC. It was found that the retarded injection timing caused a reduction in brake power, brake thermal efficiency and NOx emissions, while an increase in brake specific fuel consumption, brake specific energy consumption and smoke emissions. In terms of combustion characteristics, the results showed that injection timing has significant effects on variation in peak combustion pressure and heat release rate. Overall, the results revealed that the engine performance of CME fuel blends was comparable to that of conventional diesel and altering the injection timing resulted in a trade-off between engine performance and emissions.
Diesel engines play a major role in the modern industrialization and finds indispensable task in everyday life and the application of alternate fuels especially, the transesterified fuels have become more vital in order to reduce pollution and decrease the usage of conventional fuels. Optimization of engine variables like adjusting the injection timing, injection pressure and others play a significant role in enhancing the performance of the engine. In the present work, Mahua biodiesel blends were preferred as fuel in a single cylinder direct injection CI engine and the injection timing was advanced to 25°bTDC and retarded to 20°bTDC from the standard timing of 23°bTDC. The combustion parameters like In cylinder pressure, Net heat release, cumulative heat release and Rate of pressure rise were evaluated and studied for B10 and B20 blends for the above injection timings at full load condition and these were also compared with straight diesel. The B10 and B20 blends exhibited good combustion characteristics of higher peak pressure, higher heat release and slightly increased ignition delay compared to straight diesel.
The gas-engine driven air-to-water heat pump, type air conditioning system, is composed of two major thermodynamic cycles (including the vapor compression refrigeration cycle and the internal combustion gas engine cycle) as well as a refrigerant-water plate heat exchanger. The thermal modeling of gas engine driven air-to-water heat pump system with engine heat recovery heat exchangers was performed here for the heating mode of operation (in which it was required to model engine heat recovery heat exchanger). The modeling was performed using typical thermodynamic characteristics of system components, Artificial Neural Network and the multi-objective genetic algorithm optimization method. The comparison of modeling results with experimental ones showed average differences of 5.08%, 5.93%, 5.21%, 2.88% and 6.2% which shows acceptable agreement for operating pressure, gas engine fuel consumption, outlet water temperature, engine rotational speed, and system primary energy ratio.
Amid various methods available to reduce pollutant emissions and to improve performance and combustion characteristics of a diesel engine, emulsified fuel seems to be promising. However, because of its different properties from diesel, a biodiesel emulsion is incompetent to provide standard diesel performance. Once combusted in a diesel engine; the proper adjustment of engine operating parameters with the presence of "microexplosion" may amend the performance of a biodiesel emulsion run engine. In order to realize this fact, a comprehensive study has been carried out in a variable compression ratio diesel engine running with two-phase water in a palm biodiesel emulsion. The engine operating parameters studied and optimized are compression ratio (CR), injection timing (IT), and load. The water emulsions of palm oil methyl ester (WIP) with various specifications have been prepared by commercially available surfactants with appropriate HLB values. Water quantity (5% and 10%), surfactant quantity (1%, 2%, and 3%), and HLB values (4.3, 5, and 6) are the parameters optimized to attain the stable WIP by means of mean droplet diameter measurement and stability study. The optimized WIP of 5% water, 3% surfactant of 6 HLB is then tested in a diesel engine at varying CR (17, 17.5, and 18) and IT (20, 23, and 28 deg BTDC). For each of the combinations of CR and IT, the load has been varied from idling conditions to full load (12 kg) with an increment of 20% (2.4 kg) and 110% (13.2 kg) of full load. The results are analyzed in the form of performance, combustion, and emission parameters with respect to the baseline diesel run (CR = 17.5 and IT = 23 deg BTDC).
The acorn (Quercus frainetto L.) kernel oil is extracted from the kernels of the acorn that is grown in Sakarya which is in the Marmara region, Turkey. Acorn kernel oil (AKO) is obtained in 10 wt. , by solvent extraction. Acorn kernel oil is investigated as an alternative feedstock for the production of a biodiesel fuel. The fatty acid profile of the oil consists primarily of oleic, linoleic, palmitic, and stearic acids. Before processing alkalin transesterification reaction, the high free fatty acid (FFA) of the crude acorn kernel oil is decreased by using acid esterification method. Biodiesel is prepared from acorn kernel (AK) by transesterification of the acid esterified oil with methanol in the presence of potassium hydroxide (KOH) as catalyst. The maximum oil to ester conversion was 90. The viscosity of biodiesel is closer to that of diesel and the heating value is about 6.4 less than that of petroleum diesel No. 2. All of the measured properties of the produced acorn kernel oil methyl ester (AKOME) are being compared to the current quality requirements according to EN14214 and ASTM D 6751. The comparison shows that the methyl esters of acorn kernel oil could be possible used as diesel fuel replacements.
Suitable cylinder charge preparation is deemed critical for the attainment of a highly homogeneous, diluted, and lean cylinder charge which is shown to lower the flame temperature. The resultant low temperature combustion (LTC) can simultaneously reduce the NOx and soot emissions from diesel engines. This requires sophisticated coordination of multiple control systems for controlling the intake boost, exhaust gas recirculation (EGR), and fueling events. Additionally, the cylinder charge modulation becomes more complicated in the novel combustion concepts that apply port injection of low reactivity alcohol fuels to replace the diesel fuel partially or entirely. In this work, experiments have been conducted on a single cylinder research engine with diesel and ethanol fuels. The test platform is capable of independently controlling the intake boost, EGR rates, and fuelling events. Effects of these control variables are evaluated with diesel direct injection and a combination of diesel direct injection and ethanol port injection. Data analyses are performed to establish the control requirements for stable operation at different engine load levels with the use of one or two fuels. The sensitivity of the combustion modes is thereby analyzed with regard to the boost, EGR, fuel types and fueling strategies. Zero-dimensional cycle simulations have been conducted in parallel with the experiments to evaluate the operating requirements and operation zones of the LTC combustion modes. Correlations are generated between air-fuel ratio (λ), EGR rate, boost level, in-cylinder oxygen concentration and load level using the experimental data and simulation results. Development of a real-time boost-EGR set-point determination to sustain the LTC mode at the varying engine load levels and fueling strategies is proposed.
In this study, the in-cylinder soot and NOx trade off was investigated in a Compression Engine by implementing Premixed Charge Compression Ignition (PCCI) coupled with Low Temperature Combustion (LTC) for selected regimes of 1–3 bars IMEP. In order to achieve that, an omnivorous (multi-fuel) single cylinder diesel engine was developed by injecting n-butanol in the intake port while being fueled with biodiesel by direct injection in the combustion chamber. By applying this methodology, the in-cylinder pressure decreased by 25% and peak pressure was delayed in the power stroke by about 8 CAD for the cycles in which the n-butanol was injected in the intake manifold at the engine speed of 800 rpm and low engine loads, corresponding to 1–3 bars IMEP. Compared with the baseline taken with ultra-low sulfur diesel no. 2 (USLD#2), the heat release presented a more complex shape. At 1–2 bars IMEP, the premixed charge stage of the combustion totally disappeared and a prolonged diffusion stage was found instead. At 3 bars IMEP, an early low temperature heat release was present that started 6 degrees (1.25 ms) earlier than the diesel reference heat release with a peak at 350 CAD corresponding to 1200 K. Heat losses from radiation of burned gas in the combustion chamber decreased by 10–50% while the soot emissions showed a significant decrease of about 98%, concomitantly with a 98% NOx reduction at 1 IMEP, and 77% at 3 IMEP, by controlling the combustion phases. Gaseous emissions were measured using an AVL SESAM FTIR and showed that there were high increases in CO, HC and NMHC emissions as a result of PCCI/LTC strategy; nevertheless, the technology is still under development. The results of this work indicate that n-butanol can be a very promising fuel alternative including for LTC regimes.
In this study the Reactive Controlled Combustion Ignition (RCCI) obtained by early port fuel injection (PFI) of n-butanol and direct injection (DI) of biodiesel were compared with in cylinder direct injected binary mixture of n-butanol and biodiesel with the same mass ratio of 3:1 in both fuelling strategies. The combustion and emissions characteristics were investigated at 5 bars IMEP at 1400 rpm. The ignition for DI of n-butanol-biodiesel binary blends showed a delay by approximately 7.5°CAD compared with the PFI case. For the binary mixture, n-butanol-biodiesel, the combustion pressure has decreased by 50% compared to the PFI of butanol. The maximum in cylinder gas temperature decreased by 100K for the n-butanol-biodiesel mixture versus ULSD#2 and has also experienced a 10° CAD delay. The premixed charge combustion has been split into two regions of high temperature heat release, an early one BTDC, and a second stage, ATDC for the PFI strategy. Increasing the load to 7.5 bars IMEP, heavy knock occurred for the PFI case. The soot emissions showed a 90% decrease with n-butanol injection PFI and by 98% reduction for DI of n-butanol binary mixture with the biodiesel, while the NOx emissions were reduced by 40% in both cases. The aldehyde emissions exhibited a significant 95% decrease for the n-butanol-biodiesel binary mixture compared with the n-butanol PFI. The mechanical efficiency at 80% and thermal efficiency and 38% were found similar, for both fuelling strategies.
The results of this work suggest that the DI of n-butanol-biodiesel binary mixtures is more effective in reducing emissions than PFI of n-butanol combined with DI of biodiesel and also less likely to produce knock.
Previous research indicates that the low temperature combustion (LTC) is capable of producing ultra-low nitrogen oxides (NOx) and soot emissions. The LTC in diesel engines can be enabled by the heavy use of exhaust gas recirculation (EGR) at moderate engine loads. However, when operating at higher engine loads, elevated demands of both intake boost and EGR levels to ensure ultra-low emissions make engine controllability a challenging task. In this work, a multi-fuel combustion strategy is implemented to improve the emission performance and engine controllability at higher engine loads. The port fueling of ethanol is ignited by the direct injection of diesel fuel. The ethanol impacts on the engine emissions, ignition delay, heat-release shaping and cylinder-charge cooling have been empirically analyzed with the sweeps of different ethanol-to-diesel ratios. Zero-dimensional phenomenological engine cycle simulations have been conducted to supplement the empirical work. The multi-fuel combustion of ethanol and diesel produces lower emissions of NOx and soot while maintaining the engine efficiency. The experimental set-up and study cases are described and the potential for the application of ethanol-to-diesel multi-fuel system at higher loads has been proposed and discussed.
This paper presents experimental analyses of the ignition delay (ID) behavior for diesel-ignited propane and diesel-ignited methane dual fuel combustion. Two sets of experiments were performed at a constant speed (1800 rev/min) using a 4-cylinder direct injection diesel engine with the stock ECU and a wastegated turbocharger. First, the effects of fuel-air equivalence ratios (Φpilot ∼ 0.2–0.6 and Φoverall ∼ 0.2–0.9) on IDs were quantified. Second, the effects of gaseous fuel percent energy substitution (PES) and brake mean effective pressure (BMEP) (from 2.5 to 10 bar) on IDs were investigated. With constant Φpilot (> 0.5), increasing Φoverall with propane initially decreased ID but eventually led to premature propane autoignition; however, the corresponding effects with methane were relatively minor. Cyclic variations in the start of combustion (SOC) increased with increasing Φoverall (at constant Φpilot ), more significantly for propane than for methane. With increasing PES at constant BMEP, the ID showed a nonlinear (initially increasing and later decreasing) trend at low BMEPs for propane but a linearly decreasing trend at high BMEPs. For methane, increasing PES only increased IDs at all BMEPs. At low BMEPs, increasing PES led to significantly higher cyclic SOC variations and SOC advancement for both propane and methane. Finally, the engine ignition delay (EID) was also shown to be a useful metric to understand the influence of ID on dual fuel combustion.
Over the past several years, there has been increased interest in reformulated and alternative diesel fuels to control emissions and provide energy independence. In the following study, a California diesel fuel was compared with neat biodiesel, an 80% California diesel/20% biodiesel blend, and a synthetic diesel fuel to examine the effects on emissions. Chassis dynamometer tests were performed on four light heavy-duty diesel trucks using each of the four fuels. The results of this study showed that biodiesel, the biodiesel blends, and the synthetic diesel produced generally lower THC and CO emissions than California diesel. NOx emissions were comparable over most of the fuel/ vehicle combinations, with slightly higher NOx emissions found for the two noncatalyst vehicles on 100% biodiesel. Particulate emissions were slightly higher for two test vehicles and significantly higher for a third test vehicle on the biodiesel fuels. Chemical analyses showed elemental and organic carbon to be the primary constituents of the diesel particulate, accounting for 73-80% of the total mass for the four vehicles. Neat biodiesel had the highest organic carbon fractions for each of the test vehicles. PAH emissions for all fuel combinations were relatively low, probably due to the low fuel PAH levels.
Biodiesel is an alternative fuel for internal combustion engines. It can reduce carbon monoxide (CO), hydrocarbon (HC) and particulate matter (PM) emissions, compared with diesel fuel, but there is also an increase in nitrogen oxides (NOx) emission. This study is aimed to compare the effect of applying a biodiesel with either 10% blended methanol or 10% fumigation methanol. The biodiesel used in this study was converted from waste cooking oil. Experiments were performed on a 4-cylinder naturally aspirated direct injection diesel engine operating at a constant speed of 1800 rev/min with five different engine loads. The results indicate a reduction of CO2, NOx, and particulate mass emissions and a reduction in mean particle diameter, in both cases, compared with diesel fuel. It is of interest to compare the two modes of fueling with methanol in combination with biodiesel. For the blended mode, there is a slightly higher brake thermal efficiency at low engine load while the fumigation mode gives slightly higher brake thermal efficiency at medium and high engine loads. In the fumigation mode, an extra fuel injection control system is required, and there is also an increase in CO, HC and NO2 (nitrogen dioxide) and particulate emissions in the engine exhaust, which are disadvantages compared with the blended mode.
Biodiesel is the name of a clean burning monoalkyl-ester-based oxygenated fuel made from natural, renewable sources, such as new/used vegetable oils and animal fats. The injection timing plays an important role in determining engine performance, especially pollutant emissions. In this study, the effects of fuel injection timing on the exhaust emission characteristics of a single-cylinder, direct-injection diesel engine were investigated when it was fueled with canola oil methyl ester−diesel fuel blends. The results showed that the brake-specific fuel consumption and carbon dioxide and nitrogen oxide emissions increased and smoke opacity, hydrocarbon, and carbon monoxide emissions decreased because of the fuel properties and combustion characteristics of canola oil methyl ester. The effect of injection timing on the exhaust emissions of the engine exhibited the similar trends for diesel fuel and canola oil methyl ester−diesel blends. When the results are compared to those of original (ORG) injection timing, at the retarded injection timings, the emissions of nitrogen oxide and carbon dioxide increased and the smoke opacity and the emissions of hydrocarbon and carbon monoxide decreased for all test conditions. On the other hand, with the advanced injection timings, the smoke opacity and the emissions of hydrocarbon and carbon monoxide diminished and the emissions of nitrogen oxide and carbon dioxide boosted for all test conditions. In terms of brake-specific fuel consumption, the best results were obtained from ORG injection timing in all fuel blends.
This paper discusses the influence of biodiesel on output characteristics of a diesel engine and optimal timing setup for its injection pump. The influence of biodiesel is studied by running experiments on an NA diesel bus engine MAN D2 2566 with a direct-injection M system. The fuel used is biodiesel produced from rapeseed. Special attention is focused on the determination of the optimal injection-pump timing with respect to engine harmful emissions, engine fuel consumption, and other engine performance parameters. These engine characteristics are compared against those obtained using conventional D2 diesel. Experiments with biodiesel and D2 are run on several engine operating regimes. The engine was monitored for possible operation problems and carefully examined after the tests. The results obtained are presented and analyzed. It is shown that with carefully optimized timing of the pump, the harmful emission of NOx, smoke, HC, and CO can be reduced essentially by keeping other engine characteristics within acceptable limits.
In this paper, we explore the efficacy of (1) reducing the iodine value of soy-derived biodiesel fuels through increasing the methyl oleate (methyl ester of oleic acid) content and (2) addition of cetane improvers, as strategies to combat the biodiesel NOx effect: the increase in NOx emissions observed in most studies of biodiesel and biodiesel blends. This is accomplished by spiking a conventional soy-derived biodiesel fuel with methyl oleate or with cetane improver. The impact on bulk modulus of compressibility, fuel injection timing, cetane number, combustion, and emissions were examined. The conventional B20 blend produced a NOx increase of 3–5% relative to petroleum diesel, depending on injection timing. However, by using a B20 blend where the biodiesel portion contained 76% methyl oleate, the biodiesel NOx effect was eliminated and a NOx neutral blend was produced. The bulk modulus of petroleum diesel was measured to be 2% lower than B20, yielding a shift in fuel injection timing of 0.1–0.3 crank angle. The bulk modulus of the high methyl oleate B20 blend was measured to be 0.5% lower than B20, not enough to have a measurable impact on fuel injection timing. Increasing the methyl oleate portion of the biodiesel to 76% also had the effect of increasing the cetane number from 48.2 for conventional B20 to 50.4, but this effect is small compared to the increase to 53.5 achieved by adding 1000 ppm of 2-ethylhexyl nitrate (EHN) to B20. For the particular engine tested, NOx emissions were found to be insensitive to ignition delay, maximum cylinder temperature, and maximum rate of heat release. The dominant effect on NOx emissions was the timing of the combustion process, initiated by the start of injection, and propagated through the timing of maximum heat release rate and maximum temperature.
Combustion studies on both diesel fuel and vegetable oil fuels, with the standard and advanced injection timing, were carried out using the same engine and test procedures so that comparative assessments may be made. The diesel engine principle demands self-ignition of the fuel as it is injected at some degrees before top dead centre (BTDC) into the hot compressed cylinder gas. Longer delays between injection and ignition lead to unacceptable rates of pressure rise with the result of diesel knock because too much fuel is ready to take part in premixed combustion. Alternative fuels have been noted to exhibit longer delay periods and slower burning rate especially at low load operating conditions hence resulting in late combustion in the expansion stroke. Advanced injection timing is expected to compensate these effects. The engine has standard injection timing of 30°C BTDC. The injection was first advanced by 5.5°C given injection timing of 35.5°C BTDC. The engine performance was very erratic on this timing. The injection was then advanced by 3.5°C and the effects are presented in this paper. The engine performance was smooth especially at low load levels. The ignition delay was reduced through advanced injection but tended to incur a slight increase in fuel consumption. Moderate advanced injection timing is recommended for low speed operations.
Chassis dynamometer tests were performed on seven light heavy-duty diesel trucks comparing the emissions of a California diesel fuel with emissions from four other fuels: ARCO emissions control diesel (EC-D) and three 20% biodiesel blends (one yellow grease and two soy-based). The EC-D and the yellow grease biodiesel blend both showed significant reductions in total hydrocarbons (THC) and carbon monoxide (CO) emissions over the test vehicle fleet. EC-D also showed reductions in particulate matter (PM) emission rates. NOx emissions were comparable for the different fuel types for most of the vehicles tested. The soy-based biodiesel blends showed smaller emissions differences over the test vehicles, including some increases in PM emissions. This is somewhat in contrast to previous studies that have shown larger reductions in THC, CO, and PM for biodiesel blends. The possible influence of different fuels, fuel properties, and engine load on emissions is also discussed.