Advanced Injection Timing Research Articles

Numerical and Optimization Studies on Reactivity Controlled Compression Ignition Engine with Hydrogen and Split Injections

Abstract Effective abatement of harmful tail-pipe emissions from fossil fuel run engines is achieved through low-temperature combustion strategies; Reactivity Controlled Compression Ignition mode of operation has been successful among such concepts. The present work deals with numerical work performed using ANSYS Forte software with n-heptane as a high-reactivity fuel and hydrogen in different proportions as a low-reactivity fuel, respectively. With total energy fixed, the amount of hydrogen is varied from 0-80% fuel injection is regulated accordingly. Pertinent engine in-cylinder parameters with patterns are extracted, emphasizing the combustion phenomena of RCCI operation with the lowest possible emissions targeted, with the combined effects of hydrogen induction, Start of Injection, and split injections. The contours of fuel vapour and emission parameters are obtained to relate the performance with emissions. It is noted that with a split injection strategy at 50/50 and 75/25 split strategy and 45-50% energy share from hydrogen, the NOx, Soot reductions and thermal efficiency penalty are in the range of about 5.5%, 24% and 7.5%, respectively, also, with 30% EGR, about 95% NOx reduction but with higher soot values. A 75/25 split and advanced injection timing of 25obTDC resulted in the RCCI mode of operation with reduced soot emissions, and the use of EGR has resulted in high levels of soot and poor fuel efficiency. Among the models of machine learning tested, Random Forest regressor emerged as the most suitable, with higher R2 values, indicating better predictive capability.

Effects of ammonia energy ratio and PODE injection timing on combustion and emissions in a PODE/ammonia RCCI engine

The application of ammonia as an alternative carbon-free fuel has attracted increasing attention. In this paper, the effects and mechanisms of ammonia energy ratio (AER) and polyoxymethylene dimethyl ethers (PODE) injection timing on the combustion and emissions characteristics of a PODE/ammonia RCCI engine are investigated by both experimental and numerical methods. Results show that increasing AER from 10% to 40% leads to the delayed low temperature heat release (LTHR) due to reduced OH radical generated by PODE and the competition between PODE and ammonia for OH radical consumption. The larger AER increases the indicated thermal efficiency (ITE) by lowering combustion temperature and reducing heat transfer losses at the cost of higher hydrocarbon (HC), carbon monoxide (CO), and unburned NH3 emissions. The reduction of fuel-based nitrogen oxide (NOx) emissions with a larger AER is attributed to the enhanced in-cylinder thermal denitrification reactions. The delayed start of injection (SOI) from −60 °CA ATDC to −45 °CA ATDC leads to the higher peak in-cylinder pressure and temperature, resulting in the larger heat transfer losses and lower ITE. The impact of retarding SOI on NOx is insignificant under the combined effect of more thermal NO formation, less fuel-based NO generation, and weakened denitrification reactions. Additionally, nitrous oxide (N2O) shows dominant effects on the total greenhouse gas (GHG) emissions, and increasing AER or advancing injection timing produces more GHG. Under low loads and low AERs, although the introduction of ammonia helps to improve ITE, more researches are required to further reduce exhaust emissions.

An Evaluation of the Effect of Fuel Injection on the Performance and Emission Characteristics of a Diesel Engine Fueled with Plastic-Oil–Hydrogen–Diesel Blends

Fuelled engines serve as prime movers in low-, medium-, and heavy-duty applications with high thermal diesel efficiency and good fuel economy compared to their counterpart, spark ignition engines. In recent years, diesel engines have undergone a multitude of developments, however, diesel engines release high levels of NOx, smoke, carbon monoxide [CO], and hydrocarbon [HC] emissions. Due to the exponential growth in fleet population, there is a severe burden caused by petroleum-derived fuels. To tackle both fuel and pollution issues, the research community has developed strategies to use economically viable alternative fuels. The present experimental investigations deal with the use of blends of biodiesel prepared from waste plastic oil [P] and petro-diesel [D], and, to improve its performance, hydrogen [H] is added in small amounts. Further, advanced injection timings have been adopted [17.5° to 25.5° b TDC (before top dead centre)] to study their effect on harmful emissions. Hydrogen energy shares vary from 5 to 15%, maintaining a biodiesel proportion of 20%, and the remaining is petro-diesel. Thus, the adopted blends are DP20 ((diesel fuel (80%) and waste plastic biofuel (20%)), DP20H5 (DP20 (95%) and hydrogen (5%)), DP20H10 (DP20 (90%) and hydrogen (10%)), and DP20H15 (DP20 (85%) and hydrogen (15%)). The experiments were conducted at constant speeds with a rated injection pressure of 220 bar and a rated compression ratio of 18. The increase in the share of hydrogen led to a considerable improvement in the performance. Under full load conditions, with advanced injection timings, the brake-specific fuel consumption had significantly decreased and NOx emissions increased.

Study on partial oxidation phenomena of post-injection fuel in diesel engines

In diesel engines, post fuel is injected in the expansion stroke, oxidized by the diesel oxidation catalysts and the high temperature gas re-generates the diesel particulate filters. However, it is empirically known that the post fuel at advanced injection timing is partially oxidized in the cylinder due to the high temperature-pressure conditions and it is a cause of the reduction of fuel consumption. The purpose of this research is to analyze post-injection fuel behaviors in cylinder and investigate the optimum fuel injections that maximize the unburnt hydrocarbons to the diesel oxidation catalysts. The engine employed in this research is a turbo charged 2.0 L four-cylinder DI diesel engine with two fuel injection systems to change the heterogeneity of air-fuel mixture and temperature distributions in cylinder; n-hexane is injected in the intake manifold to produce the homogeneous air-fuel mixture and diesel fuel is directly injected into the cylinder. The partial oxidation ratio of post fuel and the fuel loss mainly by fuel adhesion was calculated by injected fuel quantity, air quantity, and emission data. The 3D-CFD software was introduced to analyze the partial oxidation of post fuel and flow in the cylinder. The heterogeneity of burned gas mixture of post injection atmosphere and the post-injection timings were the parameters of engine tests and 3D-CFD simulations. The results suggest that the heterogeneity of equivalence ratio and the non-uniformity of gas temperature inside the cylinder at the start of post injection affect the partial oxidation of post-injection fuel. The more homogeneous these conditions are, the better the suppression of partial oxidation of post-injection fuel and the avoidance of fuel adhesion to the cylinder wall can be achieved.

The combustion and emission characteristics of pure methanol as a substitute fuel for compression ignition engines

ABSTRACT Methanol, as a carbon-neutral resource, exhibits significant potential in the automotive sector. The objectives of this study are to investigate the fuel economy, emission characteristics, and combustion properties of methanol in compression-ignition engines. The research findings indicated that the combustion duration of methanol significantly extended with increasing speed and load. In comparison to diesel, methanol exhibited a relatively lower peak heat release rate under various operating conditions. With an increase in injection pressure or an advancement in injection timing, the brake specific fuel consumption (BSFC) decreased initially and then increased. The optimal injection pressure for methanol was lower than that for diesel, while the optimal injection timing was advanced. As the EGR rate increased, BSFC gradually decreased at each speed. When comparing optimized methanol with diesel, the brake thermal efficiency (BTE) of methanol was 37.54%, slightly lower than that of diesel. Methanol’s NOx, soot, and CO emissions were significantly lower than diesel, while methanol and formaldehyde emissions were higher, especially with a methanol emission of 0.83 g/kW.h. Overall, applying pure methanol as fuel in compression-ignition engines can significantly reduce emissions while maintaining the BTE as compared with that of diesel fuel, but the methanol emissions in the exhaust increase significantly.

Exploring the Combustion Performance of a Non-Road Air-Cooled Two-Cylinder Turbocharged Diesel Engine

In order to explore the combustion performance of a non-road air-cooled two-cylinder turbocharged diesel engine, an experiment on the effects of engine compression ratio, combustion chamber shape and injection timing were systematically conducted in this study. Moreover, the effects of intake air conditions on combustion performance were numerically investigated using the one-dimensional simulation platform. The findings of this study could help provide new insights for promoting the sustainable development of diesel engines used in generator sets. The results show that the increase in intake air temperature can delay the combustion center of gravity and improve the combustion performance and the sustainability of diesel engines. The decrease in intake air pressure leads to a reduction in oxygen amount during the combustion process, thus causing the deterioration of cylinder pressure and combustion performance. By modifying the combustion chamber, the ignition delay and combustion duration are each extended by 1.6 degrees and 4.2 degrees under 100% engine load. The ignition delay and combustion duration are not obviously affected by modifying the combustion chamber shape under 25% and 50% loads. By increasing the compression ratio from 19.5 to 20.5, the ignition delay and combustion duration are shortened, which could enhance the cylinder pressure and heat release rate. However, reducing the compression ratio from 19.5 to 18.5 could significantly decrease the heat release rate. Under middle and low loads, combustion duration is less affected by injection timing. Under 100% load, the peak cylinder pressure increases to 11.4 MPa, and the ignition delay is shortened by advancing injection timing from −17 °CA to −20 °CA.

The role of charge reactivity in ammonia/diesel dual fuel combustion in compression ignition engine

This study investigates the combustion characteristics of diesel–NH3–air mixture in compression ignition engine. Three different levels of ammonia energy ration (AER) were used for the investigation: 0 % AER (pure diesel), 30 % AER, and 50 % AER. Increasing AER leads to a rise in the initial peak of apparent heat release rate and promotes the prevalence of premixed combustion. Numerical simulations effectively capture the abrupt increase in maximum cylinder pressure (Pmax) from 7.4 to 7.9 MPa as AER increases from 0 to 30 %. Additionally, raising AER from 0 to 30 % extends a high-temperature region externally in the squish zone, attributed to the higher knocking propensity of the 30 % AER premixed charge. The ammonia-assisted diesel accomplish advanced diesel direct injection timing (SOID) at both heavy and medium load conditions. Under light load conditions, an increase in ITE is observed for AER = 50 % as SOID varies from −4 °CA to −10 °CA (ATDC). For medium and high load conditions, ITE monotonically increases with advancing SOID. The maximum ITE of 44.5 % is achieved at SOID = −12 °CA (ATDC) and AER = 30 %.

Influence of In-Cylinder Turbulence Kinetic Energy on the Mixing Uniformity within Gaseous-Fuel Engines under Various Intake Pressure Conditions

To explore the potential for further enhancing the gas mixing uniformity of natural gas (NG) engines, this paper identifies turbulent kinetic energy (TKE), which has an essential impact on gas mixing, as the entry point of the research. After establishing a computational fluid dynamics (CFD) model for NG engines’ direct injection and mixing processes, the inlet pressure is selected as the experimental variable to investigate the influence of TKE on gas mixing uniformity. In particular, by proposing the theoretical concept of the core mixing stage, the numerical variation rule between the best mixture concentration region (BMCR) percentage and the mean turbulent kinetic energy (MTKE) of the core mixing stage is analyzed under certain injection timing conditions. The results indicate that, with identical intake pressures, an advanced gas injection timing elevates the total turbulence kinetic energy (TTKE) during the core mixing stage, thereby amplifying the uniformity of the gas mixture at the ignition. In specific scenarios, as the intake pressure increases, the decreasing trend in the BMCR proportion closely resembles the diminishing trend in the MTKE during the core mixing stage. Scrutinizing the variation trend in either parameter allows for an approximate prediction of the variation trend in the other parameter. When the intake pressure is gradually raised from the naturally aspirated state, the adequacy of the gas jet development is progressively reduced by the increasing back pressure in the cylinder.

Enhancing Combustion Stability in Biodiesel Engines: The Plausibility of n-Butanol Injection Phasing and Reactivity-Controlled Compression Ignition–An Experimental Endeavour

This study explores the synergistic effect of injection phasing on reactivity-controlled compression ignition strategies upon the combustion and stability indices of biodiesel-fuelled single-cylinder four-stroke diesel engines. Mahua Biodiesel was used as the primary fuel, and n-butanol was injected into the manifold to achieve that strategy. The tests were conducted with varying the start of pilot-main injection timing, energy share of biodiesel in split injection and energy share of butanol. This work also entails the various combustion characteristics and the corresponding consequences on the engine’s performance-emission. Ignition delay is shortened with retarded injection timing. At the same time, combustion duration is reduced with higher butanol share and advanced injection timing of biodiesel. The butanol injection and advanced pilot biodiesel injection timing revealed the advancement of combustion phasing. In conjunction with n-butanol port fuel injection, the current study demonstrates the noteworthy and potential superiority of n-butanol as the less reactive constituent. Shortened ignition delay exhibited improved performance and UHC-CO footprint. This study highlights the maximum reduction in regulated emissions compared to operations solely relying on 100% biodiesel. The occurrence of CA50 at 5°–7° CA revealed a maximum decrease in NOX-UHC-CO-CO2 emissions compared to the B100 fuelled strategy. The reduction percentages observed were 53.4%, 97%, 81.1%, and 53.2%, respectively.

Influence of injection timing variation on combustion-emission-performance aspects of emulsified plastic oil-run compression ignition engine

Abstract This study investigates the influence of injection timing (IT) on combustion-emission-performance aspects of the compression ignition (CI) engine, running with emulsified plastic oil (EPO). The IT was advanced (250 bTDC) as well as retarded (210 bTDC) for EPO run engine, and the obtained results were compared with EPO and neat diesel run engine at standard IT (230 bTDC). At full load, the peak cylinder pressure increased to 64.7 bar when the IT was advanced to 250 bTDC. The corresponding peak heat release rate also increased to 40.29 J/CA due to the advancement of IT in comparison with the standard IT. The brake-specific fuel consumption (BSFC) also improved at all loading conditions. However, the advancement of IT increased the nitrogen oxides (NOx), and temperature of exhaust gas slightly. In addition, 250 bTDC for EPO also reduced the unburnt hydrocarbon (HC), carbon monoxide (CO), and smoke emissions w.r.t the standard IT. Largely, the advanced IT improved the majority of the engine characteristics for EPO except for the NOx, but that is also lower than diesel-run operation. Thus, 250 bTDC (for EPO) exhibits promising potential to be implemented in CI engines.

A full-parameter computational optimization of both injection parameters and injector layouts for a methanol/diesel dual-fuel direct injection compression ignition engine

Both the injection parameters and injector layouts of a methanol/diesel dual-fuel direct injection compression ignition engine operated at low loads were optimized using the genetic algorithm to achieve high fuel efficiency and low emissions simultaneously. The important parameters were identified according to the sensitivity analysis, including the in-cylinder initial temperature at intake valve closing (TIVC), methanol fraction, injection timings, and injector locations. The vaporization cooling effect of the direct-injected methanol can be compensated by elevating TIVC, so the maximum methanol fraction depends on the TIVC level. Diesel should be injected before methanol to create a high-reactivity and high-temperature region to trigger ignition efficiently. Spray included angles of diesel and methanol affect the combustion process by controlling the distributions and Overlap Degree of two fuels, and a relatively high Overlap Degree is beneficial to both combustion efficiency and fuel efficiency by targeting the spray plumes of two fuels toward the piston lip. When the methanol injector is off-center installed, the increased Overlap Degree of two fuels is helpful to improve fuel efficiency with a penalty of higher nitrogen oxides (NOx) emissions. Overall, both injectors are suggested to be centrally mounted, and a small off-center installation is allowed for two injectors without deteriorating engine performance, when the partially premixed combustion is performed with advanced injection timings.

Performance analysis and optimization of thermal barrier coated piston diesel engine fuelled with biodiesel using RSM

The current research investigates diesel and simarouba biodiesel blends (10%, 20%, & 30% by volume) in conventional and Low Heat Rejection (LHR) diesel engines, each rated at 4.4 kW. While optimization techniques like Response Surface Method and Taguchi have been extensively studied, the impact of LHR and optimization on LHR engine performance and emissions is rarely explored. Converting the conventional engine to LHR involved applying 300 μm of stabilized zirconia to the piston crown to enhance combustion efficiency. Performance and emissions were analyzed at rated injection pressure (200 bar) and timing (23° before top dead center - btdc). Experiments were continued on LHR engine by varying injection timings (advancing - 26°btdc and retarding - 20°btdc). Advanced injection timing showed significant improvement in performance of Low heat rejection engine. MINITAB statistical tool is used to optimize engine performance using Response Surface Method. The 20% blend showed improved performance in both engines. The optimum values for Low heat rejection engine responses are 26.8%, 0.32 kg/kW-h, 0.018%, 59.59 ppm, and 1419.03 ppm for brake thermal efficiency, brake specific fuel consumption, carbon monoxide, and unburnt hydrocarbons, respectively. Confirmation experiments aligned well with model predictions, indicating the potential of LHR engines to enhance thermal efficiency and reduce emissions.

Predict the characteristics of diesel engine using glycine max oil biofuel

Significant research is devoted to the transformation of Glycine max oil (soybean oil) into biofuel. An exhaustive investigation into the performance, combustion and emission analyses of glycine max oil biofuel (GMOB) in the context of optimization studies involving variable engine factors such as load, injector timing and so forth, has yet to occur. This study endeavors to fill the gap in the academic literature regarding comprehensive engine investigations of GMOB. In this study, five distinct mixtures of GMOBs are combined with diesel: DS1—0% biofuel with 100% diesel, DS2—5% biofuel with 95% diesel, DS3—20% biofuel with 80% diesel, DS4—40% biofuel with 60% diesel and DS5—100% biofuel and 0% diesel. Using standard ASTM limits, the properties of the biodiesel samples were evaluated and confirmed (the kinematic viscosity at 40°C for GMOB is 4.6 mm2/s, whereas that of unadulterated diesel is 3.0 mm2/s). Utilizing the combustion, emission and performance characteristics of a compression ignition engine, the blend, load and injection timing (IT) were optimized. At 100% load, an upward trend in indicated thermal efficiency is observed for both diesel and biofuel blends. Furthermore, the volumetric efficiency of all biofuel blends was enhanced through the implementation of advanced IT (24.5° b TDC). Additionally, smoke emission is observed to increase by 18.5°–24.5° b TDC across all mixtures. Biofuel mixtures exhibit a negligible minimum rate of pressure increase per degree.

Advancing RCCI engine performance via optimal acetylene premix ratios and advanced diesel injection timing: An experimental investigation

AbstractReactivity controlled compression ignition (RCCI) stands out as an innovative combustion strategy, effectively reconciling stringent emission regulations with precise combustion management and optimal engine performance. In this research, the influence of injection timing of diesel, acting as highly reactive fuel (HRF), alongside variable premix ratios of acetylene, a low reactive fuel (LRF), operating within the RCCI framework has been investigated. In a first‐of‐its‐kind attempt, with a thorough experimental design, the present investigation encompasses a progressive advancement of HRF injection timing, extending up to 110° CA bTDC with 20° CA increments, coupled with LRF integration at premix ratios of up to 70%. Optimal operational conditions materialize at an HRF injection timing advancement of 90° CA bTDC, complemented by a 40% LRF contribution. This configuration yields substantial gains, including a 28.2% upsurge in the cylinder pressure and an 18.6% elevation in the cylinder temperature compared to conventional diesel (CDC) operations. Additionally, the combustion process exhibits an advanced start of combustion (SoC) relative to the CDC baseline, with an 8.53% decline in heat release rate, at 40% LRF enrichment. Under optimal circumstances, moderate hydrocarbon (HC) emissions are noted, while smoke emissions experience a noteworthy reduction of 55.9%, all the while upholding overall output performance. A remarkable 69.8% peak increase in brake thermal efficiency is attained, underscoring the merits of judiciously advancing HRF injection timing and extending LRF utilization within the RCCI paradigm. Thus, the study underscores the synergistic potential between augmented HRF injection timing and controlled LRF integration, offering a promising avenue for elevating the RCCI approach.

Diesel-natural gas dual fuel injection strategy effects on engine ignition delay and cylinder pressure evolution

Diesel pilot high-pressure direct injection (HPDI) natural gas technology has been noticed and applied in medium and heavy-duty engines due to its outstanding economy and power performance. However, the combustion of two kinds of fuels will involve more injection parameters, which increases the difficulty of designing injection strategy and calibrating injection parameters. This paper investigates comprehensively the effects of three key engine injection parameters (injection timing, injection duration of the pilot diesel, interval of injection between diesel and natural gas) on the engine ignition delay and cylinder pressure evolution using the experimentation method, which are utilized to guide the design of injection strategy and optimize injection parameters. Results show that the maximum in-cylinder pressure and its position are determined by the injection timing of natural gas, but little affected by the injection parameters of diesel. As the injection timing advances and the duration of diesel injection shortens, the ignition delay increases. To avoid rough combustion in the cylinder, it is necessary to optimize the injection timing, injection interval, and ignition diesel injection duration to ensure that the pressure rise rate does not exceed the threshold.

Co-optimization of injection parameters and injector layouts for a methanol/diesel direct dual-fuel stratification (DDFS) engine

Direct dual fuel stratification (DDFS) is a promising combustion mode to achieve satisfactory engine performance with the effective control of ignition and combustion processes. In this study, a DDFS engine fueled with methanol and diesel was investigated at low loads based on a four-stroke light-duty naturally aspirated engine. Both injection parameters and injector layouts of the two fuels were co-optimized by the fast nondominated sorting genetic algorithm (NSGA-II). The results show that the fractions, injection timings, spray half-included angles, and injector positions of the two fuels all showed significant influences on engine performance. Finally, the high methanol fraction, advanced diesel injection timing, methanol injection timing near the top dead center, and large spray half-included angle of methanol were adopted in the optimal case to achieve both low EISFC and NOx simultaneously. Meanwhile, a centrally-mounted methanol injector was beneficial to shorten combustion duration, and the diesel injector can be arranged in a semicircle area with a radius of approximately 1.14 cm to provide the sufficiently high temperature for the complete combustion of methanol.

A study on the impact of fuel injection parameters and boost pressure on combustion characteristics in a diesel engine using alcohol/diesel blends

Engine researchers focused on alcohol fuels since the invention of diesel engines in the 1900s, and the rise in petrochemical costs in the 1970s triggered this concern. This study investigates the impacts of the injection start timing, pilot injection application, and boost air pressure increase, on combustion and exhaust emissions in a common rail diesel engine fueled with ethanol/butan-2-ol/diesel blends. The lowest combustion noise was obtained in the pilot injection application as 83.8 dB in E15B3. The results indicated that the peak point of cylinder gas pressure rose by more than 5 % in the application of pilot fuel injection and advanced injection timing, compared to conventional engine operating conditions. However, maximum CO2 and NOx were seen in the pilot injection application using FBDF as 5.7 % and 670 ppm, respectively. As alcohol rate increases in fuel blends, the average 1.3 °CA in the ignition delay period was increased, while the total combustion period was shortened more than 6 °CA. This result shows that the combustion reactions of alcohol/diesel fuels occur faster than pure diesel. However, the variation in the ignition delay and total combustion periods of the test fuels considerably reduced with pilot fuel injection application. These results indicates that pilot fuel injection may be applied very controlled according to changing engine conditions. It was calculated in statistical analysis that except for the coefficient variation of the maximum pressure increase rate, the other coefficient variation values were relatively stable and below 3 %. In addition, it was determined that the results of the finite element analysis are proportional to the pressure values obtained experimentally.

Experimental Characterization of Hydrocarbons and Nitrogen Oxides Production in a Heavy-Duty Diesel–Natural Gas Reactivity-Controlled Compression Ignition Engine

Reactivity-Controlled Compression Ignition (RCCI) combustion is considered one of the most promising Low-Temperature Combustion (LTC) concepts aimed at reducing greenhouse gases for the transportation and power generation sectors. Due to the spontaneous combustion of a lean, nearly homogeneous mixture of air and low-reactivity fuel (LRF), ignited through the direct injection of a small quantity of high-reactivity fuel (HRF), RCCI (dual-fuel) shows higher efficiency and lower pollutants compared to conventional diesel combustion (CDC) if run at very advanced injection timing. Even though a HRF is used, the use of advanced injection timing leads to high ignition delays, compared to CDC, and generates high cycle-to-cycle variability, limited operating range, and high pressure rise rates at high loads. This work presents an experimental analysis performed on a heavy-duty single-cylinder compression ignited engine in dual-fuel diesel–natural gas mode. The objective of the present work is to investigate and highlight the correlations between combustion behavior and pollutant emissions, especially unburned hydrocarbons (HC) and oxides of nitrogen (NOx). Based on the analysis of crank-resolved pollutants measurements performed through fast FID and fast NOx systems under different engine operating conditions, two correlations were found demonstrating a good accordance between pollutant production and combustion behavior: Net Cyclic Hydrocarbon emission—cyclic IMEP variations (R2 = 0.86), and Cyclic NOx—maximum value of the Rate of Heat Released (R2 = 0.82).

Influence of injection strategies on ignition patterns of RCCI combustion engine fuelled with hydrogen enriched natural gas

The depletion of fossil fuel and the concerns for harmful emissions and global warming has instigated researchers to use alternative fuels. Hydrogen (H2) and natural gas (NG) are attractive fuels for internal combustion engines. The dual-fuel combustion strategy is promising to reduce emissions with efficient engine operation. The concern for using NG in this strategy is the lower efficiency at low load conditions and the emission of exhaust gases like carbon monoxide and unburnt hydrocarbon. Mixing fuel with a wide flammability limit and a faster burning rate with NG is an effective method to compensate for the limitations of using NG alone. Hydrogen (H2) is the best fuel added with NG to cover NG limitations. This study investigates the in-cylinder combustion phenomenon of reactivity-controlled compression ignition (RCCI) engines using hydrogen-added NG as a low-reactive fuel (H2 addition to NG on a 5% energy basis) and diesel as a highly reactive fuel. The numerical study was done on a 2.44 L heavy-duty engine using CONVERGE CFD code. Three low, mid, and high load conditions were analyzed in six stages by varying the diesel injection timing from −11 to −21 O after top dead centre (ATDC). The H2 addition to NG had shown deficient harmful emissions generation like carbon monoxide (CO) and unburnt hydrocarbon with marginal NOx generation. At low load conditions, the maximum imep was achieved at the advanced injection timing of −21OATDC, but with the increase in load, the optimum timing was retarded. The diesel injection timing varied the optimum performance of the engine for these three load conditions.

Parametric study of GNPs nano addition in water diesel emulsified fuel on diesel engine at variable injection timings

ABSTRACT The current investigation is to determine the influence of graphene nanoplatelets (GNPs) in Water Diesel Emulsified Fuel (WDEF) of a compression ignition (CI) engine by changing injection timing (IT). The WDEF includes 94% diesel, 5% water, and 1% QPAN-80 and is referred to as D94W5Q1. For better stability, GNPs are added to D94W5Q1 at different doses (30, 60, and 90 ppm) utilizing ultrasonication, and the samples are referred to D94W5Q1-GNPs30, D94W5Q1-GNPs60, and D94W5Q1-GNPs90. The samples were run on a diesel engine at a uniform speed, fixed compression ratio (CR), and IT of 1500 rpm, 18:1, and 23°bTDC. The lower emissions of hydrocarbons (HC), carbon monoxide (CO), nitrogen oxide (NOx), and smoke were observed to be 61.72, 51.16, 48.45, and 25.51%, respectively, and enhanced Brake thermal efficiency (BTE) of 1.95% resulted for D94W5Q1-GNPs60, which is determined as an optimum blend. This optimum blend was evaluated further at various ITs of 19, 21, 23, and 25°bTDC, and the experimental values demonstrated higher BTE, in-cylinder pressure (CP), and heat release rate (HRR) of 3.49, 9.13, and 4.64% respectively, and reduced Brake Specific Fuel Consumption (BSFC) of 3.08%. Furthermore, the emissions were decreased for HC, CO, and smoke by 5.84, 22, and 8.91%, respectively, but the NOx value was raised by 3.01% at 25°bTDC. Finally, the D94W5Q1-GNPs60 blend at advanced IT enhances the overall engine performance.