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New challenges posed to internal combustion engines require a fresh approach and the application of modern simulation methods. This study focuses on the numerical analysis of the co-combustion process of diesel fuel with butyl alcohol in a dual-fuel, self-ignition internal combustion engine based on a three-dimensional engine model developed in AVL Fire software. The influence of butanol content, ranging from 0 to 60 %, on engine performance and emissions was investigated. Increasing the amount of butyl alcohol burned with diesel fuel leads to a delay in ignition, decreases maximum cylinder pressure and temperature, and increases the rate of pressure rise and heat release rate. For alcohol content of 20 % and 40 %, there is an increase in pressure and indicated power compared to diesel fuel alone. The addition of butanol to diesel fuel reduces the specific emissions of nitrogen oxides and Soot in the dual-fuel engine. The most favorable case was with a 40 % butanol content. For DB40, the highest IMEP (0.69 MPa) and Ni (10.37 kW) values were obtained, along with the highest TE efficiency (43.64 %). In comparison to D100, lower NO and Soot emissions were achieved for this case by 35 % and 65 % respectively. [ABSTRACT FROM AUTHOR]

Fossil fuel extraction and utilization are associated with several environmental issues. This study examined how altering the blending proportions of mixed diesel/biodiesel/n-butanol fuels impacts combustion. Additionally, it delved into the functioning of diesel engines when utilizing these blended fuels as well as conventional diesel. A three-dimensional fluid dynamics simulation was constructed and corroborated against test outcomes obtained at 25%, 50%, 75%, and 100% loads. The findings indicated that the n-butanol addition enhanced the indicated thermal efficiency. At a 100% load, D70B30 (70% diesel + 30% biodiesel), D70B25BU5 (70% diesel + 25% biodiesel + 5%N-butanol), D70B20BU10, and D70B10BU20 exhibited 4.76%, 5.75%, 6.79%, and 8.71% higher indicated thermal efficiency values than D100 (100% diesel), respectively. The introduction of butanol enhanced the combustion environment within the combustion chamber. Compared with pure diesel, all blended fuels reduced hydrocarbon and carbon monoxide emissions across various loads. The blended fuels showed significant reductions in hydrocarbon emissions of 1%, 4%, 6%, and 15% compared with that of diesel under the 25% load, respectively. [ABSTRACT FROM AUTHOR]

The goal of this study is to see how greater the exhaust gas recirculation (EGR) and quaternary blend approach affect the performance, emission, and combustion parameters of a Common Rail Direct Injection (CRDI) engine with various quaternary blends. In this study, we will use bio-fuels in replacement of diesel by 30–40% that emits less oxides of nitrogen (NOx) and soot. In light of this, combustion, exhaust emissions, and performance parameters of 1-cylinder CRDI engine powered by quaternary blends (QB) of diesel, vegetable oil, biodiesel, and 1-butanol by volume% were explored experimentally. To determine the effect on engine characteristics, with no EGR, 6% EGR and 12% were evaluated with various blends and base fuels. At peak load with 12% EGR, the experimental examination revealed a 2-percent decline in brake thermal efficiency (BTE), a small rise of 3.8% in brake-specific fuel consumption (BSFC) among blends in performance. In emissions, 12% EGR rate reported best results, i.e. average of 54% NOx reduction among blends, 14% rise in hydrocarbon (HC) and carbon monoxide (CO) at full load. The maximum NOx reduction has been reported by QB3 blend at 12% EGR rate and at full load is 54%. EGR rate of 12% was helpful in decreasing NOx emissions in a greater extend while little sacrificing in HC and CO. [ABSTRACT FROM AUTHOR]

Butanol has good combustion properties and it can be a viable alternative fuel for automotive spark ignition engines due to its ability to improve energy and pollution performance. This paper analyses the influence of butanol content in gasoline blends on engine operation with a focus on operation stability, thermal efficiency and emissions. A Cielo Nubira A15MF engine type with four cylinders and a 1.5 L displacement was turbocharged and it was fueled with butanol in a blend with gasoline in percent's of 10% vol. and 15% vol. An operation regime of 2500 1/min speed and 55% engine load was used, at different dosages, at which the engine power remained constant. Regarding the engine fueled with butanol in a blend with gasoline, the operation stability was improved, especially when lean dosages were used; the dosages at which the thermal efficiency was higher are comparative to classic fueling. Concerning the use of lean dosages, the combustion duration decreases and the energetic engine performance was improved when butanol was used comparative to gasoline. When butanol was used, polluting emissions and emission with a greenhouse effect were reduced. The sharp reduction in NOx is highlighted in this paper. [ABSTRACT FROM AUTHOR]

The dual direct injection strategy can flexibly control the reactivity distributions and equivalence ratio, which shows a great potential in realizing clean and efficient combustion. However, the sprays' collision is inevitable when the fuel sprays are injected into the combustion chamber simultaneously owing to limited in-cylinder space, which is rarely investigated. The investigation aims to explore the atomization and combustion characteristics of collision between biodiesel and butanol sprays at different injection delay times of biodiesel (0, 0.5, 1, 1.5, 2 ms). Experiments are conducted in a constant volume combustion chamber. The collision spray and combustion images are captured by optical diagnosis techniques. Several macroscopic parameters are obtained, including spray behavior, spray area, ignition delay, ignition location, flame behavior, flame lift-off length, and natural luminosity intensity. Results show that the variation of injection delay time can effectively change the spray distribution and realize the concentration stratification. The liquid-phase diffusion region increases with an increased premixed charge of butanol spray, but the total evaporation time has a tiny difference. The sprays' collision can promote the ignition process, but the ignition location is slightly affected by the injection delay time of biodiesel. A trade-off relationship between the vapor-phase diffusion area and combustion characteristics is found. When the injection delay time exceeds 0.5 ms, a longer injection delay time can lead to a larger vapor-phase area, which causes smaller equivalent ratio, longer flame-off length, and lower luminosity intensity. However, a longer injection delay would lead to an uncomplete combustion of the n-butanol spray. At the experimental cases, the injection delay time of biodiesel should be 1/2–2/3 injection duration to realize complete combustion and small emissions. [ABSTRACT FROM AUTHOR]

Among oxygenated alternative fuels, n-butanol is considered as a promising alternative biofuel which can partially (or fully) replace conventional transportation fuels currently in use. However, before n-butanol can be commercially utilised, its fundamental combustion characteristics need to be fully understood. In this work, the effect of adding n-butanol on autoignition property of iso-octane was studied. Measurements of ignition delay times for the two blends of n-butanol proportions of 30% and 50% by mole weight were made in a Rapid Compression Machine for stoichiometric mixtures at 2.0 MPa and temperature range 651-918 K. n-butanol increased ignition delay times of iso-octane at lower temperatures and hence acted as an octane enhancer, while at higher temperatures delay times were reduced. In the intermediate temperatures there was visually no difference in delay times between the two blends. Throughout the temperature range studied, the delay times of both blends were much closer to those of pure n-butanol which suggests that the combustion chemistry of n-butanol was dominant over that of iso-octane. These results have shown that n-butanol can enhance fuel octane rating and therefore can potentially improve thermal efficiency of SI engines, whilst CI engines can benefit from the reduced delay times at higher temperatures. [ABSTRACT FROM AUTHOR]

The detailed mechanisms of n-heptane and n-butanol were reduced for the target condition of ignition delay time using the direct relationship diagram method based on error transfer, the direct relationship diagram method based on coupling error transfer and sensitivity analysis, and the total material sensitivity analysis method. The reduced n-heptane (132 species and 585 reactions) and n-butanol (82 species and 383 reactions) were used to verify the ignition delay time and concentrations of the major species, respectively. The results showed that the reduced mechanism has a good prediction ability for the ignition delay time. The predicted mole fraction results of the major species were in good agreement. These reduced mechanisms were combined to finally construct a reduced mechanism for the n-heptane/butanol fuel mixture, which included 166 species and 746 reactions. Finally, the reduced mechanism was used to simulate the HCCI combustion mode, and the results showed that the reduced mechanism can better predict the ignition and combustion timings of HCCI under different conditions and maintain the ignition and combustion characteristics of the detailed mechanism; this indicates that the mechanism model constructed in this study is reliable. [ABSTRACT FROM AUTHOR]

Using n-butanol as an alternative fuel can effectively alleviate the increasingly prominent problems of fossil resource depletion and environmental pollution. Combined injection technology can effectively improve engine combustion and emission characteristics while applying combined injection technology to n-butanol engines has not been studied yet. Therefore, this study adopted butanol port injection plus butanol direct injection mode. The engine test bench studied the combustion and emission performance under different direct injection ratios (NDIr) and excess air ratios (λ). Results show that with increasing NDIr, the engine torque (Ttq), peak in-cylinder pressure (Pmax), peak in-cylinder temperature (Tmax), and the maximum rate of heat release (dQmax), all rise first and then drop, reaching the maximum value at NDIr = 20%. The θ0-90 and COVIMEP decrease first and then increase as NDIr increases. NDIr = 20% is considered the best injection ratio to obtain the optimal combustion performance. NDIr has little affected on CO emission, and the NDIr corresponding to the lowest HC emissions are concentrated at 40% to 60%, especially at lean burn conditions. NOx emissions increase with increasing NDIr, especially at N20DI, but not by much at NDIr of 40–80%. With the increase in NDIr, the number of nucleation mode particles, accumulation mode particles, and total particle decrease first and then increase. Therefore, the n-butanol combined injection mode with the appropriate NDIr can effectively optimize SI engines' combustion and emission performance. [ABSTRACT FROM AUTHOR]

Alcohols are oxygenated renewable fuels responsible for low carbon emission and high H/C ratio. In the present study, a blend of methanol, ethanol, and n-butanol in equal proportion by volume (E-MEBANOL) is tested as a sustainable fuel for SI engines under variable compression ratio (CR) and ignition timing (SOI). The performance of the engine is found to improve by increasing CR as well as advancing the SOI, as the brake power (BP), brake thermal efficiency (BTE), and volumetric efficiency are found to increase by increasing CR to 15 from 11 at an advanced SOI of 24°CA before top dead center (BTDC) from 16°CA BTDC by 17.54%, 17.47%, and 10.53% respectively. Similarly, combustion is also enhanced with increasing CR and advancing SOI as the peak cylinder pressure (Pmax), and maximum net heat release rate (NHRmax) are found to increase by 60% and 27.64%, respectively, while positions of these peaks are advanced by 17°CA and 18°CA respectively by increasing CR from 11 to 15 and SOI advanced to 24°CA BTDC. The flame development period (CA10) increases with advancing SOI and decreases with increasing CR, while the flame development period (CA10-90) and total combustion duration decrease with both increasing CR and advancing SOI. The CO & HC emissions improve with increasing CR and advancing SOI, while NOx increases drastically, but EGT decreases continuously. [ABSTRACT FROM AUTHOR]

In recent years, the interest in renewable fuels has increased mainly due to regulations regulating the permissible limits of toxic components of exhaust gases emitted by reciprocating engines. This paper presents the results of a comparison of the effects of fueling a compression-ignition piston engine with a mixture of diesel fuel and n-butanol, as well as RME (Rapeseed Oil Methyl Esters) biodiesel and n-butanol. The tests were carried out for a constant load and a wide energetic share of fuels in the mixture. The main focus was on the assessment of combustion stability, the uniqueness of the combustion stages, and the assessment of the fuel type influence on the CA50 angle. The tests show that RME offers the possibility of efficient combustion with n-butanol with up to 80% energy share. The share of n-butanol has a positive effect on the engine's efficiency and very effectively reduces soot emissions. Without the influence on COVIMEP, the share of n-butanol up to 40% in the mixture with diesel fuel and up to 80% in the mixture with RME was recorded. Combustion of RME with n-butanol was more stable. The share of n-butanol in the mixture with diesel fuel caused an increase in NOx emissions, and co-combustion with RME caused a decrease in emissions. [ABSTRACT FROM AUTHOR]

The combustion and emission characteristics of n-butanol/coal-derived naphtha blends in homogeneous charge compression ignition (HCCI) combustion mode were experimentally researched on a retrofitted diesel engine. The effects of intake temperature (Tin) and excess-air coefficient (λ) were mainly analyzed. The results show that the peak in-cylinder pressure (Pmax) and peak heat release rate (HRRmax) of all tested fuels show an overall increasing trend as Tin rises. The combustion gets faster and more stable, carbon monoxide (CO) and hydrocarbon (HC) emissions decrease, and the indicated thermal efficiency (ITE) first increases and then decreases. When Tin remains constant, the Pmax and HRRmax decrease and the combustion phase delays as the n-butanol volume fraction increases; CO and HC emissions gradually increase, except for that of lower Tin, which shows a trend of first reduction and then increase. ITE gradually decreases in general, but when Tin is higher than 100°C, coal-derived naphtha containing 24% of n-butanol in volume (B24N76) exhibits the highest ITE. In addition, for all tested fuels, both Pmax and HRRmax decrease as λ increases and the combustion gets slower and less stable; CO and HC emissions deteriorate, and ITE gradually decreases. It is worth noting that B24N76 shows the best combustion stability for all λs and exhibits the lowest CO and HC emissions when λ are 3.0 and 3.5. [ABSTRACT FROM AUTHOR]

The n-butanol/n-octanol fueled reactivity-controlled compression ignition engine was numerically studied based on the KIVA-CHEMKIN code. First, the knocking combustion characteristics were analyzed while functioning with a premixed n-butanol percentage of 20% (B20), since it exhibited the most severe knocking. Ten local regions were monitored to obtain local data, such as pressure and heat release rate. The local pressure oscillation was quantified by a band-pass filter. Second, the premixed n-butanol percentage and the intake valve close (IVC) timing were varied to investigate their effects on the combustion characteristics and emissions formations, as well as their potential for mitigating knocking. The results showed that a strong pressure oscillation was observed for B20 near the cylinder wall, which indicates severe knocking. This consequence is mainly caused by the low-temperature combustion of the n-octanol/n-butanol/air mixture near the cylinder-wall region. Increasing premixed n-butanol percentage and retarding IVC timing could result in an extended ignition delay, lowered peak pressure, and reduced maximum pressure rise rate (PRR). Condition B80 with an IVC timing of −126 °ATDC could improve the indicated mean effective pressure by 11.7% and reduce the maximum PRR by 63.4% when compared to condition B20. [ABSTRACT FROM AUTHOR]

Hydrogen and n-butanol are superior alternative fuels for SI engines, which show high potential in improving the combustion and emission characteristics of internal combustion engines. However, both still have disadvantages when applied individually. N-butanol fuel has poor evaporative atomization properties and high latent heat of vaporization. Burning n-butanol fuel alone can lead to incomplete combustion and lower temperature in the cylinder. Hydrogen is not easily stored and transported, and the engine is prone to backfire or detonation only using hydrogen. Therefore, this paper investigates the effects of hydrogen direct injection strategies on the combustion and emission characteristics of n-butanol/hydrogen dual-fuel engines based on n-butanol port injection/split hydrogen direct injection mode and the synergistic optimization of their characteristics. The energy of hydrogen is 20% of the total energy of the fuel in the cylinder. The experimental results show that a balance between dynamics and emission characteristics can be found using split hydrogen direct injection. Compared with the second hydrogen injection proportion (IP2) = 0, the split hydrogen direct injection can promote the formation of a stable flame kernel, shorten the flame development period and rapid combustion period, and reduce the cyclic variation. When the IP2 is 25%, 50% and 75%, the engine torque increases by 0.14%, 1.50% and 3.00% and the maximum in-cylinder pressure increases by 1.9%, 2.3% and 0.6% respectively. Compared with IP2 = 100%, HC emissions are reduced by 7.8%, 15.4% and 24.7% and NOx emissions are reduced by 16.4%, 13.8% and 7.9% respectively, when the IP2 is 25%, 50% and 75%. As second hydrogen injection timing (IT2) is advanced, CA0-10 and CA10-90 show a decreasing and then increasing trend. The maximum in-cylinder pressure rises and falls, and the engine torque gradually decreases. The CO emissions show a trend of decreasing and remaining constant. However, the trends of HC emissions and NOx emissions with IT2 are not consistent at different IP2. Considering the engine's dynamics and emission characteristics, the first hydrogen injection proportion (IP1) = 25% plus first hydrogen injection timing (IT1) = 240°CA BTDC combined with IP2 = 75% plus IT2 = 105°CA BTDC is the superior split hydrogen direct injection strategy. [Display omitted] • The injection mode is n-butanol port injection plus split hydrogen direct injection. • The increased percentage of second hydrogen injection increases the torque. • Split hydrogen injection owns a shorter combustion process than a single injection. • Split hydrogen injection yields lower HC emissions than single hydrogen injection. • Reducing the ratio of second hydrogen injection can reduce NOx emissions. [ABSTRACT FROM AUTHOR]

The study includes the use of alcohols in conjunction with diesel as a binary fuel and biodiesel. In addition, this study was conducted on quaternary fuels (premium diesel, waste cooking biodiesel, n‐butanol, and bioethanol), including Fe3O4 (iron(III) oxide)‐doped reduced graphene oxide (rGO) nanocomposite to reduce the use of fossil fuels, their cost, and energy demand. It includes 10% bioethanol, 5%–20% n‐butanol, 25 ppm Fe3O4‐doped rGO nanocomposite, and 20% and 100% waste cooking biodiesel, all of which have been tested in a diesel engine to ensure that they are suitable for use. The findings were compared to those obtained with premium diesel, ranging from 50% to 100% at full engine load conditions. In comparison to 100% premium diesel fuel, the fuel blend (Blend G) had 37.50% brake thermal efficiency and 0.46% (brake‐specific energy consumption), as well as lower rates of 316.2% carbon monoxide, 198.80% hydrocarbon, and 80.01% smoke with 28.10% higher oxides of nitrogen (NOx). Adding 20% n‐butanol to premium diesel, as well as waste cooking biodiesel, bioethanol, and Fe3O4‐doped rGO nanocomposite fuel blends, was used in this study to improve the performance of the diesel engine and reduce some of the NOx emissions. In the near future, these fuel blends may be a viable alternative combination for the diesel engine. [ABSTRACT FROM AUTHOR]

To achieve carbon neutrality goals, renewable alcohols and new technologies are receiving increased attention. Variable valve technology can effectively improve engine efficiency. However, there is limited research on valve strategies suitable for alcohol. To further promote the efficient and clean application of alcohol, this article studies the effects of intake valve timing and lift on performance of ethanol, n-butanol, and gasoline engines under stoichiometric combustion and lean burn. It is found that the combustion process of ethanol and n-butanol is prolonged by advancing intake valve timing, while gasoline is the opposite. Meanwhile, the improvement of equivalent brake-specific fuel consumption (ESFC) is the most significant when fueled with gasoline, improving by 6.9 %. The improvement of BSNOx is the highest when fueled with ethanol, improving by 42.07 %. Adjusting intake valve lift has a weaker impact on economy than valve timing. However, when adjusting the combination of throttle, valve lift and timing, the ESFC of ethanol, n-butanol, and gasoline can be reduced by 6.79 %, 4.35 %, and 10.98 %. Furthermore, combining valve timing and lean burn can further improve economy and emissions. The ESFC of ethanol, n-butanol, and gasoline can be decreased by 12.73 %, 6.87 %, and 11.96 %, while BSNOx decrease by 93.69 %, 74.86 % and 61.65 %. [Display omitted] • Variable intake valve adjustment strategies were achieved through a self-developed VVA mechanism. • Study the effect of intake valve strategy on high compression ratio SI engine fueled with ethanol, n-butanol, and gasoline. • N-butanol achieves the lowest BSNOx under the combination of intake valve timing and lean burn strategy. • Ethanol has the best combustion stability under the combination of intake valve timing and lean burn strategy. • Regardless of the strategy, ethanol maintains the fastest combustion rate. [ABSTRACT FROM AUTHOR]

In order to meet the requirements of Sustainable Aviation Fuel (SAF) to achieve the imperatives of energy conservation and emission reduction. This paper compares the combustion characteristics of diesel, RP-3/n-butanol blends in terms of heat release rate, in-cylinder pressure, temperature and fuel economy in a compression ignition engine, taking into account the advantages of lightweight structure, low fuel consumption and wide range of applications of aviation piston engines. The results certified the viability of applying RP-3 and RP-3/n-butanol blends in diesel engines. Adding n-butanol prolonged the ignition delay and shorten the combustion duration. Moreover, the peak of the pressure, temperature and apparent heat release rate (AHRR) increased. In addition, the blended fuel showed obvious diffusion combustion characteristics at high load. With the n-butanol increased, the combustion instability of the blended fuels decreased significantly, at low load. At n = 2400r/min, pme = 0.53 MPa, compared with diesel, the maximum heat release rate (MHRR) of R70B30 increased by 76.6 %, improving the combustion characteristics of the blended fuel. Moreover, the equivalent specific fuel consumption (ESFC) of RP-3 is 5.56–14.83 % lower than that of diesel, and the effective thermal efficiency (ETE) of RP-3 is 2.8–13.46 % higher than that of diesel under most working conditions. • The n-butanol/RP-3 blended fuels can replace diesel fuels in compression ignition engines. • The n-butanol improves the combustion difficulties at low load. • The blended fuel shows obvious diffusion combustion characteristics at high load. • Using n-butanol as blended fuel can shorten the combustion duration. [ABSTRACT FROM AUTHOR]

• Dual-fuel spray impingement in inert and combustion environments are investigated. • Dual-fuel spray impingement forms the concentration and reactivity stratification. • Larger impingement angle reduces the spray evaporation and temperature distribution. • High injection pressure increases the temperature distribution due to better fuel-gas mixing. Dual-fuel spray impingement is an important means to realize the reactivity and concentration stratification in dual direct injection engines. In the present study, the dual-fuel (biodiesel and n-butanol) spray impingement in inert and combustion environments was experimentally and numerically investigated. The mixture concentration distribution and ignition characteristics were analyzed. The results show that as the biodiesel and n-butanol sprays impinge with each other, the overall equivalence ratio reaches maximum value around the initial impingement region and decreases outwardly, forming the concentration and reactivity stratification. Biodiesel has a slower evaporation rate but a faster reaction rate than n-butanol. As the impingement angle increases, the spray area after the collision decreases, and the low-temperature region and high-equivalence ratio region are more concentrated, reducing the spray evaporation and temperature distribution. Conversely, increasing the injection pressure can enhance the mixing between spray and ambient gas and increase the temperature distribution. [ABSTRACT FROM AUTHOR]

The shortage-inflation of fossil fuels and aggravation of pollution intensity have initiated the search for innovative biofuel blends. Binary and Ternary fuels are studied for a long time. The use of biodiesel/vegetable oil up to 5–20% can replace fossil fuel with little modification in engine. However, to replace fossil fuel dependence up to 30–40% with little or no modification in engines is a challenge to researcher. This can be approached to evaluate a novel biofuel mix pattern called optimum Quaternary Blend by the experimental investigation. The main objective of the present research is to replace conventional Diesel with biofuels 30–40% with innovative fuel mix and lesser NOx-soot emission. In view of this, experimentally investigated combustion, emission, and performance behavior of single cylinder Common Rail Direct Injection (CRDI) engine fueled by quaternary blends combination of diesel (60–70 vol %), vegetable oil (Cotton Seed Oil – 5 vol% fixed), biodiesel (Mahua Biodiesel 5–25 vol %), and bio-alcohol (n-butanol 10–25 vol %). Further, to compare engine characteristics with D100% and D50B50%. Engine performance measures like brake thermal efficiency, specific energy consumption, emissions, and combustion characteristics such as rate of pressure rise (RPRR), combustion duration, CA50, CA90, mean gas temperature, combustion-chamber pressure, and net heat release rate are studied. It is noted that Diesel 60%, cotton seed oil 5% with mahua biodiesel 15–20%, and n-butanol 20–15% showed superior quaternary blend among all fuels. This optimum quaternary blend QB3-QB4 showed relatively higher brake thermal efficiency 8% more at lower specific energy consumption 10 MJ/kg about 29% less compared to other blends. Also, controlled combustion with rate of pressure rise 8.6 bar/deg CA about 14% less compared to other fuels. The NOx 10% less and smoke 2% less reported by optimum quaternary blends QB3 compared to other blends. However, CO emissions are noted least with marginal penalty in HC emissions. [ABSTRACT FROM AUTHOR]

A n‐butanol reduced mechanism (60 species and 306 reactions) was developed using the direct relation graph with error propagation and isomer lumping methods. Sensitivity analysis (SA) was then performed to identify reactions that were sensitive to the ignition delay (ID) for the adjustments of the pre‐exponential factor to replicate the experimental ID times. As compared with the experimental measurements at initial temperatures of 343–1350 K, initial pressures of 0.02–80 bar, and equivalence ratios of 0.5–2.0, the maximum deviation for the predictions by the n‐butanol reduced mechanism was at 37.75% for the ID times, 8 cm/s for the laminar flame speed, and a factor of three for both the species concentration profiles under jet‐stirred reactor and premixed laminar flame. Furthermore, a maximum deviation of 2.5 crank angle degrees in combustion phasing was obtained when the reduced mechanism was benchmarked against the detailed mechanism under homogeneous charge compression ignition (HCCI) conditions at initial temperature of 413 K, initial pressure of 1 bar, and equivalence ratios of 0.5–2.0. Despite these deviations, the low temperature IDs and the laminar flame speed predicted by the present reduced mechanism were in better agreement to the experimental measurements than the existing n‐butanol reduced mechanisms of comparable sizes. Hence, this collectively indicates that improvements were made to the present reduced mechanism, particularly for the low‐temperature reactions. The n‐butanol reduced mechanism was also compared with gasoline and diesel surrogates under 0D HCCI simulations. The results indicate that the combustion characteristics of n‐butanol is closer to gasoline than to diesel. This suggests that n‐butanol could safely replace gasoline fuel in neat form while it is more suitable to be blended with diesel fuel to maintain engine performance and prevent any adverse effects on the engine. [ABSTRACT FROM AUTHOR]

In this study, the ignition and combustion characteristics of fast pyrolysis bio-oil (FPBO) are investigated in a combustion research unit (CRU), which mainly consists of a constant-volume combustion chamber. To fuel the CRU with FPBO, n-butanol and 2-ethylhexyl nitrate (EHN) are used to improve the atomization and ignition properties of the fuel blends, respectively. In the first part of this study, an appropriate proportion of EHN additive into n-butanol is determined based on the balance between the ignition improvement and the amount of EHN addition. Then, the effects of FPBO content (up to 30%) in FPBO/n-butanol blends with the same EHN addition are investigated. The effects of chamber wall temperature on the combustion are also studied. Finally, the different definitions of indicators are determined from the chamber pressure traces to quantitatively depict fuel ignition and combustion characteristics including ignition delay, combustion phasing, end of combustion and burn duration. Experimental results show that a distinct two-stage ignition process can be observed for all cases. For n-butanol with added EHN, the increase of EHN proportion could effectively advance both the low- and high-temperature reaction phases. However, this gain is obviously reduced when the percentage of EHN becomes higher than 8%. For FPBO/n-butanol blends with an addition of EHN, higher FPBO proportions have little effect on the low-temperature reaction phase, while they delay the high-temperature reaction phase. Chamber wall temperature have a significant influence on the ignition and combustion processes of the tested FPBO/n-butanol blends. With these blends, negative temperature coefficient behavior was observed in a chamber wall temperature range of 535–565°C.

In recent years, the interest in renewable fuels has increased mainly due to regulations regulating the permissible limits of toxic components of exhaust gases emitted by reciprocating engines. This paper presents the results of a comparison of the effects of fueling a compression-ignition piston engine with a mixture of diesel fuel and n-butanol, as well as RME (Rapeseed Oil Methyl Esters) biodiesel and n-butanol. The tests were carried out for a constant load and a wide energetic share of fuels in the mixture. The main focus was on the assessment of combustion stability, the uniqueness of the combustion stages, and the assessment of the fuel type influence on the CA50 angle. The tests show that RME offers the possibility of efficient combustion with n-butanol with up to 80% energy share. The share of n-butanol has a positive effect on the engine’s efficiency and very effectively reduces soot emissions. Without the influence on COVIMEP, the share of n-butanol up to 40% in the mixture with diesel fuel and up to 80% in the mixture with RME was recorded. Combustion of RME with n-butanol was more stable. The share of n-butanol in the mixture with diesel fuel caused an increase in NOx emissions, and co-combustion with RME caused a decrease in emissions.

Intelligent Charge Compression Ignition (ICCI) combustion mode is a novel dual-fuel combustion strategy that has been proposed recently. In ICCI combustion mode, two fuels with different reactivity are directly injected during the intake stroke and compression stroke, respectively, to achieve flexible reactivity gradient and equivalence ratio stratification. In this study, experiments were conducted on a single-cylinder diesel engine to investigate the effects of butanol direct injection strategies on the engine running with ICCI combustion mode at a constant speed of 1500 r/min and medium load. Results showed that ICCI combustion mode was composed of premixed heat release and diffusion heat release. In compare, the percentage of premixed heat release was higher than the diffusion heat release. With fixed biodiesel direct injection timing (SOI2), retarding butanol single injection timing (SOI1) would delay combustion phasing while not distinctively affect ignition timing. SOI1 showed significant effect on the thermal efficiency and engine emissions. Indicated thermal efficiency (ITE) decreased at first and then slightly increased with retarding of SOI1, while the nitrogen oxides (NOx) emissions were always at low levels. As the butanol second direct injection timing (SOI1-2) retard and the corresponding energy ratio increase, more butanol entered into the crevice/squish regions, leading to the increase of unburned hydrocarbon (HC) and carbon monoxide (CO) emissions. EGR strategy helps to significantly reduce NOx emissions without affecting ITE although penalized HC and CO emissions are resulted in. The optimum butanol direct injection strategies were butanol single direct injection, especially in the early SOI1, in which the thermal efficiency was higher and emissions were at very low levels (NOx < 0.4 g/kW h). [ABSTRACT FROM AUTHOR]

The impact of injection timings on the in-cylinder flow field intensity, mixture formation process, combustion, and emission characteristics are analyzed. The range of injection timing is set between −320°CA and −260°CA. The research results indicate: Delaying the injection timing causes the spray plumes increasingly align with the tumble direction, consequently enhancing the in-cylinder tumble intensity and the turbulence near the spark timing. The mixture homogeneity is influenced by both the formation time and the in-cylinder flow field intensity. Moreover, combustion performance is linked to the homogeneity of the mixture and turbulence intensity near the spark timing. Despite the fact that postponed injection may augment both turbulence intensity and the equivalent ratio around the spark plug at the moment of spark, achieving higher explosion pressure, but the higher viscosity of n-butanol impedes droplet break-up, and its low volatility decelerates the evaporation rate, leading to poorer mixture homogeneity, reduced BMEP, and increased CO and soot emissions. However, at −300°CA start of injection, the extended mixing time optimizes the fuel-air mixture homogeneity, thus improving combustion quality and reducing CO, soot, and HC emissions, albeit leading to increased NOx emissions. • This research examines the process of mixture formation, combustion, and emission performance of n-butanol, which is characterized by higher dynamic viscosity，surface tension and lower volatility. • As the injection timing gets postponed, there is a simultaneous increase in both the in-cylinder tumble ratio and turbulence at the ignition moment. • Mixture homogeneity is dictated by the combination of mixture formation time and in-cylinder flow field intensity. • Earlier injection results in superior mixture homogeneity, thereby achieving improved combustion and emission performance. [ABSTRACT FROM AUTHOR]

The study aims to evaluate the combined effects of alcohols as additives to diesel and exhaust-gas recirculation (EGR) on combustion and emission characteristics of a common-rail diesel engine. Tested fuels were prepared with 25% ethanol, 25% n -butanol, 25% n -pentanol, and 50% n -pentanol by volume, referred to as E25, B25, P25, and P50, respectively. The effects of different alcohol contents and a wide range of EGR ratios on combustion and emissions characteristics, especially particulate emissions, were investigated. The results demonstrate that with EGR ratios increasing, for each fuel, the peak of cylinder pressure decreases and the peak of heat release rate increases, both of which are delayed. The premixed combustion phase of alcohol/diesel blends is larger than that of pure diesel. Furthermore, alcohol contents and EGR ratios have obvious effects on indicated thermal efficiency (ITE). ITE increases after the addition of alcohol to diesel, but falls as EGR increases. Regarding emissions, the particulate number concentration of each fuel shows a unimodal distribution versus particulate size. At low and medium EGR ratio situation (<40%), the peak particulate number concentration increases quickly and the particulate size grows larger with increased EGR ratios. The total particulate number concentrations (TPNCs) of alcohol/diesel blends are much lower than pure diesel except for n-pentanol/diesel blends. But when EGR ratio continually increases, the peaks of particulate number concentration and the particulate size decrease. For almost all EGR ratios, the TPNCs of P25 and P50 are much higher than those of E25 and B25. [ABSTRACT FROM AUTHOR]

This paper tested one cylinder of a modified light-duty 4-cylinder diesel engine to study the coupling effect of 1.8-bar pressure and oxygen concentration (Coxy) on the combustion process of diesel (B00), diesel/n -butanol (B20) and diesel/n-butanol/2-ethylhexyl nitrate (B20+EHN), with emphasis on the analysis of the influence of combustion state parameters on emission generation. The research results showed that the difference between B00 fuel and B20 fuel in hydrocarbon (HC) and CO emissions was caused mainly by the combustion duration (CD) when the gas circuit concentration was 12%–17%, whereas when the gas circuit Coxy was 9%–12%, the HC and CO emissions were the result of the combined action of the two factors of in-cylinder combustion temperature (IT) and CD. The main influencing factor of NOx emission difference was IT. However, the main influencing factor of soot emission difference at 11%–17% gas circuit Coxy was the ignition delay period (ID), and at 9%–11% gas circuit Coxy it was the in-cylinder combustion temperature. Further research on the emissions difference between B00 fuel and B20+EHN fuel showed that ID plays a decisive role in the reduction of HC and CO emissions. [ABSTRACT FROM AUTHOR]

Owing to its physicochemical similarities with gasoline and renewable nature, n-butanol (bio-butanol) has garnered significant researcher interest. However, the lower atomization and volatility of n-butanol pose challenges when implemented in direct-injection spark-ignition (DISI) engines, leading to inhomogeneous air-fuel mixtures which subsequently results in a deterioration of combustion performance and an uptick in pollutant emissions. This study uses numerical simulations to examine the effects of injection pressure and timing on mixture formation, combustion, and emission characteristics in n-butanol DISI engines. The results indicate that for n-butanol, characterized by its reduced volatility and atomization capabilities, enhancing injection pressure from 10 MPa to 20 MPa effectively improves combustion and emission performance. However, the benefits taper off with subsequent increases in pressure. At injection pressure of 20 MPa, optimizing injection timing offers better combustion and emission results than merely increasing injection pressure. An early injection, represented by −300°CA start of injection, provides extended evaporation and mixture diffusion, significantly improving mixture quality and resulting in better combustion and emission outcomes. At −260°CA start of injection, while peak in-cylinder pressures can be achieved more favorably, the resultant inhomogeneous in mixture distribution results in increased emissions of CO, soot, and HC. • Effect of fuel injection pressure and timing are studied. • The fuel used is n-butanol, characterized by its lower volatility and atomization properties. • Early injection is more conducive to forming a homogeneous air-fuel mixture. • Raising the injection pressure from 10 MPa to 20 MPa significantly improved combustion and emission performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preliminary simplified mechanism of n-butanol was constructed by decoupling methodology. • The comprehensive sensitivity evaluation method was carried out. • SFLA was reported to optimize the reaction rate constant for the first time. • A compression factor and an acceleration factor were introduced to the algorithm. • The reliability of the optimized mechanism was verified. Using n-butanol as an alternative fuel has remained a key approach for diesel engines to improve combustion performance and minimize CO and Soot emissions. Herein, to investigate the ignition and combustion behavior of n-butanol, the preliminary simplified mechanism of n-butanol was established by decoupling methodology. Then, the Shuffled Frog Leaping Algorithm (SFLA) was employed for the first time to optimize the rate constants, whereas a comprehensive sensitivity evaluation (CSE) method to identify the reaction and working condition to be optimized was offered. To assess the performance of optimized mechanism, the predicted ignition delay time (IDT), species concentration and laminar flame speed were compared to the experimental data from multiple publications. The results reveal that the estimates based on this mechanism are in good agreement with experimental data. The combustion properties of n-butanol are effectively reconstructed by this method, and it is more computationally efficient than detailed chemical models. This study provides a new idea to construct the simplified mechanism and offers a theoretical basis for the application of n-butanol fuel. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • This paper mainly focus on the utilization of higher order alcohols in SI engines. • The blend proportion for the experimentation was 90:10 (gasoline:alcohols). • Analyzed performance, emission and combustion using different higher order alcohols. • Influence of blends based on location of hydroxyl ion present in the alcohol. Abstract In this research work, an attempt has been made to compare the performance and emission characteristics of n-butanol (n-B), iso-butanol (Iso-B), n-pentanol (P) and benzyl alcohol (Bn) with gasoline at various load conditions in the ratio of 10:90 by volume respectively, in a 2 cylinder SI test engine with MPFI technology. Alcohols were selected based on the position of hydroxyl (OH) group in its molecular structure, OH group was in straight chain for n-butanol and n-pentanol while it was branched chain for iso-butanol and finally OH group was chained with benzene ring for benzyl alcohol. The favorable outcome was that the performance of the fuel blends was noticeably higher than neat gasoline, with Bn10 blend giving greater fuel power at 100% load and P10, Bn10 and iso-B10 giving greater brake thermal efficiency. On the other hand, it was observed that the fuel consumption of n-B10 was higher than gasoline but iso-B10 gave lower fuel consumption comparatively. Considering pollutant emissions, all the blends gave lower HC, CO, & CO 2 emissions as compared to neat gasoline, although the NOx emissions increased with increasing loads. Considering both performance and emission characteristics it was finally concluded that benzyl alcohol – gasoline blend was better compared to other blends. [ABSTRACT FROM AUTHOR]

The n-butanol, an alcohol with chemical characteristics similar to gasoline, was evaluated experimentally in a spark ignition (SI) engine and through two-zone computer modelling. To do so, n-butanol was burned as a pure fuel and compared to hydrous ethanol, and a blend of n-butanol/ethanol was compared to a blend of gasoline/ethanol in order to evaluate combustion characteristics and engine performance. Experimental results have shown that n-butanol performed worse than hydrous ethanol, especially due to its lower octane number, which at 13.5:1 compression ratio and 7 bar BMEP tested gave advantage to the second alcohol fuel properties due to knock limitation. At the same test conditions, n-butanol blend showed similar engine efficiency parameters, such as indicated power, when compared to the gasoline blend, indicating that n-butanol is a potential surrogate for gasoline when blended with ethanol. In order to evaluate auto-ignition occurrence, an ignition sweep was done at a 9.5:1 compression ratio and 6 bar BMEP, showing that pure n-butanol had its performance rather limited by knocking combustion and cyclic variability, while its blend with ethanol was able to avoid sporadic knock, achieving a desired performance with stable combustion. • SI engine with stable performance using n-butanol and n-butanol/ethanol blend. • Two-zone model results showed very accurate fit to the experimental pressure data. • n-butanol can be a renewable fuel used as pure alcohol or blended with ethanol. • Similar knock occurrences for n-butanol and gasoline due to near RON and MON values. • n-butanol as a direct surrogate for Brazilian gasoline when blended with ethanol. [ABSTRACT FROM AUTHOR]

The effects of different n-butanol blending ratios (Rb) on the formation of propargyl radical (C3H3), an important benzene precursor, during the combustion of n-butanol/n-butane blends are studied. A detailed kinetic combustion model of n-butanol/n-butane is developed and the premixed n-butanol/n-butane flames are calculated at an equivalence ratio of 1.5, an initial pressure of 1.0 atm, and a temperature range from 800 to 2000 K in a perfectly stirred reactor (PSR), with Rb varying from 0 to 1.0. The results show that under the investigated conditions, the peak value of the mole fraction of C3H3 decreases non-linearly with the increase of Rb. Due to the interaction between combustion products of n-butane and n-butanol during the combustion process, the actual peak mole fraction of C3H3 is higher than the theoretical value. A rate of production (ROP) analysis reveals that the number of β-carbon atoms in the molecule of n-butane and n-butanol affects the efficiency of H-abstraction reactions in generating 2-butyl (sC4H9) and C4H8OH-3 (CH3–*CH–CH2–CH2–OH), which are the two major original sources of C3H3. For both n-butane and n-butanol, the main pathway of forming C3H3 from propene (C3H6) is basically the same, which is C3H6 → C3H5-a (symmetric allyl radical) → C3H4-a (allene) → C3H4-p (propyne) → C3H3. When Rb ranges from 0.4 to 0.6, the deviation degrees of the peak mole fraction of the involved C3 species reach a maximum, indicating that the interaction between the two fuels is the most significant. The non-linear decrease in the mole fraction of C3H3 can attribute to three reasons: (a) the increase of Rb promotes the increase of the conversion ratios of n-butane to sC4H9 and n-butanol to C4H8OH-3; (b) the contribution ratios of the reactions involved in the C3H5-a → C3H4-a → C3H4-p → C3H3 pathway decrease with increasing Rb; (c) C3H5-t (tertiary allyl radical) → C3H4-p → C3H3 is the secondary pathway for the formation of C3H3. With the increase of Rb, the dependence of C3H4-p on C3H5-t increases and the conversion ratio of C3H5-t to C3H4-p increases. This study investigates the non-linear decrease of the mole fraction of C3H3 by revealing the interactions between n-butanol and n-butane during the combustion, which can help better understand the effect of n-butanol on the formation of benzene. [ABSTRACT FROM AUTHOR]

Abstract Direct Injection of methyl oleate and PFI of n-butanol were used to conduct Reactivity Controlled Compression Ignition (RCCI) and minimize exhaust emissions in reference to conventional diesel combustion. Methyl oleate was investigated for validation of a single fatty acid methyl ester as a surrogate for biodiesel in engine operation. An experimental common rail engine was operated in RCCI and conventional diesel combustion modes under constant boost and similar combustion phasing. The RCCI strategy used two pulses of direct injections with a fixed first injection at 60° before top dead center and a varied second injection for smooth combustion. Ringing intensity was reduced by 70% for methyl oleate RCCI compared to diesel conventional diesel combustion. The molecular oxygen from methyl oleate allowed a reduction in soot by 75% and 25% compared to diesel in RCCI and conventional diesel combustion operation, respectively. Compared to conventional diesel combustion, NOx and soot decreased for RCCI by several orders of magnitude with both emissions approaching near zero levels at low load. The fuels produced a stable RCCI operation where mechanical efficiency was sustained within 2% for same-load points and the coefficient of variation of indicated mean effective pressure was limited to 2.5%. Highlights • NO x and soot emissions in RCCI mode approached near zero levels at low load. • Molecular oxygen from MO significantly reduced soot compared to ULSD RCCI and CDC. • RI decreased by 70% for methyl oleate RCCI due to the stratified high reactivity. • Combustion efficiency improved with MO use, relating to its unsaturated components. [ABSTRACT FROM AUTHOR]

Abstract In this study, waste cooking oil biodiesel was mixed with titanium dioxide (TiO 2), a metal-based nano particle, and n-butanol (C 4 H 9 OH) along with euro diesel to examine their effects on diesel engines. Various ratio of fuel blends were prepared with TiO 2 nano particles-diesel-biodiesel and n-butanol. The tests fuels were euro diesel (D100), biodiesel (B100), B20, B20 + TiO 2 , B20But10 and B20But10 + TiO 2 , respectively. Thermo-physical properties such as density, pour point, cloud point, cold filter clogging point, flash point and kinematic viscosity of all test fuels were determined followed by investigating engine performance parameters such as torque, power, fuel consumption and etc. Combustion analysis was also investigated. In addition, the effects on emissions such as CO, CO 2 , HC, NO and smoke opacity were also carried out. The addition of n-butanol to the fuel blends substantially affected density, kinematic viscosity and cold flow properties, while the addition of TiO 2 has not much effect on these properties. For all tested fuels, the maximum brake engine torque and power were recorded at approximately 1400 rpm and 2800 rpm, respectively. The addition of TiO 2 increased the brake engine torque and power 10.20% and 9.74% and decreased the brake specific fuel consumption 27.73% and 28.37%, respectively compared to blends without TiO 2 additive. TiO 2 additive increases the maximum cylinder pressure and heat release rate, as a result improved the engine performance and combustion. The addition of n-butanol in the fuel blend increased the maximum cylinder pressure and heat release rate values in comparison to euro diesel. The results of exhaust emission showed a decrease in CO, HC and smoke opacity emissions, whereas increased CO 2 and NO emission, except the use of n-butanol reduced the values of NO emission, in comparison to euro diesel and without TiO 2 additive. The results show that biodiesel produced from waste cooking oil, n-butanol and TiO 2 additive can be used in diesel engines at certain proportion and that the additive materials improve the combustion characteristics, engine performance and exhaust gas emission. [ABSTRACT FROM AUTHOR]

Scarcity and inflated cost of petroleum reserves along with environmental pollution concerns urged the researchers to identify a better alternative source of eco-friendly bio-energy. In this study, oxygenated biodiesel derived from Jojoba oil was used in a compression ignition engine to analyse the engine characteristics in the presence of multi-walled carbon Nanotubes (MWCNT) at 50 ppm, 100 ppm and 150 ppm concentrations. Taguchi's approach based experimentation identified the stability of modified fuel blends ratios of n-butanol, biodiesel and MWCNT. The Jojoba biodiesel was characterized using FTIR and GC MS techniques to understand the presence of fatty acid methyl esters in the biodiesel. Higher brake thermal efficiency and significant reduction in specific fuel consumption were observed in fuel blend with MWCNT. D70JJBD20O10CNT100 showed higher in-cylinder pressure and heat release rate due to micro-explosion of carbon nanotubes at full load condition. The ignition delay was also significantly affected with the addition of MWCNT. The exhaust emission like un-burned hydrocarbon, oxides of carbon, oxides of nitrogen and smoke exhibited noticeable variations with the modified fuel blends. [ABSTRACT FROM AUTHOR]

Direct injection (DI) of cotton seed biodiesel (CS100) with port fuel injection (PFI) of n-butanol was used for producing Premixed Controlled Compression Ignition (PCCI) to achieve low-temperature combustion (LTC) and obtain lower gaseous emissions in comparison to ULSD#2 (ultra-low sulfur diesel). PFI engine operation was compared to the combustion of binary mixtures of the same fuels reflecting the same weight ratio of high reactivity (CS100) and low reactivity (n-butanol) fuels. The supercharged engine was operated at constant speed and load with 20% exhaust gas recirculation (EGR). When compared to ULSD#2 reference, the ignition delay of 50% n-butanol and 50% CS100 binary mixture increased by 12% while the 50% n-butanol PFI with 50% CS100 DI led to a 17% decrease in ignition delay. Emissions of soot and nitrogen oxides were simultaneously improved using the PCCI strategy, reducing by 84% and 17%, respectively, given lower peak in-cylinder temperatures and increased oxygenation of the mixture. Carbon monoxide (CO) and unburned hydrocarbons (UHC) increased by several orders of magnitude as a downside of dual fuel injection; ringing intensity, however, improved, decreasing by 30% when using 50% n-butanol PFI in comparison to the ULSD#2 baseline given a smoother pressure gradients. Energy specific fuel consumption for CS50Bu50 (50% ULSD-50% n-butanol blend) increased by 4.5% compared to ULSD#2. The mechanical efficiencies and the coefficient of variation (COV) of IMEP were maintained at 70% and 2.5% respectively, during PCCI, indicating stable operation with renewable fuels. [ABSTRACT FROM AUTHOR]

n-Butanol is an option of biofuel with potential to be used in the transportation industry. There is little information about performance of engines running with this alcohol and thus is very difficult to evaluate its advantages. A way to bypass this limitation is to use numerical simulation, mainly 1D models, to represent the whole engine and preview its performance running with different fuels. The lack of information about n-butanol and its combustion properties are big challenges to surpass when building these virtual models. A way to overcome these challenges is numerically model an engine and adjust the fuel properties until the numerical results are in agreement with test results. The aim of this work is to estimate fuel properties of an n-butanol-gasoline blend by means of numerical simulation, allowing the comparison of its performance against other fuels. Starting with a virtual engine model, the fuel properties were adjusted based on test measurements until a good agreement between numerical results and measured results was obtained. After numerical calibration, some of the main n-butanol fuel parameters (BU40) needed by 1D codes were obtained, like liquid fuel heat of vaporization @ 298 K = 583 kJ/kg, density = 813 kg/m 3 , liquid fuel abs. entropy @ 298 K = 3015.78 J/kg-K, critical temperature = 563 K, critical pressure = 4.5 MPa, gaseous fuel abs. entropy @ 298 K = 4723.79 J/kg-K, among others. The properties thus obtained leaded to well approximated results, where numerical to experimental results for indicated mean effective pressure (IMEP) are lower than 0.1 bar, lower than 8% for peak cylinder pressure (PCP) and lower than 7% for rate of heat release (ROHR). [ABSTRACT FROM AUTHOR]

[Display omitted] • P m of OF m increased ∼ 2.9% compared to D under the full load. • BTEs of D m and OF m were noticed to be 5.5% and 3% higher than D. • CO, and UHC of OF m compared to D dropped by 49.1%, and 54.2% • OF m showed better performances and emission characteristics. The internal combustion engine type is widely used in diesel engines due to its energy efficiency. However, the use of conventional diesel has negative effects on human health and the environment. In an effort to find a more sustainable fuel option with less harmful emissions, the focus has shifted towards investigating the effects of hybrid nano additives, which are a combination of nonmetallic (graphene nanoplate) and metal oxide (TiO 2), on conventional diesel (D) and oxygenated fuels (OF). The engine test was conducted at 4 different loading cases with increments of 25% from 25% to 100% at a constant speed of 1500 rpm. The results showed that the modified fuels had superior combustion behaviors, such as peak in-cylinder pressure, combustion duration, and ignition delay, compared to conventional diesel and oxygenated fuels. The peak pressures in the cylinder of modified diesel (D m) and modified oxygenated fuel (OF m) under full load increased by 2% and 2.9%, respectively, compared to conventional diesel (D). Additionally, the brake thermal efficiencies (BTEs) of D m and OF m were found to be 5.5% and 3% higher than D under the same test conditions. In terms of emission analysis, the modified fuels demonstrated superiority over the conventional diesel and oxygenated fuels. During full load conditions, the CO, UHC, and NO emissions of OF m compared to D dropped by 49.1%, 54.2%, and 4%, respectively. The study results indicate that the use of a hybrid fuel additive consisting of nonmetallic (graphene nanoplate) and metal oxide (TiO 2) can significantly reduce harmful emissions and improve engine performance. [ABSTRACT FROM AUTHOR]

• Effects of n -butanol and ethyl ethanoate on diesel engine were investigated. • Up to 15% ethyl ethanoate concentration had stable engine operation. • Up to 20 % n -butanol concentration provided sufficient engine stability. • All fuel blends had minimal impact on peak pressure and HRR. • The blend EE15 reduced BSFC by 15.35% at 60% load. • All blends reduced NOx emissions, but CO and HC emissions increased. • At equal fuel mass, EE10.65 has 7.2% less NOx emissions than Bu10.65. Due to their numerous advantages, diesel engines remain the primary energy source for heavy machinery. In the present experimental study, the effect of oxyfuel type, oxygen content and blend volume on diesel engine performance, combustion and emission characteristics has been investigated. Experiments were carried out on seven fuel blends using a 4-stroke, single cylinder, direct injection combustion ignition (CI) engine at a constant speed of 2000 rpm and varying loads. Four-carbon alcohol (n -butanol) and ester (ethyl ethanoate) were separately blended with pure diesel (D100) at three blending ratios. For each fuel type, two blends were prepared to contain an approximate oxygen mass content of 2.2 % and 4.1 %, then a third blend containing 15 % additive volume ratio was also formulated. All tested blends had minimal effect on in-cylinder pressure and heat release rate (HRR). At low loads, up to 20.9 % rise in brake specific fuel consumption (BSFC) was recorded but EE15 (15 % ethyl ethanoate, 85 % diesel) achieved 15.35 % lower BSFC at 60 % load. NOx emissions reduced for all blends, with n -butanol blends achieving 30.6 % less NOx emissions compared to D100. However, CO emissions increased by up to 37.6 % for n -butanol and 32.9 % for ethyl ethanoate. Considering engine stability, all blends were found to have a stable engine operation. Between the oxyfuel types, EE10.65 (10.65 ethyl ethanoate, 89.35 % diesel) has slightly superior emissions characteristics at equal fuel mass flow rate. Both fuel additives are suitable for CI engine at low blending ratios. [ABSTRACT FROM AUTHOR]

In this paper, a rotary engine equipped with an n-butanol and hydrogen port-injection system was developed to investigate the combustion and emissions characteristics of a hydrogen-blended n-butanol rotary engine at part load and stoichiometric conditions. A self-developed hybrid electronic control unit was adopted to adjust the injection durations of n-butanol and hydrogen. The rotary engine was run under the conditions of 4000 rpm, a manifold absolute pressure of 35 kPa and a fixed spark timing of 45 °CA before the top dead center during the whole testing operation. The hydrogen volumetric fraction in the total intake was varied from 0% to 6.30%. The test results manifested that the brake thermal efficiency and chamber temperature were simultaneously increased with hydrogen addition. The hydrogen supplement obviously shortened flame development and propagation periods. Both chamber pressure integral heat release fraction versus crank angle were increased when the hydrogen fraction was enhanced. HC emissions were reduced by 54.5% when hydrogen volume fraction was raised from 0% to 6.30%, CO and CO 2 emissions were also reduced after increasing hydrogen blending fraction. NOx emissions were mildly elevated due to the improved chamber temperature. [ABSTRACT FROM AUTHOR]

A series of starting tests was conducted on a turbocharged diesel engine to investigate combustion instability for various coolant temperatures, ranging from 20 to 80°C, and fuel blends (neat diesel, blend of diesel with 30% biodiesel, and blend of diesel with 25% n-butanol). A statistical analysis was performed in order to quantify the effects of the coolant temperature and fuel properties on the extent of the instability phenomena. As expected, the engine thermal status was found to play an influencing role, with cold starting leading to combustion instability; a difference up to 38 bar between successive cycles was documented. The biodiesel blend exhibited higher instability and the n-butanol one showed higher absolute pressures but somewhat more stable operation. Both biofuel blends led to higher in-cylinder pressure irregularities compared to the neat diesel operation. For all examined blends, instability phenomena were still apparent even after several seconds from the engine start-up. [ABSTRACT FROM AUTHOR]