Search

Highlights: What are the main findings? ABE is an excellent alternative fuel for spark ignition engines ABE fuel enables spark ignition engines to have good power performance and emissions performances What is the implications of the main findings? Gasoline port injection plus ABE direct injection was adopted in this paper In total, an 80% ABE direct injection ratio can obtain excellent power performance at low and medium engine speeds and loads With the further increase in the engine speed and load, pure ABE is optimal to meet power demands A direct injection ratio between 60% and 80% ABE can keep gaseous and particle emissions at low levels ABE plus gasoline combined injection can improve the combustion performance and emission performances effectively ABE can be used as an alternative fuel for engines. This paper studies the combustion and emission performances of an SI engine with GPI plus ABEDI at different engine speeds and loads. The engine operating conditions included speeds of 1000–2600 rpm at the MAP = 50 kPa and loads of MAP = 30–70 kPa at a speed of 1800 rpm. The ABEDIr contained 0%, 20%, 40%, 60%, 80%, and 100%. At speeds = 1000–1800 or 2200–2600 rpm, the testing results showed the ABEDIr corresponding to the maximum IMEP at 80% or 100%. When the ABEDIr = 60%, HC and NOx emissions were the lowest at speeds of 1000–2600 rpm. Meanwhile, NPN and APN both decreased with the increasing of ABEDIr. As the MAP increased, CA0-90 decreased. At different loads, ABE-added fuels had lower HC and NOx emissions and higher IMEP values than pure gasoline. PN was lower than 4 × 104 n/cm3 when the ABEDIr was over 80%. Overall, 80% ABEDIr is a great choice for engine performance at the test range of loads and speeds, and pure ABE fuel is better if the power performance is the main requirement at high speeds and loads. [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]

N-butanol is a kind of biomass alcohol which can be produced by fermentation, and it is also a clean alternative fuel. The combustion and emissions characteristics of n-butanol/gasoline SI engine under different combined injection modes with the introduction of EGR was studied. N-butanol inlet injection plus gasoline in-cylinder direct injection is called N-GXDI; Gasoline inlet injection plus n-butanol in-cylinder direct injection is called G-NXDI. Through the analysis of combustion and emission performance under different EGR rates, injection modes and direct injection ratios (DIr), it is found that with the increase of DIr, cylinder temperature, pressure, and IMEP increase first and then decrease. Under the DIr = 50%, the combustion is more complete when the EGR rate is 5%. Under the same DIr, with the increase of EGR rate, CO emission decreased first and then increased, NOx emission opposite, THC emission increased. Under the same EGR rate, the total particle number of the two modes decreases first and then increases with the increase of DIr. The G-NXDI mode has advantages in combustion and primary emissions, while the N-GXDI mode has advantages in particulate emissions, suitable injection mode combined with EGR can greatly improve combustion and emission performance. • Gasoline/n-butanol combined injection mode is adopted. • Introduce different EGR rates to improve emission characteristics. • The optimal injection mode and injection ratio are explored. • Suitable combined injection modes combined with EGR can synergistically optimize combustion and emissions. [ABSTRACT FROM AUTHOR]

ABE can be used as an alternative fuel for engines. This paper studies the combustion and emission performances of an SI engine with GPI plus ABEDI at different engine speeds and loads. The engine operating conditions included speeds of 1000–2600 rpm at the MAP = 50 kPa and loads of MAP = 30–70 kPa at a speed of 1800 rpm. The ABEDIr contained 0%, 20%, 40%, 60%, 80%, and 100%. At speeds = 1000–1800 or 2200–2600 rpm, the testing results showed the ABEDIr corresponding to the maximum IMEP at 80% or 100%. When the ABEDIr = 60%, HC and NOx emissions were the lowest at speeds of 1000–2600 rpm. Meanwhile, NPN and APN both decreased with the increasing of ABEDIr. As the MAP increased, CA0-90 decreased. At different loads, ABE-added fuels had lower HC and NOx emissions and higher IMEP values than pure gasoline. PN was lower than 4 × 104 n/cm3 when the ABEDIr was over 80%. Overall, 80% ABEDIr is a great choice for engine performance at the test range of loads and speeds, and pure ABE fuel is better if the power performance is the main requirement at high speeds and loads.

Hydrous ethanol is a green fuel with great potential to deal with crises in the environment and energy. The study on the ethanol life cycle showed hydrous ethanol with 10%–20% water content had the best benefit, but the water content >10% would deteriorate engine power and emission performance. In this paper, the effects of the 30 vol% laboratory-grade H 2 O 2 on the combustion performance and emission characteristics were explored in an ethanol/gasoline combined injection engine. At the engine operating condition of engine speed/manifold air pressure = 1500 rpm/49.5 kPa, the H 2 O 2 -ethanol blend direct injection (DI) and gasoline port injection were conducted. Results showed that H 2 O 2 greatly improved the operating performance of the hydrous ethanol/gasoline engine. As the 30 vol%-H 2 O 2 ratio in the H 2 O 2 -ethanol blend (H 2 O 2 r) increased, the P max and the T max first increased and then decreased. Both CA0-10 and CA10-90 were slightly extended. For the DI ratio = 10%–40%, the optimal IMEP was obtained at H 2 O 2 r = 15%, which was 0.09 bar–0.11 bar higher than H 2 O 2 r = 0%. The optimal BTE was 0.86%, 0.75%, 0.71% and 0.75% higher than H 2 O 2 r = 0%, respectively. As the H 2 O 2 r and DI ratio increased, HC and NO x emissions descended, and CO emissions decreased first and then ascended slightly with the critical H 2 O 2 r = 10%–15%. Optimal CO, HC and NO x emissions were 21.76%, 58.83% and 42.02% lower than gasoline, respectively. H 2 O 2 could reduce particulate emissions, while the H 2 O 2 r < 15% at the DI ratio = 30%–40% should be adopted. • Effects of various H 2 O 2 -ethanol blend ratios were studied in a SI engine. • H 2 O 2 can decrease the CA10-90 of a hydrous ethanol/gasoline engine. • H 2 O 2 can propel the power and economic performance of the hydrous ethanol/gasoline engine. • H 2 O 2 can simultaneously reduce gaseous emissions and particulate matter. • H 2 O 2 is a promising additive to enhance the engine operating performance. [ABSTRACT FROM AUTHOR]

• Coordinated effects of CNG injection strategy and ignition timing were studied. • CNG/gasoline combustion yielded shorter CA0-10 and less CoV IMEP , but longer CA10-90. • Both nucleation and accumulation mode particles were inhibited by dual fuel combustion. • The slow LFS of CNG can be compensated by mid CNG injection strategy. • The engine BMEP was recovered using optimal injection strategy and ignition timing. CNG was a low-carbon alternative fuel for engines, which also had the advantages of higher engine knock resistance and better fuel/air mixing. The CNG injection and ignition timing was of significant importance for the performance of Dual Fuel Spark Ignition (DFSI) engines. In this paper, the coordinated effects of CNG injection strategy and ignition timing on the combustion and emission characteristics of CNG/gasoline DFSI engines were investigated. The results showed that the CNG/gasoline engine can achieve a comparable level of BMEP to that of a pure gasoline engine by using the CNGDI plus GPI injection approach with an optimal combination of injection and igniting timing. The cyclic variations of CNG/gasoline engines were increased with the advancing of ignition timing, and these variations can be ceased by using proper CNG injection strategies (early or mild). The gaseous emissions (HC, CO, and NOx) of CNG/gasoline engines were equivalent to those of pure gasoline engines; but the PN emissions were lower than that of gasoline engines. The particle size distribution of CNG/gasoline DFSI engines followed a single peak nucleation pattern and most of the particles were in nucleation mode (d ≤ 50 nm) peaking at around 15 nm. This study would be beneficial for the application of CNG in gasoline engines, which was promising to alleviate the strong dependence of engines on petroleum energy and to reduce their greenhouse gas emission. [ABSTRACT FROM AUTHOR]

• 30 vol% laboratory-grade H 2 O 2 was used in an ethanol/gasoline engine. • Effects of H 2 O 2 on the ethanol/gasoline engine at different λ values were studied. • H 2 O 2 can improve the power performance and fuel economy. • H 2 O 2 can reduce BSHC, BSCO and BSNO x of the hydrous ethanol/gasoline engine. Hydrogen peroxide (H 2 O 2) can prompt hydroxyl radicals and chain reactions in the combustion process. Compared with the research on compression ignition engines, the effects of H 2 O 2 were less studied in spark ignition (SI) engines. In this paper, 30 % laboratory-grade H 2 O 2 (H 2 O 2 -30 %) was utilized to obtain the H 2 O 2 -ethanol blend, which was applied to a direct injection system in a combined injection SI engine. Gasoline was used for the port injection system. The effects of H 2 O 2 -30 % ratio (H 2 O 2 r) = 0 %, 5 %, 10 %, 15 % and 20 % on combustion and emission performance of an ethanol/gasoline engine were explored at three excess air ratios (λ = 0.9, 1 and 1.2). Engine operating condition was set at engine speed = 1500 rpm and intake manifold pressure = 49.5 kPa. The results showed that H 2 O 2 -30 % could reduce the T max and P max , and extend CA0-10, CA50 and CA10-90. The inhibition effects of water on combustion performance can be alleviated due to the hyperactive H 2 O 2 at the H 2 O 2 r > 5 %. Optimal H 2 O 2 r increased engine IMEP by 0.14 bar, 0.11 bar and 0.05 bar, and reduced BSHC and BSCO by 30.5 %, 36.6 %, 31.6 % and 17.9 %, 32.1 % and 40.8 %, respectively. BSNO x were reduced by an average of 38.0 %, 28.8 % and 42.2 % at λ = 0.9, 1 and 1.2, respectively. [ABSTRACT FROM AUTHOR]

Hydrogen is considered to be a suitable supplementary fuel for Spark Ignition (SI) engines. The energy and exergy analysis of engines is important to provide theoretical fundaments for the improvement of energy and exergy efficiency. However, few studies on the energy and exergy balance of the engine working under Hydrogen Direct Injection (HDI) plus Gasoline Port Injection (GPI) mode under lean-burn conditions are reported. In this paper, the effects of two different modes on the energy and exergy balance of a SI engine working under lean-burn conditions are presented. Two different modes (GPI + GDI and GPI + HDI), five gasoline and hydrogen direct injection fractions (0, 5%, 10%, 15%, 20%), and five excess air ratios (1, 1.1, 1.2, 1.3, 1.4) are studied. The results show that the cooling water takes the 39.40% of the fuel energy on average under GPI + GDI mode under lean-burn conditions, and the value is 40.70% for GPI + HDI mode. The exergy destruction occupies the 56.12% of the fuel exergy on average under GPI + GDI mode under lean-burn conditions, and the value is 54.89% for GPI + HDI mode. The brake thermal efficiency and exergy efficiency of the engine can be improved by 0.29% and 0.31% at the excess air ratio of 1.1 under GPI + GDI mode on average, and the average values are 0.56% and 0.71% for GPI + HDI mode. • The brake thermal efficiency and exergy efficiency are highest at λ of 1.1. • The cooling water takes most of the heat but its exergy is the lowest. • With hydrogen addition, the exergy destruction decreases obviously. • HDI improves the brake thermal energy efficiency and exergy efficiency. • Hydrogen engines have potentials to be more efficient by exhaust energy recovery. [ABSTRACT FROM AUTHOR]

A numerical study on effects of hydrogen direct injection on hydrogen mixture distribution, combustion and emissions was presented for a gasoline/hydrogen SI engine. Under lean burn conditions, five different direct hydrogen injection timings were applied at low speeds and low loads on SI engines with direct hydrogen injection (HDI) and gasoline port injection. The results were showed as following: firstly, with the increase of hydrogen direct injection timing, the hydrogen concentration near the sparking plug first increases and then decreases, reaching the highest when hydrogen direct injection timing is 120°CA BTDC: Secondly, hydrogen can speed up the combustion rate. The main factor affecting the combustion rate and efficiency is the hydrogen concentration near the sparking plug: Thirdly, in comparing with gasoline, the NO X emissions with hydrogen addition increase by an average of 115%. For different hydrogen direct injection timings, the NO X emissions of 120°CA BTDC is the highest, which is 29.9% higher than the 75°CA BTDC. The hydrogen addition make the NO X emissions increase in two ways. On the one hand, the average temperature with hydrogen addition is higher. On the other hand, the temperature with hydrogen addition is not homogeneous, which makes the peak of temperature much higher. In a word, the main factor of NO X emissions is the size of high temperature zone in the cylinder: Finally, because the combustion is more complete, in comparing with gasoline, hydrogen addition can reduce the CO and HC emissions by 32.2% and 80.4% respectively. Since a more homogeneous hydrogen mixture distribution can influence a lager zone in the cylinder and reduce the wall quenching distance, these emissions decrease with the increase of hydrogen direct injection timing. The CO and HC emissions of 135°CA BTDC decrease by 41.5% and 71.4%, respectively, compared to 75°CA BTDC. • Hydrogen mixture distribution affects a lot on combustion and emissions. • Hydrogen direct injection timing can control the hydrogen mixture distribution. • There is a best hydrogen direct injection timing for a gasoline/hydrogen SI engine. • The hydrogen concentration near the sparking plug influences the combustion a lot. • It deeply analyzes that how hydrogen addition makes NO X emissions increase. [ABSTRACT FROM AUTHOR]

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions was presented for a gasoline/hydrogen SI engine. Three kinds of injection modes (gasoline, gasoline plus homogeneous hydrogen and gasoline plus stratified hydrogen) and five excess air ratios were applied at low speed and low load on a dual fuel SI engine with hydrogen direct injection (HDI) and gasoline port injection. The results showed that, with the increase of excess air ratio, the brake thermal efficiency increases firstly then decreases and reaches the highest when the excess air ratio is 1.1. In comparison with pure gasoline, hydrogen addition can make the ignition stable and speed up combustion rate to improve the brake thermal efficiency especially under lean burn condition. Furthermore, it can reduce the CO and HC emissions because of more complete combustion, but produce more NO X emissions due to the higher combustion temperature. Since, in the gasoline plus stratified hydrogen mode, the hydrogen concentration near the sparking plug is denser than that of homogeneous hydrogen, the ignition is more stable and faster, which further speed up the combustion rate and improve the brake thermal efficiency. In the gasoline plus stratified hydrogen mode, the brake thermal efficiency increases by 0.55%, the flame development duration decreases by 1.0°CA, rapid combustion duration decreases by 1.3°CA and the coefficient of variation (COV) decreases by 9.8% on average than that of homogeneous hydrogen. However, in the gasoline plus stratified hydrogen mode, due to the denser hydrogen concentration near the sparking plug and leaner hydrogen concentration near the wall, the combustion temperature and the wall quenching distance increase, which make the NO X and HC emissions increase by 14.3% and 12.8% on average than that of homogeneous hydrogen. • Stratified hydrogen can make the ignition more stable and faster. • Stratified hydrogen can further speed up the combustion rate of engine. • Stratified hydrogen can achieve higher brake thermal efficiency. • The advantages of stratified hydrogen are more obviously under lean burn condition. • Homogeneous hydrogen can reduce the HC and NO X emissions. [ABSTRACT FROM AUTHOR]

Hydrogen has shown potential for improving the combustion and emission characteristics of the spark ignition (SI) dual-fuel engine. To reduce the additional NO x emissions caused by hydrogen direct injection, in this research, the cooperative control of the addition of hydrogen with exhaust gas recirculation (EGR) in the hydrogen/gasoline combined injection engine was investigated. The results indicate that both the addition of hydrogen and the use of EGR can increase the brake mean effective pressure (BMEP). As the α H2 value increases from 0% to 25%, the maximum BMEP increases by 9%, 12.70%, 16.50%, 11.30%, and 8.20%, respectively, compared with the value without EGR at λ = 1.2. The CA0-10 tends to increase with increases in the EGR rate. However, the effect of EGR in increasing the CA0-10 can be offset by the addition of 15% hydrogen at λ = 1.2. Measurements of the coefficient of variation of the indicated mean effective pressure (COV IMEP) indicate that the addition of hydrogen can effectively extend the EGR limit. Regarding gaseous emissions, NO x emissions, after the introduction of EGR and the addition of hydrogen, are lower than those of pure gasoline without EGR. An 18% EGR rate yields a significant reduction in NO x , reaching maximum decreases of about 82.7%, 77.8%, and 60% compared to values without EGR at λ = 1.0, 1.2, and 1.4, respectively. As the EGR rate increases, the hydrocarbon (HC) emissions continuously increase, whereas a blend of 5% hydrogen can significantly reduce the HC emissions at high EGR rates at λ = 1.4. Finally, according to combustion and emissions, the coupling of a 25% addition of hydrogen with 30% EGR at λ = 1.2, and the coupling of a 20% addition of hydrogen with an 18% EGR rate at λ = 1.4 yield the best results. • The addition of H 2 and use of EGR can increase the brake mean effective pressure. • The effect of EGR on increasing CA0-10 can be offset by 15% addition of H 2 at λ = 1.2. • The addition of H 2 can effectively reduce the COV IMEP and extend the EGR limit. • The combination of EGR and H 2 addition generates lower NO x than those of gasoline. • The addition of 20% H 2 with 18% EGR rate provides the best condition at λ = 1.4. [ABSTRACT FROM AUTHOR]

In this paper, a new kind of injection mode, split hydrogen direct injection, was presented for a dual fuel SI engine. Six different first injection proportions (IP1) and five different second injection timings were applied at the condition of excess air ratio of 1, first injection timing of 300°CA BTDC, low speed, low load conditions and the Minimum spark advance for Best Torque (MBT) on a dual fuel SI engine with hydrogen direct injection (HDI) plus port fuel injection (PFI). The result showed that, split hydrogen direct injection can achieve a higher brake thermal efficiency and lower emissions compared with single HDI. In comparison with single HDI, the split hydrogen direct injection can form a controlled stratified condition of hydrogen which could make the combustion more complete and faster. By adding an early spray to form a more homogeneous mixture, the split hydrogen direct injection not only can help to form a flame kernel to make the combustion stable, but also can speed up the combustion rate through the whole combustion process, which can improve the brake thermal efficiency. By split hydrogen direct injection, the torque reaches the highest when the first injection proportion is 33%, which improves by 1.13% on average than that of single HDI. With the delay of second injection timing, the torque increases first and then decreases. With the increase of first injection proportion, the best second injection timing is advanced. Furthermore, by forming a more homogeneous mixture, the split hydrogen direct injection can reduce the quenching distance to reduce the HC emission and reduce the maximum temperature to reduce the NO X. The split hydrogen direct injection can reduce the HC emission by 35.8%, the NO X emissions by 7.3% than that of single HDI. • Split hydrogen direct injection achieves various stratified conditions of hydrogen. • Split hydrogen direct injection can make the combustion more complete and faster. • Split hydrogen direct injection can improve the brake thermal efficiency. • There is an optimal second injection timing for every first injection proportion. • Split hydrogen direct injection can reduce HC emission and NO X emissions obviously. [ABSTRACT FROM AUTHOR]

This study contributes to synthetic improvement and evaluation of energy efficiency and cleaner production by using combined injection in a gasoline-hydrogen blended engine bench. According to the previous published literature, few researches deal with combined injection technology, especial hydrogen combined injection. The equivalence ratio was kept at 0.77 and the energy input into the engine was constant. Some main conclusions were got that as for the PFI + GDI mode and the GDI mode, higher injection pressure could lead to longer spray penetration distance and better atomization, but excessive direct injection pressure may cause spray wall impingement and deteriorate the engine emissions performance. As for the PFI + HDI mode (90% gasoline and 10% hydrogen, energy ratio), a small amount hydrogen could improve the engine torque effectively and rise 5.34% than the PFI mode in average value and further reduce CO by 13.98%, HC emissions by 30.03%, but increase NOx emissions by 179.31% than the PFI mode. After hydrogen addition, increase of the direct injection pressure could suppress the forming of the accumulation mode particles. In the range of accumulation mode, the particle number (PN) concentration of the PFI + HDI mode reduced 26.1% than the PFI mode, reduced 35.66% than the PFI + GDI mode and reduced 12.28% than the GDI mode. Meanwhile, a comprehensive evaluation of different injection modes were obtained. [ABSTRACT FROM AUTHOR]

This study contributes to a method based on an aqueous solution of ammonia direct injection for NOx emissions control from internal combustion engines. Many previously published studies about deNOx technology are based on selective catalytic reduction (SCR), but only few deal with inner selective non-catalytic reduction (inner SNCR) technology, which is an intensive improvement of selective non-catalytic reduction (SNCR) applied in the in-cylinder purification procedure. Before numerical calculations were carried out, the computational fluid dynamic (CFD) simulation model was validated with steady-state experimental results. The main results revealed that with the increasing concentration of aqueous solution of ammonia, nitrogen oxides gradually decrease, and the largest decline of NOx is 65.1% with little loss of cylinder peak pressure. Unburned hydrocarbon (UHC) and carbon monoxide (CO) may increase using inner SNCR, and soot emissions show a decreased tendency. However, there is little change when ammonia content varies. Ulteriorly, refining the direct injection phase is of great help to inner SNCR technology to enhance the reduction of NOx and reduce NH3 oxidation and NH3 slipping.

Ethanol has significant potential for the reduction of fuel consumption and the emissions of engines. In this paper, a dual-fuel combined engine test rig with ethanol injected in the intake port and gasoline injected directly into the cylinder are developed and the effects of ethanol/gasoline ratio (Re) on the combustion and emission of particle numbers are investigated experimentally. The results indicate that the peak in-cylinder temperature (Tmax) decreases continuously with the increase of the ethanol/gasoline ratio (Re). For particle emissions, ethanol can significantly reduce the accumulation mode particle number (APN) at low engine speed; and the lowest number of particulates are at G25 (the gasoline ratio is 25% of the fuel) at low load. And at high engine load, the total particle number (TPN) is insensitive to speed with large ethanol fraction and TPN is relatively small. With the decrease of Re (Re < 50%), TPN rises sharply. When the direct injection timing advances, TPN reduces continuously and the effects caused by speed can be neglected. On the contrary, the speed has significant effects on particle emissions at various ignition times. At low speed, increasing ignition advance can cause the increase of the TPN; which is contrary to the effects of particle emissions at medium engine speed. And the effect of ignition timing at high speed on particle number is not obvious. The ignition timing for which the lowest TPN is reached will increase with the direct injection timing advances.

• An injection mode of isopropanol direct injection plus gasoline port injection is proposed. • Isopropanol can optimize combustion in the cylinder. • Isopropanol can improve power performance and operation stability. • Isopropanol can decrease unburned HC emissions, CO emissions and NO x emissions. • Isopropanol hoists the ability of the engine operating under lean-burn conditions. Energy crises and environmental issues require the development of green fuels for engines. Isopropanol is an excellent performance renewable alternative fuel for SI engines. It can be prepared by IBE fermentation. However, there have been few studies on the use of isopropanol/gasoline dual fuel in SI engines, especially based on the combined injection technology. For dual-fuel engines, the combined injection technology can further achieve clean combustion by flexibly controlling the fuel composition in the cylinder. Therefore, it is significant to combine the isopropanol/gasoline dual-fuel with the combined injection technology. The effects of the isopropanol ratio at different λ values on combustion and emissions characteristics of an isopropanol/gasoline dual-fuel combined injection SI engine were studied in this paper. The injection mode is isopropanol direct injection plus gasoline port injection. Six isopropanol ratios (0 %, 20 %, 40 %, 60 %, 80 %, 100 %) and five λ values (0.9, 1, 1.1, 1.2, 1.3) are set. The engine was tested at 1500 rpm with an intake pressure of 50 kPa. It is shown that isopropanol addition improves combustion, increases Pmax and maximum heat release rate, and shortens ignition delay period, rapid combustion period, and combustion duration. As the isopropanol ratio increases, the IMEP increases and the COV IMEP decreases. The improvements in combustion, IMEP and COV IMEP brought by the addition of isopropanol were more obvious under lean-burn conditions. Isopropanol addition effectively reduces unburned HC emissions, CO emissions, and NO x emissions. A higher isopropanol ratio in the mixture leads to better power and emissions performance. Isopropanol is a promising alternative fuel for engines, but its corrosive properties can damage the rubber parts of engines. [ABSTRACT FROM AUTHOR]

• Different injection strategies of methanol/gasoline dual fuel engine were evaluated. • Particle size distribution patterns changed for different fuel injection strategies. • The upper limit methanol ratio was 60% for engine performance improvement. • Methanol direct injection and gasoline port injection (MDI + GPI) was preferred. Methanol was a promising alternative fuel for spark ignition engines due to its liquid nature, large octane number and high oxygen content. The combined injection technology had the advantages of greater control flexibility, less engine knock tendency, and less engine-out emissions. However, the preferable injection mode of methanol/gasoline dual fuel engine was rarely reported. In this study, the combustion and emission characteristics of methanol/gasoline dual fuel engine with different injection modes, methanol direct injection plus gasoline port injection (MDI + GPI) or gasoline direct injection plus methanol port injection (GDI + MPI), were studied experimentally. The results showed that MDI + GPI mode was preferred for methanol/gasoline dual fuel engines, as this mode yielded higher engine brake effective mean pressure, larger heat release rate, lower cyclic variation, and less particle number emissions. An unimodal nucleation pattern particle size distribution can be observed for the MDI + GPI mode, which was beneficial for the after-treatment of particles in gasoline particle filter. [ABSTRACT FROM AUTHOR]

• Gasoline port injection plus ABE, IBE or butanol direct injection has been compared. • Gasoline/IBE mode owns higher IMEP and BTE than the other two modes. • Three dual-fuel modes have no significant difference in gaseous emissions. • Gasoline/ABE mode owns lower particle emissions than the other two modes. • ABE and IBE is better than butanol as the direct injection fuel in dual-fuel engine. Vehicles powered by internal combustion engine are now facing stringent regulatory requirements, so it is urgent to improve engine thermal efficiency and reduce harmful emissions. Alcohols have attracted wide attention because of their renewability and cleaner emissions, and the bio-butanol is most similar to gasoline and has been widely investigated in spark ignition (SI) engine. However, the high energy consumption of separation and purification during fermentation process leads to the high price of bio-butanol. ABE and IBE are the intermediates for the preparation of butanol by different fermentation methods, and using ABE and IBE directly in SI engine will greatly reduce the cost. Combined injection is the most suitable injection approach for dual-fuel engine because the engine can flexibly control the dual-fuel injection ratio and parameters. Therefore, the combustion and emissions of gasoline/ABE, gasoline/IBE and gasoline/butanol were experimentally compared based on gasoline port injection plus alcohol direct injection mode. The results show that gasoline/IBE is better than gasoline/ABE and gasoline/butanol in power performance and brake thermal efficiency (BTE). And when the direct injection ratio (DIr) is low, the gaseous emissions of gasoline/ABE are superior, while emissions of gasoline/butanol are superior at high DIr. In addition, the particle number (PN) of gasoline/ABE is always the lowest among the three modes, and the particle basically show unimodal distribution. Overall, as direct injection fuel in dual-fuel combined injection engine, ABE and IBE have more advantages than butanol in terms of combustion and emissions performance as well as cost. [ABSTRACT FROM AUTHOR]

Comparison reveals defects in existing methods for the combined injection of oxygen and neutral gas in the converter bath. A new technology is proposed, in which oxygen and neutral-gas jets are introduced in the working space through a two-level upper lance, while neutral gas is introduced through bottom units. [ABSTRACT FROM AUTHOR]

• The number and distribution of particles of DME/gasoline engine are studied. • Adding DME can reduce the particle numbers of DME/gasoline engine. • The size of particles of DME/gasoline engine is unimodal distributed. • Most of particles from DME/gasoline engine are in the nucleation mode. • APN fraction changes with the variation of engine loads of DME/gasoline engine. The understanding of particulate matter emissions from Dimethyl ether (DME)/gasoline combined injection engine is crucial for the application of DME in engines. In this study, the particulate number (PN) and the size distribution of particles from a combined injection spark ignition DME/gasoline engine are studied experimentally. The results show that the addition of DME can effectively reduce both the accumulation and nucleation mode particle numbers for the DME/gasoline engines compared with pure gasoline engines. The distribution of the particle sizes follows a single peak distribution pattern, and the size of the most of particles from DME/gasoline engine are in the nucleation mode, peaking at around 17.8 nm for different ignition timing and DME ratios. Both the nucleation particle numbers (NPN) and accumulation particle numbers (APN) are dependent on the operating conditions investigated in this study and the affecting degree depends on the DME ratios. The accumulation particle numbers (APN) fractions are almost the same for pure gasoline, but the APN fraction increased with the increase of engine load after DME additions. [ABSTRACT FROM AUTHOR]

• The HEDI + GPI combined injection mode was proposed. • Larger ω prolonged CA 0-10 and CA 10-90, decreased Tmax and Pmax. • HEDI + GPI mode had better power performance than GPI and EDI + GPI mode. • ω of 5% is best for CO and NO x emissions, 10% is best for PN emissions. • Larger ω increased HC emissions and made the size of particles smaller. Hydrous ethanol has lower cost and energy consumption during the production process than anhydrous ethanol. Many researchers used hydrous ethanol instead of anhydrous ethanol to manufacture hydrous ethanol-gasoline. The water ratio in hydrous ethanol (ω) determines the energy consumption in the production process of ethanol. However, no one researched the effects of different ω on combustion and emissions of hydrous ethanol-gasoline. So, we prepared five kinds of ethanol with different ω (0, 5%, 10%, 15%, 20% vol.) to research the effects of ω on combustion and emissions. This study adopted combined injection with hydrous ethanol direct injection plus gasoline port injection (HEDI + GPI). The engine speed was 1500 rpm, and λ was 1, the intake manifold absolute pressure was 48 kPa, the direct injection ratio was 20%, five spark timings varied from 5 °CA BTDC to 25 °CA BTDC. The results showed hydrous ethanol prolonged flame development and propagation duration, decreased Tmax and Pmax, delayed APmax. Water increased COV imep , but using hydrous ethanol at the reasonable spark timing would not significantly affect the stability. Meanwhile, when the spark timing was MBT, compared with GE (gasoline/anhydrous ethanol dual fuel) fuel, as ω in GEW (gasoline/hydrous ethanol dual fuel) fuels increased, torque and brake thermal efficiency improved by 1.69%, 1.13%, −0.01%, −0.77%; HC increased by 2.13%, 9.02%, 23.89%, 37.15%; CO decreased by 41.95%, 28.56%, 5.59%, 2.46%; NO x decreased by 10.10%, −0.75%, −0.17%, 4.18%; total PN emissions decreased by 24.07%, 69.57%, 36.34%, 32.45%. Meanwhile, more water caused the size of particles to drop, made particles smaller. [ABSTRACT FROM AUTHOR]

Background and Objectives: Sentinel lymph node (SLN) mapping was considered for treating endometrial cancer (EC) which was apparent confined to the uterus. Nevertheless, intermediate-high-risk EC patients have super high risk to undergo isolated para-aortic lymph node metastases comparing with low-risk patients. Therefore, this investigation aimed to compare the efficacy of two SLN methods in detecting para-aortic lymph node metastases., Methods: According to SLN mapping injection methods, intermediate-high-risk EC patients who received both SLN mapping and systematic lymphadenectomy were divided into the combined group (fundal and cervical injections) and the cervical group (cervical injection only)., Results: The para-aortic SLN detection rate in the combined group (40.4%) was higher than that in the cervical group (4.4%) with p < 0.001. While the differences concerning the sensitivity, false-negative rate, and negative predictive value between the two groups were not significant. The survival outcomes of patients were comparable between the two groups., Conclusion: Our data showcased that the combined (fundal and cervical) injection had a higher detection rate of para-aortic SLNs than cervical injection only. The efficiency of SLN mapping and the survival outcomes were not significantly different between the two groups. Further investigations are warranted to assess the value of combined injection regarding SLN technique., (© 2021 Wiley Periodicals LLC.)

• High ratio and early direct injection timing (DIT) of ABE can obtain higher IMEP. • GPI + ABEDI can reduce CoV IMEP and CA0-90 especially at lean burn condition. • Late DIT can effectively reduce NO x while early DIT is beneficial for lower HC. • 40% or 60% of ABEDIr with early DIT can effectively reduce the particle number. • 80% of ABEDIr combined with DIT = 300° CA BTDC can be regarded as best condition. Using ABE instead of bio-butanol as an alternative fuel can reduce the costs of separating and purifying bio-butanol from ABE solution. This paper investigated the performance of an SI engine with gasoline port injection plus ABE direct injection (GPI + ABEDI) at different ABE direct injection ratio (ABEDIr), excess air ratio (λ) and DIT. Results show that, with increasing ABEDIr, IMEP basically increases continuously at λ = 0.9 while increases firstly and then decreases at λ = 1.0 to 1.3. The highest IMEP is 7.3%, 5.2%, 3%, 2.8% and 3.7% higher than that of gasoline at λ = 0.9 to 1.3. CA0-10, CA0-90 and CoV IMEP with ABE addition are lower than that of gasoline, and minimum CA0-90 value is 6.9%, 11.2% and 18% lower than that of gasoline at λ = 0.9, 1.0 and 1.3. HC emissions decrease initially and then increase as ABEDIr increases, and ABEDIr and DITs corresponding to lowest HC emissions are concentrated at 20%, 40%, 60% and 300-210° CA BTDC, respectively. NO x emissions of 75° CA BTDC are the lowest while pure ABE with early DIT owns lower CO. Nucleation mode, accumulation mode and total particle number (TPN) decrease initially and then increase as ABEDIr increases. 40% or 60% of ABEDIr with 300 and 255° CA BTDC of DIT are superior for lowest particle number (PN), and the lowest TPN is 99.9%, 99.9%, 99.6%, 96.6% and 90% lower than that of gasoline at λ = 0.9 to 1.3, respectively. In summary, GPI + ABEDI mode adopting 80% of ABEDIr combined with DIT = 300° CA BTDC can effectively improve combustion and emissions. [ABSTRACT FROM AUTHOR]

In this paper, on the basis of combined injection technique, three injection modes with five n-butanol/gasoline volume ratios (ν N) were put forward, aiming to compare and evaluate the relationship between the injection mode and the combustion and emission characteristics of an n-butanol/gasoline SI engine equipped with an extra hydrogen direct injection system. The results indicated that under low load condition, compared with NG P (n-butanol/gasoline port injection) mode, the NG PD (n-butanol/gasoline combined injection) mode and NG PH (n-butanol/gasoline with hydrogen combined injection) mode can both improve the combustion performance. The peak cylinder pressure of NG PD and NG PH mode was 5.58% and 11.63% higher than that of NG P mode on average, respectively. Furthermore, the combined injection modes concentrated the process of heat release, shortened the combustion duration, increased the power performance and improved the combustion stability at all ν N. As for emissions, the NG PD and NG PH combined modes significantly decreased the HC and CO emissions, but increased the NO X emissions. Among all the test conditions, the NG PH mode with 25% ν N obtained the best combustion quality. Additionally, the effect rules of ν N on combustion and emission characteristics under NG P mode were found to be consistent with those under NG PD and NG PH combined modes. • An n-butanol/gasoline SI engine with hydrogen direct injection is proposed. • The low load performance versus n-butanol ratio under 3 injection modes are compared. • The change of combustion parameters with n-butanol ratio is consistent under 3 modes. • Combined injection and hydrogen can make up for the innate issues of n-butanol. [ABSTRACT FROM AUTHOR]

• The brake thermal efficiency can be enhanced by ABE addition. • 50% of ABE injection ratio can be regarded as superior based on the gaseous emissions. • 75% ABE plus 25% gasoline injection can keep the particle number at a very low level. • Stratified mixture effectively enhances engine power performance at lean conditions. • Fuel with high ABE ratio (≥50%) can improve engine combustion and particle emission. Recently, more attention has been paid to the application of biobutanol in spark ignition (SI) engines due to its superior properties among the biofuels. However, the high energy consumption and low efficiency of recovering biobutanol from ABE solution during the fermentation process lead to the high price of biobutanol, which limits its popularization in vehicles. Using ABE directly can solve the problem of high price of bio-butanol. This research explored the performance of an SI engine with ABE port injection (ABEPI) plus gasoline direct injection (GDI) at different excess air ratio (λ = 0.9, 1.0, 1.1, 1.2) and ABE port injection ratio (ABEPIr = 0, 25%, 50%, 75%, 100%). The results show that CA10-90 declines with increasing ABEPIr. CA0-10 and CA0-90 decrease with ABEPIr increasing at λ = 0.9, and first descend and then rise at λ = 1.0, 1.1 and 1.2. The coefficient of variations of IMEP (CoV IMEP) reaches the minimum value at ABEPIr = 75%. As ABEPIr increases, the peak in-cylinder pressure (P max), indicated mean effective pressure (IMEP) and brake thermal efficiency (BTE) increase at λ = 0.9 while first increase and then decrease at λ = 1.0, 1.1 and 1.2, reaching the maximum values at ABEPIr = 75%. Hydrocarbon (HC) reaches the minimum value at ABEPIr = 50%. Particle number decreases dramatically as ABEPIr increases from 0% to 50% and remains at an extremely low level when ABEPIr is greater than 50%. In summary, ABE is suitable for SI engine as an alternative fuel and fuels with high ABE ratio (≥50%) can effectively improve the combustion and particle emissions by ABEPI + GDI combined injection. [ABSTRACT FROM AUTHOR]

In order to reach the goal of energy conservation and pollution emissions reduction, the combustion and emissions of a combined injection engine with ethanol port injection and gasoline direct injection under lean burn conditions are investigated in this paper. The experiments are carried out by using different direct injection timing (DIT), gasoline addition ratio (α gasoline) and excess air ratios (λ). The results indicate that T max declines after gasoline addition at λ = 1, 1.2, while increases after gasoline addition at λ = 1.4. The IMEP reaches the maximum value at DIT = 90 or 105 °CA BTDC and 0%, 10% and 30% gasoline addition bring the highest IMEP at λ = 1, 1.2 and 1.4, respectively. The COV IMEP decreases continuously with the increase of α gasoline and the EPI+GDI mode has great advantages in improving the combustion stability under λ = 1.4 condition. As for gaseous emissions, from λ = 1 to λ = 1.4, HC emissions change from increasing trend to the decreasing trend with the increase of α gasoline , while the NOx emissions show the opposite. As for particle number, at λ = 1 and 1.2, the total particle number (TPN) shows an upward trend with the increase of α gasoline. When λ = 1.4, TPN decreases with the increase of α gasoline. • The injection mode is ethanol port injection plus gasoline direct injection. • 10% and 30% gasoline addition bring the highest IMEP at λ = 1.2, 1.4, respectively. • 10% gasoline addition with injection timing of 105°CA BTDC can be regarded as best condition at λ = 1.2 • 20% gasoline addition has significant effect on reducing COV IMEP and HC at λ = 1.4 • EPI+GDI is superior at lean condition due to the stratified mixture when ignition. [ABSTRACT FROM AUTHOR]

This study contributes to a method based on an aqueous solution of ammonia direct injection for NOx emissions control from internal combustion engines. Many previously published studies about deNOx technology are based on selective catalytic reduction (SCR), but only few deal with inner selective non-catalytic reduction (inner SNCR) technology, which is an intensive improvement of selective non-catalytic reduction (SNCR) applied in the in-cylinder purification procedure. Before numerical calculations were carried out, the computational fluid dynamic (CFD) simulation model was validated with steady-state experimental results. The main results revealed that with the increasing concentration of aqueous solution of ammonia, nitrogen oxides gradually decrease, and the largest decline of NOx is 65.1% with little loss of cylinder peak pressure. Unburned hydrocarbon (UHC) and carbon monoxide (CO) may increase using inner SNCR, and soot emissions show a decreased tendency. However, there is little change when ammonia content varies. Ulteriorly, refining the direct injection phase is of great help to inner SNCR technology to enhance the reduction of NOx and reduce NH3 oxidation and NH3 slipping. [ABSTRACT FROM AUTHOR]

Ethanol has significant potential for the reduction of fuel consumption and the emissions of engines. In this paper, a dual-fuel combined engine test rig with ethanol injected in the intake port and gasoline injected directly into the cylinder are developed and the effects of ethanol/gasoline ratio (Re) on the combustion and emission of particle numbers are investigated experimentally. The results indicate that the peak in-cylinder temperature (Tmax) decreases continuously with the increase of the ethanol/gasoline ratio (Re). For particle emissions, ethanol can significantly reduce the accumulation mode particle number (APN) at low engine speed; and the lowest number of particulates are at G25 (the gasoline ratio is 25% of the fuel) at low load. And at high engine load, the total particle number (TPN) is insensitive to speed with large ethanol fraction and TPN is relatively small. With the decrease of Re (Re < 50%), TPN rises sharply. When the direct injection timing advances, TPN reduces continuously and the effects caused by speed can be neglected. On the contrary, the speed has significant effects on particle emissions at various ignition times. At low speed, increasing ignition advance can cause the increase of the TPN; which is contrary to the effects of particle emissions at medium engine speed. And the effect of ignition timing at high speed on particle number is not obvious. The ignition timing for which the lowest TPN is reached will increase with the direct injection timing advances. [ABSTRACT FROM AUTHOR]