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In large-bore two-stroke diesel/nature gas dual-fuel marine engines, a certain quantity of diesel is injected into the cylinder to satisfy the full-power output engine rated power of the gas mixture. However, the ignition and flame propagation process based on the injection strategy of diesel direct injection combined with diesel jet flame on the ignition and combustion of natural gas is unclear, which directly affects the power and the thermal efficiency of engine and emissions. Therefore, this work numerically investigates the flame propagation characteristic under the strategy of the main and pilot diesel modes. The influence of the injection timing and proportion of diesel on combustion and emission performance are further analyzed. The results show that the influence of the injection timing of main diesel (MDIT) on the combustion process and emission performance is more obvious than that of the injection timing of pilot diesel (PDIT). The results indicate that the MDIT increased from −2°CA to −8°CA, the power increased by 316 kW, and the thermal efficiency improved by 1.5%. However, the CO2 emissions increased by 10.5 g/kWh, and the NOx emissions increased by 0.7 g/kWh. Additionally, an early PDIT is not conducive to the rapid organization of combustion, resulting in decreased engine power and thermal efficiency. Furthermore, it was found that the power improved by 50 kW and the thermal efficiency improved by 0.6%, with a decrease in the main diesel ratio (MDR) from 100% to 90%. Meanwhile, the CO2 emissions decreased by 4 g/kWh, although there was no obvious change in NOx emissions with the advance of MDR. [ABSTRACT FROM AUTHOR]

Biodiesel serve as promising fuel and optimal alternative for mitigating the present issues of fuel scarcity and emission control in compression ignition engines. Several Researches have concluded that engine performance and it's emission characteristics heavily depends on parameters like fuel droplet spray formation, atomization, evaporation and combustion which in turn depend on thermophysical properties of biodiesel fuel. In this study, the thermophysical properties like normal boiling, critical properties, vapor pressure, latent heat of vaporization, liquid density, liquid viscosity, liquid thermal conductivity, gas diffusion coefficients of two biodiesel fuels sample: Madhuca Indica and Radish oil are determined using standard correlation. Accurate mathematical model for estimation of evaporation rate and combustion of single component biodiesel droplet is framed and validated with single droplet setup experiment result for Jatropa Methyl Ester (JME), Karanjan Methyl Ester (KME), Mahua Methyl Ester (MME), Neem Methyl Ester (NME), Palm Methyl Ester (PME) oil and this model is further extrapolated to predict the evaporation and combustion behaviour of two unexperimented oil, Madhuca and Radish. It is found that Madhuca oil has the higher evaporation constant value of 0.1466 mm²/s and thus lowest lifetime in among the biodiesel fuel studied. This value is attributed to lower molecular weight and higher molecular diffusivity. On the other hand reverse trend is observed in Radish with lower evaporation constant and higher lifetime. This study behaves as comprehensive methodology for estimating the behaviour of biodiesel based on their composition and chemical structure and also as firm framework for combustion modelling in enhancing engine performance. [ABSTRACT FROM AUTHOR]

Spurred by the world's attention to pollution emissions from commercial aeroengines, the International Civil Aviation Organization (ICAO) has made more stringent emission regulations for civil aircraft engines, especially the NOx emission. This paper develops a Five-Point lean direct injection (LDI) combustor with three swirler schemes to reduce the emissions of commercial aircraft engines. The flowfield of the combustor is studied numerically. Moreover, the combustion efficiency and gaseous emissions in different inlet conditions and fuel ratios of the main stage (α) are studied experimentally. The corresponding results reveal that, under a fuel-air ratio (FAR) between 0.0130 and 0.0283 and an a value between 30% and 60%, the combustion efficiency is 99.18%, 98.83%, and 99.03% when the pilot stage works alone, and 99.69%, 99.23%, and 99.75% when the pilot and main stage work simultaneously. Furthermore, the experimental results suggest that the NOx emission decreases as α increases, demonstrating that the convergent swirler has a tremendous advantage in reducing NOx emissions over Venturi. [ABSTRACT FROM AUTHOR]

The aviation industry is recovering from COVID-19 to regain rapid growth at an increasing rate of over 5 % annually. Aviation compression ignition (CI) engines attributed to their economic fuel consumption and adorable reliability, have been widely utilized in the general aviation (GA) industry. To fill in the knowledge gap of the compatibility of Fischer Tropsch (FT) blended with long-chain oxygenated fuel applied into the aviation engines, this research focuses on analyzing the combustion performance and particle matter (PM) emissions of an aviation CI engine by burning FT alternative fuel and its pentanol blends (FT80P20 - 80 % FT + 20 % pentanol), in comparison with baseline diesel/pentanol-diesel blends (D80P20 - 80 % diesel + 20 % pentanol). It was found that FT80P20 significantly increases the indicated thermal efficiency (ITE) by 6.5 %, and remarkably decreases the indicated specific fuel consumption (ISFC) by 12 % in contrast to neat diesel at high load (8.5 bar IMEP), which is due to better homogeneous charge that alternates heterogeneous combustion. Moreover, the PM size-resolved number distributions of emissions were characterized. It was observed that the integrated PM emissions from diesel were predominant (∼1.4 × 1014 #/kg∙fuel), while those from FT80P20 were significantly reduced by nearly 85 % (∼0.2 × 1014 #/kg∙fuel). Concurrently, the particulate geometric mean diameter (GMD) were decreased apparently from 80 nm to 35 nm correspondingly. The research findings reveal that "main diffusion combustion" was predominant as burning diesel, while "main premixed combustion" was prominent as using FT80P20, which has a promising impact on effective engine-work promotion with superior PM mitigation. • The combustion and PM characteristics of an aviation engine burning diesel, FT and their pentanol blends were analyzed. • FT-pentanol blends present higher indicated thermal efficiency than baseline diesel by 6.5%. • FT-pentanol blends suppress the number-based PM by nearly 85% comparing to diesel. • Significantly promotional of combustion and PM utilizing FT-pentanol blends is owing to the main premixed combustion mode. [ABSTRACT FROM AUTHOR]

Ship emissions are one of the main sources of air pollution in port cities. The prosperous maritime trade has brought great harm to the air quality of port cities while promoting the development of the world economy. During the berthing process, ship auxiliary machines emit a large amount of air pollutants, which have a great impact on air quality and public health. Alternative marine fuels are being studied and used frequently to reduce ship emissions. This research was carried out to investigate the gaseous and particles emission characteristics of a marine diesel engine during the application of experimental biodiesel fuels. To study the influence of mixed fuels on engine performance, measurements were made at different engine loads and speeds. Different diesel fuels were tested using various ratios between biodiesel and BD0 (ultra-low sulfur diesel) of 0%, 10%, 30%, 50%, 70%, 90%, and 100%. The results indicated the use of biodiesel has little influence on the combustion performance but has a certain impact on exhaust emissions. The octane number and laminar flame speed of biodiesel are higher than those of BD0, so the combustion time of the test diesel engine is shortened under the mixed mode of biodiesel. In addition, a high ratio of biodiesel leads to a decrease of the instantaneous peak heat release rate, causing the crank angle to advance. As the biodiesel blending ratio increased, most of the gaseous pollutants decreased, especially for CO, but it led to an increase of particle numbers. The particle size distribution exhibits a unimodal distribution under various conditions, with the peak value appearing at 30–75 nm. The use of biodiesel has no effect on this phenomenon. The peak positions strongly depend on fuel types and engine conditions. The particulate matter (PM) emitted from the test engine included large amounts of organic carbon (OC), which accounted for between 30% and 40% of PM. Whereas the elemental carbon (EC) accounted for between 10% and 20%, the water-soluble ions components accounted for 6–15%. Elemental components, which accounted for 3–8% of PM emissions, mainly consisted of Si, Fe, Sn, Ba, Al, Zn, V, and Ni. Generally, biodiesel could be a reliable alternative fuel to reduce ship auxiliary engine emissions at berth and improve port air quality. [ABSTRACT FROM AUTHOR]

Maritime shipping is a key component of the global economy, representing 80–90% of international trade. To deal with the energy crisis and marine environmental pollution, hydrogen-natural gas-diesel tri-fuel engines have become an attractive option for use in the maritime industry. In this study, numerical simulations and experimental tests were used to evaluate the effects of different hydrogen ratios on the combustion and emissions from these engines. The results show that, in terms of combustion performance, as the hydrogen proportion increases, the combustion ignition delay time in the cylinder decreases and the laminar flame speed increases. The pressure and temperature in the cylinder increase and the temperature field distribution expands more rapidly with a higher hydrogen ratio. This means that the tri-fuel engine (H2+CH4+Diesel) has a faster response and better power performance than the dual-fuel engine (CH4+Diesel). In terms of emission performance, as the hydrogen proportion increases, the NO emissions increase, and CO and CO2 emissions decrease. If factors such as methane escape into the atmosphere from the engine are considered, the contribution of marine tri-fuel engines to reducing ship exhaust emissions will be even more significant. Therefore, this study shows that marine hydrogen-natural gas-diesel tri-fuel engines have significant application and research prospects. [ABSTRACT FROM AUTHOR]

Fuel injection has a critical role in an internal combustion engine and a significant effect on the quality of the fuel spray. In turn, fuel spray directly affects an engine's combustion, efficiency, power and emissions. This study evaluated three different injector nozzles in a highspeed, non-road diesel engine. It was run on diesel fuel oil (DFO) and testing was conducted at three different engine loads (100%, 75% and 50%) and at two engine speeds (2,200 rpm and 1,500 rpm). The nozzles had 6, 8 and 10 holes and a relatively high mass flow rate (HF). The study investigated and compared injection and combustion characteristics, together with gaseous emissions. The combustion parameters seemed to be very similar with all studied injector nozzles. The emission measurements indicated general reductions in hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) at most load/speed points when using the 6- and 10-hole nozzles instead of the reference 8-hole nozzles. However, smoke number increased when the alternative nozzles were used. [ABSTRACT FROM AUTHOR]

In this study, the influences of injection timing and exhaust gas re-circulation on combustion and emissions characteristics of biodiesel/2-methylfuran blends are investigated on a modified water-cooled 4-cylinder four-stroke direct injection compression ignition engine. The experimental conditions are, respectively, to adjust injection timing and exhaust gas re-circulation ratio at 0.38 MPa break mean effective pressure with the engine speed at 1800 rpm constantly. With injection timing in advance, the peak cylinder pressure rose while maximum heat release rate first decreased and next slightly raised. Ignition delay and brake specific fuel consumption reduced first and then raised while combustion duration and break thermal efficiency had the opposite trend. The NOx emissions increased, and HC emissions first reduced significantly and then slightly increased, while 1,3-butadiene and acetaldehyde emissions presented a reduction tendency. As exhaust gas re-circulation ratio increased gradually, ignition delay as well as combustion duration was prolonged. brake specific fuel consumption increased and break thermal efficiency declined. HC, CO, 1,3-butadiene, and acetaldehyde emissions raised while NOx emissions reduced significantly. Biodiesel could behave well in a Diesel engine and thus a feasible alternative fuel for diesel. Moreover, methylfuran addition into biodiesel could raise break thermal efficiency and the break thermal efficiency of BM20 is higher than BM10. However, both BM10 and BM20 appeared a combustion deterioration when injection timing at 2.5 °CA before top head center. [ABSTRACT FROM AUTHOR]

Dimethyl ether (DME) and n-pentanol can be derived from non-food based biomass feedstock without unsettling food supplies and thus attract increasing attention as promising alternative fuels, yet some of their unique fuel properties different from diesel may significantly affect engine operation and thus limit their direct usage in diesel engines. In this study, the influence of n-pentanol, DME and diesel blends on the combustion performance and emission characteristics of a diesel engine under low-temperature combustion (LTC) mode was evaluated at various engine loads (0.2–0.8 MPa BMEP) and two Exhaust Gas Recirculation (EGR) levels (15% and 30%). Three test blends were prepared by adding different proportions of DME and n-pentanol in baseline diesel and termed as D85DM15, D65P35, and D60DM20P20 respectively. The results showed that particulate matter (PM) mass and size-resolved PM number concentration were lower for D85DM15 and D65P35 and the least for D60DM20P20 compared with neat diesel. D60DM20P20 turned out to generate the lowest NO x emissions among the test blends at high engine load, and it further reduced by approximately 56% and 32% at low and medium loads respectively. It was found that the combination of medium EGR (15%) level and D60DM20P20 blend could generate the lowest NO x and PM emissions among the tested oxygenated blends with a slight decrease in engine performance. THC and CO emissions were higher for oxygenated blends than baseline diesel and the addition of EGR further exacerbated these gaseous emissions. This study demonstrated a great potential of n-pentanol, DME and diesel (D60DM20P20) blend in compression ignition engines with optimum combustion and emission characteristics under low temperature combustion mode, yet long term durability and commercial viability have not been considered. • Suitability of n-pentanol/DME/diesel blends in a LTC diesel engine was examined. • LTC mode was enabled by utilizing moderate EGR level and alcohol/diesel blends. • Engine performance drops slightly by blending oxygenated fuels and EGR induction. • PM/NOx trade-off can be control with suitable oxygenated blends fuel in LTC mode. [ABSTRACT FROM AUTHOR]

• A new separated swirl combustion system (SSCS) is proposed in this study. • The SSCS with optimized chamber geometries significantly improves combustion performance and emissions. • A sensitivity analysis optimized chamber geometries and reduced calculation time. To improve air efficiency in the combustion chamber, a new separated swirl combustion system (SSCS) is proposed in this study. The combustion performance and emission characteristics were analyzed using three-dimensional simulation. A sensitivity analysis of indicated power and soot emission by chamber geometries was carried out. Based on the results of the sensitivity analysis, the chamber geometries were optimized. Then, the combustion and emission performance of the SSCS with optimized chamber geometries under different speeds was tested and compared with a double swirl combustion system (DSCS) in a single-cylinder diesel engine. The simulation results show that because the angle of the inner chamber affects the fuel distribution in the inner and outer chamber, it has the greatest influence on the SSCS combustion performance. The depth of the separated chamber is the second most important optimization parameter, followed by the diameter of the outer chamber, the separated chamber diameter, the angle of the outer chamber and finally the volume ratio of the inner and outer chamber. By comparing the combustion performance, fuel/air mixture, velocity distribution and soot emission in the cylinder of different SSCS chamber geometries, the optimized chamber geometries were determined. Then, the combustion and emission performance of the SSCS with optimized chamber geometries was compared with a DSCS combustion system. The results show that the brake-specific fuel consumption (BSFC) was lower and the indicated thermal efficiency was higher in the SSCS than in the DSCS at various engine speeds. The results of this study are of great significance for the optimization of chamber geometries as well as the improvement of fuel/air mixture and combustion performance. [ABSTRACT FROM AUTHOR]

In this study, experiments and numerical simulations were used to improve the fuel efficiency of compression ignition engine using a gasoline-diesel blended fuel and an optimization technology. The blended fuel is directly injected into the cylinder with various blending ratios. Combustion and emission characteristics were investigated to explore the effects of gasoline ratio on fuel blend. The present study showed that the advantages of gasoline-diesel blended fuel, high thermal efficiency and low emission, were maximized using the numerical optimization method. The ignition delay and maximum pressure rise rate increased with the proportion of gasoline. As the gasoline fraction increased, the combustion duration and the indicated mean effective pressure decreased. The homogeneity of the fuel-air mixture was improved due to longer ignition delay. Soot emission was significantly reduced up to 90% compared to that of conventional diesel. The nitrogen oxides emissions of the blended fuel increased slightly when the start of injection was retarded toward top dead center. For the numerical study, KIVA-CHEMKIN multi-dimensional CFD code was used to model the combustion and emission characteristics of gasoline-diesel blended fuel. The micro genetic algorithm coupled with the KIVA-CHEMKIN code were used to optimize the combustion chamber shape and operating conditions to improve the combustion performance of the blended fuel engine. The optimized chamber geometry enhanced the fuel efficiency, for a level of nitrogen oxides similar to that of conventional diesel over a variety of operation ranges. [ABSTRACT FROM AUTHOR]

Reactivity controlled compression ignition (RCCI) is demonstrated as a promising combustion strategy to achieve high efficiency and clean combustion. However, less effort has been devoted to examine the achievable RCCI operational range over a wide range of engine speed. In addition, previous studies have found that superior EGR rate and high diesel/gasoline fuel ratio are required to ease the extension of the low-load operating range of RCCI regime. Even then, relatively high CO and HC (unburned hydrocarbon) emissions and the accompanying fuel con-sum ption penalty still remain a problem to be resolved. Therefore, in this work the potential of diesel-fueled LTC to achieve simultaneously low NOx and soot emissions while maintaining high thermal efficiency at low load (IMEP ≈ 0.23–0.26 MPa) is investigated and compared with the gasoline/diesel RCCI strategy. The results show that the diesel LTC operation can yield slightly higher soot and NOx emissions (soot: 0.002 g/kW h, NOx: 0.446 g/kW h), but CO and HC emissions as well as the fuel consumption are much lower than the RCCI strategy, implying the diesel LTC regime may be more suitable for low-load operations. In addition, the RCCI operational range at speeds ranging from 900 to 2500 r/min is determined, the results show that the maximum achievable load (IMEP) increases with an increase in speed, and a maximum IMEP of 1.2 MPa can be achieved at an engine speed of 2300 r/min. Ultra-low NOx and soot emissions (soot < 0.003 g/kW h, NOx < 0.4 g/kW h) can be achieved under the maximum loading conditions at each speed investigated. However, high levels of CO and HC emissions still remain a big problem to be solved. The lowest fuel consumption (168.6 g/kW h) occurred at an engine speed of 1900 r/min with an EGR rate of 56%, and the corresponding indicated thermal efficiency is up to 50%. In addition, intake boosting can be very effective for expanding the RCCI operating range at low engine speed (900 r/min), but excessive pressure rise rates could become problematic with increased amount of fuel injection. [ABSTRACT FROM AUTHOR]

Previous research has demonstrated that the separated swirl combustion system (SSCS) based on double swirl and TCD combustion chamber improves direct-injection diesel engine combustion performance. A new multi-swirl combustion system based on lateral swirl and TCD combustion chamber (MSCS-LT) was proposed in this study. Experimental research was performed using single-cylinder diesel engine to study MSCS-LT and SSCS combustion performance and energy distribution characteristics. Simulation research was performed to reveal the influence mechanisms of the combustion chamber structure on in-cylinder fuel-air mixing quality and heated part surface temperatures. Experimental results show that MSCS-LT provides better combustion performance and lower energy losses under various working conditions than SSCS, especially at high loads and low excess air coefficients. Simulation results show that MSCS-LT enhances fuel diffusion in the axial and circumferential directions, producing better fuel-air mixing quality. Since most of the fuel is kept in the combustion chamber, direct contact between the high-temperature gases and heated parts is avoided. However, in SSCS, the interference of adjacent fuel sprays causes the accumulation of the rich fuel-air mixture, deteriorating the fuel-air mixing quality. Meanwhile, the excessive injection angle causes direct contact between the high-temperature gases and the cylinder head as well as the cylinder liner, resulting in higher surface temperatures. • A multi-swirl combustion system is designed to improve DI diesel engine performance. • MSCS-LT obtains higher thermal efficiency and less energy losses than SSCS. • MSCS-LT enhances fuel-air mixing while reducing surface temperature of heated parts. • To optimize MSCS, apply wall-flow guided effect and keep fuel in combustion chamber. [ABSTRACT FROM AUTHOR]

• DSCS with a combustion chamber diameter of 83 mm outperformed at various loads and excess air coefficients. • Reducing the combustion chamber diameter promoted the wall-flow guiding effects in the DSCS. • Enhanced air motion promoted the fuel–air mixing in the outer chamber and the clearance with diameter reduction. A double swirl combustion system (DSCS) in a diesel engine can make significant efficiency improvements and emission reductions. To explore the effects of combustion chamber diameter on the performance at various operations, DSCSs with a diameter of 83, 91, and 98 mm (DSCS83, DSCS91, and DSCS98) were designed and tested in a single-cylinder diesel engine at the maximum torque speed of 1800 rpm under various loads and various excess air coefficients (φ). The experimental results showed that DSCS83 outperformed the other DSCSs, with a 2.1–4.9% decrease in brake specific fuel consumption (BSFC), 12.4–23.1% reduction in soot, and a shortening of the combustion period by 1.6–3.6 °CA. To reveal the mechanism of fuel–air mixing in different DSCSs, simulation models were established with AVL-Fire. The simulation results indicated that the wall-flow-guiding effects and in-cylinder air motion including air entrainment and reversed squish improved as the combustion chamber diameter decreased, which contributed to fast fuel–air mixing in the outer chamber and the clearance, high indicated power and low soot generation. However, when combustion chamber further decreased from 83 to 76 mm, the unutilized air in the inner chamber and the clearance reduced the performance. An analysis of the uniformity index of the equivalence ratio in different parts of DSCS was performed to characterize the fuel–air mixing process. Results found that DSCS83 had a 1.2–4.8% improvements in the whole-chamber uniformity index at 60° CA ATDC at 32% load operating condition. These results could be an essential reference in the optimization and application of DSCSs in diesel engines. [ABSTRACT FROM AUTHOR]

• A sensitivity analysis of stepped-lip chamber geometry parameters was carried out. • The lip radius has the greatest influence on power due to fuel splitting at lip. • A methodology is established with MIGA for combustion chamber design at high load. • The optimized chamber shows a good performance on combustion and emission. An optimization of spray angle and combustion chamber geometry was conducted to improve the in-cylinder fuel/air mixing process and optimize the combustion process of a heavy-duty diesel engine at full load. The chamber is based on the stepped-lip piston bowl, and the lip radius, lip depth, bowl radius and bowl distance are optimized. A sensitivity analysis of fuel/air mixing and combustion process to stepped-lip chamber geometry parameters was carried out. The simulated results show that the lip radius affects the fuel splitting at the lip, and has the greatest influence on the stepped-lip combustion chamber. The bowl radius is the second most important optimization parameter, followed by the bowl distance and finally the lip depth. To obtain the optimal combination of the combustion chamber geometry in a wide searching space, a total of 100,000 different combustion chambers were solved with multi-island genetic algorithm. Compared to the baseline, the optimized chamber has higher enhanced air utilization, more homogeneous fuel/air mixture, rapider combustion process, higher indicted power delivery and lower emissions. The results of this study are important to guide the stepped-lip combustion chamber design of heavy-duty diesel engines for better fuel/air mixture and combustion performance. [ABSTRACT FROM AUTHOR]

Abstract: In engine combustion studies of bioethanol blended diesel fuels, biodiesel is a very important blending fuel for preventing phase separation between diesel and bioethanol. The purpose of this study is to investigate the impact of biodiesel in bioethanol blended diesel fuel on ignition delay, premixed combustion phasing, engine performance and exhaust emissions characteristics. In this work, the fuel properties of diesel–bioethanol blends were measured and engine tests were conducted using a single cylinder diesel engine. Based on the experimental results, we found that increasing the biodiesel blending ratio recovered the reduced fuel density and cetane number of bioethanol blended diesel fuel, while the kinematic viscosity and surface tension both increased. In addition, the lower heating value (LHV) slightly decreased when biodiesel fuel was added. By increasing the blending ratio of biodiesel fuel, the ignition delay and the premixed combustion phasing advanced, and the IMEP decreased. However, the premixed combustion duration in all tested blended fuels showed almost similar values, regardless of the biodiesel contents. Biodiesel blending decreased the EI-HC emission in wide engine operating regions. In addition, for the premixed combustion phasing and ignition delay, the increase of biodiesel fuel influenced the decrease of EI-HC emission. In the case of EI-CO and EI-soot emissions at advanced injection timings (around 30° BTDC), when the combustion occurred in the squish area of the combustion chamber, the biodiesel blending impact was clear. The increase of biodiesel fuel reduced EI-CO and EI-soot emissions. In addition, the increase of biodiesel fuel slightly reduced the EI-NO x emission. [Copyright &y& Elsevier]

Abstract: This study applies the L9 orthogonal array of the Taguchi method to find out the best hydrogen injection timing, hydrogen-energy-share ratio, and the percentage of exhaust gas circulation (EGR) in a single DI diesel engine. The injection timing is controlled by an electronic control unit (ECU) and the quantity of hydrogen is controlled by hydrogen flow controller. For various engine loads, the authors determine the optimal operating factors for low BSFC (brake specific fuel consumption), NO X , and smoke. Moreover, net heat-release rate involving variable specific heat ratio is computed from the experimental in-cylinder pressure. In-cylinder pressure, net heat-release rate, A/F ratios, COV (coefficient of variations) of IMEP (indicated mean effective pressure), NO X , and smoke using the optimum condition factors are compared with those by original baseline diesel engine. The predictions made using Taguchi''s parameter design technique agreed with the confirmation results on 95% confidence interval. At 45% and 60% loads the optimum factor combination compared with the original baseline diesel engine reduces 14.52% for BSFC, 60.5% for NO X and for 42.28% smoke and improves combustion performance such as peak in-cylinder pressure and net heat-release rate. Adding hydrogen and EGR would not generate unstable combustion due to lower COV of IMEP. [Copyright &y& Elsevier]

• The LSCS significantly reduces fuel consumption and soot emissions. • The LSCS exerts better injection timing adaptability. • The relevant influence mechanisms of injection timing for the LSCS were revealed. To further study the combustion performance and injection timing sensitivity, the lateral swirl combustion system (LSCS) performance was compared against a widely-used TCD combustion system (TCDCS) experimentally in a single-cylinder diesel engine. The experimental results show the LSCS exhibited better combustion performance and lower emissions compared to the TCDCS: the fuel consumption and soot emissions were decreased by 2.5–4.2 g/kW∙h and 0.27–0.73 FSN at different speeds. Further, when the injection timing was retarded from −15 to −8°CA ATDC, the fuel consumption and soot emissions for the LSCS increased by 1.4% and 2%; while for the TCDCS these increases were 2.8% and 17%, respectively. Clearly, the fuel consumption and soot emissions for the LSCS increase relatively slowly. Then, simulation was created to reveal the wall-flow-guided mechanism. For the LSCS, the wall-flow-guided geometry is a vertical convex edge, which is different from a traditional circular ridge: the spay jet almost invariably collides on the convex edge to form the wall-flow-guided and interferential interactions, promoting fuel-air mixing and exerting excellent injection timing adaptability. Therefore, the LSCS exhibits better combustion performance, and appropriately delaying the injection timing can simultaneously obtain relatively better the fuel consumption and soot and NO x emissions. [ABSTRACT FROM AUTHOR]

To study how intake swirl affects the combustion performance of the lateral swirl combustion system (LSCS), experiments under different swirl ratios were carried out in a single-cylinder diesel engine to optimize the circumferential injection angle (CIA) and test the eventual combustion performance. Then, simulation under different swirl ratios was conducted to reveal the influence mechanisms of intake swirl on the fuel/air mixing characteristics of the LSCS. Experimental results show that, as the swirl ratio (SR) was increased from 0 to 1.0, the optimal CIA increased 2.5° in the opposite direction to that of the intake swirl. Besides, the LSCS obtained better combustion performance with SR = 0 than with SR = 1.0, especially at high loads and low excess air coefficients. Simulation results indicate that, generating intake swirl weakens the wall-flow-guided and interferential interactions of the LSCS, thereby deteriorating the in-cylinder air utilization and fuel/air mixing uniformity, especially at high loads and low excess air coefficients, in which the interactions between the LSCS chamber and spray jets is strong due to the enhanced spray penetration ability. Therefore, the LSCS without intake swirl obtains the optimal fuel/air mixing and combustion performance in DI diesel engines. [ABSTRACT FROM AUTHOR]

• The PM emissions were studied under the condition of EGR, load and blend fuels. • The influence of the additive n -pentanol in biodiesel/diesel blends was analyzed. • The combination of n -pentanol and EGR reduced TPMC-NO X emissions simultaneously. • Soot and TPNC emissions were decreased by n -pentanol addition. • The addition of n -pentanol could reduce the particle geometric mean diameter. Biodiesel has a high viscosity, which limits its application to engines. However, n -pentanol has low viscosity and high volatility, which is considered a promising additive. This study examined the influence of n -pentanol/biodiesel/diesel blends on the performance and particulate emissions of a diesel engine at different loads, under the condition of coupling exhaust gas recirculation (EGR) (0–30%). The three test fuels included pure diesel (D100); 80% diesel and 20% biodiesel blended fuel (BD20); 64% diesel, 16% biodiesel, and 20% n -pentanol blended fuel (BDP20). The results indicated that the influence of EGR on the NOx emissions between fuels was greater than that of the physicochemical properties of the fuels. For the same EGR rate, the heat release rate (HRR), peak in-cylinder pressure (IP), and brake thermal efficiency (BTE) increased with the engine load increased. After adding n -pentanol to BD20, the HRR increased. The peak IP and BTE values of BDP20 were similar to those of D100 and BD20. With the addition of n -pentanol, the total particulate number concentration (TPNC), soot, and total particulate mass concentration (TPMC) emissions decreased. Furthermore, the trade-off relationship between TPMC and NOx was improved, and the geometric mean diameter (GMD) of the particles decreased. [ABSTRACT FROM AUTHOR]

A lateral swirl combustion system (LSCS) was designed to promote the spatial spray distribution through the spray wall impingement, and previous studies have established its combustion performance improvement in direct injection (DI) diesel engines. To verify that the improvement in combustion performance is due to the optimal wall-flow-guidance under the assumptive spray impingement position, numerical and experimental tests were conducted under different circumferential injection angles (CIA). The fuel/air mixing and combustion characteristics were computed and analyzed. The endoscopic visualization technique was applied to a single-cylinder diesel engine to record the spray and combustion processes. Based on the two-color method, flame temperature distribution, soot concentration distribution and the corresponding combustion performance were analyzed. Then the variation tendency of combustion performance was further validated under different engine speeds. The numerical and simulation results consistently show that the LSCS chamber and spray jet achieve an optimal match when the spray impingement position is precisely on the convex edge (CIA = 0°). At this position, the LSCS exerts the lowest fuel consumption and soot emission under various engine speeds, because significant lateral swirls form and evenly distribute fuel across all split arcs, promoting the in-cylinder fuel/air mixing and combustion. Therefore, the wall-flow-guided assumption of the LSCS in DI diesel engines is successfully verified in this study. [ABSTRACT FROM AUTHOR]

• Stratified combustion process under assisted ignition strategy was analyzed. • Effect of key assisted ignition factor on combustion characteristics was explored. • 35°CA BTDC ignition timing and (0, −88.5, ±15 mm) ignition position were optimal. • Case5 and Case7 were the preferred application assisted ignition strategy scheme. • The combustion performance of optimized spark schemes was effectively improved. This work aimed to further improve the combustion performance in a diesel Wankel engine by optimizing the assisted ignition strategy. Based on the established and verified dynamic simulation model, the effects of some key assisted ignition parameters, such as the number of assisted spark plug, assisted ignition position (AIP) and assisted ignition timing (AIT) on combustion performance were analyzed systematically. Simulation results indicated that the reaction process occurred in the mid-anterior region of the rotary chamber due to the stratified-charge mixture and forward-propagate flame. The combustion performance of the double assisted spark plug schemes was better than that of the single assisted spark plug scheme. The double assisted spark plugs symmetrically distributed relative to the major axis (X-axis) of the rotary chamber, the combustion process was more reasonable. When changing AIP, peak combustion pressure (P max) and combustion zone varied greatly, while they changed little when advancing AIT. For the optimized assisted ignition strategies, the optimal AIP scheme was Case5 (0, −88.5, ±15 mm) and the optimum AIT scheme was Case7 (35°CA BTDC). Comparing with the original scheme (Case1), their P max increased by 16.68% and 17.83%, respectively. Meanwhile, the CA50 and CA10-90 were shortened obviously. [ABSTRACT FROM AUTHOR]