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In this paper, validated simulations using Ricardo WAVE have been performed to investigate the effect of the Miller cycle and low-carbon fuels on the performance (power, torque, BTE and BSFC) and emissions of a diesel engine. The results show that the increased Miller cycle effect (larger deviation of the advanced or retarded intake valve closing from the standard intake valve closing time) will decrease NOx, CO and HC emissions, and slightly improve brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) with slight loss in engine performance and increase in soot emissions. An engine running B0 (diesel with 0% Biodiesel in the blend) with a −18% Miller cycle effect has a reduction in NOx of 9% and CO of 4.3% with a decrease of 1.6% in power at the rated engine speed. Using low carbon fuels drastically reduces emissions with reduced BTE and increased BSFC. When used in conjunction, the Miller cycle and low-carbon fuels have an improved effect on both performance and emissions. The optimal results demonstrate that using B60 (60% Biodiesel in the blend) and a −8% Miller effect contributes to a 1.5% improvement in power, 1.2% in BTE, 13.3% in NOx, 38.5% in CO, 8.9% in HC, and 33.0% in soot at a cost of 6.0% increase in BSFC. The results show that it is an easy way to reduce NOx, CO, HC and soot emissions and increase the BTE of the engine by combining Miller cycle and low-carbon fuels. [ABSTRACT FROM AUTHOR]

Abstract: This study examined the performance and emission characteristics of a household size trigeneration based on a diesel engine generator fuelled with hydrogen comparing to that of single generation, cogeneration using ECLIPSE simulation software. In single generation simulation, the engine genset is used to produce electricity only and the heat from the engine is rejected to the atmosphere. In cogeneration and trigeneration, in addition to the electricity generated from the genset, the waste heat rejected from the hot exhaust gases and engine cooling system, is captured for domestic hot water supply using heat exchangers and hot water tank; and a part of the waste heat is used to drive absorption cooling in trigeneration. Comparisons have been made for the simulated results of these three modes of operation for hydrogen and diesel. The results prove that hydrogen is a potential energy vector in the future which is a key to meeting upcoming stringent greenhouse gases emissions. The study show that hydrogen has very good prospects to achieve a better or equal performance to conventional diesel fuel in terms of energetic performance, and a near zero carbon emission, depending on the life cycle analysis of the way the hydrogen is produced. The results also show enormous potential fuel savings and massive reductions in greenhouse gas emissions per unit of useful energy outputs with cogeneration and trigeneration compared with that of single generation. [Copyright &y& Elsevier]

Abstract: The performance and the efficiency of a trigeneration system fueling with pure diesel and with raw jatropha oil are investigated using the ECLIPSE software. The study is based on a diesel engine generating set. The genset is used for electrical power generation only, acting as a single generation. The trigeneration system consists of the genset, a waste heat recovery system and an absorption refrigerator. The genset is used to generate electricity; the waste heat system is used to collect the waste heat from the cooling system and the exhaust from the engine, to supply heating/hot water; and the absorption refrigerator is used to supply cooling/refrigeration, which is driven by the waste heat from the engine instead of electricity. A comparison of the thermal efficiencies and the CO2 emissions of trigeneration with single generation and cogeneration (combined heat and power — CHP) is carried out. The results from the study show that the thermal efficiency of trigeneration is higher than that of single generation; the CO2 emissions of trigeneration are lower than that of single generation. The results also show the performance differences between the trigeneration and single generation; and the differences between trigeneration and cogeneration. [Copyright &y& Elsevier]

Polyoxymethylene dimethyl ether (PODE) is a low-viscosity oxygenated fuel that can improve the volatility of blended fuels. In this work, the macroscopic and microscopic spray characteristics of diesel-PODE3-4 under different ambient temperatures and injection pressures (IP) are studied. The studied blends consisted of pure diesel (P0), two diesel blend fuels of 20% (P20) and 50% (P50) by volume fraction of PODE3-4. The Mie scattering and Schlieren imaging techniques are used in the experiment. The results show that with the increase in IP, the vapor phase penetration distance and the average cone angle of the three fuels increased, and the Sauter mean diameter (SMD) of the three fuels decreased. When the ambient temperature increased, the vapor phase projection area and the average vapor phase cone angle of P20 and P50 increased, and the SMD decreased, but the vapor phase projection area of pure diesel did not change significantly. The results indicate that the blended fuel with PODE3-4 has better spray characteristics than P0 at low temperature, and the SMD hierarchy between the three fuels is P0 > P20 > P50. Through the visualization experiment, it is helpful to further understand the evaporation characteristics of different fuel properties and develop appropriate alternative diesel fuel. [ABSTRACT FROM AUTHOR]

With the rise of the concept of carbon neutrality, carbon-free fuel ammonia has attracted widespread attention from internal combustion engine researchers. Ammonia/diesel dual fuel mode can effectively overcome the ignition difficulty of ammonia in the engine and is an effective measure to promote ammonia combustion. Based on a single-cylinder engine, diesel-ignited ammonia combustion experiments were conducted under conditions of 1200 rpm and 30 % load to systematically study the impact of ammonia energy ratio (AER), pilot injection ratio/timing on the combustion and emission characteristics of the ammonia/diesel dual fuel engine. This study finds that the pilot injection improves the upper limit of AER, reduces the cyclic coefficient of variation (COV). The rapid combustion fraction has been defined to understand the dual fuel combustion process. With the AER increases, the rapid combustion fraction of the single injection increases while the trends of the pilot injection strategy are the opposite. Both NOx emissions of the pilot injection strategies decrease while CO emissions increase. The reduction of NOx emissions may be caused by a decline in in-cylinder temperature. At a 35 % AER,Medium-low pilot injection ratios can increase the indicated mean effective pressure (IMEP), which is because as the pilot injection ratio exceeds 35 %, the growth rate in the effective expansion efficiency (EEE) is lower than that of heat transfer loss. When the pilot injection ratio is 35 %, the highest IMEP is achieved, CO and NOx emissions are cut down by 23 % and 20 %, respectively, compared to the single injection. [Display omitted] • Detailed investigation on ammonia/diesel dual fuel mode under low engine load. • Pilot injection strategy reduces the cyclic coefficient of variation. • The rapid combustion fraction has been defined to help understand the combustion process. • The highest IMEP is achieved while CO and NOx reduce by 23 % and 20 % with pilot injection. [ABSTRACT FROM AUTHOR]

Diesel/ammonia operation is one of the ways to efficiently utilize ammonia and reduce carbon emissions, however, the increase in fuel NO introduces serious emission problems. To explore the generation mechanisms of fuel NO and oxidant source NO, a multi-component diesel/ammonia chemical reaction mechanism was constructed in this study, and based on 3D CFD simulation and N-element tracking method, the combustion and different source NO emission characteristics of diesel/ammonia reactivity controlled compression ignition (RCCI) engine at low loads were investigated by pilot injection timing (SOI1) and pilot injection ratio (PIR). In addition, the effect of different first injection spray angle (SA1) and double injection spray angle (SA total) on the engine operation was investigated. The results showed that high PIR and delayed SOI1 enhanced the engine IMEP but led to high PRR max. At a PIR of 15 %, total NO emissions increased as SOI1 advanced, and the trend was reversed when the PIR was higher than 15 %. Fuel NO was produced earlier than the oxidant source N∗O. In terms of 1 spatial distribution, high concentrations of both NO and N∗O were distributed in and around the secondary diesel fuel ignition location, and fuel NO began to be reduced where the oxidant source N∗O was rapidly formed. The reduction mechanism of NO in the cylinder was a multi-path reduction mechanism incorporating Thermal DeNOx, NO Reburning, and inverse reaction pathways for NO formation from the oxidant source. Appropriate reduction of the SA total can significantly reduce the total NO emission while maintaining no significant reduction in IMEP. When SA total was 82°, the total NO emission was only 16.3 % of the original spray angle and PRR max was further reduced. After optimization, when a narrow SA total of 82°, SOI1 of −15° CA, and PIR of 35 % were used, the IMEP of the engine increased by 5.9 %, and the total NO emission was reduced by 86 %, while PRR max did not exceed the PRR upper limit. • High PIR and delayed SOI1 enhance the IMEP while lead to high PRR max. • 5.9 % increase in IMEP and 86 % reduction in NO emission for the optimized case. • Fuel NO was produced earlier than the oxidant source N∗O. • NO reduction mechanism includes Thermal DeNOx, NO Reburing, and reverse reaction of oxidant source NO formation. • The total NO emission is 16.3 % of the original injection angle when SA total is 82°. [ABSTRACT FROM AUTHOR]

• CeO 2 Nano powders and CNT as additives can reduce pollutant emissions. • CeO 2 in smaller size emits higher CO, NO x and PN but lower HC than the larger size. • CNT leads to lower gaseous emissions but higher PN emissions than CeO 2. • Comparative tests with and without additives were obtained at various engine conditions. This research reports the study of using Cerium oxide (CeO 2) nano additive with two different sizes (25 nm and 50 nm) blended with standard diesel fuel (DF-Ce25 and DF-Ce50) at various engine speed and load conditions. Moreover, carbon nanotube (CNT) is employed as a single additive (DF-CNT). Results indicate that the in-cylinder pressure of DF-CNT is slightly lower than that of DF under the most conditions due to more heat absorption during the evaporation process. In contrast, the in-cylinder pressure of DF-Ce25 and DF-Ce50 is higher than that of DF at relatively low speed due to the improved fuel spray and faster combustion. In terms of emissions, all fuels with nano-additives are overall lower than DF. DF-CNT can reduce CO, HC, NO x and PN by 20%, 22.6%, 21% and 5.5% respectively compared with DF, due to its improved spray and lower combustion temperature. Meanwhile, DF-Ce25 and DF-Ce50 produce the overall higher level of emissions of CO, NO x and HC than DF-CNT except for PN. A minimum engine (load-speed) limit and a maximum engine limit are found for CO emissions. Furthermore, DF-Ce25 emits higher NO x and lower HC than DF-Ce50, because CeO 2 of 25 nm has a higher reaction rate of CeO 2 due to its larger surface area and in return hinders the reaction of Ce 2 O 3. The difference of PN emissions between the two sizes of CeO 2 is the comprehensive result of the oxidization of particulate matters and the aggregation of unburnt fuel. [ABSTRACT FROM AUTHOR]