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The object of this paper is to reduce soot emissions under typical 5s transient conditions of constant speed and increasing torque. And effects of fuel injection timing on combustion and emissions parameters were experimentally and numerically studied in a regulated two-stage turbocharged diesel engine with a turbine bypass valve (TBV). The test results indicated that: the smaller TBV opening could improve deterioration of smoke emissions and BSFC at medium and heavy loads. Afterward, the full-stage injection timing (FSIT) strategies (delaying injection timing during the entire transient process) could reduce soot and NOX emissions simultaneously. However, when TBV opening became larger, smoke emissions and BSFC were deteriorated gradually. Moreover, the sectional-stage injection timing (SSIT) strategies (advancing injection timing from 10 % load to a preset load and delaying injection timing from the preset load to 100 % load) could markedly reduce soot emissions by 75.8 % with TBV opening 20 %; the degradation of fuel consumption could be effectively suppressed. Finally, coupling the SSIT strategies with the TBV control strategies could significantly improve the transient performance.

By using two types of different fuels and changing the ratios of these fuels, Reactivity Controlled Compression Ignition Engine (RCCI) is able to provide a more effective control over combustion phase at different loads and speeds. In a typical RCCI engine which could be considered as a type of homogeneous charge compression ignition (HCCI) engine, a low reactive fuel is injected into the intake port and a high reactive fuel is directly injected into the combustion chamber. In this study, a multi-dimensional model coupled with chemical mechanism is developed to simulate an RCCI engine operation fueled with iso-octane as the low reactive fuel and n-heptane as the high reactive one. Initially, the engine map was derived using different quantities of total above-mentioned fuels at different ratios and then engine inappropriate operating points were detected and improved by changing intake air pressure and injection timing strategies. The improved criteria to extend engine map are ringing intensity limit, NOx formation standard and gross indicated efficiency. It was concluded that high ringing intensity and NOx formation can be reduced by increasing intake air pressure; also badfire and misfire points can get improved by retarding the injection timing.

Addressing the problem of limited methane (CH4) recovery degree under different production conditions in a target low-permeability carbonate gas reservoir, this study intends to further investigate the effect of carbon dioxide (CO2) injection on enhanced gas recovery (EGR). A group of long-core physical simulation experiments of CO2 injection for EGR was adopted. Field injection–production parameters were converted to laboratory conditions through similarity criteria to simulate the actual production process of gas wells. Systematic experiments on CH4 depletion and CO2 displacement were carried out under different irreducible water saturation, gas injection timing pressure and injection rates. The influence laws of each key parameter on the CO2 breakthrough time and CH4 recovery degree were analyzed emphatically, and the optimal injection–production scheme was obtained. For the target low-permeability carbonate gas reservoir (permeability < 1 mD), the optimal CO2 injection scheme is as follows: for layers with medium to high irreducible water saturation (≥40%), CO2 injection at a rate of 36,000 m3/d per well after the end of stable production (formation pressure > 7.38 MPa) can increase the CH4 recovery degree by 3–5%. This study provides experimental support for the optimization of CO2 injection schemes for enhanced recovery in gas reservoirs and the adjustment of gas reservoir development strategies under different irreducible water saturation conditions.

Regardless of the increasingly intensive application of vehicles with electric drives, internal combustion engines are still dominant as power units of mobile systems in various sectors of the economy. In order to reduce the emission of exhaust gases and satisfy legal regulations, as a temporary solution, hybrid drives with optimized internal combustion engines and their associated systems are increasingly being used. Application of the variable compression ratio and diesel fuel injection timing, as well as the tribological optimization of parts, contribute to the reduction in fuel consumption, partly due to the reduction in mechanical losses, which, according to test results, also results in the reduction in emissions. This manuscript presents the results of diesel engine testing on a test bench in laboratory conditions at different operating modes (compression ratio, fuel injection timing, engine speed, and load), which were processed using a zero-dimensional model of the combustion process. The test results should contribute to the optimization of the combustion process from the aspect of minimal particulate matter emission. As a special contribution, the results of tribological tests of materials for strengthening the sliding surface of the aluminum alloy piston and cylinder of the internal combustion engine and air compressors, which were obtained using a tribometer, are presented. In this way, tribological optimization should also contribute to the reduction in particulate matter emissions due to the reduction in fuel consumption, and thus emissions due to the reduction in friction, as well as the recorded reduction in the wear of materials that are in sliding contact. In this way, it contributes to the reduction in harmful gases in the air.

In order to study the problem that the pressure in the cylinder decreases significantly after diesel is mixed with isopentanol, which leads to the reduction of power performance, the software of AVL-FIRE is used for simulation, and the angle of start injection is adjusted to improve cylinder pressure. It turns out that in terms of combustion, The maximum burst pressure is reduced after mixing isoamyl alcohol. By increasing fuel injection timing, maximum burst pressure can rise to 87.8%-94.5% of the original engine respectively. The indicated power can be increased to 91.92%-95.62% of the original. In terms of emissions, after mixing, with the increase of fuel injection timing, NO does not change significantly, Soot shows a downward trend.

A combination of enhanced oil recovery (EOR) methods, specifically polymer flooding and low salinity (LS) brine injection, has been shown to improve oil recovery beyond what is achievable with either method used alone. However, the optimal sequence and timing of these methods remain unclear, affecting their efficiency. This study investigates the impact of injection sequences and timing of LS brine and polymer to optimize oil recovery by understanding the underlying mechanisms. Six injection scenarios were tested: (1) injecting high salinity (HS) water followed by LS brine (tertiary injection), (2) injecting HS water to intermediate saturation followed by LS brine, (3) injecting LS brine directly (secondary injection), and in each case, (4) polymer injected simultaneously with LS brine, (5) polymer injected after the LS brine, or (6) polymer injected before the LS brine. The results showed a positive synergy between LS brine and polymer in both secondary and tertiary injections. This synergy is highly sensitive to injection timing, sequence, and rock/fluid properties. The combined effect of LS brine and polymer shifts the flow regime by altering the balance between capillary and viscous forces, maximizing oil recovery when both mechanisms are active. Conversely, the effectiveness declines when one mechanism dominates. Therefore, the timing and order of polymer and LS brine injection significantly influence displacement efficiency and oil recovery, with different injection sequences producing varying outcomes, even with the same EOR techniques.

In order to effectively reduce greenhouse gas emissions and decrease reliance on conventional fossil fuels, ammonia has emerged as a leading zero-carbon alternative fuel for marine engines. Utilizing test data from a marine dual-fuel engine with a high compression ratio of 36.9, we simulated the combustion process of a large-bore, high pressure direct injection two-stroke marine dual fuel engine. This study investigates the effects of the ammonia-energy ratio (AER) and ammonia injection timing (AIT) on combustion and emission characteristics. The results indicate that ammonia can be combusted stably at a compression ratio of 36.9. The AER increases, the in-cylinder pressure shows a trend of “rising first and then decreasing”. Additionally, the heat release rate curve broadens, afterburning intensifies, and the duration of combustion is extended. Consequently, the indicated thermal efficiency (ITE) decreases from 54.84 to 42.2%, while carbon dioxide (CO 2 ) emissions are reduced from 472.5 g/(kW·h) to 52.5 g/(kW·h), representing a reduction of 88.9%. AER63% represents the optimal operating condition for the engine, allowing it to achieve high power density without surpassing the maximum explosive pressure (Pmax). Additionally, the nitrogen oxides (NO x ) emissions comply with Tier III emission limits. The advancement of AIT resulted in heat release advancement, increased isovolumicity, higher in-cylinder pressures, and advancement of CA10, CA50 and CA90, but prolonged combustion duration CA10-90. The advancement of AIT resulted in higher Pmax, ITE and the indicated mean effective pressure (IMEP). During the change of AIT from 4 °CA before top dead center (BTDC) to 4 °CA after top dead center (ATDC), ITE increased from 39.7 to 56.3%, a rise of 16.6%. Additionally, the IMEP increased from 1.89 MPa to 2.09 MPa. For every 1 °CA advance in AIT, Pmax increased by 0.72 MPa. The change in AIT had no effect on CO 2 emissions. However, when AIT was delayed, the reduction in NO x was more significant than the reduction in nitrous oxide (N 2 O). Specifically, NO x was reduced by 0.15 g/(kW·h), while the equivalent CO 2 emissions from N 2 O decreased by 1.31 g/(kW·h) for every 1°CA of AIT delay.

This study presents a comprehensive analysis of the performance, emissions and combustion characteristics of diesel and simarouba methyl ester (SME B20) fuels at various injection timings and load conditions. The investigation covers key parameters such as brake thermal efficiency (BTE), brake specific fuel consumption (BSFC) and emissions of carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx) and smoke opacity. Experiments were conducted using different Start of Main Injection (SoMI) and Start of Pilot Injection (SoPI) timings, specifically 18 deg, 20 deg, 30 deg and 35d eg before top dead center (BTDC), across brake power levels ranging from 0 to 5.2 kW. Results indicate that SME B20 consistently exhibits lower emissions and improved performance characteristics compared to diesel, largely due to its higher oxygen content, which promotes better performance. In terms of performance, diesel demonstrates higher BTE, especially at lower injection timings, while SME B20 performs efficiently at higher loads. CO, HC and smoke opacity emission levels were significantly reduced in SME B20 blends, particularly at optimized injection timings. NOx emissions, although higher at increased loads for both fuels, were consistently lower for SME B20 compared to diesel, especially at the SoMI 20 deg BTDC.

In diesel-ignited natural gas marine dual-fuel engines, the pilot diesel injection timing (PDIT) determines the premixing time and ignition moment of the combustible mixture in the cylinder. The PDIT plays a crucial role in the subsequent development of natural gas flame combustion. In this paper, four PDITs (− 8 °CA, − 6 °CA, − 4 °CA, and − 2 °CA) were studied. The results show that the advancement of PDIT increased the engine's power, thermal efficiency, and natural gas flame spread velocity, and increased NO emissions and CH 4 emissions of the marine engine. The PDIT affected the ignition delay period and the rapid combustion period to a greater extent than the slow combustion period and the post combustion period. With each 2 °CA advancement of PDIT, the engine's power increased by 69.87 kW, thermal efficiency increased by 0.42%, radial flame spread velocity increased by 2 m/s, axial flame spread velocity increased by 1.7 m/s, NO emissions increased by 6.1%, and CH 4 emissions increased by 3.75%.

In diesel engine, fuel injection timing is a major parameter that affects combustion, performance and emission characteristics. Variation in injection timing has a strong effect on BTE, BSFC, BSEC, smoke and NOx emissions because of the change in maximum pressure and temperature in engine cylinder. In this experimental investigation, the optimum performance DEE-diesel blend ratio DE15D (15% DEE and 85% diesel by volume) was tested for variable injection timings to evaluate its effect and determine the optimum fuel injection timing, as the addition of DEE to diesel fuel causes retardation in dynamic injection timing. The engine tests were carried out at 10%, 25%, 50%, 75% and 100% of full load with 3º and 6º advancement, base and 3º and 7º retarded injection timings. The test results show that BSFC and BSEC provide the best result for the base injection timing at full load condition. The 6º advancement in injection timing at full load condition reduced smoke by 12.5% and HC by 15.38%. The retarded injection timing by 7º at full load showed improvement in BTE by 7.96% and in NOx by 3.66%.