Diesel Combustion Research Articles

Characteristics, sources and health risk assessment of trace metals and polycyclic aromatic hydrocarbons in PM2.5 from Hefei, China.

Trace metals (TRs) and polycyclic aromatic hydrocarbons (PAHs) are major toxic components of fine particulate matter (PM2.5) and related to various health adverse outcomes. The study aims to get a better understanding of the contents, sources and risks of PM2.5-bounded TRs and PAHs in Hefei, China, during the period of 2019-2021. We collected 504 samples and measured twelve TRs and sixteen priority PAHs by inductively coupled plasma mass spectrometry and high-performance liquid chromatography. The annual mass concentrations of PM2.5 was fluctuated in the year of 2019-2021 at 50.95, 47.48 and 59.38μg/m3, with seasonal variations in rank order of winter > spring > autumn > summer. The median concentrations of PM2.5-bounded ƩTRs and ƩPAHs were also fluctuated, 132.85, 80.93 and 120.27ng/m3 for ƩTRs, 2.57, 5.85 and 2.97ng/m3 for ƩPAHs, in the year of 2019, 2020 and 2021, respectively. Seasonal variations of ƩTRs and ƩPAHs show the highest concentration in winter. Positive matrix factorization was used for identified pollution emission sources, and TRs mainly originated from coal combustion, traffic emission and fugitive dust, while PAHs stemmed from biomass, diesel, gasoline and coal combustion. Health risk assessment indicated that adults were more vulnerable than children, the carcinogenic risk assessment of As and Cr manifested a certain degree of cancer risk (1.0 × 10-6 < CR < 1.0 × 10-4) in adults group, and health risks of TRs were higher than PAHs in Hefei. These findings suggest that PM2.5-bounded TRs and PAHs should be considered when making emission control strategies for air pollution, and winter, combustion sources and adults should achieve more policy attention to decrease exposure risks in Hefei.

An innovative method of ammonia use in a light-duty automotive diesel engine to enhance diesel combustion, performance, and emissions

This study investigated the novel method of ammonia use in a light-duty automotive diesel engine. An emulsification technique and ammonia solution are combined and adopted to prepare ammonia solution in diesel emulsion referred to as emulsified diesel-ammonia solution (EDAS) and tested under similar diesel combustion conditions. The ammonia solution concentration in EDAS was fixed as 10% by volume (EDAS10) with 2% v/v of surfactant to avoid excessive ammonia slip, corrosive effects, and oxides of nitrogen (NOx) formation. The aim of this study is to explore the effect of presence of hydrogen in EDAS10 on the diesel combustion process under high-pressure multiple injection strategies. Experiments were performed at low, medium, and high loads at the same combustion phasing (CA50) and total energy input as that of diesel to investigate the influence of EDAS10 on combustion, performance, and emissions. The start of injection of EDAS10 and exhaust gas recirculation rate was varied to attain the CA50. The combustion results showed that the EDAS10 blend had increased the heat release rate in the premixed combustion phase with shortened duration and decreased the heat release rate in the diffusion combustion phase compared to neat diesel operation. Double and triple injection of EDAS10 blend also increased the indicated and brake thermal efficiencies by about 4–7% than neat diesel operation. A decrease in 50–67% unburnt emissions, 8–13% decrease in smoke, and 7–19% increase in NO emissions, 2–10% increase in CO2emissions were observed with EDAS10 when compared to diesel operation.

Experimental Characterization of Hydrocarbons and Nitrogen Oxides Production in a Heavy-Duty Diesel–Natural Gas Reactivity-Controlled Compression Ignition Engine

Reactivity-Controlled Compression Ignition (RCCI) combustion is considered one of the most promising Low-Temperature Combustion (LTC) concepts aimed at reducing greenhouse gases for the transportation and power generation sectors. Due to the spontaneous combustion of a lean, nearly homogeneous mixture of air and low-reactivity fuel (LRF), ignited through the direct injection of a small quantity of high-reactivity fuel (HRF), RCCI (dual-fuel) shows higher efficiency and lower pollutants compared to conventional diesel combustion (CDC) if run at very advanced injection timing. Even though a HRF is used, the use of advanced injection timing leads to high ignition delays, compared to CDC, and generates high cycle-to-cycle variability, limited operating range, and high pressure rise rates at high loads. This work presents an experimental analysis performed on a heavy-duty single-cylinder compression ignited engine in dual-fuel diesel–natural gas mode. The objective of the present work is to investigate and highlight the correlations between combustion behavior and pollutant emissions, especially unburned hydrocarbons (HC) and oxides of nitrogen (NOx). Based on the analysis of crank-resolved pollutants measurements performed through fast FID and fast NOx systems under different engine operating conditions, two correlations were found demonstrating a good accordance between pollutant production and combustion behavior: Net Cyclic Hydrocarbon emission—cyclic IMEP variations (R2 = 0.86), and Cyclic NOx—maximum value of the Rate of Heat Released (R2 = 0.82).

Determination of combustion and emission characteristics of liquid Fischer-Tropsch diesel fuel synthesized from coal in a diesel engine

Fischer–Tropsch (FT) synthesis is a production method that processes a liquid diesel fuel from heavy carbon-containing organic compounds such as coal and biomass. FT synthesis is an essential process in demonstrating the usability of coal-to-liquid fuel in internal combustion engines. This study investigates the effects of using FT diesel fuel synthesized from coal on the combustion characteristics of a single-cylinder common-rail direct-injection diesel engine. The engine tests were conducted at 50% of the wide-open throttle position and fixed engine control parameters (cycle duration, fuel amount, start of injection timing, etc.). As a result of the study, it was observed that the combustion with the use of FT diesel fuel started (almost 1.5 °CA) and completed earlier according to the petroleum-based diesel (D100). The cyclic variations were more stable with FT diesel fuel. With the use of FT diesel fuel, the indicated mean effective pressure was 3% lower, peak cylinder gas pressure was slightly lower, and the combustion noise was 2–3 dB quieter compared to D100. The heat release was higher during the premixed combustion phase at the cycle durations of 67 ms and 55 ms, while it occurred very small at the cycle duration of 86 ms. Significant reductions in CO2 and NOx emissions, which are complete oxidation products, were obtained with FT diesel fuel compared to D100. The fuel properties, combustion characteristics and emission results showed that no further measures should be taken to use FT diesel in compression ignition engines. FT diesel fuel can be safely used as an alternative fuel.

A review on natural background concentration of beryllium prevalent in ambient air and different environmental matrices

Abstract Beryllium, the 44th most abundant element in the Earth’s crust, is found ubiquitously in environmental matrices, including air, soil, and water, as well as in a variety of food items such as grains, fruits, and vegetables. The typical concentration of Be in air is reported to be ~0.05 ng/m3, whereas in soil, its concentration varies from ~2 to 5 ppm. The prevalence of Be in soil leads to its presence in water as well as in plants, and various human activities such as burning of coal, petrol, diesel, mining, and other industrial activities may further increase the concentration of beryllium in environment and associated matrices. It needs to be mentioned that the typical concentration of Be in food items is of the order of few ppb, whereas in drinking water, the typical values are reported to be &lt;1 ppb or so. Based on the literature survey including some of the most recent studies, the present paper provides summary on concentration of Be in air, soil, and other relevant matrices as concise and consolidated reports on beryllium are scarce. In addition, related information like Be in drinking water along with available guidelines is also provided. Information on the prevalence of other isotopes of beryllium, i.e., 7Be4 and 10Be4, which are radioactive and are produced by cosmic rays in atmosphere, is also included in the present paper.

Occurrence, distribution and risk assessment of polycyclic aromatic hydrocarbons in soils around main water source areas of Beijing, China.

Polycyclic aromatic hydrocarbons (PAHs) in urban environments have been globally concerned due to their significant health impacts on residents. However, little is known about potential risks of PAHs from centralized water source areas. In the present study, 326 soils samples from the main water source areas of Beijing were collected and the occurrence, source appointment, and risks of PAHs were systematically investigated based on the monitoring results from high-performance liquid chromatography (HPLC). The total PAHs (∑16 PAHs) concentrations ranged from 5.70 to 1512ng/g with median value of 44.2ng/g, in which 4-ring and 5-ring groups were the major components. PAHs concentrations in the cultivated land were significantly higher than other areas, which could reflect significant impact of soil organic matter and total nitrogen contents on the spatial variations of PAHs. Further source identifications through positive matrix factorization model (PMF) revealed that biomass (22.5%), coal (21.4%), gasoline (17.6%) and diesel (16.4%) combustion were dominant sources of soil PAHs in the study area. Moreover, the risk assessment indicated that total ecological and health risk of PAHs were negligible, but individual PAH, including pyrene and benzo(b)fluoranthene, should be concerned due to their potential risks in several monitored stations located in the secondary protection area of four reservoirs. Our study provided new insights into environmental risks of soils in main water source areas from PAHs and could be helpful for organic micropollutant controlling and drinking water safety in rapidly urbanizing cities.

Using radius of influence and adaptive collision mesh to capture droplet collision of a diesel engine

The collision of fuel droplets is a vital part of diesel engines. In this work, a three-dimensional (3D) model of diesel combustion in the cylinder of a diesel engine was constructed, and the radius of influence (ROI) and adaptive collision mesh (ACM) models were used to simulate the collision behavior of the droplets. For comparison, analysis was also conducted for when the droplet collision model was not used. The impacts of the ROI and ACM models were analyzed based on the engine operating conditions, and the relevant parameters of the ROI and ACM models were modified. It was found that if the ROI model was used with different influence radius, the average Sauter mean diameter (SMD) of the diesel droplets was affected. The ROI model had a larger impact on the computational fluid dynamics calculation time than the ACM model and a smaller impact on the engine power and pollutant emissions. A large number of parcels could be used to simulate diesel spray to reduce the dependence on grids. For simulations with more parcels, the efficiency of the ACM model was much higher than that of the ROI model.

Differences in compositions and effects of VOCs from vehicle emission detected using various methods

Vehicle exhaust and oil fuel evaporation emit volatile organic compounds (VOCs). The differences in VOC compositions and their effects determined using different methods have not been addressed sufficiently. In this study, VOC samples are obtained from single gasoline and diesel vehicle exhausts using a portable emission measurement system, from a tunnel in Yichang City, and from gasoline and diesel evaporation at gas stations. A total of 107 VOCs are analysed. The calculated VOC source profiles (based on VOC source profiles of single-vehicle type and vehicle fleet composition in the tunnel) and the tested source profiles (from a tunnel test) are compared. The results show that gasoline burning can reduce alkenes from a mass fraction of 53.1% (for evaporation) to 3.6% (for burning), as well as increase the mass fraction of alkenes from 1.3% (for diesel evaporation) to 34.0% (for diesel burning). The calculated VOC source profiles differed from the tested VOC source profiles, with a coefficient of divergence of 0.6. Ethane, ethylene, n-undecane, and n-dodecane are used to distinguish VOCs in gasoline and diesel exhausts. Cis-2-butene, 2-methylpentane, m/p-xylene, o-xylene, and n-decane can be used to separate gasoline from diesel. The xylene/ethylbenzene ratios accurately reveal the photochemical age. Gasoline burning increases health risks associated with VOCs compared with gasoline evaporation. Furthermore, it modifies the main contributor to ozone formation potential. This study is expected to facilitate refined VOC source apportionment and studies pertaining to speciated emission inventories.

Historical trends of traditional, emerging, and halogenated polycyclic aromatic hydrocarbons recorded in core sediments from the coastal areas of the Yellow and Bohai seas

Historical trends of polycyclic aromatic hydrocarbons (PAHs) contamination were reconstructed from eleven sediment cores located in intertidal zones of the Yellow and Bohai seas for a period encompassing the last 80 years. The analysis encompassed 15 traditional PAHs (t-PAHs), 9 emerging PAHs (e-PAHs), and 30 halogenated PAHs (Hl-PAHs), including 10 chlorinated PAHs (Cl-PAHs) and 20 brominated PAHs (Br-PAHs). Concentrations of target PAHs were highest in industrial and municipal areas situated along the coast of the Bohai Sea, including Huludao, Yingkou, Tianjin, and Dandong, constituting a substantial mass inventory. All target PAHs showed increasing trends since the 1950s, reflecting the development history of South Korea and China. High molecular weight PAHs accumulated in sampling sites more than low molecular weight PAHs. A positive matrix factorization model showed that the PAH sources were coal and gasoline combustion (35%), diesel combustion (33%), and biomass combustion (32%). Over the last 80 years, the contribution of coal and gasoline combustion increased in all regions, while diesel combustion and biomass combustion varied across regions and over time. Toxicity equivalence values were highest for t-PAHs (>99% contribution), followed by Cl-PAHs, Br-PAHs, and e-PAHs. Concentrations of t-PAHs in Eastern Asia seas have increased since the 1900s, particularly in intertidal areas compared to subtidal areas. The intertidal zone removed 83% of the total flux of PAHs originating from land and thus appears to serve as a buffer zone against marine pollution. Overall, this study provides novel knowledge on the historical trends and sources of PAHs on a large scale, along with insights for future coastal management.

Gas and Propane Combustion from Stoves Emits Benzene and Increases Indoor Air Pollution.

Exposure pathways to the carcinogen benzene are well-established from tobacco smoke, oil and gas development, refining, gasoline pumping, and gasoline and diesel combustion. Combustion has also been linked to the formation of nitrogen dioxide, carbon monoxide, and formaldehyde indoors from gas stoves. To our knowledge, however, no research has quantified the formation of benzene indoors from gas combustion by stoves. Across 87 homes in California and Colorado, natural gas and propane combustion emitted detectable and repeatable levels of benzene that in some homes raised indoor benzene concentrations above well-established health benchmarks. Mean benzene emissions from gas and propane burners on high and ovens set to 350 °F ranged from 2.8 to 6.5 μg min-1, 10 to 25 times higher than emissions from electric coil and radiant alternatives; neither induction stoves nor the food being cooked emitted detectable benzene. Benzene produced by gas and propane stoves also migrated throughout homes, in some cases elevating bedroom benzene concentrations above chronic health benchmarks for hours after the stove was turned off. Combustion of gas and propane from stoves may be a substantial benzene exposure pathway and can reduce indoor air quality.

Subchronic exposure to 1,2-naphthoquinone induces adipose tissue inflammation and changes the energy homeostasis of mice, partially due to TNFR1 and TLR4

Air pollution affects energy homeostasis detrimentally. Yet, knowledge of how each isolated pollutant can impact energy metabolism remains incomplete. The present study was designed to investigate the distinct effects of 1,2-naphthoquinone (1,2-NQ) on energy metabolism since this pollutant increases at the same rate as diesel combustion. In particular, we aimed to determine in vivo effects of subchronic exposure to 1,2-NQ on metabolic and inflammatory parameters of wild-type mice (WT) and to explore the involvement of tumor necrosis factor receptor 1 (TNFR1) and toll-like receptor 4 (TLR4) in this process. Males WT, TNFR1KO, and TLR4KO mice at eight weeks of age received 1,2-NQ or vehicle via nebulization five days a week for 17 weeks. In WT mice, 1,2-NQ slightly decreased the body mass compared to vehicle-WT. This effect was likely due to a mild food intake reduction and increased energy expenditure (EE) observed after six weeks of exposure. After nine weeks of exposure, we observed higher fasting blood glucose and impaired glucose tolerance, whereas insulin sensitivity was slightly improved compared to vehicle-WT. After 17 weeks of 1,2-NQ exposure, WT mice displayed an increased percentage of M1 and a decreased (p = 0.057) percentage of M2 macrophages in adipose tissue. The deletion of TNFR1 and TLR4 abolished most of the metabolic impacts caused by 1,2-NQ exposure, except for the EE and insulin sensitivity, which remained high in these mice under 1,2-NQ exposure. Our study demonstrates for the first time that subchronic exposure to 1,2-NQ affects energy metabolism in vivo. Although 1,2-NQ increased EE and slightly reduced feeding and body mass, the WT mice displayed higher inflammation in adipose tissue and impaired fasting blood glucose and glucose tolerance. Thus, in vivo subchronic exposure to 1,2-NQ is harmful, and TNFR1 and TLR4 are partially involved in these outcomes.

Chemical speciation of organic compounds and elemental compositions of PM2.5 in Mexico City: Spatial-seasonal distribution, emission sources, and formation processes

The simultaneous study of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs, and metals in particles ≤2.5 μm (PM2.5) provided helpful information to identify pollutant emission sources in the Metropolitan Zone of Mexico Valley (MZMV). PM2.5 samples were obtained during three seasons of a year from five sampling sites simultaneously collected. The dominant sources of the species were the incomplete combustion of fossil fuel by vehicles, followed by the resuspension of geogenic material, evaporation from petrogenic sources, and emissions from the oil refining industry. The northeast (NE) of the MZMV, hosting the industrial area, exhibited the highest contribution of ΣPAHs<228 due to the high presence of diesel vehicles. The NE also showed the highest metal concentrations of geogenic origin due to its proximity to agricultural lands and the dominant wind direction from the north to the south, introducing pollutants into the Valley. Among the pollutants, 1-nitropyrene emitted from diesel combustion sources and 2-nitrofluoranthene formed in the atmosphere were found. Particles enriched with Mn + Fe + Co + Cu and Rb were emitted from agricultural lands and volcanic soil, respectively, and originated from local/peripherical soils, while particles enriched with Cr + Cs + Th were originated from geogenic sources further away from the MZMV. Cd + Pb and n-alkanes C16-C22 were emitted outside the Valley, while PAHs, nitro-PAHs, and heavier n-alkanes (C23-C33) were emitted inside the Valley. Decision-makers could use our results to develop control strategies for air pollutants from specific sources. Comparisons of hydrocarbon and metal concentrations in other cities were also made.

Experimental study on wall heat transfer from diesel spray flame in two-dimensional combustion chamber operated with rapid compression and expansion machine (RCEM)

Heat transfer phenomenon in internal combustion diesel engine is one of problems to be solved. This study was conducted to investigate the relationship between diesel spray impingement, combustion processes, and heat loss using a rapid compression and expansion machine (RCEM). Furthermore, spray combustion and heat transfer processes were investigated using multiple injection strategies with a 6-holes injector. The amounts of diesel fuel used in the pilot, pre-injection, and main injection sprays were 3.964, 0.747, and 11.205 mg, respectively. Variations in common rail pressure conditions (30, 120, and 180 MPa) were applied to properly investigate spray evaporation, air–fuel mixture formation, and heat transfer in the combustion chamber. In addition, a local wall heat flux sensor was installed in the cylinder (head and liner) and piston cavity (upper lip, lip, and bottom) to measure the heat flux distribution, and a diffused backlight illumination method was used to visualize the spray and flame behavior in the combustion chamber and 2D piston cavity. The results showed that the impingement flame surrounding the cylinder head contributed to the highest magnitude and longest duration of the heat flux on the cylinder side owing to the spray flame velocity, impingement, and residence time. Meanwhile, the highest different temperature at cavity bottom induced more heat flux on the cavity side than that on the squish side. In addition, the higher injection pressure increased the spray momentum and spray tip penetration which led to a better air–fuel mixture, better evaporation rate, and less flame residence that contributed to reduce the accumulated heat loss in combustion chamber. Furthermore, a low common rail pressure was found to induce a greater difference in the accumulated heat flux ratio than a high common rail pressure which is owing to longer flame residence time in the combustion chamber. They were approximately 14% and 6% greater than that compared to the baseline common rail pressure which mean that a high common rail pressure contributes for the improving thermal efficiency in spray combustion.

Implementation Strategies for Sustainable Vehicle Fleet Management

Abstract Research purpose. Against the backdrop of climate change, pressure is growing in the transport sector to reduce CO2 emissions. Numerous companies are therefore setting specific targets to curb the CO2 emissions of their own vehicle fleets. As a rule, this requires the replacement of combustion vehicles by vehicles with alternative drives. In addition to the selection of suitable technologies, economic aspects play a prominent role in this transformation process. Based on a practical case study, potential implementation strategies for achieving a specific CO2 target are to be examined for a parcel service provider. The focus here is on a fleet of diesel combustion vehicles from the small van class with a permissible total weight of fewer than 3.5 tons, which are to be replaced by vehicles with electric drive (BEV) in order to achieve a specific CO2-savings target. The research objective can be easily extended if one considers, on the one hand, that climate protection cannot be limited to individual countries but has to take place on a global level and, on the other hand, that sustainable strategic planning of vehicle fleets also concerns other vehicle segments, such as company cars for individual transport or trucks with higher permissible gross weights. Design / Methodology / Approach. In the first step, framework conditions and criteria are defined that are needed for an evaluation of the implementation strategies. In the second step, a practical case study is constructed. In the third step, different scenarios and strategies for the conversion of the vehicle fleet are designed in order to achieve the set CO2-emission targets. In the last step, the economic and ecological effects of the different strategies and scenarios are measured and analysed with the help of the calculation tool "DIPO-tool", which was developed at the Ludwigshafen University of Business and Society LUBS for research and teaching purposes. To evaluate sustainability, in addition to the established metrics for Tank-to-Wheel (TtW) and Well-to-Wheel (WtW), a holistic life cycle approach is implemented that takes into account emissions during vehicle production. Findings. Against the backdrop of expected further technological development and numerous parameters with a considerable leverage effect on economic and ecological evaluation criteria, it seems advisable from the point of view of sustainability to use alternative drives as soon as possible. From the point of view of economic efficiency, a more differentiated picture emerges depending on the framework conditions, e.g., subsidies. Originality / Value / Practical implications. The originality of the approach lies in the application of a practical case study and the attempt to reduce the complexity of the decision problem by using an Excel-based calculation tool. The value of the study lies in the realisation that, due to the complexity, a simple optimisation approach does not seem viable but rather the evaluation and analysis of different scenarios. The practical impact can be described in the sense that the used DIPO-tool can provide effective support for sustainable implementation strategies for vehicle fleets.

Preparation and properties of graphene composite lubricants additive used for cylinder liner in marine diesel burning low sulfur fuel oil

In recent years, abnormal wear issues have emerged in cylinder liner-piston rings (CL-PRs) in marine diesels that burn low-sulfur fuel oils (LSFO). To address this issue, a graphene-attapulgite composite additive was prepared and characterized as detailed in this report. Then, the tribological properties and corrosion resistance of this graphene-attapulgite were investigated when it was used at various concentrations as a multifunctional composite lubricant additive in simulated LSFO lubrication conditions. It was found that the appropriate concentration of the additive in a lubricant produced excellent anti-friction and anti-wear properties. This was when the additive was at 0.25 wt% concentration in normal lubricating conditions, where the friction coefficient and wear mass loss were reduced by 22.7% and 44.1%, respectively. Additionally, the impermeability of the graphene additive was found to improve the corrosion resistance of the lubricant. These findings revealed the mechanism of the graphene-attapulgite additive for friction reduction and corrosion resistance of cylinder liner in simulated LSFO lubrication conditions, which provided an inhibition method to prevent abnormal wear of cylinder liner in marine diesel burning LSFO.

Synthesis of magnetic carbon composite by diesel engine and its application to dye removal

We report a one-step and efficient method to synthesize magnetic diesel particles (MDPs) and their application toward dye removal. The MDPs were obtained by the combustion of ferrocene-doped diesel fuel using an internal combustion engine. The diesel particles combined with ferrocene as a metal source were collected by an electrostatic precipitator. The thermogravimetric analysis confirmed the ferrocene-based catalyst and thermal stability of MDPs. FE-SEM showed irregular and aggregated morphologies, and the presence of iron oxide phases (Fe4O3 and γ-Fe2O3) was confirmed by X-ray diffraction analysis. The characteristics of MDPs as an adsorbent for organic pollutants were evaluated by methylene blue (MB) adsorption experiments. Langmuir isotherm and pseudo-second-order models best interpret the adsorption process and kinetics, respectively, with a maximum adsorption capacity of 40.81 mg/g of MB adsorbed on the surface of magnetic diesel particles.

Evaluating the Operating Parameters of a Compression Ignition Engine Fueled With Waste Cooking Oil—Diesel Blends Using Artificial Neural Network and Ensemble Methods

Abstract Fossil fuels being the primary source of energy for industrial and power sectors are being consumed at an alarming rate. There is a dire need to search for alternative fuels and optimize the performance parameters of internal combustion (IC) engines. Traditional methods of testing and optimizing the performances of IC engine are complex, time-consuming, and expensive. This has led the researchers to shift their focus to faster and computationally feasible techniques like soft computing (SC) and machine learning (ML) algorithms, which predict the optimum performance with a substantial accuracy. This study focuses on the implementation of artificial neural network (ANN) and ensembling methods (random forest regression and extreme gradient boosting algorithm) modeling of a compression ignition (CI) diesel engine run on waste cooking oil (WCO). A single-cylinder, four-stroke, variable compression ratio diesel engine's performance, combustion, and emission parameters have been predicted using ANN and ML approaches. These models have been developed to predict the brake power, brake thermal efficiency, brake-specific fuel consumption, ignition delay, combustion duration, carbon monoxide, carbon dioxide, and oxides of nitrogen. All the models have been trained by tuning and optimizing a different number of hyper-parameters and training algorithms (Levenberg–Marquardt (LM), scaled conjugate gradient, and Broyden–Fletcher–Goldfarb–Shanno). Further the most optimum parameters have been selected using hyper-parameter optimization. The mathematical models are assessed for their generalization capability by subjecting them to a set of new testing data.

A numerical study of piston bowl geometry and diesel injection timing in a heavy-duty diesel/syngas RCCI engine

The current numerical study aims to examine the single and combined effects of various piston bowl geometries, diesel main Start of Injection (SOI) timing, and syngas energy ratio on the combustion characteristics, specific emissions (g/kW·h), energy distribution, and exergy of a heavy-duty off-road Reactivity-Controlled Compression Ignition (RCCI) diesel engine. The examined geometries include the stock chamber (baseline combustion chamber), wide-shallow chamber, dual-swirl chamber, stepped-lip chamber. The main SOI timing was varied from −20 to −5 Crank Angle (CA) After Top Dead Center (ATDC) with 5 CA steps. Also, syngas energy ratio including 0% Conventional Diesel Combustion (CDC) mode, 20%, 40%, and 60% of total fuel energy per cycle. To accomplish this goal, the SAGE combustion model coupled with a reduced chemical kinetic mechanism consists of 360 reactions, and 72 species was applied to conduct this investigation. The numerical findings showed that the use of the wide-shallow chamber extended the engine operable range under diesel-syngas combustion operating conditions. In comparison to the baseline CDC case, the application of the dual-swirl chamber under CDC conditions, and main SOI timing of −15 CA ATDC led to reduction of Carbon Monoxide ([Formula: see text]), Hydro-Carbon ([Formula: see text]), Particle Matter ([Formula: see text]), Carbon Dioxide ([Formula: see text]), Indicated Specific Energy Consumption (ISEC), Gross Indicated Efficiency (GIE), and exergy efficiency but with a Nitrogen Oxides ([Formula: see text]) penalty rate. In general, an increase in the bore to bowl diameter ratio caused a shorter ignition delay period and combustion duration. The utilization of the stepped-lip chamber at both CDC and diesel-syngas combustion operating modes resulted in a shorter ignition delay period, but a longer combustion duration. Nonetheless, the stepped-lip combustion chamber reduced the diffusive flame temperature. Also, it is noteworthy that the utilization of the stock chamber along with the main SOI timing at −5 CA ATDC under diesel-syngas 60% combustion mode is a suitable technique to pass EURO-VI [Formula: see text] and [Formula: see text] emissions regulations.

Soot formation and effect on engine oils

Introduction. During the combustion of diesel fuel in a diesel engine with an increased fuel supply, as a result of its incomplete combustion, soot particles are formed, which are either released into the atmosphere or inevitably enter the engine oil. Soot, polluting the engine oil, causes a change in its quality indicators. Soot is very small particles formed by a complex reaction mechanism in the flame of a fuel-rich region during the combustion of hydrocarbons in the absence of air, mainly consisting of a mixture of amorphous carbon and organic matter.Materials and methods. This paper presents the results of a literary review aimed at studying the ways of soot occurrence during the operation of diesel engines, its effect. The mechanical properties of diesel soot are also discussed on the surfaces of friction pairs and engine components.Conclusions. The soot content in engine oil will increase sharply in engines with exhaust gas recirculation, which leads to an increase in temperature in the friction zones and viscosity of the lubricant, as well as to the formation of deposits on hot parts. These processes occur due to the discharge in the crankcase space and the intensification of the intake of gases from the combustion chamber. Oil change intervals should be monitored at an increased rate of soot entering the engine oil.Scope of the study / opportunity. This type of study will help determine the causes of soot in a diesel engine, understand the consequences of using engine oil contaminated with soot particles.Originality / value. The conducted research can be the basis for the development of recommendations for improving the maintenance of internal combustion engines for enterprises that have cars with diesel engines at their disposal in order to increase the resource of power units and reduce operating costs.

An optical study of the combustion and flame development of ammonia-diesel dual-fuel engine based on flame chemiluminescence

Under the background of the “carbon peak and carbon neutrality”, the development and utilization of zero-carbon fuels, represented by green ammonia and green hydrogen, has gained attention from all walks of life. Among them, the problems of transportation and storage of hydrogen restrict its industrial development, while ammonia has significant advantages as a suitable hydrogen energy carrier for the power systems. The ammonia-diesel dual-fuel engine enables the mixture to be stratified in a time-activated multi-point ignition mode to promote efficient and clean combustion of ammonia. To investigate the combustion and flame development of the ammonia-diesel dual-fuel engine, an optical diagnostic study was carried out on a self-refit dual-fuel optical engine. The results show that the combustion inertia and lower flame temperature of ammonia can inhibit combustion and lead to lower cyclic heat release in the ammonia-diesel dual-fuel combustion (ADDC) mode, which in turn reduces the indicated mean effective pressure (IMEP). Different from the yellow-white flame produced by the high-temperature soot radiation in pure diesel combustion (PDC) mode, the flame in the ADDC mode appears orange. The peak of flame area (FR) percentage and flame natural luminosity (FNL) of the 80% ammonia ratio ADDC mode decrease by 60% and 92%, respectively, compared to the peaks at PDC mode. The ammonia combustion flame is mainly concentrated around the diesel flame, and at the same time achieves good ignition performance at all ammonia ratios. In contrast to the PDC mode where the FR and FNL decrease rapidly as the diesel injection timing (DIT) advances, the flame pattern of the ADDC mode does not respond significantly to the DIT.