Research Engine Research Articles

Comparative Evaluation of the Effect of Exhaust Gas Recirculation Usage on the Performance Characteristics and Emissions of a Natural Gas/Diesel Compression-Ignition Engine Operating at Part-Load Conditions

The use of natural gas as an alternative fuel in dual-fuel compression-ignition engines can lead to a substantial reduction in the majority of pollutant emissions compared to fossil fuels, while the thermal efficiency of the engine can be maintained at adequate levels. Its usage has increased widely in recent years, and significant efforts have been made to investigate the inherent physical and chemical processes that take place during this engine’s combustion, as well as the parameters that affect the operation of the engine and use natural gas as energy source. The scope of this study is to investigate the effect of EGR temperature (cold and hot) and rate (10% and 20%) on the performance characteristics and emissions of a dual-fuel compression-ignition engine operating at a specific engine operating point under dual-fuel (diesel–natural gas) conditions. For this reason, a phenomenological two-zone combustion model was developed. The results of the model were validated against the experimental data obtained from a single-cylinder direct-injection, turbocharged compression-ignition dual-fuel research engine operated under part-load conditions (IMEP = 0.52 Mpa and engine speed = 1500 rpm) and at various replacement percentages of diesel using methane (which was treated as a natural gas surrogate). The model results were in good agreement with the experimental results, revealing the ability of the model to be used in the aforementioned EGR analysis. The results of the study revealed that engine operation with 10% cold EGR does not significantly affect the engine performance characteristics, and combined with the addition of 80% gaseous fuel energy, can lead to a substantial reduction in NO and soot emissions, with a moderate increase in CO emissions. On the other hand, a significant finding of the present work is that engine operation with hot EGR under the investigated operating conditions, even though it had a beneficial effect on NO-specific emissions, led to a reduction in engine efficiency and may raise issues regarding the mechanical strength of the engine.

Operation of a Compression Ignition Engine at Idling Load Under Simulated Cold Weather Conditions

Abstract Heavy-duty compression ignition (CI) engines can be subject to long periods of idling during their duty cycles. In colder climates, getting the engine and exhaust aftertreatment (EAT) system to ideal operating temperatures can be challenging under such idling and low load conditions. This may lead to high emissions of criteria pollutants especially nitrogen oxides (NOx). Increasing the engine load and idling speed may help mitigate NOx emissions but typically leads to higher greenhouse gas emissions. Therefore, the objective of this study is to evaluate the performance of a heavy-duty CI engine operating at various idling conditions and determine suitability for exhaust aftertreatment system operation. Tests are conducted on a heavy-duty single cylinder CI research engine fueled with diesel. As per the United States' (U.S.) Code of Federal Regulations (CFR), CI engines can be certified for the optional Clean Idle NOx emission standard. A corresponding two-mode Clean Idle Test (CIT) is specified in CFR which requires the engine to be operating in fully warmed-up condition at two engine speeds. Steady-state tests are conducted at these two engine speeds of 650 and 1100 rpm, and cold weather operation is simulated by operating the engine at suboptimal coolant, lubricant, and intake air temperatures. The steady-state tests are used to determine suitable diesel injection timing for performing the CIT under standard and simulated cold weather conditions. At the lowest load and 650 rpm idling speed, use of multiple injections and exhaust gas recirculation (EGR) are insufficient for raising the exhaust gas temperature above 200 °C. A combination of higher load, EGR, and 1100 rpm idling speed can create conditions for light-off selective catalytic reduction (LO-SCR) operation at the expense of higher fuel consumption. The modified CIT results show that the optional Clean Idle NOx emission standards can be met with the use of EGR at both test modes. The mode 2 conditions at 1100 rpm may allow LO-SCR activation as well. There are also distinct differences between results under fully and partially warmed-up conditions.

A Survey of Research on Vibration Friction Reduction Technologies in Aero-Engines

The performance and reliability of an aviation engine, as a core component of an aircraft, is of paramount importance to flight safety. Scholars worldwide have contributed to the design and research of aviation engines, and these advancements and contributions embody the relentless efforts and innovative spirit of scholars and engineers in the field of aviation engine design research. In recent studies, researchers have proposed various vibration control methods to address friction issues in aviation engines, offering corresponding control strategies for the aspects of materials, lubrication, and structural design. However, how to reduce the loss of service life and the safety risks caused by friction in aircraft engines has become an urgent issue that needs to be addressed in the aviation sector. This paper briefly analyzes the current development status regarding vibration and friction reduction in aircraft engines, explores key technologies and research progress in addressing this challenge, and provides insights and prospects for future developments. With advancements in technology, research into vibration and friction in aviation engines will continue to deepen, providing strong support for the development of the aviation industry.

Spatial planning in the face of natural and technological disasters: a literature review

ABSTRACT A growing concern about disasters triggered by natural phenomena and technological accidents is evident over the last decades. These disasters are increasingly common and severe nowadays, partly due to the impact of climate change, which is exacerbated by the continuing human pressure on the environment. Spatial planning is believed to play a key role in disaster prevention with discussions about the integration of risk analysis and management in spatial planning processes being discussed relevantly recently. Nevertheless, it is still inconsistent. This is a literature review paper about the integration of prevention and management of natural/technological disasters in spatial planning. The authors performed extensive research in scientific search engines, using relevant keywords in a combined way, for more targeted results. Following a bibliometric analysis of 382 documents/papers, some of the major findings are: the topic gained momentum after 2006, most of the literature examines topics of prevention combined with management, the most researched disaster is floods and disaster risk management is usually discussed in combination with urban planning. Only about 5% of the publications refer to maritime spatial planning and merely around 3% of the research is solely dedicated to technological disasters, indicating that these topics are suitable for future research.

Artificial Neural Networks as a Tool for High-Accuracy Prediction of In-Cylinder Pressure and Equivalent Flame Radius in Hydrogen-Fueled Internal Combustion Engines

The automotive industry is under increasing pressure to develop cleaner and more efficient technologies in response to stringent emission regulations. Hydrogen-powered internal combustion engines represent a promising alternative, offering the potential to reduce carbon-based emissions while improving efficiency. However, the accurate estimation of in-cylinder pressure is crucial for optimizing the performance and emissions of these engines. While traditional simulation tools such as GT-POWER are widely utilized for these purposes, recent advancements in artificial intelligence provide new opportunities for achieving faster and more accurate predictions. This study presents a comparative evaluation of the predictive capabilities of GT-POWER and an artificial neural network model in estimating in-cylinder pressure, with a particular focus on improvements in computational efficiency. Additionally, the artificial neural network is employed to predict the equivalent flame radius, thereby obviating the need for repeated tests using dedicated high-speed cameras in optical access research engines, due to the resource-intensive nature of data acquisition and post-processing. Experiments were conducted on a single-cylinder research engine operating at low-speed and low-load conditions, across three distinct relative air–fuel ratio values with a range of ignition timing settings applied for each air excess coefficient. The findings demonstrate that the artificial neural network model surpasses GT-POWER in predicting in-cylinder pressure with higher accuracy, achieving an RMSE consistently below 0.44% across various conditions. In comparison, GT-POWER exhibits an RMSE ranging from 0.92% to 1.57%. Additionally, the neural network effectively estimates the equivalent flame radius, maintaining an RMSE of less than 3%, ranging from 2.21% to 2.90%. This underscores the potential of artificial neural network-based approaches to not only significantly reduce computational time but also enhance predictive precision. Furthermore, this methodology could subsequently be applied to conventional road engines exhibiting characteristics and performance similar to those of a specific optical engine used as the basis for the machine learning analysis, offering a practical advantage in real-time diagnostics.

Perceived Sexual Health Needs of Older Women: A Systematic Review

Background: Maintaining and promoting sexual health in older women requires paying attention to and meeting their sexual health-related needs. This study aimed to determine older women’s perceived sexual health needs through a systematic review. Materials and Methods: In this systematic review, studies conducted from the beginning of 2000 to August 28, 2022, were searched in Databases, Scopus, Web of Science, SID, Pub Med, and Google Scholar as a research engine. To access all English articles, keywords such as sexual health, sexual performance, sexual intercourse, sexual, need, demand, and women and their possible combinations were used using “AND” and “OR” operators. This research was implemented based on the criteria of the PRISMA checklist. The articles were evaluated using the STROBE and COREQ checklists. The thematic synthesis method was used to synthesize the data. Results: The sexual health needs of older women were categorized into four groups: restoration of violated sexual rights, elimination of age discrimination (ageism), promotion of sexual health literacy, and providing sexual health services. Conclusions: The sexual needs of older women have been neglected due to prevailing social structures of many countries, stigma, gender discrimination, and lack of sexual health literacy. In addition to the need for social and emotional support to adapt to the conditions of old age, these women need to achieve sexual rights, improve sexual health literacy, and receive health services.

Gaps Manifesting in African Social Work: Eclectic Contexts in Africa

Although the discipline of social work is pivotal in rejuvenating socio-economic welfare in ubiquitous corners of the world, it has paradoxically scored poorly in managing and leveraging welfare-based interventions in many African countries. The paper aims to discuss social work gaps in social welfare in some African countries. The paper used a review of the literature methodology that drew variegated literature from different research engines such as Google Scholar, EBSCOhost, Research Gate, and a few books and book chapters. The study has the following findings: poor professional conceptualisation, inadequate social workers in African countries, social work’s visibility deficits compared to its sister disciplines, absence of social workers in institutions of learning, poor policy and leadership involvement, social work gap in dealing with indigents, and social work suffers from gender stereotyping. The paper recommends that for social work to leverage its service delivery interventions, a collaboration between the forces of government NGOs and other social service professional bodies is necessary. The paper also advocates that the discipline be catapulted to its noble and honorable status as a very important discipline that enhances and turns around the service delivery process for a country’s citizens. The paper is very important for scholarship in that its content will add knowledge to the domain of social work by offering suggestions for leveraging social work service delivery, as well as informing policy and programmatic improvement in social work service delivery in the countries discussed. Keywords: Social Work Obscurity, Inadequate Training, Professional Visibility, Gender Stereotyping, Paradigm Shift, Poverty.

In- and near- nozzle and external flow characterization in Gasoline Direct injection (GDi) engines – A review of latest technologies and trends. Part 1: Experimental background

In an era of increasingly stringent emissions regulations, environmental standards are driving gasoline engine research and development toward more widespread use of direct injection systems. It is also of interest to know what kind of phenomena cause these types of emissions in order to address and reduce them as much as possible. Therefore, it has been considered of interest to summarize in this article the latest research topics related to the gasoline direct injection (GDI) process, providing researchers with a valuable resource to understand the current state of research, the different technologies of gasoline direct injection and the phenomena that take place in this process. Research applied to GDI engines can be approached in several ways. The one chosen for this article is mainly based on separating the relevant processes within the engine with the objective of going deeper into each of them. In this sense, it is proposed to study the injection without taking into account the combustion phenomenon. In the same way, it is suggested to study the injection process in several phases: in- and near-field of the injector and downstream of the injector. Therefore, this work performs an extensive analysis of the experimental techniques employed for the study of each of the phenomena that take place in the injection process. The objective of the research is a better understanding of the phenomena, an improved characterization of the internal flow and spray and consequently the final optimization of the engine design. In a subsequent publication (Part 2), the same literature review will be addressed but only taking into account the computational work carried out in recent years with the same objective of investigating the injection, the mixture formation process, and the associated emissions characterization.

Impact of Mental Health on Skin Disorders: Investigating the Bidirectional Relationship Between Stress and Conditions like Acne, Vitiligo, and Psoriasis

There is a close connection between skin diseases and mental health. This connection has recently gained the attention of researchers. The main objective of this study is to review the updates of cited literature about the impacts of mental health on skin disorders. The research team used the most popular research engines including Science direct, Pub med, Google Scholar, and others to extract the appropriate materials to make this article. The results of cited literature emphasized the existence of bidirectional relationship between mental health and skin disorders. This means that either of them will impact the other. Stress is a common factor in both.

Childhood Eczema Triggers: Role of Early-Life Dietary and Environmental Exposures

Eczema is common in childhood, with a prevalence of approximately 15% in Western industrialized countries. The objective of this review study was to explore the updates of the literature towards childhood eczema triggers. To achieve this objective, the research team employed the main research engines including Science direct, Pub Med, Google Scholar, Springers, and others. This review included several topics such as biological and environmental factors leading to eczema. The cited literature showed that childhood eczema is a world-wide problem. Therapeutic options are varied among individuals. Food and environmental factors are important factors that participate in the development of eczema.

Advancements in Pediatric Hematology and Oncology

Pediatric hematology and oncology is the medical subspecialty that focuses on the identification, management, and research of various blood disorders and pediatric cancer. The main objective of the present study was to review the updates of literature regarding the main topic of this study. The researchers employed the main research engines such as Science Direct, pub med, Google Scholar, and others to reveal the appropriate cited literature. The results of this review showed that pediatric hematology and oncology has common features with the general hematology and oncology. The researchers discussed in this study diagnostic and therapeutic strategies. Innovative intervention studies were also discussed.

Advancements in Pediatric Allergology and Immunology

Pediatric allergology and immunology have emerged as a distinct subspecialty and addressed the necessity of studying allergic and immunologic disorders in the pediatric population, further progressing therapeutic regimens and treatment approaches, especially for children. The main objective of this study was to review the updates of the literature regarding the advancements of pediatric allergology and immunology. Main research engines were employed to extract the appropriate data. Literature showed the importance of this topic and its diagnosis and therapeutic approached.

Effects of injection timing on combustion and mixture formation of a methanol direct injection engine equipped with a small volume passive pre-chamber

The pursuit of high efficiency and cleanliness has always been the focus of engine research. As one of the most promising low-carbon renewable alternative fuel, methanol has gained increasing attention in engine applications. Inspired by the advantages of gasoline direct injection (GDI) in fuel economy, methanol direct injection (MDI) engine has also become a research hot spot. Similar to GDI, the mixture distribution is crucial for MDI engines, especially in the late injection stratified operation mode, an unreasonable mixture distribution of rich and lean regions will result in slow and incomplete combustion, or even flame quenching. Due to the characteristics of multi-point ignition and the high ignition energy, pre-chamber jet flame ignition has the potential to effectively enhance combustion. In this paper, the effect of injection timing on combustion characteristics in a methanol direct injection engine equipped with a small volume pre-chamber are studied experimentally. The mixture formation processes in both the main-chamber and the pre-chamber at different injection timings were also explored through simulations. The research findings indicated that the engine exhibits optimal power performance at the injection timing of − 270 °CA ATDC (after top dead center), primarily attributed to the enhanced volumetric efficiency and improved mixture homogeneity. However, the mixture concentration in the pre-chamber is leaner, resulting in the longest ignition delay period. When the injection timing is located on the middle state of the intake stroke, specifically − 210 °CA ATDC, the ignition delay period is the shortest, indicating that the mixture concentration and temperature in the pre-chamber are conducive to the flame kernel formation and flame propagation. In addition, the volumetric efficiency of this injection case is maximized due to the combined effects of spray-wall interaction, spray-air interaction, and the flow field. When injection occurs on compression stroke, the mixture concentration in the pre-chamber is higher; however, there exists a significant and discontinuous concentration gradient in the main-chamber, which limits the enhancement of the flame propagation speed and the combustion efficiency, especially for − 120 °CA ATDC injection case, the engine exhibits longest combustion duration and the lowest IMEP. The conclusions can provide theoretical basis and empirical data support for enhancing the combustion of methanol direct injection engines equipped with passive pre-chambers.

Turbofan engine health status prediction with artificial neural network

The main purpose of this study is to present the concept of the aircraft turbofan engine health status prediction with artificial neural network augmentation process. The main idea of engine health status prediction is based on the engine health status parameter broadly used in the aviation industry as well as propulsion technology being the performance and safety margin. As a result of research engine health status index is calculated in order to determine the engine degradation level. The calculated parameter is then used as a response parameter for the machine learning algorithm. The case study is based on the artificial neural network which was two-layer feedforward network with sigmoid hidden neurons and linear output neurons. Network performance is evaluated using mean squared error and regression analysis. The final results are analyzed using visualization plots such as regression fit plot and histogram of errors. The greatest achievement of this elaboration is the presentation of how the entire process of engine status prediction might be augmented with the use of an artificial neural network. What is the greatest scientific contribution of the article is the fact that there are no scientific studies available, which are based on the engine real-life operating data.

OPERATING PECULIARITIES OF STANDARD COOLING SYSTEMS OF ENGINES AT HIGH ALTITUDES

The item under test was the engine without its standard facility-based cooling systems, the lack of which makes it impossible to operate as a power unit of a vehicle in a great majority of experimental research of internal combustion engines at high altitudes. The findings may create a wrong impression of the range of power ratings and economic parameters of the engine when operating at high altitudes because changes in atmospheric conditions exert an effect on the running efficiency of its standard systems as well. It is established that the efficiency loss of the cooling system may cause a forced power limitation of the engine as a result of the experimental research of the diesel engine equipped with all standard facility-based systems at very high altitudes. Thus, the shortage of power may significantly exceed the power loss of the engine due to air density reduction at high altitudes.

Surrogate model-driven multi-parameter optimization of four distinct combustion chambers in a four-stroke diesel engine

The reduction of emissions from compression ignition (CI) engines is a major area of research in response to increasing environmental regulations and the need for cleaner energy solutions. This study presents a comprehensive computational fluid dynamics (CFD) study on a sector combustor of a CI engine, focusing on the effects of injection parameters and combustion chamber design on emissions. Four distinct combustion chamber designs—rectangular, shallow depth combustion chamber (SCC), hemispherical combustion chamber (HCC), and toroidal combustion chamber (TCC)—were analyzed. Key parameters such as tumble ratio, swirl ratio, cross-tumble ratio, soot formation, and NOx emissions were observed and compared. This study uniquely combines a comparative analysis of these combustion chamber designs with an advanced optimization of injection parameters using a Multi-Objective Genetic Algorithm (MOGA), an approach not widely explored in previous CI engine research. Additionally, response surface methodology (RSM) and design of experiments (DOE) were employed to gain further insights into the influence of individual variables, providing a thorough understanding of their impact on emissions and combustion performance. The results show that SCC chambers are most effective at reducing soot emissions, while TCC designs are better at lowering NOx emissions. Later injection timings showed a 450% decrease in soot rate compared to earlier timings, whereas NOx has significantly benefited from earlier injections, which presented about a 1600% difference in the NOx production when compared to late injections. These findings offer valuable contributions to the design of cleaner and more efficient CI engines, with the potential to significantly impact future engine development.

Experimental and artificial neural network (ANN) study on the impact of three different metal oxide nanoparticle combustion enhancers enriched on mahua biodiesel-diesel fuelled CI engine

Abstract The prediction of CI engine parameters has acquired significant attention and is regarded as a crucial tool for engine research and diagnosis studies. This contribution compares two different approaches for diesel engine viz. experimental and artificial neural networks (ANNs) predictions of performance and emission outputs. The base fuel M30 blend consist of mahua biodiesel 30 (% v) and 70 (% v) of diesel. The M30 blend and 50 ppm concentration of NPs (CeO2, CuO, and TiO2) were chosen for basic experimentation. The findings indicate an increase in BTE by 9.1%, peak CP by 11.3%, and HRR by 10.2%, with a decrease in BSFC by 13.7%, CO by 30.4%, HC by 30.1%, smoke by 34.7%, and NOx by 7.1%, resulting from the addition of 50 ppm CeO2 NP to D70M30 blend. The widely used backpropagation technique for ANN is implemented in multilayered feedforward design. To forecast the engine characteristics of a CI engine, a network structures including two inputs and one output is used. The given ANN model examined D100, M30, M30CeNP50, M30CuNP50, and M30TNP50 blends, using engine load and biodiesel with nanoparticle blend as the two input factors. A data-driven ANN model was created to forecast the optimised engine characteristics. The lowest and highest value of correlation coefficient (R2) and mean square errors (MSE), mean relative error (MRE) were found to for peak CP, HRR, BTE, BSFC, CO, CO2, HC, NOx and smoke. Using ANN one can choose right blend ratio among the variety of fuels blends for an appropriate requirement without much experimentation.

Kinetic study of the combustion process in internal combustion engines: A new methodological approach employing an artificial neural network

The comprehension of combustion mechanisms enables supervision of reaction rates. By adjusting factors such as heat transfer rates, combustion duration, self-ignition propensity, ignition delay and laminar flame speeds, it is possible to minimize emissions and enhance fuel conversion efficiency in internal combustion engines (ICE). The present study aims to develop and explore a methodology employing an Artificial Neural Network that uses Mass Burned Fraction data as a function of crankshaft angular position to determine combustion kinetics in ICE. The Artificial Neural Network was programmed in this work as a home-made code and produced accurate results. The kinetic triplet consisting of Activation Energy (Ea), Frequency Factor (A) and Reaction Model throughout the combustion process was determined to explore the combustion characteristics of different gasoline formulations and ICE operation conditions. The experimental data were obtained in a Single Cylinder Research Engine (SCRE) operating with gasoline formulations commercialized in Brazil. The methodology determines the kinetics of combustion along the process and recovers the values of Ea and A without resorting to mechanisms that describe each reaction individually, describing, instead, the global contribution of physical models. Because the kinetic models activate the neurons in the hidden layer, they accurately reproduce the experimental Mass Burned Fraction data and bring physical information to the network about the combustion process. The kinetic study showed that the samples with higher values of Ea also had higher ignition delay. The rate constant was also related to the consumption and combustion efficiency during the combustion process, i.e., the fuel with a higher rate constant presents greater combustion efficiency and smaller consumption.

Octane Response of Gasoline Fuels to Different Anti-knock Oxygenates Addition

Abstract A series of renewable and clean oxygenated compounds possessing high octane numbers, including alcohols, ethers, esters and furans, were used as octane boosters for gasoline fuels, and the octane responses of the gasoline fuels to these oxygenates addition were evaluated. Gasoline model fuels of different typical hydrocarbon compounds, including iso-octane, n-heptane, toluene, diisobutylene, and cyclohexane, were designed to have the identical octane rating. The research octane number (RON) and motor octane number (MON) of the gasoline model fuels with anti-knock oxygenates addition were experimentally measured on a standard cooperative fuel research (CFR) engine. The results highlight the varied impact of anti-knock oxygenates on the octane enhancement of gasoline fuels, with 2-methylfuran exhibiting the most pronounced RON boost effect and ethanol demonstrating the strongest MON enhancement effects, and isopropyl ether and dimethyl carbonate shows the weakest RON and MON boost effects, respectively. The anti-knock enhancement effects of the oxygenated additives are dependent on gasoline fuel compositions. With the anti-knock oxygenates addition, PRF model fuel shows more significant octane enhancements, and the octane boosting effects are reduced for the gasoline model fuels containing toluene or diisobutylene, indicating an antagonistic interaction between the oxygenates and toluene/diisobutylene. By comparing the octane enhancement effects of the tested anti-knock additives, it is evident that 2-methylfuran and ethanol are the more superior anti-knock candidates for gasoline fuels.

Modeling of Hydrogen Combustion from a 0D/1D Analysis to Complete 3D-CFD Engine Simulations

Hydrogen and its unique properties pose major challenges to the development of innovative combustion engines, while it represents a viable alternative when it is based on renewable energy sources. The present paper deals with the holistic approach of hydrogen combustion modeling from a 0D/1D reactor evaluation with Cantera up to complete engine simulations in the 3D-CFD tool QuickSim. The obtained results are referenced to the current literature and calibrated with experimental data. In particular, the engine simulations are validated against measurements of a single-cylinder research engine, which was specifically adapted for lean hydrogen operation and equipped with port fuel injection and a passive pre-chamber system. Special attention is hereby given to the influence of different engine loads and varying lambda operation. The focus of this work is the complementary numerical investigation of the hydrogen flame speed and its self-ignition resistance under the consideration of various reaction mechanisms. A detailed transfer from laminar propagation under laboratory conditions to turbulent flame development within the single-cylinder engine is hereby carried out. It is found that the relatively simple reaction kinetics of hydrogen can lead to acceptable results for all mechanisms, but there are particular effects with regard to the engine behavior. The laminar flame speed and induction time vary greatly with the inner cylinder conditions and significantly affect the entire engine’s operation. The 3D-CFD environment offers the opportunity to analyze the interactions between mixture formation and combustion progress, which are indispensable to evaluate advanced operating strategies and optimize the performance and efficiency, as well as the reliability, of the engine.