Modern Diesel Engines Research Articles

Advanced Methods for Monitoring and Fault Diagnosis of Control Loops in Common Rail Systems

Common rail systems are a key component of modern diesel engines and highly increase their performance. During their working lifetime, there could be critical damages or failures related to aging, like backlash or friction, or out-of-spec operating conditions, like low-quality fuel with, e.g., the presence of water or particles or a high percentage of biodiesel. In this work, suitable data-driven methods are adopted to develop an automatic procedure to monitor, diagnose, and estimate some types of faults in common rail systems. In particular, the pressure control loop operating within the engine control unit is investigated; the system is described using a Hammerstein model composed of a nonlinear model for the control valve behavior and an extended linear model for the process dynamics, which also accounts for the presence of external disturbances. Three different sources of oscillations can be successfully detected and quantified: valve stiction, aggressive controller tuning, and external disturbance. Selected case studies are used to demonstrate the effectiveness of the developed methodology.

SCIENTIFIC-TECHNICAL AND PRODUCTION POTENTIAL OF UKRAINE FOR THE PRODUCTION OF SCIENTIFIC PRODUCTS OF DIESEL CONSTRUCTION

In this work, an attempt is made to provide an assessment of the prospects for the development of automotive diesel engineering in Ukraine, the availability and preservation of scientific, technical and production potential for the continuation of the production of knowledge-intensive products of this domestic sub-industry in modern conditions. According to the authors, the manufacturers of vehicles in Ukraine quickly found the support of the State regarding the inclusion of the relatively most complex structural units of the car design - the engine and the chassis - in the list of imported components, since the manufacture of these parts requires high-tech processes that ensure the manufacture of low-quality parts. Other personal opinions of the authors have been expressed regarding the reasons for the absence of energy sources that ensure the economic development of the country and are considered science-intensive products in the modern domestic automotive industry. According to the results of the research, it was established that the list of developments of the domestic automotive diesel industry in recent years extends from the two-cylinder diesel engine of the ZIM-800D four-wheeled motorcycle, which was proven to be introduced into the series, and the ZIM-1901 and ZIM-1902 microcars, to the design documentation of the modern six-cylinder diesel engine 6DTNA2 with a four-valve cylinder head and electronic fuel injection system. As an example of the capacity of the domestic production potential, the production technology of the cylinder head of a four-cylinder diesel engine 4ChN 8.8/8.2 was worked out with the involvement of available production resources and the use of imported components. This approach makes it possible to significantly reduce the time for the manufacture and preparation of the production of structural elements of the domestically produced engine, which is a representative of the "Slobozhansky diesel" power series.

Traffic-related ultrafine particles impair mitochondrial functions in human olfactory mucosa cells – Implications for Alzheimer's disease

Constituents of air pollution, the ultrafine particles (UFP) with a diameter of ≤0.1 μm, are considerably related to traffic emissions. Several studies link air pollution to Alzheimer's disease (AD), yet the exact relationship between the two remains poorly understood. Mitochondria are known targets of environmental toxicants, and their dysfunction is associated with neurodegenerative diseases. The olfactory mucosa (OM), located at the rooftop of the nasal cavity, is directly exposed to the environment and in contact with the brain. Mounting evidence suggests that the UFPs can impact the brain directly through the olfactory tract. By using primary human OM cultures established from nasal biopsies of cognitively healthy controls and individuals diagnosed with AD, we aimed to decipher the effects of traffic-related UFPs on mitochondria. The UFP samples were collected from the exhausts of a modern heavy-duty diesel engine (HDE) without aftertreatment systems, run with renewable diesel (A0) and petroleum diesel (A20), and from an engine of a 2019 model diesel passenger car (DI-E6d) equipped with state-of-the-art aftertreatment devices and run with renewable diesel (Euro6). OM cells were exposed to three different UFPs for 24-h and 72-h, after which cellular processes were assessed on the functional and transcriptomic levels. Our results show that UFPs impair mitochondrial functions in primary human OM cells by hampering oxidative phosphorylation (OXPHOS) and redox balance, and the responses of AD cells differ from cognitively healthy controls. RNA-Seq and IPA® revealed inhibition of OXPHOS and mitochondrial dysfunction in response to UFPs A0 and A20. Functional validation confirmed that A0 and A20 impair cellular respiration, decrease ATP levels, and disturb redox balance by altering NAD and glutathione metabolism, leading to increased ROS and oxidative stress. RNA-Seq and functional assessment revealed the presence of AD-related alterations in human OM cells and that different fuels and engine technologies elicit differential effects.

Controlled human exposures to diesel exhaust or particle-depleted diesel exhaust with allergen modulates transcriptomic responses in the lung

The evidence associating traffic-related air pollution (TRAP) with allergic asthma is growing, but the underlying mechanisms for this association remain unclear. The airway epithelium is the primary tissue exposed to TRAP, hence understanding its interactions with TRAP and allergen is important. Diesel exhaust (DE), a paradigm of TRAP, consists of particulate matter (PM) and gases. Modern diesel engines often have catalytic diesel particulate filters to reduce PM output, but these may increase gaseous concentrations, and their benefits on human health cannot be assumed. We conducted a randomized, double-blinded, crossover study using our unique in vivo human exposure system to investigate the effects of DE and allergen co-exposure, with or without particle depletion as a proxy for catalytic diesel particulate filters, on the airway epithelial transcriptome. Participants were exposed for 2 h before an allergen inhalation challenge, with each receiving filtered air and saline (FA-S), filtered air and allergen (FA-A), DE and allergen (DE-A), or particle-depleted DE and allergen (PDDE-A), over four different occasions, each separated by a 4-week washout period. Endobronchial brushings were collected 48 h after each exposure, and total RNA was sequenced. Differentially expressed genes (DEGs) were identified using DESeq2, followed by GO enrichment and pathway analysis. FA-A, DE-A, and PDDE-A exposures significantly modulated genes relative to FA-S, with 462 unique DEGs identified. FA-A uniquely modulated the highest number (↑178, ↓155), followed by DE-A (↑44, ↓23), and then PDDE-A exposure (↑15, ↓2); 6 DEGs (↑4, ↓2) were modulated by all three conditions. Exposure to PDDE-A resulted in modulation of 285 DEGs compared to DE-A exposure, further revealing 26 biological process GO terms, including “cellular response to chemokine” and “inflammatory response”. The transcriptional epithelial response to diesel exhaust and allergen co-exposure is enriched in inflammatory mediators, the pattern of which is altered upon particle depletion.

Assessing the Benefits of Electrification for the Mackinac Island Ferry from an Environmental and Economic Perspective

Ferry electrification has gained attention in the last decade as a potential path to reduce greenhouse gas emissions. This study, conducted by APS LABS at Michigan Technological University for the Mackinac Economic Alliance (MEA) and funded by the Michigan Economic Development Corporation (MEDC), looked at the feasibility and potential benefits of electrification of a particular vessel that is part of a ferry service from Mackinaw City, Michigan, USA, to Mackinac Island, Michigan, USA. The study included a comprehensive analysis of the feasibility of retrofitting the current configuration of the ferry into an all-electric ferry based on the availability of components in today’s market. A life-cycle assessment was conducted to compare the emissions between the baseline ferry rebuilt with new internal combustion engines and an all-electric ferry to understand the potential environmental benefits of ferry electrification and find the most sustainable solution for propulsion. The final prong of the three-pronged approach to this project consisted of estimating the difference in expenditures and profits for a rebuilt internal combustion (IC) engine versus electric configurations for a company operating the ferry. The analysis indicated that in the current scenario, electrification of the Mackinac Island ferry is not beneficial, and replacing the ferry’s current diesel engines with modern diesel engines is the preferred solution.

Oxidation-induced variations in the physical and fragmentation characteristics of exhaust soot from DMC-diesel blend: Effect of NO presence in the air atmosphere

This study investigated the changes in physical properties (including morphology, primary particle diameter, fractal dimension, and nanostructure) and fragmentation characteristics of exhaust soot from a modern direct injection diesel engine fueled with diesel (D100) and its blend with 7 vol% of dimethyl carbonate (DMC7) during oxidation processes in air and air-NO atmospheres. Soot particles (D100 soot and DMC7 soot) with specific oxidation degrees (0%, 20%, 50%, and 80%) were produced using a thermogravimetric analyzer, then applied to a high-resolution transmission electron microscopy to generate images. The results exhibited that the morphology for D100 soot and DMC7 soot transformed similarly through oxidation, experiencing an increase in fractal dimension, and a decrease in primary particle diameter, while the introduction of NO to the air accelerated these transformations. Additionally, the nanostructure of both soot particles was gradually ordered through oxidation, as evidenced by longer fringe length, narrower separation distance, and lower tortuosity, while DMC7 soot showed lower order degree compared to D100 soot. Interestingly, the ordering processes of soot nanostructure were decelerated as NO was involved in the oxidation process. Furthermore, the aggregate fragmentation rate for both soot particles declined over the oxidation process, while the possibility for primary particle fragmentation increased overall. Moreover, DMC7 soot exhibited significantly lower aggregate fragmentation rate and higher possibility for primary particle fragmentation than D100 soot at the same oxidation stage. This suggests that DMC7 soot is more susceptible to internal oxidation compared to D100 soot. Furthermore, the presence of NO in the air promoted aggregate fragmentation, while reducing the possibility of primary particle fragmentation.

Проблемы диагностики современных тепловозных двигателей

Objective: to consider the issue of diagnostics of modern diesel engines, in particular vibration diagnostics. Consider modern strategies and methods based on vibroacoustic signals that allow you to track and diagnose diesel engine malfunctions, as well as an assessment of the working process in the engine. To determine which means of measuring vibration parameters and methods of processing vibration signals can be considered the most reliable and informative. Propose to make adjustments to the currently used methods of processing vibration signals. Methods: comparison of the effectiveness of vibration measurement tools and mathematical methods of vibration signal processing. Results: the necessity of choosing mathematical methods of vibration signal processing is indicated, both for individual components of a diesel locomotive engine and for evaluating the workflow. Modern mathematical methods, applied to vibration diagnostics, require updating, due to an increase in computing power, as well as due to the development of powerful signal processing methods. To increase the reliability of the comparison results, it is necessary to take into account the large variability of the components and processes of the diesel engine. The need for additional study of modern mathematical methods of vibration signal processing is revealed. Practical importance: the necessity of introducing more modern methods of vibration signal processing is shown, which will optimize the durability of the components’ design using long operating cycles, reduce maintenance costs, track the service life of the internal combustion engine during the operation of the locomotive, improve the monitoring and diagnostics systems of the locomotive engine. The presented methods of assessing the use of certain methods of vibration diagnostics for diesel locomotives can be recommended for practical use.

Potential of 2-ethylhexyl nitrate (EHN) and di-tert-butyl peroxide (DTBP) to enhance the cetane number of ethanol, a detailed chemical kinetic study

Ethanol is one of the most promising renewable liquid fuels to decarbonize the internal combustion engine due to its high production capacity, reasonable cost and low carbon intensity. At the same time, diesel engines are preferred over other powertrain technologies in most hard-to-electrify applications, such as heavy-duty, off-road, marine and rail. However, ethanol’s properties are not suitable for modern diesel engines with ignitability being the main technical barrier for ethanol compression-ignition combustion. Cetane improvers, such as 2-ethylhexyl nitrate (EHN) or di-tert-butyl peroxide (DTBP) may be a solution to enable diesel-like ethanol combustion, but the potential of those additives to increase the cetane number of ethanol is still unclear.In this investigation, detailed chemical kinetic simulations were performed to better understand the mechanisms by which EHN and DTBP affect the ignition reactivity of ethanol. Sub-models of EHN and DTBP chemistry were merged with a chemical kinetic mechanism for ethanol and validated against experimental data. Rate of production analyses and sensitivity analyses were performed to better understand the reactions and species that control the autoignition of ethanol additized with EHN or DTBP. The formation and accumulation of acetaldehyde from ethanol-derived radicals is the bottleneck for ignition, since the remaining ethanol acts as a sink of the OH radicals required for the decomposition of acetaldehyde. A simple model to predict the derived cetane number of fuel blends is proposed and used to estimate the effectiveness of EHN and DTBP in improving the reactivity of ethanol. EHN works better as an additive as compared to DTBP, as it speeds up the main decomposition reactions of the fuel by providing the necessary OH radicals as compared to CH3 provided by DTBP.

Research on technological innovation and application of modern diesel engines

Diesel engines have been instrumental in driving industrial advancement. This paper provides an in-depth analysis of the evolution and application of diesel engine technology across various sectors, set against the backdrop of the global energy crisis and swift technological progress. The research emphasizes technological breakthroughs like turbocharging and common rail fuel injection, which have been pivotal in augmenting combustion efficiency and reducing environmental impact. The potential of alternative fuels, such as biodiesel, synthetic diesel, and water-emulsified diesel, in curbing emissions and bolstering combustion efficiency is also critically assessed. The diverse applications of diesel engines, spanning marine vessels to aviation, are explored, highlighting the adaptability of these engines to evolving environmental norms and market needs. The paper further investigates strategies to enhance thermal efficiency and performance, spotlighting innovative combustion methods like HCCI and RCCI. The pivotal role of accurate fuel injection control and injector design in refining combustion quality is also accentuated. In summation, while the study underscores the persistent relevance of diesel engine technology amidst modern challenges, it also advocates for sustained innovation to harmonize performance with environmental concerns. The prospective trajectory for diesel engines might encompass an amalgamation of traditional and novel energy solutions to address shifting energy and emission standards.

Experimental Analysis of Hydrogen Enrichment in Waste Plastic Oil Blends for Dual-Fuel Common Rail Direct Injection Diesel Engines

Abstract Growing global concerns about fossil fuels highlight the importance of alternative fuels for internal combustion engines. Proper management of plastic waste is crucial due to its environmental impact. The pyrolysis oil process offers a sustainable solution to address plastic waste accumulation. This study explores the impact of a hydrogen-waste plastic oil blend on a modern diesel engine. The research delves into plastic oil and diesel blends at 10%, 20%, and 30% concentrations, with hydrogen provided at 8 L/min. Experiments are conducted at various loads, and hydrogen-enriched fuel blends are analyzed for combustion characteristics, performance parameters, and emissions. Higher blended fuel ratios lead to extended ignition delays, decreased thermal efficiency, and increased emissions. Hydrogen enrichment reduces carbon dioxide, hydrocarbon, and carbon monoxide emissions but raises nitrogen oxide emissions due to higher exhaust gas temperatures. The comparative analysis shows significant improvements in brake thermal efficiency and brake-specific fuel consumption under full load conditions. The blend demonstrates notable reductions in hydrocarbon, carbon monoxide, and carbon dioxide emissions but an increase in nitrogen oxide emissions compared to diesel. The findings indicate that integrating hydrogen into diesel engines enhances performance measures and reduces overall emissions.

Evaluation of energy-exergy performance and sustainability index of a DI engine integrated with designed electromechanical EGR cooling system

Exhaust Gas Recirculation (EGR) system is a commonly used pretreatment technique to improve pollutant emissions from modern diesel engines. Recently, the EGR cooling strategy focuses on improving combustion stability, NOx emission and fuel consumption values by controlling oxygen dilution, in-cylinder and exhaust gas temperatures. However, there are not enough studies focusing on energy and exergy analysis to improve the deterioration caused by hot EGR gas in engine performance and energy distributions. Therefore, in this study, classical and electronically controlled external EGR cooling systems are designed. The present study investigates the effect of the various EGR rates and EGRout gas temperatures on classical/electromechanics EGR cooling systems in a DI diesel engine and reveals the effects of energy-exergy distributions on each other and the sustainability index (SI) perspective. The tests are performed with various EGR rates (5%, 10%, 15%) and EGRout gas temperatures (75 °C, 90 °C, 110 °C) at 1700 and 2000 rpm. At 1700 rpm test conditions, the highest thermal-exergetic efficiencies for low and high load are recorded at 15% EGR rate-75 °C EGRout gas temperature and 5% EGR rate-75 °C EGRout gas temperature, respectively. At 2000 rpm test conditions, the highest thermal-exergetic efficiencies for low and high load are achieved at 15% EGR rate-110 °C EGRout gas temperature and 5% EGR rate-90 °C EGRout gas temperature, respectively. The main findings show that the EGR rate rather than the EGRout gas temperature has a more dominant effect on the in-cylinder combustion performance and thermal-exergetic efficiency. While the increase in the EGR rate from 5% to 15% contributes positively to the thermal-exergetic efficiency and SI performance at low engine load, the opposite is observed at high load. The study recommends that the EGR rate and EGRout gas temperature should be chosen at the optimum level for the engine performance and energy efficiency.

MODERN TRENDS IN IMPROVING THE FUEL SUPPLY SYSTEM FOR VEHICLES WITH A DIESEL ENGINE

By reducing time, production and financial costs in the implementation of maintenance and repair based on the development and application of diagnostic, scientific substantiation, operational and informational methods of modern diesel engines and their fuel supply systems significantly increasing the efficiency of the operation of vehicles is an urgent scientific problem that limits the progress in the industry.

Пружинные демпферы крутильных колебаний в составе современных судовых дизелей: преимущества и недостатки

The article presents analysis of the advantages and disadvantages in assembling the spring dampers of torsional vibrations in modern marine diesel engines. There are considered the urgent problems of using spring dampers in the marine propulsion systems: lack of the systematized scientific data about the spring damper design, statistics of their prevalence in the marine diesel engines, analysis of breakdowns. It has been stated that today there is no methodology for assessing the technical condition of spring dampers, except for the methods recommended by the Russian Maritime Register of Shipping in relation to the silicone dampers. Disassembly diagnostics of the technical condition of spring dampers is extremely difficult and costly for a shipowner. Most of the vessels that are currently being operated in Russia are found obsolete, and there has started a gradual process of modernization and replacement 
 of morally and physically obsolete main engines G60,G70 (6CPH 36/45), SKL NVD, 6ChH18/22, 3D6 (6ChH 15/18) etc. by new foreign diesel engines manufactured by Wartsila (Finland), Caterpillar (USA), Volvo - Penta (Sweden), Scania (Sweden), Henan Diesel Engine Industry Co., Ltd (China) etc., which have new dampers of such companies as Geislinger (Germany), Hasse & Wrede (Germany), STE - Schwingungstechnik (Germany), Holset (England), Caterpillar (USA) etc. Diagnostics of dampers of modern diesel engines is a new direction for the domestic marine industry; it requires a revision of both the technological processes of working with such equipment and training the qualified specialists. The study of the structural and operational features of spring dampers of modern diesel engines will allow to accumulate the necessary amount of scientific and technical information to create in Russia the foundations of production of efficient structures and the development of engine building in general.

Arrhenius type empirical ignition delay equations based on the phenomenology of in-cylinder conditions for wide operating ranges in modern diesel engines

Ignition delays were systematically measured in a DI diesel engine under wide ranging and various engine operating conditions, including engine speeds, fuel injection pressures, intake gas temperatures, intake gas pressures, and intake oxygen concentrations changed with EGR. Empirical equations to predict the ignition delay based on the Arrhenius equation with and without the Livengood-Wu integral and multiple regression analysis of the experimental results. The simple equation assuming constant conditions during the ignition delay without the Livengood-Wu integral can accurately predict the ignition delay. However, the lack of generality has remained as the fuel injection pressure is directly included in the Arrhenius equation which should contain only the chemical parameters. To improve the generality of the equation, the ignition delay was separated into the initial physical process of the fuel spray breakup and the following chemical process. The start of the Livengood-Wu integral was set at the breakup time of liquid fuel jet assuming that the chemical reactions do not occur before the fuel spray breakup, and that the physical factors are directly involved in the physical processes and indirectly in the chemical processes. The fuel spray tip dynamics based on Wakuri’s momentum theory was introduced to express the changes in the conditions in the fuel spray during the ignition delay. The ignition delay can be accurately predicted by the equation with the Livengood-Wu integral and six parameters, including the breakup time, the mass flow rates of air and fuel at the cross section of the spray tip, the oxygen partial pressure, the engine speed, and the averaged in-cylinder gas temperature. The empirical equation predicted longer ignition delays at high ignition pressure conditions, and the accuracy was improved by performing a multiple regression analysis separately at each fuel injection pressure, suggesting unknown factors varying with the fuel injection pressures.

Increasing the efficiency of the lubrication system of a modern internal combustion diesel engine

BACKGROUND: Leading manufacturers of engines for trucks are constantly competing and trying to create engines with the best consumer characteristics, which at the same time meet modern environmental standards. One of the most important characteristics for long-haul tractors is fuel efficiency. As a way to improve this parameter, it was chosen to reduce the loss of mechanical energy to drive the oil pump.
 AIMS: To determine the current level of mechanical losses in the drive of the oil pump of the KAMAZ 6ChN13/15 engine, to form a set of solutions to reduce losses.
 METHODS: The current pattern of mechanical losses distribution for the 6ChN13/15 engine was obtained by engine motoring at the engine bench with sequential removal of engine components. A comparative diagram of the overpressure at the outlet of the uncontrolled and controlled pumps was obtained empirically during tests at the engine bench. The evaluation of the positive effect from the use of a controlled oil pump was determined analytically.
 RESULTS: As a result, by using a controlled oil pump, it became possible to reduce the excess pressure at the outlet of the pump at nominal rotational speed by 25%, which theoretically should reduce the relative mechanical losses of the engine by 3%.
 CONCLUSIONS: The practical value of the study lies in determining effective ways to reduce mechanical energy losses and improve the consumer qualities of modern diesel engines.

Ranking of four dual loop EGR modes

Modern Diesel engines contain sophisticated control systems to keep their environmental impact low for sustainable road transport. One of these systems is the dual loop exhaust gas recirculation, which can change combustion properties in several ways. This article presents an engine dyno measurement based on analyzing the duel loop EGR with a medium-duty Diesel engine. Intake throttles and exhaust brakes for the highest freedom in the air-fuel ratio setting support the EGR systems. The EGR modes are compared from fuel consumption, NOx emission, and exhaust gas opacity in steady and transient operations. There are expected results, for instance, in the HP EGR’s faster reaction time or the LP EGR’s boost pressure holding property. Unexpected results are also presented. Contrary to theory, LP EGR generally provides a fuel consumption advantage in many operation points due to its higher boost pressure. Typically, HP EGR can provide lower fuel consumption at higher engine power. In the emission results, LP EGR is favourable both in NOx emission and exhaust gas opacity, whereas the intake throttle-supported HP EGR usually shows the highest emission. Besides, with high EGR rates at lower engine loads, LP EGR can realize low-temperature combustion, where both emissions decrease. No difference can be detected between the LP EGR’s support valves’ results. HP EGR was faster in the transient operation, with about half the reaction time. The results can be utilized for dual-loop EGR layout and control design.

Study on the Design Stage from a Dimensional and Energetic Point of View for a Marine Technical Water Generator Suitable for a Medium Size Container Ship

The purpose of this study is to provide an overview of the development of the modern low-speed marine two-stroke diesel engine from the point of view of the technical water cooling plant, taking into account and starting from the market requirements for power and speed, with information and design options relevant to the entire shipping industry. Thus, through the ideas of this project, we analyze notions and relevant aspects of systems related to marine slow turning engines, including the basic thermodynamic structure of the technical water system designed for a marine engine. This study also presents the design criteria that define the size and design concept of the engine structure components, with a focus on the technical water cooling installation. The concepts for the main engine hot parts served by the technical water cooling installation play a vital role in the marine technical water generator. The choices the engine designer must make regarding basic auxiliary systems, such as fuel injection and exhaust valve actuation, are important factors to keep in mind when installing a technical water generator onboard a ship. The automation and control systems that govern the modern electronic engine, which drive the supply pump of the technical water cooling system can provide a simplified view of the engine development process. In order to point out the contributions of this study, it is important to focus on the calculations used to determine the main parameters of a technical water generator especially designed for a midsized container ship.

Experimental investigation of combustion characteristics analysis and optimization during the turbocharging mode switching process of diesel engine with advanced turbocharging system

Multi-turbocharger system is one of the major enablers of modern diesel engine performance. To meet the boosting requirements under different operating conditions is the difficulty. The two-stage sequential turbocharging (TSST) system creates the flexibility to select the turbocharging mode so that the engine benefits from efficiency and power density. However, the critical issue at hand is the unstable running, or even worse, misfire, of the engine caused by the abrupt air path shifts during the turbocharging mode switching process. Therefore, the control of the switching process is an indispensable procedure to apply the TSST system. The previous studies mainly focused on turbocharging system parameters. The combustion characteristics during switching process have been underestimated. The combustion process is influenced by the fuel and charging variations during the transient process, and it is unique compared with the steady state. In this paper, the experiments of TSST system switching process were carried out to investigate the transient combustion characteristics, formation mechanism of its fluctuation, and optimal control. The experimental results indicate that the combustion present fluctuation during the direct switching process. The main features are the generation and extinction of premixed combustion, combining the degradation and recovery of mixing-controlled combustion. The cycle history of heat-release center (CA50) presents a 3-phase fluctuation of moving backward from 9.7°CA to11.2°CA, then forward to 6.2°CA, and finally backward to 10.7°CA. The boost pressure trough is the primary factor contributing to incomplete combustion. The lowest gross indicated efficiency of 33.9 % happened at the lowest air-fuel ratio cycle. Based on the corresponding results, the substantial improvement in combustion can be ensured by regulating the switch valves in air path. When the intake switch valve opens 0.9 s later than the exhaust switch valve, the system exhibits minimal parameter fluctuations and the quickest recovery capacity. The coefficients of variation for IMEPg and CA50 are 2.7 % and 4.6 %, respectively, guaranteeing at least 39.7 % fuel conversion efficiency and only 17 cycles to reach the steady state.

The experimental study of mechanical losses in the modern diesel engine

BACKGROUND: Amid the tightening of the CO2 emission requirements as well as high level of competition on the commercial truck market, the focus area of the internal combustion engine (ICE) development is as follows: high engine efficiency and fuel economy, minimization of internal losses and engine cycle optimization for all operation modes. Engine performance factors of modern 1213-liter diesel engines, existing on the global market, are as follows: the minimal specific fuel consumption is 179182 g/kWh, effective efficiency is 4648%. Decreasing of mechanical losses is one of the features that made the achievement of such factors possible. The relevant issue for choosing the strategy of mechanical losses decreasing is formation of balance in losses distribution between main ICE groups of components. Moreover, considering the mechanical losses dependence on engine operating speed, engine cycle parameters and engine design features, it is important to determine the pattern of change in mechanical losses.
 AIMS: Assessment of mechanical losses of modern diesel engine with high effective efficiency in an experimental way. Formation of mechanical losses balance.
 METHODS: The study object is the 6ChN 13/15 inline six-cylinder diesel engine with the operation volume of 11.95 liters. The mechanical losses assessment was performed with the engine, propelled by a dynamometric machine on a testing facility with fully stabilized conditions, with the method of sequential disassemble of main groups of components.
 RESULTS: Relevant data of mechanical losses level of the modern diesel engine with the distribution between main groups of components is obtained. Mechanical losses dependence on operation speed, oil and coolant liquid temperatures is formed.
 CONCLUSIONS: Practical value of the study lies in assessment of contribution of each group of components in the total friction as well as in assessment of the degree of design and technological development of ICEs. According to the study results, areas of possible improvement of friction for each group of components and engine as a whole will be formed.

An indirect approach to optimize the reaction rates of thermal NO formation for diesel engines

With stringent emission regulations, it has become more important for modern diesel engine manufacturers to accurately predict engine-out nitrogen oxide (NOx) emissions across a wide range of operating conditions. Thermal NO is the major source of engine-out NOx in modern diesel engines. For thermal NO formation, several earlier studies have recommended the forward and reverse reaction rate coefficients of the rate-limiting reaction (O + N2⇌ NO + N). However, due to deficiencies in sub-models and inadequacies of reduced chemical mechanisms to represent diesel combustion, these recommended values more often than not need to be adjusted in reduced order combustion models to accurately predict engine-out NOx. Hence, in this work a systematic and computationally efficient approach has been proposed to streamline the process of determining the optimum reaction rate coefficients. To develop the optimization approach, four different production diesel engines with different operating conditions in terms of speed, load, and exhaust-gas recirculation have been considered. Numerical simulations have been performed using a detailed zero-dimensional velocity-composition-frequency transported probability density function (0D-VCF-tPDF) model that uses hundreds of notional particles to capture in-cylinder stratification. Four different combinations of hydrocarbon and NOx chemical mechanisms were used to represent chemistry. It was found that for the rate-limiting reaction, the pre-exponent factors (Af1,Ar1) and activation energies (EA,f1,EA,r1) of the forward and reverse reaction rates follow a linear band in Af1−EA,f1 and Ar1−EA,r1 space where predicted engine-out NOx match the measured values closely. By encompassing such bands from different engines and considering constraints on activation energies, a reduced search domain of pre-exponent factors and activation energies was constructed that is expected to be applicable to any diesel engine. Eventually, computationally efficient three-line and one-line search approaches were proposed to determine the optimum values of the pre-exponent factors and activation energies that led to a minimum error between measured and predicted engine-out NOx. Finally, these three-line and one-line NOx optimization approaches were applied to a fifth production diesel engine for which the 0D-VCF-tPDF model showed a very good predictive performance in terms of predicting peak pressure, 50% burn rate, and engine-out NOx when compared to measured and 3D-CFD values.