Conventional Combustion Research Articles

The Impact of Fuel Injection Timing and Charge Dilution Rate on Low Temperature Combustion in a Compression Ignition Engine

Using high charge dilution low temperature combustion (LTC) strategies in a diesel engine offers low emissions of nitrogen oxides (NOx). These strategies are limited to part-load conditions and involve high levels of charge dilution, typically achieved through the use of recirculated exhaust gases (EGR). The slow response of the gas handling system, compared to load demand and fuelling, can lead to conditions where dilution levels are higher or lower than expected, impacting emissions and combustion stability. This article reports on the sensitivity of high-dilution LTC to variations in EGR rate and fuel injection timing. Impacts on engine efficiency, combustion stability and emissions are assessed in a single-cylinder engine and compared to in-cylinder flame temperatures measured using a borescope-based two-colour pyrometer. The work focuses on low-load conditions (300 kPa gross indicated mean effective pressure) and includes an EGR sweep from conventional diesel mode to high-dilution LTC, and sensitivity studies investigating the effects of variations in charge dilution and fuel injection timing at the high-dilution LTC condition. Key findings from the study include that the peak flame temperature decreased from ~2580 K in conventional diesel combustion with no EGR to 1800 K in LTC with low-NOx, low-soot operation and an EGR rate of 57%. Increasing the EGR to 64% reduced flame temperatures to 1400 K but increased total hydrocarbon (THC) and carbon monoxide (CO) emissions by 30–50% and increased fuel consumption by 5–7%. Charge dilution was found to have a stronger effect on the combustion process than the diesel injection timing under these LTC conditions. Advancing fuel injection timings at increasing dilution kept combustion instability below 2.5%. Peak in-cylinder temperatures were maintained in the 2000–2100 K range, while THC and CO emissions were controlled by delaying the onset of bulk quenching. Very early injection (earlier than 24 °CA before top-dead-centre) resulted in spray impingement on the piston crown, resulting in degraded efficiency and higher emissions. The results of this study demonstrate the potential of fuel injection timing modification to accommodate variations in charge dilution rates while maintaining low NOx and PM emissions in a diesel engine using low-temperature combustion strategies at part loads.

Novel Energy Management Control Strategy for Improving Efficiency in Hybrid Powertrains

Energy management in electrified vehicles is critical and directly impacts the global operating efficiency, durability, driveability, and safety of the vehicle powertrain. Given the multitude of components of these powertrains, the complexity of the proper control is significantly higher than the conventional internal combustion engine vehicle (ICEV). Hence, several control algorithms and numerical methods have been developed and implemented in order to optimize the operation of the hybrid powertrain while complying with the required boundary conditions. In this work, a model-based method is used for predicting the impacts of a set of possible control actions, choosing the one minimizing the associated costs. In particular, the energy management technique used in the present study is the equivalent consumption minimization strategy (ECMS). The novelty of this work consists of taking into account the thermal state of the ICE for optimization. This feature was implemented by means of an extensive experimental campaign at different coolant temperatures of the ICE to calibrate the additional fuel consumption due to operating the engine outside of its optimum temperature. The results showed significant gains in both WLTC and RDE cycles.

Renewable Power and Heat for the Decarbonisation of Energy-Intensive Industries

The present review provides a catalogue of relevant renewable energy (RE) technologies currently available (regarding the 2030 scope) and to be available in the transition towards 2050 for the decarbonisation of Energy Intensive Industries (EIIs). RE solutions have been classified into technologies based on the use of renewable electricity and those used to produce heat for multiple industrial processes. Electrification will be key thanks to the gradual decrease in renewable power prices and the conversion of natural-gas-dependent processes. Industrial processes that are not eligible for electrification will still need a form of renewable heat. Among them, the following have been identified: concentrating solar power, heat pumps, and geothermal energy. These can supply a broad range of needed temperatures. Biomass will be a key element not only in the decarbonisation of conventional combustion systems but also as a biofuel feedstock. Biomethane and green hydrogen are considered essential. Biomethane can allow a straightforward transition from fossil-based natural gas to renewable gas. Green hydrogen production technologies will be required to increase their maturity and availability in Europe (EU). EIIs’ decarbonisation will occur through the progressive use of an energy mix that allows EU industrial sectors to remain competitive on a global scale. Each industrial sector will require specific renewable energy solutions, especially the top greenhouse gas-emitting industries. This analysis has also been conceived as a starting point for discussions with potential decision makers to facilitate a more rapid transition of EIIs to full decarbonisation.

Influence of primary reference fuels on isobaric combustion in a heavy-duty optical diesel engine

Previous studies on isobaric combustion achieved using n-heptane/diesel fuel have shown the potential for higher engine efficiency compared to conventional diesel combustion. This was due to the lower heat transfer losses thanks to the lower rate of heat release and in-cylinder temperature, along with exhaust losses when coupled with a split cycle concept. However, the close-coupled injections implemented in isobaric combustion led to spray-flame interactions resulting in higher soot emissions. Potential ways to reduce the soot emissions are either employing multiple injectors, which helps to avoid the spray-flame interaction, or, as investigated in this study, burning higher octane or low reactivity fuels to increase the pre-combustion mixing time. This study investigated the effect of fuels on isobaric combustion in both all-metal and optical configurations of a heavy-duty optical diesel engine. Isobaric combustion was achieved using multiple injections from a single central injector; the engine performance, exhaust emissions, particle size distributions, and in-cylinder flame and soot distributions have been compared for three different primary reference fuels (PRFs) i.e., PRF0 (n-heptane), PRF50 (volumetric mixture of 50 % n-heptane and 50 % isooctane), and PRF100 (isooctane). High-speed combustion luminosity, OH* chemiluminescence, and planar laser-induced incandescence of soot (soot-PLII) have been performed at a fixed air-excess ratio and peak cylinder pressure for all three fuels. The results demonstrated that PRF100 being the least reactive fuel out of the three tested fuels led to longer ignition delay resulting in more premixed combustion. PRF100 resulted in 4 % higher gross indicated efficiency, 48.8 % lower heat transfer losses, 17.6 % lower exhaust losses, and 87.4 % lower soot emission than PRF0; however, isobaric combustion using PRF100 was difficult to achieve. PRF50 is a promising candidate for isobaric combustion with slightly lower gross indicated efficiency than PRF100 but lower uHC/CO/soot/NOx emissions. Overall, PDI of Soot-PLII indicates initial soot is formed near the nozzle holes, and grow along the flame direction, until they hit the bowl-wall and flow along it due to flame-wall interactions. The soot PDI values are comparatively lower as we move axially away from the top of the cylinder.

Optimization of homogeneous charge compression ignition combustion in a light-duty diesel engine operated using ethyl acetate-gasoline blends

The low temperature combustion mode of homogeneous charge compression ignition eliminates particulate matter and oxides of nitrogen (NO x) emissions trade-off that prevails in high-temperature, diffusion-controlled conventional diesel combustion (CDC). In the present research, the significant challenge of narrow operating load range that hinders the commercial implementation of light-duty HCCI engines was overcome by employing ethyl acetate-gasoline blends. The gasoline concentration in test fuels was reduced in 10% decrements, from 84% to 24%, to replace it with ethyl acetate. The use of ethyl acetate, a renewable fuel, can help solve the energy crisis due to the rapid depletion of fossil fuels. An ignition improver was blended in the test fuels in a predetermined amount of 6% so that combustion stability was not hampered at lower loads. Parametric investigations were conducted to study the effect of progressively increasing ethyl acetate in test fuels on HCCI combustion, performance, and emissions. The machine learning tool of artificial neural network was implemented to learn the behavior of the test engine, considering load and fuel composition as input variables. The feedforward artificial neural network models were developed to predict the start of combustion, combustion phasing, indicated thermal efficiency, and emissions of carbon monoxide, soot, NO x, and unburned hydrocarbon (HC). A multi-objective optimization was performed to arrive at the best operating condition by integrating artificial neural network models with the genetic algorithm. All the developed artificial neural network models could predict responses with acceptable accuracy. The genetic algorithm indicated that the optimum point of the operation was at 80% load and 65% ethyl acetate in the test fuels. Experiments were conducted to validate the optimal HCCI conditions that resulted in 27% higher indicated thermal efficiency, 54% lower HC+NOx, and 99% lower soot emissions than CDC. Overall, the present study demonstrated the benefits of considering ethyl acetate as a fuel to improve HCCI engine metrics of off-road diesel engines.

Liquefaction, cracking and hydrogenation of microalgae biomass resources to CO2 negative advanced biofuels: Mechanisms, reaction microkinetics and modelling

Deoxygenation of triglycerides is one of the crucial pathways for the production of oxygen-free hydrocarbons and biofuels that are fully compatible with conventional internal combustion engines. The one-step liquefaction and hydrotreatment of Chlorella sorokiniana microalgae was investigated in a three-phase slurry reactor. The production of diesel-like hydrocarbons was successfully accomplished over sulfide form of NiMo/Al2O3 catalyst under hydrogen atmosphere. The present work contains a comprehensive investigation of the temperature and hydrogen pressure influence on the final product composition. The highest yield of C18 and C16 (26.1% and 10.7%, respectively) was reached by increasing the reaction temperature to 350 °C and hydrogen pressure to 50 bar, while at milder conditions (200 °C and 20 bar) the products appeared only in trace concentrations. In order to obtain an accurate kinetic model, reaction mechanism was first needed to be determined based on experimentally obtained products and intermediates. A simplified reaction pathway contains liquefaction, hydrogenolysis, hydrodeoxygenation, decarboxylation and decarbonylation. The model comprises mass transfer phenomena involved in the liquefaction process, the mass transfer of hydrogen from gas to liquid phase, adsorption, desorption and surface reaction kinetics. The lowest rate constant was calculated for the microalgae conversion to triglycerides (k0 = 1.93 × 10−6 min−1), indicating slow liquefaction.

Dynamic stabilization of a hydrogen premixed flame in a narrow channel

Combustion of hydrogen can help in reducing carbon-based emissions but it also poses unique challenges related to the high flame speed and Lewis number effects of the hydrogen flame. When operated with conventional burners, a hydrogen flame can flashback at higher volumetric flow rates than a methane flame due to the difference in stabilization mechanisms of the two fuels. Due to these differences, conventional burners cannot offer similar operational ranges for hydrogen than that for hydrocarbon flames. An exploration into the unique stabilization behaviour of hydrogen flames is required which could help in envisioning non-conventional burner concepts for keeping hydrogen flames stable. Stability conditions, which describe the kinematics of premixed flames with spatially and temporally changing flow parameters, are crucial for such an exploration. Stability conditions are usually hypothesized for stable flames, where a flame upon perturbation is assumed to return to its original position. Alternatively, in the case of flashback/blow-off, it refers to a flame moving upstream of the burner or being convected out of the domain. However, it is also of interest to understand how and why a flame could move to a new location when the velocity and strain fields are varying with time and space at the original and the new location. In this paper, we investigate the flame stabilization by 1) observing the hydrogen flame’s upstream movement in a multi-slit configuration when a geometrical change is made, and 2) changing strain and velocity fields in a dynamic and periodic manner using numerical tools such that the unique behaviour of a hydrogen flame can be captured. We vary the location of high flow strain periodically in a channel by manipulating the boundary condition along a wall. It is found that a hydrogen flame follows this point in a periodic manner, also propagating against the inflow which is considerably faster than its unstretched burning velocity. Spatial and temporal stability conditions, that explain the mechanism behind the flame’s movement from its original position to a new position, are analyzed from the simulation data, advancing our knowledge on the flame movement in an unsteady setting and providing important insights into the stabilization mechanism of hydrogen flames.

The Influence of Design Geometry on the Operational Performance of Helmholtz Pulse Combustor

The objective of this study is to build a pulse combustion simulation model in order to determine the design parameters that influence the pulse combustor’s optimized performance. The Helmholtz valveless pulse combustor type is the simple design of pulse combustors. It has many advantages over conventional combustion, so it has been used in a variety of applications. There are many parameters that need to be studied in order to design this combustor type to achieve optimal performance. This research presents numerical and experimental investigations of pulse combustion. FLUENT software is used to conduct numerical simulations of the design parameters and pulse combustor performance. These simulations are then experimentally validated and confirmed to be accurately optimized in order to be applicable. The performance of the pulse combustor is studied for different inlet and tailpipe length and combustion chamber volume. This research accurately predicts how the frequency and pressure amplitude vary as the lengths of the inlet and tailpipe increase, as well as the combustion chamber volume.

Progress in high-resolution isotope-ratio analysis of tree rings using laser ablation.

Stable isotope ratio analysis of tree rings has been widely and successfully applied in recent decades for climatic and environmental reconstructions. These studies were mostly conducted at an annual resolution, considering one measurement per tree ring, often focusing on latewood. However, much more information could be retrieved with high-resolution intra-annual isotope studies, based on the fact that the wood cells and the corresponding organic matter are continuously laid down during the growing season. Such studies are still relatively rare, but have a unique potential for reconstructing seasonal climate variations or short-term changes in physiological plant properties, like water-use efficiency. The reason for this research gap is mostly technical, as on the one hand sub-annual, manual splitting of rings is very tedious, while on the other hand automated laser ablation for high-resolution analyses is not yet well established and available. Here, we give an update on the current status of laser ablation research for analysis of the carbon isotope ratio (δ13C) of wood, describe an easy-to-use laser ablation system, its operation and discuss practical issues related to tree core preparation, including cellulose extraction. The results show that routine analysis with up to 100 laser shot-derived δ13C-values daily and good precision and accuracy (ca. 0.1‰) comparable to conventional combustion in an elemental analyzer are possible. Measurements on resin-extracted wood is recommended as most efficient, but laser ablation is also possible on cellulose extracted wood pieces. Considering the straightforward sample preparation, the technique is therefore ripe for wide-spread application. With this work, we hope to stimulate future progress in the promising field of high-resolution environmental reconstruction using laser ablation.

A single fuel port and direct injected low temperature combustion strategy to reduce regulated pollutants from a light-duty diesel engine

Low temperature combustion (LTC) recently received considerable attention due to its potential to simultaneously reduce oxides of nitrogen (NOx) and soot emissions from diesel engines and high thermal efficiency benefits. However, lack of ignition timing control, narrow engine operating load range, high unburned hydrocarbon (UHC), and carbon monoxide (CO) emissions are significant shortcomings in LTC. A homogeneous charge with direct injection (HCDI) strategy is proposed in this study to address these shortcomings. HCDI is a single-fuel LTC strategy that includes port and direct diesel fuel injection. The direct-injected diesel provides better control over ignition timing, and a wider engine operating load range could be achieved in HCDI. However, NOx emissions are significantly higher in HCDI than conventional diesel combustion (CDC). A novel water vapour induction system using ultrasonic atomizers is proposed to address this shortcoming. The experiments were conducted in a modified single-cylinder light-duty diesel engine operated in HCDI mode. A high-pressure port and direct fuel injection systems are installed in the metallic engine (engine with factory configuration) to achieve HCDI. Ultrasonic atomizers installed closer to the intake port generated the water vapour for NOx control. The premixed ratio and direct-injected diesel fuel timings are optimized to achieve maximum thermal efficiency at each load condition. The results obtained with and without water vapour induction in HCDI are compared to examine the NOx reduction potential. Further, the results obtained in HCDI with water vapour induction are compared with CDC with production settings to examine engine performance improvement and emission reduction. The results show improved thermal efficiency with reduced NOx emissions with water vapour induction in HCDI. HCDI resulted in higher thermal efficiency than CDC, with a maximum increase of 20.3 % and a 27.1 % reduction in NOx emissions at 3.5 bar IMEP. However, at a higher load condition of 5.7 bar IMEP, the thermal efficiency is reduced with higher soot emissions in HCDI. Direct-injected fuel pressure was increased, and injection timings were optimized to address this shortcoming. The soot emissions were reduced by 89.2 %, with a slight increase in thermal efficiency. The unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions were reduced significantly in HCDI compared to CDC, with a maximum reduction of 95.9 % and 40.7 %, respectively. Overall, the proposed novel HCDI with water vapour induction is a promising LTC strategy for diesel engines that helps achieve a wider operating load range, higher thermal efficiency and lower regulated pollutants.

Comparative Analysis of Grid Connected Electric Vehicle

Growing need of transportation is pushing scientists towards the better option other than conventional internal combustion engines. One of the most effective ways to reduce the effects of these IC engines is the use of electric vehicle. This paper consists of a comprehensive overview on integration of electric vehicles to the grid. Vehicle to grid (V2G) technology and its effects on the grid have been depicted along with the challenges faced during the process. ULTRA, FAST, ECO and V2G modes in which the vehicles can be connected to the grid and importance of each mode in their aspects are also discussed here. All the modes combined cover the entire population’s demand regarding the charging system which is the major area of research for energy management domain.

A Comparison between Statistical Behaviours of Scalar Dissipation Rate between Homogeneous MILD Combustion and Premixed Turbulent Flames

Three-dimensional Direct Numerical Simulations (DNS) data has been utilised to analyse statistical behaviours of the scalar dissipation rate (SDR) and its transport for homogeneous methane-air mixture turbulent Moderate or Intense Low oxygen Dilution (MILD) combustion for different O2 dilution levels and turbulence intensities for different reaction progress variable definitions. Additional DNS has been conducted for turbulent premixed flames and passive scalar mixing for the purpose of comparison with the SDR statistics of the homogeneous mixture MILD combustion with that in conventional premixed combustion and passive scalar mixing. It has been found that the peak mean value of the scalar dissipation rate decreases with decreasing O2 concentration for MILD combustion cases. Moreover, SDR magnitudes increase with increasing turbulence intensity for both MILD and conventional premixed combustion cases. The profiles and mean values of the scalar dissipation rate conditioned upon the reaction progress variable are found to be sensitive to the choice of the reaction progress variable definition. This behaviour arises due to the differences in the distributions of the species mass fractions within the flame. The strain rate contribution and the molecular dissipation term are found to be the leading order contributors in the scalar dissipation rate transport for MILD combustion; whereas, in conventional premixed flames, the terms rising from density variation and reaction rate gradient also play leading roles in addition to the strain rate and molecular dissipation contributions. By contrast, the terms due to density gradient and reaction rate gradient remain negligible in comparison to the leading order contributors in MILD combustion cases due to small density variation because of moderate temperature rise and small reaction rate gradient magnitudes. Furthermore, the qualitative behaviour of the strain rate contribution to the SDR transport in premixed flames is significantly different to that in the case of MILD combustion and passive scalar mixing. The findings of the current analysis indicate that the scalar dissipation rate statistics in MILD combustion show several qualitative similarities to the passive scalar mixing despite major differences with the SDR transport in conventional turbulent premixed flames. This further suggests that the scalar dissipation rate models, which were originally proposed in the context of passive scalar mixing, have the potential to be applicable for MILD combustion but the models for the premixed turbulent combustion may not be applicable for MILD combustion of homogeneous mixtures.

Accelerometer-based SOC estimation methodology for combustion control applied to Gasoline Compression Ignition

The European Community’s recent decision to suspend the marketing of cars with conventional fossil-fueled internal combustion engines from 2035 requires new solutions, based on carbon-neutral technologies, that ensure equivalent performances in terms of reliability, trip autonomy, refueling times and end-of-life disposal of components compared to those of current gasoline or diesel cars. The use of bio-fuels and hydrogen, which can be obtained by renewable energy sources, coupled with high-efficiency combustion methodologies might allow to reach the carbon neutrality of transports (net-zero carbon dioxide emissions) even using the well-known internal combustion engine technology. Bearing this in mind, experiments were carried out on compression ignited engines running on gasoline (GCI) with a high thermal efficiency which, in the future, could be easily adapted to run on a bio-fuel. Despite the well-reported benefits of GCI engines in terms of efficiency and pollutant emissions, combustion instability hinders the diffusion of these engines for industrial applications. A possible solution to stabilize GCI combustion is the use of multiple injections strategies, typically composed by 2 early injected fuel jests followed by the main injection. The heat released by the combustion of the earlier fuel jets allows to reduce the ignition delay of the main injection, directly affecting both delivered torque and center of combustion. As a result, to properly manage GCI engines, a stable and reliable combustion of the pre-injections is mandatory. In this paper, an estimation methodology of the start of combustion (SOC) position, based on the analysis of the signal coming from an accelerometer sensor mounted on the engine block, is presented (the optimal sensor positioning is also discussed). A strong correlation between the SOC calculated from the accelerometer and that obtained from the analysis of the rate of heat release (RoHR) was identified. As a result, the estimated SOC could be used to feedback an adaptive closed-loop combustion control algorithm, suitable to improve the stability of the whole combustion process.

European Green Deal Implications on Country Level Energy Consumption

Abstract Research background: The European Green deal set by the European Commission has launched new business models in sustainable development. Major contributions are expected in the road transport sector; as far as conventional internal combustion creates significant input in Green House Gas emission inventories. Each EU member state has an obligation to reduce GhG emission by accelerating Electric Vehicle development. In order to foster growth of EVs, there is the need of significant investment into charging infrastructures. The article propose the model of forecasting of investment based on the forecast of the growth of the amount of electric vehicles and their demand on energy. The model includes the behaviouristic approach based on the total cost of ownership model as well as calculations of efficient usage of EV charging points. The model takes into account all types of vehicles including personal and commercial, freight and passenger. Purpose: The aim of this article is to present a complex model for forecasting the required investments based on the fore-cast of the increase in the number of electric vehicles and their demand on energy and investments. Research methodology: The general algorithm of forecasting consists of several consecutive phases: (1) Forecasting the number of electric vehicles, (2) Forecasting the energy needed for electric vehicles, based on the forecast (1) and the predicted usage level of these vehicles. (3) Forecasting the charging station number with the expected technical capacities and characteristics of these charging stations based on the forecasts (1) and (2). (4) Forecasting the need to upgrade the low-voltage grid based on the forecast (3). (5) Calculating the total investment needed based on the results of the forecasts (3) and (4). The main limitations of the study are related to the statistics available for modelling and human behaviour uncertainty, especially in the evaluation impact of measures to foster use of electric vehicles. Results: The findings of the Lithuanian case analysis, which is expressed in three scenarios, focuses on two trends. The most promising scenario projects 319,470 electric vehicles by 2030 which will demand for 1.09 TWh of electricity, representing 8.4–9.9 percent of the total energy consumption in the country. It requires EUR 230, million in the low-voltage grid and EUR 209, million in the charging stations. Novelty: The scientific problem is that the current approach on the forecasting of electric vehicles is too abstract, forecast models cannot be transferred from country to country. This article proposes a model of forecasting investments based on the forecast of the increase in the number of electric vehicles and their demand on energy. The model includes the behaviouristic approach based on the total cost of ownership model as well as calculations of efficient usage of EV charging points. The model takes into account all types of vehicles including personal and commercial, freight and passenger. The article has proven that statistics-based forecasting gives very different results compared to the objective function and to the evaluation of the effects of measures. This has not been compared in previous studies.

ANALYSIS OF ADVANCED TECHNOLOGY FOR COMBUSTION OF HOMOGENEOUS FUEL MIXTURE

The most serious problems to overcome for a successful operation of the HCCI engine are control of the combustion phase, limited operational range, cold start of engine and high noise level during engine operation. This study aims at describing the engine power output characteristics and emission characteristics of HCCI engines under different testing conditions and the various challenges associated with these engines. Furthermore, this study holds a potential guide for overcoming these challenges and improvement of the engine power output as well as the emission characteristics. Thus, it is possible to say, concerning the performed investigation work, that HCCI combustion can be applied in existing conventional engines after their modifications. The most significant result of the HCCI process application is the reduction of NOx emissions and soot emissions, keeping almost the same engine power output as the conventional combustion process.

A conceptual framework for waste heat recovery from compression ignition engines: Technologies, working fluids & heat exchangers

• The current article reviews the potentials of waste heat recovery systems in diesel engines. • The study highlights the importance of working fluids and their performance in waste heat recovery systems. • This research work reviews the importance of heat exchanger design and the choice of waste heat recovery systems. In recent years, the awareness about sustainable energy production using renewable energy sources has increased drastically due to the depletion of fossil fuels and the implementation of environmental protection measures. The effective energy conversion rate of conventional combustion engines stands at 35% whereas the rest of the energy gets dissipated as waste heat to cool the engine. Several Waste Heat Recovery (WHR) methods have been developed so far such as the Organic Rankine Cycle (ORC), thermoelectric generator (TEG), Stirling engine (SE) and the Electric turbo-compounding (ETC). Various research works have been conducted so far to enhance the efficiency of combustion engines through innovative heat recovery systems and by reducing the energy losses, especially in automotive applications. The novelty of the current review article lies in analyzing different aspects of the WHR technologies in terms of increasing the fuel economy and environmental compliance in diesel engines from the perspectives of technology and application feasibility. Further, the current study is also an initiative to present a comprehensive review of different criteria regarding working fluid selection, heat exchanger parameters and their optimization. The results of this article infer that waste heat can be used in an attractive way to produce additional power efficiently, which in turn can result in maximum overall efficiency and optimal usage of the waste energy through the implementation of an exhaust heat recovery system. The current study also recommends that the fuel economy of compression ignition engines can be significantly improved by paying special attention to innovative heat exchanger designs, different parameters of the heat exchangers and working fluid selection.

Experimental optimization of homogeneous charge compression ignition through fuel modifications and a relative comparison with reactivity controlled compression ignition

Reactivity controlled compression ignition (RCCI) and homogeneous charge compression ignition (HCCI) are suitable alternatives to improve the performance and emission metrics of conventional diesel combustion. Previous studies have shown that the gasoline/diesel RCCI outperforms diesel HCCI as it has a wider load range, higher brake thermal efficiency, and lower smoke and oxides of nitrogen emissions. The present work addressed the shortcomings of diesel HCCI by replacing diesel with low reactivity, high volatile methanol–gasoline blends. 2-ethylhexyl nitrate, an ignition quality improver, was added in small amounts (6 vol.%) to the blends to avoid misfiring, particularly at lower loads. There were two approaches to improve engine performance metrics of methanol–gasoline HCCI: exhaust gas recirculation and fuel composition variation. The best approach was chosen, and HCCI performed using the selected approach was compared with baseline RCCI. The methanol-gasoline HCCI was compared to baseline-optimized gasoline/diesel RCCI to demonstrate that the challenges associated with diesel HCCI can be overcome through fuel modifications. It was revealed that the strategy of varying methanol concentration in fuel blends was more effective than the strategy of varying EGR rate in terms of efficiency improvement and reduction of soot, carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions. The parametric investigation showed that HCCI outperformed RCCI at mid to higher loads. For instance: at 60% load (3.19 BMEP), indicated thermal efficiency decreased by 7%, specific CO, UHC, nitrogen oxides, and smoke emissions elevated by 1.3, 1.2, 2.5, and 20.5 times for baseline-optimized RCCI than 40% methanol/54% gasoline/6% 2-EHN HCCI. Also, increased methanol in fuel during HCCI improved indicated thermal efficiency at a particular load. For instance, at 60% load, the indicated thermal efficiency improved by 30% during HCCI of fuel containing 40% methanol than 20% methanol. Overall, the present work discusses a practical method to efficiently use renewable methanol fuel in HCCI engines.

Hydrogen Internal Combustion Engine Vehicles: A Review

Motor vehicles are the backbone of global transport. In recent years, due to the rising costs of fossil fuels and increasing concerns about their negative impact on the natural environment, the development of low-emission power supply systems for vehicles has been observed. In order to create a stable and safe global transport system, an important issue seems to be the diversification of propulsion systems for vehicles, which can be achieved through the simultaneous development of conventional internal combustion vehicles, electric vehicles (both battery and fuel cell powered) as well as combustion hydrogen-powered vehicles. This publication presents an overview of commercial vehicles (available on the market) powered by internal combustion hydrogen engines. The work focuses on presenting the development of technology from the point of view of introducing ready-made hydrogen-powered vehicles to the market or technical solutions enabling the use of hydrogen mixtures in internal combustion engines. The study covers the history of the technology, dedicated hydrogen and bi-fuel vehicles, and vehicles with an engine powered by a mixture of conventional fuels and hydrogen. It presents basic technology parameters and solutions introduced by leading vehicle manufacturers in the vehicle market.

Evaluation of the sample size requirements of machine learning models used in engine design and research

Machine Learning (ML) techniques have been effectively used to learn the intricate relationships between variables that play a significant role in the field of engine design. However, there are two challenges to this approach – (1) Identifying ML regression models that could capture the trends of a response variable, given a non-parametric training set of relatively small size, with an acceptable accuracy and response time, and (2) identifying the size of the dataset, with respect to the input parameters, to be used for training and validation of the ML models. There is not enough information in the literature to reach a consensus on the sampling size to be used for an engine design problem that would yield an acceptable measure of goodness-of-fit. This is evident from the varied size of the training/validation data size used within the engine research community, as will be elaborated on in the following sections. The objective of this paper is to provide an insight into the sampling size required by the different ML models to achieve an acceptable fit between the model and the data, to be used in three types of engine design/optimization problems – (1) conventional diesel combustion (CDC) engine performance over a wide range of speed and load, (2) cold-start operation of a direct-injected spark-ignition (DISI) engine, and (3) high-load performance of a dual-fuel reactivity-controlled compression ignition (RCCI) engine.

Mechanical properties evaluation and microstructural analysis study of ceramic-coated IC engine cylinder liner

In the automotive industry, the primary objectives are to bring down the fuel consumption and boost power. The diesel engine has the best performance of any conventional internal combustion engine because of its extraordinarily high compression ratio. Gasoline engines consume more fuel per unit of power than diesel ones, whilst the two have the same performance. Only 40% of the power generated by an engine is utilized for productive purposes on average. Thirty percent of the remaining heat is lost through the exhaust, and another thirty percent is dissipated as heat losses by the cooling system. Ceramic and YSZ Coatings are applied to the cylinder liners and the piston head to transform the heat generated by the combustion process into meaningful mechanical work. As a result, the engine's heat transmission will be reduced, increasing efficiency. The higher gas temperature is expected to minimize the concentration of incomplete combustion products at the expense of an increase in nitrogen oxides (NOx). Scanning Electron Microscopy (SEM) and optical microscopy studied an engine cylinder liner's top-ring reversal point surface texture. Experiments were done on a single spark ignition engine during the break-in stage and the texture of the cylinder liner is studied.