Search

The article presents the results of studies of energy, environmental and fuel efficiency indicators of a passenger car with a gasoline injection system. The engine is equipped with a device additionally supplying liquefied petroleum gas (LPG) and it has an ignition timing variator (ITV). As a result of research, an improvement in the fuel efficiency of a car in thermal equivalent was found when the engine was running on LPG and a slight increase in energy performance was observed. Emissions of pollutants with exhaust gases change in different ways: emissions of carbon monoxide practically do not change, emissions of hydrocarbons and nitrogen oxides are growing, carbon dioxide emissions from LPG operation are reduced, socio-economic damage when the engine is running on LPG is also reduced.

The present study aims to evaluate the emission characteristics for gasoline-fueled vehicles at idling condition. Factors influencing the formation of emissions at different operating conditions are examined. The study is focused on the ignition parameters as well as the mixture quality which are the most important factors affecting the engine performance and emission. A wide range of spark plug gap(0.3- 1.9) mm and ignition timing (10- 1900 BTDC)were employed in the present study. The mixture quality at idling is varied along the flammability limit to clarify its effect on the combustion products concentration. The measurements were carried out on a specified vehicle. Both the engine speed and combustion products concentration were recorded simultaneously. The results indicate the importance of adjusting the idling condition to optimize the exhaust products.

This study present the performance optimization of a spark ignition (SI) engine using gasoline fuels with variations of research octane number (88, 92, and 98) with 40 volume % of bioethanol. The optimization is done by setting the spark ignition time (2° CA advanced) and fuel injection duration (10% reduction) of the engine control module. The engine was tested using an engine dynamometer test to obtain the performance data at the shaft speed of 1000, 1500, 2000, and 2500 RPM and wide-open throttle conditions. From the results of this study, we conclude that optimizing the engine control strategy can lead to the improvement of engine power, torque, and specific fuel consumption which are more significant with the usage of fuels with higher octane number.

Spark-assisted compression ignition (SACI) has a promising potential to substantially improve engine's fuel efficiency. To this end, two exothermic stages in SACI combustion, flame propagation and auto-ignition, need to be well organized to increase control authority of bulk ignition timing especially in lean burn. In this study, three gasoline surrogates, namely EPRF, ETPRF and TPRF, formulated through blending ethanol/toluene with primary reference fuel (PRF) and having the same research octane number (RON) and octane sensitivity (S), were used to conduct experiments in a rapid compression machine (RCM) under lean engine-relevant conditions (10–30 bar and 722–862 K). Under different ethanol blending ratios, both ethanol's synergistic effect during auto-ignition and its stronger pressure dependence of flame speed (S_(Flame)) than toluene were observed. The ethanol's synergistic effect is mainly attributed to its more HO₂ production and then faster consumption by benzyl which results in more OH radical production. As for the stronger pressure dependence of S_(Flame) of ethanol, at 722 K, it is primarily determined by the stronger pressure dependence of H radical in EPRF's flame structure rather than the promotion effect from critical reactions on S_(Flame); while at 862 K, these two factors influence the pressure dependence of S_(Flame) simultaneously. Whatever the temperature is, third-body reactions have larger impacts on ethanol's S_(Flame) than on toluene's. In this study, the relative magnitude of S_(Flame)’s pressure dependence between ethanol and toluene shows rationality at lower φ and higher T, which is in line with the pressure exponents extracted from the existing high-p laminar burning velocities of ethanol and toluene. Further verification was made in a spark-ignition engine, which showed that low-carbon alcohols, exhibited stronger pressure dependence of S_(Flame) than monophenyl aromatics in commercial gasoline, represented by toluene. The aforementioned characteristics of ethanol can be utilized under different engine loads and provide a reference in fuel design for lean SACI combustion.

Purpose This study aims to deal with the large eddy simulation (LES) of an ignition sequence and the resulting steady combustion in a swirl-stabilized liquid-fueled combustor. Particular attention is paid to the ease of handling the numerical tool, the accuracy of the results and the reasonable computational cost involved. The primary aim of the study is to appraise the ability of the newly developed computational fluid dynamics (CFD) methodology to retrieve the spark-based flame kernel initiation, its propagation until the full ignition of the combustion chamber, the flame stabilization and the combustion processes governing the steady combustion regime. Design/methodology/approach The CFD model consists of an LES-based spray module coupled to a subgrid-scale ignition model to capture the flame kernel initiation and the early stage of the flame kernel growth, and a combustion model based on the mixture fraction-progress variable formulation in the line of the flamelet generated manifold (FGM) method to retrieve the subsequent flame propagation and combustion properties. The LES-spray module is based on an Eulerian-Lagrangian approach and includes a fully two-way coupling at each time step to account for the interactions between the liquid and the gaseous phases. The Wall-Adapting Local Eddy-viscosity (WALE) model is used for the flow field while the eddy diffusivity model is used for the scalar fluxes. The fuel is liquid kerosene, injected in the form of a polydisperse spray of droplets. The spray dynamics are tracked using the Lagrangian procedure, and the phase transition of droplets is calculated using a non-equilibrium evaporation model. The oxidation mechanism of the Jet A-1 surrogate is described through a reduced reaction mechanism derived from a detailed mechanism using a species sensitivity method. Findings By comparing the numerical results with a set of published data for a swirl-stabilized spray flame, the proposed CFD methodology is found capable of capturing the whole spark-based ignition sequence in a liquid-fueled combustion chamber and the main flame characteristics in the steady combustion regime with reasonable computing costs. Research limitations/implications The proposed CFD methodology simulates the whole ignition sequence, namely, the flame kernel initiation, its propagation to fully ignite the combustion chamber, and the global flame stabilization. Due to the lack of experimental ignition data on this liquid-fueled configuration, the ability of the proposed CFD methodology to accurately predict ignition timing was not quantitatively assessed. It would, therefore, be interesting to apply this CFD methodology to other configurations that have experimental ignition data, to quantitatively assess its ability to predict the ignition timing and the flame characteristics during the ignition sequence. Such further investigations will not only provide further validation of the proposed methodology but also will potentially identify its shortfalls for better improvement. Practical implications This CFD methodology is developed by customizing a commercial CFD code widely used in the industry. It is, therefore, directly applicable to practical configurations, and provides not only a relatively straightforward approach to predict an ignition sequence in liquid-fueled combustion chambers but also a robust way to predict the flame characteristics in the steady combustion regime as significant improvements are noticed on the prediction of slow species. Originality/value The incorporation of the subgrid ignition model paired with a combustion model based on tabulated chemistry allows reducing computational costs involved in the simulation of the ignition phase. The incorporation of the FGM-based tabulated chemistry provides a drastic reduction of computing resources with reasonable accuracy. The CFD methodology is developed using the platform of a commercial CFD code widely used in the industry for relatively straightforward applicability.

Polyoxymethylene Dimethyl Ethers (PODEn) are a kind of high-activity and promising soot-reduction additive fuel. The effects of enhanced intake charge temperature (Tin) and low fuel-air equivalence...

This paper presents a real-time implementable successive convexification algorithm for a generalized free-final-time six-degree-of-freedom powered descent guidance problem. Building on our previous...

The ignition of ammonia in aqueous solution was simulated in a two-stroke compression ignition engine model. Zero-dimensional chemical kinetic calculations were used to estimate the ignition timing of fuel air mixtures in homogeneous charge compression ignition and diesel combustion modes. The fuel consisted of a 25% m/m aqueous solution of ammonia and pure ammonia for comparison. Ignition was studied by varying the geometric compression ratio of the engine. To ignite ammonia in aqueous solution a minimum compression ratio of 25 was necessary under homogeneous charge compression ignition combustion conditions, whereas under diesel combustion conditions a minimum compression ratio of 27 was required. Ammonia containing ammonium nitrite or hydrogen were two potential ammonia derivatives that were shown to enhance aqueous ammonia ignition in the simulations, and allowed ignition to take place at a compression ratio of 24 for diesel combustion. When comparing the ignition of aqueous ammonia solution to pure ammonia, the minimum compression ratio necessary to ignite pure ammonia was approximately 24.8 and that for aqueous ammonia 26.7 in diesel combustion. This led to the conclusion that aqueous ammonia is not prohibitively more difficult to ignite than pure ammonia. Ammonia containing ammonium nitrite or hydrogen were found to be potential pilot fuels.

In our continual effort to develop an improved performance of a V-twin engine, we investigated the effective release energy, residual gas, peak pressure rise and combustion duration using experimental and simulation approaches. Through combined experimental and simulation methods, the results of the research show that the peak firing pressure rise, combustion duration, and effective release energy were strongly dependent on bore-stroke ratio, while the residual gas was less dependent on bore-stroke ratio. The increase of the bore-stroke ratio led to decrease residual gas ratio, effectively release energy, and increase ignition timing, combustion duration, and volume efficiency. At the bore-stroke ratio of 0.966, the peak firing pressure rise achieved its maximum value of 3.05 bar/deg. The HC and CO emissions were reduced but NOx was increased. At a bore-stroke ratio of 0.8, the maximum engine torque was improved by 7.68 % compared to the reference bore-stroke ratio of 1.06. The engine emitted the least NOx at a 0.88 bore-stroke ratio.

The article indicates the methodology of using vibroacoustic nosting on the example of the gas distribution mechanism (GDM). Until the beginning of 2000 this method was not widely used due to the significant cost diagnostic systems, the complexity of used sensors calibration, the complexity processing and analysis of diagnostic information. Nowadays its’ using is simplified due to the advent of low-cost USB oscilloscopes and high sensitivity real vibration sensors. Moreover, the possibilities for processing diagnostics of statistical data and their presentation have significantly increased. Besides, the car in the field of electronic systems and elements that allow synchronously receiving the necessary diagnostic signal, and then, analyze the received data was significantly improved. Failures of engine timing elements and, in particular, burnout valves, violation of their tightness, phase displacement, the growth of gaps or their absence occur in most vehicles with runs much lower than normal matte or marginal. This is explained by a number of operational factors, such as - untimely maintenance, the use of recommended oils and fuel materials, violation of thermal and load re- bench presses and others. In 30–50% of cases, these factors cause an increase in valve clearances of GDM. In the presented material the studies allowed establish: when tolerance for clearance in the exhaust valve 0.35 ± 0.05 mm set –150–182 mV. The control of gaps in gas distribution mechanism valves revealed 14 deviations of 20 controlled cylinders of the internal combustion engine. Any excess of the amplitude of the signal impulses above 182 mV require adjustment of gaps or replacement of hydraulic pushers. This method and the used set of technological methods allow quickly determine the technical condition of engine systems without disassembly at any intermediate exact conditions of diagnosed objects. This set of diagnostic tools, technological methods and regulatory data allows to recommend their use at modern motor transport enterprises engaged in operation, repair and maintenance of vehicles.

The propagation of combustion wave, which is formed as a result of impact of a filamentary pulsed periodic non-equilibrium discharge on a mixture that is not ignited by only compression in the HCCI engine, has been simulated. The discharge for a short time locally activated the mixture in the engine cylinder at a certain crankshaft rotation angle at the compression stage. The approach to evaluation of the temperature and composition in the region activated by high-frequency corona discharge has been proposed. Multi-pulse and multi-channel nature of discharge was accounted for in our model. The densities of chemically active species produced during streamer propagation were found using two-dimensional axially symmetric fluid model. The obtained composition and temperature in the activated zone were the initial conditions for modeling the propagation of combustion wave along the cylinder radius in 1D approximation. Special terms were included in equations responsible for the compression along the axis of cylinder to mimic the real change in pressure in cylinder. The calculations were performed for a lean C3H8-air mixture, which is characterized by the presence of low-temperature heat release (LTHR) stage, and intermediate and high temperatures heat release (ITHR and HTHR) stages. It was shown that the ignition timing in activated zone depends on the specific energy input into the streamer channel, the radius of activated region coupled with the volume fraction of activated region treated by discharge, and the moment of discharge initiation relative to the top dead center (TDC). The speed of combustion wave, the occurrence of auto-ignition in the end gas and transition to combustion, accompanied by “knocking” or strong pressure fluctuations are largely determined by the moment of discharge initiation and the specific energy input. The significant effect of discharge is explained by the stimulation of oxidation kinetic mechanisms at LTHR and ITHR stages.

In the current investigation, a four stroke, variable speed, single cylinder, variable compression ratio (VCR) SI engine is operated with raw biogas at wide open throttle (WOT) condition and at five different CRs ranging from CR 10 to CR 14 over the operating speed range of the engine. The ignition timing (IT) of the engine is also varied from 23○CA to 47○CA before top dead centre (bTDC) at each operating CR. The optimized operating CR and IT of the engine are obtained through series of experiments and its effects on the performance, combustion and emission characteristic are analysed herein. The rise in operating CR from CR 10 to CR 12 enhanced the power output and efficiency of the biogas fueled SI engine by 12.72% and 5.68%, respectively and reduced fuel consumption by 5.42% at 1400 rpm. Enhancing the CR from CR 10 to CR 12, limited the intensification of NOx and unburnt hydrocarbon emission by 10.17% and 15.6%, respectively at 1400 rpm. Hence, CR 12 is recommended as the optimum CR and its combination with 1400 rpm and WOT setting is recommended as the best operating condition of the engine.

Biodiesels produced from various feedstocks have been considered as alternative fuels used in internal combustion engines without major modifications. This research focuses on producing biodiesel from waste cooking oil (WCOSD) by the catalytic cracking method using MgO as the catalyst and comparing the engine operating characteristics of the test engine when using WCOSD and traditional diesel (CD) as test fuels. As a result, the brake power of the test engine fueled WCOSD, and traditional diesel is similar. However, the engine fuel consumption in the case of using WCOSD is slight increases in some operating conditions. Also, the nitrogen oxides emissions of the test engine fueled WCOSD are higher than those of CD at all tested conditions. The trend is opposite for hydrocarbon emission as the HC emission of the engine fueled by WCOSD reduces 26.3% on average. The smoke emission of the test engine in case of using WCOSD is lower 17% on average than that of CD. However, the carbon monoxide emissions are lower at the low and medium loads and higher at the full loads. These results show that the new biodiesel has the same characteristics as those of commercial biodiesel and can be used as fuel for diesel engines.

This paper includes the experimental test data of an SI engine fuelled with simulated LCV gas (Low Calorific Value), which resembles synthesis gas in composition. The LCV gas was simulated by a mixture of carbon monoxide, hydrogen and nitrogen. During the experiment, the lower heating value of the LCV gas was altered by dilution with nitrogen. A single-cylinder Honda GX270 engine was adopted in the experiment to assess the impact of LCV gas on the system performance. This engine is typically used to power various machines and for electrical energy production in small generator sets. A modified engine was connected to an electric generator, which was loaded with an electric resistor. Engine operation was controlled using a microprocessor controller. All tests were performed at constant engine speed (3000 rpm). The engine was working at wide-open throttle for all mixtures. All mixtures were burned at stoichiometric conditions and with fixed value of ignition timing (30 deg bTDC). The indicated performance of the SI engine was evaluated based on the in-cylinder pressure measurements. No significant impact on the main internal parameters of the tested SI engine fuelled with simulated LCV gas diluted by nitrogen was observed. The experimental tests showed that the combustion duration increased for the mixtures with higher content of inert gas. Increase in the LHV raised the specific emissions of NOx and decreased specific emissions of CO and HC.

Spark assistance for homogeneous charge compression ignition (HCCI) can control combustion phasing, improve thermal efficiency, and reduce emissions in gasoline engines. As the characteristics of flame propagation determine the control authority of ignition timing, it is important and necessary to investigate pressure dependence of flame speed in the lean-premixed mixture relative to engine operating conditions. Experimental study in an optical rapid compression machine (RCM) and simulation work were carried out using two fuels comprising n-heptane/iso-octane/ethanol with varied octane sensitivity (S). The effective pressure ranged from 10 to 35 bar, temperature from 715 to 860 K, and equivalence ratios between 0.3 and 0.7 to cover the region of lean flammability limits of low and high S fuels with ethanol blended. Based on pressure profiles, flame speed extracted from images, and sensitivity analysis of flame speed, the dependence of flame speed on the effective pressure in low and high S fuels was discovered and the fundamental mechanism behind this phenomena became to be understood in the negative temperature coefficient (NTC) and non-NTC regions, respectively. In the studied temperature conditions, the flame speed of high S fuel has stronger dependence on the pressure than that of low S fuel does. In the NTC region, this phenomenon is attributed to the dependence of H radical concentration on pressure in the unburned mixture and flame structure. In the non-NTC region, promoting effect of dominant reactions varied with pressure can significantly influence pressure dependence of flame speed. Although quite limited data of laminar burning velocity for studied fuels were obtained in high pressures (>15 bar), the trend of flame speed's dependence on pressure was well predicted by two models with different but well-accepted core mechanisms, showing consistent results with the experimental ones in the RCM.

Bu çalışmada doğalgazla çalışan direkt enjeksiyonlu benzinli bir motorda ateşleme zamanının yanma ve emisyonlar üzerine etkileri incelenmiştir. Farklı ateşleme zamanları için motorun 3000 devir şartlarında simülasyonlar gerçekleştirilmiştir. Yanma karakteristikleri ve emisyon oluşumlarını incelemek için üç boyutlu hesaplamalı akışkanlar mekaniği kodu olan ANSYS-Forte 19.0 kullanılmıştır. Tüm simülasyonlar farklı ateşleme zamanları için gaz kelebeğinin tam açık konumunda tekrarlanmıştır. Erken ateşleme zamanlamasında silindir içi basıncın yükseldiği görülürken, HC ve CO emisyonlarında düşüş gözlenmiştir. Ayrıca, erken ateşleme şartlarında düşen HC ve CO emisyonlarına rağmen NOx emisyonlarında artış görülmüştür. Sonuç olarak doğalgazlı motorlarda erken ateşleme zamanında daha yüksek yanma verimi elde edilmiştir.

Engine performance parameters, including fuel conversion efficiency (FCE), power, torque and specific fuel consumption (SFC), can be affected by variables such as ignition timing (IGT), injection timing (IT) and hydrogen volume fraction (H2%). In this paper an engine fueled with different H2/CNG blend rations from 0 to 50% volume under ignition and injection timing at different speeds were investigated. For model validation, the engine operating conditions were simulated using the AVL fire software and compared with experimental results. The statistical comparison showed that there was no significant difference between them. Also, a support vector machine (SVM) was used to study the engine's behavior according to the variables studied. The SVM model predicted the FCE, power, torque, SFC and CO with error of less than 4%. The Genetic Algorithm (GA) was used to find optimal IGT, IT and H2% values to achieve optimum engine performance. Therefore, the results showed that the optimum engine operating conditions depend on the engine speed. Also, the results showed that independent variables (IT, IGT and H2%) maximize the engine performance and minimize SFC and CO emission. So that the optimum use of hydrogen in this research at different engine speeds was between 20% and 30%.

The ignition delay in a diesel engine is defined as the time interval between the start of injection and the start of combustion. This delay period consists of (a) physical delay, wherein atomisation, vaporization and mixing of air fuel occur and (b) of chemical delay attributed to pre-combustion reactions. Physical and chemical delays occur simultaneously. To reduce NOx, the method adapted in modern engines is to reduce the ignition delay. For predicting heat release in modern engines, therefore, the estimation of ignition delay is no more important. However, the ceiling on NOx is dipping to such a low level that accurate prediction of ignition delay has become important even if it is small. Ignition delay of diesel sprays is a strong function of ambient temperature and pressure. However, the physical delay has not been modelled satisfactorily in the literature. In this chapter, phenomenological calculations of the cooling of spray surface have shown that the physical parameters and fuel type influence the temperature of the mixture of air and the vapour produced by the first parcel of the injected fuel throughout its life up to ignition. A unique thin-ring like zone on the spray surface is postulated where the preflame reactions have reached a critical level beyond which uncontrolled reactions take place. The time, at which the spray just touches the ring, the ignition is predicted. However, due to turbulence, ignition will take place at only a few points in the neighbourhood of the ring. Detailed consideration of droplet formation, evaporation fuel and preflame reaction has enabled prediction of delay period and location of the ignition accurately within the experimental errors and errors in the input to the calculations.

In this analytical investigation, preheated palm oil was used in the direct injection diesel engine with various optimization methods. The main purpose of the optimization was to get better results than the conventional engine. Raw palm oil was heated using the heat exchange process to reduce the density and viscosity. The relationship between the output process and factors response was evaluated in the design of experiment methods. The Taguchi method is an important method for optimization of the output response performance and emission characteristics of a diesel engine. Two important factors—output and input—were calculated. The input factors considered were preheated palm biodiesel blend, torque, injection pressure, compression ratio, and injection timing. The output factors calculated were smoke opacity, carbon monoxide emission, and brake-specific fuel consumption by using the signal-to-noise (S/N) ratio and analysis of variance. Carbon monoxide was most impacted by torque conditions through injection timing and injecting pressure, and opacity of smoke emission. Among them, injection timing had a higher impact. Different biodiesel blends were prepared: B10 (90% diesel + 10% oil), B20 (80% diesel + 20% oil), B30 (70% diesel + 30% oil) and B40 (60% diesel + 40% oil). Silver nanoparticles (50 ppm) were constantly mixed with the various biodiesel blends. The smoke opacity emission for the biodiesel blend B30 + 50 ppm silver nanoparticle showed the lowest S/N ratio and achieved better optimum results compared with the other blends. The blend B30 + 50 ppm silver nanoparticle showed the lowest S/N ratio value of 9.7 compared with the other blends. The smoke opacity, carbon monoxide emission, and brake-specific fuel consumption of all the response optimal factors were found to be 46.77 ppm, 0.32%, and 0.288 kg/kW·h, respectively.

Natural gas (NG) has many advantages of clean fuels and can replace gasoline in spark ignition (SI) engines. However, it comes with disadvantages such as low energy density. Hydrogen blended NG can improve the fuel characteristics. Ignition timing also plays an important role in engine performance, especially at lean limits. Experiments were conducted for performance and emissions with hydrogen-compressed natural gas (HCNG) blends in a spark ignition (SI) engine with fixed ignition timing. HCNG blends with 0–15% hydrogen were tested with maximum brake torque (MBT) spark timing 30° before top dead center (BTDC) ignition. Significant reduction of carbon monoxide (CO), carbon dioxide (CO2) and hydrocarbons (HC) along with improved break thermal efficiency was observed with higher hydrogen fraction. There was no significant benefit in indicated thermal efficiency or NOx reduction by using MBT ignition. Hence, the expensive retrofitting of using variable spark timing apparatus can be avoided for on-road vehicles.

With the deepening of the oil crisis, more and more vehicles are using CNG vehicles. Although China is relatively rich in natural gas resources, CNG vehicles are very necessary due to their non-renewable resources. In addition, CNG vehicle solar term research is an important part of vehicle energy conservation and emission reduction, an important aspect of promoting sustainable energy development and implementing national energy conservation guidelines and policies, as well as the foundation of building clean and fast modern green transportation concept. Aiming at the phenomenon of high gas consumption of CNG vehicles in operation. Based on the bench test of gasoline /CNG combined fuel engine, this paper uses computer to record and analyze the test data. Through the bench test data, this paper analyzes the influence of too large or too small ignition timing on the gas consumption of CNG engine in idle speed and medium speed. In this way, we actually use CNG vehicles to avoid unnecessary waste of natural gas caused by the ignition timing.

Homogeneous lean spark-ignited combustion is known for its thermodynamic advantages over conventional stoichiometric combustion but remains a challenge due to combustion instability, engine knock and NOx emissions especially at higher engine loads above the naturally aspirated limit. Investigations have shown that lean combustion can partly suppress knock, which is why the concept may be particularly advantageous in high load, boosted operation in downsized engines with high compression ratios. However, the authors have previously shown that this is not true for all cases due to the appearance of a lean load limit, which is defined by the convergence of the knock limit and combustion stability limit. Therefore, further research has been conducted with the alternative and potentially renewable fuel methane which has higher resistance to autoignition compared to gasoline. Operation with a gaseous fuel on high load was achieved by high pressure direct injection and boosting in a single cylinder research engine. To analyse the combustion further, an endoscope allowing optical access to the combustion chamber was utilized to acquire combustion chamber flame images. High load lean operation with methane could confirm the hypothesis that without a knock limit, optimal ignition timing could be maintained resulting in high combustion stability, and the lean load limit mitigated. Instead, limitation was reached due to peak cylinder pressure. Direct injected methane resulted in overall higher combustion stability compared to gasoline. However, methane also provided an overall lower fuel conversion efficiency by 1-2 %-units compared to gasoline. Despite higher combustion stability using methane, the maximum air-dilution could only be marginally extended. Flame images using the endoscope revealed that the flame growth post ignition was prohibited, possibly due to flame quenching, at high turbulence conditions.

Biogas is one of the most promising renewable fuels for application in decentralized energy generation. In this context, gasoline-fueled spark ignition-based engines converted using commercial kits to run as flexible-fuel engines appear to be a low-cost alternative propulsion system. Therefore, this study aims to experimentally evaluate the performance parameters of a biogas-fueled generator set equipped with technology that has already diffused within society. The system comprises a 2.0-L petrol engine coupled to a synchronous generator, the power output, in-cylinder pressure and temperature, stability, and emission data of which were evaluated. The apparatus runs with biogas samples composed of CH4, C2H6, N2, CO2, and traces of other gases, of which the CO2 concentrations vary by up to 14%. The results show that adjusting the ignition timing for an intermediate configuration makes it possible to achieve a flexible fuel engine. In addition, the injection of CO2 into fuel allows an effective reduction of NOx emissions, although with slight decrease in performance. The efficiency decreases with an increase in the CO2 concentration. With 14% CO2, combustion ends at 75.66o on average, which contrasts with other average gaseous fuel combustion endings at 64.05o. Under such operation conditions, the in-cylinder temperature and NOx emission are approximately 1442.91 K and 271.47 ppm. Finally, with CNG, the in-cylinder temperature and NOx emissions are 1758.53 K and 1963.25 ppm on average.

A numerical study of the energy conversion process occurring in a lean-charge cogenerative engine, designed to be powered by natural gas, is here conducted to analyze its performances when fueled with mixtures of natural gas and several percentages of hydrogen. The suitability of these blends to ensure engine operations is proven through a zero–one-dimensional engine schematization, where an original combustion model is employed to account for the different laminar propagation speeds deriving from the hydrogen addition. Guidelines for engine recalibration are traced thanks to the achieved numerical results. Increasing hydrogen fractions in the blend speeds up the combustion propagation, achieving the highest brake power when a 20% of hydrogen fraction is considered. Further increase of this last would reduce the volumetric efficiency by virtue of the lower mixture density. The formation of the NOx pollutants also grows exponentially with the hydrogen fraction. Oppositely, the efficiency related to the exploitation of the exhaust gases’ enthalpy reduces with the hydrogen fraction as shorter combustion durations lead to lower temperatures at the exhaust. If the operative conditions are shifted towards leaner air-to-fuel ratios, the in-cylinder flame propagation speed decreases because of the lower amount of fuel trapped in the mixture, reducing the conversion efficiencies and the emitted nitrogen oxides at the exhaust. The link between brake power and spark timing is also highlighted: a maximum is reached at an ignition timing of 21° before top dead center for hydrogen fractions between 10 and 20%. However, the exhaust gases’ temperature also diminishes for retarded spark timings. Lastly, an optimization algorithm is implemented to individuate the optimal condition in which the engine is characterized by the highest power production with the minimum fuel consumption and related environmental impact. As a main result, hydrogen addition up to 15% in volume to natural gas in real cogeneration systems is proven as a viable route only if engine operations are shifted towards leaner air-to-fuel ratios, to avoid rapid pressure rise and excessive production of pollutant emissions.

In this paper, the effects of external supercharger application on in-cylinder combustion, performance parameters, fuel efficiency and environmental-economic indicators are discussed together regarding a hydrogen-fueled spark ignition engine operating under a lean mixture. The engine was operated at an engine speed of 1600 rpm, under four different boosting pressures (between 10 kPa and 40 kPa), by optimized ignition timing and being compared to a normally aspirated condition. Hydrogen was injected at five bars into the inlet-air. The results show that the indicated mean effective pressure and thermal efficiency increased by 38.9% and 14.2%, respectively, with a 40 kPa boosting pressure under an optimized ignition timing condition according to the normally aspirated engine, and that the cyclic variation decreased by 15.5%. In addition, under 40 kPa boosting pressure, NOx emissions increased by 45.2% and its environmental-social cost increased by 21.8%, while specific fuel consumption and fuel cost were reduced by approximately 18.5%. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The ability to re-ignite at high altitude after a flameout event is critical for flight safety. One reason that makes the relight process of the engine difficult is the low temperature and pressure, which leads to poor atomization, low degree of evaporation and slow reaction rate of the vaporized fuel. For this research work a rectangular, one sector RQL combustion chamber was utilized for experimental investigations at high altitude conditions. The design of the chamber is modular so that experiments for two configurations, i.e. without and with effusion cooling holes can be conducted. The fuel injection and the ignition system are representative of the ones used in commercial aviation. The investigations were performed in the frame of the European research project SOPRANO at the ISCAR rig. The ISCAR rig is capable of generating low pressure and temperature conditions for flowing kerosene-air mixtures. The investigation focuses on the characterization of the ignition process, in terms of probability, minimum fuel to air ratio (FAR) and ignition timing for a successful ignition event. In addition, the unsteady flame kernel generation and propagation were analyzed by high-speed imaging recording. An in-house image processing code was developed in order to derive quantitative spatial information of the flame and overall trends among ignition sequences for the same or different operating conditions. In order to achieve comparability between the investigated configurations (liners without and with effusion cooling), the pressure drop across the nozzle and the liners was the same depending on the operating condition. Results show that both pressure and temperature affect the ignition process, with the former being the dominant parameter in the investigated conditions. In both configurations, the minimum FAR increased as long as the conditions in the chamber became more adverse, indicating that at high altitude low-pressure situations, the performance of the airblast atomizer deteriorated causing poor ignition. This is overcome by creating a richer fuel-air mixture in the primary zone. Finally, the air injected through the effusion cooling holes near the spark seems to create favorable conditions for the ignition process.

The six-stroke spark ignition engine has the potential to be developed as a new alternative to future motor fuel technology. The development of motor vehicles will be directly proportional to the use of rising fossil fuels. It is, therefore, necessary to have renewable alternative fuel, in which one of them is using ethanol fuel. Characteristics of the ethanol fuel are different from fossil fuels so the ignition timing is needed to be modified. The purpose of this study was to determine the effect of the ignition degree on the performance of a 6-stroke spark-ignition engine fuel using ethanol. This research is worked out directly by experimental and testing on the intended object. The test was carried out on an ethanol-fueled 6-step spark ignition engine with variations in the ignition angle at 24 0 ,26 0 and 28 0 . Each variation was tested for a rotation interval of 600 rpm from 2400 rpm to 7200 rpm. The results show that ignition degree greatly affects performance. The ignition angle of 28 0 produced better torque, effective power, effective specific fuel consumption and effective thermal efficiency than those of the ignition degrees at 24 0 and 26 0 (standard angle ). This is due to the use of ethanol fuel which has a slower combustion speed. Based on this fact, it is necessary to advance the ignition angle so that the explosive power of the air-fuel mixture is increasing. Low fuel consumption and better effective thermal efficiency were observed for 28 0 ignition degrees compared to 24 0 and 26 0 ignition degrees.

Developing more energy-efficient and environmentally friendly transportation technologies, that can enable to use significantly less petroleum and to reduce regulated emissions while meeting or exceeding drivers’ performance expectations, has always been one of the main challenges in automotive technology. Therefore, based on an experimental dataset, metamodels were generated using design of computer experiments and central composite design technique in order to accurately predict carbon monoxide (CO), oxides of nitrogen ($$\text {NO}_{x}$$), hydrocarbon (HC) and carbon dioxide ($$\text {CO}_{2}$$) emissions, mean effective pressure and exergy destruction due to heat transfer and combustion process. Combustion metamodels was evaluated varying air–fuel ratio, ignition timing [($$^{\circ }$$CAD) Crank Angle Degrees], compression ratio, and combustion duration ($$^{\circ }$$) on the performance of a Spark Ignition (SI) engine at constant speed of 750 rpm. Because SI gasoline engines always encounter the decreased thermal efficiency and increased toxic emissions at idle (Jurgen in Automotive electronics handbook, McGraw-Hill, New York, 1995). The Akaike information criterion was applied to automatically select the best metamodel for each case.

Purpose The purpose of this paper is to investigate the knock combustion characteristics, including the combustion pressure, heat release rate (HRR) and knock intensity of aviation kerosene fuel, that is, Rocket Propellant 3 (RP-3), on a port-injected two-stoke spark ignition (SI) engine. Design/methodology/approach Experimental investigation using a bench test and the statistical analysis of data to reflect the knock combustion characteristics of the two-stroke SI unmanned aerial vehicle (UAV) engine on RP-3 kerosene fuel. Findings Under the full load condition of 4,000 rpm, at the ignition timing of 25 degree of crank angle (°CA) before top dead centre (BTDC), the knock combustion is sensitive to the thinner mixture; therefore, the knock begins to occur when the excess air ratio is larger than 1.0. When the excess air ratio is set as 1.2, the knock obviously appears with the highest knock intensity. At the excess air ratio of 1.2, better engine performance is obtained at the ignition timing range of 20-30 °CA BTDC. However, the ignition timing at 30° CA BTDC significantly increases the peak combustion pressure and knock intensity with the advancing heat release process. Practical implications Gasoline has a low flash point, a high-saturated vapour pressure and relatively high volatility, and it is a potential hazard near a naked flame at room temperature, which can create significant security risks for its storage, transport and use. The authors adopt a low-volatility single RP-3 kerosene fuel for all vehicles and equipment to minimise the number of different devices using various fuels and improve the military application safety. Originality/value Most two-stroke SI UAV engines for military applications burn gasoline. A kerosene-based fuel for stable engine operation can be achieved because the knock combustion can be effectively suppressed through the combined adjustment of the fuel amount and spark timing.

This work presents an analysis of a diesel power generator converted to operate in Otto cycle using ethanol as fuel. This conversion was done without changing the compression ratio of 17:1, with the build-up of adequate control for intake air mass flow rate, fuel injection, and ignition timing when operating with ethanol. The new conversion approach allows for simplicity of reversion to the original configuration. In Diesel cycle, the engine was fuelled with diesel oil containing 7% biodiesel injected directly into the combustion chamber. The in-cylinder pressure, emissions of carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOX), unburned hydrocarbons (THC), as well as fuel conversion efficiency, when operating with pure hydrous ethanol, were evaluated. The results showed no significant changes on THC emissions in Otto cycle configuration, in comparison with engine operation in Diesel cycle configuration. The emissions of CO2, CO, and NOX were increased when operating in Otto cycle with ethanol.

In the present investigation, experiments were conducted in wide open throttle condition (WOT) for different speed ranging from 1400 rpm to 1800 rpm at an interval of 200 on a single-cylinder four-...

The combustion process in Homogeneous Charge Compression Ignition Engines (HCCI) is one of the new methods of futuristic combustion technologies. Since there is no direct operator for the start of the combustion (SOC) of these engines, air-fuel mixture properties at the moment of entering the combustion chamber, specifies the ignition timing. In HCCI engines, the ignition timing is the most crucial factor in determining other engine operating characteristics such as power output, pollution, and fuel consumption. To control SOC, there should be an accurate predictive model based on the entering air-fuel mixture properties. The Artificial Neural Networks (ANN) approach can be considered as a solution with less computational costs than traditional physics-based modeling. In this investigation, a multi-input single-output model was developed for predicting the SOC of the HCCI engine for a wide range of engine operation. Three popular architectures namely the Nonlinear Autoregressive Network with Exogenous Inputs (NARXNET), Multi-Layer Perceptron (MLP) and Radial Basis Function (RBF) were used, for this purpose. The networks were trained using experimental data taken from a one-cylinder Ricardo engine. The network architecture was optimized using a Genetic Algorithm (GA) method. By using GA, the proposed networks also have the optimum network structures, improved model predictive behaviors, and simulation costs of the learning process. After optimization, the regression ratio between the outputs of MLP and the corresponding experimental data was increased from 0.8965 to 0.96166. This value was improved from 0.7623 to 0.83991 for RBF. By using GA, the time needed to train the NARX was reduced from 3.12 s to 0.46 s. By comparing the model predictions with the experimental data, it was shown that the selected neural network architectures are powerful approaches for non-linear modeling the SOC of the HCCI engine.

Homogeneous Charge Compression Ignition (HCCI) is an advanced combustion technology being considered for internal combustion engines due to the potential for high fuel conversion efficiency and extremely low particulate matter (PM) and Nitrogen Oxides (NOx) emissions. In HCCI engines, there is no direct control method for auto ignition time. A common method to indirectly control the ignition timing in HCCI combustion engines is altering engine’s parameters which can affect the combustion. Previous research has indicated that fuel chemistry has a strong impact on HCCI combustion. This work introduces a new predictive multi-zone model for the description of combustion in HCCI engines. A multi zone model with reduced fuel chemistry was developed to simulate the combustion process in HCCI engines and predict engine performance. In this work, a parametric study on Diesel/Biodiesel blends(D80B20) HCCI combustion is conducted in order to identify the effect of equivalence ratio values (0.1786, 0.27, 0.37, and 0.4762) on combustion and engine performance parameters. Two kinds of parameters will be discussed. First, in-cylinder pressure, temperature and net heat release rate diagrams at altering Diesel/Biodiesel dose (0%, 20%, 40%, 60%), then the second category, the variation of start of combustion and combustion duration which are performance parameters of HCCI Diesel Engine.

Natural gas has been suggested as an alternative fuel for compression ignition (CI) engines because it generates significantly less pollutants and has a smaller carbon footprint, while maintaining the cycle efficiency. However, the high auto-ignition temperature of natural gas typically requires the use of a quasi-compression ignition method such as homogenous charge compression ignition (HCCI) or a dual-fuel mode. Yet, methods such as these are unable to realize the full potential of high efficiency and low emissions. This motivated us to evaluate the applicability of a high-pressure direct-injected natural gas jet for a pure CI engine under various engine load, injection timing, and injection pressure conditions using a single cylinder CI engine with a compression ratio of 15.5. The intake temperature was raised to 400 °C to achieve the auto-ignition temperature of methane after compression and a multi-hole GDI injector capable of operating at a pressure of 400 bar was used for fuel injection. As a result, CI operation was possible, but ignition occurred after the end of the injection in the form of a partially premixed flame rather than a diffusion flame for all conditions under which the engine was operated. A sufficient equivalence ratio of 0.8 was achieved at an injection pressure of 300 bar and injection duration of 1.6 ms with the multi-hole GDI injector, and the GMEP value varied from 2 bar to 5.5 bar according to the equivalence ratio. However, at an equivalence ratio of 0.7 or higher, the combustion efficiency decreased drastically because of the limit of the volume fraction of the piston bowl at TDC and the narrow nozzle distribution of the GDI injector. Measurement of the pollutants indicated that the total number of particles from methane CI operation exceeded that of diesel at an equivalence ratio of 0.74 in the same engine setup because of incomplete combustion; however, the total mass of the particulate matter (PM) was approximately 15% of the diesel because the average particle size from methane CI was approximately one third smaller than that of diesel. However, the high post-compression temperature for the auto-ignition of methane gas resulted in a high peak temperature, which resulted in the production of approximately 2000 ppm NOx under all test conditions. The results of the parametric study showed that, as the injection timing retarded, the ignition timing was almost equally retarded, thus the combustion was still observed in the form of a diffusion flame. As the injection pressure increased, the ignition delay became shorter and the emission of PM could be further reduced, but the NOx emission increased.