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Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To reduce knock and keeping low NOx emissions and high indicated thermal efficiency (ITE) in a hydrogen fuel engine, the comprehensive effects of ammonia substitution rate (ASR), compression ratio (CR), and ignition timing (IT) on its combustion and its NOx emissions were studied numerically. Based on a four‐cylinder gasoline direct injection (GDI) engine, it was modified into an ammonia/hydrogen dual‐fuel (AHDF) spark ignition (SI) engine. The simulation was conducted by GT‐Power software, and simulation data were validated through experiments. 2500 rpm_50% load was selected for the research. ASR, CR and IT vary from 0% to 20%, 10.5 to 8.5, and −24 to 0°CA ATDC, respectively. The findings indicate that increasing ASR decreases the maximum pressure rise rate (MPRR) and the knock index (KI), improving the ITE, but increasing NOx emissions. Based on 20% ASR, CR was optimized. The findings indicate that decreasing CR reduces the MPRR and KI, but increasing NOx emissions and decreasing the ITE. Finally, based on CR of 9, IT was optimized. The findings indicate that delaying IT reduces the MPRR and KI, but also has a certain impact on NOx emissions and ITE. After compromise consideration, the optimal IT in this study was selected as −9°CA ATDC. [ABSTRACT FROM AUTHOR]

Ammonia is a very promising alternative fuel for internal combustion engines, but there are some disadvantages, such as difficulty in ignition and slow combustion rate when ammonia is used alone. Aiming to address the problem of ammonia combustion difficulty, measures are proposed to improve ammonia combustion by blending hydrogen. A one-dimensional turbocharged ammonia-hydrogen engine simulation model was established, and the combustion model was corrected and verified. Using the verified one-dimensional model, the effects of different ratios of hydrogen to ammonia, different rotational speeds and loads on the combustion performance are investigated. The results show that the ignition delay and combustion duration is shortened with the increase of the hydrogen blending ratio. The appropriate amount of hydrogen blending can improve the brake's thermal efficiency. With the increase in engine speed, increasing the proportion of hydrogen blending is necessary to ensure reliable ignition. In conclusion, the ammonia-hydrogen fuel engine has good combustion performance, but it is necessary to choose the appropriate hydrogen blending ratio according to the engine's operating conditions and requirements. [ABSTRACT FROM AUTHOR]

This study presents an experimental investigation into the impact of blending bioethanol (E100) with conventional gasoline (E0), incrementally increasing biofuel levels up to E10, E50, and E70. The test was carried out in two stages: Stage I assessed the engine's performance under fixed speeds (n = 2000 rpm and n = 2500 rpm) and fixed throttle positions (15%, 20%, and 25%) to measure changes in engine torque, efficiency, and environmental metrics by varying the concentration of bioethanol in the fuel. Stage II aimed to enrich the initial findings by conducting an additional test, running the engine at a fixed speed (n = 2000 rpm) and braking torque (MB = 80 Nm) and varying the ignition timing. Results indicated slight improvements in engine brake torque and thermal efficiency (up to 1.7%) with bioethanol content increased to 70%, and a notable reduction in incomplete combustion byproducts—carbon monoxide and hydrocarbons emissions (up 15% and 43%). Nitrogen oxide emissions were reduced by up to 23%, but carbon dioxide emissions decreased by a mere 1.1%. In order to increase thermal efficiency by adding higher bioethanol blend concentrations, adjusting the ignition timing to counter the longer ignition delay is necessary; however, higher emissions of nitrogen oxides and hydrocarbons are a major drawback of such a strategy. The results of the research are important in determining the optimal concentration of bioethanol in the mixture with gasoline for the energy and environmental sustainability of a spark ignition engine. [ABSTRACT FROM AUTHOR]

Changing the ignition advance angle has a significant impact on the performance of a combustion engine. Optimization of ignition advance angle is a major task of adjusting the engine concerning emission standards, fuel consumption, torque value, etc. The results of the research showed that the process of optimizing the ignition advance curve can noticeably increase engine efficiency, as well as torque and power output from the engine while reducing fuel consumption as a result of lower indications of the air flow mass per second from MAF sensor (mass air flow sensor). The highest impact of the ignition advanced angle modifications can be seen in the area of the highest volumetric efficiency of the tested combustion engine. Almost no impact is observed within high engine speed levels. Simultaneously increasing engine load and rotation speed increases the possibility of engine knocking, which has a devastating effect on engine durability. [ABSTRACT FROM AUTHOR]

Background: Wildfires are thought to become more prevalent during periods of extended dry weather. This issue is examined using two dryness metrics commonly applied in Australian fire management agencies. Aims: This paper investigated links between wildfire incidence and the Keetch–Byram Drought Index (KBDI) and McArthur's Drought Factor (DF) across the state of Victoria, Australia. Methods: Weather records and data from 41 418 wildfires that occurred across the State over a 17-year period were compiled to examine the distributions of KBDI and DF on days with fires smaller and larger than 5 ha in area and all days, using kernel density plots. Key results: Days with fires, particularly days with fires that escaped initial attack, have higher DFs and KBDIs compared with all days. These differences vary between regions and are greatest in areas with moist climates. Conclusions and implications: An appreciation of dryness conditions using tools such as KBDI and DF is useful for understanding fire potential, particularly in areas that experience higher and more regular rainfall. McArthur's Drought Factor and the Keetch–Byram Drought Index are higher than normal on days with fires in Victoria, Australia. These metrics provide a more reliable indication of fire potential in high-rainfall areas than in lower-rainfall areas. This article belongs to the Collection Fire and Climate. [ABSTRACT FROM AUTHOR]

Natural gas (NG) is a potential alternative fuel for carbon neutral and has been received increasing attentions on its combustion behaviors in engine. However, there is little systematic quantitative investigation on the combustion characteristic of purified NG (methane) engine. In this study, the sweeping tests for compression ratio (CR), ignition timing, and hydrogen addition were conducted on a heavy-duty truck liquid methane engine, and the influence factors of ignition delay and combustion rate at each stage were quantitatively investigated. Some new findings and interesting conclusions were obtained. Overall, CR especially the higher CR has small effect on the ignition delay of methane engine (less than 2 deg). Under all the conditions discussed, the ignition delay almost linearly increases with the advance of ignition timing, resulting in the slight advance of start of combustion (SOC). Compared with ignition timing, hydrogen addition has larger effect on SOC since it reduces ignition delay largely (up to 7.3 deg at 1400rpm). By increasing hydrogen addition, the CA10–50 shortens slightly while CA50–90 elongates largely, resulting in a rising trend in CA10–90 finally. All these have extended the research on methane engine and are useful to improve its combustion performance. [ABSTRACT FROM AUTHOR]

This study investigates a direct injection (DI) engine fueled with compressed natural gas (CNG) enrichment with hydrogen blend (HCNG) in counter from the conversion of the port injection gasoline engine. The intention of the investigation was to examine the performance and exhaust gases from the effect of excess air ratio and timing angle changes in consequence of hydrogen increment to natural gas in comparison to gasoline engine performance and exhaust gases as a single fuel. The compression ratio was set at 14:1 with varying load at 3000 rpm, and the ignition timing was applied at −17, −19, −21, and −34°bTDC at WOT, and the amount of hydrogen enrichment to natural gas was applied at 10%, 20%, 30%, and 40%. The conditions on torque, power, heat release rate, brake specific fuel consumption, CO, and NOx were studied. Results showed that the power and torque increased by 8% with increasing the hydrogen content to 40% in fuel composition and advancing ignition timing and heat release rate as well as decreasing λ from 1.4 to 1.2 relative to the stoichiometric state. Also, the specific fuel consumption decreased by 18.5% in the optimal condition. [ABSTRACT FROM AUTHOR]

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-stroke port-injected; spark-ignition engine. The engine fueled with equi-volume blend of methanol/gasoline was tested for different ignition timing and its effects on engine characteristics. The experiment results shown, retardation of ignition timing to 14⁰ BTDC exhibits excellent results compared to 24⁰ BTDC ignition timing. The results obtained show a good agreement of improvisation observed with M50 fuel in terms of BTE and BSEC at a speed of 1600 rpm when compared to gasoline fuel. The optimal ignition timing attributes to good combustion efficiency with increasing cylinder pressure and heat release rate. However, low carbon–hydrogen ratio and oxygen content in methanol aids to reduced NOx, HC, and CO emissions by 50%, 35%, and 40%, respectively. The small increase of 10% in CO2 emission is observed; this is due to retardation of ignition time, which allows the M50 fuel to absorb sufficient energy and achieve complete combustion. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The spark plug of an opposed‐piston two‐stroke (OP2S) gasoline engine is arranged on the side wall of the cylinder liner, far from the center of the combustion chamber; the ignition core of the mixture is offset, the flame propagation distance is increased, the combustion duration is prolonged, and the knock tendency is severe. In this paper, a quasi‐dimensional two‐zone combustion model is used in GT‐Power software to establish a thermodynamic process simulation model and a knock prediction model is included to analyze the effect and matching of the compression ratio, ignition timing, and other thermodynamic process parameters on the knock intensity and engine performance. The extended coherent flame model combustion model is coupled with the Huh–Gosman spray model in AVL‐Fire software, and the An B knock model is used to establish an in‐cylinder combustion model and analyze the flame propagation and the knock response rate of the flat and pit piston during the combustion process. With an increase of the compression ratio, the temperature and pressure of the mixture in the combustion chamber increase at the time of ignition, which leads to the knocking combustion in the cylinder. With an increase of the ignition advance angle, the in‐cylinder pressure and temperature increase rapidly, which increases the likelihood of knocking combustion. In comparison with the pit piston combustion chamber, the flame propagation speed of the flat piston combustion chamber is relatively slow, which increases the knock tendency. The results show that lowering the compression ratio and delaying the ignition can reduce the in‐cylinder knock tendency by setting a compression ratio of 10.5 and an ignition advance angle of 20°CA. When the pit piston is used to organize the squish and inverse squish before and after the inner dead center, the flame propagation process can be promoted. The knock response rate of pit piston is 24.7% lower than that of flat top piston. [ABSTRACT FROM AUTHOR]

For electric reliability and to save energy, the distributed power generation combining cooling and heating supply called a CCHP system for architectures has many potential advantages and is widely adopted to provide electric power and to satisfy local heating and cooling loads by waste heat recovery with low carbon intensity. However, the current CCHP system usually has a fixed ratio of the power and heat due to the features of its power unit, which leads to difficulties in the load management. In this paper, based on the operation of an internal combustion engine fueled with natural gas, a novel method is proposed and studied to achieve a controllable rate of heat/power to meet different load requirements of the electricity and heat (cooling or heating loads). By varying the ignition timing of the spark ignition engine, the combustion process within the cylinder can be adjusted to occur at different crank angles so that the engine crank shaft output power (related to the generated electricity) and the heat from the exhaust gas are changed accordingly. To study the effects of ignition timing on engine power and exhaust heat energy, a two-zone model was established with a predictive combustion model. The changes in the combustion process, output power, exhaust gas temperature, and heat energy were mostly our concern. The results show that the heat/electricity ratio can be adjusted from normally 1.0 to 1.6, and they can be controlled independently under partial load operating conditions. To solve the potential thermal failure of the turbine, the extraordinarily high exhaust temperature will be adjusted by compressed air. [ABSTRACT FROM AUTHOR]

The application of hydrogen fuel in ORP engines makes the engine power density much higher than that of a reciprocating engine. This paper investigated the impacts of combustion characteristics, energy loss, and NOx emissions of a hydrogen-fuelled ORP engine by ignition timing over various equivalence ratios using a simulation approach based on FLUENT code without considering experiments. The simulations were conducted under the equivalence ratio of 0.5~0.9 and ignition timing of −20.8~8.3° CA before top dead centre (TDC). The engine was operated under 1000 RPM and wide-open throttle condition which was around the maximum engine torque. The results indicated that significant early ignition of the ORP engine restrained the flame development in combustion chambers due to the special relative positions of ignition systems to combustion chambers. In-cylinder pressure evolutions were insensitive to early ignition. The start of combustion was the earliest over the ignition timing of −17.3° CA for individual equivalence ratios; the correlations of the combustion durations and equivalence ratios were dependent on the ignition timing. Combustion durations were less sensitive to equivalence ratios in the ignition timing range of −14.2~−11.1° CA before TDC. The minimum and maximum heat release rates were 15 J·(°CA)−1 and 22 J·(°CA)−1 over the equivalence ratios of 0.5 and 0.9, respectively. Indicated thermal efficiency was higher than 41% for early ignition scenarios, and it was significantly affected by late ignition. Energy loss by cylinder walls and exhaust was in the range of 10~16% and 42~58% of the total fuel energy, respectively. The impacts of equivalence ratios on NOx emission factors were affected by ignition timing. [ABSTRACT FROM AUTHOR]

Hydrogen can be used as a fuel for internal combustion engines to realize a carbon-neutral transport society. By extending the lean limit of spark ignition engines, their efficiency, and emission characteristics can be improved. In this study, stratified charge combustion (SCC) using monofueled hydrogen direct injection was used to extend the lean limit of a spark ignition engine. The injection and ignition timing were varied to examine their effect on the SCC characteristics. An engine experiment was performed in a spray-guided single-cylinder research engine, and the nitrogen oxide and particulate emissions were measured. Depending on the injection timing, two different types of combustion were characterized: mild and hard combustion. The advancement and retardation of the ignition timing resulted in a high and low combustion stability, respectively. The lubricant-based particulate emission was attributed to the in-cylinder temperature and area of the flame surface. Therefore, the results of the study suggest that the optimization of the hydrogen SCC based on the injection and ignition timing could contribute to a clean and efficient transport sector. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Biodiesel is a clean energy source that helps in the reduction of environmental pollution as compared to fossil fuel. This study aimed to improve the performance of combustion and reduce emission in direct injection rotary engine by fueling it with biodiesel as well as selecting the best ignition time. A 3D‐dynamic simulation model was established and then coupled with biodiesel chemical kinetics mechanism. On this basis, investigation of five ignition timings (IT) was conducted to know their various effects on combustion process. The simulation results showed that properly advancing IT increased in‐cylinder pressure, with the peak pressure (Pmax) of 35°CA (BTDC) IT of 45.99 bar the largest. Comparing IT of 35°CA (BTDC) with the IT of the original engine showed an 18.14% increase in peak pressure. The corresponding crank angle (φmax) for Pmax values also proved that when the IT was advanced, φmax values decreased and that of 35°CA (BTDC)‐10.37°CA (ATDC), 30°CA (BTDC)‐11.46°CA (ATDC), and 25°CA (BTDC)‐13.88°CA (ATDC) were better because they were generally between 10–15°CA (ATDC), which contributes to better engine performance. With advanced IT, phase of total period during combustion was continuously brought forward due to flame propagation acceleration by tumble as well as increase of tumble residence effect time that aided in improving the combustion rate. The burnt fuel mass fractions at TDC of 40°CA (BTDC) IT of 0.94 was the highest followed by 35°CA (BTDC) IT of 0.88. Under this computational condition, 35°CA (BTDC) was deemed to be the improved combustion scheme though soot exhaust increased. [ABSTRACT FROM AUTHOR]

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effects of varying the ignition timing on the performance and emissions characteristics of a crank-rocker engine were experimentally investigated. Experiments were carried out at five different ignition timings of 6.5°, 8.5°, 10.5°, 12.5°and 14.5° CA BTDC at engine speed of 2000rpm and wide open throttle position. Performance data such as brake torque, brake power, brake specific fuel consumption and brake thermal efficiency were calculated. Engine exhaust gas emission such as CO, CO2, HC and NOx have also been measured. The results showed that at 10.5° CA (BTDC) ignition timing, the crank-rocker engine produce maximum brake torque, brake power, BTE and minimum value for the BSFC. In general, CO and HC emissions decreased while CO2 and NOx emissions increased with ignition timing advance. The findings in this paper are useful for researchers and engine developers in understanding the trade-offs and physical limitations of crank-rocker engine designs. [ABSTRACT FROM AUTHOR]

This paper presents the design and statistical validation of a Spark Ignition Internal Combustion Engine Electronic Control Unit (ECU), implementing ignition and fuel injection algorithms in an automotive grade Freescale Power PC microcontroller. Crankshaft position, intake manifold temperature and pressure, coolant temperature and throttle position were instrumented. In addition a communication interface using CAN protocol was developed for the real time acquisition of the parameters, through which engine performance in a linear range at constant load was validated comparing the design with the manufacturers ECU. Statistical analysis shows that for future hardware-in-the-loop testing, variation introduced by the hardware is negligible and will be solely due to the improvement proposals or model selection. [ABSTRACT FROM PUBLISHER]

The pressure and temperature during liquid rocket engine ignition drastically increase because of energy generation from the severe combustion reaction of pure oxidizer and fuel. Studies on the ignition of oxygen/kerosene combustion are scarce. This research observes ignition transition of a gaseous oxygen/kerosene spray by directly visualizing the combustion flow field using a windowed combustor and high-speed shadowgraph imaging technique. The hydrodynamic characteristics of a propellant feed system are investigated before the ignition experiments by analyzing the time responses of propellant injection pressures and a high-speed movie of developing spray during injection. The experiments are performed with a 22.5 ms fuel pre-injection sequence. The high-speed shadowgraph imaging and dynamic pressure measurement results are analyzed. The effects of ignition timing on the ignition transition are focused on. The early ignition timing results in the smoothest ignition and longest ignition delay time from the propellant injection related to an ignitable transient spray condition. The combustion pressure rapidly increases with ignition timing delay. A peak pressure caused by propellant mixture accumulation is also observed. The ignition delay is less than 5 ms, and slightly decreases as the ignition timing is further delayed. [ABSTRACT FROM AUTHOR]

Ignition system is the main important part of the engine, and has absolute influence on engine performance. OpenECU for ignition timing strategy on the basis of the design and calibration work, greatly shorten the development difficulty and cycle; machine of a LNG gas ignition timing strategy has carried on the design and optimization, and combining the calculation model for the engine (air intake, compression, power, and exhaust) feedback and verification. It can save a lot of time and resources for experiment if experiments use openECU. It also can monitor the influence of the different inputs conditions on the ignition advance angle. It has realized the map of calibration, greatly shorten the development work and has certain actual application value. [ABSTRACT FROM AUTHOR]

In the actual content of pollution regulations for the automotives, the use of alternative fuels becomes a priority of the thermal engine scientific research domain. From this point of view bioethanol can represents a viable alternative fuel for spark ignition engines offering the perspective of pollutant emissions reduction and combustion improvement. The paper presents results of the experimental investigations of a turbo-supercharged spark ignition engine (developed from a natural admission spark ignition engine fuelled with gasoline) fuelled with bioethanol-gasoline blends. The engine is equipped with a turbocharger for low pressure supercharging, up till 1.4 bar. An correlation between air supercharging pressure-compression ratio-dosage-spark ignition timing-brake power is establish to avoid knocking phenomena at the engine operate regime of full load and 3000 min-1. The influences of the bioethanol on pollutant emissions level are presented. [ABSTRACT FROM AUTHOR]

Copyright of Scientific Bulletin of National Mining University is the property of National Mining University, State Higher Educational Institution and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Late-phasing homogeneous charge compression ignition operating conditions have the potential to expand the useful operating range of homogeneous charge compression ignition in internal combustion engines. However, significant combustion instabilities can occur at late-phasing operating conditions. Combustion phasing and work output variations at these conditions are characterized by a pattern in which the combustion phasing alternates between being earlier than the desired timing and later than the desired timing. This characteristic can be traced to a negative eigenvalue in a simplified, discrete-time analytical model of homogeneous charge compression ignition dynamics. The model forms the basis for the design of a simple controller that is shown to reduce combustion timing variations in simulation. Experimental results illustrate the controller successfully reduces the cyclic variations in combustion by altering the exhaust valve timing, resulting in stable combustion and an expanded operating range. [ABSTRACT FROM PUBLISHER]

The number of engine control actuators and potential fuel sources are constantly increasing to meet fuel economy targets and global energy demand. The increased engine control complexity resulting from new actuators and fuels motivates the use of model-based control methodologies over map-based empirical approaches. Purely physics-based control techniques have the potential to decrease calibration burdens but must be complex to represent nonlinear engine behavior with low computational requirements. Artificial neural networks are recognized as powerful tools for modeling systems which exhibit nonlinear relationships, but they lack physical significance. Combining these two techniques to produce semiphysical artificial neural network models which provide acceptable accuracy while minimizing the artificial neural network size, the calibration effort and the computational intensity is the focus of this research. To minimize the size of the neural network, sensitivity analyses are carried out on the critical inputs and the minimum number of required neurons. The most critical physical parameters are selected as follows: the laminar flame speed; the turbulence intensity; the total in-cylinder mass. The control algorithm derivation is described, and the process validated in real time using an engine dynamometer. The real-time experimental results demonstrate that the semiphysical artificial neural network approach can produce accurate ignition timing control for both gasoline and E85. Robustness of the semiphysical neural network approach is also discussed on the basis of the real-time experimental results. [ABSTRACT FROM PUBLISHER]

The effects of EGR and ignition timing on engine emissions and combustion were studied through an experiment carried out on an air-guided GDI engine. The test results showed that the ignition timing significantly affected the GDI engine emissions, that the NO x emissions significantly reduced when the ignition timing was retarded, and that NO x emissions decreased with the EGR level increasement. A higher EGR rate could reduce CO emissions while the CO emissions were less affected by the ignition timing. The HC emissions decreased at a lower EGR rate. At 2500 r/min, an appropriate EGR rate could cut down CO emissions. The exhaust gas temperature could significantly decrease with improving the EGR rate, and the exhaust gas temperature at 2500 r/min was clearly higher than that at 1850 r/min. The nucleation mode particles increased clearly, the accumulation mode particle number decreased gradually with the increase of EGR rate, and the typical particle size of nucleation mode particle was in the range of 10–25 nm. [ABSTRACT FROM AUTHOR]

The pressure to improve automotive fuel economy and emissions has driven the introduction of more complex spark ignition engines. As the number of control actuators increases, traditional ignition timing calibration and control methods become restrictive, creating a need for new feedforward approaches to manage transient operation. This research was conducted to determine whether a control-oriented turbulent flame entrainment model could be developed to predict the ignition timing of an engine with a large number of control actuators. A physics-based approach is used to capture the influence of additional control actuators on the complex interactions affecting the ignition timing. Each actuator is characterized by its influence on the fundamental combustion parameters, such as the residual gas fraction and the turbulence intensity. Experimental results are used to generate semiempirical input and combustion models that are capable of running in real time within an engine controller. The model is used to predict the combustion duration, from the spark to 50% mass fraction burned, at every crank angle position within a reasonable ignition timing window for each engine operating point. With minimal engine mapping, the model was capable of predicting the spark timing to within several degrees of ideal values, demonstrating the feasibility of this approach for use in high-degrees-of-freedom spark ignition engines. [ABSTRACT FROM AUTHOR]

Fluctuating fuel prices and associated pollution problems of largely exploited petroleum liquid fuel has stimulated the research on abundantly available gaseous fuels to keep the mobility industry intact. In the present work an air cooled diesel engine was modified suitably into a spark ignition engine incorporating electronic ignition and variable speed dependant spark timing to accommodate both LPG and CNG as fuels. Engine was optimized for stoichiometric operation on engine dynamometer. Materials of a few intricate engine components were replaced to suit LPG and CNG application. Ignition timing was mapped to work with gaseous fuels for different speeds. Compensation was done for recovering volumetric efficiency when operated with CNG by introducing more volume of air through resonator. Ignition timing was observed to be the pertinent parameter in achieving good performance with gaseous fuels under consideration. Performance and emission tests were carried out on engine dynamometer and chassis dynamometer. Under wide open throttle and at rated speed condition, it was observed that the peak pressure with LPG was lying between diesel fuel and CNG fuel operation due to slow burning nature of gaseous fuels. As compression ratio was maintained same for LPG and CNG fuel operation, low CO emissions were observed with LPG where as HC + NOx emissions were lower with CNG fuel operation. Chassis dynamometer based emission tests yielded lower CO2 levels with CNG operation. [ABSTRACT FROM AUTHOR]

A cycle-resolved analysis system was designed with the specified measurement instruments to investigate the characteristics of combustion stability in a mild gasoline hybrid powertrain. A Fast Response Flame Ionization Detector (FFID), cylinder pressure transducer and engine torque transducer were used to observe both the engine-out THC emissions and engine performance during a brief moment of engine restart. This research aimed to improve combustion stability and was performed by varying the battery State Of Charge (SOC), injection duration and ignition timing. The results indicate that engine combustion tends to be more stable with longer fuel injection durations and advanced ignition timing, while the effect of the battery SOC is negligible. Also, peculiar differences in the catalyst conversion efficiency at the front and rear of the catalyst during engine restart and deceleration were revealed, with the degree of HC oxidation being the suspected cause. This study not only analyzed the engine control and engine-out total hydrocarbon (THC) emission characteristics, but also implemented control strategies that allowed for combustion stability during engine stop and restart operation. [ABSTRACT FROM AUTHOR]

The cyclic variations of homogeneous charge compression ignition (HCCI) ignition timing is studied for a range of charge properties by varying the equivalence ratio, intake temperature, intake pressure, exhaust gas recirculation (EGR) rate, engine speed, and coolant temperature. Characterization of cyclic variations of ignition timing in HCCI at over 430 operating points on two single-cylinder engines for five different blends of primary reference fuel (PRF), (iso-octane and n-heptane) is performed. Three distinct patterns of cyclic variation for the start of combustion (SOC), combustion peak pressure (Pmax), and indicated mean effective pressure (i.m.e.p.) are observed. These patterns are normal cyclic variations, periodic cyclic variations, and cyclic variations with weak/misfired ignitions. Results also show that the position of SOC plays an important role in cyclic variations of HCCI combustion with less variation observed when SOC occurs immediately after top dead centre (TDC). Higher levels of cyclic variations are observed in the main (second) stage of HCCI combustion compared with that of the first stage for the PRF fuels studied. The sensitivity of SOC to different charge properties varies. Cyclic variation of SOC increases with an increase in the EGR rate, but it decreases with an increase in equivalence ratio, intake temperature, and coolant temperature. [ABSTRACT FROM AUTHOR]

An experimental study on the combustion and emission characteristics of a direct-injection spark-ignited engine fueled with natural gas/hydrogen blends under various ignition timings was conducted. The results show that ignition timing has a significant influence on engine performance, combustion and emissions. The interval between the end of fuel injection and ignition timing is a very important parameter for direct-injection natural gas engines. The turbulent flow in the combustion chamber generated by the fuel jet remains high and relative strong mixture stratification is introduced when decreasing the angle interval between the end of fuel injection and ignition timing giving fast burning rates and high thermal efficiencies. The maximum cylinder gas pressure, maximum mean gas temperature, maximum rate of pressure rise and maximum heat release rate increase with the advancing of ignition timing. However, these parameters do not vary much with hydrogen addition under specific ignition timing indicating that a small hydrogen fraction addition of less than 20% in the present experiment has little influence on combustion parameters under specific ignition timing. The exhaust HC emission decreases while the exhaust CO2 concentration increases with the advancing of ignition timing. In the lean combustion condition, the exhaust CO does not vary much with ignition timing. At the same ignition timing, the exhaust HC decreases with hydrogen addition while the exhaust CO and CO2 do not vary much with hydrogen addition. The exhaust NOx increases with the advancing of ignition timing and the behavior tends to be more obvious at large ignition advance angle. The brake mean effective pressure and the effective thermal efficiency of natural gas/hydrogen mixture combustion increase compared with those of natural gas combustion when the hydrogen fraction is over 10%. [ABSTRACT FROM AUTHOR]

Emission regulations for automobiles have become more stringent and the improvement of emission during cold start has been a major key issue to meet these regulations. Among many kinds of factors that affect cold start operation, ignition timing is crucial to improve emission characteristics due to the influence on exhaust gas temperature. Recent progress in variable valve timing allows optimized valve event strategies under various ranges of engine operating conditions including cold start. This study investigates effects of ignition and exhaust valve timing on exhaust gas temperature, combustion stability and emission characteristics through cold start bench tests of an SI engine. Experimental results show that exhaust valve timings and ignition timings significantly affect exhaust gas temperature and stability of engine operation under cold start condition. Exhaust valve timing also affects CO and NOx emission due to changes in residual gas fraction of the combustion chamber. Ignition timing mainly affects exhaust gas temperature and HC emission. A control strategy, advanced exhaust valve timing and retarded ignition, is plausible in order to achieve reduction of exhaust emission while maintaining stability under cold start operation of SI engines. [ABSTRACT FROM AUTHOR]

There is an inherent difficulty in trying to distinguish between the thermodynamic and the chemical effects in a homogeneous charge compression ignition (HCCI) engine. This article attempts to isolate the chemical kinetics effects in the framework of a zero-dimensional, thermo-kinetic model combined with a detailed chemical mechanism for iso-octane and an auto-ignition correlation. The study focuses on the behavior of single-stage ignition fuels near top dead center (TDC), as a means of relating conditions at TDC to predicted ignition timings. It is found that a unique relationship exists between combustion phasing, and the constant volume ignition delay at TDC conditions expressed in crank angle degrees (CAD). This relationship holds for given engine parameters and composition over a wide range of RPM. For ignition near TDC, the ignition delay at TDC conditions expressed as a crank angle interval must be between 8 and 12 CAD, depending on engine design parameters. [ABSTRACT FROM AUTHOR]

In this work fuel and ignition control techniques are developed for articulated rod, large-bore, two-stroke, natural-gas-fuelled engines. A Cooper-Bessemer GMV-4TF engine is utilized for the experimental investigation. Due to the articulation of the connecting rods, the even hank cylinders have different piston position and port opening profiles and different compression ratios than the odd bank cylinders. Additionally, due to the mechanical design of the engine, ignition and top dead centre (TDC) for the cylinders are not evenly spaced. The non-symmetric timing and articulated geometry result in different gas flow characteristics for each cylinder bank. These differences result in increased NO, emissions of the even cylinder bank compared with those of the odd bank. Results of engine testing have demonstrated that this difference can be compensated for through hank specific fuel and ignition control. Two separate control techniques were utilized for compensation. The first resulted in decreased fuel consumption at a constant NOx level, and the second produced reductions in NOx emissions at a constant fuel consumption. [ABSTRACT FROM AUTHOR]

In diesel engines, most of the fuel is burned in a diffusion combustion phase, which inherently leads to the formation of excessive amounts of soot and NOx emissions. In order to decrease soot and NOx emissions simultaneously, the concept of a lean homogeneous charge compression ignition engine has been proposed. The onset of the combustion of the engine depends on the autoignition of the fuel, so it is quite difficult to control the ignition timing. On the other hand, it has been revealed that Pulsed Flame Jet (PFJ) has a great potential to enhance ignition reliability and burning rate in lean mixtures. In this article, autoignition characteristics of n -butane/air mixtures in a rapid compression machine (RCM) were shown first. The appearance of low temperature flames was observed in autoignition of n -butane in the RCM used here, and it was realized that the final compression conditions in the RCM correspond to the upper end of the low-temperature range of the positive temperature dependence region of ignition delay. Then the combustion tests with PFJ were carried out and it was demonstrated that the onset of combustion can be controlled by PFJ, and it was revealed that PFJ has a potential for the ignition timing control of the homogeneous charge compression ignition engine. [ABSTRACT FROM AUTHOR]

Ignition control is an important issue in homogeneous charge compression ignition (HCCI) engines, which have the advantages of low NO[sub x] emission and high thermal efficiency. In this study, the effect of the exhaust gas recirculation (EGR) on the ignition control of HCCI engines is discussed using an engine cycle simulation in which a homogeneous mixture is assumed. Auto-ignition of 65 per cent iso-octane + 25 per cent toluene + 10 per cent n-heptane, which is used as a fuel to evaluate the characteristics of a gasoline-like fuel, is represented by a detailed reaction model. The dilution by EGR delays the ignition timing when the charged gas temperature is not changed by EGR. The temperature rise of the charged gas promotes auto-ignition. Based on these characteristics, it was suggested that the ignition timing could be controlled by EGR with temperature control, when the amount of fuel supply is constant. This control method can also be applied to control of the air–fuel ratio (A/F) in the cylinder while maintaining the optimum ignition timing. In spite of the difference in the A/F and the EGR ratios, no significant difference was found in the pressure rise rate at combustion and the NO[sub x] emission when the ignition timing was the same. [ABSTRACT FROM AUTHOR]

The ignition timing of an SI engine is a critical parameter. The influence on residual gas, effective release energy, and emissions characteristics of ignition timing for the V-twin engine is investigated in this research. For this purpose, an experiment system was built with a dynamometer, and a model of the simulation was created. In this research, the ignition timing was varied from 10 to 45 degrees BTDC under full load operating conditions, with engine speeds ranging from 3000 to 10,000 rpm. Based on the output data, ignition timing has a major impact on the proportion of residual gas, efficient release energy, performance of the engine, and the emission characteristics. The smallest proportion of residual gas was 0.07% at 8000 rpm and ignition timing of 10 °CA. At 15 °CA of ignition timing, the highest efficient release energy was 0.817 kJ at 4000 rpm, while at 8000 rpm and 25 °CA of ignition timing, it was 0.8305 kJ. At 6000 rpm, the greatest braking torque of the engine was 21.57 Nm, while the minimal BSFC was 343.821 g/kWh. The nitrogen oxide emission and HC emission increase with the advanced ignition timing, but CO emission decreases. [ABSTRACT FROM AUTHOR]

The level of hydrocarbon (HC) emissions, from a spark-ignition engine using a 30 % iso-butanol-gasoline blend was experimentally investigated. Experiments were conducted on a Hydra single-cylinder, spark-ignition, fuel-injection engine. HC emissions were measured as a function of fuel air equivalence ratio, ignition timing and engine speed. The effect of varying the temperature of cooling water on HC emissions was also investigated under three fuel air equivalence ratios (lean, stoichiometric, and rich). Results show that retarding ignition timing with respect to maximum break torque (MBT) has a great effect on HC emissions reduction, where for lean mixture, Phi 0.85, retarding ignition timing by 6 degrees from MBT reduces the exhaust HC emissions by 12 %. The level of HC emissions is also reduced by 30 % at MBT, as the cooling water temperature increase from 55 to 90 C. It is noticed that as the engine speed increases, the level of HC emissions decrease. [ABSTRACT FROM AUTHOR]

The gasoline/natural gas dual-fuel combustion mode has been found to have unique advantages in combustion. The ignition timing has a significant impact on the combustion characteristics of gasoline engines. Thus, here we study the combustion characteristics of gasoline/natural gas dual-fuel combustion mode to determine the details of their respective advantages under cooperative combustion. A direct-injection turbocharged gasoline engine was modified, and an engine experimental platform was built for the coordinated control of gasoline direct-injection and natural gas port injection. A low-speed and low-load operating point was selected, and the in-cylinder pressure, heat release rate, pressure rise rate, combustion temperature, ignition delay, and combustion duration under the coordinated combustion of gasoline and natural gas dual fuel at the ignition moment were studied through bench tests among other typical combustion parameters. The results show that with the increase of the ignition advance angle, the maximum cylinder pressure, heat release rate, pressure rise rate, and maximum combustion temperature increase. The ignition advance angle is 28°CA-BTDC, and PES40 has the best fuel synergy effect and the best power performance improvement. The effect of the advance of the ignition advance angle on the ignition delay and the combustion duration reaches the peak at 20°CA-BTDC–22°CA-BTDC, and the improvement of the two periods is more significant at PES60. [ABSTRACT FROM AUTHOR]

The combustion characteristics of an opposed-piston two-stroke gasoline engine are investigated with experiment. The energy conversion and exergy destruction are analyzed and the organization method of the combustion process is summarized. The effects of phase difference, scavenging pressure, injection timing, ignition timing, and dual spark plug ignition scheme on the combustion process and engine performance are discussed, respectively. The heat release rate of the opposed-piston two-stroke gasoline engine is consistent with the conventional gasoline engine. With the increase of opposed-piston motion phase difference, the scavenging efficiency decreases and overmuch residual exhaust gas is not beneficial to the combustion process. Meanwhile, the faster relative velocity of the opposed-piston near the inner dead center enhances the cylinder working volume change rate, which leads to the rapid decline of in-cylinder pressure and temperature. The 15 °CA of opposed-piston motion phase difference improves the scavenging and combustion process effectively. When scavenging pressure is 0.12 MPa, the scavenging efficiency and heat release rate are improved at medium-high speed conditions. With the delay of injection timing, the flame developing period decreases gradually, and the rapid burning period decreases and then increases. The rapid burning period may reach the minimum value when the injection advance angle is 100 °CA. With the delay of ignition timing, the flame developing period increases gradually, and the rapid combustion period decreases and then increases. The rapid combustion period may reach the minimum value when the ignition advance angle is 20 °CA. Notably, the flat-top piston structure should be matched with the dual spark plug, which the ignition advance angle is 20 °CA at medium-high load conditions. [ABSTRACT FROM AUTHOR]

Low-temperature combustions (LTCs), such as homogeneous charge compression ignition (HCCI), could achieve high thermal efficiency and low engine emissions by combining the advantages of spark-ignited (SI) engines and compression-ignited (CI) engines. Robust control of the ignition timing, however, still remains a hurdle to practical use. A novel technology of jet-controlled compression ignition (JCCI) was proposed to solve the issue. JCCI combustion phasing was controlled by hot jet formed from pre-chamber spark-ignited combustion. Experiments were done on a modified high-speed marine engine for JCCI characteristics research. The JCCI principle was verified by operating the engine individually in the mode of JCCI and in the mode of no pre-chamber jet under low- and medium-load working conditions. Effects of pre-chamber spark timing and intake charge temperature on JCCI process were tested. It was proven that the combustion phasing of the JCCI engine was closely related to the pre-chamber spark timing. A 20 °C temperature change of intake charge only caused a 2° crank angle change of the start of combustion. Extremely low nitrogen oxides (NOx) emission was achieved by JCCI combustion while keeping high thermal efficiency. The JCCI could be a promising technology for dual-fuel marine engines. [ABSTRACT FROM AUTHOR]