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[en] We report our results on non-periodic experimental time series of pressure in a single cylinder spark ignition engine. The experiments were performed for different levels of loading. We estimate the noise level in internal pressure calculating the coarse-grained entropy from variations of maximal pressures in successive cycles. The results show that the dynamics of the combustion is a non-linear multidimensional process mediated by noise. Our results show that so defined level of noise in internal pressure is not monotonous function of loading
[en] Highlights: • A new calibration method is proposed for dual-injection engines under biofuel blends. • Sparse Bayesian extreme learning machine and flower pollination algorithm are employed in the proposed method. • An SI engine is retrofitted for operating under dual-injection strategy. • The proposed method is verified experimentally under the two idle speed conditions. • Comparison with other machine learning methods and optimization algorithms is conducted. - Abstract: Although many combinations of biofuel blends are available in the market, it is more beneficial to vary the ratio of biofuel blends at different engine operating conditions for optimal engine performance. Dual-injection engines have the potential to implement such function. However, while optimal engine calibration is critical for achieving high performance, the use of two injection systems, together with other modern engine technologies, leads the calibration of the dual-injection engines to a very complicated task. Traditional trial-and-error-based calibration approach can no longer be adopted as it would be time-, fuel- and labor-consuming. Therefore, a new and fast calibration method based on sparse Bayesian extreme learning machine (SBELM) and metaheuristic optimization is proposed to optimize the dual-injection engines operating with biofuels. A dual-injection spark-ignition engine fueled with ethanol and gasoline is employed for demonstration purpose. The engine response for various parameters is firstly acquired, and an engine model is then constructed using SBELM. With the engine model, the optimal engine settings are determined based on recently proposed metaheuristic optimization methods. Experimental results validate the optimal settings obtained with the proposed methodology, indicating that the use of machine learning and metaheuristic optimization for dual-injection engine calibration is effective and promising.
[en] An experimental investigation was performed on the influence of the addition of small quantities of Hydrox (hydrogen and oxygen) as generated through electrolysis of water on the performance of a spark ignition engine. A Mazda 1600 cc fuel injected engine connected to a Superflow SF901 dynamometer system was used in this project. The engine was also equipped with a Unichip engine management system in order to enable changes in the spark timing and the amount of fuel injected. Hydrox was generated by an electrolysis process that could either be powered by the engine's alternator or from a separate power source. This hydrox gas produced from the electrolyzer was introduced into the engine's intake manifold and the influence of this was measured on the engine's performance, emissions and fuel consumption. For these tests a typical load condition as experienced for a light passenger car vehicle driven at 100 km/h on the open road was simulated. Typical results for the change in emissions with the hydrox introduction showed a significant reduction in hydrocarbons at lean air-fuel ratio operation of the engine. Additionally with the electrolysis process being driven by the engine a small improvement in fuel consumption was experienced. (author)
[en] The unburnt hydrocarbons by the combustion chamber are pointed at as being the lead covers above the big eities, and thus to be responsible for the 'smog' which 'chokes' these cities. In order to reply to the self-accusing declarations made by the ecologists, one studies, via an ideal model, the various factors contributing to the formation of the nitrogen monoxide in a spark ignition engine. The model used is said to be 'multizonal' because it breaks up the combustion chamber into ten fictitious zones, each one containing the same quantity of fuel. The results do not change if one increases the number of zones beyond ten, The release of heat by combustion obeyed Wiebe's law. The process of combustion is described by a front of flame successively crossing these slices. At every moment the temperature of gases is homogeneous but differs from one zone to another, on the other hand the pressure is the same in all the zones. The exchange of heat and mass between the zones i excluded and the calorific losses through thewalls are expressed using Woschni's formula. The proposed reactional mechanism brings into play 11 intermediate species (CO2, H2O, O2, N2, H2, CO, H, O, OH, N and NO). In addition to the time dependant thermodynamic quantitiesw in each zone (temperature, concentration, ....) are evaluated by the developed computer code as a function of various parameters (richness of carburated mixture, compression ratio, engine speed, duration of combustion, recycling of exhaust gases, advance in ignition,...). The theoretical results obtained from this model of simulation corroborate the measurements currently available in the French Petroleum and Engines Institute of Rueil Malmaison.(Author)
[en] We analyze combustion variations in a four cylinder spark ignition engine. We apply dimensional time series analysis to heat release and construct recurrence plots for different advance angles of spark ignition. The results show that the qualitative change in combustion can be easily related to patterns in recurrence plots. Fluctuations for a larger advance angle have more deterministic nature influenced by an intermittency phenomenon
[en] Highlights: • A normal four-stroke cycle followed by a skip cycle without gas exchange is tested. • The normal and skipped mode results are compared at equal power levels. • The throttle valve is opened wider, thereby resulting in a higher volumetric efficiency. • The pumping work during the gas exchange decreases significantly. • The fuel consumption (BSFC) is reduced by approximately 14–26% under part load conditions. - Abstract: The efficiency decrease of spark ignition (SI) engines under part-load conditions is a considerable issue. Changing the effective stroke volume based on the load level is one of the methods using to improve the part-load efficiency. In this study, a novel alternative engine valve control technique in order to perform a cycle without gas exchange (skip cycle), is examined. The goal of skip cycle strategy is to reduce the effective stroke volume of an engine under part load conditions by skipping several of the four stroke cycles by cutting off the fuel injection and simultaneously deactivating the inlet and exhaust valves. To achieve the same power level in the skip cycle, the cylinder pressure level reaches higher values compared to those in a normal four stroke cycle operation, but inherently not higher than the maximum one at full load of normal cycle. According to the experimental results, the break specific fuel consumption (BSFC) was reduced by 14–26% at a 1–3 bar break mean effective pressure (BMEP) and a 1200–1800 rpm engine speed of skip cycle operation, in comparison to normal engine operation. The significant decrease in the pumping work from the gas exchange is one of the primary factors for an increase in efficiency under part load conditions. As expected, the fuel consumption reduction rate at lower load conditions was higher. These experimental results indicate a promising potential of the skip cycle system for reducing the fuel consumption under part load conditions.
[en] Hydrogen is found to be a suitable alternative fuel for spark ignition engines with certain drawbacks, such as high NOx emission and small power output. However, supercharging may solve such problems. In this study, the effects of equivalence ratio, compression ratio and inlet pressure on the performance and NOx emission of a four stroke supercharged hydrogen engine have been analyzed using a specially developed computer program. The results are verified and compared with experimental data obtained from tests on a Ricardo E6/US engine. A chart specifying the safe operation zone of the hydrogen engine has been produced. The safe operation zone means no pre-ignition, acceptable NOx emission, high engine efficiency and lower specific fuel consumption in comparison with the gasoline engine. The study also shows that supercharging is a more effective method to increase the output of a hydrogen engine rather than increasing the compression ratio of the engine at the knock limited equivalence ratio
[en] Hydrogen has long been recognized as a fuel having some unique and highly desirable combustion properties, such as a wide flammable mixture range, low ignition energy, very fast flame propagation rates and clean combustion products especially without greenhouse gases. These features made H2 an excellent fuel for both traditional and emerging innovative power devices such as spark ignition engines and fuel cells. The application of H2 makes it possible for these devices to potentially meet the ever increasingly stringent environmental controls of exhaust emissions, including the possible elimination of green house gas emissions. This paper contributes to the experimental examination of H2 applications in spark ignition engines. The detailed engine performance including the onset of knock, lean operational limits and exhaust emissions is to be presented. Comparison with the corresponding performances of other common gases fuels such as natural gas is made. The optimization of spark timing for efficiency and for the avoidance of knock while maintaining high thermal efficiency is also to be discussed. (author)
[en] We analyse the combustion process in a spark ignition engine using the experimental data of an internal pressure during the combustion process and show that the system can be driven to chaotic behaviour. Our conclusion is based on the observation of unperiodicity in the time series, suitable stroboscopic maps and a complex structure of a reconstructed strange attractor. This analysis can explain that in some circumstances the level of noise in spark ignition engines increases considerably due to nonlinear dynamics of a combustion process