Showing papers on "Spark-ignition engine published in 2022"

Comparison of Random Forest and Neural Network in Modeling the Performance and Emissions of a Natural Gas Spark Ignition Engine

Abstract: Abstract Machine learning (ML) models can accelerate the development of efficient internal combustion engines. This study assessed the feasibility of data-driven methods toward predicting the performance of a diesel engine modified to natural gas (NG) spark ignition (SI), based on a limited number of experiments. As the best ML technique cannot be chosen a priori, the applicability of different ML algorithms for such an engine application was evaluated. Specifically, the performance of two widely used ML algorithms, the random forest (RF) and the artificial neural network (ANN), in forecasting engine responses related to in-cylinder combustion phenomena was compared. The results indicated that both algorithms with spark timing (ST), mixture equivalence ratio, and engine speed as model inputs produced acceptable results with respect to predicting engine performance, combustion phasing, and engine-out emissions. Despite requiring more effort in hyperparameter optimization, the ANN model performed better than the RF model, especially for engine emissions, as evidenced by the larger R-squared, smaller root-mean-square errors (RMSEs), and more realistic predictions of the effects of key engine control variables on the engine performance. However, in applications where the combustion behavior knowledge is limited, it is recommended to use a RF model to quickly determine the appropriate number of model inputs. Consequently, using the RF model to define the model structure and then using the ANN model to improve the model’s predictive capability can help to rapidly build data-driven engine combustion models.

A review of the pre-chamber ignition system applied on future low-carbon spark ignition engines

Abstract: Legislations for greenhouse gas and pollutant emissions from light-duty vehicles are pushing the spark ignition engine to be cleaner and more efficient. As one of the promising solutions, enhancing the ignition energy shows great potential in simultaneously mitigating combustion knock and enabling lean-burn operation. Featured with distributed ignition sites, pre-chamber ignition systems with large or small pre-chamber volumes, auxiliary or no auxiliary fueling, and large or small orifices have gained a surge of interest in decreasing the fuel consumption and pollutant emissions. This paper aims at presenting a comprehensive review of recent progress and development trends of pre-chamber ignition systems adopted on future low-carbon and low-emission spark ignition engines. First, mechanisms behind this technology are discussed from the perspectives of the pre-chamber scavenging and combustion, jet ejection, main chamber combustion, and emission formations. Second, the design criteria of pre-chamber geometries are presented in detail, followed by a discussion on the fuel and air management for the main chamber. Next, recent numerical and experimental studies on the pre-chamber ignition system and its applications in conjunction with other complementary technologies are summarized. Finally, critical issues for commercialization and future research directions are discussed.

An evaluation of the conversion of gasoline and natural gas spark ignition engines to ammonia/hydrogen operation from the perspective of laminar flame speed

Abstract: Power generation systems will reduce carbon emissions primarily through the application of low or even zero carbon fuels under the global decarbonization trend. Ammonia is an ideal alternative fuel because it is cheap, readily available, and easy to store and transport. However, its mediocre combustion performance has raised concerns about its use in engines. The objective of this paper was to evaluate the amount of hydrogen that would need to be added to the ammonia from a laminar flame speed perspective if converting existing spark ignition engines to ammonia operation. The benchmark for determining the hydrogen blending ratio was to help ammonia achieve efficient combustion in the cylinder comparable to that of gasoline or natural gas. The results showed that hydrogen addition had the potential to greatly improve engine efficiency and emissions, although the combustion kinetics of ammonia-hydrogen mixtures were still dominated by ammonia with hydrogen addition levels below 60%. In addition, the hydrogen addition ratio was mainly determined by the kernel inception process, as this burning stage heavily influenced the repeatability of the combustion and the ease of combustion control. Also, at least 20% of hydrogen was required to be added to ammonia to adapt the engine to various operating conditions, while such a strategy still cannot help ammonia to obtain a rapid burning event compatible with gasoline or methane. Moreover, natural gas engines were more suitable for retrofitting to ammonia-hydrogen operation because they have a higher compression ratio and their combustion chambers are less demanding on the fuel laminar flame speed. Further, ammonia lean operation was recommended to be avoided in spark ignition configurations. Overall, all of these findings support the need for additional efforts in ammonia engine optimizations and onboard ammonia dissociation system efficiency improvements.

Alcohol Fuels in Spark Ignition Engines

Abstract: Carbon dioxide (CO2), nitrogen oxides (NOx) and soot emissions are primary concerns and the most investigated topics in the automotive sector. Indeed, recent governments directives push toward carbon–neutral mobility by 2050. In this framework, zero-carbon fuels, as hydrogen, or renewable low carbon alcohol fuels, play a fundamental role. To this aim, in this chapter, the main results on largely used alcohol fuels application in spark-ignition (SI) engines are discussed. Aspects inherent ethanol and methanol production processes, chemical-physical properties and their application in SI engines are presented. Different engine fuelling strategies, dual fuel and blend are analysed. Alcohols have higher enthalpies of vaporisation and research octane number (RON) values as well as excellent anti-knock ability compared to gasoline. This effect enhances in dual fuel mode. Ethanol and methanol have higher thermodynamic conversion efficiencies than gasoline combustion. Cycle to cycle variation is in line with gasoline values. In general, NOx decreases with alcohol fuels, and the best results are achieved in blend mode with a reduction of up to 30% with methanol compared to gasoline. Independently of the fuelling mode, significant benefits on particle number emissions are observed by using alcohol fuels. Carbon monoxide (CO) and hydrocarbons (HC) emission trends strongly depend on fuelling mode and engine operating conditions. Additionally, the lower carbon content of alcohol fuels reduces the CO2 emissions up to 10% compared to reference gasoline.KeywordsSpark ignitionMethanolEthanolDual fuelFuel blendCO2Emissions