Abstract
As the most reliable alternative energy source for traditional fuel engines, natural gas has been widely used in inland river marine engines. The natural gas engine is faced with the problem of increased cyclic variations under the condition of lean combustion. In this paper, a multi-point injection spark ignition natural gas engine is tested under different lean burn degrees to investigate the correlation between different parameters and cyclic variation, including accumulated heat release, combustion phase and burning rate. The purpose is to clarify the optimized technical route for marine natural gas engine. A new method to quantify the correlation between parameters and cyclic variation is proposed. The maximum explosion pressure of combustion and its phase are used as the parameters to characterize the cyclic variation. Different parameters are then nonlinearly fitted to it, and the R-S value of the fitting is used to quantify the correlation between parameters and cyclic variation. The results show that the correlation between accumulated heat release and cyclic variation is less than 10%. The main factors causing the cyclic variation are the fluctuation of ignition delay and initial flame propagation, whose correlation with cyclic variation is over 80% and 70%, respectively.
Highlights
Natural gas has become the most reliable alternative energy source for engines due to its abundant reserves, low price and clean combustion [1–3]
Distribution is carried out, and the degree of correlation between different parameters and PMAX distribution is used as an index to evaluate its correlation with cyclic variation
In order to clarify the reasons for the fluctuation of PMAX, and further clarify the degree of correlation between each parameter and the cyclic variation, the third part quantitatively analyzes the correlation between the accumulated heat release, combustion phase parameters and cyclic variation
Summary
Natural gas has become the most reliable alternative energy source for engines due to its abundant reserves, low price and clean combustion [1–3]. In the Chinese inland marine engine market, the application of natural gas is becoming more and more extensive. For a vehicle’s natural gas engines, in order to meet the strict emission regulations, equivalent ratio combustion and three-way catalytic converter are used to control emissions. Especially Chinese inland waterway marine engines, the current emission regulations are relatively loose compared with vehicle engine’s emissions. From July 2021, the emission regulations for inland marine engines in China entered the second phase, namely China II emission standard. The NOx + NMHC emission is limited to 5.8 g/kWh (1.2 L ≤ single cylinder displacement ≤ 5 L), which is 7.2 g/kWh during the first phase
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