Abstract
With the increasingly stringent CO2 emission regulations, the degree of strengthening of the engines is increasing. Under high-pressure conditions, the airway throat parts of the intake and exhaust systems have a great influence on the flow loss of the diesel engine. The reasonable distribution of the throat area of the intake and exhaust ports in the limited cylinder headspace is key to improving the performance of supercharged engines. This study took a large-bore, high-pressure ratio diesel engine as the research object. Firstly, the three-dimensional (3D) flow simulation method was used to reveal the influence law of different throat areas on the engine intake and exhaust flow under steady-state conditions, and a steady-flow test bench was built to verify the accuracy of the simulation model and law. Secondly, based on the 3D steady-state calculation and test results, a more accurate one-dimensional simulation model was constructed, and a joint optimization simulation platform was established based on the dynamic data link library. On this basis, the mathematical description of the multi-objective optimization of airway throat size was established using machine learning methods, such as a genetic algorithm, the design domain and boundary conditions of variable parameters were clarified, and the collaborative optimization objective of integrated flow coefficient and flow loss is proposed to achieve the fast and accurate optimization of intake and exhaust throat diameters.
Highlights
In recent years, due to the implementation of fuel consumption regulations, engines’degree of strengthening has increased, and their boost degree has increased
For high-boost-ratio diesel engines, this paper focuses on the key issues, such as the influence law of intake and exhaust ports with different throat diameters on flow coefficient and the interaction relationship between the airway throat area ratio and the flow loss and establishes an efficient and accurate simulation platform and method for the joint optimization of airway throat size by integrating machine learning theory
The research results are as follows: (1) A 3D steady-state simulation model is established for a diesel engine with different throat diameters, and the MAP diagrams of flow coefficient are calculated for different pressure ratios, different pressure differences and different valve lifts
Summary
Due to the implementation of fuel consumption regulations, engines’degree of strengthening has increased, and their boost degree has increased. How to quickly and reasonably distribute the throat area of the intake and exhaust ports in the highly compact cylinder headspace has become a key issue, restricting the further development of the engine [5,6] To solve this problem, an efficient and accurate prediction model is proposed in this paper, and a fast and accurate matching of performance of a large-bore, high-pressure ratio diesel engine and intake and exhaust throat diameters is achieved. The influence of different intake and exhaust port throat diameters, different intake pressures, different intake pressure differences and different valve lifts on the flow coefficient of high-pressure-ratio engines is insufficient and needs further research
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