Comparative analysis and normalization of single-hole vs. multi-hole spray characteristics: 1st report on spray characteristic comparison

Abstract

The single hole injector, known for its simple design and ease of measurement, is widely utilized in optical spray experiments; however, multi-hole injectors are commonly applied in real engine applications. The structural differences between the two leads to variations in spray characteristics. This series of studies, based on the principles of similarity and normalization, proposes a theory for the transformation of spray characteristics between different hole numbers injectors. The 1st report investigates the spray characteristics of different hole numbers injectors under super high injection pressure conditions. Using the Diffuser BackgroundImaging (DBI) method, the experimental pressure range covers 100-300 MPa. The research indicate that the single-hole injector exhibits a shorter initial injection delay, while the multi-hole injector demonstrates a more stable injection flow rate and greater penetration. At higher pressures, the velocity increase, especially at 300 MPa. Higher ambient density has a suppressive effect on spray tip velocity and alters spray morphology. Moreover, it was observed that while the initial spray velocity of the single-hole injector is relatively higher, the penetration of the multi-hole injector significantly exceeds that of the single-hole injector in the later stages. For multi-hole injectors, interactions between adjacent sprays lead to a relatively narrower spray angle. The ratio of spray angle to cone angle for both injectors remain nearly unaffected by changes in density and injection pressure. In general, the Naber and Siebers model is better suited for predicting penetration in single-hole injectors under conditions of high density and ultra-high injection pressure (200-300 MPa). This study not only highlights the distinctive spray characteristics under super high pressure conditions but also offers valuable theoretical foundations and experimental insights for optimizing diesel engine design.

Keywords

Diesel spray / Single-hole injector / Small hole diameter injector / Super high pressure

CRediT authorship contribution statement

Chang Zhai: Writing - original draft, Investigation, Data curation. Junyu Zhang: Formal analysis, Writing - review & editing. Kuichun Li: Writing - review & editing, Supervision, Investigation. Pengbo Dong: Writing - review & editing, Investigation. Yu Jin: Writing - review & editing, Data curation. Feixiang Chang: Data curation, Formal analysis. Hongliang Luo: Writing - review & editing, Supervision.

Funding

This study was financially supported by the Open Research Subject of Key Laboratory of Fluid Machinery and Engineering (Xihua University), Sichuan Province (LTJX-2024 002), the National Key Laboratory of Marine Engine Science and Technology (LAB-2023-01), the Open Fund of Key Laboratory of Oil & Gas Equipment, Ministry of Education (Southwest Petroleum University) (OGE202302-04), the Fundamental Research Funds for the Central Universities (3072023CFJ0304), and the Funded by Shandong Postdoctoral Science Foundation (SDCX-ZG-202400247), China Postdoctoral Science Foundation (2024M760290).

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors would like to thank Mazda for supplying the injection system and Nac for offering technical support.

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