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Open AccessArticle

A Study on the Optimal Actuation Structure Design of a Direct Needle-Driven Piezo Injector for a CRDi Engine

1
Department of Mechanical Engineering, Graduate School, Soongsil University, Seoul 06978, Korea
2
Department of Mechanical Engineering, Soongsil University, Seoul 06978, Korea
*
Author to whom correspondence should be addressed.
Academic Editor: Jose Ramon Serrano
Appl. Sci. 2017, 7(4), 320; https://doi.org/10.3390/app7040320
Received: 13 January 2017 / Revised: 13 March 2017 / Accepted: 14 March 2017 / Published: 24 March 2017
(This article belongs to the Special Issue Internal Combustion Engines (ICE) for Ground Transport)
Recently, the high-pressure fuel injection performance of common-rail direct injection (CRDi) engines has become more important, due to the need to improve the multi-injection strategy. A multiple injection strategy provides better emission and fuel economy characteristics than a normal single injection scheme. The CRDi engine performance changes with the type of high-pressure electro-mechanical injector that is used and its injection response in a multi-injection scheme. In this study, a direct needle-driven piezo injector (DPI) was investigated, to optimize its actuation components, including the plate length, number of springs, and the elasticity of the spring between the injector needle and the piezo stack. Three prototype DPIs were proposed by this research. They were classified as Type 1, 2, and 3, depending on whether the injector needle was hydraulic or mechanical. Then, the optimal prototype was determined by conducting four evaluation experiments analyzing the maximum injection pressure, injection rate, spray visualization, and real engine combustion application. As a result, it was found that the Type 3 DPI prototype, with several pan-springs and plates, had the highest injection pressure, a steady injection rate, and the fastest spray speed. It also demonstrated the most effective emission reduction for a two-stage rapid spray injection in a single-cylinder CRDi engine. The Type 3 DPI displays an increased elasticity from its hydraulic needle that provides a synergy effect for improving DPI actuation. View Full-Text
Keywords: direct needle-driven piezo injector; high-pressure injection pressure; injection rate; spray visualization; CRDi engine direct needle-driven piezo injector; high-pressure injection pressure; injection rate; spray visualization; CRDi engine
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Han, S.; Kim, J.; Lee, J. A Study on the Optimal Actuation Structure Design of a Direct Needle-Driven Piezo Injector for a CRDi Engine. Appl. Sci. 2017, 7, 320.

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