Purpose: Owing to the excellent performance, giant magnetostrictive materials (GMMs) are widely used in many engineering fields. The dynamic Jiles–Atherton (J-A) model, derived from physical mechanism, is often used to describe the hysteresis characteristics of GMM. However, this model, despite cited by many different literature studies, seems not to possess unique expressions, which may cause great trouble to the subsequent application. This paper aims to provide the rational expressions of the dynamic J-A model and propose a numerical computation scheme to obtain the model results with high accuracy and fast speed.Design/methodology/approach: This paper analyzes different published papers and provides a reasonable form of the dynamic J-A model based on functional properties and physical explanations. Then, a numerical computation scheme, combining the Newton method and the explicit Adams method, is designed to solve the modified model. In addition, the error source and transmission path of the numerical solution are investigated, and the influence of model parameters on the calculation error is explored. Finally, some attempts are made to study the influence of numerical scheme parameters on the accuracy and time of the computation process. Subsequently, an optimization procedure is proposed.Findings: A rational form of the dynamic J-A model is concluded in this paper. Using the proposed numerical calculation scheme, the maximum calculation error, while computing the modified model, can remain below 2 A/m under different model parameter combinations, and the computation time is always less than 0.5 s. After optimization, the calculation speed can be enhanced with the computation accuracy guaranteed.Originality/value: To the best of the authors’ knowledge, this paper is the first one trying to provide a rational form of the dynamic J-A model among different citations. No other research studies focus on designing a detailed computation scheme targeting the fast and accurate calculation of this model as well. And the performance of the proposed calculation method is validated in different conditions.

Based on the structure of direct-drive injectors, the giant magnetostrictive actuator (GMA) for direct-drive injectors designed with giant magnetostrictive materials (GMMs) shows great application prospects in the field of fuel injection. This paper establishes the mathematical model of GMA for direct-drive fuel injector. The numerical model of the GMA is built by means of the Advanced Modeling Environment for performing Simulation of engineering systems (AMEsim) simulation platform combined with the working process of the actuator. A prototype was fabricated, and the correctness of the numerical model was verified by experiments. Through AMEsim, the magnetic potential distribution law, unit step response, and frequency characteristics were analyzed, it is found that the relationship between the magnetic potential and the current on the GMM is approximately linear, and the ratio of the magnetic potential to the total magnetic potential of the magnetic circuit is about 0.9; the unit step response shows that the actuator has a fast response speed, the rise time is about 240 µs, and when the output displacement enters the 5% and 2% error bands, the adjustment time is 540 and 810 µs, respectively; by inputting the sweep signal, it is obtained that the natural frequency of the actuator is about 700 Hz, and the output amplitude is relatively “smooth” with a bandwidth of 0–250 Hz. This research enriches the research methods of GMAs and provides a novel idea for the development of high-performance fuel injectors.

Serving as one of the core component, the excitation coil can exert remarkable influence on the output performance of giant magnetostrictive actuator (GMA) for electronic controlled fuel injector. In this paper, a multi-objective coil optimization scheme is proposed to balance the conflicting response speed and magnetic field intensity determined by the coil parameters. Firstly, a physics-based coil model is established for optimization, whose parameters can be directly calculated by the coil dimensions. Then, with the current response of the coil calculated, a multi-objective optimization framework is conducted attempting to get the selection guideline for the enameled wire diameter of the coil. The optimal choices exist when the outer diameter of the enameled wire falls in 0.9∼1.6 mm, and the inner/outer diameter ratio is relatively high. Finally, a series of experiments are conducted and the results indicate that the proposed model is able to accurately describe the current response throughout the operating frequencies, and the optimization scheme can provide a valuable roadmap to design coil for high performance GMA.

At present, the research of electronically controlled injectors is mostly limited to the non-direct drive structure. Although the research on the direct drive structure is involved, it mostly stays in the conceptual machine or simulation stage. In this paper, based on the direct-drive structure, the giant magnetostrictive material is used as the energy conversion material, the prototype of the direct-drive giant magnetostrictive fuel injector is designed and manufactured, and the experimental test system and AMESim simulation model are built. By means of experiment and simulation, the injection characteristics of Giant magnetostrictive injector (GMI) are tested. It is found that the minimum single injection quantity of GMI is 5.9 mm³ under the condition of 30 MPa rail pressure, which shows high injection accuracy. The experimental results are in good agreement with the simulation results under different driving pulse widths and voltages. When the driving pulse width is not less than 650 µs, the relative errors are all less than 5%, which verifies the effectiveness of the simulation model. The injection performance of GMI is analyzed. The results show that this injector has a stable injection performance, fast response speed (the shortest injection pulse width is about 200 µs), and the injection process can be completed five times in 5 ms.

The related parameters of electronically controlled injector have profound influence on the fuel injection performance of injector. However, most of the current researches focus on some parameters of actuator, but few on some parameters of nozzle. Based on the direct-drive giant magnetostrictive injector, the simulation model of this injector was built with AMEsim simulation software, and the effects of nozzle parameters such as half cone angle of needle valve, diameter of needle valve stem and diameter of nozzle hole on the injection performance of this injector were studied. In view of the many research parameters, the orthogonal experiment method was adopted to design the experimental scheme reasonably, and finally L16 (45) orthogonal experimental table was selected for the experiment. The results show that the parameters that have the greatest and smallest influence on the fuel injection performance of this injector are the cavity parameters and the number of injection holes. The optimum combination of nozzle parameters was obtained, and the fuel injection performance of injectors before and after the optimization of nozzle parameters was compared. It was found that the optimized combination of nozzle parameters had a better correspondence between fuel injection rate and needle valve displacement, which provided the possibility for further improving the flexibility of fuel injection rate.