Optimized Control For Hydrogen-fueled Engine Based On Signal Processing

As the enhance of the environment protection consciousness and the aggravation of petroleum shortage force people to look for―clean energy‖, hydrogen energy is receiving wide attentions due to its cleanness, high efficiency and reproducibility, and is getting onto the energy stage of 21st century, even may become a leading actor. For these reasons people are filled with full expectations. Hydrogen, as a kind of fuel of internal-combustion engines, has many advantages and is expected to be the best alternative energy sources. However, because of its differences with petroleum in the physicochemical properties, hydrogen is apt to have some problems in the working process of hydrogen engines, such as pre-ignition, backfire and decrease of engine power. How to solve the conflict problem between the abnormal combustion and the power increase of hydrogen engine is a key issue to promote the research and technology progress.The research history and technology situation of hydrogen energy and hydrogen-fueled engines as well as the development and technical level of fuel battery vehicles are summarized first. And then the features of hydrogen-fueled internal combustion engines and the crucial problems of development are briefly analyzed, based on which the idea that hydrogen-fueled engines will come into the market ahead of fuel battery vehicles is put forth. The discussion results show that the research of hydrogen-fueled engines has its academic significance and application prospects.An electrical control system design of hydrogen-fueled engine and the corresponding hardware and software development of the electrical control system is completed in this paper. In order to improve burning efficiency an optimization control scheme is proposed which can solve the contradiction between avoiding abnormal combustion and improving hydrogen engine power, laying an experimental foundation for the burning features research and optimization control of hydrogen-fueled engines.An experimental study is also carried out in depth in terms of multi-parameters balance of hydrogen-fueled engine and its optimization control , primarily including the mutual relationships among the emission characteristics after the hydrogenation of petrol engine, the power factor and the economy factor, the relationship between hydrogenation amount and the working condition changes and the relationship between some important working parameters such as injection timing, fire timing, compression ratio and excess air ratio etc., and the burning patterns. Detailed and accurate experimental data results are provided. An important conclusion is presented that the hydrogen injection time and firing time play a key role in improving the engine capability, which is valuable for optimization control.Based on the study of the abnormal combustion mechanism of hydrogen-fueled engine including preignition, tempering, cyclic variations, as well as the relationship among various abnormal combustions, a serious of conclusions are provided which are as follows. The preignition and tempering generally occurs in the hydrogen engine whose mixed gas is formed externally. Tempering can occur either in thick or thin mixed gas, and preignition can convert to temper. The phenomenon of cyclic variations in hydrogen-fueled engine is more obvious than others. Various currently available technologies of restraining abnormal combustion in hydrogen-fueled engine are summarized in this paper.In order to solve the technical problems of preignition and backfire in hydrogen-fueled engine, a new method of optimizing adjustment of ignition timing angle and spraying amount of inlet pipe is proposed in this paper, which can not only solve this problem but also take into account both power factor and economy factor.In regard to the modeling and the optimization control of hydrogen-fueled engine burning process, A state-space-based analysis method of nonlinear control system is firstly introduced and combined with the thermodynamics analysis methods of quality transference and power transference in this paper, based on which the state space model of hydrogen engine nonlinear burning control system is presented. Some problems such as the linearization, controllability and stability are discussed. The state space model can now be equivalently converted to optimization control model with respect to some working parameters and some performance index. This theoretical achievement provided a theoretical analysis and experimental research foundations for the optimization control of engines, especially for solving the problem of the conflict between abnormal combustion and hydrogen-fueled engine power improvement.In regard to optimization design of burning control model, this paper, targeting at the case of multiple working conditions, multiple targets, multiple variables and multiple restrictions to solve ignition timing and hydrogen injection timing, the nonlinear programming theory is firstly combined with multiple targets genetic algorithm, which successfully converted the multiple targets optimization control to single target one, opening up a new way to solve the optimal control problem in the case of multiple working conditions, multiple targets, multiple variables and multiple restrictions.In regard to diagnosis of abnormal combustion, the methods of wavelet-lifting transform and empirical mode decomposition are firstly introduced and used for this purpose, which can provide more useful information for early diagnosis of preignition. The comparison between Harr wavelet transform and wavelet-lifting transform has shown that both results are similar, and both can precisely reflect the characteristics of the original signals, however the wavelet-lifting transform has some advantages over Harr wavelet transform such as the independence on Fourier transform, simplicity of structure and algorithm and fast calculation without additional storage costs etc. Since the method of EMD , compared with harmonic-based wavelet transform, is more intuitive and adaptive, the EMD method is used in this paper for comparative analysis of the preignition signals and normal combustion signals. Test results show that EMD can conveniently display the pressure signal characteristics in different resolutions, thus can more accurately reflect the characteristics of the original signals compared with wavelet transformation, which is valuable for early diagnosis and recognition of preignition.With regard to hydrogen engine test, a Lab VIEW-based software tool is designed, which can conveniently be used for monitoring, analysis and processing of the hydrogen-fueled engine sensor signals with graphical display and storage functions that are not available with the conventional test systems, thus is of practical value.