Experimental And Numerical Investigation On Performance Of The On-Board Alkaline Hydrogen Generator

Concerning the severe energy and environmental issues, reducing fuel consumption and toxic emissions has become an inevitable development trend for vehicle dynamic systems in the future. The hydrogen has many good physicochemical properties which enables the gasoline engine to gain higher thermal efficiency and lower toxic emissions with the hydrogen enrichment. This makes the addition of hydrogen becomes a feasible way for improving the performance of present gasoline engines. However, the massive storage of hydrogen in vehicles brings potential safety problems. Besides, the limited hydrogen infrastructure distribution also blocks the refilling of hydrogen of the hydrogen-blended gasoline engines. The onboard hydrogen generator could produce hydrogen during driving, which is helpful for solving above problems. The alkaline hydrogen generator produces hydrogen by consuming the electrical energy from the electric generator in the engines. This means that the hydrogen production rate and efficiency directly influence the overall performance of the hydrogen-blended engine powered vehicles. Therefore, this paper studied the effect of metal ions and additive addition on performance of the on-board alkaline hydrogen generator by experimental investigations. Moreover, the effect of the optimized on-board alkaline hydrogen generator on economy performance of the hydrogen-blended gasoline engine-powered vehicle is also studied through numerical simulation.The paper studied influencing factors of the on-board alkaline hydrogen generator such as electrolytic efficiency, hydrogen producing velocity and efficiency, designing and building hydrogen generator testing bench. The test bench consists of an electrolytic tank, a controlling and measuring system, and a cooling and drying system, which controls electrolyte concentration, electrolytic temperature, electrolytic pressure and electrolytic current.In view of the low efficiency of on-board alkaline hydrogen generator due to adding metal ions in water, effects of different concentrations of Zn²⁺, Fe³⁺ and Cu²⁺ on addition performance of the on-board alkaline hydrogen generator were tested on the hydrogen generator testing bench. The experiment was carried out at the electrolytic current of 30 A, the initial temperature of 19.7 ℃ and the pressure of 0.1 MPa. The effect of adding 50 m L metal ions liquor to the 2 L KOH liquor which has a KOH mass fraction of 30% was investigated and compared with the pure KOH liquor electrolyzing. In view of the low efficiency of on-board alkaline hydrogen generator in the hydrogen-blended gasoline engine-powered vehicle, effects of additive addition on performance of the on-board alkaline hydrogen generator with different mass fractions of KOH liquor were tested on hydrogen generator test bench. In this paper, the experiment was carried out at the conditions of electrolytic current of 40 A, the initial temperature of 23.7 ℃ and the pressure of 0.1 MPa. The mass fractions of KOH were kept at 20%, 30% and 40% in the KOH liquor, respectively. For each KOH mass fraction, the effect of adding 0.3g K₂Cr₂O₇ on performance of the on-board alkaline hydrogen generator was investigated. Through optimizing performance of the on-board alkaline hydrogen generator by adding additives, the paper studied the effect of the optimized on-board alkaline hydrogen generator on the global fuel economy of hydrogen-blended gasoline engine-powered vehicle by using AVL Cruise.The experimental results of the effect of metal ions on performance of the on-board alkaline hydrogen generator showed that the electrolytic temperature was increased, the electrolytic voltage was reduced, and the hydrogen producing velocity and efficiency were increased by adding metal ions. The electrolytic voltage was increased which also decreased more gently with the increased of time. Meanwhile, the hydrogen producing velocity and efficiency were reduced and slightly increased with the increase of Zn²⁺, Fe³⁺ and Cu²⁺ concentrations. The experimental results of the effect of additive addition on performance of the on-board alkaline hydrogen generator showed that adding K₂Cr₂O₇ into 20%, 30% and 40% KOH liquor respectively reduced electrolytic voltages by 0.16V、0.19 V and 0.09 V, the increased hydrogen producing efficiencies of 2.14%, 2.78% and 1.46%, and the increased hydrogen producing efficiency ratios of 5.23%、6.71% and 3.47%, respectively. Adding K₂Cr₂O₇ into the 30% KOH liquor contributed to the best hydrogen producing efficiency. The numerical results of the effect of the optimized on-board alkaline hydrogen generator on fuel economy of the hydrogen-blended gasoline engine-powered vehicle showed that optimized on-board alkaline hydrogen generator consumed less gasoline than original on-board alkaline hydrogen generator, improving economy performance of the hydrogen-blended gasoline engine-powered vehicle.