Abstract
Social problems such as environmental pollution and limited crude oil resources are great challenges that have become major concerns in the world, so scientists and researchers are investing significant time and effort in developing new eco-friendly technologies that can be applied in the automotive industry. A hybrid pneumatic power system (HPPS), that replaces the battery’s electric-chemical energy with flow work, recycles the exhaust-gas energy of the internal combustion engine (ICE), and makes the ICE operate at its sweet spot of maximum efficiency, could be viewed as a promising solution to increase the system thermal efficiency and greatly improve exhaust emissions. However, in this system, the flow energy merger of both the high-pressure compressed airflow and the hightemperature exhaust-gas flow is significantly dependent on merging capability of energy merger pipe. If the compressed airflow pressure (Pair) increases significantly, the static pressure at the merging region of the energy merger pipe will become too high. This will prevent the exhaust-gas flowing out and then annoy ICE’s operation, thus the exhaust-gas recycling capability and the system thermal efficiency will significantly reduce. In order to improve the aforementioned deficiencies, an innovative energy merger pipe optimally designed and operated according to the Venturi principle, which effectively converge both the compressed airflow and the exhaust-gas flow, is proposed. The paper present investigation results concerning the effects of cross-sectional area at the merging region of the energy merger pipe and high-pressure compressed airflow rate on flow energy merger. The results showed that exhaust-gas recycling and flow energy merger are significantly dependent on the suitable adjustment of the open angle (Aair) of the air storage tank’s throttle valve, and contraction of cross-sectional area (CSA) at the merging region of the energy merger pipe for the change in Pair. The optimum conditions for high exhaust-gas recycling efficiency and best merging process are the Aair around 25−100% and the CSA around 5−50% in full study ranges of Pair. Under these conditions, the exhaust-gas recycling efficiency reached approximately 75−80%, therefore, a vehicle equipped with an HPPS can achieve thermal efficiency that is approximately 40% higher than that of conventional vehicles.
Keywords: Hybrid pneumatic power system, Exhaust-gas recycling, Flow energy merger, System thermal efficiency