Search

Hydrogen-fueled Wankel rotary engine, with few available research currently, has excellent power and emission characteristics, however, with lower efficiency. With increasing attention to low-carbon emission, it is of great significance to explore methods to improve the efficiency of hydrogen-fueled Wankel rotary engines. This work aims to study the effect of qualitative control coupling variable engine speeds at the wide-open throttle on the power control. The comparative effect of qualitative control coupling engine speeds from 1000 r/min to 1500 r/min under the wide-open throttle and quantitative control at 1500 r/min on the combustion and emission characteristic of hydrogen-fueled Wankel rotary engine is investigated. The results show that compared with quantitative control, qualitative control coupling variable engine speed can achieve excellent performance. The brake thermal efficiency can be maximally increased by 43.5%, an absolute increase of 6.22%, as well the volumetric efficiency with a maximal 105% improvement. The thermal load and risk of knock can be greatly reduced. Moreover, NO emission also can be reduced by more than an order of magnitude or even by zero. Although there is an increase in cyclic variation, the value is no more than 4%. In addition, qualitative control coupling variable engine speed allows flexible matching of appropriate engine speed and excess air ratio based on the actual requirements of efficiency, stability, durability and emission. • The power control method of the hydrogen Wankel rotary engine is investigated. • Qualitative control achieves better engine performance than quantitative control. • Qualitative control coupling engine speed meets the power and high-efficiency demand. • Lower thermal load, knock tendency and NO emission can be obtained. • Much high excess air ratio isn't recommended due to high cyclic variation. [ABSTRACT FROM AUTHOR]

Hydrogen-fueled Wankel rotary engine, with few available research currently, has excellent power and emission characteristics, however, with lower efficiency. With increasing attention to low-carbon emission, it is of great significance to explore methods to improve the efficiency of hydrogen-fueled Wankel rotary engines. This work aims to study the effect of qualitative control coupling variable engine speeds at the wide-open throttle on the power control. The comparative effect of qualitative control coupling engine speeds from 1000 r/min to 1500 r/min under the wide-open throttle and quantitative control at 1500 r/min on the combustion and emission characteristic of hydrogen-fueled Wankel rotary engine is investigated. The results show that compared with quantitative control, qualitative control coupling variable engine speed can achieve excellent performance. The brake thermal efficiency can be maximally increased by 43.5%, an absolute increase of 6.22%, as well the volumetric efficiency with a maximal 105% improvement. The thermal load and risk of knock can be greatly reduced. Moreover, NO emission also can be reduced by more than an order of magnitude or even by zero. Although there is an increase in cyclic variation, the value is no more than 4%. In addition, qualitative control coupling variable engine speed allows flexible matching of appropriate engine speed and excess air ratio based on the actual requirements of efficiency, stability, durability and emission. • The power control method of the hydrogen Wankel rotary engine is investigated. • Qualitative control achieves better engine performance than quantitative control. • Qualitative control coupling engine speed meets the power and high-efficiency demand. • Lower thermal load, knock tendency and NO emission can be obtained. • Much high excess air ratio isn't recommended due to high cyclic variation. [ABSTRACT FROM AUTHOR]

Wankel rotary engine (WRE) is welcomed due to its high power density and compact layout and is criticized due to its low efficiency and poor emission. To develop low-carbon emission and high-efficiency WRE, the present work discusses the potential of hydrogen/methane dual-fueled WRE with varied fuel components. The test was conducted at 1500 r/min, 80 kPa manifold absolute pressure and stoichiometric ratio. The results indicate that compared with pure hydrogen or pure methane WRE, hydrogen/methane dual-fueled WRE can achieve higher thermal efficiency and output power, the maximum values of which are 30.7% and 12.4 kW under test conditions, respectively. Besides, it also has satisfactory NO, CO2 and HC emissions. In particular, there is a linear relationship between NO emission and methane volumetric percentage with a 0.9949 determination coefficient in logarithmic coordinates, which means that the NO emission can be easily predicted. In addition, the cyclic variation is acceptable at maximum-efficiency CH4% and the knock can be almost eliminated in hydrogen-methane dual-fueled WRE when the volume ratio of methane exceeds about 40%. In general, WRE is recommended to be fueled by a mixture of hydrogen and methane with a high methane volumetric percentage. • Discussion on the potential of hydrogen/methane dual-fueled Wankel rotary engines. • Dual fuel is better than single fuel in terms of power, efficiency, emission, etc. • There is a linear relationship between NO and CH4% in logarithmic coordinates. • Knock can be almost eliminated when the CH4% exceeds about 40%. [ABSTRACT FROM AUTHOR]

• The behavior of CO2 in a hydrogen Wankel rotary engine is investigated. • CO2 can effectively improve the dynamics, economics and emission characteristics. • CO2 has significant effects on the heat release process. • Adding CO2 into intake can be considered an excellent knock suppression method. • CO2 has a better effect on the prevention of knock than N2. To prevent global warming, vigorously developing hydrogen energy has become one of research focuses of various countries and regions in recent years. Hydrogen-fueled engines have been proven to be a potential alternative to current fossil-fueled engines. Among various engines, Wankel rotary engine (WRE) is praised for its simple structure and excellent dynamic characteristics, which can greatly compensate for the low specific-volume heat value of hydrogen. However, hydrogen-fueled WRE suffers from low efficiency, high NOx emission and severe knock. For methanol-reforming hydrogen-fueled ICEs, CO2 as the by-product can be used as variant-cooled-EGR to improve ICEs performance and prevent abnormal combustion. Therefore, this work researches the behavior of CO2 on the hydrogen-fueled WRE. The work is conducted at 1500 r/min and wide-open throttle. The results show that CO2 has a significant influence on the heat release process of hydrogen-fueled WRE. Due to this influence, when the volume fraction of CO2 in intake (CO2%) is increased from 0 to 19.28%, the brake thermal efficiency can be improved by 8% with a 7% decline in power output. The NO emission has two orders of magnitude of reduction with increasing CO2% from 0 to 19.28%.. In addition, compared with cooled-EGR, CO2 has a better effect on knock suppression. If methanol-reforming to produce hydrogen becomes the mainstream of on-board hydrogen production in the future, the application of CO2 is of great significance. [ABSTRACT FROM AUTHOR]