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The structure chamber of rotary engine is irregular compared with traditional reciprocating engines. Pure n -butanol rotary engine normally encounters partial burning and even misfire at idling and lean conditions. Comparatively, hydrogen supplement can ameliorate performance of original engine. In this paper, experimentation of a rotary engine fueled with pure n -butanol and hydrogen/ n -butanol blends at idling and different excess air ratios was conducted. Experimental results manifested that hydrogen addition effectively decreased the engine instability and fuel energy flow rate. To be specific, fuel energy flow rate at the excess air ratio of 1.05 was reduced from 23.63 MJ/h to 21.26 MJ/h when 3% hydrogen was added. Combustion duration was lowered after introducing hydrogen. Maximum chamber temperature was heightened after hydrogen addition. HC and CO emissions were reduced when 3% hydrogen was added. NOx emissions were reduced when the mixture was leaned out. [ABSTRACT FROM AUTHOR]

Ignition timing is an important parameter for spark-ignited engine. Hydrogen replenishment effectively improves the performance of engine. This paper experimentally investigated the impact of ignition timing on performance of a hydrogen-enriched n-butanol rotary engine. For this purpose, a rotary engine installed with a dual-fuel (hydrogen and n-butanol) port injection system was specially developed. An electronic management module was solely developed to control the fuel injection, excess air ratio and hydrogen proportion. In this experiment, the engine was run at 4000 rpm, an intake pressure of 35 kPa and an excess air ratio of 1.10. Hydrogen volume ratio was set at 0% and 3%, respectively. When hydrogen fraction was changed, n-butanol injection was also adjusted to make excess air ratio be 1.10. For 0% and 3% hydrogen addition, ignition timing was severally varied from 35 to 51°CA BTDC and 29 to 45°CA BTDC with an interval of 2°CA. Experimental results showed that with the increase of ignition advance, both peak chamber pressure and temperature were increased, brake thermal efficiency was initially ascended and then declined. Flame development period was prolonged whereas flame propagation period was shortened as ignition advance increase. Cyclic variation was initially weakened and then deteriorated by advancing ignition. HC and NOx emissions were reduced after retarding ignition timing. Ignition timing had little influence on CO emission. [ABSTRACT FROM AUTHOR]

Rotary engine generally sustains poor fuel economy and emissions performance at idle condition. Hydrogen has excellent physicochemical properties that can serve as an enhancer to improve the performance of the original engine. In this paper, a modified rotary engine equipped with dual fuel (hydrogen and n-butanol) port injection system and electronic ignition module was developed to explore the influence of hydrogen supplement on enhancing the idle performance of n-butanol rotary engine. In this study, the engine was run at the idle and stoichiometric with the original spark timing. Hydrogen volume percentage in the total intake was gradually increased from 0% to 7.9% by adjusting the fuel flow rate of n-butanol. The experimental results indicated that the engine instability and fuel energy flow rate were both reduced by enlarging the hydrogen supplying level. Combustion periods were shortened thanks to the enrichment of hydrogen. The peak chamber temperature was heightened as hydrogen fraction increased due to the improved combustion. HC and CO emissions were severally reduced by 50.4% and 85.8% when the hydrogen volume percentage was raised from 0% to 7.9%. However, NOx emissions were mildly increased because of the raised chamber temperature by increasing hydrogen fraction. [ABSTRACT FROM AUTHOR]

The present paper introduced an experiment survey focusing on exploring the impact of hydrogen enrichment on improving the lean-burn performance of an n-butanol rotary engine. During the test, the engine speed and intake pressure were roughly set at 4000 rpm and 35 kPa, respectively. A constant spark advance of 45 °CA was adopted through the test. Hydrogen volumetric fraction of the total intake was severally kept at 0% and 3%. The testing results manifested that the brake thermal efficiency and peak chamber temperature were heightened with hydrogen addition. Besides, the ignition delay and rapid combustion duration were both reduced with the hydrogen additive. Engine running stability gained an improvement by hydrogen supplement. Moreover, HC and CO emissions from the original n-butanol rotary engine were reduced after hydrogen adding. NOx emissions were increased with hydrogen enrichment while reduced with the increase of excess air ratio. This indicated that NOx emissions from both the n-butanol and hydrogen-blended n-butanol rotary engines could be reduced by lean combustion strategies. [ABSTRACT FROM AUTHOR]

Rotary engine has flat chamber and longs for fuel with high flame speed and small quenching distance. Hydrogen has many excellent characteristics that are suitable for the rotary engine. In this paper, the performance of a rotary engine fueled with pure hydrogen at different excess air ratios was experimentally investigated. The investigation was carried out on a single-rotor hydrogen-fueled rotary engine equipped with port fuel injection system. An online electronic control module was used to govern the hydrogen injection duration and excess air ratio. In this study, the engine was operating at the idle speed of 3000 rpm and different excess air ratios varied from 0.993 to 1.283. The test results demonstrated that the fuel energy flow rate of the hydrogen rotary engine and engine stability were reduced with the increase of excess air ratio. When the excess air ratio increased from 0.993 to 1.283, the hydrogen energy flow rate was decreased from 14.91 to 11.55 MJ/h. Both the flame development and propagation periods were increased with excess air ratio. CO emission was negligible, but HC, CO 2 and NOx emissions were still detected due to the evaporation and possible burning of the lubrication-used gasoline, and oxidation reaction of nitrogen of the intake air. [ABSTRACT FROM AUTHOR]

The combustion process within the cylinder directly influences the thermal efficiency and performance of the engines. As for the rotary engine, the long-narrow combustion chamber prevents the mixture from fully burning, which worsens the performance of the rotary engine. As a fuel with excellent properties, hydrogen can improve the combustion of the original engine. In this paper, improvements in combustion of a gasoline rotary engine by hydrogen supplement under different operating conditions were experimentally investigated. The experiment was conducted on a modified hydrogen-gasoline dual-fuel rotary engine equipped with an electronically-controlled fuel injection system. An electronic control module was specially made to command the fuel injection, excess air ratio and hydrogen volumetric fraction. Integral heat release fraction (IHRF) was employed to evaluate the combustion of the tested engine. The tested engine was first run at the idle speed of 2400 rpm and then operated at 4500 rpm to investigate the combustion of the hydrogen-blended gasoline rotary engine under different hydrogen volume fractions, excess air ratios and spark timings. The testing results demonstrated that the combustion of the gasoline rotary engine were all improved when the hydrogen was blended into the chamber under all tested conditions. [ABSTRACT FROM AUTHOR]

In this paper, a rotary engine equipped with an n-butanol and hydrogen port-injection system was developed to investigate the combustion and emissions characteristics of a hydrogen-blended n-butanol rotary engine at part load and stoichiometric conditions. A self-developed hybrid electronic control unit was adopted to adjust the injection durations of n-butanol and hydrogen. The rotary engine was run under the conditions of 4000 rpm, a manifold absolute pressure of 35 kPa and a fixed spark timing of 45 °CA before the top dead center during the whole testing operation. The hydrogen volumetric fraction in the total intake was varied from 0% to 6.30%. The test results manifested that the brake thermal efficiency and chamber temperature were simultaneously increased with hydrogen addition. The hydrogen supplement obviously shortened flame development and propagation periods. Both chamber pressure integral heat release fraction versus crank angle were increased when the hydrogen fraction was enhanced. HC emissions were reduced by 54.5% when hydrogen volume fraction was raised from 0% to 6.30%, CO and CO 2 emissions were also reduced after increasing hydrogen blending fraction. NOx emissions were mildly elevated due to the improved chamber temperature. [ABSTRACT FROM AUTHOR]

In the present paper, the cyclic variations of a hydrogen-blended gasoline rotary engine operated under various conditions were experimentally investigated. The experiments were carried out on a modified hydrogen-gasoline dual-fuel rotary engine equipped with an electronically-controlled fuel injection system. An electronic control module was specially made to command the fuel injection, excess air ratio and hydrogen volumetric fraction. The tested engine was first run at idle condition with a speed of 2400 rpm and then operated at 4500 rpm to investigate the cyclic variations of a hydrogen-enriched gasoline rotary engine under different hydrogen volumetric percentages in the total intake, excess air ratios and spark timings. The experimental results demonstrated that the coefficient of variations (in peak pressure, engine speed, flame development period and flame propagation period) of the gasoline rotary engine were distinctly decreased with the increase of hydrogen volume fraction under all the tested conditions. In particular, at idle and stoichiometric conditions, the coefficient of variation in CA0-10 and CA10-90 were reduced from 9.25% to 5.01%, 15.40% to 8.70%, respectively. [ABSTRACT FROM AUTHOR]

This paper aimed to study the effect of spark timing on performance of a hydrogen-gasoline dual-fuel rotary engine. For this aim, a modified rotary engine equipped with a dual-fuel port injection system was developed. An electronic management module (ECM) was specially made to command the fuel injection, excess air ratio and hydrogen volumetric fraction. In this study, the engine was operated at 4500 rpm with a manifold absolute pressure (MAP) of 35 kPa. Hydrogen volumetric percentage of total intake was kept at 0%, 3% and 6%, severally. When the hydrogen volumetric percentage was changed, the gasoline fraction was also adjusted to keep the mixture at the stoichiometric. For a specified hydrogen volumetric fraction, the ignition timing was varied from 24 to 42 °CA BTDC (before top dead center) with a fixed interval of 2 °CA. Experimental results showed that for a specific hydrogen volumetric percentage, the peak combustion pressure and chamber temperature were increased, brake thermal efficiency was first increased and then decreased with the increase of spark advance. Advancing spark timing caused the increased flame development period, the decreased flame propagation period and exhaust temperature. Cyclic variation was initially weaken and then deteriorated after raising spark advance. HC and NOx emissions were reduced after retarding spark timing. Spark timing had little effect on CO emission. [ABSTRACT FROM AUTHOR]

This paper presented an experimental study about the idle performance of a rotary engine fueled with hydrogen and gasoline blends. The idle speed was reduced from original 2400 to 2300 and 2200 rpm, and hydrogen energy percentage ( β H2 ) was varied from 0% to 35.0%. Test results showed that cyclic variation was raised with the decrease of idle speed whereas reduced with the increase of β H2 . Both decreasing idle speed and increasing β H2 were effective on reducing engine fuel consumption. Total fuel energy flow rate was effectively dropped from 22.4 MJ/h under “2400 rpm and β H2 = 0%” to 20.01 MJ/h under “2200 rpm and β H2 = 35.0%”. Combustion duration was reduced through increasing β H2 . HC and CO emissions were dropped with the increase of β H2 , but increased after reducing idle speed. CO 2 emission was decreased after reducing idle speed and adding hydrogen. [ABSTRACT FROM AUTHOR]

Because of the limit of properties of gasoline and irregular design of chamber, the pure gasoline rotary engine generally encounters partial burning, increased noxious emissions or even misfire at lean conditions. This situation could be deteriorated at idle because of the high variation in the intake charge and low combustion temperature. Hydrogen addition is proved to remit the deterioration of performance of sparked-ignited (SI) engines at idle and lean conditions. This paper conducted an experiment on a modified rotary engine equipped with gasoline and hydrogen port-injection systems to explore the performance of a hydrogen–gasoline rotary engine (HGRE) at idle and lean conditions. An electronic management unit (EMU) was invented to manage spark and fuel injection. Excess air ratio ( λ ) and hydrogen volumetric fraction in the total intake ( α H 2 ) were also governed through the EMU. For this study, the HGRE was operating at idle and α H 2 was kept at 0% and 3%, respectively. For a specific α H 2 , gasoline flow rate was reduced to make the HGRE run at desired λ . Results indicated that engine fluctuation and fuel energy flow rate were both decreased after hydrogen addition. Combustion duration was cut down and central heat release point was advanced after hydrogen addition. Peak chamber temperature ( T max ), pressure and heat release were enhanced after hydrogen blending. HC, CO and CO 2 emissions were simultaneously reduced because of hydrogen enrichment. Specifically, at λ = 1.00, HC, CO and CO 2 emissions were respectively reduced from 42,411 to 26,316 ppm, 1.86 to 0.78% and 9.96 to 8.58% when 3% hydrogen was added. [ABSTRACT FROM AUTHOR]

Because of the unusual structure chamber compared with traditional engines, gasoline rotary engine always encounters partial burning and increased noxious emissions at the idle. Hydrogen-addition could enhance the characteristics of combustion and emissions of sparked-ignited engines at idle. A modified gasoline rotary engine with electronic spark control and fuel (gasoline and hydrogen) port-injection system was developed to study the impact of hydrogen-addition on idle performance of a gasoline rotary engine. A hybrid electronic control unit was invented to manage the spark, fuel injection, hydrogen volume fraction of the total intake and overall excess air ratio. In this study, the engine was operating at the idle speed of 2400 rpm and stoichiometric conditions. The hydrogen volume fraction was gradually varied from 0% to 6.8%. Results showed that the coefficient of variation in speed and fuel energy flow rate were both decreased after the hydrogen-addition. Flame development and propagation periods were shortened owning to hydrogen-addition. The peak chamber temperature was enhanced after the hydrogen-addition due to the high adiabatic flame temperature of hydrogen. Cooling loss was dropped when hydrogen was added into gasoline. HC, CO and CO 2 emissions were reduced by 79.4%, 86.0% and 25.9% when hydrogen volume fraction were raised from 0% to 6.8%. [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]

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 (HWRE) as a promising power device overcomes some of the drawbacks of the hydrogen-fueled reciprocating engine. However, its elongated combustion chamber makes it prone to knock, and little research has been done in this area. Hence, to understand the knock characteristics of HWRE, the present work focus on parameters of HWRE knock at 2000r/min, an excess air ratio of 1.2 and an ignition timing of −7°CA ATDC. The main results are as follows: As with knock intensity, knock duration and maximum pressure rising rate also can characterize the knock of HWRE because of the logarithmic or linear relationship among three parameters. For the knock intensity, two parameters are needed to precisely characterize the HWRE knock, while only one parameter is needed for the knock duration and the maximum pressure rising rate. Considering the computing cost, the maximum pressure rising rate is better than others. The knock intensity has a significant influence on the timed sequence of peak knock pressure and peak in-cylinder pressure. Besides, the mechanism of backfire caused by the knock of HWRE is different from that of the hydrogen-fueled reciprocating piston engine, which results from the inter-cylinder flame leakage. • The knock characteristic of hydrogen-fueled Wankel rotary engine is analyzed. • There are mathematical relationships among parameters characterizing knock. • Maximum pressure rise rate is a better metric to characterize WRE knock. • Misfire caused by knock in WRE is different from reciprocating piston engines. [ABSTRACT FROM AUTHOR]

Abstract This paper analyzed low emissions on a hydrogen-fueled spark ignition (SI) engine at the cold start period under rich combustion through ignition timing (IT) control. Cold start characteristics of hydrogen-fueled engine were investigated experimentally. The study was performed under different IT. The results demonstrated that when excess air ratio (λ) was 0.7 and IT varied from 25 °CA BTDC to 10 °CA ATDC, the peak cylinder pressure of the first cycle and the successful start time (SST) of hydrogen engine first increased and then decreased with the retard of IT. At 15 °CA BTDC, the hydrogen engine gained the shortest SST and the highest cylinder pressure in the first cycle. Flame development period (CA0-10) first shortened and then lengthened, and flame propagation period (CA10-90) prolonged when IT gradually retarded. The average NOx emissions efficiently reduced by 90.2%, HC and CO emissions caused by the evaporated lubricant oil reduced individually by 33.8% and 19.7% in the first 6 s during the cold start process with the retard of IT. Especially when IT delayed from 25 °CA BTDC to 15 °CA BTDC, the effect of IT on HC emissions was significant. Highlights • A hydrogen-fueled engine with low emissions in the cold start was realized. • Engine emission performances under different ignition timing were studied. • The engine gained the fastest successful start time at 15°CA BTDC. • NOx, HC and CO emissions within the first 6 s all decreased. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the effects of excess air ratios (λ) on nitric oxide (NOx) emissions of a hydrogen-fueled spark ignition engine in the cold start period are studied. Cold start characteristics of hydrogen-fueled engine were investigated experimentally. The study was performed under different λ. The experimental results showed that, when λ declined from 1.6 to 0.7, the peak engine speed within the first 6 s increased and in-cylinder pressure in the first cycle raised firstly then decreased slightly while the flame development and propagation periods shortened, and the exhaust temperature at the 6th s raised from 329 K to 355 K. In addition, NOx emissions obviously decreased, whereas hydrocarbon (HC) and carbon monoxide (CO) emissions caused by the evaporated lubricant oil increased by decreasing λ within the first 6 s. Highlights • A hydrogen-fueled engine with low emissions in the cold start was realized. • Engine combustion and emission performances have been studied in this paper. • The flame development and propagation periods were shortened. • NOx emissions were decreased, HC and CO emissions were increased. [ABSTRACT FROM AUTHOR]

The performance of a hydrogen-blended gasoline direct injection engine under various second gasoline direct injection timings is investigated on a modified commercial gasoline direct injection engine. All tests are carried out at a typically congested city-driving condition using lean burn and split gasoline direct injection modes. Results show that under pure gasoline fuel supply mode, brake mean effective pressure, brake thermal efficiency, flame development period, flame propagation period, and maximum in-cylinder pressure vary obviously with various second gasoline direct injection timings and the best second gasoline direct injection timing for engine performance is 130 CAD before top dead center. Blending hydrogen could weaken variations of engine performance related parameters caused by changing second gasoline direct injection timing compared to that under pure gasoline mode. Besides, blending hydrogen could also reduce flame development and propagation periods, and enhance the maximum in-cylinder pressure under the same second gasoline direct injection timing. With hydrogen addition, the coefficient of variations in indicated mean effective pressure drops to less than 1.1%, but second gasoline direct injection timing has no obvious effect on it any more. Besides, adding hydrogen could reduce hydrocarbon and carbon monoxide emissions by 33.10% and 18.28% in average, respectively. Particulate number has a reduction of order of magnitudes (∼10 8 to ∼10 6  n/cm 3 in average). With hydrogen addition, nitrogen oxides emissions increase. [ABSTRACT FROM AUTHOR]