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In this paper, the effects of direct water injection (WI) on characteristics of combustion and emission for a hydrogen (H2)-fueled spark ignition (SI) engine were experimentally investigated. The experiments conducted under different amounts of water injection (AWI) and varied water injection timing (WIT). The experimental results showed that in-cylinder pressure decreased, indicated thermal efficiency (ITE) increased, and the flame development (CA0-10) and propagation (CA10-90) periods prolonged when AWI raised. When AIW grew to 4.5 mg/cycle, Nitrogen oxides (NOx) expelled from the original engine decreased by 53.7% when excess air ratio (λ) was 1.15. Early WIT had positive effects on the reduction of NOx emissions. When WIT retarded, in-cylinder pressure increased, ITE decreased and CA0-10 and CA10-90 shortened, NOx emissions rapidly increased.

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.

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.

The general purpose of this work is to examine the adsorption characteristics of activated carbon materials for reducing HC emissions from the gasoline engine under starting conditions. Three kinds of activated carbon materials were selected to adsorb HC emissions within 80 s from the onset of starting at different coolant temperatures of 25, 35, 45 and 55 °C, respectively. The experimental results showed that the total HC adsorption rates of activated carbon materials declined with the increase of coolant temperatures. The total HC adsorption rates of activated carbon honeycomb, foams and fibers were 68.6%, 66.1% and 53.5% under the coolant temperature of 25 °C. The early desorption was found for activated carbon foams, which was getting severe with the increase of coolant temperatures. Then, the adsorption performance of activated carbon honeycomb was further investigated at the repeated engine starting conditions. Under the repeated starting conditions, the total HC adsorption rates of activated carbon honeycomb decreased with the increase of adsorption times in the test. The total HC adsorption efficiencies of the first three times under repeated starting conditions were 76.4%, 63.7% and 54.0%, respectively. The results showed that the adsorption processes could be divided into three phases based on the adsorption characteristics, which were rapid adsorption phase, interim adsorption phase and slow adsorption phase, respectively.

In this paper, the effects of direct water injection (WI) on characteristics of combustion and emissions for a hydrogen (H2)-fueled spark ignition (SI) engine were experimentally investigated. The experiments were conducted under different excess air ratios (λ) and ignition timing (IT). In each test, the water to air ratio (α) was varied, and the results were compared with baseline data without WI. The experimental results showed that in-cylinder pressure decreased, indicated thermal efficiency increased, and the flame development and propagation periods prolonged when WI was used. When α increased to 1.87%, NOx emissions expelled from the original engine separately decreased by 36.9% and 55.4% when IT were 5°CA BTDC and 15°CA BTDC at λ of 1.15.

Due to the elongated shape of the combustion chamber and strong one-way flow characteristic, changing the location of enhanced combustion is an effective means to ameliorate the indicated efficiency of the Wankel engine. For this purpose, strengthening combustion can happen by allocating spark-energy in the desired location along with a favorable ignition environment. In this study, three-dimensional CFD simulations were implemented and the numerical results were compared with existing measured data, in which ignition environment variations were achieved by hydrogen enrichment within the intake manifold of a spark-ignition Wankel engine. Based on CONVERGE code with the SAGE detailed chemistry solver, the twin-plug engine model was then used to assess the location of strengthened combustion employing a spark-energy allocation from the perspective of species evolution, combustion characteristics, and emissions formation. The results indicate that enhancing spark-energy at the leading side of the rotor chamber has an overall higher burned volume rate and faster species evolution due to the later connection of two burning sources prior to quenching. Increasing the hydrogen content in the ignition environment causes richer active radicals and higher turbulence, ultimately promoting flame propagation and combustion intensity. A larger T-plug spark-energy decreases the indicated mean effective pressure, heat release rate, and thermal efficiency because of the intensified wall heat flux and the lower mass burning rate at the leading side. There is no doubt that the introduction of hydrogen enrichment presents a positive effect on both thermal efficiency and specific fuel consumption at the price of a slighter increase of nitrogen oxide formation due to higher mass fraction of high-temperature regions. It is recommended that enhancing local mass burning rate in the leading part of the rotor chamber under the hydrogen-enriched ignition environment can provide a great potential in the quest towards high-efficiency Wankel rotary engine.