Effect of LP-EGR on the Emission Characteristics of GDI Engine

Exhaust gas recirculation (EGR) can improve the fuel economy of gasoline direct-injection (GDI) engines, but at the same time it will have a significant impact on emissions. In this paper, the effects of low-pressure exhaust gas recirculation (LP-EGR) and its rate on the main gaseous and particulate emission characteristic of a GDI engine were investigated. The results showed that the particle size distribution of the GDI engine presented bimodal peaks in nucleation and accumulation mode, and the nucleation mode particles comprised the vast majority of the total particles. The effect of LP-EGR on emissions depended on the engine conditions. At low and medium speed, the particle emissions increased with the increase in the EGR rate, while at high speed, a reduction in the particle emission was observed. When the engine operated in full load condition, an increase in the EGR rate reduced the particle number (PN) concentration significantly, but increased the particle mass (PM) concentration. In terms of the gaseous emission, the EGR could reduce as much as 80% of the NOx emission; however, the total hydrocarbons (THC) emission presented an increased trend, and the maximum increase reached 23.5%. At low and medium loads, the EGR could reduce the CO emission, but at high load, the CO emission worsened with the EGR.

The Effect of Hydrogen Enrichment on The Exhaust Emission Characteristic in A Spark Ignition Engine Fueled by Gasoline-Bioethanol Blends

Bioethanol characteristics can be used as an alternative fuel to spark-ignition (SI) engines to reduce emissions. This experiment evaluates the production of emissions for SI engines using hydrogen enrichment in the gasoline-bioethanol fuel blends. The fraction of bioethanol fuel blend was added to the gasoline fuel of 10% by volume and hydrogen fuel produced by the electrolysis process with a dry cell electrolyzer. The NaOH was used as an electrolyte which is dissolved in water of 5% by a mass fraction. The test is conducted using a single-cylinder 155cc gasoline engine with sensors and an interface connected to a computer to control loading and record all sensor variables in real-time. Hydrogen produced from the electrolysis reactor is injected through the intake manifold using two injectors, hydrogen injected simultaneously at a specific time with a gasoline-bioethanol fuel. The test was conducted with variations of engine speeds. The emission product of ethanol--H2 (BE10+H2) was an excellent candidate as a new alternative of fuel solution in the future. The engasolinerichment of hydrogen increased the flame speed and generated a stable combustion reaction. The hydrogen enrichment produced CO2 emission due to the unavailability of carbon content in hydrogen fuel. As a result, the C/H ratio is lower than for mixed fuels.

Improvement of performance and emission characteristic of waste plastic pyrolytic oil blended diesel fuel in variable compression diesel engine using graphene nano additive

A growing interest in extracting oil from waste plastics has converged with rising demand for petro-fuels and issues in disposing of waste plastics. The characteristics of pyrolytic oil produced from plastic wastes were compared to diesel and found to be sufficiently similar to be used as an alternative fuel. In this paper, an attempt has been taken to enhance the combustion properties of waste plastic oil blended diesel following dispersion of nanographene particles. The performance and emissions of a single-cylinder direct injection compression ignition engine with compression ratios ranging from 16:1 to 18:1 was evaluated using 50, 70, and 100 ppm by using 50, 70, and 100 ppm by mass of nanographene dispersed in 20% waste plastic oil blended diesel without any engine modification. By supercharging the engine with nanographene at various compression ratios, the performance of a 20% plastic oil blended diesel is compared to that of a neat diesel. The brake thermal efficiency of 20% plastic oil blended 100 ppm graphene dispersed diesel fuel increased by 1.16% at a compression ratio of 17:1 when compared to diesel. The CO, HC, NOx emissions also dropped significantly by adding 100 ppm nanographene to WPO as compared to the other combinations of fuels.

Reductive Dehalogenation – Challenges of Perfluorinated Organics

: In this mini-review, the problem of effective elimination of perfluorinated organic micropollutants from aquatic environment has been touched. The extraordinary chemical stability of common perfluorinated organic surfactants results in unsatisfactory efficiency of conventional treatment processes, which opens perspectives for photocatalytic methods - especially for reductive-dehalogenation. To tackle this challenge by photocatalysis one have to be aware of objective, physical limits set by very nature of the reduction process, electronic structure chemical stability, and formulation of the catalyst as well as emission characteristic of the light source. The paper provides some clues for rational design of reductive-dehalogenation oriented photolytic systems, which are derived on the basis of physical principles, and, rather sparse, experimental examples.

X-ray high frequency pulse emission characteristic and application of CNT cold cathode x-ray source cathode x-ray source

Carbon nanotube (CNT) field-emission X-ray source has great potential in X-ray communication (XCOM) because of its controllable emission and instantaneous response. A novel voltage loading mode was proposed in this work to achieve high-frequency pulse X ray-emission. The characteristics of cathode current and pulse X-ray versus voltage, frequency, and pulse amplitude were studied, and XCOM data transmission experiment was carried out. Results showed that the CNT cold cathode X-ray source, as a communication signal source, could work in 1.05 MHz pulse emission frequency. When the grid voltage was higher than 470 V, the pulse X-ray waveform amplitude achieved peak, and the shape exhibited a pseudo square wave. The duty cycle of the X-ray waveform exceeded 50%, reaching 56% when the pulse frequency reached 1 MHz. In the XCOM data transmission experiment, the pulsed X-ray waveform was well consistent with the loading data signal voltage waveform under different pulse-emission frequencies. This work realized the X-ray high-frequency pulse emission of CNT cold cathode X-ray source and lays a foundation for the development and application of CNT cold cathode X-ray source in XCOM.

Physical Origin of Dual-Emission of Au–Ag Bimetallic Nanoclusters

On the origin of photoluminescence of noble metal NCs, there are always hot debates: metal-centered quantum-size confinement effect VS ligand-centered surface state mechanism. Herein, we provided solid evidence that structural water molecules (SWs) confined in the nanocavity formed by surface-protective-ligand packing on the metal NCs are the real luminescent emitters of Au-Ag bimetal NCs. The Ag cation mediated Au-Ag bimetal NCs exhibit the unique pH-dependent dual-emission characteristic with larger Stokes shift up to 200 nm, which could be used as potential ratiometric nanosensors for pH detection. Our results provide a completely new insight on the understanding of the origin of photoluminescence of metal NCs, which elucidates the abnormal PL emission phenomena, including solvent effect, pH-dependent behavior, surface ligand effect, multiple emitter centers, and large-Stoke’s shift.