Effect of atmospheric aging on volatility and reactive oxygen species of biodiesel exhaust nano-particles

In the prospect of limited energy resources and climate change, effects of alternative biofuels on primary emissions are being extensively studied. Our two recent studies have shown that biodiesel fuel composition has a significant impact on primary particulate matter emissions. It was also shown that particulate matter caused by biodiesels was substantially different from the emissions due to petroleum diesel. Emissions appeared to have higher oxidative potential with the increase in oxygen content and decrease of carbon chain length and unsaturation levels of fuel molecules. Overall, both studies concluded that chemical composition of biodiesel is more important than its physical properties in controlling exhaust particle emissions. This suggests that the atmospheric aging processes, including secondary organic aerosol formation, of emissions from different fuels will be different as well. In this study, measurements were conducted on a modern common-rail diesel engine. To get more information on realistic properties of tested biodiesel particulate matter once they are released into the atmosphere, particulate matter was exposed to atmospheric oxidants, ozone and ultra-violet light; and the change in their properties was monitored for different biodiesel blends. Upon the exposure to oxidative agents, the chemical composition of the exhaust changes. It triggers the cascade of photochemical reactions resulting in the partitioning of semi-volatile compounds between the gas and particulate phase. In most of the cases, aging lead to the increase in volatility and oxidative potential, and the increment of change was mainly dependent on the chemical composition of fuels as the leading cause for the amount and the type of semi-volatile compounds present in the exhaust

Numerical simulation of performance and exhaust emissions of a marine main engine using heavy fuel oil during the whole voyage

In this study, the performance and exhaust emissions of the marine main engine (ME) of a large cargo vessel operating on the east coast of Australia by numerical thermodynamic simulation were investigated. The simulation were validated using on-board measurements of the ME conducted in October and November 2015 on a large cargo ship cruising between Ports of Brisbane, Gladstone and Newcastle. The commercial engine modelling/design software, AVL Boost, was used with special adaptation to marine engines and Heavy Fuel Oil (HFO). All measurements here carried out on the ME at different engine speeds and loads when the ship experienced different working conditions such as manoeuvring near port areas and cruising at sea. Specific engine parameters including in-cylinder mean and peak pressure, power, exhaust temperature and turbocharger boost were investigated. A good agreement between experimental and numerical results was observed for engine emissions of NOx and soot at higher engine speed conditions. The capacity of AVL Boost for marine engine simulation is evaluated, including prediction on the engine performance and emissions under different engine working conditions where they cannot be measured in the experiment

Development and validation of A quasi-dimensional model for (M)Ethanol-Fuelled SI engines

RESEARCH OBJECTIVE - The use of methanol and ethanol in spark-ignition engines forms an interesting approach to decarbonizing transport and securing domestic energy supply. Experimental work has produced promising results, however, the full potential of light alcohols in modern engine technology remains to be explored. Today, this can be addressed at low cost using system simulations of the whole engine, provided that the employed models account for the effect of the fuel on engine operation. The goal of current work is to develop an engine cycle model that can accurately predict performance, efficiency, pollutant emissions and knock onset in state-of-the-art neat alcohol engines. METHODOLOGY - Two-zone thermodynamic engine modeling, in combination with 1D gas dynamics, is put forward as a useful tool for cheap and fast optimization of engines. Typically, this model class derives the mass burning rate of fuel from turbulent combustion models. A fundamental building block of turbulent combustion models is an expression for the laminar burning velocity of the fuel-air-residuals mixture at instantaneous cylinder pressure and temperature. This physicochemical property basically groups the contribution of the chemical reactions (of the fuel) to combustion. Consequently, an important part of our study consisted of calculating (using chemical kinetics) and measuring the laminar burning velocity of methanol and ethanol at engine-like conditions. In order to validate the developed engine model, its predictions were compared against a database of experimental results obtained on three different flex-fuel and dedicated alcohol engines. RESULTS - Comparison of the experimental and simulated cylinder, intake and exhaust pressure traces confirmed the predictive power of our engine model for methanol-fuelled engines. A wide variety of engine operating points were accurately reproduced thanks to a new laminar burning velocity correlation, which correctly accounts for changes in pressure, temperature, mixture richness and residual ratio. The Flame Closure Model of Zimont-Lipatnikov emerged as the most widely applicable model from a comparison of several turbulent combustion models. With regard to the gas dynamics it proved necessary to include a fuel puddling submodel to take the cooling effect due to alcohol injection into consideration. LIMITATIONS - The developed model was successfully validated for normal combustion in port-injected neat methanol engines. The validation of the routines for ethanol combustion and engines with direct injection is part of ongoing work. Now that normal combustion can be accurately simulated, further work will look at the prediction of pollutant emissions and knock onset in these engines. NOVELTY - This paper presents the first recent attempt to model the application of neat alcohols in modern and anticipated future engine technologies. Compared to previous work the effects of in-cylinder and mixture conditions on the combustion are more accurately predicted thanks to the inclusion of a new and widely validated laminar burning velocity correlation. In contrast to other studies, the current experimental database also includes measurements on turbocharged, high compression ratio engines with elevated amounts of EGR, which is representative of future dedicated alcohol engines. CONCLUSIONS - The current work focused on adapting the various submodels of quasi-dimensional engine codes to the properties of light alcohols. The developed simulation tools can be used with confidence to optimize current and future engines running on neat methanol and ethanol. This work also forms the starting point for an extension of the modelling concepts to alcohol-gasoline blends, which hold more industrial relevance

Emissions of particulate matter, carbon monoxide and nitrogen oxides from the residential burning of waste paper briquettes and other fuels

Using waste paper as fuel for domestic heating is a beneficial recycling option for small island developing states where there are lacks of resources for energy and waste treatment. However, there are concerns about the impact of air pollutants emitted from the burning of the self-made paper briquettes as household air pollution is recognised as the greatest environmental risk for human. In this study, combustion tests were carried out for paper briquettes made in one Pacific island and three commercial fuels in Australia including wood briquettes, kindling firewood and coal briquettes in order to: 1) characterise the emissions of three criteria air pollutants including particulate matters, CO and NOx including their emission factors (EF) from the tested fuels; and 2) compare the EFs among the tested fuels and with others reported in the literature. The results showed that waste paper briquettes burned quickly and generated high temperature but the heat value is relatively low. Paper briquettes and coal briquettes produced higher CO concentration than the others while paper briquettes generated the highest NOx level. Only PM2.5 concentration emitted from paper briquettes was similar to kindling firewood and lower than wood briquettes. Burning of paper briquettes and wood briquettes produced particulate matter with large average count median diameter (72 and 68 nm) than coal briquette and kindling firewood (45 and 51 nm). The EFs for CO, NOx and PM2.5 of paper briquettes were within the range of EFs reported in this study as well as in the literature. Overall, the results suggested that using paper briquettes as fuel for domestic heating will not likely to generate higher level of three major air pollutants compared to other traditional fuels

Particle emissions from biodiesels with different physical properties and chemical composition

Biodiesels produced from different feedstocks usually have wide variations in their fatty acid methyl ester (FAME) so that their physical properties and chemical composition are also different. The aim of this study is to investigate the effect of the physical properties and chemical composition of biodiesels on engine exhaust particle emissions. Alongside with neat diesel, four biodiesels with variations in carbon chain length and degree of unsaturation have been used at three blending ratios (B100, B50, B20) in a common rail engine. It is found that particle emission increased with the increase of carbon chain length. However, for similar carbon chain length, particle emissions from biodiesel having relatively high average unsaturation are found to be slightly less than that of low average unsaturation. Particle size is also found to be dependent on fuel type. The fuel or fuel mix responsible for higher particle mass (PM) and particle number (PN) emissions is also found responsible for larger particle median size. Particle emissions reduced consistently with fuel oxygen content regardless of the proportion of biodiesel in the blends, whereas it increased with fuel viscosity and surface tension only for higher diesel–biodiesel blend percentages (B100, B50). However, since fuel oxygen content increases with the decreasing carbon chain length, it is not clear which of these factors drives the lower particle emission. Overall, it is evident from the results presented here that chemical composition of biodiesel is more important than its physical properties in controlling exhaust particle emissions

A comparison of particulate matter and gaseous emission factors from two large cargo vessels during manoeuvring conditions

In this study, emission factors of both particle and gaseous phases are characterised on board two large cargo vessels operating on the east coast of Australia during manoeuvring conditions. In order to investigate the difference in particle number and mass size distributions, measurements were conducted on two 2-stroke engines of two vessels using Heavy Fuel Oil (HFO) with nearly the same sulphur content. Results showed that manoeuvring compared to ocean-going conditions resulted in higher emission factors for carbon monoxide (CO), carbon dioxide (CO2), unburnt hydrocarbon (HC), particulate matter (PM) and particle number (PN), which can have significant negative effects on human health and the environment in coastal and port areas. Importantly, a significant difference was observed in particle number size distributions between the two vessels. Those observed for Vessel II were mono-modal with the peak at 40–50 nm and dominated by ultrafine particles (D < 100 nm), while for Vessel I a bimodal distribution with a nucleation peak at around 20 nm and a major peak at larger diameter of 60 nm was observed. The difference in particle number size distributions between the two vessels may be due to the difference in sampling location and/or marine engine characteristics, including age and technology. The effects of fuel sulphur content on PN and PM emissions observed in this study are also compared with the results available from previous measurements in the literature. Engine load was also found to be an important influence on all emission factors

Influence of fuel molecular structure on the volatility and oxidative potential of biodiesel particulate matter

We have studied the effect of chemical composition of biodiesel fuel on the physical (volatility) and chemical (reactive oxygenated species concentration) properties of nano particles emitted from a modern common-rail diesel engine. Particle emissions from the combustion of four biodiesels with controlled chemical compositions and different varying unsaturation degrees and carbon-chain lengths, together with a commercial diesel, were tested and compared in terms of volatility of particles and the amount of reactive oxygenated species carried by particles. Different blends of biodiesel and petro diesel were tested at several engine loads and speeds. We have observed that more saturated fuels with shorter carbon chain lengths result in lower particle mass but produce particles that are more volatile and also have higher levels of Reactive Oxygen Species. This highlights the importance of taking into account metrics that are relevant from the health effects point of view when assessing emissions from new fuel types