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Abstract: Mucosal vaccination has several advantages over parenteral vaccination. In this study, viscosity-enhancing mucosal delivery systems for the induction of an adaptive immune response against viral antigen were investigated. Powder formulations based on spray-dried mixtures of starch (Amioca®)/poly(acrylic acid) (Carbopol® 974P) in different ratios were used as carriers of the viral antigen. A comparison of these formulations for intranasal delivery of heat-inactivated influenza virus combined with LTR192G adjuvant was made in vivo in a rabbit model. Individual rabbit sera were tested for seroconversion against hemagglutinin (HA), the major surface antigen of influenza. The powder vaccine formulations were able to induce systemic anti-HA IgG responses. The presence of Carbopol® 974P improved the kinetics of the immune responses and the level of IgG titers in a dose-dependent way which was correlated with moderately irritating capacities of the formulation. In contrast, mucosal IgA responses were not detected. In conclusion, it was demonstrated that the use of bioadhesive carriers based on Amioca® starch and poly(acrylic acid) facilitates the induction of a systemic anti-HA antibody response after intranasal vaccination with a whole virus influenza vaccine. [Copyright &y& Elsevier]

• TJI concept was implemented in a high compression ratio turbocharged SI engine. • A numerical methodology was developed to design pre-chambers geometry. • Selected pre-chamber designs were experimentally evaluated and scored. • TJI concept is unable to extend dilution ratio to avoid the use of TWC system. • TJI concept is less tolerant to EGR dilution than the standard ignition concept. The pre-chamber ignition concept is an attractive strategy to enable the operation of spark-ignition engines in lean or diluted conditions keeping a suitable combustion process. According to the results the benefits in lean conditions include the combustion process shortening, the improvement of combustion stability and the increase of combustion efficiency by lowering carbon monoxide and hydrocarbons emissions. Thus, the pre-chamber ignition concept, especially in its passive version, arises as a promising alternative for future spark-ignition engines for passenger car applications. In this framework, an experimental investigation has been carried out to evaluate the potential of passive pre-chamber ignition concept in a high compression ratio, turbocharged, port fueled spark-ignition engine, using 95 Research Octane Number gasoline. As a first step, a 1D Wave Action Model was generated to design the pre-chamber geometry taking the fuel available at the start of pre-chamber combustion and the pressure difference between the main chamber and pre-chamber as key parameters. In a second step, these pre-chamber designs were experimentally validated at high load/speed conditions (4500 rpm, 12.5 bar Indicated Mean Effective Pressure) and compared with the conventional spark-ignition concept. Experimental results show how the passive pre-chamber concept increases efficiency with good combustion stability and high combustion efficiency in stoichiometric conditions. Nevertheless, maximum lambda attainable with the passive system is similar than that of the conventional spark and much lower compared to the maximum levels reported for the active system. [ABSTRACT FROM AUTHOR]

• The passive TJI system fueled by CNG is experimentally and numerically evaluated. • 1D numerical methodology helps to gain knowledge and improve the pre-chamber design. • Experimental results support the findings of the numerical methodology. • Increasing the pre-chamber volume has benefits under restrictive conditions. • An optimum swirl level inside the pre-chamber helps to stabilize combustion. Passive pre-chamber ignition concept has been proven to be an excellent strategy to increase the ignition energy and enhance the combustion velocity even when spark-ignition engines are operating in diluted conditions. Other benefits of this system are the increased combustion stability and combustion efficiency, reducing hydrocarbons and carbon monoxide emissions. However, these advantages are limited at some operation conditions such as low engine load or diluted conditions since both the energy available in the pre-chamber and the scavenge of combustion products are compromised. In this framework, numerical studies using two different computational tools, based on one-dimensional modeling, are utilized to gain knowledge about the governing parameters and to improve the design of a pre-chamber when the engine operates at these restrictive conditions. In particular, the impact of the pre-chamber volume, the total cross sectional area of the holes and tangential angle of the nozzles have been numerically evaluated. Different pre-chamber designs were proposed and experimentally tested in a single-cylinder, high compression ratio turbocharged spark-ignition engine fueled with compressed natural gas and operating on Miller cycle. Results give valuable insight into the key aspects of the internal geometry and some relevant design paths to follow for a suitable pre-chamber definition. [ABSTRACT FROM AUTHOR]

In view of the increasing restrictions for CO 2 mitigation, the evaluation of alternative fuels to ensure sustainability of transportation is becoming increasingly important. Since some of these alternatives can be refined from renewable sources, they are interesting from the perspective of both: the use of the current power-plants and the CO 2 emission. In this sense, natural gas arises as an interesting propellant to substitute fossil fuels. Therefore, combining this fuel with specific combustion strategies can help to decrease the environmental footprint of transportation in the broadest sense. In this paper, an evaluation of the possible advantages of this combination has been conducted. The investigation has been carried out in a port fueled turbocharged spark-ignition engine, using compressed natural gas (CNG) and a passive pre-chamber ignition system. The effects of the CNG fuel properties on combustion have been analyzed and the global impact of using CNG for transportation has been appraised by means of the life cycle assessment. Results show that combustion of CNG refined by different renewable sources not only reduces the global CO 2 emission but also can contribute to remove the existent pollution. In addition, they show an increase of the engine thermal efficiency when combining CNG and the pre-chamber ignition concept. [ABSTRACT FROM AUTHOR]