• Energy Research
• 13. Climate action close
• 7. Clean energy close
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• Istituto Motori close

The Istituto Superiore di Sanità (ISS, the National Institute of Health of Italy) and the Istituto dei Motori (IM) of the Consiglio Nazionale delle Ricerche (CNR, National Research Council) have carried out this study, jointly funded by the two institutes together with the Ministry of Environment. The chemical and toxicological characteristics of emissions from two urban bus engines were studied: a diesel engine fueled with both diesel oil and biodiesel blend and an equivalent spark-ignition one fuelled with compressed natural gas, operating in steady-state conditions. Regulated and unregulated pollutants, such as carcinogenic polycyclic aromatic hydrocarbons and nitrated derivatives, carbonyl compounds and light aromatic hydrocarbons were quantified. Mutagenicity of the emissions was evaluated by the Salmonella typhimurium/mammalian microsome assay. The effect of the fuels under study on the size distribution of particulate matter was also evaluated. The impact of diesel-powered transport on urban air quality, and the potential benefits for human health deriving from the use of natural gas for public transport, are discussed.

Experimental evaluation of the combustion characteristics of carbon-neutral, biomass-derived fuels has been carried out. Since these fuels are meant as likely replacement for CH4, a comparison was drawn with methane in the same operating conditions. Tests were performed in the high-pressure, constant-volume DHARMA reactor at Istituto Motori - CNR. The laminar burning parameters were evaluated analyzing spherical expanding flames. The flame growth was recorded by means of high-speed, high-resolution shadowgraph; image processing and stretch analysis allowed to infer the laminar burning velocity and the Markstein length for each test case. Results are presented for the combustion in air of CH4-CO2 (55-45 % vol.), H2-CO (5-95 % vol.) and a wood gasification product. All the tests were performed at 0.6 MPa and 301 K. The equivalence ratio ranged between 1.0 and the lower flammable limit. The unstretched laminar burning velocity and the Markstein length are reported for each fuel as a function of the equivalence ratio.