Final Report, Combustion Fundamentals of PO and PO based fuels in lab scale equipment - EU Contract ENK5-CT-2002-00690 \"COMBIO: A New Competitive Liquid Biofuel for Heating\" (Rapporti finali progetti di ricerca)

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  • Final Report, Combustion Fundamentals of PO and PO based fuels in lab scale equipment - EU Contract ENK5-CT-2002-00690 \"COMBIO: A New Competitive Liquid Biofuel for Heating\" (Rapporti finali progetti di ricerca) (literal)
Anno
  • 2006-01-01T00:00:00+01:00 (literal)
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  • R. Calabria, P. Massoli. F. Chiariello (2006)
    Final Report, Combustion Fundamentals of PO and PO based fuels in lab scale equipment - EU Contract ENK5-CT-2002-00690 "COMBIO: A New Competitive Liquid Biofuel for Heating"
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  • R. Calabria, P. Massoli. F. Chiariello (literal)
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  • Il progetto è stato svolto, nel periodo 1.1.2003 - 30.6.2006, in collaborazione con: VTT/Process, Helsinki; Fortum Oy (Finlandia); Università di Firenze - Consorzio Interuniversitario Sistemi a Grande Interfase (Firenze); Birka Varme (Svezia); Vapo (Finlandia); ETA Energie Rinnovabili (Firenze). (literal)
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  • Istituto Motori - C.N.R. (literal)
Titolo
  • Final Report, Combustion Fundamentals of PO and PO based fuels in lab scale equipment - EU Contract ENK5-CT-2002-00690 \"COMBIO: A New Competitive Liquid Biofuel for Heating\" (literal)
Abstract
  • The purpose of the present task was to support the development and application of Emulsion of Pyrolysis Bio Oil (PO) in furnaces with the specific aim of studying the combustion fundamentals of POs and POs based emulsions. Particular attention was placed on the comparison with the combustion behaviour of the parent light oil being the utilization of emulsion envisaged in boilers where light fossil oils were used. The work programme was centred on the influence of the chemical-physical properties of emulsions on the combustion quality. The study was carried out on emulsions characterized by different: i) Size of droplets of PO dispersed in the diesel fuel ii) Percentage of PO in the emulsion iii) Percentage and quality of surfactant and co-surfactants iv) Ageing. In the combustion analysis, several indicators were evaluated. The main were: a) Ignition b) Swelling/microexplosions c) Gaseous emissions d) Solid residuals e) Homogeneous combustion time (combustion of the liquid phase) f) Heterogeneous combustion time (combustion of solid residuals) The work was executed in two different experimental systems, the Single Droplet Combustion Chamber (SDCC) and the Drop Tube Furnace (DTF). A main feature common to both the SDCC and DTF is the small quantity of fuel required to execute the tests: from few cubic centimetres to few hundreds cubic centimetres for SDCC and DTF, respectively. This permitted to test a matrix with a number of different fuels. The second aspect should be mentioned is the strategic synergy between the two experimental approaches. In the SDCC, a single large droplet is studied; in the DTF a dilute but real spray is studied. This permits to infer complementary data, as explained below. In addition, it has to be underlined that the experimentation on the DTF permitted to set up the optical diagnostics that was applied in the \"Tests with a PO emulsion in a small boiler\" (Combio modif. work plan 3.3, Feb 16 2005). In the SDCC they were burned single droplets of size comprised between 0.4 mm and 1.2 mm. Despite this size is clearly out of the dimensions occurring in practical sprays, the data inferred in this kind of experiments permit to describe the thermal behaviour of a fuel and to extract its peculiar combustion data. Examples are the tendency to form residuals, the burning rate etc. Moreover, many data available in literature refer to similar experimental conditions. This aspect is relevant when new fuels are tested because this experimentation permits to directly compare the inferred experimental data with the ones concerning standard fuels. The SDCC approach can be deemed like a thermogravimetry apparatus but where the fuel undergoes a thermal history much more close to the evolution experienced by a droplet in a burning spray. For example, the heating velocity in the SDCC is as high as 1000 K/s and the life of droplets is few seconds. A high heating rate is very critical for complex thermally instable fuels. In fact, a slow and long heating can promote reactions not activated in real combustion conditions. Thus the inferred data result strongly affected by the experimental procedure utilized. In the DTF, a dilute spray of monodisperse droplets was injected in air stream heated at high temperature. The modal value of the narrow size distribution was around 80 µm. The DTF spray analysis permitted to examine two main questions related to emulsion combustion quality. The first concerns the stability of the emulsions with respect to the mechanical stress underwent by the liquid during the formation of spray. The second was related to the thermal stability of the emulsions during droplet evaporation. To this aim the two-dimensional GSI technique was applied. In fact, GSI is the unique technique that permits to measure the size and the optical properties of droplets in a spray. The determination of optical properties is very relevant in the study of non-stationary sprays because the optical properties of a liquid are connected to its composition. In particular, GSI measures the imaginary part, k, of the refractive index of the liquid composing the droplets. This parameter is a relevant marker to study the evolution of PO emulsion droplets because k is 10-4 - 10-3 for pyrolysis oils and 10-6-10-5 for light oil. Thus it is possible to discriminate about the composition of a droplet. The activities performed in the DTF were also functional to the tests on large sprays (Task 3.3 \"small boilers\"). In fact, the same optical technique set and utilized for the characterization of the sprays in the DTF was applied in the experimentation concerning large sprays. (literal)
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