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The presented research work examines the effects of different fuel-air equivalence ratios and initial pressure on ignition temperature.
This study shows a non-monotonic pressure dependence in stoichiometric mixtures at varying pressures from 1 to 10 bar and a low sensitivity to changes in the equivalence ratio (0.5-2). The results form the basis for our future research into the complex interaction between lubricant characteristics and hydrogen-air mixtures to better understand pre-ignition phenomena in internal combustion engines.
Self-ignition of coal dust deposits poses a higher risk of fires in oxygen-enriched oxy-fuel combustion systems. In this work, we develop a numerical method, using the commercial software COMSOL Multiphysics, to investigate self-ignition behaviour of coal dust accumulations with a main emphasis on the roles of oxygen, diluent gas and dust volume. A one-step 2nd-order reaction kinetic model considering both coal density and oxygen density is used to estimate reaction rate using the kinetic parameters from previously conducted hot-oven tests. This model is validated to predict the transient temperature and concentration profiles of South African coal dusts until ignition. The computed self-ignition temperatures of dust volumes show a good agreement with experimental results. In addition, it is found that the inhibiting effect of carbon dioxide is comparatively small and oxygen consumption increases dramatically after ignition. Parameter analysis shows that the heating value and kinetic parameters have a comparatively pronounced effect on self-ignition temperature. The model provides a satisfactory explanation for the dependence of self-ignition behaviour on gas atmospheres, thus helping to further understand the fire risk of self-ignition in oxy-fuel combustion systems.
The gaseous TFE is a monomer which is used to form PTFE, also known as Teflon®, by a polymerisation process at elevated conditions of temperature and pressure. TFE belongs to the group of chemically instable gases which are able to decompose under specific conditions releasing a huge amount of heat comparable to a gas explosion of flammable gases. Due to several incidents in PTFE – production plants the investigation of the safety related properties of TFE at elevated condition was necessary and resulted in a research project at BAM which is subsidized by the PlasticsEurope association. In a first stage the pressure dependence of the Minimum Ignition Temperature for Decomposition (MITD) was determined in the range of 0.5 MPa - 3 MPa in small autoclaves with volumes of 0.2 dm³ and 3 dm³. These results were used to validate the numerical model and were found to correlate quite well with the simulated values. Nevertheless the applicability had to be confirmed for larger volumes as well. Therefore a heat able 100-dm³-autoclave was constructed and build to determine the MITD in the range of 0.5 MPa to 1.1 MPa.