Camal Rahmouni

Knock rating of gaseous fuels in a single cylinder spark ignition engine

Abstract This paper presents the determination of knock rating of gaseous fuels in a single cylinder engine. The first part of the work deals with an application of a standard method for the knock rating of gaseous fuels. The Service Methane Number (SMN) is compared with the standard Methane Number (MN) calculated from the standard AVL software METHANE (which corresponds to the MN measured on a Cooperative Fuel Research engine). Then, in the second part, the ‘mechanical’ resistance to knock of our engine is highlighted by means of the Methane Number Requirement (MNR). A single cylinder LISTER PETTER engine was modified to run as a spark ignition engine with a fixed compression ratio and an adjustable spark advance. Effects of engine settings on the MNR are deduced from experimental data and compared extensively with previous studies. Using the above, it is then possible to adapt the engine settings for optimal knock control and performances. The error on the SMN and MNR stands beneath ±2 MN units over the gases and engine settings considered.

Determination of the combustion properties of natural gases by pseudo-constituents☆

Abstract This paper presents a methodology for a rapid determination of important natural gas combustion properties (lower heating value, Wobbe index and the stoichiometric air–fuel ratio) using easily detectable physical properties. It is possible to determine natural gas composition by measuring two physical properties and using specific ternary diagrams (CH 4 –C 2 H 6 –C 3 H 8 and CH 4 –C 2 H 6 –N 2 ). The first part of the work deals with the selection of two physical properties from a group comprising thermal conductivity, refraction index, and speed of sound. Then, in the second part, a sensor using the best couple of physical property is used to determine the ternary pseudo-constituents of the gas mixture. The model and the sensor are applied to specific situations such as the online determination of LHV. The error on the combustion properties of natural gas is less than 1% over the gases considered in the present study and over about 20 typical gases supplied over Europe. The effect of small errors in the measurement of physical properties has also been highlighted.

A Numerical Comparison of Spray Combustion between Raw and Water-in-Oil Emulsified Fuel

Heavy fuel-oils, used engine oils and animal fat can be used as dense, viscous combustibles within industrial boilers. Burning these combustibles in the form of an emulsion with water enables to decrease the flame length and the formation of carbonaceous residue, in comparison with raw combustibles. These effects are due to the secondary atomization among the spray, which is a consequence of the micro-explosion phenomenon. This phenomenon acts in a single emulsion droplet by the fast (< 0.1 ms) vaporization of the inside water droplets, leading to complete disintegration of the whole emulsion droplet. First, the present work demonstrates a model of spray combustion of raw fuel. Secondly, the spray combustion of water-in-oil emulsified fuel is exposed to the same burning conditions, taking into account the micro-explosion phenomenon. Finally, the comparison between the results with and without second atomization shows some similar qualitative tendencies with experimental measurements from the literature.