One of the conditions for controlling the aerodynamic in the reaction chamber is designing a crevice volume on the surface of the piston head. The importance of the crevice volume is to contain the cool boundary layers generated as a resulting of the moving reactor piston. But this crevice volume...

The fabrication of a rapid compression machine (RCM) is in its early phase of design. The machine is designed to enhance the study of ignition delay and validation of detailed kinetics models of fuels. The machine compresses fuel/air mixtures isentropically within 25 to 52 ms with a varying stroke. The combustion chamber design is not fixed and can be adjusted through the threaded shaft lock and within chamber slots. The originality of the facility is the inclusion of a pneumatic piston release mechanism (PPRM), which is pneumatically operated. The current test facility has been characterised by conducting a nonreactive and reactive experiment, the result showed that an obtainable compressed pressure of 21 bar and end gas temperature of approximately 1000 K was achievable within the present facility. The fidelity of the facility was performed with a non-reactive experiment, which experimental pressure profile was seen to follow each other closely showing that the data are highly repeatable within the test condition, the result was free from any form of rebound or disturbance, which would have adversely distort the result. The experiment data was simulated implementing the effective volume approach and was seen to perfectly match with the experiment at both stages of compression. The reactive experiment was demonstrated with heptane/air mixture at stoichiometric condition, T_C = 625 ⩽ 689 K. The results show that the experimental pressure traces overlay each other thus signifying a repeatable pressure trace and this demonstrates that the Shef-RCM is operable and ready at its first stage of design for studying the ignition delay time of liquid fuels operating within an engine like conditions and for validating chemical kinetics models.

Experimental work is reported for premixed flames propagating in tubes. The flames were ignited with a pilot flame and the flame propagation captured with high-speed cameras. Initial measurements were performed characterizing the rig. For downwardly propagating flames to a closed-end, methane and propane were studied. The flames initially propagated steadily, then at approximately a third of the way down the tube, the primary acoustic oscillation sets in, resulting to a change in the flame shape. This was then followed by a plateau of variable length before a more violent secondary acoustic oscillation. In some circumstances, flames were observed to rotate due to the primary acoustic instability. The flame front position growth rate for both methane and propane were similar despite the differences in the fuels. The total acoustic loss time for propane and methane increases from the lean limit with the equivalence ratio, peaks at φ = 1.1 and then decreases as the mixture becomes richer. There was also an increase in the total acoustic loss time as the angular speed of the flame increased. The results showed that the generation of acoustic energy for propane was smaller than that of methane due to the stronger natural damping effect of the former.

Premixed flame propagation in an open-ended horizontal tube has been investigated. Methane-air flames (ø =1.2) enriched with hydrogen were filmed with a high-speed camera and the pressure captured. Two-thirds along the tube, the flames encountered an acoustic field and were subjected to longitudinal oscillations. Depending on the hydrogen content, significant differences were observed in the behaviour of the flames. For lower hydrogen concentrations (RH 0.1 – 0.3), the flame speed initially decreased as it entered the field, and was then subjected to violent oscillations, resulting in a high acceleration and speed. The accelerations were attributed by the formation of Rayleigh-Taylor instabilities, which existed in the form of spikes of unburned mixture into the burned gasses that coupled with the pressure oscillations. This satisfied the Rayleigh criteria that the acoustically driven instabilities require the heat release and pressure waves to be in phase. When the hydrogen content was increased, as the flame passed through the acoustic field, the flame speed decreased, and no Rayleigh-Taylor instabilities were observed. This difference in behaviour with hydrogen content was attributed to the higher flame speeds with higher hydrogen concentrations.

This paper presents a framework for energy, exergy utilization, and economic analysis of industrial steam boiler system in Nigerian Bottling Company (NBC), Enugu, Nigeria. The study was carried out by an investigative approach in which all other parameters were kept constant, and a particular one was varied, and the desired quantity measured. The results of the effects of burner rotary cup speed and fuel nozzle sizes on emissions show that for boiler having liquid fuel nozzle sizes 3mm, 4mm and 6mm and with constant fuel inlet temperature of 82oC were analysed. Nozzle size of 4mm diameter with burner rotary cup operating at speed of 2920rev/min to 3200rev/min generated minimum emission while burning fuel oil of 82oC with excess air of 12.36%. Similarly, nozzle size of 6mm with rotary cup burner operating between 3950rev/min to 4400rev/min at 12.36 % excess air generated no emission of CO and NOx. It was concluded that the combustor yielded the highest energy efficiency of 99.8% while the heat exchanger gave the lowest energy efficiency of 94% when run on both fuel oil and natural gas. This improved efficiency translates to a savings of approximately 89 million naira annually for a boiler operating at 46% availability yearly.