The selection of suitable working fluid for simple and recuperative organic Rankine cycle (ORC) operating under subcritical, superheated and supercritical conditions are investigated. 11 fluids with critical temperature above 1500C are considered as potential candidates. Performance screening...

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.

This work presents a pneumatically operated piston released rapid compression machine (PRRCM) designed at the University of Sheffield that introduces a new set of pneumatic systems to lock/release the piston from its initial position. It is pneumatically operated to compress gas mixture to an adiabatically thermodynamic state and stopped hydraulically. The range of compression ratios of the facility is between 4.4 and 20. The end of compressed gas temperature, T _c and pressure, P _c obtained within the facility is approximately 1000 K and 22 bar respectively. The performance of the Sheffield piston released rapid compression machine (SHEF-PRRCM) facility has been characterised to ensure a high level of fidelity of experimental data over a range of test conditions. The performance test was conducted for a nonreactive test using nitrogen and argon, the result demonstrated a repeatable pressure trace. Repeatability test for the reactive mixtures was also demonstrated. Further study on ignition characteristics of aviation fuel (Jet A-1) and Banner NP1014 known as Bannersol in SHEF-PRRCM was conducted over T _c of 723 K ⩽ T _c ⩽ 884 K, P _c = 6 and 10 bar at ϕ = 0.75 and 1.0. The influence of pressure, temperature and equivalence ratio was seen on the oxidation of Jet A-1 and Bannersol. The results showed that Bannersol displayed a negative temperature coefficient behaviour and has higher reactivity than Jet A-1. Besides, a comparative analysis of the current facility with other facilities in literature was carried out, the result showed a fair deviation of the current data from literature and these could be attributed to the inherent non-ideality of heat transfer effects in different rapid compression machine and fairly slight differences in the condition tested. This work has demonstrated the competence of the current facility to carry out further studies on combustion and validation of the chemical kinetics of hydrocarbon fuels.

In the current research, experimental work is investigated for vertically and horizontally downward propagating flames in an open-ended tube. The objective was to study and compare the influence of flammability limits, gravity, and the flame speed in the different tube configuration for two different fuels. The experimental facility included a 20 mm inner diameter tube, 1200 mm in length and an optical access quartz tube made centrally of 700 mm in length. Methane-air and propane-air fuel were compared for both vertically and horizontally downward propagating flames. The flame speed at each equivalence ratios for both fuels was lower for the flame that propagates downward compared to the flame that propagates horizontally. For both fuels, the flammability limits tend to rise for the vertically downward flame. The influence of gravity was seen as the flames become leaner and richer in methane-air and propane-air flames that propagate vertically downwards, causing a transformation in the contour of the flame from a steady curved flame to a vibrating corrugated flame.