The preparation and shock tube investigation of comparative ignition delays using blends of diesel fuel with bio-diesel of cottonseed oil

This paper describes an experimental effort for the production of cotton methyl ester (CME), cotton ethyl ester (CEE) and CEE–diesel blends from neat cottonseed oil (CSO) for use as a bio-diesel fuel and the investigation of the ignition delay times of these fuels using the shock tube. The transesterification of the neat CSO with methanol or ethanol has been performed to determine the optimum conditions for the preparation. The optimum parameters were cottonseed oil/alcohol molar ratio, 1:6; NaOH amount, 1% by the weight of the oil and reaction time, 75 min. The physical properties of all the tested fuels are measured. 89% of the neat CSO was converted into CME or CEE and the use of different alcohols (methanol or ethanol) presents few differences with regards to the kinetics of reaction but the final yield of esters remains almost unchanged. The ignition delay times were measured using a piezo-electric pressure transducer, charge amplifier, data acquisition card, IBM computer and LabVIEW program. Effects of equivalence ratio, initial charge temperature and initial charge pressure on the ignition delay times are discussed. The results show that the minimum ignition delay time was observed at an equivalence ratio of 1.05 for all the tested fuels. The ignition delay can be reduced considerably together with an increase of the initial charge temperatures and pressures. Also, the ignition delays of the tested fuels are compared with the diesel fuel.