Combustion and Oxidation of Lube Oils at Gas Turbine Conditions: Experimental Methods

Because of the high temperatures involved, undesirable ignition events can happen during gas turbine operation, often necessitating expensive down time and repairs. The ignition events are frequently linked to the lubricant, a flammable mixture of large hydrocarbons with a very low vapor pressure. To understand better the role of the lubricant in such ignition events, increased understanding of the fundamental thermal and oxidation characteristics of such oils is needed. To this end, a suite of different tests has been set up and demonstrated at the TEES Turbomachinery Laboratory at Texas A&M University (TAMU) to study various aspects of lubrication oil breakdown and oxidation at elevated temperatures, mostly those related to their coking and ignition behaviors. Five types of tests have been implemented: ignition delay time measurements using a shock tube; hot surface ignition (HSI); autoignition temperature (AIT) determination; thermal cook-off under controlled heating; and a high-temperature coking experiment. Such tests can be used both for fundamental understanding of how lube oils burn and for comparing the reactivity of various types and grades of oil. Each technique at TAMU is briefly described in this paper as they pertain to gas turbine lube oils, and sample results are presented for a common lubrication oil, Mobil DTE 732. For this oil, the HSI tests produced a lowest temperature without ignition of 510°C, and in shock-tube measurements, lower-temperature ignition kinetics are observed below about 1300 K, even at 1 atm. Typical AIT values for oils have been found to be around 370°C but do vary amongst brands, types, and level of degradation. The measured temperatures for the exothermic and boiling events were measured as 166±2 °C and 277±4 °C using the cook-off rig.

FLAMMABILITY OF HYDROCARBON FRACTIONS OBTAINED BY DESTRUCTION OF POLYMER RAW MATERIALS

The article discusses the possibility of using hydrocarbon fractions – products of thermal destruction of polymer raw materials (polyethylene and polypropylene) at atmospheric pressure as components of commercial diesel fuels. This approach allows, on the one hand, to improve the properties of commercial diesel fuel, on the other, to increase the competitiveness of domestically produced products. In addition, the problem associated with the accumulation of polymer waste and their negative impact on the environment is also partially solved. The nature of the dependences between such indicators of the quality of fractions 160–350 °C, 200–350 °C, 240–350 °C as the autoignition temperature, the initial boiling point of the fraction and the cetane number as an indicator characterizing the flammability, has been established. The dependence of the autoignition temperature on the boiling point of the fractions has a polynomial character and indicates a decrease in the autoignition temperature with an increase in the boiling point of the fractions. The dependence of the cetane number on the initial boiling point of the fractions is linear and indicates an increase in the cetane number with an increase in the initial boiling point of the fractions. The dependence of the cetane number on the autoignition temperature of the fractions has a polynomial character and indicates a decrease in the cetane number with an increase in the autoignition temperature of the fractions. It was found that the autoignition temperature of the investigated fractions, regardless of the type of polymer raw material, fluctuates in a rather narrow range, from 229 to 348 ° C, and the cetane number – from 41 to 55 units. Based on the literature data, we note that exactly this range is close to the range that commercial diesel fuels have, and the fractions studied by us can be used in the production of diesel fuel.

Comparative Evaluation of Bioethanol Production from Pineapple (Ananas comosus) and Cassava (Manihot esculenta)Waste from Warri

Fossil fuel is known to increase greenhouse gas emission which has resulted in serious environmental consequences. This study was designed to determine bioethanol production from pineapple(a fructogenic waste) and cassava (a glucogenic waste). It was also designed to allow a comparative analysis of pure ethanol with ethanol produced from the two food wastes with a view to generate an alternative fuel source. The parameters evaluated were the volume ofbioethanol per 100g of waste, percentage (%) purity of bioethanol produced, pH and auto ignition temperature of bioethanol produced. The values obtained were analyzed using the unpaired student’s t- test where appropriate to determine if there are any significant differences in pure ethanol values for those parameters. The result showed thatrelative to the pure ethanol(control), the auto ignition temperature of ethanol produced from the cassava (Manihot esculenta)and pineapple(Ananas comosus)wastes were significantly (p≤0.05) high. The autoignition temperature of ethanol produced from pineapple waste was slightly higher when compared to bioethanol from cassava waste but it was not statistically significant (p>0.05). The volume of ethanol produced from cassava waste was slightly lower (p>0.05), when compared to the volume of the same parameter in the pineapple waste. There was a significant (p≤0.05) decreasein pH of ethanolproduced from pineapple waste when compared to that from cassava waste. The % purity of the bioethanol produced from pineapple waste was higher (p>0.05) when compared to that from the cassava waste. The autoignition temperature of the blend of produced bioethanol was slightly reduced(p>0.05) when compared to the auto ignition temperatures of individual ethanol from separate waste. But, relative to the pure ethanol utilized as a control in this study, the autoignition temperature of the blend was significantly (p≤0.05) high. Finally, it was observed that bioethanolobtained from cassava waste (a glucogenic energysource) produced a lower yield involume with a 15.8 v/100g (ml) value while its fructogenic counterpart (pineapple waste) exhibited a slightly lower autoignition temperature effect (33oC). The autoignition temperature of the waste blend (Cassava-Pine) was 30oC when compared to each waste source alone.A combination of both cassava and pineapple waste yielded better fuel properties and iscampaigned in this study for use in the production of biofuel.