Research Projects

In the last few years, thermal management of onboard supersonic engines has gained considerable attention from different R&D groups. A supersonic combustion ramjet (SCRAMJET) engine at hypersonic speed warrants severe cooling requirements to manage its thermal load. Above Mach-4 speeds, the temperature of the intake air becomes too high to cool the engine. Although cryogenic fuels can provide sufficient cooling, the associated cost, weight, logistics, and safety will be the major concerns for additional cryogenic fuels. To fulfil dual purposes, endothermic fuels can be a substitute for traditional jet fuels. Endothermic fuels are hydrocarbons that have the capacity to absorb large quantities of heat. The partial cracking of fuel will enhance the heat sink further. In the last 10-15 years, the suitability of endothermic fuel for supersonic applications has been studied by many researchers. Hydrocarbon fuels such as JP–7, RP–3, JP–10, n-heptane, and n-decane have been considered in studies, and the reported value of heat sink capacity lies in the range of 2300-2700 kJ/kg of fuel for a temperature range of 500-650 oC. Though a good number of investigations are available, the methodologies adopted in calculating the heat sink, cracking percentage, and coke deposition are not furnished explicitly in many studies, which undermines the data reproducibility. Most of the experiments on endothermic fuel have been performed below 45 bar pressure and a temperature range of 500-650 °C. Relatively less information is available above 50 bar. Although the critical pressure for most fuels is less than 30 bar, the critical pressure of ethylene and ethane is more than 45 bar. Hence, the reactor pressure should be more than 50 bar to maintain a single-phase. Due to analysis simplicity, many studies are on single-component hydrocarbons like n-heptane, n-decane, and n-dodecane. Studies on multi-component fuel are few in number. In most studies, it is mentioned that the heat sink capacity of a fuel was determined by subtracting the heat loss from the heat input data. But the heat loss estimation details are not furnished. The majority of investigations focused either on cracking conversion or the heat sink of various fuels. Limited attention was paid to the coke deposition aspect, a critical issue. Also, in most of the studies, the authors mentioned the reactor coke only. The flow-away coke can also block the fuel transfer nozzle and reduce/stop the fuel flow to the combustor. It is noted that more than 80% of total investigations on endothermic fuels are from three countries (China, USA, and Russia). Over the last five years, a few other countries, such as France, UK, Turkey, Korea, etc., have also geared up in this field. In recent years, India’s defense sectors have also started various research activities on the development of indigenous endothermic fuel for hypersonic applications. Recently, we have also demonstrated some preliminary studies on the cracking of n-heptane, n-decane, and a jet fuel, and the results intrigue us to carry out further in-depth and higher TRLs research in this field. We believe there is a significant scope for both basic and applied research in this field. The objective of the research proposal is to develop a high-density hydrocarbon-based indigenous endothermic fuel that can be suitable for supersonic/hypersonic applications. The study will be useful for the defence sectors. The proposal is inter-disciplinary in nature, with involvement of both the Chemical and Aerospace departments from two different institutes. The present research proposal is aligned with India’s national initiative ‘Make in India’ along with the national vision for ‘Atmanirbhar Bharat’. More details on the existing status of research are mentioned in the main document.