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various locations, in-cylinder pressures, crank position and exhaust gas composition. A 35- cc two-stroke spark-ignition engine fuelled by petrol was chosen for the tests. Initially, the basic tests were performed
to characterise the engine
performance with petrol. These
results were taken as a base
reading for further comparison.
For further tests, nitromethane
was added to petrol in varying
compositions. Intermediate
alcohol was added to enable
the mixing of nitromethane with
petrol. The mixed fuel was filled
into the fuel tank for engine
tests. Tests were done under
various engine conditions. The
engine throttle position, air fuel
ratio, spark timing, compression
ratio, propeller sizes, lubricant quantity, etc. were varied to optimize the engine to its best performance with the nitromethane-blended fuel.
The results showed a 40% increase in the power output, which potentially meant that a smaller engine could be used on-board of the UAV, saving some valuable weight. Additionally, a 5% reduction in fuel consumption was also obtained. Further analysis was carried out to investigate the reasons for enhanced performance. It was found that the flame speed and flame temperatures increased with the addition of nitromethane. This resulted in the improved combustion efficiency of the engine. A reduction in carbon moNOxide and hydrocarbon emissions was observed with nitromethane addition. On the downside, due to increased temperatures, the nitric oxide emissions and engine surface temperatures shot up drastically. Future work should aim to
Dr Raviteja S || 59
reduce nitric oxide emissions with lean engine operations and improve fin design to reduce engine surface temperatures.
With these achievements, it would be possible
to make drones more powerful and increase their flight durations. Our team at IIT- Madras is also developing a complete drone using the above- developed technology for long endurance and surveillance missions. A photograph of the same is presented here. The possibilities with these drones would be endless. With further developments in technologies, we can potentially avoid direct involvement of human life in wars.
Being a peace-loving nation, we would spread the message of peace and harmony to the world. But in case of misbehaviour, the drones would hunt down the enemy with no compromise of army lives. The wars of muscle power are over; further is going to be a war of technology. It is important for us to start early and have a progressive advancement in defence technology. The present work is a tiny step towards this mission.
   The goal of the present work was to further enhance the specific power of the UAV engines by increasing the power output of the engine without adding additional weight or by increasing the complexities. It is well known that the engines run at full power only during the take-off of the flight.
      










































































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