PROBLEM BACKROUND
Auto Rickshaws in Mumbai: Facts and figures
- 77.4% of the Auto Rickshaws in Mumbai use 2 stroke engines
- 98% of Rickshaws powered by CNG, and only 2% powered by gasoline
- Rickshaws emit the highest levels of PM while accelerating and while idling, which account respectively for 40% and 15% of their operation.
Hybrid Powertrain
- Harvests kinetic energy during braking and drives Rickshaw during acceleration
- Fills in gaps of inefficient and polluting power delivery for engine
- Meshes into existing Rickshaw geometry
- Near carbon-neutral energy production during accelerating and braking
- Ideal for stop-and-go traffic
PROPOSED SOLUTION
After considering other means of energy storage, such as batteries and a regenerative flywheel, compressed air was chosen as the preferred energy storage method. The others were either too expensive given the financial status of typical rickshaw drivers or posed to much of a safety risk or risk of being stolen.
The proposed alternative is relatively cheap, easy to implement and does not require much technical knowledge on the part of the driver for installation and repair. Under this method, air is compressed while the rickshaw is braking by using the driveshaft of the rickshaw to power a recipcrocating compressor. The compressed air is then stored in a tank of approximately 5 liters (calculated based on a typical rickshaw mass of 660 kg). Once the driver is ready to accelerate again, the high pressure air from the storage tank is then run through the compressor and used to rotate the shaft of the compressor which is in turn geared to the rickshaw's driveshaft. This propels the rickshaw to a velocity near that from which it originally decelerated.
The proposed alternative is relatively cheap, easy to implement and does not require much technical knowledge on the part of the driver for installation and repair. Under this method, air is compressed while the rickshaw is braking by using the driveshaft of the rickshaw to power a recipcrocating compressor. The compressed air is then stored in a tank of approximately 5 liters (calculated based on a typical rickshaw mass of 660 kg). Once the driver is ready to accelerate again, the high pressure air from the storage tank is then run through the compressor and used to rotate the shaft of the compressor which is in turn geared to the rickshaw's driveshaft. This propels the rickshaw to a velocity near that from which it originally decelerated.
ACHIEVED RESULTS
The first metric that was used to determine the viability of the system was a comparison of the modeled energy storage capacity versus measured energy storage based on the initial flywheel speed. The modeled energy storage was based on the kinetic energy of the flywheel at its maximum rotational velocity. The measured energy was based on the final air pressure in the storage tank and assumed complete adiabatic compression.
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Another metric that was used was the comparison of the maximum number of strokes predicted by the model vs. the experimental results. The prototype was used to run multiple tests at varying tank pressure levels to determine the amount of strokes the compressor could achieve. These results were compared to the model to determine the validity of the MATLAB code. The experimental results exhibited the same behavior as the model at the same tank pressure levels. The lower number of strokes in the experimental testing may be due to various frictional sources that were not included in the model such as internal friction of the piston and cylinder walls or due to pressure leakage from the crank case of the compressor.
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