2. Topics of Interest
Introduction to the liquid nitrogen vehicle
History
Justifying the use of liquid nitrogen vehicle
Cryogenic heat engines
Production of liquid nitrogen
Main components
Principle of operation
Open Rankine cycle
3. Topics of Interest
Advantages
Drawbacks
Solutions to drawbacks
Efficiency
Reason for not being commercialized
Conclusion
4. What is Liquid Nitrogen Vehicle?
It is a vehicle which uses Cryogenic fluid(liquid
nitrogen) as a working fluid.
Propulsion system is a cryogenic heat engine in
which a cryogenic substance is used as a heat sink.
CRYOGENICS
Cryogenic can be defined as the branch of the physics that deals with the study
of the production of very low temperature (below −150 °C, −238 °F or 123 K)
and the behavior of materials at those temperatures.
5. History
In 1997, the liquid nitrogen powered vehicles was
independently developed by University of North Texas (UNT)
and University of Washington (UW).
The propulsion systems in these vehicles were cryogenic heat
engines in which a cryogenic substance is used as a heat sink
for heat engine.
The vehicle (car) was named as LN2000.
It was a converted 1984 Grumman-Olson Kubvan mail
delivery van.
7. Why Nitrogen as a Vehicle Fuel?
High cost and limited availability of fossil fuels like petrol and
diesel.
Due to high level of pollution associated with the combustion
of fossil fuels the need of ZEV(Zero Emission Vehicle) has
been generated. (presently the battery powered electric vehicle
is the only commercially available ZEV but not successful due
to high initial cost, slow recharge and limited range).
And the most important is the huge availability of Nitrogen
gas(78% of air is nitrogen).
Note: According to Petroleum Conservation and Research Association
petroleum production will be at its peak in 2012 and is likely to
decrease after that.
8. Cryogenic Heat Engine
It is a engine which uses very cold substances to produce
useful energy.
There is always some heat input to the working fluid during the
expansion process.
9. Liquid Nitrogen(LN2)
Liquid Nitrogen is the cheapest, widely produced and most
common cryogen.
It is mass produced in air liquefaction plants
The liquefaction process is very simple.
Normal, atmospheric air is passed through dust precipitator
and pre-cooled.
11. Inter cooler
Atmospheric Dust Turbo
Precipitator pumps
Air passes
Expansion
Fractional
LN2
Insulated Nozzle
chamber
Distillation
Dewar Flask
Nitrogen cycle showing the production of liquid nitrogen
12. It is then compressed inside large turbo pumps to about 100
atmospheres(10.13 MPa).
Once the air has been cooled to room temperature it is allowed
to expand rapidly through a nozzle into an insulated chamber.
By running several cycles the temperature of the chamber
becomes low enough. The air entering it starts to liquefy.
Liquid nitrogen is removed from the chamber by fractional
distillation and is stored inside well-insulated Dewar flasks .
13. Main Components of the Engine:
A pressurized tank(24 gallon) to store liquid nitrogen.
Pressurant bottles of N2 gas substitute for a pump. The gas
pushes the liquid nitrogen out of the Dewar that serves as a fuel
tank.
A primary heat exchanger that heats (using atmospheric heat)
LN2 to form N2 gas, then heats gas under pressure to near
atmospheric temperature.
An Expander to provide work to the drive shaft of the vehicle.
An economizer or a secondary heat exchanger, which preheats
the liquid N2 coming out from the pressurized tank taking heat
from the exhaust.
16. Principle of Operation:
LN2 at –320oF (-196oC) is pressurized and then vaporized in a
heat exchanger by ambient temperature of the surrounding air.
This heat exchanger is like the radiator of a car but instead of
using air to cool water, it uses air to heat and boil liquid
nitrogen.
Liquid N2 passing through the primary heat exchanger quickly
reaches its boiling point.
The N2 expands to a gas with a pressure of 150 KPa.
18. The pressurized N2 gas drives the motor.
The only exhaust is nitrogen, which is major constituent of our
atmosphere.
Energy+N2(l)-->N2(g)
Hence, there is no pollution produced by running this car.
19. Advantages over electric cars:
A liquid nitrogen car is much lighter and refilling its tank takes
only about 10-15 minutes.
The exhaust produced by the car is environmental friendly.
A cryogenic car could have three times the range of an electric
car of the same weight and no battery disposal concerns .
20. Drawbacks:
The N2 passing through the tubes of the heat exchanger is so
cold that the moisture in the surrounding air would condense
on the outside of the tubes, obstructing the air flow.
Then there's the safety issue. Should a nitrogen car be kept in a
poorly ventilated space and, if the Nitrogen leaks off, it could
prove fatal.
Turning N2 gas into a liquid requires a lot of energy. So while
cryogenic cars have zero emissions, they rely on energy
produced at emission generating power plants.
21. Probable Solutions:
A tube within a tube design.
N2 passes back and forth inside a set of three nested tubes.
By the time it reaches the outermost tubes, the N2 is warm
enough that the exterior wall of the tube remains above the
freezing point of water.
Route the exhaust from the fossil fuel power plants through
cryogenic plants, so that the pollutants and the greenhouse
gases could be condensed for later disposal
22. Efficiency:
The LN2 car can travel 79 miles(127.58 km) on a full 24
gallon(90 liter) tank of liquid nitrogen going 20 MPH.
Its maximum speed is over 35 MPH.
23. Why not commercialized?
Even though the technology is 10 to 12 years old, still it has not
come to the market for two reasons.
Safety issues have not been sorted out as yet.
Lack of funds for research.
24. Conclusion:
In a real sense, the more such vehicles are used, the cleaner
the air will become.
In addition to the environmental impact of these vehicles,
refueling using current technology can take only a few
minutes, which is very similar to current gas refueling
times.
Extra research work is needed to utilize the most of the
available energy
