Q1.What is advantage and disadvantage of LPG ?

Advantages and Disadvantages of LPG

Liquefied petroleum gas has higher potential as an alternate fuel for IC engines. The advantages and disadvantages of using LPG are

Advantages :

1. LPG contains less carbon than petrol. LPG powered vehicle produces 50 per cent less carbon monoxide per kilometre, though only slightly less nitrogen compounds. Therefore emission is much reduced by the use of LPG.
2. LPG mixes with air at all temperatures.
3. In multicylinder engines a uniform mixture can be supplied to all cylinders.
4. Since the fuel is in the form of vapour, there is no crankcase dilution.
5. Automobile engines can use propane, if they have high compression ratios (10:1).
6. LPG has high antiknock characteristics.
7. Its heat energy is about 80 per cent of gasoline, but its high octane value compensates the thermal efficiency of the engine.
8. Running on LPG translates into a cost saving of about 50%.
9. The engine may have a 50 per cent longer life.
10. LPG can be used for various applications, including heating, cooking, and as a fuel for vehicles.

Disadvantages :

1. Engines are normally designed to take in a fixed volume of the mixture of fuel and air. Therefore LPG will produce 10 per cent less horse power for a given engine, at full throttle.
2. The ignition temperature of LPG is somewhat higher than petrol. There- fore running on LPG could lead to a five per cent reduction in valve life.
3. A good cooling system is quite necessary, because LPG vaporizer uses engine coolant to provide the heat to convert the liquid LPG to gas.
4. The vehicle weight is increased due to the use of heavy pressure cylinders for storing LPG .
5. A special fuel feed system is required for liquid petroleum gas.
6. While LPG is convenient to store and transport, there are safety concerns related to its flammability and the need for proper handling.
7. Incomplete combustion of LPG can produce carbon monoxide, a potentially harmful gas.

Q.2.What is advantage and limitations of Liquid-Cooling System ?

Advantages of Liquid-Cooling System

1. Compact design of engines with appreciably smaller frontal area is possible.
2. The fuel consumption of high compression liquid-cooled engines are rather lower than for aircooled ones.
3. Because of the even cooling of cylinder barrel and head due to jacketing makes it possible to reduce the cylinder head and valve seat temperatures.
4. In case of watercooled engines, installation is not necessarily at the front of the mobile vehicles, aircraft etc. as the cooling system can beconveniently located wherever required. This is not possible in case of air-cooled engines.
5. The size of engine does not involve serious problems as far as the design of cooling systems is concerned.
6. In case of air-cooled engines particularly in high horsepower range difficulty is encountered in the circulation of requisite quantity of air for cooling purposes.

Limitations

1. This is a dependent system in which water circulation in the jackets is to be ensured by additional means.
2. Power absorbed by the pump for water circulation is considerable and this affects the power output of the engine.
3. In the event of failure of the cooling system serious damage may be caused to the engine.
4. Cost of the system is considerably high.
5. System requires considerable maintenance of its various parts.

Q.3.What is advantage and limitations of Air-Cooling System ?

1. The design of the engine becomes simpler as no water jackets are required. The cylinder can have identical dimensions and be individually detachable and therefore cheaper to renew in case of accident etc.
2. Absence of cooling pipes, radiator, etc. makes the cooling system simpler thereby has minimum maintenance problems.
3. No danger of coolant leakage etc.
4. The engine is not subject to freezing troubles etc., usually encountered in case of water cooled engines.
5. The weight of the air-cooled engine is less than that of water-cooled engine, i.e., power to weight ratio is improved.
6. In this case, the engine is rather a self-contained unit as it requires no external components like radiator, header, tank etc.
7. Installation of air-cooled engines is easier.

Limitations

1. Can be applied only to small and medium sized engines.
2. In places where ambient temperatures are lower
3. Cooling is not uniform.
4. Higher working temperatures compared to water-cooling.
5. Produce more aerodynamic noise.
6. Specific fuel consumption is slightly higher.
7. Lower maximum allowable compression ratios.
8. The fan, if used absorbs as much as 5% of the power developed by the engine.