Write a short paragraph explaining the three following metho

Write a short paragraph explaining the three following methods for fueling a spark ignited internal combustion engine:

Naturally aspirated carbureted, electronic fuel injection via ports, and direct fuel injection.

Solution

Answer:

Naturally aspirated carbuteted engine

This is the earliest design where mixing of fuel and air during is accomplished by aspiration throgh venturi where jet of petrol(gasolene) flows due to suction created at throat of venturi as well at static head of petrol tank.The engine power is controlled by throttle which controls the air flow. The fuel amount is varied automatically in proportion to the throttle flow as the suction cteated at throat increases with increasing throttle flow. Since there is very little spraying action of the near atmispheric fuel jet, the thorough mixing of fuel and air does not happen in this design.

Electronic Fuel Injection

In this design fuel is transported from the fuel tanks via fuel lines and then pressurised before injection using fuel pumps. Often pressurised fuel rails are used to distribute the fuel to different cylinders. Fuel is often injected within the intake air, before intake valves. The amount of fuel to be injected is determined by the Engine Control Unit from the throttle position signal from sensor. Modern systems use a mass flow sensor for intake air, however other sensing options are available. After injection the fuel-air mixture is ignited with spark plugs.

Typically the EFI system includes the following components:

- Injectors

-Fuel pump

-Fuel pressure regulator

-Engine control unit

-Various sensors.

Due to pressurised spray the dispersion and mixing of fuel and air is better than carbureter design which in turn improves the fuel efficiency. Since the fuel spray nozzles are located away from the high temperature combustion chamber, the material quality can be lesser than direct injection, also maintenence effort is less.

Direct Injection

Here fuel in injected directly into the combustion chamber. Typically a common rail system is used. Here the fuel from the fuel tank is pressurised by pump and sent to a common rail, also called accumulator. The fuel is then sent through tubings to the injectors which inject into the combustion chamber. The header has a high pressure relief valve to maintain the pressure within, the excess fuel is returned to the fuel tank. Fuel is sprayed with the help of nozzles with needle valves which open and close with the help of solenoids. After injection the fuel-air mixture is ignited with spark plugs.

By virtue of better dispersion and homogeneity, the cylinder and piston are better cooled (sometimes by swirl action of intake air flow), permitting use of higher compression ratio, with resultant higher cycle efficiency. Also homogeneity permits use of leaner fuel-air mixture, improving the fuel efficiency. Costly nozzle materials are required because of hith temperature working condition, maintenance effort is also more.