scram jet design and oblique shock

In scram jets combustion occurs at super sonic air velocities. Oxygen is directly available from air and there is no need for tank to store oxygen. the velocities with which these engines run are very high about 10 -15 times sonic speed.

Intake of air matters a lot in this design . and it is a bit complex .

If the pressures with which air enter s the combustor increases we get high speeds .

In order to achieve high pressures the intake is designed in such a way to increase pressure. The main principle behind it being oblique shock occurrence which causes an increase in pressure and change in direction of flow .

The body of jet is provided with ramps (as shown in figure ) which are responsible for generation of oblique shock waves.the generation of oblique shock occurs at the tip of the ramp .the designing is done in such a way that the shock wave direction after meeting the ramp tips converge at the inlet of the intake of combustor and the flow is also directed towards the intake .

FUEL INJECTORS

In trying to keep up with emissions and fuel efficiency laws, the fuel system used in modern cars has changed a lot over the years. For most of the existence of the internal combustion engine , the carburetor has been the device that supplied fuel to the engine. But as the automobile evolved, the carburetor got more and more complicated trying to handle all of the operating requirements.

At first, carburetors were replaced with throttle body fuel injection systems. Gradually, as new engines were designed, throttle body fuel injection was replaced by multi-port fuel injection.

Fuel-injection management comprises all the components which are involved in transferring the fuel from the tank and into the combustion chamber:

• The low-pressure pump forces the fuel from the tank into the pressure chamber of the high-pressure pump.
• The high-pressure pump compresses the fuel.
• Mechanically or electronically triggered valves meter the correct amount of compressed fuel to the engine at the correct moment in time.
• The fuel is then injected into the combustion chamber through the nozzles

Here is a over view of common rail injection systems being produced by bosch which gives us an idea about their progress

1997:
First Common Rail system in the world for passenger cars.
Injection pressure: 1,350 bar.

1999:
Common Rail system for trucks.
Injection pressure: 1,400 bar.

2001:
2nd generation Common Rail for passenger cars makes diesel engines even more economical, cleaner, quieter and more powerful. Injection pressure: 1,600 bar.

2002:
2nd generation Common Rail for trucks gives lower emissions, improved fuel consumption and more power.
Injection pressure: 1,600 bar.

2003:
3rd generation Common Rail with rapid-switch piezo inline injectors for cars.
Advantages: up to 20 % lower emissions or up to 5 % more power or up to 3 % lower fuel consumption or up to 3 dB(A) less engine noise.
Injection pressure: 1,600 bar.