Ramjet engines, How do they work?

at present brahmos is the fastest and only supersonic cruise missile on the planet during its cruise it breaks the sound barrier by traveling three times faster than a sound wave and no known weapon system can intercept it due to its speed in the first stage solid boosters power this missile and the second stage features the ramjet engines we'll learn more about these intriguing engines in this video we thank brilliant.org for supporting this video more about lessex brilliant collaboration towards the end of this video to understand ramjet technology we first need to understand the concept of shock waves everybody is familiar with the ripples that are created in water when an object is thrown into it these ripples travel uniformly right now take a look at this interesting scenario suppose a boy is pulling a tennis ball towards him the movement of the source produces ripples that are not concentric isn't that interesting the same effect can happen with sound waves during aircraft movement here the sound waves are taking the place of the water ripples and the aircraft is taking the place of the tennis ball in this scenario the sound ripples will obviously travel at the speed of sound but here's a brain teaser for you what will happen if the aircraft moves at the speed of sound obviously the sound waves won't be able to move forward so if you move along with the aircraft it will look as if the sound waves are stuck at the front forming a sound barrier during world war ii the sound barrier was assumed to be an invisible wall due to the aircraft experiencing high drag however what if the aircraft moves faster than the sound waves the concentrated waves at the front of the aircraft will suddenly form a distributed ripple pattern as shown the aircraft needs to apply more thrust during this transition the distributed pattern has a conical shape the interesting thing is that a very narrow volume with a thickness of 200 nanometers and high temperature and pressure is formed on this conical shape the pressure in this narrow region is almost 29 times that of the atmospheric pressure this region is known as a shock wave why is the shock wave formed when the airplane moves at a speed greater than the speed of sound this result is because in fluid the information travels at the speed of sound when the airplane travels faster than sound the air volume shaded in red color has absolutely no information about the disturbance the moving object is making however inside the green region the disturbance in the fluid happened with prior information when the disturbed fluids suddenly interact with fluid particles in the red region which has no information about what is going on a shock gets formed in the boundary shock waves can cause harm to a human body however even though these high pressure waves are disastrous opportunity lies in the middle of difficulty using the concept of the shock wave let's understand how a ramjet engine works ramjet engines have a very simple geometry they have only three main stationary parts a diffuser region at the entrance a combustion chamber in the middle and a nozzle at the exit the duty of the diffuser is to increase pressure and temperature of the air the ramjet engines will work only in supersonic conditions since the flow is supersonic the scientists tweaked the shock wave concept to increase the diffuser pressure let's see how the shock waves get generated from many points of this cylindrical object remember in a shock wave the high pressure and temperature is there only in a narrow region however when many such shock waves club together something interesting happens you can see at the inlet a conical region is formed with no effective shock wave at all this will be a low pressure region it is also clear a high pressure conical wall is getting generated at the inlet region what about the remaining volume to understand the remaining volume condition let's take a cross section of the cones at different lengths you can see a flower-like shape if you increase the number of cones this flower will fill the entire area remember the number of shock cones getting generated from a circle edge is infinite this area filling is true for any length which means after the initial void cone a thick volume of high pressure and temperature air is formed inside the cylinder in short it forms automatic compression action with the help of shock waves this is the ram effect this high pressure and high temperature air can create effective combustion in the combustion chamber hydrogen is commonly used as fuel for ramjet engines the combustion chamber further increases the gas temperature and also the fluid velocity according to newton's third law the greater the exhaust jet speed the more thrust the rocket derives to increase the speed of the jet further a converging diverging nozzle is also added at the exit even though this simple diffuser arrangement achieves a very high pressure boost if the combustion pressure exceeds limits the shock front will be blown out resulting in compressed air spilling out around the front of the tube this spill limits the speed of the ramjet to 1.2 mach scientists didn't stop here they further improved the ram effect with the help of an aerodynamically designed inner body in this new geometry you can see that the area allocated for the air is actually decreasing along with the flow for supersonic flow when the area decreases the pressure increases in ramjets the majority of the pressure rise happens due to the shock effect and because of a concept called oblique shock wave when air hits the nose of the inner body it deflects with some angle forming an oblique shock wave this oblique shock wave hits the outer tube deflects multiple times and is finally terminated by a normal shock wave in this method the air spillout does not happen and scientists were able to achieve a high mach number for the ramjet engine now let's learn a little more about the combustion chamber design of ramjet engines the airflow speed through the ramjet is so high that the mixing of fuel completes within two to five milliseconds for complete mixing of fuel an air flame holder is used which helps to maintain continuous combustion it also stops the flame from blowing out by sheltering it ramjets are the most efficient in the speed range of mach 3 to mach 6. when traveling at low speed the thrust isn't sufficient to overcome the drag as a result the stand-alone ramjet engine is not feasible it needs the solid booster to propel the missile towards supersonic speeds the ramjet does not contain any moving parts unlike jet engines before you leave please make use of brilliant.org lesix collaboration and get a discount of 20 percent brilliant has recently upped the interactivity on their platform to a new level check out this interactive lesson on the center of mass for example this is an example of brilliant newly updated scientific thinking course follow the link given below and be a brilliant and creative engineer we hope you enjoyed the amazing technology of the ramjet engines see you next time

Channel: Lesics

Views: 5,395,814

Keywords: Ramjet engine, shock wave, ram effect

Id: kHSJiO_Fvvw

Length: 7min 46sec (466 seconds)

Published: Sat Aug 28 2021