We usually read in brochures of diesel cars, VGT or might have heard in fast and furious series the term: Turbochargers! but what exactly are they and how they work is a good question! Few car enthusiasts might be knowing something about it but in this blog, we will talk about anything and everything for Turbochargers. In this blog we will cover the basics of turbochargers, their types, cooling methodologies and finally applications. So, let's start!
Well in simple words, a turbocharger is a forced induction device i.e. it converts the linear motion of exhausts gas out from the exhaust manifold of the engine and converts it into rotary motion of turbine which in turn increases the air-intake in the inlet manifold for better performance of the engine. As we know, more air means more perfect fuel combustion which in turn increases mechanical efficiency!
The reaction involved inside combustion chamber of iso-octane with oxygen is:
C8H18 + 12.5 O2 ------ 8 CO2 + 9 H2O
As, can be seen in the above equation, for every mole of iso-octane/fuel; 12.5 moles of pure oxygen is required to completely burn the fuel else:
C8H18 + 10 O2 ------ 8 CO2 + 4 H2O + 5 H2 or even,
C8H18 + 5 O2 ------ 4 CO2 + H2O + CO + 3 CH4 + 2 H2
if the fuel if not burned properly, then there will be carbon monoxide, methane and unburned hydrogen which escape to atmosphere and is not good for environment. There are 2 air-fuel mixtures: 1) Lean i.e. more amount of air than usual 14.7:1 stoichiometric air-to-fuel ratio (AFR) or 2) Rich i.e. more amount of fuel in AFR. Well, they are there in Automobile dictionary for some reason. The reason is, lean AFR will result in more mechanical efficiency and cleaner exhaust while richer AFR will provide with more torque. But, more of something is also dangerous, the lean or rich AFR must be set optimally for best results! In an un-tuned turbocharged engine, the AFR is overly-lean which increases probability of knocking so in such-cases the AFR is made richer!
Now, there are various types of turbochargers (and I mean turbochargers; don't mix it up with superchargers or twin-chargers). The various types are:
1) Twin-Turbo - which means that two different turbochargers are used sequentially or parallel. If the turbos are parallel, it means the exhaust from different cylinders split into each i.e. let's say in a V6 arrangement: the cylinders 1,3,5 will be connected to 1st turbo while cylinders 2,4,6 will be connected to 2nd turbocharger! The main benefit of connecting two parallel turbos is that, the turbo-lag is reduced considerably while reducing the size they take up in the chassis; the other arrangement is to connect twin-turbo sequentially. This arrangement usually uses two different sized turbos, first a small turbo to reduce initial turbo lag and second big turbo to provide peak performance during full throttle, that is also the reason they are called as 2-stage twin turbo!
2) Twin-Scroll - or divided turbochargers instill the properties of 2-stage turbo into 1. The twin-scroll turbocharger has 2 exhaust-inlet manifolds and 2 nozzles. The sharp angled nozzle is for quick response and reduction in turbo-lag while the other division is for peak performance.
3) Variable Geometry - The Variable Geometry Turbocharger or VGT uses multi vane nozzle to control the exhaust-air flow to turbin and uses an actuator to control the diameter opening of nozzle. This gives a optimal power curve throughout the size which helps reduce lag without compensating for either boosted acceleration or boosted torque at peak revs!
Well, they might put you racing but without the underlying accessories, you might wanna race in tonight's race because you might loose your engine or blow off your car!
1) Intercooler: It is the most useful and essentially the most required addition you might want to install with your turbocharger! When, the air is forced into the inlet-manifold its pressure and temperature increases, thus reducing the density of oxygen in the air-fuel mixture thus, to optimise it an air charge intercooler is fitted with every turbocharger to increase the density of the air-fuel mixture and increase efficiency of the turbo-charger, also while bringing temperature under control.
2) Water Injection system: though not-popular and even very cumbersome, the water injection system is an alternative to intercooler which reduces the temperature of inlet-air through injecting water, this system was used in various automobile and aircraft applications.
3) External Waste Gate: A wastegate is a solenoid operated device that redirects excess of exhaust air away from turbine so as to regulate the power output of a small turbocharger and save engine and turbocharger from excess wear and breakdown.
4)Dump Valve: also anti-surge valve or blow off valve is a auto-pressure release valve that reduces the pressure when suddenly the throttle valve is closed in a wide-open throttle engine system. When the throttle is closed, the compressed air has no exit and without dump valve might result catastrophic in nature that is why the dump valve is an required accessory in turbochargers.
Now, since we've talked about basic working of turbo, its types, additions, then now it is right time to talk about the applications. The turbochargers have been used widely across all locomotives from production road cars to aircrafts.
1) Petrol Engines: Since 1962 Oldsmobile Jetfire Turbo to 2014 Mclaren P1, all possess petrol turbocharged engines which increase their power output by many folds.
2) Diesel Engine: The application of turbochargers in diesel engines came in 1978's with the Mercedes 300SD which drastically improved the fuel efficiency, mechanical efficiency, and driveability of diesel cars.
3) Aircrafts: Otto as well as Brayton cycle engines, both require forced induced air in one way or another; as altitude increases inversely, the density of oxygen in air increases thus making it difficult for engine to aspire, thus since 1920's research on using turbochargers with aircraft's rotary spark ignition engine started! the same concept of turbochargers is used in brayton cycle engines also where the air is compressed axially rather than using a centrifugal system.
Apart from these main uses, turbochargers have been extensively used in motorcycles, trucks, marine and land machinery etc.
Well in simple words, a turbocharger is a forced induction device i.e. it converts the linear motion of exhausts gas out from the exhaust manifold of the engine and converts it into rotary motion of turbine which in turn increases the air-intake in the inlet manifold for better performance of the engine. As we know, more air means more perfect fuel combustion which in turn increases mechanical efficiency!
The reaction involved inside combustion chamber of iso-octane with oxygen is:
C8H18 + 12.5 O2 ------ 8 CO2 + 9 H2O
As, can be seen in the above equation, for every mole of iso-octane/fuel; 12.5 moles of pure oxygen is required to completely burn the fuel else:
C8H18 + 10 O2 ------ 8 CO2 + 4 H2O + 5 H2 or even,
C8H18 + 5 O2 ------ 4 CO2 + H2O + CO + 3 CH4 + 2 H2
if the fuel if not burned properly, then there will be carbon monoxide, methane and unburned hydrogen which escape to atmosphere and is not good for environment. There are 2 air-fuel mixtures: 1) Lean i.e. more amount of air than usual 14.7:1 stoichiometric air-to-fuel ratio (AFR) or 2) Rich i.e. more amount of fuel in AFR. Well, they are there in Automobile dictionary for some reason. The reason is, lean AFR will result in more mechanical efficiency and cleaner exhaust while richer AFR will provide with more torque. But, more of something is also dangerous, the lean or rich AFR must be set optimally for best results! In an un-tuned turbocharged engine, the AFR is overly-lean which increases probability of knocking so in such-cases the AFR is made richer!
Now, there are various types of turbochargers (and I mean turbochargers; don't mix it up with superchargers or twin-chargers). The various types are:
1) Twin-Turbo - which means that two different turbochargers are used sequentially or parallel. If the turbos are parallel, it means the exhaust from different cylinders split into each i.e. let's say in a V6 arrangement: the cylinders 1,3,5 will be connected to 1st turbo while cylinders 2,4,6 will be connected to 2nd turbocharger! The main benefit of connecting two parallel turbos is that, the turbo-lag is reduced considerably while reducing the size they take up in the chassis; the other arrangement is to connect twin-turbo sequentially. This arrangement usually uses two different sized turbos, first a small turbo to reduce initial turbo lag and second big turbo to provide peak performance during full throttle, that is also the reason they are called as 2-stage twin turbo!
2) Twin-Scroll - or divided turbochargers instill the properties of 2-stage turbo into 1. The twin-scroll turbocharger has 2 exhaust-inlet manifolds and 2 nozzles. The sharp angled nozzle is for quick response and reduction in turbo-lag while the other division is for peak performance.
3) Variable Geometry - The Variable Geometry Turbocharger or VGT uses multi vane nozzle to control the exhaust-air flow to turbin and uses an actuator to control the diameter opening of nozzle. This gives a optimal power curve throughout the size which helps reduce lag without compensating for either boosted acceleration or boosted torque at peak revs!
Well, they might put you racing but without the underlying accessories, you might wanna race in tonight's race because you might loose your engine or blow off your car!
1) Intercooler: It is the most useful and essentially the most required addition you might want to install with your turbocharger! When, the air is forced into the inlet-manifold its pressure and temperature increases, thus reducing the density of oxygen in the air-fuel mixture thus, to optimise it an air charge intercooler is fitted with every turbocharger to increase the density of the air-fuel mixture and increase efficiency of the turbo-charger, also while bringing temperature under control.
2) Water Injection system: though not-popular and even very cumbersome, the water injection system is an alternative to intercooler which reduces the temperature of inlet-air through injecting water, this system was used in various automobile and aircraft applications.
3) External Waste Gate: A wastegate is a solenoid operated device that redirects excess of exhaust air away from turbine so as to regulate the power output of a small turbocharger and save engine and turbocharger from excess wear and breakdown.
4)Dump Valve: also anti-surge valve or blow off valve is a auto-pressure release valve that reduces the pressure when suddenly the throttle valve is closed in a wide-open throttle engine system. When the throttle is closed, the compressed air has no exit and without dump valve might result catastrophic in nature that is why the dump valve is an required accessory in turbochargers.
Now, since we've talked about basic working of turbo, its types, additions, then now it is right time to talk about the applications. The turbochargers have been used widely across all locomotives from production road cars to aircrafts.
1) Petrol Engines: Since 1962 Oldsmobile Jetfire Turbo to 2014 Mclaren P1, all possess petrol turbocharged engines which increase their power output by many folds.
2) Diesel Engine: The application of turbochargers in diesel engines came in 1978's with the Mercedes 300SD which drastically improved the fuel efficiency, mechanical efficiency, and driveability of diesel cars.
3) Aircrafts: Otto as well as Brayton cycle engines, both require forced induced air in one way or another; as altitude increases inversely, the density of oxygen in air increases thus making it difficult for engine to aspire, thus since 1920's research on using turbochargers with aircraft's rotary spark ignition engine started! the same concept of turbochargers is used in brayton cycle engines also where the air is compressed axially rather than using a centrifugal system.
Apart from these main uses, turbochargers have been extensively used in motorcycles, trucks, marine and land machinery etc.
