TurboSystems → Helpful information → Interesting facts
The average exhaust gas temperature at the turbine's rotor in diesel engines is 800 ° C and in petrol engines it can reach up to 1000 ° C. Such a temperature is sufficient to melt the window glass.
The new generation of turbocharger rotors can spin up to 220,000 rpm. For comparison, the Boeing 747 aircraft engine rotor spins about 7000 rpm.
The air entering the turbocharger rotor can travel at a speed close to the sound speed (340.3 m/s).
At medium engine speeds, a medium-sized turbocharger can suck 3.7 cubic meters of air per minute. That would be around the same volume as average minibus.
The turbocharger can spin from 20,000 rpm to 150,000 rpm in less than 1 second.
To balance the turbocharger, we need the precision: if we would match the permissible unbalance with a force of 2 kg, the 6 kg force acting on the turbocharger rotor would be the same as running a car with a brick attached to the wheel.
VGT - „VARIABLE GEOMETRY TURBINE”
For many years, turbocharger manufacturers compete with each other and develop their turbochargers. The main disadvantage of turbochargers is the "turbo lag". It is the time during which the turbocharger builds up pressure in the system. It is believed that the turbocharger switches on certain RPM, for example at 1500 or 2200 rpm, while in reality the turbocharger starts to rotate right after the engine starts, but due to the inertia of the axis and rotors, the turbocharger builds up pressure in the system later than you press the accelerator pedal. Driving a car with bigger turbo lag requires some skill in overtaking another car or quickly crossing the crossroads. All the time you need to plan that the car will not have power for a while.
Variable geometry turbochargers have been developed to reduce turbine lag. With the help of variable geometry, the exhaust gas speed is increased, thus the turbocharger's axes spin faster and build up pressure in the system. The torque of the engine increases and the engine torque increases evenly as the RPM rises. Driving a car with VGT is more convenient, moreover fuel consumption and harmful emissions are reduced.
So far, variable geometry turbochargers are installed (in serial production) only in diesel vehicles. In petrol engine cars, the exhaust gas temperature is higher than in diesel engines, which is why the durability of variable geometry decreases. In the serial production, no manufacturer has yet been determined to install a turbocharger with variable geometry.