Nowadays turbocharged engine is very hot, with more power than the same displacement naturally aspirated engine, by many people of all ages. The turbocharger as a core part of its evolution is constantly upgraded, as nowadays some of the equipment to launch a single twin-scroll turbocharger turbine. Single turbo twin-scroll turbocharger and the general principles of what would be different? And how about the engine performance impact? Let us resolve it.
Single twin-scroll turbocharger turbine structure
Single turbo twin-scroll turbocharger with common structure similar turbocharger, exhaust gas can be simply understood as the entrance to a general increase in turbine exhaust passage, except that the turbine is driven by the exhaust gas of the two channels.
Exhaust gas turbocharger boost mode?
Exhaust gas turbocharger on the engine intake supercharger There are two main ways that the constant pressure and pulse supercharger boost. Is the constant-pressure turbocharger turbine inlet pressure of the exhaust duct is almost constant, even though the exhaust gas of each cylinder alternately, but the pulse voltage is superimposed and the effect of the exhaust pipe, the inlet pressure of the turbine is almost change.
Pressurized pulses, each cylinder is discharged through the exhaust gases and at different moments of the forming pulse, the pressure before the turbine is changed, the pressure wave in a pulse manner to drive a turbine. Impulse supercharging turbocharger can achieve fast response characteristic (especially at a lower speed), because this time the pulse of the strongest, whereas in the case of constant pressure supercharging turbo mode after the pressure difference is relatively small.
How to exhaust pulse generation?
We know that the working cylinder four-stroke engine, only the exhaust stroke exhaust gases, the pressure before the turbocharger the exhaust gas passage of the cylinder only when the exhaust stroke is the largest. In a multi-cylinder engine, the exhaust gas due to the different time of each cylinder, and therefore the exhaust gas passage before the turbocharger the exhaust gas pulses will produce corresponding. Such as single-cylinder engine, in theory, each crankshaft rotation 720 ° in there 180 ° for exhaust. The following figure with a very simplified way to display a pressure situation cylinder engine exhaust gas turbocharger ago.
In the four-cylinder engine, since the crankshaft rotates two turns after completion of the respective all-cylinder exhaust gas loop, so produced within the 720 ° of the crank angle of the four pressure waves, uniform distribution of the ignition interval of 180 ° crank angle intervals. In this process, the pressure wave superposed on each other when the cylinder pressure falls to a next cylinder pressure has been increased.
Superimposed effect will make the minimum pressure and maximum pressure difference significantly reduced, and therefore the pressure wave acting on impulse turbine also will be reduced, leading to the exhaust turbocharger boost pulse within reduced.
Single twin-scroll turbocharger turbine produces larger pulse supercharger
In a single twin-scroll turbine engine exhaust system, the exhaust duct is divided into two groups, such as the four-cylinder engine in the cylinder group 1 and 4, the cylinders 2 and 3 as a group, so that according to the ignition order, one channel the cycle interval of 360 ° crank angle, so even in the case of superimposed can produce a larger pulse supercharging, better utilization of the kinetic energy of the exhaust gas.
When the engine load is changed, the exhaust gas temperature and pressure changes can be quickly transmitted to the turbine, the turbine directly reflected by the compressor, so that a faster response of the turbocharger to changes in engine load, so that the engine can be improved better the acceleration characteristics and torque characteristics (low speed high torque can be generated).
Single twin-scroll turbo engine intake and exhaust design more efficient
The above mentioned four-cylinder engine cylinder 1 and the cylinder 4, the cylinder 2 and the cylinder 3 are integrated in one channel, why should the cylinder 4 and the cylinder 1 together with the set, rather than the set of cylinders and the cylinder 2 together with? In fact, there is another advantage to do so. Autoboss V30 Elite Scanner For Multi-brand Vehicles for sale
We know that the four-cylinder engine firing order is 1-3-4-2, the general turbocharger (single turbo single scroll) is an exhaust manifold of an exhaust pipe of all the cylinders together and to the exhaust pooled and then to push the turbine.
What's so wrong with that? When the work of a single cylinder, the resonant pulse generated by the exhaust gas will affect the efficiency of the exhaust gas of the other cylinder. When working as a cylinder, there is a period of time the cylinder intake valve and exhaust valves are in the open state (valve overlap). If the ignition interval between the adjacent two cylinder exhaust pipe connected when the valve overlap causes the exhaust gas back into the preceding cylinders. Before a cylinder intake air reduction, then the next cycle of the total power will drop.
And in a single twin-scroll turbine engine exhaust system, the two cylinders adjacent to the ignition twenty-two separate exhaust duct (1 and 4, a group, a group 2 and 3), so that when the cylinder 3 is completed when the exhaust acting , a cylinder is entering the intake stroke, due to a cylinder and 3-cylinder exhaust pipe is not connected, so the three-cylinder exhaust does not affect a cylinder intake effect (other empathy), so the two adjacent ignition cylinder intake and exhaust without interference effects of intake can increase the displacement of each cylinder, thus effectively improving engine efficiency.
Single twin-scroll turbo-charged engine characteristics
BMW N20 turbo engine uses a single twin-scroll turbocharger technology, 1250 at low speed can reach 350Nm of peak torque (high power version), and can be continued until the 4800 revolution, covering almost daily driving use to the speed range. Autoboss V30 Elite Scanner
Single turbo twin-scroll turbocharging system, the ignition timing according to engine exhaust pipes adjacent cylinder exhaust pipes were divided into two groups to promote the turbine work, have a stronger pulse supercharger and exhaust more fully. Compared to ordinary turbocharged engine, single twin-scroll turbo engine effectively relieve hysteresis at low speeds, making the engine's peak torque outbreak earlier, better fuel economy.