Modern methods of turbocharging
PULSE CONVERTER SYSTEM:-
Concerning those pulse charging system due to long interval of air inlet and partial loss of air inlet (multi inlet turbine) which lead a low efficiency of turbine, in order to improve the performance of engine, pulse converting charging system is presented. Pulse converting system tries to keep the advantage of pulse system which is its high available energy and the unsteady flow at exhaust, meanwhile steady and effective flow condition can be obtained for turbine.
A real simple pulse converting system used for four cylinder engine is shown in the figure below
It uses conventional pulse manifold, using a carefully designed connecting piece to connect a manifold which has two branches to a single turbine. Through four cylinders connecting to an inlet of turbine, it totally avoids the interval of air inlet among exhaust pipes. Comparing to constant pressure system though inlet of turbine are different it avoids the situation of pulse system operating in low efficiency. The design of connecting piece makes the least transmission of pressure pulse from one pipe of the exhaust pipe to another, so it avoids that a cylinder's exhaust pipe breaks another cylinder scavenging process. This type of pulse converter are mostly used on medium speed engine especially 4 cylinder, 8 cylinder and 16 cylinder. If engine has cylinder we should use two pulse converter, each pulse converter converting an inlet of turbine.
TWO CHARGE TURBOCHARGING:-
This uses two large turbocharger set up parallel to each other. Each turbo supplies half of the cylinder with pre-compressed air.Each turbocharger is driven by half of the engine's spent exhaust energy.In most application the compressed air from both turbos is combined in common intake manifold and sent to individual cylinder.
SEQUENTIAL TURBOCHARGING:-
In this system a small turbo is used when the engine is running at lower RPM and at higher engine RPM turbocharging is switched to larger high flow turbocharger. The gas flow between the turbos is controlled using by-pass valve where operation modes are based on engine speed. During low to medium speeds, when available spent exhaust energy is minimal, only small turbocharger is active. During this period all of engine's exhaust energy is directed to the primary turbocharger only, providing the small turbo's benefits of a lower boost thresh hold, minimum turbo lag , and increased power output at lower engine speeds As RPM increases the secondary turbocharger is partially activated in order to pre-spool prior to its full utilization Once a preset engine speed or boost pressure is attained, valves controlling compressor and turbine flow through the secondary turbocharger are opened completely.
VARIABLE GEOMETRY TURBOCHARGER:-
These are a family of turbocharger usually designed to allow the effective aspect ratio(A/R ratio) of the turbo to be altered as condition change. This is done because optimum aspect ratio at low engine speed is very different from that at high engine speeds. If the aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressure, high pumping losses and ultimately lower power output. VGT has little movable vanes which can direct exhaust flow on to the turbine blades. The vane angles are adjusted via an actuator. The angle of vane vary throughout the engine RPM range to optimize turbine behavior.
Concerning those pulse charging system due to long interval of air inlet and partial loss of air inlet (multi inlet turbine) which lead a low efficiency of turbine, in order to improve the performance of engine, pulse converting charging system is presented. Pulse converting system tries to keep the advantage of pulse system which is its high available energy and the unsteady flow at exhaust, meanwhile steady and effective flow condition can be obtained for turbine.
A real simple pulse converting system used for four cylinder engine is shown in the figure below
TWO CHARGE TURBOCHARGING:-
This uses two large turbocharger set up parallel to each other. Each turbo supplies half of the cylinder with pre-compressed air.Each turbocharger is driven by half of the engine's spent exhaust energy.In most application the compressed air from both turbos is combined in common intake manifold and sent to individual cylinder.
SEQUENTIAL TURBOCHARGING:-
In this system a small turbo is used when the engine is running at lower RPM and at higher engine RPM turbocharging is switched to larger high flow turbocharger. The gas flow between the turbos is controlled using by-pass valve where operation modes are based on engine speed. During low to medium speeds, when available spent exhaust energy is minimal, only small turbocharger is active. During this period all of engine's exhaust energy is directed to the primary turbocharger only, providing the small turbo's benefits of a lower boost thresh hold, minimum turbo lag , and increased power output at lower engine speeds As RPM increases the secondary turbocharger is partially activated in order to pre-spool prior to its full utilization Once a preset engine speed or boost pressure is attained, valves controlling compressor and turbine flow through the secondary turbocharger are opened completely.
These are a family of turbocharger usually designed to allow the effective aspect ratio(A/R ratio) of the turbo to be altered as condition change. This is done because optimum aspect ratio at low engine speed is very different from that at high engine speeds. If the aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressure, high pumping losses and ultimately lower power output. VGT has little movable vanes which can direct exhaust flow on to the turbine blades. The vane angles are adjusted via an actuator. The angle of vane vary throughout the engine RPM range to optimize turbine behavior.
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