Lower exhaust emissions of large bore diesel engines without after treatment, can be realized by increasing the mean effective pressure. One way to achieve a higher m.e.p. is to increase the boost pressure of the turbocharger however standard turbo designs are already at or approaching the limit of their capability to go from atmospheric pressure to the desired boost pressure in one unit: the solution is therefore to use two turbo stages. Simply, it comprises a low pressure turbine feeding via an inter cooler a second high pressure turbine which in turn passes through a second inter cooler to the engine. Control of a two stage turbo system including the suppression of compressor surging.is complex and is effected with the aid of variable nozzle rings (VTA) and bypasses. MAN Diesel & Turbo have recently announced their own series of two-stage turbos called the New TCX Generation. Using a configuration with the turbos at 90 degrees to each to provides a compact solution and reduce the amount of piping.
In the relentless quest for lower exhaust emissions of large bore diesel engines without after treatment, increasing the mean effective pressure is a way of accomplishing it .
One way to achieve a higher m.e.p. is to increase the boost pressure of the turbocharger however standard turbo designs are already at or approaching the limit of their capability to go from atmospheric pressure to the desired boost pressure in one unit: the solution is therefore to use two turbo stages.
A sequential turbo charging (STP) configuration has been around for several years with the second turbo bringing additional charging when required. This arrangement also has its limitations hence the introduction of the two stage turbo concept. Simply, it comprises a low pressure turbine feeding via an inter cooler a second high pressure turbine which in turn passes through a second inter cooler to the engine. The exhaust gases powering the turbos pass first of all through the high pressure turbine then the low pressure turbine. Control of a two stage turbo system including the suppression of compressor surging.is complex and is effected with the aid of variable nozzle rings (VTA) and bypasses.
MAN Diesel & Turbo have recently announced their own series of two-stage turbos called the New TCX Generation. They are based on their established TCA/TCR series and use a novel layout to achieve a compact unit. As two inter coolers are required by the system, with one located between the chargers, an unusual configuration with the turbos at 90 degrees to each other is used. This provides a compact solution and reduces the amount of piping.