Assignment 6

Ans.

Following are the various tubocharger used in GT tutorials:

1. Fixed geometry

2. Fixed geometry Twin entry turbine

3. Waste gate turbocharger

For the given tutorial compressor maps are:

For tutorial 6:

1. Compressor operating point on pressure ratio vs. mass flow rate plot: Operating speed of compressor is in 5949 rpm region.

2. Compressor effciency map: Efficiency of compressor is 72%.

Looking at compressor maps it is observed that operating point is very near to the safe limit.

3. Turbine map speed map:

4. Turbine effciency map:

Operating point is in dot figure in pressure and effciency map.

For tutorial 7:

1. Compressor speed map: Operating points lies in choking zone

2. Effciency map:

Turbine maps:

3. Turbine speed map:

4. Turbine effciency map:

In second compressor and turbine maps it is observed that compressor operates in the choking zone. We know that compressor choking occur when mass flow rate of air is very high. Therefore it is more optimum to go for VGT turbocharger in this case. Where flow area can be charged by varing rack position.

VGT turbocharger (Tutorial):

In VGT tubocharger model, we use rack controller. With helps in orienting the blade in tubocharger as per requirement.

Above is the image of VGT turbocharger controller. Input signal is boost pressure from intake manifold and which is to be controlled by varing rack position in turbine. For this XYZ plot is given where target boost pressure is mentioned for given speed and fuel injection quantity.

Further injector rate is controlled by the controller, where target bmep is set, on the base of which injection quantity is set.

Above figure shows how for the given target boost pressure, the rack position is changed.

Above figure is for Diesel injector controller i.e how the main injection quantity is changed in order to get desired bmep.