Assignment 7

1. AIM:

• To Explore tutorial number 9 and write a detailed report (50 marks)
• To Build FRM Model for following configuration using FRM builder approach (50 marks)
• Bore 102 mm stroke 115 mm CR 17
• No of cylinder 6
• CI engine
• Twin Scroll Turbine
• GT Controller
• Run all cases

2. METHODOLOGY:

Challenge 1

FRMs are used to achieve fast run times by :

• Increasing the simulation time step size
• Decreasing the number of calculations per time step.

These 2 possibilities are accompolished by combining various flow volumes and reducing the total number of subvolumes. It also provides the provision for a larger time step size by increasing the effective subvolume length.

In this challenge FRM converter is used to convert detailed model to FRM. The entire process is carried out in the following 8 steps. In this approach all the small volumes are lumped into a single volume.

STEP 1

In this step a detailed 4 cylinder GDI Turbo model with 4 valve cylinder, 2 intakes and exhaust ports, with a separate runner for each cylinder is taken.

STEP 2

In this step the two exhaust valves and ports are lumped to a single entity for each cylinders. In addition, small subvolumes after Turbine are lumped into single volume.

STEP 3

Like exhaust, the intake side is also converted to single valve and port for each cylinder

STEP 4

Compressor and intercooler subvolumes are lumped into larger volume

STEP 5

Airbox in and Airbox along with pipe connections are removed

STEP 6

Exhaust system is once again reduced to single runner connected to turbine.

STEP 7

Cylinder Slaving: Cylinder - override value of cylinder slaving option to Master

STEP 8

Real time Solver - requires GT-RT licence

Inference: A detailed model can be converted to FRM model using the above sequence of steps such that the speed of run takes minimum cycle time.

Challenge 2

• To Build FRM Model for following configuration using FRM builder approach (50 marks)
• Bore 102 mm stroke 115 mm CR 17
• No of cylinder 6
• CI engine
• Twin Scroll Turbine
• GT Controller

1D Simulation Modelling

Twin scroll – heavy duty and no. of cylinders >4 - for this problem we have taken twin scroll

Detail model of the diesel engine is depicted below:

3. RESULTS AND DISCUSSION

Case 1: 4000 rpm

rev/sec --> 4000/60=66.66rev/sec

cycles/sec --> 66.66/2=33.33cycles/sec

1/33.33 = 0.03 sec to complete one cycle or sec/cycle

then for 1000 cycles it will take 30 sec = Actual time

FRM the results are obtianed in short time in comparison to a detailed model.

The 1D FRM simulation is run For all 25 cases .

PLOT

ompressor Efficiency Map

Inference: It is envisaged from the figure that there is a downward trend visbile in the oparating points when moved from 100% load to 20% load.

Turbine Efficiency Map

Inference: It is envisaged from the figure that all the oparating points were found to lie in the high efficiecny zone.

In cylinder Pressure

Inference: It is envisaged from the figure that as the load decreases from 100% to 20%, in cylinder pressure decreases proportionately.