1.

What should the effect be on the engine if the primary failure was that the main flow nozzle was partly destroyed. Should the engine surge. Should we get an increase or decrease in any of the rotor speeds?

Would we expect any other things to happen that the pilots might recognise and that could verify that the nozzle was the main fault?

The engine are torn down and it is found that the variable guide vanes of the first stage of the compressor are turned to a closed position, (as if the engine where running at idle condition). The vanes must have been turned early in the accident, i.e. at full speed of the rotor, as they have been turned before any damages have occurred at the house to which the blades now are closely locked.

2.

Can this fault be the primary reason for the accident? What should happened if the guide vanes are closed when the compressor is running at full speed? Is there a risk of surge. Can we expect choking in any of the stages. Can any of the cascades be stalled. Etc. Should any of the rotor speeds be changed in a specific way by this error? Try to describe all the effects you could think would result.

Around the fuel injectors swirlers are located. Several of these swirlers were destroyed.

3.

Can this be a reason for the accident? What effects should we expects to see if the swirlers are destroyed? Will the combustion continue? Is any part of the combustor or turbine expected to be overheated? Should we expect to find unburned fuel in some areas, and in that case where (maybe close to the nozzle)?

Try to explain, from the knowledge of how the combustor is designed and supposed to work, how a failure of the swirlers can be detected.

In analyses after failures, metallurgic analyses are usually always performed. From these it is possible to estimate operating temperatures of the materials and then determine if overheating has occurred.

4.

What turbine inlet temperature should we expect for this engine? We may assume that the engine is designed to be close to optimal. It must be a fairly new engine as the bypass ratio is so high. This implies that component efficiencies must also be high.

Try from the knowledge of FPR and BPR and your analysis to estimate the cycle, in form of OPR and TIT. (The values you obtain will be compared to the values given by the manufacturer. In this way it is possible to get an impression if the engine is well designed or stressed, as far as cycle is concerned.)

5.

Cascade blades are designed differently in compressors and turbines. This is partly due to different circumstances like the large turning in turbines and the limited turning in compressors. Why do we see such a large difference in turning for the two cases?

The blade profile can be designed using standard profiles like C4 and T4 but more often they are designed just using circular arcs. However, there are large differences in how the designs are performed. The most important parameters are not the same. The reason for doing in a special way are not the same. Etc. Describe how the blades are designed and what the most important parameters are that must be fulfilled. What sort of blade profile do You expect that we will see in the fan of the destroyed engine.

6.

A radial compressor for air is needed. No diffusor can be installed so the fluid must be collected directly in a scroll. Because of this a limit is put on the fluid velocity out of the impeller to 170 m/s. The pressure ratio must be at least 1,8 and the flow 0.9 kg/s. The efficiency can be estimated to 85%. The impeller must be at least 1 cm wide all the way through.

Determine the main dimensions of the impeller and the speed.