Thermal Expansion - Measurement

[JourneymanEng]

Hello all,

I have an interesting problem with a micro GT and Recup combination.

Background:
Thermal expansion is wreaking havoc with bellows and pipework. I suspect a combination of unrelieved stresses in the fabricated pipes, and an incorrect config for the bellows.

Problem:
I would like to measure the thermal expansion of the entire system and need an idea of the correct apparatus & method for such an experiment.

I know i will need to start with a datum that is fairly even temperature (got it). Then need to measure specific points on the assembly during the course of combustion (know the points).

Specific problem: I will need to ensure all measurements are accurate but have a budget and limited time. In a past life i worked for the aircraft industry and made good use of theodolytes for measurement.

Is there a standard no-messing-about way to get an accurate idea of what a large assembly of metal is doing under thermal expansion?

 

[byrdj]

Before "Laser alignment" became the management desired way to go, I used a precision level. A simple straight edge with one end on the "high" datum point and shims added to make level will provide vertical growth. I've also used a shop made straight edge with a micrometer head attached to one end.

The companies that make and promote laser alignmet tools, also have tools that will measure growth during heatup. However, one straight edge and level with multiple documented datum points would be cheaper than multiple laser things.

You could also calculated expected growth by determine distances from "fixed", temperture change, and thermal coefficiant. for example a turbine bearing centerline supported 36" from "floor" that has a 250F rise would grow (36 X 250 X 0.007 = 0.063&quot anoter example would be a turbine sliding standard, with 100" between supports, with 900F change will grow (100 X 900 X 0.007 = 0.630&quot

The thermal expansion coefficient for different materials will vary greatly from the 0.007"/0.001" "average steam turbine metal" I use for quick calcs.