Turbine

(design meeting notes)

First Stage

first nozzle stage: should be an impulse stage. flow goes to sonic velocity, choke flow regime, pressure drop is significant. The blades are impulse blades, and pressure drop will be very low. The air will cool, across the nozzle.

gives you a way to control mass flow

the air that strikes the blades will be much cooler because of expansion to high velocity (20% temp drop)

How many rows of blades do we need, to get expansion ratio of about 4?

Second Stage

may be difficult to also get it in choked flow. so we have to choose between first or second stage being in chocked flow.

inlet manifold and nozzle must have about double the flow area, compared to those of the first stage

challenge: peak temperature is on the second stage, rather than the first stage. does this mean that impulse blades should be used here, rather than reactive blades?

Constant air mass flow

power varies by varying turbine inlet temperature. so when running at part load, these types of turbines will be inefficient.

Turbine casing width must stay below 3.5 m, to remain rail-transportable, excluding the external combustor, which connects via a flange

Combutor cooling flow:

420+1300 -> 670

questions:

torrous: you want to keep the velocity constant, so that you don’t have to accelerate and decelerate, and you get constant pressure

applies to inlet plenum upstream of each of the two turbine nozzles. also applies to the outlet plenum on the reactor vessel.

Cold Air Line

what is the design assumption on the diameter of the cold air pipe? also, need to transition to higher diameter, because we shift to insulated piping

need to rotate around so it comes off the bottom

Hot Air Line

add the extension

to mention:

  1. adding notes in wordpress
  2. design of torrous
  3. posting edrawing of latest design
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2013-06-26 Meeting Notes

General SolidWorks updates

  • Air lines: change elbows to straight 90° angles and internal insulation (look at PBMR design).
  • Hot air by-pass line used to reduce load: direct line with valve between hot duct and vent stack. This way, the nuclear heat load won’t change. These lines can be elbows.
  • Need to fix turbomachinery design for internal combuster. Want to use same injector design as Alstom GT112n turbine. 2nd stage: hot gas coming through center, and gas injection lines will come radially instead of axially. Current design shows internal combustor which is not needed à remove. 1st and 2nd expansion stages will have 2 blades each (4 total instead of 3 currently).
  • Explosion hazard: need to work through it carefully. Natural gas explosions are going to be DBEs à need to update DBE list (Mike). Need to think about how to prevent backflow to the air lines in multiple ways. May use check valve in vertical section of the hot duct (2 half disks that will open in normal operation and close the duct from gravity to prevent backflow). Also need to think about blow-out pressure control à use rupture disks? Active air flow to flush the lines? For redundancy, use an air-activated gas injection valve (fail closed) so that gas cannot be injected when air is not running.
  • May also want to run longer salt lines (even have an intermediate loop) so that the air heaters are not in the nulcear island. Or put an explosion-proof wall between CTAHS and reactor vessel?
  • Need by-pass between cold and hot duct to allow for full intake to the turbine during startup.
  • Or replace gas with liquid fuel to avoid all the gas issues? Need to work through the economics.

(notes taken by Nicolas)

Managing Gas Explosion Risk

Design basis events – check with Mike

———————-

natural gas explosions
how do we prevent back-flow?
we don’t want gas to go up into the CTAH

New components:
————–
back-flow check valve on hot duct
safety-related valve that isolates CTAH on the air side
question: do the hot and cold air ducts run below grade?

can we have a system to keep gas from flowing if there is no air flowing?

spark, or continuously burning pilot light.

how do we do blow-out?
relief valve on hot and cold ducts

need to add by-pass line to connect hot and cold duct

we need multiple ways to prevent back-flow
do we need active air flow?

air-activated gas valves using air from the air cold leg
how do we route a nat gas leak to a vent stack?

natural gas accidents at combined cycle plants, with the steam generator exploding
explosion-proof wall in-between reactor vessel and CTAH
how about the pressure coming up the salt lines?

alternatives to fuel:
1. depressurize natural gas, then recompress it
2. liquid fuel
3. other?