Thanks for answering, anyway -- and I for one am interested in the larger turbine (and combined-cycle) applications too.
Overmod Erik_Mag Steam injection acts similarly to EGR - i.e. diluting the oxygen reduces flame temperature. IIRC, 2700F is the magic temperature where NOx production really takes off. Read the papers I referenced -- the steam injection there is true bottoming, at pressure matched to combustor outlet, and providing increased mass flow through the power turbine(s). Interestingly it seems the water-cooled-stator approach to isothermal compression on the 501-K or 570-K appears to be working in lieu of formal water injection in keeping compression stages 'intercooled'... Where is our MG-loving millwright when we need him? ...
Erik_Mag Steam injection acts similarly to EGR - i.e. diluting the oxygen reduces flame temperature. IIRC, 2700F is the magic temperature where NOx production really takes off.
Read the papers I referenced -- the steam injection there is true bottoming, at pressure matched to combustor outlet, and providing increased mass flow through the power turbine(s).
Interestingly it seems the water-cooled-stator approach to isothermal compression on the 501-K or 570-K appears to be working in lieu of formal water injection in keeping compression stages 'intercooled'...
Where is our MG-loving millwright when we need him? ...
He's been working on a generator stator rewind for a 14oo MW machine. But I can't be of help on an Alison 501 engine I have worked on 501s but they were Westinghouse 501 series engines. The rotor for a Westinghouse 501F weighs right at 60 tons so there is no aircraft application. Early 501Bs , quite primitive by todays standards, produced over 53,000 HP. The latest versions, 501J I believe are around 225 MW or 301,608 HP. I hear that they have been breathed upon to produce substantially more. The later ones do have both air and water cooled blades. The water cools the blade and ,becoming steam, increases the volume of gas through the turbine end. The Westinghouse design is produced by Siemens and Mitsubishi. Siemens aquired the westinghouse intellectual properties but Mitsubishi had a license with no expiration or termination provision so they continue to produce and develop the engine as does Siemens.
Overmod Erik_Mag Read the papers I referenced -- the steam injection there is true bottoming, at pressure matched to combustor outlet, and providing increased mass flow through the power turbine(s).
Erik_Mag
Steam injection provides two advantages, one is the improvement in efficiency with the bottoming cycle and the other is reduction in NOx presumably from reduction in flame temperature. Freeman Dyson was championing steam injected gas turbines for electric power generation specifically on low harmful emssions.
Speaking of bottoming cycles - seem to remember Paul M. discussing a supercritical CO2 turbine - another is work being done on higher efficiency thermoelectric conversion optimized for exhaust heat.
timz Erik_Mag at 100F the SFC with steam injection was 0.35lb/hp-hr and 0.53lb/hp-hr without steam injection. Including the fuel needed to produce the steam? How much steam injected per pound of fuel into the turbine?
Erik_Mag at 100F the SFC with steam injection was 0.35lb/hp-hr and 0.53lb/hp-hr without steam injection.
Including the fuel needed to produce the steam? How much steam injected per pound of fuel into the turbine?
There is enough heat in the exhaust to generate the required amount of steam - assuming a very effective heat transfer. As OM said, the steam injection acts in part as a bottoming cycle. One benefit of using exhaust heat is that the ultimate exhaust temperature is greatly reduced.
For 7,000 HP output, the fuel flow is 2,000 lb/hr and the steam flow is 7,200 lb/hr.
Worthless Kalmbach IT makes it impossible to edit my own link on a phone. The permanent link to Porter's ASME paper on the 6400kW version of the 501-K industrial engine with process-steam bottoming is:
https://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1997/78699/V002T07A004/2409044/v002t07a004-97-gt-511.pdf
There is discussion in the 'Chung cycle' paper about the sources of the bottoming steam used to enhance output torque (vs. injection to limit peak combustor temperature or TIT).
Erik_Magat 100F the SFC with steam injection was 0.35lb/hp-hr and 0.53lb/hp-hr without steam injection.
Erik_MagSteam injection acts similarly to EGR - i.e. diluting the oxygen reduces flame temperature. IIRC, 2700F is the magic temperature where NOx production really takes off.
Timz:
The 501-K series is derived from the Allison aircraft turbine for stationary use. With steam injection, the turbine produces more power for a given amount of fuel - at 100F the SFC with steam injection was 0.35lb/hp-hr and 0.53lb/hp-hr without steam injection.
Bear in mind that the data is at least 32 years old, and there has been considerable progress in improving turbine efficiency.
Paul M.
The theoretical limit for desalinization of sea water with reverse omosis is around 0.9kwhr per cubic meter of fresh water. Some membranes have shown ~2kwhr per cubic meter. For de-ionizing "city water", I suspect energy requirements will be even less.
Giving the water vs steam injection a bit more thought, it seems to me that water injection would work better if the output of the compressor was reduced thus reducing the excess air, which then increases combustion temperature and the water wuld be used to keep the turbine inlet temperature within limits. That is less compressor power would be needed to keep the same mass flow through the turbine.
Steam injection acts similarly to EGR - i.e. diluting the oxygen reduces flame temperature. IIRC, 2700F is the magic temperature where NOx production really takes off.
timz Erik_Mag A 1989 vintage brochure for the Allison 501-K turbine states that the fuel consumption with steam injection is substantially less than without steam injection.
Erik_Mag A 1989 vintage brochure for the Allison 501-K turbine states that the fuel consumption with steam injection is substantially less than without steam injection.
Erik_MagA 1989 vintage brochure for the Allison 501-K turbine states that the fuel consumption with steam injection is substantially less than without steam injection.
By way of analogy, one could think of water injection as feeding a steam locomotive boiler with an injector, combined cycle as using a feedwater heater and steam injection as using an exhaust steam injector, which is a middle ground in efficiency.
As to reverse osmosis, there is a process called mechanical vapor recompression that conducts distillation with much greater energy efficiency. By adding mechanical work through a vapor compressor, it reclaim much of the latent heat of vaporization in the distillation from condensing the vapor at a higher pressure and hence temperature. Think of that as a kind of heat pump, where mechanical work causes heat to flow from warm to cold, heating up a cold space.
Another way to reduce the penalty of the latent heat of vaporization is the multi-effect still. With a suitable scavenging pump against air leaks, condensing can take place at a lower temperature and pressure than the evaporation. The condenser in turn can evaporate fluid at a lower pressure, where its vapor can in turn condense at a yet lower pressure. Each such stage is called an "effect."
The multi-effect still was invented by Norbert Rillieux for extracting sugar from the pressed pulp of sugar cane. I read that a 3-effect still is used in commercial processing of orange juice concentrate, but larger number of effects could boost energy efficiency in trade for more costly apparatus. Mechanical vapor recompression is used on Navy vessels to produce fresh water. Reverse osmosis may be better for smaller scale use -- the Northern Michigan maple syrup producers bought reverse osmosis machines during the last runup in oil prices.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
I suspect the loss in effiency with water versus steam is the heat of evaporation robbing enthalpy from the combustion products, whereas steam injection provides more high pressure gas (steam) to the gas flow through the power turbine without absorbing a lot of heat in evaporating water. One advantage of steam generation is that the final exhaust temperature is much cooler than straight out of the turbine. Both techniques will increase the mass flow through the turbine.
Reverse osmosis works almost as well as distallation for removing dissolved solids, which would make logistics easier.
Water injection (into the gas turbine combustion chamber) boosts power at the expense of fuel consumption. Water injection was used on jet airliners prior to the use of turbofans to get more thrust for takeoff and climb.
Steam injection is a whole other proposition. It boosts power, yes, but the considerable heat to turn water into steam is taken from the otherwise wasted exhaust heat instead of from the fuel burning in the combustion chamber.
Steam injection is a kind of non-condensing "bottoming cycle." A condensing bottoming cycle, which is more efficient converting the waste, exhaust heat from the gas turbine into power requires a more complicated combined gas-turbine steam-turbine power plant than the simpler measure of using exhaust heat to boil water and then extract work from that steam by feeding through the gas turbine.
One drawback of steam injection is that it requires distilled water. Imagine if you had to supply a steam locomotive tender with distilled water.
Since Kalmbach was offering me a $5 off for my birthday, I figured buying this book would be a good use of it. One amusing part of the ordering experience was getting warning about USPS induced delays - the book arrived only 5 days after the order was placed...
General impression is the book is an interesting read with a broader coverage than Thos Lee's Turbines Westward, particularly with developments after 1970. Walter Simpson went into a fair amount of detail on the fuel efficiency of several of the steam and gas turbine locomotives.
A few comments:
The was no mention of the TGOJ steam turbine locomotives that were in service for a couple of decades hauling iron ore to Oxelosund in Sweden.
Both Lee and Simpson missed one detail about the 1939 GE steam turbine electric locomotive, in that GE was involved with steam turbine electric drives for ships. Naval turbines are intended to have a reasonably good efficiency over a wide power range and the USN used Bunker C as boiler fuel. Power to weight ration is fairly good, Fletcher class destroyers had 60,000hp available for a ship that weighed 2,500 tons.
I have a quibble with Simpson's comment on water injection for gas turbines increasing specific fuel consumption. A 1989 vintage brochure for the Allison 501-K turbine states that the fuel consumption with steam injection is substantially less than without steam injection.
Simpson is correct in stating that the UP GTEL's were fuel hogs, the 4,500 HP locomotives used almost as much fuel idling as a modern 4,400 HP diesel uses in run 8. OTOH, GE's large frame gas turbine can reach 46% thermal efficiency, compared to maybe 50% for a Tier III locomotive diesel engine.
Nitpick, the M-497 wind tunnel testing was done at Case Institute of Technology before the merger with Western Reserve.
I was intrigued by his coverage of the X-12 "Atomic Locomotive", though such a beast would more likely have used a molten salt reactor derived from the Aircraft Nuclear Propulsion program than the acqueous solution reacotor in the Borst design. Best way to do nuclear powered trains is using a stationary nuclear generating station and electrification.
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