Interesting project, but it seems that it had some technical issues.

"Air-Steam Hybrid Engine:
An Alternative to Internal Combustion..."

[www.transit.dot.gov]

"...The sum of the process is as follows:
Key start begins a modest fuel burn that immediately provides initial hot air fm ow through the engine.
• Depressing the accelerator increases the water fraction and fuel fm ow (in direct proportion).
• The vehicle moves forward under (air/steam/fuel) power in direct
proportion to wheel turn.
• The hot mix expands, and the expanded mix condenses the water fraction.
• A small parasitic load recompresses the small air fraction to reinjection pressures.
• Removing the foot from the accelerator returns the fm ow to hot air only, sweeping residual moisture from the cylinders and preventing hydraulic lock (during next cold start).
The engine can operate on any fuel whose fm ow can be regulated (semi-solid, liquid, gas). Combustion occurs at high temperature at one atmosphere, so much cleaner burning than internal combustion...."

The folks behind this came to Berrien Springs in order to give a presentation at the SACA meet. It is fair to say that that people were not impressed.

Hi Novice,

Here is a fairly late development with MTU Turbine Engines in Germany. They call this the WET engine. To me it is a combined steam - gas turbine system. Officially I would consider it a combined Brayton and Rankine Cycle.

I plan to talk about this WET engine in a presentation at the SACA meet. It has some key concepts that I will be leveraging. My intent is to have an interesting presentation for everyone...

MTU Wet Turbofan Engine

Hope to see you all there at the SACA Meet,

Rick

The only problems I’ve found with wet turbines is water or wet steam cutting grooves in the low pressure turbine blades. Off course this was found on the twenty-year shutdown of a power plant. 24-7 for twenty years. You could put your hand in some of the cuts.

On small sixteen inch turbines driving boiler feed pumps I found no problems. I don’t remember if the steam came from the super heated source.

Rolly

Rolly,
Their are some exotic turbine blade coatings out there. To give you an idea, take a grown crystal blade and plate a special base coat onto the blade. This coating creates a strong ionic bond to the next coating. Then use Electron Beam Vapor Deposition (EBVD) to coat the blade with something like titanium. Then finish it with a plasma spray coating even a ceramic. I performed a short gig at Chromoly NY where my customer was Textron. Other customers were Prat and GE.

I'm pretty confident that MTU would use the same technology on the WET engine. They would be able to achieve a decent MTBR.

Kind regards,
Rick

Rick
I have read about some of these new materials used on high temperature gas turbine blades even three D printing hollow turbine blades. It’s unenviable where the technology has goon. My experience is old school nowadays.
Jay Leno can spend six grand on high Tec coating his SS combustion chamber but most of us can’t, but we should be aware of the trouble we can get into doing some of the things we try building.

Rolly

BTW Rolly,
You know I think of you as a mentor. Attached is a concept, feedwater heater - condenser for a non-condensing Stanley. The MTU example influenced me to think of this. I would suspect you already had this concept in mind at some point in time.

Also, Pat,
If you're listening...I would like you to weigh in? Also mentor and suspect you thought of this for a Stanley.

Note that I plan to use this as a slide in a technical presentation at the SACA meet.

Kind regards,
Rick

Rick I have used exhaust feed water heaters on both my steamboats along with boiler exhaust economizers.
Lots of Stanley’s have used exhaust feed waters heater. I did not build one for my EX through.
Some where I have some photos of Stanley exhaust feed heaters, I will look.

I have built economizers for Stanley boilers see attached.
This is 100 feet of ½ OD type K tubing wound from the outside in and back out.

Rolly

Rick H, Your engine exhaust feedwater heater is a standard item for the non-condensing Stanley. With it's hot feed water, it adds about 15% performance to the boilers evaporation rate. The collection pit for condensed water in your feed water heater is a novel idea. In a Stanley, the engine's exhaust pulses would most likely blast your water collection pit empty of water in short order. It is worth experimenting with.

"Evaluation of the Climate Impact Reduction Potential of the Water-Enhanced Turbofan (WET) Concept":

[www.mdpi.com]

It is quite interesting aircraft engine with combined gas steam cycle.
There is no boiler- water is directly injected into combustion chamber of the turbofan engine.
The key component of the system is a special membrane system that sepates condensed steam turbine exhaust from non-condensing exhaust gases CO2 and N2.
This is exhaust gas water recuperation and it can also can be applied to IC automobile engines:

[digitalcommons.mtu.edu]

"Analysis of a novel waste heat recovery mechanism for an I.C. engine

Abstract
Typical internal combustion engines lose about 75% of the fuel energy through the engine coolant, exhaust and surface radiation. Most of the heat generated comes from converting the chemical energy in the fuel to mechanical energy and in turn thermal energy is produced. In general, the thermal energy is unutilized and thus wasted. This report describes the analysis of a novel waste heat recovery (WHR) system that operates on a Rankine cycle. This novel WHR system consists of a second piston within the existing piston to reduce losses associated with compression and exhaust strokes in a four-cycle engine. The wasted thermal energy recovered from the coolant and exhaust systems generate a high temperature and high pressure working fluid which is used to power the modified piston assembly. Cycle simulation shows that a large, stationary natural gas spark ignition engine produces enough waste heat to operate the novel WHR system. With the use of this system, the stationary gas compression ignition engine running at 900 RPM and full load had a net increase of 177.03 kW (240.7 HP). This increase in power improved the brake fuel conversion efficiency by 4.53%."



Edited 1 time(s). Last edit at 09/04/2021 12:30AM by novice.

MTU Aeroengines' patent describing semi-closed system for the water injection into aircraft turbofan engine and water recovery ducted air fan cooled wing condenser with the flue gas separation. Patent is in German language, but drawings are quite detailed and show basic operation principle of this engine.


[patentimages.storage.googleapis.com]

I'm wondering if this intellectual property (IP) is purposely misleading. There are several versions of wire diagram configurations that are significantly different in operation. I would chose page 27 and 28 as the best versions. However, in every case I would not put the feed water pump after the feed water heater...terms that I would use to describe the functions of the components. Perhaps this is another way to spoil would be IP pilfer(s).

The reason for the pump in front of the heat exchanger would be to pressurize the water and let it instantly go to vapor at the injection point at the combustor.

I think this concept has great potential and just needs to be experimented with, developed. My opinion, that the steam would allow a larger fan blade and greater efficiency in moving air. The gas turbine engine is depicted too big and could be drawn 3/4 the size and better represent the actual needed gas generator. MTU is noted for gear reduction to the Fan. This is another feature that I would incorporate into this concept.

Turbofan, turbojet and turboshaft engines are using large amounts of compressed air to cool the engine rotors to avoid their meltdown. Water compression requires much less power than compression of the air to the same pressure. Water injection will decrease excess air and net engine power will increase. In turbojet compressor power equals gas turbine power, in turbofan compressor consumes 2/3 of turbine power.

Most interesting in MTU's concept are ducted fan air cooled steam condenser and closed cycle water recovery from the engine's exhaust. Both of them have to be highly efficient, compact and lightweight. Water recovery has to be better than 90% for the duration of aircraft's flight.

Novice,
Good points about cooling air...

Correcting my earlier comments: after some German conversion to English that the diagram was misunderstood. Turns out that the pumps are before the feedwater heater.

Some definitions I propose to be used here:

Feedwater Heater - is a water to steam heat exchanger using the heat from the exhaust of the engine (provided steam in the exhaust). This is applied before an economizer and boiler(steam generator).
Feedwater Pump - pumps the water from a hot tank or storage tank through the feedwater heater and to the economizer/boiler
Economizer - is a water to burner gas heat exchanger after the hot gas has been through the boiler or steam generator.
Steam Turbine - steam applied/impinging to a rotating bucket if I may say it this way.

Where I thought there was a pump, this was actually a steam turbine. The heated water from the feedwater heater is questionable to be run direct to a steam turbine. There just isn't enough heat to get anything out of the engine/steam exhaust after several stages of gas turbines. Perhaps add a generating loop just behind the combustor to generate effective steam to run the steam turbine. This would reduce NOx also...just some thoughts.

All files from this thread

File Name	File Size		Posted by	Date
65-Feedwater Heater Concept.png	140.3 KB	open | download	Rick.H	09/01/2021	Read message
Stanley economizer.jpg	113.5 KB	open | download	Rolly	09/01/2021	Read message