Turbine engines

Weird Harold wrote:

Max wrote:While I am not a mechanical engineer, I can visualize a high volume turbine speed air compressor without fancy gearing. I have much more trouble getting the high speed of a steam turbine to run the low speed pumps of a hydraulic system without some pretty fancy gearing...

A high-RPM turbine driving a high-RPM pump can provide high pressure hydraulic fluid to a low-RPM motor -- or a very slow-moving actuator. The turbine + hydraulic pump is completely independent from the motors and actuators that use the pressure. In that respect, there is little difference between hydraulic and pneumatic systems. The main difference is in the compressibility of the working fluid.

IIRC the speeds for the various turbines and pumps is related to the densities of the media so a steam==>liquid connection would still require a heavy duty speed changing gear train where a steam==>air set would not. And the part about the actuators was the point I was making against pneumatic speeds being a problem. You are just reinforcing my point.

And the compressability point goes in favor of pneumatic reservoirs. A high pressure air reserve would probably be much more compact and easier to build than a similar capacity fluid accumulator. That would give a boat with such a reserve a sprint capability that could provide an (admittedly limited) tactical advantage.

USMA74 wrote:The Lexington and Saratoga were originally going to be built as battle cruisers but the Washington Naval Treaty resulted in their conversion to aircraft carriers. As battle cruisers they were to be armed with eight 16 inch guns, but originally retained eight 8 inch guns in four turrets (two forward and two aft of the island). In March 1942 the turrets were removed in favor of additional antiaircraft armament.

As were HMS Glorious, Furious & Courageous which actually saw service as battlecruisers during WW1 before being converted to reasonably successful Aircraft Carriers. One was "half converted" to Aircraft Carrier while still building, the forward 18" gun being removed and a "flying-off" deck added forward of the main superstructure.

Seawater should be a last resort as a working fluid in hydraulics. Common salt solutions encourage rapid corrosion of metals, and are particularly bad on many iron-based alloys. You can fight the corrosion on bulk metal (like a ship's hull), but I would expect severe problems with more delicate devices.
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Peter2 wrote:Seawater should be a last resort as a working fluid in hydraulics.

The seawater suggestion came from up-thread; I have my doubts about its suitability, but included it simply to cover the past discussions. It does have the advantage of availability for a ship's hydraulic drive. I'm sure the corrosion problem is solvable, since a ship's drive system is hardly "delicate."

Weird Harold wrote:

Peter2 wrote:Seawater should be a last resort as a working fluid in hydraulics.

The seawater suggestion came from up-thread; I have my doubts about its suitability, but included it simply to cover the past discussions. It does have the advantage of availability for a ship's hydraulic drive. I'm sure the corrosion problem is solvable, since a ship's drive system is hardly "delicate."

That set of a very loud alarm when I read it. HEAVY DUTY is not the same as "indelicate". Quite the opposite in fact. The effect of sand on gear trains is legendary...

Max

Max wrote:..snip..
And the compressibility point goes in favor of pneumatic reservoirs. A high pressure air reserve would probably be much more compact and easier to build than a similar capacity fluid accumulator. That would give a boat with such a reserve a sprint capability that could provide an (admittedly limited) tactical advantage.

High pressure systems comprising of a gas that has high compressibility is a sure recipe for disaster. A little battle damage and things tend to rupture in spectacular ways - often deadly.

During the 60's my father saw an accident where a mechanic was standing on a tractor tire while trying to inflate it. The tire ruptured. They had to scrape the guy off the ceiling. Not a pretty sight.

Joat42 wrote:High pressure systems comprising of a gas that has high compressibility is a sure recipe for disaster. A little battle damage and things tend to rupture in spectacular ways - often deadly.

Much like the magazine taking a hit... Still, they keep building warships with magazines...

Max

Max wrote:

Joat42 wrote:High pressure systems comprising of a gas that has high compressibility is a sure recipe for disaster. A little battle damage and things tend to rupture in spectacular ways - often deadly.

Much like the magazine taking a hit... Still, they keep building warships with magazines...

Max

You need to have magazines on a warship and they are usually located in the citadels which are heavily armored (at least if we talk about modern ships, don't know how the Haraldhs are setup).

Using compressed air/gas for propulsion is far more inefficient, expensive and dangerous than using hydrostatic propulsion, and Safeholds engineers has far more experience in hydraulics than pneumatics.

Even today its extremely difficult to built high pressure gas systems that isn't prone to a diverse range of problems where contamination is the top one. Also, finding leaks in pneumatic systems are a nightmare compared to a hydraulic system where you can see the hydraulic fluid leaking.

Another issue with pneumatic systems compared to hydraulics is that pneumatics require a lot of more energy because of the heat-loss during the compression cycle.

If you need a system that can handle high/heavy loads only hydraulics works in this context, since pneumatics require so much larger motors/cylinders to be able to handle same load.

Max wrote:

Weird Harold wrote:
The seawater suggestion came from up-thread; I have my doubts about its suitability, but included it simply to cover the past discussions. It does have the advantage of availability for a ship's hydraulic drive. I'm sure the corrosion problem is solvable, since a ship's drive system is hardly "delicate."

That set of a very loud alarm when I read it. HEAVY DUTY is not the same as "indelicate". Quite the opposite in fact. The effect of sand on gear trains is legendary...

Max

How right you are. I was actually thinking of valve seatings when I wrote of the corrosive effects of brine. Valves can be pretty massive structures, but the seatings are delicate because they have to fit real tight. If they don't, the valve doesn't close properly and that leads to all sorts of trouble. All it needs is a tiny speck of impurity in the wrong place.
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Peter2 wrote:Seawater should be a last resort as a working fluid in hydraulics. Common salt solutions encourage rapid corrosion of metals, and are particularly bad on many iron-based alloys. You can fight the corrosion on bulk metal (like a ship's hull), but I would expect severe problems with more delicate devices.
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IIRC, they use engineering quality ceramics and plastics. There is still the bio fouling problem.