Click for McConaghy
Click for McConaghy
Click for Nordlund
Click for Moonen
Click for Oceanco
Click for JetForums
Go Back   YachtForums.Com > GENERAL YACHTING DISCUSSION > Technical Discussion > Jet Drive vs. Prop

Login to YachtForums
Username
Password

Reply

Jet Drive vs. Prop

 
 
LinkBack Thread Tools Rating: Thread Rating: 10 votes, 4.70 average. Display Modes
Old 02-21-2008, 04:47 PM   #46 (permalink)
Senior Member
 
Marmot's Avatar
 
Join Date: May 2007
Location: 9114 S. Central Ave
Posts: 2,960
Yeah, we use flash evaps running at around 162 - 170 F, just high enough to kill bacteria but minimize scaling. The only treatment involved at that point is an anti-foaming compound that also helps keep the scale soft enough to be chemically cleaned when it gets too thick. Virtually none of that makes it through to the distillate though.

The distillate is not treated, there is a valve that sends it to the distilled water tanks, the potable tanks, or the bilge. When it's good enough to save, it's all the same water.

When distilled water becomes feed water there are so many chemicals added that it is technically contaminated water with potassium hydroxide added to obtain a pH of around 11 and until recently laden with hydrazine to scavenge oxygen, and more phospates than the runoff from a third world laundromat. Pretty nasty stuff and makes terrible tea that really would give you the runs.
Marmot is offline   Reply With Quote
Old 04-10-2008, 06:13 PM   #47 (permalink)
Senior Member
 
brian eiland's Avatar
 
Join Date: Jul 2004
Location: Washington DC, Annapolis MD, Thailand
Posts: 2,433
electro-magnetic propulsor as part of a waterjet propulsion unit

Quote:
Originally Posted by brian eiland
It certainly appears as though the rim-driven propulsor concept has a lot of potential as a component in a jet pump drive system……ie, a rim driven impeller (“a new era of impeller design” as noted by YachtForums). Now we know there is considerable work being done on rim-drive technology, particularly those incorporating permanent-magnet electric motor components to power-up the rim. These electrical driven rim-drives may prove too advanced, overly complicated, and/or too expensive for small PWC or RIB jet applications.
Abstract

A concept investigation has been carried out into the possibility of using a tip driven electro-magnetic propulsor as part of a waterjet propulsion unit. The primary advantage is that there is no need to insert a drive shaft within the waterjet inflow. This significantly reduces cyclic variations in the propulsor inflow and removes an area of flow separation around the shaft. It also provides the designer with greater freedom as to the types of propulsion systems available and where they can be placed within the ship.

The viability of the concept has been examined by considering the performance of an axial flow electromagnetic thruster developed for the ROV market and numerically studying its performance within a typical waterjet inflow. A study was also conducted to examine the scalability of such propulsion units. It is concluded that for a typical size of waterjet with an input power requirement of 110 kW and diameter of 0.25m the maximum delivered power at 2,200 rpm would be 90 kW. This design would have the benefits of no shaft induced losses and reduced cyclic blade loadings and should deliver a higher thrust than comparable conventional waterjet units using geared electric motor drives
http://eprints.soton.ac.uk/22746/
brian eiland is offline   Reply With Quote
Old 08-23-2010, 05:20 PM   #48 (permalink)
Senior Member
 
brian eiland's Avatar
 
Join Date: Jul 2004
Location: Washington DC, Annapolis MD, Thailand
Posts: 2,433
Electric PWC, the Green Samba

Got a note from a fellow just today asking if I had seen this... I had not.

It's not the first to try its hand at an all-electric personal watercraft, but the Ohio-based Silveira Group is claiming that its new so-called Green Samba will be the first "viable" vehicle of its kind. To that end, the company says that the Green Samba will deliver the same 65 mph performance of the fastest 260 bhp sit-down PWCs, and do so while remaining completely silent thanks to a pair of twin direct drive electric propulsion pods. As the company is quick to point out, that also has the added benefit of eliminating one of the biggest complaints about PWCs from the public: their noise. Of course, the other key to viability is the price, and Silveira is unfortunately doing decidedly less talking about that right now, saying only that it will be able to "ballpark a retail price" when it finishes work on the latest prototype in August.......Gizmag

Wonder what the details are on the propulsion unit(s) ??
brian eiland is offline   Reply With Quote
Old 08-23-2010, 05:37 PM   #49 (permalink)
Senior Member
 
K1W1's Avatar
 
Join Date: Sep 2005
Location: My Office
Posts: 6,374
Quote:
Originally Posted by brian eiland
Wonder what the details are on the propulsion unit(s) ??
Hi,

I also wonder how the propulsion V longevity ratio compares to 30 lt of gas v the unmentioned recharge requirement, 5 mins for Gas how long for electric?
K1W1 is offline   Reply With Quote
Old 08-23-2010, 05:40 PM   #50 (permalink)
Senior Member
 
brian eiland's Avatar
 
Join Date: Jul 2004
Location: Washington DC, Annapolis MD, Thailand
Posts: 2,433
Unique Propulsion Unit(s)

...just found this:

When we wrote up the Samba in April 2009, it had already been through four prototypes, and several more have seen the water since then. The latest iteration has seen the shape and construction refined to such an extent that according to Rodrigo Silveira, just 65 bhp is now required to match the performance of the biggest 240-260 bhp Sea-Doo, Kawasaki and Yamaha designs. But the aim had also been to eventually replace the 800cc twin-cylinder internal combustion engines the company was using in the development process with electric propulsion.

In the last twelve months, the company almost gave up on that process. "I can tell you that making a green watercraft is not easy," Silveira told Gizmag.

"Our experiments were becoming more discouraging. We knew that the public would not accept lesser performance to go green – being a good citizen does not compensate for being ten mph slower than your friends on their internal combustion skis."

"We wanted to use an electric motor but the amount of energy required to get a jet ski on the plane was so large that it was using too much of the battery capacity. Combustion engines give you the torque you need to get to planing very quickly, without using too much of the available stored energy. We refined everything we could but to get the engine performance we wanted, and sufficient range, we would have needed 150 pounds of batteries which would have impinged on the weight and hence maneuverability too much. We had some sleepless nights wondering if our objectives were achievable with the current state of battery technology."

As the man who split the atom is oft quoted, "we didn't have any money, so we had to think" and it was in going back to the objective and rethinking it that the breakthrough came for Rodrigo. With limited resources and the high burn-rate of funds associated with intensive R&D, Silveira acknowledges that he was on the verge of giving up when the breakthrough came.

"We realized that we had been focusing on the motor, not the pump. In the same way that automotive electric propulsion is just about to go through a revolution of design because it doesn't require the same centrally located ICE we have had for the last 100 years, we began exploring what could be achieved with different propulsion methods."

"Once we began looking, we came across a propulsion technology originally developed for military applications that had not been previously used in watercraft and we have now acquired an exclusive license for using the technology on watercraft. After testing, we are now confident it makes our objectives possible both weight and price wise."

"With twin electric shaft-less drives of far less modest horsepower output, we are expecting about the same top speed as with the 65 bhp gas engine, which will give us 65 mph. In some ways the US Coast Guard's limit of 65 mph for watercraft has worked to our advantage as otherwise we'd probably be seeing 80 mph watercraft by now. Aiming at a non-moving target of 65 mph has been a huge advantage."

"The PWC is a huge water pump and the existing manufacturers have ignored the inefficiencies of the jet drive system currently in use by pouring horsepower and fuel on it. The inefficiencies in the horsepower-thrust conversion are quite obscene and that's were we've been focusing our energy."

"The propulsion pods we're using have an electric motor self contained within them. Each one has one moving part on the internal wall of the thrust pod, so it's a direct drive and it has eliminated many of the losses and made the system extremely efficient. What started out as a 6 horsepower motor became two 12 horsepower pods that are far more efficient."

"Our tank tests have proven to us that we can achieve between 34.9 and 36.5 pounds of thrust per horsepower compared to 28 pounds of thrust from a gasoline engine. By going electric and having a self contained pod that isn't connected to anything else other than a power source and a controller, we have achieved a similar freedom of design as automotive designers are now experiencing with electric motors. It means we don't need a big fat motor and a drive train in line with the motor."

"We started out with a single, centrally-located propulsion unit, but along the way, we realized if we made it into a dual pod system we would gain maneuverability by being able to get far more angle on the thrust pods than by using the traditional centrally-located nozzle steering. Then to take full advantage of turning the propulsion units, we had to completely different hull configuration."

"The redesign allowed us to put the pods below the planing line, which allows a more efficient intake and even better performance. With traditional design you can overload the pump, so you have a limitation on the amount of water going into the intake tunnel, but with these pumps we realized that the more we feed the pump, the better the performance.”

One of the benefits from using a lightweight, low-powered craft with such efficient drives is that the range of the unit has now skyrocketed and Rodrigo expects to get more than three hours usage from a full charge – well in excess of the 250 horsepower sit-down PWCs.

"Our testing so far shows that by getting the two pods on either side of the center line, you can get amazing turning ability. The first tests showed it was a bit too sensitive – it'd tip you off too easily because you just couldn't hold on. The prototype we have planned for August brings all the strengths into focus and… we're confident now we have a viable next generation PWC in every respect.."

http://www.gizmag.com/green-samba-fi...ric-pwc/15141/

...and some more pics
http://www.gizmag.com/green-samba-fi...icture/114776/
brian eiland is offline   Reply With Quote
Old 08-23-2010, 05:48 PM   #51 (permalink)
Senior Member
 
K1W1's Avatar
 
Join Date: Sep 2005
Location: My Office
Posts: 6,374
Hi,

I see two two closely related things here, the first being the checkbook journalism phenomenon and closely following is Smoke and Mirrors.
K1W1 is offline   Reply With Quote
Old 08-23-2010, 05:52 PM   #52 (permalink)
Senior Member
 
brian eiland's Avatar
 
Join Date: Jul 2004
Location: Washington DC, Annapolis MD, Thailand
Posts: 2,433
ahh, such an optimist you are
brian eiland is offline   Reply With Quote
Old 08-23-2010, 05:57 PM   #53 (permalink)
Senior Member
 
brian eiland's Avatar
 
Join Date: Jul 2004
Location: Washington DC, Annapolis MD, Thailand
Posts: 2,433
I was thinking it sounded more like these two subjects I brought up before:

Posting #31, Rim-Driven Impeller

Posting #47, Electro-Magnetic Propulsor as Part of a Waterjet Propulsion Unit
brian eiland is offline   Reply With Quote
Old 08-24-2010, 04:27 PM   #54 (permalink)
Senior Member
 
brian eiland's Avatar
 
Join Date: Jul 2004
Location: Washington DC, Annapolis MD, Thailand
Posts: 2,433
Links to Rim-Drive Propulsion Thread

Over in this subject thread on rim-drive propellers, have a look at postings #12 and #13

http://www.yachtforums.com/forums/te...ropellers.html
brian eiland is offline   Reply With Quote
Old 08-24-2010, 04:47 PM   #55 (permalink)
Senior Member
 
brian eiland's Avatar
 
Join Date: Jul 2004
Location: Washington DC, Annapolis MD, Thailand
Posts: 2,433
Rim Drive Impeller OR Intregal Canned Electric Motor ??

Opps, I might have been too quick to suggest this new jet unit was making use of a rim drive impeller.

What if it is of a form of an 'intregal canned electric motor'?
http://v3.espacenet.com/publicationD...37607&KC=&FT=E
brian eiland is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are EST. The time now is 11:11 PM.

Click for Pacific Mariner
Click for Nordhavn
Click for Ferretti
Click for Cheoy Lee
Click for McKinna
Click for MotorCheck


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Content Relevant URLs by vBSEO 3.3.2