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YachtForums · 04-19-2006, 03:28 PM

I took a look at the patents issued for Intellijet. It was interesting to note they were issued to a Palm Bay, Florida location where some of my own development work eventually ended up.

I don’t have the software currently installed to display the TIFF images/drawings from the patent office, but in reading through their patents, it looks like they’re on the right track. However, I do have some reservations about what I’ve seen in the promotional video on their website…

A. Variable Intake Gullet; Sliding Plate

I like the idea of a sliding plate to reduce the intake gullet size, but there are two important caveats….

1. Sand intrusion with any type of moving mechanism on the bottom of a hull. We encountered this repeatedly with deployable pumps and foils on the vessels we designed. In all our testing, we could not be fully prepared for the “real world” punishment a craft could be subject to, i.e. high speed beaching, running aground or hitting a submerged/floating object.

2. Intellijet’s sliding plate is designed to increase vacuum at higher speeds by decreasing the size of the uptake entrance. Short of a better mechanical means, this will work, but it’s really not the ultimate answer. In order to effectively increase vacuum, you MUST decrease the volumetric area within the cavity, specifically where ventilation is induced, which is near the top of the intake gullet. Decreasing the size of the “opening” should also be done in conjunction with an overall reduction of the volumetric area of the intake gullet. Mechanically… this is very difficult to create!

3. Intellijet’s sliding plate moves forward to decrease the opening at high speed. Ultimately, moving the intake forward can have both good and bad effects.

The good… moving the lip of the intake plate forward CAN help optimize flow to the top of the impeller, as well as reducing the abrupt uptake of water at higher speeds, by creating a more direct path to the impeller.

The bad… the more forward the intake area is, the sooner ventilation will be incurred at higher speeds. For example, as speed increases, a hull develops more lift and the point of lift moves further aft. The higher the hull rides on the water; the sooner ventilation will be incurred by the jet pump intake. Moving the intake forward, where more air is present, can reduce uptake efficiency. Another caveat here... by moving the plate forward, you are diverting flow higher on the impeller, which may starve the lower portion of the impeller.

In a nutshell… the intake gullet should become smaller with increased speed, because this increases vacuum and decreases aeration. Ultimately, the opening should move further aft, away from potential interruptions in vacuum. The pump should move further aft and assume a surfacing position. The combination of both should also create a path of least resistance to the flow of water for greatest efficiency at higher speeds.

B. Variable Pitch Impeller Blades…

Variable pitch blades and the mechanism for controlling the same are nothing new, but this is the first time I’ve seen it in a jet pump! This is one of the Holy Grails to increasing efficiency, whether it’s for jet pumps or non-ducted props. BUT, it’s not without some drawbacks…

1. In order to accommodate the mechanism/gears/cams for controlling pitch, the size of the impellor hub must increase in size proportionately. The larger the hub, the greater the obstruction to flow. In an axial flow pump, this can be a problem. This is the main reason a rim-driven prop is a more effective design.

2. The benefit of variable pitch is obvious, but with a jet pump… it is even more important. Increasing pitch can increase vacuum… critical to high-speed pump performance, BUT… variable pitch blades DO NOT overlap each other. It would be physically impossible for the blades to go from forward, to neutral or reverse. Over-lapping blades are one of the most beneficial ingredients in pump efficiency, along with radial edge (swept) blade designs.

Intellijet’s variable pitch blades allow forward, neutral and reverse, without shifting gears, changing RPM or utilizing a reverse bucket. This is ALL good, but it’s not the Holy Grail of jet pump design.

In addition to NOT having over-lapping blades, the other problem I have with the entire variable pitch concept within a jet pump is how to control hydraulics between the trailing edge of the blades and the leading edge of the stators. When blades change pitch, the distance between these point’s changes dramatically… not to mention how important it is that the angle of stators match the pitch of the blades. That’s an entirely new subject that I won’t go into.

C. Variable Geometry Venturi…

I don’t have time to read the patent (in its entirety) on how Intellijet is accomplishing a variable geometry venturi, but I can tell you this is VERY difficult to do mechanically. Not only must the diameter of venturi’s exiting orifice change accordingly, the rate of compression inside the bowl must change as well. For acceleration, the exiting orifice should be larger and the rate of compression (acceleration!) should be more abrupt. As speed increases, the orifice should become smaller and the rate of compression (acceleration!) should be more relaxed. This entire sequence must work in conjunction with the level of aeration present in the bowl, which should also match the venturi’s tail cone. NOT easy to do!

And last… in reading Intellijet’s website, they speak of presenting this technology to the Naval Surface Warfare Center. I can tell you this much… The Department of the Navy has had an effective means and technology in this area for MANY years, but it’s not an area of critical need. If it was, I wouldn’t be the admin of YF... I’d still be standing in front of congressional committees presenting proposals for continued funding.

04-19-2006, 03:28 PM	#16
YachtForums Publisher/Administrator Join Date: Dec 2002 Location: South Florida Posts: 10,228	I took a look at the patents issued for Intellijet. It was interesting to note they were issued to a Palm Bay, Florida location where some of my own development work eventually ended up. I don’t have the software currently installed to display the TIFF images/drawings from the patent office, but in reading through their patents, it looks like they’re on the right track. However, I do have some reservations about what I’ve seen in the promotional video on their website… A. Variable Intake Gullet; Sliding Plate I like the idea of a sliding plate to reduce the intake gullet size, but there are two important caveats…. 1. Sand intrusion with any type of moving mechanism on the bottom of a hull. We encountered this repeatedly with deployable pumps and foils on the vessels we designed. In all our testing, we could not be fully prepared for the “real world” punishment a craft could be subject to, i.e. high speed beaching, running aground or hitting a submerged/floating object. 2. Intellijet’s sliding plate is designed to increase vacuum at higher speeds by decreasing the size of the uptake entrance. Short of a better mechanical means, this will work, but it’s really not the ultimate answer. In order to effectively increase vacuum, you MUST decrease the volumetric area within the cavity, specifically where ventilation is induced, which is near the top of the intake gullet. Decreasing the size of the “opening” should also be done in conjunction with an overall reduction of the volumetric area of the intake gullet. Mechanically… this is very difficult to create! 3. Intellijet’s sliding plate moves forward to decrease the opening at high speed. Ultimately, moving the intake forward can have both good and bad effects. The good… moving the lip of the intake plate forward CAN help optimize flow to the top of the impeller, as well as reducing the abrupt uptake of water at higher speeds, by creating a more direct path to the impeller. The bad… the more forward the intake area is, the sooner ventilation will be incurred at higher speeds. For example, as speed increases, a hull develops more lift and the point of lift moves further aft. The higher the hull rides on the water; the sooner ventilation will be incurred by the jet pump intake. Moving the intake forward, where more air is present, can reduce uptake efficiency. Another caveat here... by moving the plate forward, you are diverting flow higher on the impeller, which may starve the lower portion of the impeller. In a nutshell… the intake gullet should become smaller with increased speed, because this increases vacuum and decreases aeration. Ultimately, the opening should move further aft, away from potential interruptions in vacuum. The pump should move further aft and assume a surfacing position. The combination of both should also create a path of least resistance to the flow of water for greatest efficiency at higher speeds. B. Variable Pitch Impeller Blades… Variable pitch blades and the mechanism for controlling the same are nothing new, but this is the first time I’ve seen it in a jet pump! This is one of the Holy Grails to increasing efficiency, whether it’s for jet pumps or non-ducted props. BUT, it’s not without some drawbacks… 1. In order to accommodate the mechanism/gears/cams for controlling pitch, the size of the impellor hub must increase in size proportionately. The larger the hub, the greater the obstruction to flow. In an axial flow pump, this can be a problem. This is the main reason a rim-driven prop is a more effective design. 2. The benefit of variable pitch is obvious, but with a jet pump… it is even more important. Increasing pitch can increase vacuum… critical to high-speed pump performance, BUT… variable pitch blades DO NOT overlap each other. It would be physically impossible for the blades to go from forward, to neutral or reverse. Over-lapping blades are one of the most beneficial ingredients in pump efficiency, along with radial edge (swept) blade designs. Intellijet’s variable pitch blades allow forward, neutral and reverse, without shifting gears, changing RPM or utilizing a reverse bucket. This is ALL good, but it’s not the Holy Grail of jet pump design. In addition to NOT having over-lapping blades, the other problem I have with the entire variable pitch concept within a jet pump is how to control hydraulics between the trailing edge of the blades and the leading edge of the stators. When blades change pitch, the distance between these point’s changes dramatically… not to mention how important it is that the angle of stators match the pitch of the blades. That’s an entirely new subject that I won’t go into. C. Variable Geometry Venturi… I don’t have time to read the patent (in its entirety) on how Intellijet is accomplishing a variable geometry venturi, but I can tell you this is VERY difficult to do mechanically. Not only must the diameter of venturi’s exiting orifice change accordingly, the rate of compression inside the bowl must change as well. For acceleration, the exiting orifice should be larger and the rate of compression (acceleration!) should be more abrupt. As speed increases, the orifice should become smaller and the rate of compression (acceleration!) should be more relaxed. This entire sequence must work in conjunction with the level of aeration present in the bowl, which should also match the venturi’s tail cone. NOT easy to do! And last… in reading Intellijet’s website, they speak of presenting this technology to the Naval Surface Warfare Center. I can tell you this much… The Department of the Navy has had an effective means and technology in this area for MANY years, but it’s not an area of critical need. If it was, I wouldn’t be the admin of YF... I’d still be standing in front of congressional committees presenting proposals for continued funding.