VTOL Jet Engine Aircraft and VTOL Jet Engine

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Main Question or Discussion Point

I am thinking about VTOL jet engine aircrafts like the following example (an ambulance).

ambulance.jpg


To be able to buid that kind of aircraft VTOL jet engines are needed. At the moment there are no VTOL jet engines available, but I have my own proposal:

vtolengine2.jpg


I have questions to jet engine experts. Is my design viable? Could the thrust-to-weight be over 50? What about a jet engine with following specs:

- thrust 8000 N (1800 lbf)

- weight 16 kg (35 lb), the thrust-to-weight ratio is 50

- height 300 mm (12")

- diameter 400 mm (16")

More: << Link to personal website deleted by the Mentors >>
 
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Answers and Replies

Klystron
Gold Member
503
582
While not an expert on jet engines, I have gathered operational data on a variety of VTOL aircraft via radar and tracking video and on models in wind tunnels. From your size specifications are you designing jet propelled model aircraft or drone with VTOL capability?
 
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berkeman
Mentor
56,129
6,157
Welcome to the PF. :smile:
(an ambulance)
How does the air ambulance in your rendering take off vertically? With only one engine on the high wing, I'm not able to picture how it can smoothly and stably take off and land vertically...
 
etudiant
Gold Member
1,187
110
Afaik, the best lift engine ever produced was the RR RB162, with a listed 18.75 thrust to weight.
Getting to 50 would be a massive challenge, that is getting to rocket engine territory.
Note the RB162 had a dry weight of about 280 pounds, about 10x heavier than your notional item and delivered around 5500 pounds of thrust, with very low fuel efficiency.
 
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Can you all see the pictures?

If not here they are again:

http://www.cyanspace.com/images/ambulance.jpghttp://www.cyanspace.com/images/vtolengine2.jpg
Here's a previous thread on this topic.

https://www.physicsforums.com/threads/why-must-vtol-engines-be-larger-than-normal-engines.790352/
I am unclear how a VTOL engine differs from a regular jet engine.
VTOL jet engine is designed only for lift and land the aircraft. Ordinary jet engine could do that but they way too heavy for that at least without special/expensive materials.

From your size specifications are you designing jet propelled model aircraft or drone with VTOL capability?
How does the air ambulance in your rendering take off vertically? With only one engine on the high wing, I'm not able to picture how it can smoothly and stably take off and land vertically...

There are eight VTOL jet engines in the air craft. The engines are for full size aircraft.

Throttle and possible pressurized air are used for take off and landing.

Afaik, the best lift engine ever produced was the RR RB162, with a listed 18.75 thrust to weight.
Getting to 50 would be a massive challenge, that is getting to rocket engine territory.
Note the RB162 had a dry weight of about 280 pounds, about 10x heavier than your notional item and delivered around 5500 pounds of thrust, with very low fuel efficiency.
Afaik, RB162 was the only VTOL jet engine ever build but really newer used. It was tested with Dornier Do 31, but they didn't get it working.

RN162 was build at the beginning of 1060s. After that jet engines evolved a lot. Also materials have evolved.

I tested NASAs jet engine simulator EngineSim and I got T/W 75 with carbon fiber and ceramic option. Of cource this was without my design. I hope that my design would do more.
 
etudiant
Gold Member
1,187
110
I honestly believe that the EngineSim is misleading you, as I do not think there is any experimental verification for the results. The numbers are probably right, but I suspect they reference unobtainium materials.

The RB 162 was indeed never put into service, but it was a state of the art design and metal technology has not advanced all that much since, the main temperature improvements have come with better turbine cooling and coatings. The limitation is still the compressor exit temperature, as components in that area are not easily cooled. Ceramics, which have been the hoped for solution, have not yet reached sufficient maturity to serve reliably.

Separately, the design you outline appears to have an annular intake, with the flow making 3 right angle turns to enter the combustor. There will be efficiency losses and it is a heavier structure than a straight through flow, so you must anticipate some big benefit from it that I do not see.

More broadly, a pure jet lift engine would be very hard to live with, the exhaust is more like a plasma torch than a hot wind, it melts the pavement. The Navy even had a hard time with the F35, even though the bulk of the lift is from a geared fan rather than the direct exhaust. A fan lift engine provides cooler exhaust and better mass flow, for very little extra weight.

Good luck in your efforts!
 
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797
173
If your aircraft doesn't have to fly long distances, it is more economical and fuel efficient to use a conventional rotor (powered by turboshaft or piston engine) to provide the vertical lift. A turbojet or turbofan engine gives you a speed advantage that may not be big enough for short or medium distance trips to be worth the drawbacks.
 

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