sorry this is completely wrong Ive built the turbines for some of them. Most have them have pretty old tech as far as matl. goes the focus is on low cost not highest performance. Most of your assumptions are being based off of 40s tech GT comparing them to ICE engines that don't exist.WhiteBlue wrote:I'm surprised that all the UAVs the military and civil operators use are fitted with piston engines and wankels then. Normally you would expect them to use turbines as in manned vehicles, but turbines don't seem to be able to reach the efficiency requirements for that application. So one wonders why such a strong commercial demand with a turbine friendly customer has not led to a viable solution?
75 kg/h at 440 kW means 170 g/kWh which is a long way away from current MGT territory.
Whiteblue wrote:I'm surprised that all the UAVs the military and civil operators use are fitted with piston engines and wankels then
Re. Target drones Ringo you're spot on; When I was at Uni I worked with Ilmor on the Voodoo target drone... it uses a tuned Triumph motorcycle engine... solely on cost grounds....ringo wrote:Piston engines are cheap, very cheap. A UAV is a waste of a gas turbine.
So I dreamt my final year at Uni then?!flyfrog wrote:that is also incorrect most of the drones are turbine or rocket powered pistons and wankels are not fast enough.
machin wrote:So I dreamt my final year at Uni then?!flyfrog wrote:that is also incorrect most of the drones are turbine or rocket powered pistons and wankels are not fast enough.
And I made up this web page? http://www.aviationweek.com/shownews/02 ... rfrm23.htm
Don't get me wrong...I'm on your side; I'm all for GT's.. my point was that the reason that some drones and UAV's use piston engines is on cost grounds, not because GT's aren't good enough as Whiteblue was inferring. I sat down with the guys from Ilmor and that is exactly the reason that they gave for using the Triumph motorbike engine. They also confirmed that it would be slower than a GT-engined one, but much more cost effective -hence the market opportunity for them to get involved in the project.
If GT's were allowed by the rules I'm sure that many of the costs and shortcomings would be overcome... For example I like 747h's idea to combine it with a KERS system to get over the spooling issue....
This engine featured a two-stage set-up; a gas-generating turbine fed a second turbine that was connected to an output shaft.
The lag problem was solved by fitting two waste-gates between the two turbines. At 1/3 throttle all the gasses were fed through the waste-gates and out the centre exhaust. This way the blades kept spinning but the engine generated no power. As more throttle was applied the waste-gates closed gradually, feeding more and more gasses to the second turbine. At full throttle the engine produced around 325 bhp, which was very impressive considering it only weighed 77 kg.
A further advantage of the turbine engine was its completely flat power curve, so it did not require a conventional gearbox. It was instead mated to a Continental gearbox that featured just one forward gear. A separate electric-motor was used if reverse was required. A quick-change differential was used so the final drive ratio could be adapted to each track's characteristics.
Target drones have been known for a long time but they are not the bulk of the UAV which tends to be tasked with reconnaissance and to a smaller degree with weapons deployment.flynfrog wrote:sorry this is completely wrong Ive built the turbines for some of them. Most have them have pretty old tech as far as matl. goes the focus is on low cost not highest performance. Most of your assumptions are being based off of 40s tech GT comparing them to ICE engines that don't exist.WhiteBlue wrote:I'm surprised that all the UAVs the military and civil operators use are fitted with piston engines and wankels then. Normally you would expect them to use turbines as in manned vehicles, but turbines don't seem to be able to reach the efficiency requirements for that application. So one wonders why such a strong commercial demand with a turbine friendly customer has not led to a viable solution?
75 kg/h at 440 kW means 170 g/kWh which is a long way away from current MGT territory.
The car was flying for just 325hp. I guess the flat power curve is responsible.machin wrote:Its quite a neat drive arrangement:-
Quote from here:- http://www.ultimatecarpage.com/car/2827/Howmet-TX.html
This engine featured a two-stage set-up; a gas-generating turbine fed a second turbine that was connected to an output shaft.
The lag problem was solved by fitting two waste-gates between the two turbines. At 1/3 throttle all the gasses were fed through the waste-gates and out the centre exhaust. This way the blades kept spinning but the engine generated no power. As more throttle was applied the waste-gates closed gradually, feeding more and more gasses to the second turbine. At full throttle the engine produced around 325 bhp, which was very impressive considering it only weighed 77 kg.
A further advantage of the turbine engine was its completely flat power curve, so it did not require a conventional gearbox. It was instead mated to a Continental gearbox that featured just one forward gear. A separate electric-motor was used if reverse was required. A quick-change differential was used so the final drive ratio could be adapted to each track's characteristics.
WhiteBlue wrote: It is an indisputable fact that gas turbines generally are a failure in land vehicles and cannot even compete in heavy applications like trucks and tanks. The only known mass application is the M1 Abrams main battle tank. It was politically motivated and has become a total disaster to the American tax payer when compared to the cost of highly efficient diesel propulsion systems.
nickle alloy stack ceramic diffuser electric couplingringo wrote:The funny thing is that those old engines weren't even designed for racing use.
Imagine if a GT is purpose built for racing?
I don't decree facts. I just record them. The 1963 Chrysler gas turbine car wasn't a success. The 50 units produced were not loved by the public (engine sound and MGU problems were recorded as complaints) and they did not meet the NOx emission legislation. The 1966 Dodge charger solved the emission problem but by then Chrysler had commercially failed due to their unsuccessful product development strategy. Those are facts.flynfrog wrote:WhiteBlue wrote: It is an indisputable fact that gas turbines generally are a failure in land vehicles and cannot even compete in heavy applications like trucks and tanks. The only known mass application is the M1 Abrams main battle tank. It was politically motivated and has become a total disaster to the American tax payer when compared to the cost of highly efficient diesel propulsion systems.
well since you can decree fact I guess we are done here
Did you even read my post above? The Chrysler turbine cars were a huge success better efficiency longer service intervals ect. Killed by the US govt as they thought them to be to risky.
the turbine indy cars were a few miles short of a one two at indy when the fuel pumps failed. They were quickly banned due to threats from piston teams to leave the sport.
Both of the big three had turbine prototype trucks and the engines were unbelievably tiny and light compared to the diesel counter parts. They never got to far in development as the companies didn't want to retool. From what I have been told the files were long sense lost they had much more torque with a similar fuel consumption.
You are also forgetting how much more streamlined a turbine car could be. no sidepods were cut off much drag allow for more aggressive wings so even if the motor made more power it could make it up in corner speed.