Why has the Bombardier Jet Train not been put into commercial use? They would be perfect for Amtrak’s Cascade route pulling the Talgo’s.
It’s an Acela power car with a jet-engine derivative gas turbine engine. Like all gas turbines, it has two effective fuel efficiency settings … shut-down or wide-open full bore.
The main problem, IIRC, is where to run it. The only railroad in the US willing to let trains run as fast as the JetTrain needs to in order to be practical is Amtrak, on the NEC.
With this type of technology, Turbos were practical with low fuel prices. They are inefficient when run at part load. The genset concept can restore some efficiency, but that adds complications.
IIRC correctly ,Bombardier pinned much of it’s hopes for production orders for the Jet Train on proposed Florida and Texas high speed rail projects that failed to be built.
The thought being that the high fuel consumption would be less of an economic deficit when compared to the cost of building and maintaining catenary…
What I’d like to know at this late date is what happened to the JetTrain prototype? The last I heard is that it was languishing in storage at TTI in Colorado Springs.
I believe that is correct.
A point to note not highlighted in this thread is that it doesn’t have a turbine.
The turbine was leased from the US Marine Corps from a stock held as spares for the Air Cushion Landing Craft which use four of these each for both lift and propulsion. The turbine lease was for the duration of the trials and it went back into USMC stores when the trials concluded.
If anyone wanted to run the power car, they could purchase, or lease a turbine as Bombardier did for the trials.
But it is basically an Acela power car without a transformer or pantograph. If an Acela power car was damaged, Amtrak could convert the Jetrain car to replace it but that hasn’t happened either.
But it isn’t a complete power unit that people are ignoring. Nobody wants to put up the money to run it, given the cost of buying or leasing a turbine.
Peter
Frankly, there’s nothing the Jet Train could do that a Charger can’t do more efficiently.
Turbine engines do not fare well at low altitude when it comes to fuel consumption.
The denser air at low altitude demands more fuel than it does in the rarified upper reaches of the flight levels. That should explain why long range flights strive to get as high as possible in the fupper flight levels. There is substantial fuel savings to be had at those altitudes.
There are hazards that high off the ground where a sudden decompression of the plane could be instanty fatal to passengers and crew but they are taken into consideration before the flight.
I enjoy flying private and like flying below 15.000 ft. Oxygen is requieremt a that altitude but I did not find it a problem.
Thanks,M636C,
I did not know that about the turbine lease. Even though it’s carcass is rotting in the desert in CO, at least we know where it is.
Can anybody zero me in on where it might be on Google Earth or is it stored inside?
I was always under the impression that fuel efficency rises because of the lower air temperatures, not because of air density.
About 15 years ago this thing came out to Alberta for a promotional tour, pulling one Amfleet coach. At the time a study had just been completed which recommended upgrading the existing Canadian Pacific Edmonton-Calgary line to handle much higher speeds. The JetTrain would have allowed this without the initial expense of electrification, and would also have solved the clearance issues around overhead wires.
But nothing ever came of that proposal, and the prototype never returned to western Canada after that tour.
Perhaps lower air resistance in the thinner air too?
Seems to be varying answers online, but here’s one that matches what I thought was the reason behind it.
https://www.quora.com/Why-are-jet-engines-more-efficient-at-higher-altitude
Lots of stuff out there about air density though as well. I wonder if we have anyone here with a degree in aeronautical engineering that could shed some light now that I’m curious?
Naturally aspirated piston engines lose power as you gain altitude, with a loss of 2-3% for every 1000 feet gained. Turbocharging or other forms of forced induction can reduce or even eliminate this derating.
Not sure how gas turbines react though.
Interesting question. One of the You Tube channels I subscribe to is a flight channel where the pilot flies a Daher TBM-850 turboprop with a Pratt & Whitney Canada PT-6 engine. If the flight is long enough he flies at around 30,000’ depending on direction of the flight. This is for efficiency, cruising speed, and weather.
Jet engine performance limited by temprature.
Early turbojets used water injection on takeoff to reduce inlet temprature, also the cooler air is denser and when compressed provide a better fuel/air ratio providing more thrust generation.
The issue with turbine powered airplanes fuel consumption at low altitudes is that turbine engines lose efficiency when “turned down” - i.e. they do their best running near max power. Most energy efficient flying speed is usually said to be 1.3 times stall speed - at 40,000’ feet cruising speed isn’t much past the 1.3 times stall speed at that altitude. 100% power at 40,000’ feet is quite a bit lower that at sea level, so the engines are running close to flat out at cruise.
Issue with turbines in trains is similar, as the prime mover would be running considerably less then full power most of the time and thus at a lower efficiency. The 4,500HP UP GTEL of the 1950’s used about 450 gallons per hour at full throttle and 200 gallon per hour at idle - a 4,500HP diesel engine may use 5 to 10 gallons per hour at idle.
- Erik
It is a lot more complicated than at first blush. First it is the aircraft design. Higher altitude means less air resistance so less power needed. There are aircraft that are actualy more efficient at lower altitudes. The A-300 is one and its most efficient trip altitude ( not fuel consumption ) is between 25,000 ft and 27,000 feet. It has a high lift wing that akes a lower altitude better. Since it flies at a lower altitude its true airspeed is much faster than at high altitudes. Total fuel cosumption is less for a trip.
Outside air temperature is the controlling factor. The speed of sound is dependent exclusively on air temperature. Most aircraft are designed to cruise at a defined fraction of the speed of sound (mach ) . Usually about Mach .80 although a large differences for biz jets. Standard temperature “usually” decreases 2C per thousand feet. Starting at sea level’s 15C temp decreasing to about -50C above that temp remains same so less air resistance, Now that is just standards and know there are major variations espeially at the poles or equator.
Jet engines actuallly produce less thrust at higher altitudes but the aircraft differences more than make up. Each model is different of course but as a general rule fuel flow equals thrust . Better later designs have more thrust per pound of fuel flow.
Jet engines, turbo props, turbo shafts that just operate at close to sea level have different designs than a jet designed for high altitude service. GE’s CF6-50s -80 s are major block cores for back up generators and many navy ships
The Bombardier JetTrain was like an evolutionary step backward from the ALPS locomotive toward the Amtrak turboliners – it involves no more than a turboshaft engine driving a transmission. To my knowledge this involves the same general construction idea as the PT6/ST6 in the TurboTrain, where the traction turbine is free from the stages that drive the compressor and therefore can turn at any required speed while the compressor speed is optimized. There is no point for ‘fan bypass’ in these designs, as there is neither prop or reaction thrust; the only output that matters is torque via the power turbine shaft. This is not a design like the NYC jet RDC that might benefit in some way from high bypass or geared-fan engines.
The high “idle” fuel consumption is a consequence of the required power to run the compressor at required volumetric throughput and pressure to keep the combustors stable in firing. (That’s a different way of looking at what erikem was calling ‘turndown’) How much of the resulting combustion gas goes through a power turbine is optional in this design, but any of it that isn’t directly used will have to be wasted.