RE: Jaguar C-X75 cancelled
Discussion
RTH said:
Aircraft engines use enormous amounts of fuel - they load 100 tons of fuel on a 747
They can afford to be wasteful of fuel because they pay no tax or VAT on aviation fuel so it costs operators a quarter of what it costs road users.
LOL... tell that to Richard BransonThey can afford to be wasteful of fuel because they pay no tax or VAT on aviation fuel so it costs operators a quarter of what it costs road users.
Notorious for wanting his aircraft towed to the runway by tug so that he could avoid spooling up the turbines until the last minute.
s RTH said:
Aircraft engines use enormous amounts of fuel - they load 100 tons of fuel on a 747
They can afford to be wasteful of fuel because they pay no tax or VAT on aviation fuel so it costs operators a quarter of what it costs road users.
Ahem, it's not for the benefit of Airlines that there is no tax on jet fuel, if they did tax it, no one would be able to afford to fly. They can afford to be wasteful of fuel because they pay no tax or VAT on aviation fuel so it costs operators a quarter of what it costs road users.
CraigyMc said:
Here's some info on bladon jets' turbines in general.
http://www.lcv2011.co.uk/PRESENTATIONS/TSB-DOME/PD...
I found the size of the turbine blades interesting - 75mm for their 5-stage axial 50Kw turbine (that's about 75hp). I'd have guessed bigger than that - in old money it's 3 inch blades and a length of about 5 inches or so including the stators from end to end of the compressor assembly.
C
For the life of me i can't work out why you'd want to put the generator on the "hot" end of the shaft??.http://www.lcv2011.co.uk/PRESENTATIONS/TSB-DOME/PD...
I found the size of the turbine blades interesting - 75mm for their 5-stage axial 50Kw turbine (that's about 75hp). I'd have guessed bigger than that - in old money it's 3 inch blades and a length of about 5 inches or so including the stators from end to end of the compressor assembly.
C
Also, they use a boggo std Honda generator as a competitor? Really, a unit you can buy for less than £200, and is designed to be robust, quiet, simple, affordable and not to get a high specific output etc? A fairer comparison would be an F1 engine, under 100kg, over 750bhp.
Max_Torque said:
For the life of me i can't work out why you'd want to put the generator on the "hot" end of the shaft??.
I suspect the airflow on the way in is more important than the exhaust flow on the way out. For the record, the industrial 211 is similar:
Max_Torque said:
Also, they use a boggo std Honda generator as a competitor? Really, a unit you can buy for less than £200, and is designed to be robust, quiet, simple, affordable and not to get a high specific output etc? A fairer comparison would be an F1 engine, under 100kg, over 750bhp.
I think they point they were making was that their turbine is 30Kg all in, and needs no radiator. The F1 engine comparison is bonkers for lots of reasons - size, weight, cost, longevity, packaging, heat, noise, vibration, etc.
A comparison with something like the lotus triple Jag looked at is fairer - and they put that in there too.
C
CraigyMc said:
Max_Torque said:
For the life of me i can't work out why you'd want to put the generator on the "hot" end of the shaft??.
I suspect the airflow on the way in is more important than the exhaust flow on the way out. For the record, the industrial 211 is similar:Max_Torque said:
Also, they use a boggo std Honda generator as a competitor? Really, a unit you can buy for less than £200, and is designed to be robust, quiet, simple, affordable and not to get a high specific output etc? A fairer comparison would be an F1 engine, under 100kg, over 750bhp.
I think they point they were making was that their turbine is 30Kg all in, and needs no radiator. The F1 engine comparison is bonkers for lots of reasons - size, weight, cost, longevity, packaging, heat, noise, vibration, etc.
A comparison with something like the lotus triple Jag looked at is fairer - and they put that in there too.
C
The point i was trying to make, is that saying the axial turbine has a 20x power density than a reciprocating engine is misleading. It may do compared to a production Honda generator, that uses 20yo tech and is mass produced. I haven't seen a published number from the TSB sponsored project for BSFC. And i am wondering why that is?
If the axial turbine system was the answer, wouldn't Honda, a company with massively more resource than the small startup enterprises developing turbines, already be making them by now?
The other issue that isn't even mentioned in that document is exhaust emissions. And i know why they haven't mentioned it, because it really is a bit of a nail in the turbines coffin unfortunately. With current aftertreatment system, the engine must operate stoichometrically in order to allow the catalyst to function, a turbine engine does not operate stoichometrically, because it uses the excess air to cool the hot section. Running one at such a load point, move the fuel consumption from poor to catastrophic, and requires hot side materials like inconel and titanium to withstand the heat. All of which are a major PITA and add £££'s to the cost.
Because tubrine systems are "continuous" in their operation, they have charactistically low raw exhaust emissions, but unfortunately, such is the march of progresss and legislation, low is not good enough when it comes to passenger car pollutant emissons. However, there is probably an aftertreatment system that will allow a turbine engine to meet passenger car exhaust emission limits, but it doesn't exist yet, so that's yet another thing you have to develop before the technology becomes "realistic". And that takes yet more money and adds yet more time to the program (and not to mention a huge risk, would you hand over lets say £100M to start a program that is not guaranteed to actually work?? nope, me neither) Added to which, the impact of that aftertreatment system on engine performance almost certainly isn't factored into their "power density" and "efficiency" calculations.
The final issue, and probably the most diffcult to overcome is the fact that car OEM's are notoriously conservative! No way do any unproven technologies get included in the program plan for a new platform that is going to sell in any volume. It's just too "risky"
IMO, turbines and other slightly unconventional combustion engines all face their biggest risk from fuel cell and battery technology. The car of the future is absolutely going to have an electric traction system, the only bit open to question is what the system for energy storage and conversion is going to be. Any significant breakthrough in battery technology immediately kills them stone dead (may not happen, but who knows, it's a fast moving area) and no one wants to (or can afford to) back the wrong horse! It also looks like broadly, the cost and effort of developing a practicable fuel cell is similar to that of a turbine/generator system. Yet the fuel cell has no tailpipe exhaust emissions at all, excellent NVH and no moving parts (high reliability), and is a "scalable" technology. Faced with those benifits, it's no wonder companies like Honda have pinned their colours to the mast and backed the development of FC's over other technologies.
In the short term, range extenders based upon conventional (and less risky as far as the OEM's are concerned) reciprocating IC engines are and will continue to be the lead programs.
PS: the "multi spool" RB211 engines probably have the PTO on the hot side of the engine to reduce the length required of the highspeed shaft (to avoid whirl). The single shaft turbine being developed by Bladon jets could take power off either end i think (may be some other good reason not to do so). A good reason to do so would be that your SR generator can then be effectively cooled by the intake air!
PPS: this is quite a nice roundup of the various range extending technologies and their status:
http://www.atcentre.nl/images/stories/publications/public/atc%20trend%20analysis%20-%20range%20extender%20technology.pdf
Edited by anonymous-user on Saturday 15th December 12:52
I havent been this dissappointed since the last time a jet engined concept car was cancelled...
That's all the C-X75 was. A concept car. A chance for the engineers to test new ideas, designers to seek new design areas for future models, and to gauge crows reaction. It has done its ob tremendously well, and taught JLR a lot about car based turbine technology
That's all the C-X75 was. A concept car. A chance for the engineers to test new ideas, designers to seek new design areas for future models, and to gauge crows reaction. It has done its ob tremendously well, and taught JLR a lot about car based turbine technology
Triple7 said:
RTH said:
Aircraft engines use enormous amounts of fuel - they load 100 tons of fuel on a 747
They can afford to be wasteful of fuel because they pay no tax or VAT on aviation fuel so it costs operators a quarter of what it costs road users.
Ahem, it's not for the benefit of Airlines that there is no tax on jet fuel, if they did tax it, no one would be able to afford to fly. They can afford to be wasteful of fuel because they pay no tax or VAT on aviation fuel so it costs operators a quarter of what it costs road users.
Air travel is getting crazy cheap though - it costs about the same to drive to my local airport as it does to fly to Spain, and its not very far away (about 25 miles, the airport that is, not Spain).
cml said:
Air travel is getting crazy cheap though - it costs about the same to drive to my local airport as it does to fly to Spain, and its not very far away (about 25 miles, the airport that is, not Spain).
I would argue the point...Air is not getting cheaper, it's just road/rail is now silly money
Scuffers said:
cml said:
Air travel is getting crazy cheap though - it costs about the same to drive to my local airport as it does to fly to Spain, and its not very far away (about 25 miles, the airport that is, not Spain).
I would argue the point...Air is not getting cheaper, it's just road/rail is now silly money
I still don't get how a private transport bus/train company gets Govt subsidies to run and then makes a profit to give to shareholders and keeps putting fares up above inflation!
Max_Torque said:
Lots of good stuff
Very true. The C-X75 wasn't really about the turbine though - that was just added cool. It was an electric car using a fuel tank and engine instead of a battery, and if a battery that was capable of meeting the requirements of usage in terms of capacity, cycling, and recharge speed became available, no doubt it would have been reasonably easy to slot in. williamp said:
I havent been this dissappointed since the last time a jet engined concept car was cancelled...
That's all the C-X75 was. A concept car. A chance for the engineers to test new ideas, designers to seek new design areas for future models, and to gauge crows reaction. It has done its ob tremendously well, and taught JLR a lot about car based turbine technology
Have you read ANY of the previous posts on this thread. ?That's all the C-X75 was. A concept car. A chance for the engineers to test new ideas, designers to seek new design areas for future models, and to gauge crows reaction. It has done its ob tremendously well, and taught JLR a lot about car based turbine technology
Any disappointed C-X75 customers can spend some small change on this low mileage XJ220
http://www.ebay.co.uk/itm/Jaguar-XJ-220-Stunning-c...
http://www.ebay.co.uk/itm/Jaguar-XJ-220-Stunning-c...
Max_Torque said:
Ok, how about a modern motorbike engine? How heavy for 50kW? Not very is the answer (when you think that sportsbikes are making nearly 200bhp, and have a multispeed gearbox attached too!
Even with the lightest available bike engine capable of 75bhp, you're still talking about a lot more than 30Kg - more like double. Then add the generator, which is included in the bladon system's 30Kg.A bike engine isn't really the best sort of solution for this anyway, in terms of IC engines. If you want efficiency, you're really talking about something designed specifically for the purpose, not something designed to have tractibilty and power through a rev range. Something like Lotus's range extender monobloc engine, which a number of 3rd parties are taking pretty seriously, is what you want.
Max_Torque said:
The point i was trying to make, is that saying the axial turbine has a 20x power density than a reciprocating engine is misleading. It may do compared to a production Honda generator, that uses 20yo tech and is mass produced.
Nobody said they have 20x the power density in this sort of application.Bladon mention that number when talking about turbines in general in their PDF.
You don't see any widebody airliners powered by a different sort of engine, do you? Presumably that's something to do with efficiency?
Max_Torque said:
I haven't seen a published number from the TSB sponsored project for BSFC. And i am wondering why that is?
Perhaps it's because their result was to take a 2.0 petrol focus and downsize it to a 1.0 turbo triple, adding some battery hybrid tech along the way make it meet (in one form) the CO2 standard of an existing, retail-available prius?Page 142 of 146: http://www.cenex.co.uk/LinkClick.aspx?fileticket=s...
What's that got to do with turbines?
Max_Torque said:
If the axial turbine system was the answer, wouldn't Honda, a company with massively more resource than the small startup enterprises developing turbines, already be making them by now?
A1. You have to ask why the world's largest internal combusion engine maker wants to keep making internal combusion engines? Business decisions aren't the same as engineering ones. That was my point many posts ago.A2. Honda do make turbines anyway - they actually make a whole private jet. http://gehonda.com/products/hf120/pdf/hf120_datash...
Max_Torque said:
The other issue that isn't even mentioned in that document is exhaust emissions. And i know why they haven't mentioned it, because it really is a bit of a nail in the turbines coffin unfortunately. With current aftertreatment system, the engine must operate stoichometrically in order to allow the catalyst to function, a turbine engine does not operate stoichometrically, because it uses the excess air to cool the hot section. Running one at such a load point, move the fuel consumption from poor to catastrophic, and requires hot side materials like inconel and titanium to withstand the heat. All of which are a major PITA and add £££'s to the cost.
Actually bladon do point to their jets making low NOx emissions (less relevant in the UK than in places like California).You haven't shown that turbine fuel economy is poor, you've just said it is without anything to prove it.
Max_Torque said:
Because tubrine systems are "continuous" in their operation, they have charactistically low raw exhaust emissions
They have low emissions for a given amount of power because they are pretty efficient at turning fuel into motion.Max_Torque said:
but unfortunately, such is the march of progresss and legislation, low is not good enough when it comes to passenger car pollutant emissons.
Er, yes it is. If cars were required to produce no emissions at all at the tailpipe, we'd all have to be driving stuff with similar tech to the Nissan Leaf (which would be nonsensical given where the electricity was generated: in many cases with fossil fuels like coal and gas). Ironically, much of this will have been generated by combined cycle gas powerplants using the same sort of gas turbines you're saying are inefficient: http://www.decc.gov.uk/en/content/cms/statistics/e...Emissions standards today would have been impossible to meet with tecnology from 20 years ago.
Max_Torque said:
However, there is probably an aftertreatment system that will allow a turbine engine to meet passenger car exhaust emission limits, but it doesn't exist yet, so that's yet another thing you have to develop before the technology becomes "realistic". And that takes yet more money and adds yet more time to the program (and not to mention a huge risk, would you hand over lets say £100M to start a program that is not guaranteed to actually work?? nope, me neither) Added to which, the impact of that aftertreatment system on engine performance almost certainly isn't factored into their "power density" and "efficiency" calculations.
You slap a £100m price tag on something to make it seem unattainable, ignoring that in industry gas turbines run with catalysts already.How about they start with the existing stuff (for industrial use) and work from there?
Max_Torque said:
The final issue, and probably the most diffcult to overcome is the fact that car OEM's are notoriously conservative! No way do any unproven technologies get included in the program plan for a new platform that is going to sell in any volume. It's just too "risky"
That didn't stop tesla from building an electric toy for hollywood types, and it doesn't seem to be stopping Fisker, GM (ampera/volt thingy) or any of the other range extended cars from being developed.You could argue that conservatism in engineering is going to stop progress until you're blue in the face.
You would have to show why OEMs didn't try out or progress with new technologies like fuel injection, turbochargers, high pressure direct injection, variable valve timing, varliable lift, etc etc etc.
At what point are you saying OEMs became conservative? Was it recent?
Max_Torque said:
IMO, turbines and other slightly unconventional combustion engines all face their biggest risk from fuel cell and battery technology.
The concept in question paired up some small turbines with batteries. Why is this a risk? They work together: electricity for immediate response, turbine for efficiency and quick refuelling.Max_Torque said:
The car of the future is absolutely going to have an electric traction system, the only bit open to question is what the system for energy storage and conversion is going to be. Any significant breakthrough in battery technology immediately kills them stone dead (may not happen, but who knows, it's a fast moving area) and no one wants to (or can afford to) back the wrong horse! It also looks like broadly, the cost and effort of developing a practicable fuel cell is similar to that of a turbine/generator system. Yet the fuel cell has no tailpipe exhaust emissions at all, excellent NVH and no moving parts (high reliability), and is a "scalable" technology. Faced with those benifits, it's no wonder companies like Honda have pinned their colours to the mast and backed the development of FC's over other technologies.
Forgive me for pointing this out but - doesn't the clarity run on hydrogen?Personally I can't see a whole transport system being able to do this (whereas you can runa whole transport system on oil-based fules like diesel, petrol and kerosene). My concern is for the fact that hydrogen has rediculous handling characteristics all the way through the storage and supply process. How big would a hydrogen tanker have to be to carry the same amount of fuel as one of today's bulk carriers, in terms of energy per volume? The boat would have to be miles long to get anywhere near. Also - hydrogen is a cryogenic fuel. The tanker would develop its own iceberg.
It's not a practical volume technology in my opinion, but I wouldn't mind being wrong.
Max_Torque said:
In the short term, range extenders based upon conventional (and less risky as far as the OEM's are concerned) reciprocating IC engines are and will continue to be the lead programs.
Nobody's arguing that IC engines are anything other than the leading option. On the other hand, nobody has demonstrated an engineering reason why that's the case either - it boils down to money and immediacy, not the best engineering solution available.Max_Torque said:
PS: the "multi spool" RB211 engines probably have the PTO on the hot side of the engine to reduce the length required of the highspeed shaft (to avoid whirl). The single shaft turbine being developed by Bladon jets could take power off either end i think (may be some other good reason not to do so). A good reason to do so would be that your SR generator can then be effectively cooled by the intake air!
PPS: this is quite a nice roundup of the various range extending technologies and their status:
http://www.atcentre.nl/images/stories/publications/public/atc%20trend%20analysis%20-%20range%20extender%20technology.pdf
I've read hooker's biography too. PPS: this is quite a nice roundup of the various range extending technologies and their status:
http://www.atcentre.nl/images/stories/publications/public/atc%20trend%20analysis%20-%20range%20extender%20technology.pdf
C
Ok, i'm going to try to say this in the simplest way i know how:
A gas turbine engine cannot ever be as efficient as a reciprocting piston engine in terms of converting fuel energy to useful work.
This is for two fundamental reasons:
1) Compression ratio: The thermal efficiency of a heat engine is controlled primarily by it's cycle compression ratio. A reciprocating piston engine can have a nearly limitless compression ratio in a single "stage". A turbine engine, that uses blades to accelerate air, and then convert that dynamic pressure to static pressure can have a high overall CR, but needs multiple stages to do that, which is less efficient (leakage, windage etc)
2) Heat loss. An IC engine looses a proportion of it's working fluid heat to the engine. The total heat lost is controlled by the surface area of the hot parts. In this case, the fundamental physical properties of surface area to volume ratio matter. The smaller volume system you have, the larger the ratio of surface area to volume you have. Hence, as you downscale an engine, it gets less efficient (because more heat is lost to the engine, rather than being used as useful work on the piston. For a turbine engine, this is even worse, because being continuous, the compression, combustion, and power extraction processes all take place at a different physical location, and hence you have a much much larger surface area through which to loose heat.
Hence, turbine engines have a higher specific fuel consumption than that for reciprocating piston engines. Basic physics makes this the case, and the smaller you make your engine, the worse it gets
For an aeroplane, where currently specific power is the most important factor (needs low enough weight and high enough power to get off the ground), turbines are the best choice. However, as fuel costs soar, and environmental pressures on pollutants increase, the aeroplane is likely to face a hard time in the next 50 years. Significant work si already going on to develop high power diesel CI engines for aeronautics, in order to leverage that technologies fuel economy benefits.
So, as i hinted above, why haven't Bladon Jets published a BSFC map for their engine? If it's as good as a reciprocating piston engine, then just publish the data and we can stop speculating about it!
A gas turbine engine cannot ever be as efficient as a reciprocting piston engine in terms of converting fuel energy to useful work.
This is for two fundamental reasons:
1) Compression ratio: The thermal efficiency of a heat engine is controlled primarily by it's cycle compression ratio. A reciprocating piston engine can have a nearly limitless compression ratio in a single "stage". A turbine engine, that uses blades to accelerate air, and then convert that dynamic pressure to static pressure can have a high overall CR, but needs multiple stages to do that, which is less efficient (leakage, windage etc)
2) Heat loss. An IC engine looses a proportion of it's working fluid heat to the engine. The total heat lost is controlled by the surface area of the hot parts. In this case, the fundamental physical properties of surface area to volume ratio matter. The smaller volume system you have, the larger the ratio of surface area to volume you have. Hence, as you downscale an engine, it gets less efficient (because more heat is lost to the engine, rather than being used as useful work on the piston. For a turbine engine, this is even worse, because being continuous, the compression, combustion, and power extraction processes all take place at a different physical location, and hence you have a much much larger surface area through which to loose heat.
Hence, turbine engines have a higher specific fuel consumption than that for reciprocating piston engines. Basic physics makes this the case, and the smaller you make your engine, the worse it gets
For an aeroplane, where currently specific power is the most important factor (needs low enough weight and high enough power to get off the ground), turbines are the best choice. However, as fuel costs soar, and environmental pressures on pollutants increase, the aeroplane is likely to face a hard time in the next 50 years. Significant work si already going on to develop high power diesel CI engines for aeronautics, in order to leverage that technologies fuel economy benefits.
So, as i hinted above, why haven't Bladon Jets published a BSFC map for their engine? If it's as good as a reciprocating piston engine, then just publish the data and we can stop speculating about it!
To be clear also:
Current Off Highway emissions limits for Europe are nowhere near as draconian as the current passenger car tailpipe emissons limits. Industrial power generation limits are even higher than for Off Highway prime movers. No current turbine engine system for which i have pollutant figure for could even be started once during the NEDC cycle without exceeding the PE limits, let alone do any useful work during that cycle. We are talking about requiring a quantum leap in raw exhaust emission reduction to become viable for passenger car useage. (of course, this IS possible, as i mentioned above, but it will be expensive and time consuming to engineer, which is enough to put off the OEM's) (like JLR.........)
Current Off Highway emissions limits for Europe are nowhere near as draconian as the current passenger car tailpipe emissons limits. Industrial power generation limits are even higher than for Off Highway prime movers. No current turbine engine system for which i have pollutant figure for could even be started once during the NEDC cycle without exceeding the PE limits, let alone do any useful work during that cycle. We are talking about requiring a quantum leap in raw exhaust emission reduction to become viable for passenger car useage. (of course, this IS possible, as i mentioned above, but it will be expensive and time consuming to engineer, which is enough to put off the OEM's) (like JLR.........)
Finally: Battery system improvements pose the biggest risk to range extender and hybrid developments becuase something like a 100% improvement in energy storage would be enough to render a hybrid as un-necessary.
The simplest technology, with the lowest cost, and most reliability is a pure electric car. It needs a traction motor, a gearbox, an inverter/PE, and a battery system. Only a few moving parts and gives very flexible packaging. If battery energy density increases to the point were a typical electric car can have a range of say ~300 miles range eztenders would be a dead end street for the vast majority of passenger car platforms.
Compared to a hybrid or range extended platform, which is a hugely complicated undertaking, which a massive number of different systems than need to be co-developed and integrated. (Take a good long look at the shear number of components and systems required to make a Vauxhall Ampera/Chevy Volt actually work for example!)
So, an OEM could spend easily £250M developing a turbine based RE system, and then find it is obsolete over night, when battery tech advances. Now, i'm not saying that battery tech is suddenly going to take a similary quantum leap in energy density, but given the worldwide focus on battery system development now underway, i wouldn't want to bet against it in say the next 5 to 10 years. Which is the sort of timescale that it will take to produce a viable volume production turbine based RE system.
The simplest technology, with the lowest cost, and most reliability is a pure electric car. It needs a traction motor, a gearbox, an inverter/PE, and a battery system. Only a few moving parts and gives very flexible packaging. If battery energy density increases to the point were a typical electric car can have a range of say ~300 miles range eztenders would be a dead end street for the vast majority of passenger car platforms.
Compared to a hybrid or range extended platform, which is a hugely complicated undertaking, which a massive number of different systems than need to be co-developed and integrated. (Take a good long look at the shear number of components and systems required to make a Vauxhall Ampera/Chevy Volt actually work for example!)
So, an OEM could spend easily £250M developing a turbine based RE system, and then find it is obsolete over night, when battery tech advances. Now, i'm not saying that battery tech is suddenly going to take a similary quantum leap in energy density, but given the worldwide focus on battery system development now underway, i wouldn't want to bet against it in say the next 5 to 10 years. Which is the sort of timescale that it will take to produce a viable volume production turbine based RE system.
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