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UnnaturallyAspirated
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How does one say "I need more cowbell" in Bavaria?
TT: I've been accused of several things on this blog, but generousity is not one of them. In all honesty, I've have not been as critical of them as some others, mostly because i'm secretly routing for them. Just a few smart guys on a shoestring budget working out of rented space in a machine shop doing everything themselves. They really believe in it and are committed to taking the technology as far as it will go. I'm not very hopefull but am routing for them anyhow. This is a stark contrast to Scuderi in just about every way. UA
Seen the machine in person and spoken with the founder. A clever device that seems to work well for the water treatment plant application which it was originally intended, however, i don't see it catching on in automotive. it is exceptionally large machine relative to the engine for a given displacement which presents packaging as well as cost issues. Performance at meaningful pressure ratios is still unimpressive compared to a conventional centrifugal machine. Granted they do not boast variable displacement capability, but at these efficiency levels, it is relatively meaningless. Would like to see 3rd party test results. UA
Regarding the merit of UofW's publications and who is more trustworthy... -as a member of SAE, reviewer of papers, and a session organizer, I can confirm that any paper published by SAE has had typically 3 people review it, however, this doesn't mean that the work published inside is irrefutable. Everything needs to be taken with a grain of salt. It is not unheard of to see 2 papers on the same subject come to completely different and contradictory conclusions, even at the same conference in the same year. Both came to logical conclusions based on the work they did. Usually the difference is in the scope of the work and how thoroughly a hypothesis is tested and the assumptions made by the authors. Because they do not present their whole body of work to support their findings in their papers, it is often impossible to tell who is right. Moreover, it is unlikely that somebody doing cutting edge work has a peer with the detailed first hand experience to really challenge the work as a reviewer. If the paper was on a well explored and understood topic, it would not qualify as research. Also, for many research institutions (universities), researchers (professors) performance is measured by the quantity of their publications. This can have a big impact of whether someone will ever make tenure or not. Unfortunately, quality is sometimes left by the wayside in the process. Thus, in my opinion, university publications are no more (or less) trustworthy than those of a for profit manufacturer whose interests and motive are more obvious for all to see. UA
-GdB if you read the paper i referenced, it is very clear that RCCI and other LTC strategies are very sensitive to air charging system efficiency. The EGR levels result in relatively high levels of boost to provide sufficient fresh air to reach the target lambda. With LTC, residual exhaust gas energy is substantially reduced which is in essense the source of available energy to drive the turbine. The combination of low available exhuast energy and demanding compressor power requirements results in substantial negative engine backpressure that the engine must overcome. In the end, this means that pumping work to drive the turbocharger significant consumes gross power and erodes Brake Thermal Efficiency. Some will argue that this just means that turbochargers will have to get better, but as you may have guessed by my screen name, i happen to know a thing or two about this subject and i would not place bets on improvements that this technology requires anytime in the near future. Regards, UA
Reitz and team are doing very interesting work, however, it's time to progress beyond single cylinder testing indicated efficiency and put the work in meaningful terms of Multi-cylinder Brake Efficiency. There are a number of key ingredients in his recipe that are built into Indicated measurements which can not be assumed for the real world, especially means to provide the mixture of fresh air and diluent at the assumed efficiencies. These are serious hurdles which are not new and are unlikely to be overcome anytime soon. This is good progress but claiming victory before realizing results in a production type engine using real turbochargers is premature. Based on work presented at the same conference in paper 2011-01-0358, it is unlikely that peak BTE will exceed that of a the current conventional commercial diesel engine. UA
@PB&J 1) You don't need the white papers if you can talk directly with the people doing the work or closely associated with it. This is a privelledge i enjoy in my position. 2) I didn't say there isn't any industry interest. Nobody can afford to ignore claims of breakthrough technology as they risk being left behind if it turns out to be real. That is why the OE's are having their own study's being done. They will make their own assesment based on work they fund to get answers they believe to be credible. The end result of this is a decision to either license the technology or not. Even if they decide to license, this is often a hedge just in case which is standard procedure and should not be confused with an intent to go to production. This simply secures the right in case they decide to use it later. Kind of an insurance policy. 3) SwRI is a research gun for hire. Just about anyone can hire them to do investigations for them. I have, and they do a good job. The point of my note was to point out that just becasue SwRI is hired to do something, it doesn't mean that they endorse the idea, and that publicity released by the funding entity does not necessarily reflect the opinions of SwRI. It is quite easy to take a piece of data out of context and twist it into whatever you want, especially when the topic is highly technical and the audience is not. UA
Don't confuse the work that SwRI was contracted to do for Scuderi as an endorsement by SwRI. Scuderi are experts in marketing and they use SwRI not only because they can't do the work themselvse, but also as a means to shape the perception that SwRI is their partner and a believer in the technology. SwRI is very professional and polite, but when you talk with them about the Scuderi project it is clear from just about everyone that this is simply a consulting project for a customer and that the press releases are hand from hand picked data which often is taken out of context. The real claims in this article have little to do with the Scuderi cycle and mostly about the benefits of hybridization. "...25% decrease in fuel consumption (i.e., up to 33% increase in MPG) was achievable with an SSC engine replacing the Sentra’s engine when factoring in fuel cutoff during deceleration and idle in the model". UA
Most of the technologies presented here are thinly disguised adverts based primarily on addressing one particular aspect without concern for myriad of others which usually are more important, however, this seems rather interesting. Mahle tends to do solid work and William Attard got my company's attention a few years ago when he finished his education. This one may actually makrpe it to production.
@ Globi- -re: CO2 emission and EV vs ICE, the link you provide is not compelling. It is summary of a study by an Electric Vehicle Team without any of the key assumptions which have a strong impact on the outcome which limits one's ability to review the quality of the work. It may sponsored by John Heywood, but without the assumptions (drive cycle, vehicle class, etc. ) the results can not be put in context. For instance, The ratings of the different powertrain technologies will change if they are evaluated over FTP75 vs US06 and similarly if they are fo a B-class sedan or a D-class. Even taken as is, it says that a diesel power vehicle is effectively as clean as a BEV. In this regard, the report is not far from many other analysis results i've seen. Go to an SAE, ASME or any other reputable and relatively unbiased proffessional engineering society symposium and you'll see equal number of studies with results on either side of the fence. In the end, it boils down to the assumptions. The researchers whose studies seemed most scientific and fair tended to yield results that were slightly unfavorable to BEV's which is why i tend to share this opinion. This is all hinged on the source of electricity for BEV's which will change over time, but it won't change quickly. Coal is simply too cheap and abundant and Nuclear too unpopular with the public. UA
A few thoughts on responses: -Just Capstone PR doing there job to advertise whatever good news they can since there is so little of it. -micro gas turbine generator makes little sense in this application. Bus market is extremely cost sensitive as their operators have little money of their own to spend and users aren't typically willing to pay a premium for better service. Buses are not weight limited so whatever advantage a gas turbine offers in weight savings is of little value. Any benefit in physical size reduction is moot given the poor energy storage efficiency of CNG and low efficiency of small gas turbines. if somebody wants or their is a need for a clean PHEV bus, they'd be better off using a simple ICE regardless of the fuel. -@ToppaTom- Well said -@Engineer-Poet- Right on -@Harvey D- you can't discount heat engine efficiency if you are concerned with GHG. Except for a handfull of countries who are already invested on nuclear, geothermal, or other non HC fuel source, most countries electrical grid produces as much CO2 by the time it gets to an electric car as does a modern ICE. This can be improved but it will take decades and trillions of dollars so it can not be ignored. -@SJC-stop start is definitely a great candidate for hybridization, but not so much for an ORC. Need high quality (high temp) heat and stop start is not conducive to this operating environment. Several recent studies have been conducted by NAS and other reputable scientific groups, all of which have shown that the economics don't come close to working for ORC until fuel prices increase by several times. -@Mannstein- centrifugal compressors suffer tip leakage too. small gas turbines use centrifs to keep them simple and low cost. you can get upwards of 6:1 pressure ratio with good efficiency in a single stage on a centrif which would usually take 4 axial stages. multi-staging a centrif becomes tricky so it isn't often done so if you want to go to higher pressure ratios and use actively cooled turbines, then axial machines are the only way to go. -@Aussie- Though i agree that $35/kw isn't a bad number for diesel engines, real engine costs are not well represented by such a simple metric. it depends heavily on other factors, such as emissions level, production volumes, BSFC, expected duty cycle, life. As an example, heavy duty engine costs have doubled in developed markets in the past decade due to emissions regulations with negligible improvement in fuel efficiency or durability. At any rate, suffice it to say that we looked at costing out a recuperated gas turbine in this power range for automotive use and came to a figure closer to 2-3X what an ICE costs in volumes 10,000 - 100,000/yr. UA
Glad to see more interesting cars being offered in the USA in the small car segment. My personal opinion is that part of the attraction Americans have for large cars is that the small cars have historically been deprived of interesting styling and void of quality components inside and out. The Mini has shown that there is a market for small cars if you don't penalize the buyer with a lack of content and I expect similar acceptance of the 500. Regarding the engine, I'm not impressed with the published performance values. Its hard to say how efficient it will be without seeing the BSFC maps, but the specific torque and spread between peak torque and rated power are not impressive, especially considering the capabilities of the valvetrain. UA
@Roger & EP, Did either of you go to the High Efficiency Engine Symposium or the Fluids and Lube meetings last month? Either way, what is your feeling on how these single cylinder lab engine results will translate into real measures of efficiency (BTE) in multi-cylinder format? I've yet to hear Reitz, Johanson or anyone else playing with XXXX (flavor of the week Low Temperature Combustion) strategy address how their concepts will avoid the significant drop usually seen if the concepts every make it that far. As an air-handling expert, what worries me is the ability to produce the in-cylinder conditions that are manufactured in the laboratory to achieve their results. The requirements usually involve fairly lean AFR with very high EGR rates requiring high boost levels and low engine backpressure. The resulting low temperature exhaust (~400C) creates a very challenging problem statement for the turbocharger to create the required boost. Long story short, i don't think they can do it if they unplugged their supercharger and actually let the engine backpressure, AFR, and EGR rate equalize with real tubocharger hardware. Whenever i've seen them challenged, they avoid they stonewall and rely on arrogant responses like "we've checked our math and it should work". Anyhow, i'd be interested to hear your thoughts on this subject. UA
Another marketing effort to keep the VC's happy that their money is being spent wisely, but not much content when you dig into the details. -Their comparison of efficiency relative to 2 other engines is more or less meaningless. The variation in performance from one engine design to another within a given size and power level is simply too large to draw any conclusions. Every engine manufacturer has to determine how to trade off cost, efficiency, operable range, power, packaging, NVH etc for the type of customer they sell to which is why the world hasn't converged on a consolidated recipe for engine design. -1D code predictions are good for directional guidance of evolutionary changes when the models are calibrated to test results. Any attempt to draw conclusions beyond this is an exercise in futility. -TC has made some comments about emissions, but has not made claim to what emission standard it is testing. Without emissions parity, efficiency comparisons are useless. Given that Lean stratified operation can only operate at relatively low load without NOx issues, they will have to either switch to Stoichiometric operation for most of the operating map and lose much of the lean benefit, or they'll have to add NOx aftertreatment to meet most of the developed world's emissions regs. This is a proven and viable solution, but the on-cost of such technology has made it a non-starter given the current cost of fuel (even in Europe). Even if one assumes NOx aftertreatment will be standard, the more relevant comparison is then a diesel engine given similar structure and required subsystems. -Comments regarding cooled EGR are also misleading. Its true this is very beneficial, and could be a way around NOx aftertreatment for lean operation, but it has already been proven to work with conventional injection technology. The problem with this approach is ignition systems and it isn't clear that TC's system makes this any easier. -Keep up the research though and hopefully you'll prove me wrong.
Why is everyone so hard up on PHEVs? Its like groundhog day on GCC. Its simply an electric car with an onboard generator. Until Batteries are cost effective and electric power generation switches over from coal to something cleaner, PHEV's will offer no CO2 advantage over conventional ICE's and will simply add $10k+ to the initial purchase price for a vehicle of equivalent performance. The only tangible benefit for the foreseeable future is reduced dependence on foreign oil which is a noble thing, but far from what is promised.
Though I think Honeywell fumbled in their sales pitch by touting the age of their "new" technology, I can't rationalize how a sane person would really conclude the delay is some kind of conspiracy. A more likely scenario is that the technology was available in the 80's, but not feasible for high volume, or cost effective manufacturing. Honeywell and their customers are in the business in the making money. If they could not pass on the cost to the consumer or its benefits were not needed to meet a CAFE standard or CO2 regulation, then there is little reason to put it into production. its ultimately about what is the most appropriate and cost effective solution for a given problem, not just what is the most efficient or advanced.
Most car manufacturers are in the business of making money, or least they aspire to. Making cool toys happens to be the method that they choose to accomplish their goal. Many of the manufacturers of 300k cars for sale today seem to be doing well enough to stay afloat and bring new products to market regularly, which suggests they have a compelling business case, either as stand alone, or as a flagship brand as part of a larger organization. vehicles without business cases either don't make it to market or go away soon after.
Roger, Clearly you are a fan of this concept, but I am surprised by your comments. You can't believe that a 140kw recip would not package in this car? This could easily be a 3cyl gasoline, or 4 cylinder diesel @.5L per cylinder. 5X weight difference is probably about right when you consider all the accessories, but even at this delta, what you are talking about is 250 lbs. Sure it isn't negligible, but no ground vehicle will give up 50% BTE for 250 lbs. Weight simply is not that important unless you are airborn. As for the supposed infinite life that Capstone and Bladon like to talk about with air bearings or gas turbines in general, this is total B.S. My company is one of the highest volume, highest technology air-bearing gas turbine manufacturers and consumers in the world. I can assure you they do wear out. Turbomachinery suffers from cyclic fatigue and airbearings have limited lift off cycles. As we agree, its a matter of physics. @ Kelly, Be sure to write Rattan Tata and beg him to put it into production. He championed the Nano and can bring this to life too if he chooses. Left to the marketing, finance, and engineering team, it won't happen because it doesn't have a compelling business proposition. UA
@ Kelly.... "If this is true, how does 580 kw get 500mi/15gal. = 32 mph?" With simple math, you can show that given their claimed Cd of .32, reasonable frontal area of ~2.2m^2 and rolling resistance of 0.012, it takes ~5.5kw to maintain 32mph. Likewise, 15 U.K. gallons of diesel fuel contain ~2,200MJ of energy. to travel 560miles at 32 mph,it takes ~15.5hrs at ~5.5kw which equates to ~350MJ of energy. 346MJ of work from 2,200MJ of potential energy = ~16% efficient from fuel to shaft power. this assumes they start with depleted batteries. if not, then the efficiency number goes down more. The reality is that their own numbers agree with physics which prove that it is not an efficient solution and a simple recip would be a substantially more efficient heat engine for this application.
@ kelly... if you are technically savvy, grab a thermodynamics book and run the calcs on a simple Brayton cycle (no recuperation, intercooling and single stage expansion) and you'll see that 15% if a pretty good value for BTE. Modern reciprocating engines at similar power levels are easily +30%. ie. typical 4cyl turbodiesel can achieve peak BTE of +37%. Gasoline engines are less efficient and more sensitive to off load cases, but still hover around 30% at peak island. The Gen III Prius engine is actually about 35% for a fairly wide operating region. Not sure where 580 kw, 500 mi/15 gal comments comes from. it doesn't take 580 kw to drive 32 mph and neither a gas turbine nor recip will go 500 miles on 15gal producing 580kw. Regarding average driving conditions, i don't disagree with you. Virtually no consumer really needs the performance that is offered by the vast majority of vehicles on the road.
@ kelly.... As for Tata's (Jaguars) specifications, the maths all add up. its simple physics. The point is that there is more to it than the specifications that they've posted. Its just my opinion, but this concept is a poser. You can drive it @ WOT for about 90 seconds, long enough to reach top speed once, but it won't run a track event, and will struggle to complete most Auto-X events. It will produce good CO2 numbers on the EU cycle but its well known that neither the NEDC nor FTP75 represent real world driving. In charge sustaining mode it will be about ~15% thermally efficient, hardly better than the 580kw reciprocating engine they seek to replace. Its like a hybrid between a Ferrari with a 1 gallon tank and a coffee straw for a filler and a Prius with a 2 spark plugs removed.
Try not to lose sight that this is a "concept". Though feasible, it relies on multiple unproven claims of technical breakthrough. Moreover, it does not make a compelling business case which is why we won't see it in production. Its fast, but there are a dozen other real cars on the market today with the same of better performance, not to mention it is only fast until the batteries are depleted which will take all of a minute of so. Once the gas turbines are powering it as it series hybrid, it only makes 188hp. As for efficiency, It may be a cycle beater on test due to its all electric operating potential, but in charge sustaining mode, it will be pretty bad. Small gas turbines are horribly inefficient reducing the specific power density larger gas turbines are famous for. To add further complication, the unrecuperated Brayton cycle is very inefficient from a specific fuel consumption perspective. Bladon makes numerous unfounded claims of technical breakthroughs to resolve both of these issues, but a review of their IP portfolio, including applications not yet granted shows no evidence of breaking new ground. This car would be much more efficient with a conventional recip of the same power level. In the end, its main attribute is its unique, but not differentiated powertrain. Tata may need this concept to gain attention to its premium brand now that its under new colonial ownership, but it doesn't need a production version to keep selling Jags.
oh...where to start? First challenge will be keeping it from crashing without excessively large clearances as rotordynamics will not be trivial. Next challenge will be keeping bearing losses to a minimum to avoid losing whatever aerodynamic benefit they have through ideal wheel size and speed matching. Final and most difficult issues will be CVT durability. Making it work for a short period should be possible as this demonstrator won't see significant hours of use, however, making it reliable for 500k miles or more exceeds state of the art for traction drive CVT technology. At a bare minimum, it will likely require that the traction fluid will need to be replaced regularly since it will be contaminated with exhaust gas leaking past the turbine seal. Assuming they best these hurdles at least for the short term, it will be great to see if they can can demonstrate a performance benefit. Turbocompounding is quite sensitive to turbomachinery efficiency. Performance at the design condition may be acceptable, but managing off design peformance will take more than a few guys at a startup to tackle. I wish them the best and look forward to the DOE report. Good Luck Ed!!
Tex, if you read their article carefully, they only claim the demonstrated fuel efficiency improvement over standard diesel engine buses, even though they clearly have other types of hybrids in their fleet. The reality as EP alludes to is that the big efficiency benefit in urban applications is due to regenerative braking and elimination of idle time. these are attributable to the hybrid architecture, not because of the type of heat engine they use. The problem with their approach (as well as other HD electrical hybrid solutions) is that there is a large discrepancy between the average power consumption and max power requirements. The bus may only need 30kw to keep up with average usage, but it will need 150-200kw in order to accelerate at a pace that doesn't make it a road hazard, or to climb a hill when loaded. That power will need to be available on demand and providing the energy storage to support such power levels without exceeding current state of charge limits is neither cost effective nor packaging friendly. Moreover, Capstone has avoided discussing the cost of the technology or the fact that there are not substantial quantities of other fuels for their microturbine to burn which makes that feature relatively valueless. It is for these reasons that most Heavy Duty hybrid solutions are leaning toward pneumatic-hydraulic energy storage rather than electrical, with power coming from conventional diesel engines using aftertreatment to meet emissions. it is simply a result of it being the best solution and most economical, not a conspiracy by the oil industry or automotive engineers worldwide. In summary, Capstone tries to confuse the issue by parading the benefits of hybridization as the benefits of a gas turbine while completely ignoring the cost of their gas turbine relative to a comparable IC engine or addressing the battery storage issue. P.S. if you read between the lines, 20 years ago the Rosen brothers understood the issue was more about the batteries than the heat engine which is why they were working on flywheel energy storage.
Tex, Knock yourself out and buy some stock in Capstone if you are so confident in your Masters Degrees. I cant claim to have such a big brain as you, but I happen to work closely with just about every truck and engine manufacturer and multiple recovering Capstone engineers and will not be making such investments myself. UA