 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / October 2005Wankel-Electric Hybrid?
When reading about the disadvantages of the Wankel rotary engine, some of the more prominent reasons listed are the lower fuel-economy, lower emissions quality as well as lower torque: http://en.wikipedia.org/wiki/Wankel_engine I'd like to ask if pairing up with an electric motor in a hybrid configuration couldn't serve to address the shortcomings. Using a lighter fuel like propane/methane/H2 could play to the Wankel's strengths while also reducing the emissions problem. The electric motor could provide the better torque at low rpm, while the wankel would extend the rpm/speed cieling. What are the pro's and cons of wankel-electric hybrid compared to reciprocating piston-electric hybrid? Comments? > When reading about the disadvantages of the Wankel rotary engine, some > of the more prominent reasons listed are the lower fuel-economy, lower [quoted text clipped - 14 lines] > > Comments? My guess is that you would get more bang for your buck from a small diesel paired to an electric motor. > When reading about the disadvantages of the Wankel rotary engine, some > of the more prominent reasons listed are the lower fuel-economy, lower [quoted text clipped - 14 lines] > > Comments? In a proper hybrid, the engine does not need flexibility, so I see no advantage on working to increase flexibility (rpm and load range). So, yes, in a sense a hybrid does make a poor flexibility engine useful. If the rotary can provide a better specific power (hp per weight) then it is a candidate, but it should also have good efficiency to start with, or else proping it up with hybrid mode seems like a bandaid rather than a good idea. > When reading about the disadvantages of the Wankel rotary engine, some > of the more prominent reasons listed are the lower fuel-economy, lower [quoted text clipped - 14 lines] > > Comments? Go to http://www.regtech.com/ to see the next actuall usable version of a rotary eng. now in protype testing and see the future. lighter, more efficent, cheeper. KB  SignatureThunderSnake #9 Warn once, shoot twice 460 in the pkup, 460 on the stand for another pkup and one in the shed for a fun project to yet be decided on Hi, I've read about this Randcam for a number of years now, and I guess I'm wondering why hasn't it taken off yet? What are the shortcomings of the Randcam? With its use of diesel, it seems to have better compression ratio than most wankels, although I wonder if this is at the expense of rpm-cieling. I also remember reading about the Dynacam, which features a circular arrangement of reciprocating pistons, and a sinusoidal cam. Again, I haven't heard much happening from that either, and I'm not sure what its drawbacks are. Gee, it's hard to believe that no further significant improvements are possible in engine design, with all the advances in CAD, materials, and even electronic valves. > Hi, > [quoted text clipped - 12 lines] > possible in engine design, with all the advances in CAD, materials, and > even electronic valves. Many of those "inventions" are based on a myth that since the connecting rod isn't perpendicular to the crank throw there is a loss of efficiency. The big breaktrough still to be made is the adiabatic engine where the combustion chamber and cylinder walls are uncooled and allowed to reach average temperature of combustion gases. This needs new materials and especially new lubricants. Petroleum oils coke at these temperatures. Since approximately one third of energy in fuel goes out exhaust in enthalpy of exhaust gases, one third goes into cooling system, leaving one third for useful work, an uncooled engine can be an enormous boost, almost doubling efficiency. Don Stauffer <stauffer@usfamily.net> wrote in news:Ufx_e.4$Be5.209 @news.uswest.net: >> Hi, >> [quoted text clipped - 25 lines] > one third for useful work, an uncooled engine can be an enormous boost, > almost doubling efficiency. The bigest impediment to adopting a new technoligy is almost due to the need to retool. The industry has a enormous inerita effect that will eventually be overcome when one of these invensions is shown to be too efficient and supperior to ignore. KB SignatureThunderSnake #9 Warn once, shoot twice 460 in the pkup, 460 on the stand for another pkup and one in the shed for a fun project to yet be decided on > Since approximately one third of energy in fuel goes out exhaust in > enthalpy of exhaust gases, one third goes into cooling system, leaving > one third for useful work, an uncooled engine can be an enormous boost, > almost doubling efficiency. There's a step missing there somewhere. Not removing the heat cannot automagically convert the heat to work. SignatureIf John McCain gets the 2008 Republican Presidential nomination, my vote for President will be a write-in for Jiang Zemin. Not anyone can invent a good new engine. As the early vacuum engine engineers pointed out, "it takes a philosopher to design an engine." Bret Cahill "manofsan@yahoo.com" <manofsan@gmail.com> writes in article <1127813302.784558.320830@g14g2000cwa.googlegroups.com> dated 27 Sep 2005 02:28:22 -0700: >When reading about the disadvantages of the Wankel rotary engine, some >of the more prominent reasons listed are the lower fuel-economy, lower [quoted text clipped - 12 lines] >What are the pro's and cons of wankel-electric hybrid compared to >reciprocating piston-electric hybrid? Wankel has higher emissions and lower gas mileage. Those are exactly the problems that the hybrid concept aims to solve. So a Wankel-hybrid would be better than a plain old Wankel but not as good as a piston-hybrid. Your light-fuel comment seems to apply equally well to piston-hybrids. The main advantage of the Wankel is its higher power-to-weight ratio, which would not come through in a hybrid because power and weight depend more on the size and type of battery than on the combustion engine. -- spud_demon -at- thundermaker.net The above may not (yet) represent the opinions of my employer. > When reading about the disadvantages of the Wankel rotary engine, some > of the more prominent reasons listed are the lower fuel-economy, lower > emissions quality as well as lower torque: > What are the pro's and cons of wankel-electric hybrid compared to > reciprocating piston-electric hybrid? Wankels have only 2 advantages: smaller size and weight and cheaper production (far fewer parts). Their hydrocarbon emissions are inherently higher because of the large surface area/volume of the combustion chamber. >>When reading about the disadvantages of the Wankel rotary engine, some >>of the more prominent reasons listed are the lower fuel-economy, lower [quoted text clipped - 7 lines] > inherently higher because of the large surface area/volume of the > combustion chamber. That higher surface area to volume ratio is also one of the reasons for lower fuel efficiency. At least, that is the case for any non-adiabatic Wankel, and I haven't heard of an adiabatic one yet. >When reading about the disadvantages of the Wankel rotary engine, some >of the more prominent reasons listed are the lower fuel-economy, lower [quoted text clipped - 14 lines] > >Comments? There is no reason to do a wankel based hybrid; unless, there is something about a wankel that makes it desirable. You left out that a wankel is smaller than a comparable piston engine, with no reciprocating masses and fewer parts. These might be reasons to go with a wankel, except that gas turbines are even smaller and have even less parts. The abysmal part-load performance of a gas turbine are solved by making it part of a hybrid that never runs the turbine at less than full rated power. Hi, I hear what you're saying, but turbines don't like to stop and start frequently, from my understanding., and you know that's going to be a requirement for normal driving applications. What I've also heard is that turbines also run hot and very noisily, and are considered to be fuel-guzzlers. Yet I've never quite understood why they're considered to be fuel-guzzlers if they're supposed to have relatively higher Carnot efficiency. I'd also think that modern advances in insulation would make the high temperatures of the turbine less dangerous to deal with. Is there any way to design a turbine that can have multiple optimal power ratings? Or could a turbine merely be switched on to recharge a battery/supercap that had dropped below 20% of its charge? Is the Wankel perhaps the best possible compromise between the reciprocating piston engine and the turbine? I'd suggested the Wankel because it seems to cater to the opposite end that an electric motor excels at. The electric motor seems good for high-torque acceleration in the low-velocity range ("low-gear"), while the wankel seems more specialized for the lower-torque higher-rpm range ("high-gear"). Comments? > Hi, > [quoted text clipped - 14 lines] > > snip Almost all GTs run with much excess air to hold down turbine temperature. Even with our best materials for turbine blades, they cannot run at flame temp. Now, the Carnot efficiency is dependent on using a high temp. Very expensive commercial and military engines get their high efficiency by running very hot (high TIT). So low efficiency and high temps do not go together. Yes, good insulation solves the high surface temps of GTs. I believe a good metallurgist or materials expert who can come up with a good material for turbine blades that allows very high temp, but yet, easy, low cost fabrication, can achieve fame and fortune. People have been trying for over half a century. I'd like to have a nickel for all the press releases that have been issued in last half century by some person or company who has claimed to have solved the problem. While turbines do not like wide operating range, this is also true of throttled gasoline engines, so in both cases this is a good reason to use with hybrid setup. 60% of the billions spent on R & D for gas turbines went to high temp. materials. GE had a carbon-carbon turbine that could take high compression stoichiometric flame temperatures but if any O2 got near it it would burn up -- not a good material for real life aviation engines. Materials science advances are more important than anything on earth so humanity is at the mercy of those voodoo witch doctors over at the mill or lab. Bret Cahill > What I've also heard is that turbines also run hot and very noisily, > and are considered to be fuel-guzzlers. 15-30 years ago, Mercedes said their turbine concept car would get 70 MPG on the freeway, 17-18 MPG city. Actually, then would it be possible/useful to literally fuse a turbine and electric motor together onto the same shaft, as a single integrated apparatus? Both roughly have the same geometry, with the shaft inside the cylindrical casing, and requiring tight tolerances for smooth rotation. Would this be feasible, and would there be any benefit to this? Exactly what is happening inside the partially-loaded/throttled-down turbine to make it less efficient? Lower compression ratio? >Actually, then would it be possible/useful to literally fuse a turbine >and electric motor together onto the same shaft, as a single integrated >apparatus? http://www.capstoneturbine.com/ Regards, Bill Ward > Actually, then would it be possible/useful to literally fuse a turbine > and electric motor together onto the same shaft, as a single integrated > apparatus? The generator would have to be capable of turning at a turbine's typically high shaft speed and the output, if AC, would be at a very high frequency. This can complicate the electronic design, but is doable. It would have the advantage of eliminating a reduction gear box. --Damon >> Actually, then would it be possible/useful to literally fuse a turbine >> and electric motor together onto the same shaft, as a single integrated [quoted text clipped - 7 lines] >It would have the advantage of eliminating a reduction >gear box. The biggest reason for going to a direct drive turbine (unlikely, but possible) is that the generator also becomes very small. Roughly speaking, for a given power, the product of length times radius times frequency will be constant across all possible AC machines. Losses go up with frequency, but if a 1000Hz generator can be economical, the turbine speed would be 60,000 rpm, not far out of line for an automotive turbine engine. A combination of battery power and stored compressor bleed air would make for reasonably fast startup. There is no complication in the electrical design, the problem is that at a higher frequency (power kept constant) more waste heat has to be extracted from a smaller machine. >>Actually, then would it be possible/useful to literally fuse a turbine >>and electric motor together onto the same shaft, as a single integrated [quoted text clipped - 9 lines] > > --Damon Actually, this is one reason the steam turbine was invented. People were having to GEAR UP the output of reciprocating steam engines driving commercial generators. Steam turbines turned faster, allowing higher frequency AC without gearing up. >Actually, this is one reason the steam turbine was invented. People >were having to GEAR UP the output of reciprocating steam engines driving >commercial generators. Steam turbines turned faster, allowing higher >frequency AC without gearing up. Not true, at all. For DC generators, all that matters is how fast the wires move under the pole pieces. Slower prime movers just mean that the generators have to have a larger radius. I have seen pictures of early generators that were several feet across, with what looked like a spoked wheel for a rotor. Not that the upper speed of a reciprocating steam engine was an issue, as a steam locomotive had no difficulty hitting a hundred miles an hour on straight level track with a short enough rebound time. The really wide generators were needed for hydraulic turbines, as they were quite large and only spun at about 60 to 240 rpm (one to four hertz). AC generators deal with a low mechanical frequency by multplying the mechanical frequency by a large number of pole pairs to get a useful electrical frequency. I have seen photos of small angle segments of large generators for hydraulic turbines that implied more than thirty poles (my father gave me his copy of the Westinghouse Handbook of Generation and Distribution, and most of its information is still valid[my copy is dated 1950]). There were two reasons steam turbines blew away reciprocating steam engines: Turbines and their generators were smaller Turbines shook less and their vibrations did not carry as far > >Actually, this is one reason the steam turbine was invented. People > >were having to GEAR UP the output of reciprocating steam engines driving [quoted text clipped - 23 lines] > Turbines and their generators were smaller > Turbines shook less and their vibrations did not carry as far Here's a picture of an old ASEA (1910) alternator: http://www.elmuseum.se/kraftverk/images/bullerforsen18.jpg apparently rotating at 150 rpms as can be seen from this: http://www.elmuseum.se/kraftverk/images/bullerforsen22.jpg notice the not so kosher logo ASEA (now ABB) used in 1910 ;-) I've been on a tour through this old power station about 30 years ago, and power stations from that time was a piece of art! Check out more pictures: http://www.elmuseum.se/?/kraftverk/bullerforsen.htm >>Actually, this is one reason the steam turbine was invented. People >>were having to GEAR UP the output of reciprocating steam engines driving [quoted text clipped - 23 lines] > Turbines and their generators were smaller > Turbines shook less and their vibrations did not carry as far I was specifically talking about AC generators. By the time the steam turbine was perfected, AC systems were the system of choice for big power systems, and they were trying to raise frequencies for various reasons. True, for DC systems rpm wasn't a problem, but Edison had lost the power wars, and AC was starting to dominate. >>>Actually, this is one reason the steam turbine was invented. People >>>were having to GEAR UP the output of reciprocating steam engines driving [quoted text clipped - 29 lines] >reasons. True, for DC systems rpm wasn't a problem, but Edison had lost >the power wars, and AC was starting to dominate. But AC systems never needed to be geared up, either. A two pole, 60 Hz AC generator turns at 3600 rpm. A forty pole, 60 Hz AC generator turns at 180 rpm. The initial frequency standard of 25 Hz AC would have rotor speeds of 1500 and 75 Hz, respectively. Low frequency systems have lower losses, but high frequency systems are smaller. The qualities of polyphase systems also embody a compromise. More phases transmit power more efficiently, but adding another phase adds another conductor to each transmission line. Two phase is better than single phase, three phase is better than two phase, but the additional costs of four phase power is not worth the additional cost. >>Actually, this is one reason the steam turbine was invented. People >>were having to GEAR UP the output of reciprocating steam engines driving >>commercial generators. Steam turbines turned faster, allowing higher >>frequency AC without gearing up. Electricity generation was not the only use of early steam engines. Turbines were used on board ships even though the higher speed meant they had to *install* gearing for the slow speed propellers. The turbine is much simpler to maintain, more robust wrt water induction, and packs more hp in a given space/weight. Regardless of the end shaft speed requirements, turbines were adopted for their cost and efficiency. daestrom >>>Actually, this is one reason the steam turbine was invented. People >>>were having to GEAR UP the output of reciprocating steam engines driving [quoted text clipped - 10 lines] > > daestrom I was referring to the use in AC power stations. Indeed the turbine was used in warships before power stations, and while the need for gearing was a slight drawback for ships, it was not for powerplants. However, one thing about the gearing in ships- one needed at least a gear system for reverse anyway. Turbines could not be reversed in rotation while recips could. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.