... as a range extender coupled to an electric motor. I thinks it's a great idea.
https://jalopnik.com/mazda-officially-announces-the-return-of-the-rotary-eng-1829459947
From a size standpoint, makes a lot of sense. Power output is quite high for the physical envelope of the engine. Fuel efficiency, though...
BSFC of a rotary engine is better than a piston engine at high loads.
It makes sense to use a rotary like this... Just really sad this looks like what will come from over a decade of development time since the Renesis 1.3L
A good idea. I wonder how they will sound. Range extenders need to be quiet as possible. Vibration will be nonexistent but hopefully they can keep the revs low
Quote from: 12,000 RPM on October 02, 2018, 11:34:16 AM
A good idea. I wonder how they will sound. Range extenders need to be quiet as possible. Vibration will be nonexistent but hopefully they can keep the revs low
Why is that important? The engine ought to be able to run at a wide range of RPMs depending on the load.
Nice! Rotary hybrid drivetrain sounds great
Quote from: Laconian on October 02, 2018, 11:39:09 AM
Why is that important? The engine ought to be able to run at a wide range of RPMs depending on the load.
Most range extenders default to a pre-programmed efficient RPM and hang there. The load is decoupled from the car's speed (at least in the way an engine connected through a transmission is). I don't think too many people want a rotary zinging at 9000 RPM to charge the battery or add thrust....
Quote from: Laconian on October 02, 2018, 11:39:09 AM
Why is that important? The engine ought to be able to run at a wide range of RPMs depending on the load.
If its a true series hybrid (and the term range extender kinda implies that), won't matter. Speed of the ICE is decoupled from the vehicle speed anyways. it actually simplifies a lot of things greatly.
Quote from: Soup DeVille on October 02, 2018, 02:24:42 PM
If its a true series hybrid (and the term range extender kinda implies that), won't matter. Speed of the ICE is decoupled from the vehicle speed anyways. it actually simplifies a lot of things greatly.
Yes, but what I'm saying is that low RPM operation probably isn't what's desirable, because then you've the overhead of an off-idle engine without any of the power. Instead, you probably want it to run at max efficiency RPM (cruising and recharging a battery) or max power RPM (accelerating with a depleted battery).
The beauty of the rotary is that you could spin it at higher RPMs without the NVH penalty you would have on a two cylinder. So, no need to have the engine loaf - just turn it off.
Could you just put a little Honda generator in the trunk of your Tesla or Leaf with a cord going to the charge plug? In a soundproof box with proper ventilation, that is.
Quote from: 12,000 RPM on October 02, 2018, 02:23:06 PM
Most range extenders default to a pre-programmed efficient RPM and hang there. The load is decoupled from the car's speed (at least in the way an engine connected through a transmission is). I don't think too many people want a rotary zinging at 9000 RPM to charge the battery or add thrust....
A rotary zinging at 9k rpms is actually smoother then idle
Quote from: giant_mtb on October 02, 2018, 05:05:41 PM
Could you just put a little Honda generator in the trunk of your Tesla or Leaf with a cord going to the charge plug? In a soundproof box with proper ventilation, that is.
A little Honda generator is what, 5 hp? Assuming no transmission losses (which isn't true), you're still using more than 5 hp to move a car. You're going to deplete your battery faster than you charge. But in theory, yes, you can do that. That's essentially what the BMW i3 does with it's gasoline range extender.
Quote from: giant_mtb on October 02, 2018, 05:05:41 PM
Could you just put a little Honda generator in the trunk of your Tesla or Leaf with a cord going to the charge plug? In a soundproof box with proper ventilation, that is.
Yes, and I've actually seen that done.
Quote from: r0tor on October 02, 2018, 05:05:53 PM
A rotary zinging at 9k rpms is actually smoother then idle
Yes, but I would think that the greater volumetric efficiency and less
wear at lower speeds would make a slower engine a better choice.
Quote from: MrH on October 02, 2018, 05:08:42 PM
A little Honda generator is what, 5 hp? Assuming no transmission losses (which isn't true), you're still using more than 5 hp to move a car. You're going to deplete your battery faster than you charge. But in theory, yes, you can do that. That's essentially what the BMW i3 does with it's gasoline range extender.
The most common sizes are 2200 and 4500 watts.
Diesel would be better economy. Like locomotives.
Quote from: Soup DeVille on October 02, 2018, 05:18:29 PM
Yes, but I would think that the greater volumetric efficiency and less
wear at lower speeds would make a slower engine a better choice.
Volumetric efficiency and brake specific fuel consumption are best in a rotary in the upper portion of the power curve as gas leakage past the apex seals is minimized.
Fuel mileage was one of the keys of the 787B winning at LeMans
Quote from: r0tor on October 02, 2018, 05:48:34 PM
Volumetric efficiency and brake specific fuel consumption are best in a rotary in the upper portion of the power curve as gas leakage past the apex seals is minimized.
Fuel mileage was one of the keys of the 787B winning at LeMans
Yes, the upper portion, whatever you design that to be. I would doubt it would be as high as 9000 RPM.
Quote from: r0tor on October 02, 2018, 10:17:32 AM
BSFC of a rotary engine is better than a piston engine at high loads.
It makes sense to use a rotary like this... Just really sad this looks like what will come from over a decade of development time since the Renesis 1.3L
That's true for T/C'ed rotaries. For N/A, it's the opposite.
Quote from: r0tor on October 02, 2018, 05:48:34 PM
Volumetric efficiency and brake specific fuel consumption are best in a rotary in the upper portion of the power curve as gas leakage past the apex seals is minimized.
Fuel mileage was one of the keys of the 787B winning at LeMans
The 787's fuel mileage was largely achieved by driver technique. Mazda figured out the driving techniques that got the best fuel economy results and then they had to have their drivers basically re-learn how to drive (specifically throttle application technique) to maximize efficiency. They also fitted the cars with fuel economy indicators to warn the drivers if they slipped back into old habits.
Quote from: r0tor on October 02, 2018, 05:05:53 PM
A rotary zinging at 9k rpms is actually smoother then idle
Not quieter though.
Quote from: 12,000 RPM on October 02, 2018, 06:33:44 PM
Not quieter though.
Wankels are actually pretty quiet at higher RPMs with a good muffler on them. Also bear in mind that the rotors themselves aren't spinning at 9000 RPM. The eccentric shaft is spinning that fast, but the rotors are running at 1/3 that speed.
Quote from: MrH on October 02, 2018, 05:08:42 PM
A little Honda generator is what, 5 hp? Assuming no transmission losses (which isn't true), you're still using more than 5 hp to move a car. You're going to deplete your battery faster than you charge. But in theory, yes, you can do that. That's essentially what the BMW i3 does with it's gasoline range extender.
Not sure if this has already been done, but I wonder if you could have the gasoline engine drive the wheels through some kind gearbox arrangement. That was you could cut out the generator and electric motor middlemen
Quote from: Morris Minor on October 03, 2018, 09:08:26 PM
Not sure if this has already been done, but I wonder if you could have the gasoline engine drive the wheels through some kind gearbox arrangement. That was you could cut out the generator and electric motor middlemen
:lol:
Quote from: Morris Minor on October 03, 2018, 09:08:26 PM
Not sure if this has already been done, but I wonder if you could have the gasoline engine drive the wheels through some kind gearbox arrangement. That was you could cut out the generator and electric motor middlemen
:golfclap:
I've wondered for some time now if it was practical to mount 2 - 4 alternators on the roof of an electric car, covered with an aerodynamic shroud. The alternators have turbine impellers on the shafts (about 6" diameter) and the shroud has NACA style ducts to feed ram air to the impellers. The alternators feed AC current to an ECU/converter, which then charges the batteries while you drive.
I assume this has been long thought of, but for some reason not feasible?
Quote from: Morris Minor on October 03, 2018, 09:08:26 PM
Not sure if this has already been done, but I wonder if you could have the gasoline engine drive the wheels through some kind gearbox arrangement. That was you could cut out the generator and electric motor middlemen
:clap: :lol:
"Wankel range extender..."
The last thing that I associate with a Wankel engine is fuel efficiency and range. Also, does this not mean more maintenance costs as Wankel engines require frequent oil fill-ups?
Quote from: Rockraven on October 04, 2018, 06:34:29 AM
I've wondered for some time now if it was practical to mount 2 - 4 alternators on the roof of an electric car, covered with an aerodynamic shroud. The alternators have turbine impellers on the shafts (about 6" diameter) and the shroud has NACA style ducts to feed ram air to the impellers. The alternators feed AC current to an ECU/converter, which then charges the batteries while you drive.
I assume this has been long thought of, but for some reason not feasible?
The energy generated would be less than the power expended to overcome the aerodynamic drag of the turbines.
Quote from: cawimmer430 on October 04, 2018, 07:21:50 AM
"Wankel range extender..."
The last thing that I associate with a Wankel engine is fuel efficiency and range. Also, does this not mean more maintenance costs as Wankel engines require frequent oil fill-ups?
As noted, under high load and at a constant speed, they're quite efficient.
http://m.youtube.com/watch?v=2gm29WZpBJc
Quote from: MX793 on October 04, 2018, 02:23:57 PM
The energy generated would be less than the power expended to overcome the aerodynamic drag of the turbines.
Easy answer, but it loses lustre when you take the turbines out of the vehicle's aerodynamic flow. You can have an intake faired with the bodywork the size of a pitot tube... 1 cm across. At speed the ram air can spin the turbine at high rpm and generate power.
Quote from: Rockraven on October 04, 2018, 03:22:49 PM
Easy answer, but it loses lustre when you take the turbines out of the vehicle's aerodynamic flow. You can have an intake faired with the bodywork the size of a pitot tube... 1 cm across. At speed the ram air can spin the turbine at high rpm and generate power.
Yeah, I mean, look at all the fancy aerodynamic ductwork some supercars have for air intake or radiator cooling. Their bodies are still aero as frig.
Quote from: Rockraven on October 04, 2018, 03:22:49 PM
Easy answer, but it loses lustre when you take the turbines out of the vehicle's aerodynamic flow. You can have an intake faired with the bodywork the size of a pitot tube... 1 cm across. At speed the ram air can spin the turbine at high rpm and generate power.
What you're proposing amounts to a perpetual motion machine, which violates the 2nd Law of Thermodynamics.
Laws were made to be broken, man... :rastaman:
Don't be a physics fascist!
We might think of the universe as a perpetual motion machine :huh:.
No way, entropy will destroy everything. We're all racing towards energy equilibrium.
Quote from: MX793 on October 04, 2018, 03:59:20 PM
What you're proposing amounts to a perpetual motion machine, which violates the 2nd Law of Thermodynamics.
No, I'm proposing a range extender. You won't get anywhere close to the power expended to propel the car, but you can trickle charge the batteries as you drive.
Quote from: Rockraven on October 04, 2018, 04:11:17 PM
No, I'm proposing a range extender. You won't get anywhere close to the power expended to propel the car, but you can trickle charge the batteries as you drive.
Yeah, if anything it would help keep the electronics/fans/AC goin' without draining as much from actual propulsion energy.
Similar idea of an electric gyrocopter. Electric motor/propeller drives the craft forward, causing the freewheeling rotor to spin and create lift. You can harness that huge windmill by gearing it to a generator to send charging power back to the batteries.
Quote from: giant_mtb on October 04, 2018, 04:13:07 PM
Yeah, if anything it would help keep the electronics/fans/AC goin' without draining as much from actual propulsion energy.
Yes, that too. Airliners have emergency ram air generators that deploy into the airstream to power all the flight systems if there's a catastrophic loss of power.
Quote from: Rockraven on October 04, 2018, 04:11:17 PM
No, I'm proposing a range extender. You won't get anywhere close to the power expended to propel the car, but you can trickle charge the batteries as you drive.
Yes,
you are.
TANSTAAFL.
Quote from: Rockraven on October 04, 2018, 04:17:46 PM
Yes, that too. Airliners have emergency ram air generators that deploy into the airstream to power all the flight systems if there's a catastrophic loss of power.
To answer your question: why don't they just leave those on all the time then?
Quote from: Soup DeVille on October 04, 2018, 04:28:56 PM
To answer your question: why don't they just leave those on all the time then?
Because you don't need them when the engines are generating power.
Quote from: Rockraven on October 04, 2018, 04:33:14 PM
Because you don't need them when the engines are generating power.
If it was a net positive process; if it produced more power than it used, why wouldn't they leave them on all the time?
I see I'm up against the "heavier than air flight is impossible" crowd. :lol:
Quote from: Rockraven on October 04, 2018, 04:40:21 PM
No, I'm not.
Yeah, you're misunderstanding a basic fact. You can't get something from nothing. Nothing is more than 100% efficient. Most things never even come close.
You don't create energy, you just change its form; and everytime you do, you lose some to the process. Your plan is taking kinetic energy from the wind and the motion of the car, turning it into electrical energy, just to turn it back to kinetic energy to push the car into that same wind.
Its a net negative process, no matter how you add it up.
Quote from: Rockraven on October 04, 2018, 04:43:57 PM
I see I'm up against the "heavier than air flight is impossible" crowd. :lol:
Well, then you best do ot and prove us wrong.
Quote from: Soup DeVille on October 04, 2018, 04:44:11 PM
Yeah, you're misunderstanding a basic fact. You can't get something from nothing. Nothing is more than 100% efficient. Most things never even come close.
You don't create energy, you just change its form; and everytime you do, you lose some to the process. Your plan is taking kinetic energy from the wind and the motion of the car, turning it into electrical energy, just to turn it back to kinetic energy to push the car into that same wind.
Its a net negative process, no matter how you add it up.
It's not creating energy; it's redirecting energy (airflow) to generate electricity. So what you're saying is that electricity generated would be negated by the extra energy required by the motor to compensate for parasitic loss caused by the intake and turbine/alternator setup?
The problem is that the wind is generated from the car moving itself. If it was natural wind, yes you could power something from it.
Quote from: Rockraven on October 04, 2018, 05:21:10 PM
It's not creating energy; it's redirecting energy (airflow) to generate electricity. So what you're saying is that electricity generated would be negated by the extra energy required by the motor to compensate for parasitic loss caused by the intake and turbine/alternator setup?
It would be negated by the extra energy required to create the airflow. The parasitic loss would be the disturbance of the airflow- yes, even in a NACA duct.
Quote from: Rockraven on October 04, 2018, 05:21:10 PM
It's not creating energy; it's redirecting energy (airflow) to generate electricity. So what you're saying is that electricity generated would be negated by the extra energy required by the motor to compensate for parasitic loss caused by the intake and turbine/alternator setup?
Let me put numbers to it.
You have an electric vehicle with typical car aerodynamics. It requires 25 kW of power to maintain 65 mph on flat ground in still air (power to overcome drag and rolling resistance). You attach to that car one or more little wind turbines that, cumulatively, generate 5 kW of power at 65 mph. The drag they will add to the car in order to create that 5 kW will require the propulsion motor to put out more than 5 kW to overcome in order to maintain speed. Let's say 6 kW of additional drag. So now the car needs 31 kW to maintain 65 mph, but the turbines are kicking back 5 kW, so you're at 26 kW total propulsive power to do 65 mph.
Let's say you have 50 kW-h of battery charge.
The car without the wind-turbine "range extender" can travel for 2 hrs at 65 mph, 130 miles
The car with the wind turbine "range extender" can travel for 1.92 hrs at 65 mph, or 124.8 miles.
The range extender will not extend range.
Even assuming a 100% efficient turbine (power generated equals the drag incurred), which is impossible due to the laws of thermodynamics, you can do no better than match the range of the scenario when you have no turbine. The only way for that to extend range is for the turbine to have a greater than 100% efficiency, which also violates the laws of thermodynamics.
Quote from: Rockraven on October 04, 2018, 04:17:46 PM
Yes, that too. Airliners have emergency ram air generators that deploy into the airstream to power all the flight systems if there's a catastrophic loss of power.
Which requires that they throttle up the engines (and burn more fuel) to overcome the added drag of the emergency generators. That power isn't gotten for free. It's using the plane's kinetic energy to turn those turbines, and since the engines are the things imparting that kinetic energy, either the plane slows down at the same fuel consumption rate, or they throttle up (increase consumption rate) to maintain speed.
Quote from: MX793 on October 04, 2018, 06:01:46 PM
Which requires that they throttle up the engines (and burn more fuel) to overcome the added drag of the emergency generators. That power isn't gotten for free. It's using the plane's kinetic energy to turn those turbines, and since the engines are the things imparting that kinetic energy, either the plane slows down at the same fuel consumption rate, or they throttle up (increase consumption rate) to maintain speed.
I think he's talking about a RAT, which is an emergency device for when the engines stop.
https://en.m.wikipedia.org/wiki/Ram_air_turbine
In this case, they add drag and slow the plane down- but allow you to maintain hydraulic and electric power.
Maybe a louver could open during braking? But then why not just do regen braking instead...
Quote from: Laconian on October 04, 2018, 06:16:06 PM
Maybe a louver could open during braking? But then why not just do regen braking instead...
Regen braking would be (is) far more efficient. Which is why all contemporary hybrids and EVs utilize it.
Of course if you had some sort of wind generator where you could sit by the side of the road and capture energy from the breeze of passing cars...
Well, that's one step away from putting a small windmill on the Thanksgiving table and trying to put some of that hot air to a useful purpose...
Quote from: MX793 on October 04, 2018, 05:56:10 PM
Let me put numbers to it.
You have an electric vehicle with typical car aerodynamics. It requires 25 kW of power to maintain 65 mph on flat ground in still air (power to overcome drag and rolling resistance). You attach to that car one or more little wind turbines that, cumulatively, generate 5 kW of power at 65 mph. The drag they will add to the car in order to create that 5 kW will require the propulsion motor to put out more than 5 kW to overcome in order to maintain speed. Let's say 6 kW of additional drag. So now the car needs 31 kW to maintain 65 mph, but the turbines are kicking back 5 kW, so you're at 26 kW total propulsive power to do 65 mph.
Let's say you have 50 kW-h of battery charge.
The car without the wind-turbine "range extender" can travel for 2 hrs at 65 mph, 130 miles
The car with the wind turbine "range extender" can travel for 1.92 hrs at 65 mph, or 124.8 miles.
The range extender will not extend range.
Even assuming a 100% efficient turbine (power generated equals the drag incurred), which is impossible due to the laws of thermodynamics, you can do no better than match the range of the scenario when you have no turbine. The only way for that to extend range is for the turbine to have a greater than 100% efficiency, which also violates the laws of thermodynamics.
Good explanation, and I did learn this stuff a long time ago, but say the impellers were well designed and allowed the alternators to kick out 10 kw. Given the airflow and aerodynamic drag remains almost the same, you're telling me the drive motor must draw another 10+ kw to compensate. That doesn't seem right. I don't mean to sound dumb... it's actually an interesting discussion.
Quote from: Soup DeVille on October 04, 2018, 06:25:40 PM
Of course if you had some sort of wind generator where you could sit by the side of the road and capture energy from the breeze of passing cars...
Well, that's one step away from putting a small windmill on the Thanksgiving table and trying to put some of that hot air to a useful purpose...
I met the guy up here who formed a company to do just that. Wind impellers/generators mounted into the divided highway medians. I don't think the cost advantages are there.
Quote from: Rockraven on October 04, 2018, 06:34:44 PM
Good explanation, and I did learn this stuff a long time ago, but say the impellers were well designed and allowed the alternators to kick out 10 kw. Given the airflow and aerodynamic drag remains almost the same, you're telling me the drive motor must draw another 10+ kw to compensate. That doesn't seem right. I don't mean to sound dumb... it's actually an interesting discussion.
Yes. If you put a 10kW wind turbine on a car, it will add >10kW of drag to the car. The law of conservation of energy states that the turbine cannot add less than 10kW of drag (1st Law of Thermodynamics). And, as energy conversion cannot be 100% efficient (2nd Law of Thermodynamics), the turbine must therefore incur more drag than the energy it generates.
Putting a wind turbine on the car is no different than attaching a trailing 5th wheel that turns a generator as it rolls along (actually, the 5th wheel generator would probably be more efficient, but still a net loss). Like the turbine, the wheel would convert kinetic energy to create electricity. The car's propulsion motor creates that kinetic energy. To offset the drain of the KE being converted to electricity, the car's motor would have to increase it's output to maintain speed. The amount the output increases would have to be at least as high as the power being generated, assuming 100% efficiency at the generator. Every kW it generates in power is more than a kW of extra drag it imparts on the car for the reasons given above. It would basically be a trailing regenerative brake that's always there, trying to slow the car down and taking power to overcome, while generating less power than it takes to overcome the drag of the wheel.
An even more simplified scenario would be to connect a battery to a motor, then have the motor's output shaft directly driving a generator, and then have the generator feed power back into the battery (with diodes to ensure that the electricity can only flow 1-way). Due to losses in the system (resistance in the wires, friction in bearings, etc), the output of the generator into the battery will always be less than the output from the battery and the motor. This means that the battery will eventually go dead, as it takes more mechanical power to turn the generator than electrical power the generator can create (or, more accurately, convert).
Suppose you want to use this motor to power some kind of equipment, like a conveyor belt. If you attach both a generator and a conveyor belt to the motor, thinking that the generator's output will at least partially charge the battery and increase your run time, you'll find that battery will actually go dead faster than if you just ran the conveyor belt.
Quote from: Soup DeVille on October 04, 2018, 02:37:15 PM
As noted, under high load and at a constant speed, they're quite efficient.
I know the Wankel is part of Mazda's uniqueness and USP to enthusiasts, but I still can't imagine this motor finding acceptance among the majority of the buying public. It might be efficient at constant speed, but aren't Wankel's still notorious for a high oil consumption and Apex seals that need to be replaced sooner or later?
Quote from: cawimmer430 on October 05, 2018, 09:26:10 AM
I know the Wankel is part of Mazda's uniqueness and USP to enthusiasts, but I still can't imagine this motor finding acceptance among the majority of the buying public. It might be efficient at constant speed, but aren't Wankel's still notorious for a high oil consumption and Apex seals that need to be replaced sooner or later?
They're not that bad, and if its a PHEV, it probably won't really be running very much depending on usage.
Quote from: 2o6 on October 05, 2018, 11:50:24 AM
They're not that bad, and if its a PHEV, it probably won't really be running very much depending on usage.
We'll see. Should be interesting. ;)
Audi had planned to use a wankel as a range extender, and had a working prototype in the form of the A1 e-tron concept, but thee overlords at VW pulled the plug on that.