MGU-H. What? How?

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RoyO
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MGU-H. What? How?

Post by RoyO »

Racecar engineering has the following description of this system:
"The MGU-H is connected to the turbocharger. Acting as a generator, it absorbs power from the turbine shaft to convert heat energy from the exhaust gases. The electrical energy can be either directed to the MGU-K or to the battery for storage for later use. The MGU-H is also used to control the speed of the turbocharger to match the air requirement of the engine (eg. to slow it down in place of a wastegate or to accelerate it to compensate for turbo lag.)
So it is both energy recovery and anti lag in one!
The MGU-H produces AC current, but the battery and MGU-K is DC current so a highly complex convertor is needed.
Very high rotational speeds are a challenge as the MGU-H is coupled to a turbocharger spinning at speeds of up to 100,000rpm. Bearing design and again cooling are critical."


Now call me dense but I still don't understand how this system works, even in simple terms. The section I've highlighted in bold reads as gibberish to me. Nothing I've seen anywhere explains how heat is converted to electrical current in this system. In the above is implied that the kinetic energy in the turbocharger rotation is the source, not heat.

Can someone point me to a link where this technology is more clearly described.
Roy

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moby
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Re: MGU-H. What? How?

Post by moby »

Yip, I also can not fathom the "heat" bit as it is obviously moving gas. There is no energy recovered from heat as far as i can see.

Lord Crc
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Re: MGU-H. What? How?

Post by Lord Crc »

moby wrote:Yip, I also can not fathom the "heat" bit as it is obviously moving gas. There is no energy recovered from heat as far as i can see.
As I understand it, it's not using the heat directly. Rather it's exploiting the fact that when the combustion occurs in the engine, the exhaust gas has expanded compared to the intake gas due to the heat.

Thus the exhaust gas can rotate the turbo more compared to what the intake gas could, had the intake gas not been ignited and simply pushed out by the piston.

By hooking up a dynamo to the turbo shaft, they can extract electrical energy from the exhaust gasses leaving the engine.

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moby
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Re: MGU-H. What? How?

Post by moby »

Lord Crc wrote:
moby wrote:Yip, I also can not fathom the "heat" bit as it is obviously moving gas. There is no energy recovered from heat as far as i can see.
As I understand it, it's not using the heat directly. Rather it's exploiting the fact that when the combustion occurs in the engine, the exhaust gas has expanded compared to the intake gas due to the heat.

Thus the exhaust gas can rotate the turbo more compared to what the intake gas could, had the intake gas not been ignited and simply pushed out by the piston.

By hooking up a dynamo to the turbo shaft, they can extract electrical energy from the exhaust gasses leaving the engine.
But it is still basically a windmill, and gas with lots of calories in goes out the pipe wasted.

It just sounds good in the blurb

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Alienturnedhuman
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Re: MGU-H. What? How?

Post by Alienturnedhuman »

The heat from the chemical reaction causes the pressure to increase in the cylinder, this pressure causes the gases to move, and once the valves open out into the exhaust. This then drives the turbo which turns the MGUH.

So yes, at the point at which it is converted into electrical power it is kinetic energy, however it started from the thermal energy of the reaction.

If they were turning heat directly into useful energy they would be in danger of breaking the second law of thermodynamics. And that's at least a two race ban.

Lord Crc
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Re: MGU-H. What? How?

Post by Lord Crc »

Alienturnedhuman wrote:If they were turning heat directly into useful energy they would be in danger of breaking the second law of thermodynamics. And that's at least a two race ban.
Heh. Technically they could do this using a Peltier element (which works through the Seebeck effect). However they're not very efficient (requiring a significant temperature delta), so not very useful for a F1 car.

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moby
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Re: MGU-H. What? How?

Post by moby »

Alienturnedhuman wrote:The heat from the chemical reaction causes the pressure to increase in the cylinder, this pressure causes the gases to move, and once the valves open out into the exhaust. This then drives the turbo which turns the MGUH.

So yes, at the point at which it is converted into electrical power it is kinetic energy, however it started from the thermal energy of the reaction.

If they were turning heat directly into useful energy they would be in danger of breaking the second law of thermodynamics. And that's at least a two race ban.
And one is the human race :D

Agree, but this would all happen anyway and plow out the pipe. It is the already expanded gas that is used the temp at the vane is irrelevant.

But the only way I can see of using it is thermocouples or some sort of sterling engine. I have asked the question of how is the heat used from day one without a satisfactory reply.

Lord Crc
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Re: MGU-H. What? How?

Post by Lord Crc »

moby wrote:I have asked the question of how is the heat used from day one without a satisfactory reply.
There isn't a really good answer, except they had to call it something.

The MGU-K (KERS) also technically recovers the heat energy, a it's the heat (causing the air to expand during combustion) that made the car move to begin with.

So perhaps a better name would have been MGU-X (for eXhaust) or something, but it's not a huge issue.

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Alienturnedhuman
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Re: MGU-H. What? How?

Post by Alienturnedhuman »

I think MGU-P would be the best description, as it's harvesting the energy from the pressure of the exhaust gases. That would then fit with the MGU-K still being called the MGU-K as it's the form the energy was in right before driving the harvesting motor.

As the MGU-H doesn't cool the gases down I don't think we can claim it is harvesting heat energy.

Lord Crc
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Re: MGU-H. What? How?

Post by Lord Crc »

Alienturnedhuman wrote:I think MGU-P would be the best description, as it's harvesting the energy from the pressure of the exhaust gases. That would then fit with the MGU-K still being called the MGU-K as it's the form the energy was in right before driving the harvesting motor.
Good suggestion, you'd get my vote ;)

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moby
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Re: MGU-H. What? How?

Post by moby »

Alienturnedhuman wrote:I think MGU-P would be the best description, as it's harvesting the energy from the pressure of the exhaust gases. That would then fit with the MGU-K still being called the MGU-K as it's the form the energy was in right before driving the harvesting motor.

As the MGU-H doesn't cool the gases down I don't think we can claim it is harvesting heat energy.
Of course, they could call it MGU_S and claim that is where the missing sound has gone, recycled into the turbo :D

Saabjock
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Re: MGU-H. What? How?

Post by Saabjock »

The MGU principal is very similar to that of the Auxiliary Power Units (APU) starters I worked on for years in business jet aviation...sans the gearbox.
Most are dual purpose and act as both starter and generator for weight savings.
In the case of the APU, the S/G reverts to a generator through a GCU (Generator Control Unit) after start.
In the cars the turbine/compressor shaft is coupled to the Motor-Generator Unit (MGU).
The exhaust gas rotates the turbine wheel/shaft assembly which serves as the input/output to the MGU depending on mode.
This rotation of the MGU (generator mode) creates electrical energy which is stored in a power-pack or 'harvested' for future use.
That energy stored by the power-pack then drives the MGU (motor mode) when accelerating out of corners.
This action reduces lag by spooling the turbo faster.

Irbis
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Re: MGU-H. What? How?

Post by Irbis »

Alienturnedhuman wrote:If they were turning heat directly into useful energy they would be in danger of breaking the second law of thermodynamics. And that's at least a two race ban.
Care to point out how it would apply seeing F1 car is not an example of isolated system?

Also, every single mechanical fuel engine 'turns heat directly into useful energy', the limitation in SLoT is on flow of the heat, not what you do to it.

Saabjock
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Re: MGU-H. What? How?

Post by Saabjock »

Reading too much into this...
They're not taking the exhaust gas piping it somewhere and turning it into something 'magical'.
All they're doing is using the energy extracted as the turbo spools to drive an extended shaft into the MGU to charge the batteries....then reversing that by using the battery to spool the MGU.

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moby
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Re: MGU-H. What? How?

Post by moby »

Saabjock wrote:The MGU principal is very similar to that of the Auxiliary Power Units (APU) starters I worked on for years in business jet aviation...sans the gearbox.
Most are dual purpose and act as both starter and generator for weight savings.
In the case of the APU, the S/G reverts to a generator through a GCU (Generator Control Unit) after start.
In the cars the turbine/compressor shaft is coupled to the Motor-Generator Unit (MGU).
The exhaust gas rotates the turbine wheel/shaft assembly which serves as the input/output to the MGU depending on mode.
This rotation of the MGU (generator mode) creates electrical energy which is stored in a power-pack or 'harvested' for future use.
That energy stored by the power-pack then drives the MGU (motor mode) when accelerating out of corners.
This action reduces lag by spooling the turbo faster.
Motorcycles of half century ago used a CIBA DYNASTART which was the same except driven by/drives the crank instead of a spindle. This is unambiguous though and does not pretend to use heat, just rotational forces and magnets.

Battery supplies power to spin the motor to start, ans once started it becomes a dynamo and produces power.

Blinky McSquinty

Re: MGU-H. What? How?

Post by Blinky McSquinty »

The heat from combustion produces an expanding medium, the exhaust gases. The exhaust gases, because they are hot and thus expanding, force themselves out the exhaust pipe once the exhaust valves open. That hot exhaust flow (kinetic energy) pushes against the impellers of the turbine, converting that hot gas energy into mechanical energy, the turning of the turbocharger shaft. That torque on the turbocharger shaft is transferred to the turbocharger compressor, or to the MGU-H. Going one step further, the MGU-H converts that torque into electrical energy.

If you really want to dig deeper, electrical energy going to the battery produces a chemical reaction. In the case of a lithium battery, when the battery charges, ions of lithium move through the electrolyte from the positive electrode to the negative electrode and attach to the carbon. During discharge, the lithium ions move back to the LiCoO2 from the carbon.

Energy can be converted. It starts with potential chemical energy in the gasoline, converted to heat energy>kinetic>mechanical>electrical>chemical.

But that is not the only way to convert heat energy into mechanical energy. One auto manufacturer is considering placing a small boiler to the exhaust system, it heats up, steam is produced, a small turbine converts that into electricity.

Or a Sterling engine.

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moby
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Re: MGU-H. What? How?

Post by moby »

Blinky McSquinty wrote:The heat from combustion produces an expanding medium, the exhaust gases. The exhaust gases, because they are hot and thus expanding, force themselves out the exhaust pipe once the exhaust valves open. That hot exhaust flow (kinetic energy) pushes against the impellers of the turbine, converting that hot gas energy into mechanical energy, the turning of the turbocharger shaft. That torque on the turbocharger shaft is transferred to the turbocharger compressor, or to the MGU-H. Going one step further, the MGU-H converts that torque into electrical energy.

If you really want to dig deeper, electrical energy going to the battery produces a chemical reaction. In the case of a lithium battery, when the battery charges, ions of lithium move through the electrolyte from the positive electrode to the negative electrode and attach to the carbon. During discharge, the lithium ions move back to the LiCoO2 from the carbon.

Energy can be converted. It starts with potential chemical energy in the gasoline, converted to heat energy>kinetic>mechanical>electrical>chemical.

But that is not the only way to convert heat energy into mechanical energy. One auto manufacturer is considering placing a small boiler to the exhaust system, it heats up, steam is produced, a small turbine converts that into electricity.

Or a Sterling engine.
When I was young, we used to wire foil wrapped meat onto the exhaust manifold of my Volks van when we went to the beach. They would be ready just about when we arrived. That is recovering heat energy :D

motie
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Re: MGU-H. What? How?

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Guia
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Re: MGU-H. What? How?

Post by Guia »

Alienturnedhuman wrote:The heat from the chemical reaction causes the pressure to increase in the cylinder, this pressure causes the gases to move, and once the valves open out into the exhaust. This then drives the turbo which turns the MGUH.

So yes, at the point at which it is converted into electrical power it is kinetic energy, however it started from the thermal energy of the reaction.

If they were turning heat directly into useful energy they would be in danger of breaking the second law of thermodynamics. And that's at least a two race ban.
LOL.

And a nice explanation, ATH.

GarJE
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Re: MGU-H. What? How?

Post by GarJE »

I think I know where Merc's performance gain is.

The mgu-h is used conventionally to overcome lag by pre-compressing the inlet tract.

A second benefit could be that in a decoupled turbo, the exhaust turbine could be "spun-up" independently, creating a draw in the exhaust track, effectively pullung down a vacuum.

Exhaust gases would therefore be "sucked" from the engine when a valve is open, boosting efficiency.

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Alienturnedhuman
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Re: MGU-H. What? How?

Post by Alienturnedhuman »

The turbines are still connected via a common shaft, as that is a requirement of the regulations. So they can't spin up the compressor while the exhaust turbine is stationary or vice versa. The Mercedes have just made the shaft run the length of the engine to move the turbines away from each other.

Blinky McSquinty

Re: MGU-H. What? How?

Post by Blinky McSquinty »

GarJE wrote:I think I know where Merc's performance gain is.

The mgu-h is used conventionally to overcome lag by pre-compressing the inlet tract.

A second benefit could be that in a decoupled turbo, the exhaust turbine could be "spun-up" independently, creating a draw in the exhaust track, effectively pullung down a vacuum.

Exhaust gases would therefore be "sucked" from the engine when a valve is open, boosting efficiency.
If you ran such an arraignment, the turbine would attempt to compress the exhaust system because it is a centrifugal compressor. It would be terribly inefficient because of the alignment of the vanes, but it definitely would be incapable of extracting anything.

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