Tell me about the feasibility of such a construct:

A variable geometry turbo with an alternator/motor attached directly to the turboshaft via a reduction gear. At idle and part throttle (yeah, yeah, diesels have no throttles...you know what I mean ) The motor runs and provides full boost prior to spooling up naturally. At near and full throttle, the motor switches over to alternator mode, recovering kinetic energy from the pressurized exhaust, thus taking the load off of the belt driven alternator.

Any Problems?

Don't use dead dinos for fuel:
let 'em rest in peace!

You don't need full boost at idle. At high rpms you would be trying to drive a high load device (alt) through a gear reduction as well as trying to compress air. The alt would put too much load on the turbine shaft and you would lose boost. Other than that, I don't see any problems. . cheers, Joe

A number of years ago I remember reading an article about GM using a turbo-charger to run the alternator, AC compressor and the power steering pump. Don't think the turbo was used for boost but they claimed that it saved 15 to 20HP. This was during the fuel crunch of the late 70s so I would think it was purely for economy. Haven't heard anything about it since but it may have some merit.

Bill

I now have a Mazda 2.0 litre "Supercharged" engine in the Fatmobile. The "Supercharger" is a belt driven turbocharger, where at low RPM, the belt drive gives some boost. At open throttle and above 1500RPM, the exhaust powers the turbo, with the belt drive preventing excessive revs of the turbo. A "start" valve is included in the intercooler piping, but I believe also acts as a boost "Dump" valve where the boost from the turbo is limited. The extra power removed from the turbo by the belt drive is applied to the alternator and other belt driven auxiliaries.

>26 000 KM in a '90 Mazda 2 litre diesel on SVO with biodiesel start/purge.

Tony

How did you learn all that about your turbo?

Is that Mazda a turbo diesel or a comprex supercharged diesel? They didn't sell Mazda diesels in the UK.

Phill

Pressure wave supercharger

"A pressure-wave supercharger is a charger for the engine which compresses the combustion air. Supercharging increases the power output with the same engine dimensions and engine speeds whilst reducing fuel consumption as the engine is able to work in more favourable ranges. In the past, the pressure-wave supercharger was developed to its present state in particular by the Swiss company COMPREX. In the case of the WENKO drive a pressure-wave supercharger charges the engine up to 2.6 bar in absolute terms.
The principle of supercharging (simplified):

With pressure-wave supercharging pulsating hot exhaust gases and fresh air are combined in the supercharger. The exhaust gas pressure waves compress the fresh air and force it into the combustion chambers. These processes are controlled by the central component of the pressure-wave supercharger, the cylindrical cell rotor. The speed of the latter is synchronised with the engine speed via a V-belt.

The cells in the cell rotor alternately open and close the exhaust gas and fresh air apertures, each located on one side of the housing. When the aperture on the exhaust gas side is reached as a result of the rotary movement, pressurised exhaust gas flows into the cell and compresses the fresh air there. Meanwhile the cell rotor continues turning and the cell described reaches the aperture on the fresh-air inlet side (to the engine). The fresh air, now highly compressed, flows into the engine's inlet tract. Before the exhaust gas can now flow in as well, the aperture is closed again as a result of the cell rotor turning and the exhaust gas column is reflected ("runs up against a wall"). It flows back to the exhaust gas side of the housing and leaves the cell through the aperture (to the outside), which has now become free again as a result of the rotary motion. The exhaust gas column leaves the cell on the exhaust gas side at very high speed, thereby creating negative pressure "behind it". This means that fresh air can be sucked into the cell via an aperture now becoming free on the fresh air side. From this point onwards the process is repeated cyclically.


The exchange of energy in the pressure-wave supercharger occurs at sound velocity, which results in a practically instant response even at low engine speeds.

Although there are various different processes for compressing intake air (turbocharger, mechanical "G supercharger", pressure-wave supercharger, i.a.), the pressure-wave supercharger is the preferred system because it combines the advantages of mechanical and exhaust gas turbocharging. In contrast to the turbocharger, the pressure-wave supercharger effectively increases the engine torque even in the engine's lower speed range. It does not have the infamous "turbo hole". In any case, the turbo is currently mainly installed on large-capacity engines. Although it increases their power output into even more ridiculous speed ranges, it does not improve efficiency in the "lower", range needed in practice - on the contrary, in order to avoid knocking in the turbocharged range the compression ratio is reduced, which worsens the efficiency over the entire operating range."

Information thanks to Greenpeace

The Mechanic I talked to said the 626 diesel had a "Wave Supercharger" Until I looked it up I thought it was a brand name.

Tilly SBC*IBA Mover and Shaker (Pending)

Why is it called "after dark" when it really is "after light"?

Neutral,
I looked at it and it seemed to agree with what I've been told about them, but I believe that I have been misled by the wrecker who I get my parts from.

Tilly, you and your Google.
This is indeed a "Pressure Wave Supercharger" The information I was given is wrong. He did say that the unit would spin even faster if the drive belt was removed. Id this consistent with your description?
What I do not understand is that if this is synchronous with the engine, why would it be geared up so high? It runs from the back of the Alternator, which runs at about 3-4* engine revs. The drive there is about a 125mm diam pulley, driving a 25mm pulley. so that would put it at about 15 - 25 times engine RPM.

Or is it independent of the firing cycle and exhaust gas pulses?

I agree that it does allow exhaust gases to pass, from exhaust to inlet side, when the motor is stationary.

I am keeping your post to study off-line.

>26 000 KM in a '90 Mazda 2 litre diesel on SVO with biodiesel start/purge.

There is a Haynes tech-book on turbocharging / supercharging that has a good description and diagrams of the Comprex supercharger.

Phill

On another message board I asked about the Comprex supercharger.

I was told that the "compie" was a rather limited piece of technology, only producing usable boost at a narrow rpm range and throttle, for which the unit is specifically "tuned" .

Is this true, or can the compie actualy run reliably over the engine's entire operating range?

Don't use dead dinos for fuel:
let 'em rest in peace!

If I give a small throttle blip before putting load onto the engine, the unit appears to provide adequate boost from just above idle, through to what I think is time to change gears. Sorry, no Tacho on the Fatmobile.
If I just put the engine in gear and slowly raise the RPM, it seems to wait until the engine is well above idle, although that could be my subjective interpretation, before coming in with significant boost.
By comparison with my previous (non-superchgd) motor, this (superchgd) motor allows me to climb hills in third gear at half throttle and room to accelerate or climb the same hill in 4th gear, whereas the old motor in third gear would be slowing down and 4th gear would not be considered at all.
Shortly after fitting this motor, I had an intercooler pipe come off and the engine was like a dead slug. It came off on the hill (see above) and I had to climb the hill in 2nd gear, clouds of unburnt fuel from the exhaust too.
>26 000 KM in a '90 Mazda 2 litre diesel on SVO with biodiesel start/purge.

From what I have been reading on this post, you guys seem to be talking about the re-emergence of the "turbo compound engine". When the first radial engines were created for the aircraft industry, one of the big problems to be overcome was the even distribution of the air/fuel mixture and the natural tendance for the lower cylinders to get a richer mixture.

It was so bad that one company actually went as far as rotating the engine around the crankshaft (Nome rotatry). This produced a very smooth engine but because of the slip ring seals used for all air and liquid transfer, very few Nome equipped aircraft ever ran out of fuel...the windscreen and flying goggles were so gummed up with Castor oil you had to land early because you couln't see.

For the most part the solution was to install a diffuser, just downstream of the carburator, powered by the crankshaft. It was discovered that by changing the geometry of the diffuser vane you could actually increase air pressure...the first superchargers. While this worked for moderate amounts of boost, it was none the less, limited as you were only using a single stage compressor. Attempts to gear up this diffuser was met with limited results.

Developments in turbine technology during WW2 lead to the creation of exhaust actuated air turbines (turbo charger). By combining both they were able to create boost at almost the full RPM range of the engine and thus was created the Turbo-compound engine. The developement of the stand alone turbine negated the requirements of ever more powerful piston engines and the technology died...until it seems now.

I have always thought that if you were to combine a low output belt driven supercharger with an effective blow-off valve to work at low RPMs with an exhaust driven, wastegated turbo-charger to take over when load increased you could create an engine that would operate continually in a boost condition allowing for a substantial increase in efficiency, power to wieght ratio and performance.

Never got around to trying out my hypothesis but it would seem that I was on the right track.

Bill

"money can't buy everthing...the rest you can put on your Mastercard"

Eureka!

http://www.turbodyne.com/product2.html

Masochist to Sadist: "Hurt me."
Sadist to Masochist: "No."

They don't actually seem to be selling any product:http://biz.yahoo.com/e/030415/trbd.ob10ksb.html. But from a google search they seem to have been around since the mid 90s.

This from 1998:http://www.fool.com/EveningNews/1998/EveningNews980804.htm
Shares of Turbodyne Technologies (Nasdaq: TRBD), which manufactures permanent mold and sand aluminum castings, were cut more than a third today, losing $5 13/16 to $10, because Asensio & Co. issued a press release entitled "Turbodyne Possesses No Valuable Technology." To back up its argument, Asensio offered that "[n]o manufacturer has ever incorporated a single Turbodyne product in a new engine or vehicle." Turbodyne has made it abundantly clear in all of its SEC filings that the future of the company hinges on its technology -- particularly its two primary, "proprietary" products, the "Turbopac" and the "Dynacharger" for optimizing air flow to internal combustion engines. However, a little investigation by investors may be warranted to ascertain the true potential of the technologies in question.


Don't sequential turbocharging and developments in conventional supercharging address the turbo lag problem? I do understand that burning the same amount of air/fuel of a large engine in a smaller engine can give you the driveability of the large engine but with large efficiency gains. Is the extra complexity of the dynacharger really going to take off when its theoretical superiority is being eroded by cheaper super/turbo charging?

Phill