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FEV Displays Turbocharged, Direct-Injection, E85 Variable Compression Ratio Engine

16 April 2007

Fevvcr
An earlier rendering of the VCR mechanism. Click to enlarge.

FEV Engine Technology is displaying a developmental gasoline/E85 turbocharged direct injection (GTDI) engine that also features variable compression ratio (VCR) at the 2007 SAE World Congress.

The engine is being developed in-house, in tandem with several other DI engine projects that FEV is working on with various automakers, based on earlier work FEV had done with the VCR platform. While offering the potential to generate V-8 power from a V-6 engine, this concept also provides roughly a 20-25% improvement in fuel consumption.

The VCR system is based upon the concept of an eccentric crankshaft bearing. Rotation of the eccentric bearing leads to a vertical position change of the crank train relative to the cylinder head and thus, a continuous change in the compression ratio. An electric motor  controls the adjustment between compression ratios of 8 and 16. FEV has deployed a VCR engine in a demonstration vehicle, and is further optimizing the adjustment mechanism. There is interest in the OEM community in the work, according to Dr.-Ing. Joachim Wolschendorf, Vice President Engineering and Chief Technical Officer.

The VCR element allows the engine to take advantage of the higher octane of ethanol by increasing the compression ratio for higher-level ethanol blends. FEV is currently working to optimize a control strategy for engine management that will take into account the compression ratio as well as load and the fuel mixture.

Although the three principal elements of the engine—VCR, GTDI and Turbocharging—have been tested on the bench and on the road, FEV has not yet put all three together in a vehicle.

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April 16, 2007 in Engines, Ethanol, Vehicle Manufacturers | Permalink | Comments (18) | TrackBack (0)

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Comments

The problem with raising and lowering the centreline of the crankshaft for VCR engines is that you inevitably bugger up the squish band clearances which lowers the performance of your combustion chamber design.

Having said that, if your engine was optimised for E85 then it would be useful to lower the compression ratio for normal gasoline so you could use it when you can't get E85.

Sadly the increased cost would probably mean the engine has no chance of seeing the light of day.

Andy

This thing is blown, so what is the advantage of using VCR over a variable vane turbocharger?

Nothing here is ready for prime time. Show me a real world version; you can't; so it's only more vapor. Spend the money on EVs. That's where we're all headed anyway, plug in battery driven electric autos. Why waste money on building mechanical trickery and quackery?

Andy -

afaik, the main purpose of squish bands is to generate additional turbulence just prior to ignition, to ensure the mixture burns as quickly as possible. There are, however, many different design concepts for the piston crown-cylinder head interface in gasoline engines, many of which feature virtually no special squish bands at all. This is especially true if direct-injection concepts such as this one.

cidi -

in stoichiometrically operated gasoline engines, a turbocharger cannot deliver significant boost at low load and RPM because of the low the exhaust gas mass flow and enthalpy. Raising the geometric compression ratio in this area of the engine map compensates to some extent and also increases thermodynamic efficiency.

Conversely, lowering the geometric compression ratio at high load and RPM means you can keep the turbo's waste gate closed in a larger portion of the engine map and, reduce the amount of shaft work lost to the compression strokes. Theoretical thermodynamic efficiency is reduced, but as long as you don't overdo it the reductions in overall losses can overcompensate for this. Moreover, because the boosted fresh charge is intercooled, combustion temperatures at full load are lower so you no longer need to enrich the mixture just to avoid thermal damage at rated power.

In other words, turbocharging and variable compression plus GDI all complement one another over the whole engine map. The main reason VCR hasn't caught on is the additional complexity of the cranktrain, but FEV obviously still has high hopes for it.

Lad -

FEV is actually one of the leading engine design consultancies in the world, with a close relationship to the RWTH Aachen. They compete against AVL, Ricardo, Lotus and others.

As the above article states, they have already implemented prototypes and validated them separately. The current project covers systems integration of already proven technology. This is hard but it is neither trickery or quackery.

EVs and PHEVs are coming but it will take 1-2 decades for them to gain a large share of the market. There are still fundamental issues of power, safety, longevity and cost to resolve. In the meantime, what choice so we have but to keep improving ICEs?

Rafael Said:

Well said, Said. You are right; however, any push to bypass the complication of controlling the various components with mechanical devices using analog to digital interfaces and microcomputers as an interim solution, will help move us faster toward the goal of moving away from carbon fuel combustion. Improving the ICE only serves to slow down progress toward the future.

Building turbos with inter coolers, directly electo-controlled valves, variable compression ratio cranks etc. are all expensive experiments; but, of little practical value in the long run. I would like to see them put the R and D money into solving the problems associated with bring electric cars to market.

I read about bio fuels as an answer; but, I wonder what effect those also will have on the environment. I think we can assume nothing in this area. Only testing will prove their worth. I hearken back to the first attempt to add ethanol to gasoline that was countered by Big Oil using MTBE, what an environmental mess. The facts show that the best way to clean up the air is at a central power source not in millions of remotely located automobiles and this is the argument for Plug-ins.

The faster we can move personal autos to EVs, the faster we improve the environment.

Why not use variable valve timing to vary compression and expansion ratios? It delivers most of the benefit and is a lot simpler. Do they want to avoid paying royalties?

Lad:

It's frustrating to see energy and engineering talent poured into something that's perceived as, and may very well be a dying technology. But technology, R&D and life are all about pursuing parallel paths.

It's currently impossible to see and anticipate all the pitfalls and time delays a particular path may hold. What if battery tech takes 30 years to be a viable solution? Parallel paths tend to make for a more robust end result and keep options open for the present and future. If we have to use ICE for another 30 years, it would be beneficial to have the most efficient designs at work.

Look at medicine. Lots of people are currently developing cancer treatments from all different angles and using different approaches with no clear winner in many cases. Utility can sometimes be borrowed from one path and added to another, developments and insights that show up on one path may hold a piece of information that enables another path to take the lead.

Until we know all the answers and can down load them directly to everyone's collective conscience, pursuing parallel paths, in many cases, actually makes things move faster. Plus, who doesn't like eccentric bearing mechanisms, turbos, electromagnetic devices and complex control systems? Parties wouldn't be much fun without them! Or maybe I need to go to more interesting parties?

Lad - This is not ment to be an insult but you seem to have closed your mind to the possibility that battery EV's may not be the solution going by you saying we're all headed to EV's. Research must procede on many paths. Givin a few breakthroughs H2 fuel cells might end up being a real solution even though there are major hurdles right now.

ICEs will be around a very long time before they are displaced with other tech. Pound for pound liquid fuels have a much higher energy density than any battery tech. Coming up with ways to make the ICE more efficent is going to be an important part of the transpotation future for the coming decades.

Richard -

detuning the valve timing to achieve overexpansion (Miller or Atkinson cycle) is indeed a good idea for naturally aspirated engines - especially stoichiometric spark ignition designs. This is why Toyota uses it in e.g. the Prius.

For turbo engines, overexpansion does not work as well because it robs the turbine of both enthalpy and mass flux. The compressor also suffers because of the negative impact on flow patterns in the intake manifold.

When variable valve timing is used on turbocharged GDI engines (a good idea!), it's main purpose is to improve scavenging and hence, combustion stability at low load.

Tim Russell:
Didn't mean to exclude the other technologies and I agree the interim ICE solution will be around a long time; however, I tried to make a point that to recover the potential n-r-g in carbon fuels to percentages much higher than 30 to 40 will take a lot of money and effort and will most likely result in lots of electro mechanical complication which often results in poor reliability at a higher cost. I'm suggesting the research path to follow is toward plug-ins.

Like many who read Green Congress, I am intrigued by the various creative solutions to auto mechanical problems and at times I'm amazed at what comes out of engineering minds.

Lad, OK sounds like your heads screwed on right. Often times I've run into zelots that latch on to one thing and think it's the answer. There may be one tech that leads in the end but that is yet to be seen. PHEV tech seems to be a promising way to reduce usage. I really hope GM can turn the powertrain of the Volt into reality. The problem is the battery tech needed to do it might be difficult to do.

GM could easily produce the Volt as a standard series hybrid, with a 5 kwh battery pack, which would be quite sufficient for this vehicle, and could be made in NiMH like the Prius, just 4 times the size of the Prius' battery pack. The battery pack would be very lightly used since only about 1 kwh is needed to absorb and supply the normal acceleration & hill climbing energy, the other 4 kwh would be needed occasionally for hill climbing in the mountains and passing at high speed. Even in NiMH the battery would last in the range of 1 million km's like the Prius' has and would cost about $1100. When the Li-Ion batteries are ready for full scale production, the plug-in series HEV version of the Volt would be a trivial upgrade. GM touts their so-called E-Flex architecture but doesn’t use it. What’s up with that?

It is certainly desirable not to put all energy eggs in one basket, but it is also desirable to invest wisely in Energy Technology likely to be successful. Nutty Hydrogen Economy schemes and Corn Ethanol do not meet the good investment criteria.

There are lot's of promising technologies to put money into, that are not getting sufficient or any funding, like high efficiency generators for series hybrid vehicles, methanol production & distribution, biomass to ethanol via Fischer Tropsch, Thorium molten salt nuclear reactors, the Bussard Inertial Electrostatic Confinement Fusion reactor, and automotive batteries.

For achieving low emissions and high fuel efficiency, a reciprocating engine requires low temperature combustion without EGR, high thermal efficiency without high combustion temperature, and high power density for high mechanical efficiency. During the past few decades, research efforts worldwide to reach these requirements have failed because of the limitations of four-stroke engines.

For removing the limitations of four-stroke engines, an Overexpanded Two-Stroke Constant Pressure cycle (an OTCP Cycle) has been developed. For achieving low temperature combustion, the OTCP cycle chooses a constant pressure combustion process, because of a higher specific heat and the fact that the earlier burned fuel/air mixture is not compressed into a higher temperature after burning. For achieving high thermal efficiency, the OTCP cycle chooses an expansion process having a much longer expansion stroke than the compression stroke. For achieving high power density, the OTCP cycle utilizes the difference of stroke lengths between expansion and compression strokes for replacing cylinder exhaust gas with fresh charge such that a two-stroke Miller cycle can be obtained.

A combustion process of OTCP cycle converts fuel chemical energy into heat energy denoted by Q+. An overexpanded expansion process converts a large portion of heat energy into mechanical work. The remaining portion of heat energy, denoted by Q-, is rejected from the cylinder at the end of the power stroke. The thermal efficiency is equal to (Q+ - Q-)/Q+. That means the thermodynamic aspect of engine design involves only the power stroke. This new insight of a reciprocating engine clearly shows the right way to achieve low emissions and high fuel efficiency. Because Q+ is fixed by the power output, the only way to increase the thermal efficiency is to reduce Q-.

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