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Ricardo papers on ultra-fuel efficient gasoline engine research receive FISITA awards

3 December 2012

Tsgdi
Cross-sectional view of SGDI cylinder head showing the layout of the combustion system. King et al. Click to enlarge.

Papers on the Ricardo turbocharged spray-guided gasoline direct injection (T-SGDI) combustion system and on its HyBoost research (earlier post) took awards for most “outstanding paper” at the recent FISITA 2012 World Automotive Congress in Beijing in the “future internal combustion engines” and “future powertrain” categories.

T-SGDI. Ricardo, in collaboration with the engines business of Malaysian technology and energy company PETRONAS Research Sdn Bhd., have undertaken a four-year collaborative research program to develop the next generation of spark-ignited Spray Guided Direct Injection (SGDI) gasoline engine combustion system with robustness to blended fuels such as ethanol or methanol.

In the FISITA paper, Jason King from Ricardo mainly covered the development and benefits of stratified operation at part load with both naturally aspirated and boosted engine operation.

The initial part of the T-SGDI program enabled the successful development of a next-generation stratified charge combustion system based on spray-guided fuel injection with up to five injections per cycle. The injection sequence and injection duration was varied from a minimum of 0.1ms per injection upwards.

Subsequent research work on the multi-cylinder T-SGDI research engine has demonstrated that fuel consumption benefits were significantly enhanced through boosting, with a best BSFC of 203 g/kWh being achieved at 2250 rev/min and 13 bar BMEP.

Work reported in the paper used a spray-guided direct injection combustion system jointly developed with PETRONAS. The cylinder heads featured a transverse orientation spark plug and injector layout—i.e. the axis of the spark plug and injector was perpendicular to the crankshaft axis. The piezoelectric outwardly opening injector was located between the intake valves while the spark plug was located between the exhaust valves. Both injector and spark plug were slightly tilted towards the cylinder axis.

The piston incorporated a bowl shape, optimized for lean stratified SGDI operation. The principle design feature of the bowl was to allow for longer spray penetration lengths during late injection thus avoiding liquid fuel impingement onto the piston crown. In addition, the squish flow, generated during the compression stroke was utilized to improve the formation of a compact mixture cloud in the combustion chamber centre. The main aim of the strategy was to reduce the mixture concentration gradient in the periphery of the mixture cloud.

Experimental variables included the split of injected mass between the injection events, fuel pressure, EGR quantity, valve timing and lift to control air motion and internal residual gas fraction, and boost pressure. Rapid testing methods, analysis and final optimisation of the engine was realized using in-house Design of Experiments (DoE) techniques.

For a given engine part load condition it was shown that multiple fuel injection events resulted in improved engine combustion stability when compared to a single injection event. Furthermore, combustion stability was also less sensitive to spark timing.

The angle of 50% of mass fraction burnt in the multiple injection case was closer to the thermodynamic optimum than could be achieved in the single injection case. Low engine-out NOx emissions, an important attribute of a stratified combustion system due to the cost and regeneration fuel penalty associated with a LNT, was improved through multiple injections and external EGR.

By adding boosting to stratified operation it was possible to widen the late injection operating window from 8 bar NIMEP (net indicated mean effective pressure) to 14 bar NIMEP so unthrottled running could be maintained throughout most of the engine operating range.

The higher mass flow during part load resulting from unthrottled operation also improves turbocharger response. In addition, the best BSFC engine map areas are much closer to real-world requirements than is the case with previous stratified charge solutions. Unlike a diesel engine, there is no practical smoke-limited AFR, so lambda can be instantaneously switched from lean to λ1 or richer to maximize the air utilization for maximum torque and increased enthalpy release to the turbine for enhanced run-up.

King
SGDI multi-cylinder fuel consumption, boost, spark advance and Pmax across wider load range at 2500 rpm. The BSFC from 16 bar BMEP upwards was achieved with conventional homogenous lambda 1 operation, SOI set to 300 deg BTDCF and a single injection, fuel pressure to 150 bar, increasing airflow through increasing boost pressure, and the spark advance limited by detonation. King et al.

Combining advanced multiple injection strategies with boosting enabled the stratified operating range to be extended to over 12 bar BMEP, with a further significant improvement in fuel consumption to class leading levels. As the load exceeded 8 bar BMEP the MIVIS [Multiple Injection Variable Injection Separation] injection strategy was superior in fuel consumption terms to the multiple injection strategy used at the lower loads and on the singe cylinder engine to minimize NOx emissions. The extended WOT part load operating region also increased the mass flow through the engine versus a conventional throttle boosted gasoline engine, and this resulted in an improved transient response of the turbocharger, which is a key issue particularly for downsized gasoline engines where the downsizing ratio could be as high as 50%. Finally, the robustness of the SGDI combustion system to the highest loads in combination with the latest boosting and future knock mitigation technologies has been clearly demonstrated.

—King et al.

HyBoost. The HyBoost concept was demonstrated by Ricardo and its research partners Controlled Power Technologies, the European Advanced Lead Acid Battery Consortium, Ford, Imperial College London, and Valeo. HyBoost is based on a 2009 Ford Focus in which a 2.0L naturally aspirated four-cylinder gasoline engine is replaced with a 1.0L three-cylinder EcoBoost engine.

In implementing this 50% downsizing by swept volume, the research team had the objective of delivering zero degradation in driveability, performance or acceleration. This was achieved through the use of a combination of technologies including a belt starter-generator to provide regenerative braking and stop/start, exhaust energy recapture through electric turbo-compounding, advanced lead-acid batteries and super-capacitors to provide energy storage, and electric supercharging to provide improved transient response and avoid the pitfalls of turbo-lag that otherwise place a practical limit on the potential for downsizing.

The resulting architecture provides a highly cost-effective, low-voltage, mild hybrid gasoline powertrain delivering similar CO2 performance to a more expensive full-hybrid, but at a cost premium of less than a diesel.

Resources

  • J. King, L. Schmidt, J. Stokes, J. Seabrook, F. Nor, S. Sahadan (2012) “Multiple injection and boosting benefits for improved fuel consumption on a Spray Guided Direct Injection gasoline engine” F2012-A01-041

  • J. King, M. Heaney, E. Bower, J. Saward, A. Fraser, G. Morris, P. Blore, Mark Criddle, Thierry Chang (2012) “HyBoost – The Development of an Intelligently Electrified Optimised Downsized Gasoline Engine Concept” F2012-B02-070

December 3, 2012 in Engines, Fuel Efficiency | Permalink | Comments (4) | TrackBack (0)

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Comments

It doesn't matter how they achieve low Co2 driving, as long as they do, and this (or the Ford 1L) looks like a viable contender.

I would say: "well deserved" about the award! In general, engine consultant companies have tough times these days. They have to be in front of the development to receive commissions from car manufacturers but as soon as they come up with something really smart, car manufacturers copy it or get it almost for free by participating in the project.

That is not a discovery at all because they received an award that was already planned, so they have to give it to someone and they choosed these folks to receive it. i readed the text and this is just old inneficient combustion process that will change nothing at all. Also they said that they still need 4 years of develloppement to get it working. The important thing was for them, as it still don't work to try to get anothey 4 years of income with this idea. All that work is finnish in my view and the value of this research is worth 1 000$ maximum.

@A_D
First, I do not know what you refer to. Do you have any inside information about how FISITA decides about awards?

I do not know if yoy refer to T-SGDI or HyBoost in your comments. However, both have to be considered being at the proof-of-concept stage. It is not surprising that it takes a couple of years before a concept can be commercialized. This is particularly true if some of the sub-systems are new or if the combination of systems is new, as it is in these two cases.

I would say that the T-SGDI has taken the stratified lean-burn DI concept much further than anybody else has done so far. I you do not agree, please refer to a publication that shows better results. If we compare to one of the most advanced engines that have been in production regarding efficiency it would be the BMW 4 and 6-cylinder engines. They did not use turbocharging/downsizing and the switching point was way down in BMEP level compared to the Ricardo concept. What might be more difficult is to convince car manufacturers to use the NOx aftertreatment needed when lean-burn is under discussion. This is albeit the fact that Ricardo has reduced engine-out NOx considerably. These catalysts are expensive, they could be prone to deterioration and you also have to compromise between LNT and TWC optimization. This alone, might be a show-stopper, simply due to lack of interest from car manufacturers.

Some components of HyBoost are commercially available or close to commercialization. However, it is the first time all this has been put into one package. We could compare to the Ford Ecoboost 1-liter engine, which is commercial today. It replaces a 1.6-liter NA engine. The Ricardo engine replaces a 2-liter engine and it also reduces the absolute fuel consumption from the already low level of the Ecoboost Focus. This must be worth more than $ 1000. In fact, if the fuel consumption and CO2 is comparable with a diesel engine and cost is lower, it might be worth more than $ 1000 per car, and then you could multiply this number by one million.

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