Researchers in POWERFUL develop new two-stroke diesel featuring low consumption and low criteria emissions

4 November 2014

Two-stroke diesel in test car. Click to enlarge.

A European project led by Renault, in collaboration with the Czech Technical University in Prague, IFP Energies Nouvelles, Delphi, Le Moteur Moderne (LMM) and Universitat Politècnica de València have developed an advanced two-cylinder, two-stroke compression ignition (CI) engine integrating LTHC (low temperature homogeneous combustion) as part of the European project POWERFUL (POWERtrain for FUture Light-duty vehicles).

The €25-million (US$31-million) FP7 project, which ended in June, also supported two other engine projects: an advanced four-stroke two-cylinder SI engine concept characterized by low-cost / low emissions; and an advanced four-stroke, three-cylinder CI engine concept able to run also on new tailored fuels and integrating the LTC (low temperature combustion) mode in the CI combustion system.

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The objective of POWERFUl was to design engines for light-duty urban and micro-urban vehicles (segment A and B), capable of reducing CO₂ and criteria pollutant emissions. The main feature of the Spanish, French and Czech researchers’ work is the reduction in the engine’s weight and size, which results in a high specific power.

The 2-stroke, two-cylinder 730 cm³ engine uses a valve scavenging architecture, with the combustor head defined to optimize the scavenging. Injection pressure is up to 2,000 bar, delivered by the latest common rail generation combined with a high performance HP pump designed to limit the weigh to contribute to the CO2 reduction. A new generation of fast solenoid injector was proposed with improved multiple injection control and limited leakage.

We have been able to reduce the engine weight by between 50 and 60% with regard to the equivalent four-stroke engine. This entails a significant saving in fuel consumption, as well as a reduction in the cost of the engine itself.

With fewer cylinders, the friction produced in the engine is reduced, increasing its mechanical output and, finally, its overall performance. The engine has been designed for small vehicles such as the Renault Twingo, in which it has been applied.

The validation tests of the engine were performed at CMT-Motores Térmicos at the Universitat Politècnica de València. The researchers of the UPV proved its potential for reducing pollutant emissions and fuel consumption compared to the four-stroke version currently available on the market. Moreover, they studied the possibility of implementing new advanced combustion concepts, as alternatives to the conventional diesel system, with what they said was very promising results.

The research effort is now focused on the development of a boosting system that increases the actual levels of maximum power to the equivalent of a four-stroke engine.

Now the engine needs 20% more power, but it weighs 50% less, so the ratio gives more power per unit of weight (specific power), but not twice as much, which is what it should be. It gives around 1.7 times more. It is necessary to increase the power to a ratio of 2.

Renault and the IFP Energies Nouvelles are leading this work. In addition, Renault and CMT-Motores Térmicos are continuing their collaboration focusing on the analysis and optimization of new advanced concepts of combustion.

The researchers at Renault and CMT-Motores Térmicos presented the performance, characteristics and output of this new engine at the conference THIESEL 2014 (Thermo- and fluid-dynamic processes in direct injection engines), held at the beginning of September at the Universitat Politècnica de València.

Resources

• J. Benajes, R. Novella, D. de Lima (2014) “Analysis of combustion concepts in a newly designed 2-stroke HSDI compression ignition engine” (THIESEL 2014)

• Benajes, J., Martin, J., Novella, R., and De Lima, D. (2014) “Analysis of the Load Effect on the Partially Premixed Combustion Concept in a 2-Stroke HSDI Diesel Engine Fueled with Conventional Gasoline,” SAE Technical Paper 2014-01-1291 doi: 10.4271/2014-01-1291

• Jesus Benajes, Ricardo Novella, Daniela De Lima, Pascal Tribotté, Nicolas Quechon, Philippe Obernesser, Vincent Dugue (2013) “Analysis of the combustion process, pollutant emissions and efficiency of an innovative 2-stroke HSDI engine designed for automotive applications,” Applied Thermal Engineering, Volume 58, Issues 1–2, Pages 181-193 doi: 10.1016/j.applthermaleng.2013.03.050