Search Results

Compressed natural gas (CNG) is considered as one of the most promising alternative fuels for transportation due to its ability to reduce greenhouse gas emissions and its abundance. More specifically, CNG has a considerable potential when used as a dedicated fuel on a downsized turbo-charged SI engine for a small urban vehicle. This approach can be profitably extended by adding a small secondary (electrical) power source to the CNG engine, thus hybridizing the powertrain. This is why IFP has developed a mild-hybrid CNG prototype vehicle based on a MCC smart car equipped with a starter-alternator and ultra-capacitors (the StARS system). This solution offers some interesting functions such as “Stop'n'Start”, regenerative braking, torque boosting and engine assistance, and yields significant benefits in terms of fuel economy, reduced exhaust emissions and better driveability.

Compressed natural gas (CNG) is considered as one of the most promising alternative fuels for transportation due to its ability to reduce greenhouse gas emissions (CO2, in particular) and its abundance. An earlier study from IFP has shown that CNG has a considerable potential when used as a fuel for a dedicated downsized turbo-charged SI engine on a small urban vehicle. To take further advantage of CNG assets, this approach can be profitably extended by adding a small secondary (electrical) power source to the CNG engine, thus hybridizing the powertrain. This is precisely the focus of the new IFP project, VEHGAN, which aims to develop a mild-hybrid CNG prototype vehicle based on a MCC smart car equipped with a reversible starter-alternator and ultra-capacitors (Valeo Starter Alternator Reversible System, StARS).

Pollutants emissions from transportation have become a major focus of environmental concerns in the last decades. Many alternative fuels are under consideration, among which Natural Gas as fossil resource offering an advantageous potential to reduce local emissions. The European Commission has set an objective of 10% of Natural Gas consumption for the transport sector by 2020. In a sustainable development view, both vehicle emissions and energy supply chain analysis from well to wheel must be addressed. Even if the main focus today is on CO2 emissions, it is interesting to evaluate the pollutant emissions of the whole Well to Wheel chain. Besides, as the potential of reducing pollutant emissions of vehicle (due to the improvement of engines and severization of norms), looking at pollutant emissions of the Well to Tank part of the chain could show the possible further improvements. Former studies exist, comparing Natural Gas to conventional and non conventional fuels.

The main objective of this project was to confirm the high potential of Natural Gas as fuel for downsizing turbocharged engines. For this purpose, a demonstrator vehicle has been developed when modifying a Smart gasoline vehicle. The target was to achieve low CO2 emissions with a maximum level of 100 g/km on a European Driving Cycle (NEDC), while keeping pollutant emissions below the EURO IV level. At full load conditions, thermal efficiency is 25% higher than for gasoline. That represents a CO2 gain of 35%. After a brief description of the main Natural Gas characteristics as a transportation fuel, the downsizing approach will be described as a most promising way to reduce engine specific fuel consumption. Results obtained on bench and with the Natural Gas Smart vehicle will be presented focusing the CO2, regulated emissions, drive-ability and driving range in accordance with “urban” expectations.

This paper describes the successive stages needed to develop a lean-burn natural gas engine. A wide optimization was undertaken with the view to power commercial medium duty vehicle able to meet the 2005 proposals with the European MVEG cycle. PSA Peugeot Citroen DJ5TED 2.5 Liters displacement Direct Injection Diesel engine was chosen to be converted to natural gas Spark Ignition engine. On the basis of findings from simulation using the KMB computer code, combustion chambers of three different shapes were selected, meeting specific air flow motion criteria. After fitting sparkplug and ignition system providing high-energy required under lean operation, the chamber shape showing the best emissions-consumption trade-off was selected from engine bench tests. Then, after turbocharger matching, optimizations were carried out on lean and stoichiometric mixture in order to ensure excellent exhaust emissions and output performances.

The development phases and test bench results related to the conversion of a bus Diesel engine of 6 cylinder 9.8 L displacement to an aftercooled turbocharged Spark Ignition (SI) compressed natural gas engine are reported. A pre-screening of various piston shapes was performed using the KMB CFD code to determine the most promising intake-chamber geometries according to computed mean flow and turbulence results. Then, the designed pistons were built for engine tests. Ignition characteristics, valve lift laws, bowl shape and swirl level were optimized to find the trade-off between efficiency and emissions. The finally retained solution reaches performances very close to the starting Diesel engine by running ultra lean (λ > 1.8) with a maximum thennal efficiency larger than 40% for a compression ratio of 12.5: 1. The complementary use of an efficient oxidizing catalyst allows nitrogen oxide emissions lower than lg/kWh for the European 13 mode cycle.