Search Results

Ammonia and hydrogen can be produced from water, air and excess renewable electricity (Power-to-fuel) and are therefore a promising alternative in the transition from fossil fuel energy to cleaner energy sources. An Homogeneous-Charge Compression-Ignition (HCCI) engine is therefore being studied to use both fuels under a variable blending ratio for Combined Heat and Power (CHP) production. Due to the high auto-ignition resistance of ammonia, hydrogen is required to promote and stabilize the HCCI combustion. Therefore the research objective is to investigate the HCCI combustion of varying hydrogen-ammonia blending ratios in a 16:1 compression ratio engine. A specific focus is put on maximizing the ammonia proportion as well as minimizing the NOx emissions that could arise from the nitrogen contained in the ammonia. A single-cylinder, constant speed, HCCI engine has been used with an intake pressure varied from 1 to 1.5 bar and with intake temperatures ranging from 428 to 473 K.

The present investigation examines a new way to control the homogeneous charge compression ignition (HCCI) process. An ozone generator was set up to seed the intake of a single-cylinder engine with low concentrations of ozone. Two kinds of gas supply were tested: an oxygen supply and an air supply; as well as two kinds of injection: a plenum injection and an injection inside one of the intake pipes. The results showed that air can easily be used and that the second injection mode is the best way to achieve an on-road application. Moreover, experiments demonstrated that each combustion parameter such as the phasing, the indicated mean effective pressure and the pollutants can be controlled by varying the capacity of the ozone generator. Then, from experimental results, two dynamic control approaches on the maximum pressure phasing were proposed.

In the search for zero-carbon emissions and energy supply security, hydrogen is one of the fuels considered for internal combustion engines. The state-of-the-art studies show that a good strategy to mitigate NOx emissions in hydrogen-fueled spark-ignition engines (H2ICE) is burning ultra-lean hydrogen-air mixtures in current diesel architectures, due to their capability of standing high in-cylinder pressures. However, it is well-known that decreasing equivalence ratio leads to higher engine instability and greater cycle-to-cycle variations (CCVs). Nevertheless, hydrogen flames, especially at low equivalence ratios and high pressures, present thermodiffusive instabilities that speed up combustion, changing significantly the flame development and possibly its variability. This work evaluates the hydrogen combustion and their CCVs in two single-cylinder diesel baseline H2ICEs (light-duty and medium-duty) and their influence on performance parameters.

A single cylinder Diesel engine was used to study combustion stability changes from a cetane number improver: 2-EHN. It has been added to a low cetane number diesel and two biodiesels blends with 20 % of SME or RME. All fuels have been raised to a CN of 51 with 2-EHN. Those fuels have been compared to a reference diesel with a CN of 55. Cold and warm start have been recreated for measurements at three conditions: cranking, engine speed increase and idle. Engine coolant temperature has been set to 20°C and 80°C for cold and warm start respectively. 2-EHN effects on combustion stability have been monitored through the IMEP covariance. Under cold-start, only the low cetane number diesel showed combustion stabilities improvements with 2-EHN addition. Moreover, the combustion stability was better than the reference diesel and the heat release rate show an enhancement of the cold flame. On the contrary, the biodiesel fuels exhibited higher IMEP covariances.

Internal combustion engine downsizing allows the reduction of fuel consumption, in particular for those applications where the engine operates frequently at part load conditions. This design solution is usually combined with intake charge dilution by means of exhaust gas recirculation, for the purpose of limiting abnormal combustion events, reducing pumping losses and nitrogen oxide formation. While the exhaust gas recirculation is widely used in compression ignition engines, it still causes some technological issues, in particular for spark ignition engines. This paper presents the results of an experimental campaign performed on a spark ignition engine for the investigation of different dilution techniques for low temperature combustion. Nitrogen, carbon dioxide and exhaust gas recirculation have been adopted as diluents, comparing engine performance and pollutant emissions.

Homogeneous Charge Compression Ignition (HCCI) is among the new generation of combustion modes which can be applied to internal combustion engines. It is currently the topic of numerous studies in various fields. Due to its operating process, HCCI ensures a good efficiency, similar to that of compression ignition (CI) engines, and low particulate and nitric oxide (NOx) emissions. However, before promoting the use of this kind of engine, several challenges must be addressed, in particular controlling the combustion. Recent work showed that the combustion phasing can be controlled using low concentrations of ozone, an oxidizing chemical species. As ozone generators become increasingly compact, the integration of this kind of device in passenger cars can be considered. The present study investigates the effect of ozone on the combustion of different fuel mixtures. The engine was fuelled with various blends: a 95%methane/5%propane mixture and three different methane/hydrogen mixtures.

The increased utilization of batteries and fuel-cells for powering electric applications, as well as bio- and e-fuels into internal combustion engines are seen as options to lower the carbon footprint of industry and transportation sectors. When high power outputs and fast refueling are requisites, H2 ICEs may be a relevant choice. Applications include electricity conversion within a genset or mechanical energy in a vehicle. Within this framework, a John Deere 4045 Diesel engine converted to a H2 single-cylinder is studied at relevant operating conditions for the mentioned use cases, which pose high torque and power output requirements. The modified engine integrates a Phinia DI-CHG 10 outward-opening H2 injector instead of the Diesel unit, as well as a spark-plug rather than the glow-plug.

Dihydrogen, as a zero CO2 fuel, is a strong candidate for internal combustion engine to limit global warming. This study shows the impact of standard tuning parameters on mixture homogeneity and combustion characteristics. A 2.2L Diesel engine on which the head was reworked to allow side mounted direct injector and central mounted spark plug was selected. The discussed tests were made at low engine speed and partial load. A spark advance sweep at different air-fuel ratios (λ) was conducted. The exponential relation between λ and NOx emissions is highly marked and extremely low NOx emissions up to 1.7 g/kWh at minimum spark advance for maximum brake torque can be measured. A λ sweep was performed at different starts of injection (SOI). The results show that, depending on the engine speed, a later SOI might lead to lower NOx emissions. For a λ setpoint of 1.8, at 1500 rpm, late SOI leads to 30% higher NOx emissions where at 2500 rpm these emissions are 26% lower.

In the present study, experiments were carried out in a single-cylinder downsized SI engine with different rates of oxygen (15% to 27% by volume in the total mixture of intake gases except fuel) and equivalence ratios (from 0.45 to 1). Therefore, the oxygen volume fraction is due to oxygen enrichment or nitrogen dilution. The study of the impact of controlling oxygen concentration on the combustion characteristics and emissions was performed at 1400 rpm, at several loads (Indicated Mean Effective Pressure (IMEP) from 400 to 1000 kPa). For each operation point, the spark advance and the intake pressure were adjusted simultaneously in order to maintain the load and obtain a minimum value of indicated Specific Fuel Consumption (SFC). The effect of oxygen concentration on the engine combustion characteristics was simulated by using the commercial software AMESim, with the combustion model developed by IFP-EN, and an adapted algorithm was used to avoid residual gas calibration.

Ammonia is a widely used and known chemical. Today it is seen as a carbon free solution to fuel thermal engines especially in applications where other solutions would not be realistic. For marine applications, electrical or fuel cells solutions for example would not allow spans long enough to sustain big cargo ships ranges. Engine manufacturer such as MAN, Wartsila or Win-GD have already announced the development of marine engine running on ammonia. But while ammonia is a non-CO2 emitting fuel, it has some caveats such as being gaseous in standard conditions and hard to ignite. As it is now, ammonia is usually used in compression ignition engines with the help of highly reactive carbonated pilot fuels. Many forms of dual-fuel combustion are conceivable, although all the simple ones use a carbon-based fuel and quite often originated from fossil oil.

When a biofuel, methanol is an interesting alternative for internal combustion engines (ICE). Despite drawbacks such as misfiring or instabilities at low loads, methanol has several advantages. Today, dual-fuel systems allow the use of methanol in combination with diesel fuel. This paper will present a different approach, the ability to use methanol in a flex-fuel system. The addition of a combustion enhancer containing alkyl nitrate (CEN) allows the use of methanol in a direct-injection compression ignition (DICI) engine without any changing. In this paper, different volume fractions of this additive are tested. The aim is to show the effect of the CEN on the combustion of methanol. The effect of CEN on methanol has been confirmed thanks to previous tests carried out on a Rapid Compression Machine (RCM). Ignition delay times (IDT) and auto-ignition temperature were reduced with small amounts of CEN.

As an alternative to second generation ethanol, valeric esters can be produced from lignocellulose through levulinic acid. While some data on these fuels are available, only few experiments have been performed to analyze their combustion characteristics under engine conditions. Using a traditional spark ignition engine converted to mono-cylinder operation, we have investigated the engine performances and emissions of methyl and ethyl valerates. This paper compares the experimental results for pure valeric esters and for blends of 20% of esters in PRF95, with PRF95 as the reference fuel. The esters propagate faster than PRF95 which requires a slight change of ignition timing to optimise the work output. However, both the performances and the emissions are not significantly changed compared to the reference. Accordingly, methyl and ethyl valerate represent very good alternatives as biofuels for SI engines.

Hydrogen-fueled internal combustion engines (H2ICEs) have emerged as a promising technology for reducing greenhouse gas emissions in the transportation sector. However, due to the unique properties of hydrogen, especially under ultra-lean conditions, the combustion characteristics of hydrogen flames differ significantly from those of conventional fuels. This research focuses on evaluating the combustion process and cycle-to-cycle variations (CCVs) in a single-cylinder port-fuel injection H2ICE, as well as their impact on performance parameters. To assess in-cylinder combustion, three indicators of flame development are utilized and compared to the fundamental properties of hydrogen. The study investigates the effects of various factors including fuel-air equivalence ratio (ranging from 0.2 to 0.55), engine load (IMEP between 1 and 4 bar), and engine speed (900 to 1500 rpm).

The present social context imposes effective reductions of transport greenhouse gases and pollutant emissions. To answer to this demand, car manufacturers adopted technologies such as downsizing, turbocharging, intense in-cylinder aerodynamics and diluted combustion process. In this context, to master mixture ignition is crucial to ensure an efficient heat release. To get to a clearer knowledge about the physics holding early stages of premixed mixture combustion, the PRISME institute in the framework of the French government research project ANR MACDOC generated a consistent experimental database to study ignition and spherical flame propagation processes in a constant volume vessel in laminar and turbulent environment.

Biogas is a gas resulting from biomass, with a volumetric content of methane (CH4) usually ranging between 50% and 70%, and carbon dioxide (CO2) content between 30% and 50%; it can also contain hydrogen (H2) depending on the feedstock. Biogas is generally used to generate electricity or produce heat in cogeneration system. Due to its good efficiency through the rapid combustion and lean air-fuel mixture, Homogeneous Charge Compression Ignition (HCCI) engine is a good candidate for such application. However, the engine load must be kept low to contain the high-pressure gradients caused by the simultaneous premixed combustion of the entire in-cylinder charge. The homogenous charge promotes low particulate emissions, and the dilution helps in containing maximum in-cylinder temperature, hence reducing nitrogen oxide emissions. However, HC and CO levels are in general higher than in SI combustion.

Increasingly stringent pollutant emission regulations have constrained car manufacturers to reduce the fuel consumption and pollutant emissions of internal combustion engines. Downsized engines appear to be the most promising way to achieve this in terms of emission reduction as well as investment minimization. The design of downsized internal combustion engines requires the understanding and quantification of thermo-fluid-dynamic processes at high pressure, high temperature and with high dilution rate. This study aims to carry out preparatory work in a fan-stirred spherical combustion vessel at conditions representative of those occurring in downsized engines. First, experimental correlations giving the laminar burning velocity from the initial pressure, the initial temperature, the dilution rate and the equivalence ratio are proposed.

Increasing the internal combustion engine efficiency is necessary to decrease their environmental impact. Several combustion systems demonstrated the interest of low temperature combustion to move toward this objective. However, to ensure a stable combustion, the use of additives has been considered in a several studies. Amongst them, 2-Ethylhexyl nitrate (EHN) is considered as a good candidate for these systems but characterizing its chemical effect is required to optimize its use. In this study, its promoting effect (0.1 - 1% mol.) on combustion has been investigated experimentally and numerically in order to better characterize its behavior under different thermodynamic and mixture. Rapid compression machine (RCM) experiments were carried out at equivalence ratio 0.5 and pressure 10 bar, from 675 to 995 K. The targeted surrogate fuel is a mixture of toluene and n-heptane in order to capture the additive effect on both cool flame and main ignition.

For a better understanding of how soot is generated due to fuel films, a constant volume vessel was used together with four visualization techniques due to their high spatial (2D) and time resolution: Schlieren, natural luminosity, diffused back illumination and OH* chemiluminescence. The analysis was performed keeping the injection pressure at 30 bar and changing the plate temperature on which the spray impacts: 80, 120, 160 and 200 °C. The fuel is a mixture of iso-octane, hexane, toluene and 1-methylnaphthalene, which presents similar properties to commercial gasoline. Valuable insights were gained from the results that infer the real nature of the radiation observed during combustion events in gasoline direct injection (GDI) engines due to the presence of a fuel films which are conventionally described as “pool fires”. The results show that the highest quantity of soot is generated between plate temperatures of 80 and 120 °C.

As the world moves towards a decarbonized motorization, Hydrogen became a strong candidate to replace Diesel and Gasoline. Possibly used in a DI configuration, a huge challenge is the injection and mixing process of the hydrogen in the combustion chamber. In this paper we will focus on the characterization of a compressed hydrogen jet using Schlieren imaging technique and image processing. The injector used in those tests is designed and manufactured by BorgWarner to be used specifically with Compressed Hydrogen Gas (CHG). It operates at medium pressure. Two injection pressures had been used to study the jet development in different conditions. The cylinder pressure (back pressure) will vary between 1.2 bar and 15 bar while the temperature will go from 20°C to 150°C. The discussed tests were made in full nitrogen conditions to avoid any ignition of the hydrogen jet.

In this work, the first injection of gasoline was maintained at 30 CAD Before TDC and the second one was swept between 10 CAD Before TDC to 5 CAD After TDC, in order to demonstrate the ideal positioning of the second injection. The results showed that when it was placed near TDC, low emissions, acceptable noise and acceptable efficiencies could be obtained. The effect of EGR, simulated by N2 addition, was also studied. As expected, globally the effect of the EGR rate was to delay the combustion phasing and to decrease NOx emissions. The optimal EGR dilution rate was found to be 30% with respect to the cycle-to-cycle variation criterion (< 5%). Increasing the dilution rate increased HC, CO and PM emissions, due to a considerable delay in combustion phasing caused by the reduction in the fuel reaction rate and the in-cylinder lack of oxygen when the EGR rate reached 30%. The impact of the fuel mass distribution between the two injections was also considered.