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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.

The European Union aims to be climate neutral by 2050 and requires the transport sector to reduce their emissions by 90%. The deployment of H2ICE to power vehicles is one of the solutions proposed. Indeed, H2ICEs in vehicles can reduce local pollution, reduce global emissions of CO2 and increase efficiency. Although H2ICEs could be rapidly introduced, investigations on hydrogen combustion in ICEs are still required. This paper aims to experimentally compare a flat piston and a bowl piston in terms of performances, emissions and abnormal combustions. Tests were performed with the help of a single cylinder Diesel engine which has been modified. In particular, a center direct injector dedicated to H2 injection and a side-mounted spark plug were installed, and the compression ratio was reduced to 12.7:1. Several exhaust gas measurement systems complete the testbed to monitor exhaust NOx and H2.

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.

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.

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).

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 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.

A single cylinder Diesel engine was used to study LTC combustion. We evaluated the 2-EthylHexyl Nitrate (2-EHN) as cetane number improver (CNI) distributed by VeryOne@ on the combustion of six diesel fuels. Tested fuels are a low Cetane Number (CN) diesel fuel (CN of 43.7) and two biodiesel mixed at 20% with the low Cetane number diesel fuel: Soybean oil Methyl Ester (B100 SME) and Rapeseed oil Methyl Ester (B100 RME). Each fuels doped with the 2-EHN were prepared to meet the minimum European CN, 51. LTC strategies could provide low NOx emission without thermal efficiency deterioration. The study investigated engine operation at loads of 2, 6 and 10 bar IMEP at engine speed of 1250 rpm, 1500 rpm and 2000 rpm and the impact against synthetic EGR up to 30%. The low-temperature decomposition of 2-EHN, resulting in the oxidation of the fuel, makes it possible to achieve a very low cycle-to-cycle variation of the IMEP even at very low load or at a very high rate of EGR.

Mechanisms responsible for enhanced charge reactivity with intake added ozone (O3) were explored in a single-cylinder, optically accessible, research engine configured for low-load advanced compression ignition (ACI) experiments. The influence of O3 concentration (0-40 ppm) on engine performance metrics was evaluated as a function of intake temperature and start of injection for the engine fueled by iso-octane, 1-hexene, or a 5-component gasoline surrogate. For the engine fueled by either the gasoline surrogate or 1-hexene, 25 ppm of added O3 reduced the intake temperature required for stable combustion by 65 and 80°C, respectively. An ultraviolet (UV) light absorption diagnostic was also used to measure crank angle (CA) resolved in-cylinder O3 concentrations for select motored and fired operating conditions. The O3 measurements were compared to results from complementary 0D chemical kinetic simulations that utilized detailed chemistry mechanisms augmented with O3 oxidation chemistry.

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 transportation sector adds to the greenhouse gas emissions worldwide. One way to decrease this impact from transportation is by using renewable fuels. Ethanol is a readily available blend component which can be produced from bio blend­stock, currently used blended with gasoline from low to high concentrations. This study focuses on a high octane (RON=97) gasoline blended with 0, 20, and 50, volume % of ethanol, respectively. The high ethanol blended gasoline was used in a light duty engine originally designed for diesel combustion. Due to the high octane rating and high ignition resistance of the fuel it required high intake temperatures of 443 K and higher to achieve stable combustion in in homogeneously charged compression ignition (HCCI) combustion operation at low load. To enable combustion with lower intake temperatures more commonly used in commercial vehicles, ozone was injected with the intake air as an ignition improver.

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.

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.

Fossil fuel reserves are being depleted due to increasing energy requirements. One of the solutions is to partly replace fossil fuel by renewable biodiesel fuel. However, the physical properties of biodiesel fuels need to be thoroughly investigated before applying biodiesel or diesel-biodiesel blends in diesel engines, in order to improve the combustion efficiency. This paper presents the experimental study of diesel fuel and biodiesel blends on injection flow characteristics and fuel spray behavior. Seven fuels were tested: diesel fuel, five diesel-biodiesel blends: 10%(B10), 20%(B20), 30%(B30), 40%(B40), 50%(B50), and pure biodiesel(B100) in a diesel engine equipped with a piezo injector. Injection pressures were set at 30-180 MPa for the study of the injection flow characteristics and at 30-150 MPa for the study of spray behavior in non-vaporizing conditions.

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.

Plasma sustained ignition systems are promising alternatives to conventional spark plugs for those applications where the conditions inside the combustion chamber are more severe for spark plug operation, like internal combustion engines with high compression ratio values and with intake charge dilution. This paper shows the results of an experimental activity performed on a spark ignition engine equipped alternatively with a conventional spark plug and a radio frequency sustained plasma ignition system (RFSI). Results showed that RFSI improved engine efficiency, extended the lean limit of combustion and reduced cycle-by-cycle variability, compared with the conventional spark plug at all test conditions. The adoption of the RFSI also had a positive impact on carbon monoxide and unburned hydrocarbon emissions, whereas nitrogen oxide emissions increased due to higher temperatures attained in the combustion chamber.