Search Results

Effects of six different fuels on low temperature premixed compression ignition (PCI) combustion were experimentally investigated in this paper with a light-duty HSDI engine. The PCI combustion concept reduces NOx and smoke emissions simultaneously by low temperature and premixed combustion, respectively. To achieve low temperature and premixed combustion, the ignition delay is prolonged and the injection duration is shortened. Six fuels were chosen to examine the influence of cetane number (CN) and other fuel properties on low temperature PCI combustion. The fuel selection also included a pure Gas- to-Liquid (GTL) fuel and a blend of base diesel and 20% soy based biodiesel (B20). Fuel effects were studied over a matrix of seven part load points in the low temperature combustion mode. The seven part load points were specified by engine speed (RPM) and brake mean effective pressure (BMEP).

The dilution of the cylinder charge using excess air enables both an increase in the net indicated efficiency and a decrease in the engine-out emissions of nitrogen oxides. The maximum excess air dilution capability in a spark-ignition engine depends on both the ignition of the charge and the flame propagation. These two aspects can be influenced by the fuel properties, which draw attention to the laminar burning velocity of alternative fuels to extend the lean limit. Cyclopentanone and anisole show promising values regarding the laminar burning velocity. However, there is a lack of engine investigations using these two fuels. To this end, both fuels were assessed in an engine application using experimental and numerical investigations. Cyclopentanone and anisole were investigated as neat components and as mixtures with conventional gasoline fuel, resulting in seven investigated fuels.

Substitution of diesel fuel with natural gas in heavy-duty diesel engines offers significant advantages in terms of operating cost, as well as NOx, PM emissions and greenhouse gas emissions. However, the challenges of high THC and CO emissions, combustion stability, exhaust temperatures and pressure rise rates limit the substitution levels across the engine operating map and necessitate an optimized combustion strategy. Reactivity controlled compression ignition (RCCI) combustion has shown promise in regard to improving combustion efficiency at low and medium loads and simultaneously reducing NOx emissions at higher loads. RCCI combustion exploits the difference in reactivity between two fuels by introducing a less reactive fuel, such as natural gas, along with air during the intake stroke and igniting the air-CNG mixture by injecting a higher reactivity fuel, such as diesel, later in the compression stroke.

Electrification of heavy-duty trucks has received significant attention in the past year as a result of future regulations in some states. For example, California will require a certain percentage of tractor trailers, delivery trucks and vans sold to be zero emission by 2035. However, the relatively low energy density of batteries in comparison to diesel fuel, as well as the operating profiles of heavy-duty trucks, make the application of electrified powertrain in these applications more challenging. Heavy-duty vehicles can be broadly classified into two main categories; long-haul tractors and vocational vehicles. Long-haul tractors offer limited benefit from electrification due to the majority of operation occurring at constant cruise speeds, long range requirements and the high efficiency provided by the diesel engine.

Due to their CO2 reduction potential and their high knock resistance gaseous fuels present a promising alternative for modern highly boosted spark ignition engines. Especially the direct injection of LPG reveals significant advantages. Previous studies have already shown the highest thermodynamic potential for the LPG direct injection concept and its advantages in comparison to external mixture formation systems. In the performed research study a comparison of different LPG fuels in direct injection mode shows that LPG fuels have better auto-ignition behavior than gasoline. A correlation between auto-ignition behavior and the calculated motor octane number could not be found. However, a significantly higher correlation of R2 = 0.88 - 0.99 for CR13 could be seen when using the methane number. One major challenge in order to implement the LPG direct injection concept is to ensure the liquid state of the fuel under all engine operating conditions.

In order to reduce engine out CO2 emissions it is a main subject to find new alternative fuels out of renewable sources. For this paper, several fuels were selected which can be produced out of biomass or with hydrogen which is generated directly via electrolysis with electricity from renewable sources. All fuels are compared to conventional diesel fuel and two diesel surrogates. It is well known that there can be a large effect of fuel properties on mixture formation and combustion, which may result in a completely different engine performance compared to the operation with conventional diesel fuels. Mixture formation and ignition behavior can also largely affect the pollutant formation. The knowledge of the combustion behavior is also important to design new engine geometries or implement new calibrations for an existing engine. The fuel properties of the investigated fuels comprise a large range, for example in case of the derived cetane number, from below 30 up to 100.

Due to raising interest in diesel powered passenger cars in the U.S. in combination with a desire to reduce dependency on imported petroleum, there has been increased attention to the operation of diesel vehicles on fuels blended with biodiesel. One of several factors to be considered when operating a vehicle on biodiesel blends is understanding the impact and performance of the fuel on the emission control system. This paper documents the impact of the biodiesel blends on engine-out emissions as well as the overall system performance in terms of emission control system calibration and the overall system efficiency. The testing platform is a light-duty HSDI diesel engine with a Euro 4 base calibration in a 1700 kg sedan vehicle. It employs 2nd generation common-rail injection system with peak pressure of 1600 bar as well as cooled high-pressure EGR. The study includes 3 different fuels (U.S.

The increased demand in fuel economy and the reduction of CO₂ emissions results in continued efforts to downsize engines. The downsizing efforts result in engines with lower displacement as well as lower number of cylinders. In addition to cylinder and displacement downsizing the development community embarks on continued efforts toward down-speeding. The combination of the aforementioned factors results in engines which can have high levels of torsional vibrations. Such behavior can have detrimental effects on the drivetrain particularly during the development phase of these. Driveshafts, couplings, and dynamometers are exposed to these torsional forces and depending on their frequency costly damages in these components can occur. To account for these effects, FEV employs a multi-body-system modeling approach through which base engine information is used to determine optimized drivetrain setups. All mechanical elements in the setup are analyzed based on their torsional behavior.

In order to reduce engine out CO2 emissions, it is a main subject to find new alternative fuels from renewable sources. For identifying the specification of an optimized fuel for engine combustion, it is essential to understand the details of combustion and pollutant formation. For obtaining a better understanding of the flame behavior, dynamic structure large eddy simulations are a method of choice. In the investigation presented in this paper, an n-heptane spray flame is simulated under engine relevant conditions starting at a pressure of 50 bar and a temperature of 800 K. Measurements are conducted at a high-pressure vessel with the same conditions. Liquid penetration length is measured with Mie-Scatterlight, gaseous penetration length with Shadowgraphy and lift-off length as well as ignition delay with OH*-Radiation. In addition to these global high-speed measurement techniques, detailed spectroscopic laser measurements are conducted at the n-heptane flame.

Within this paper, the two possible alternative and biomass-based fuel candidates Di-n-butyl ether (DNBE) and 1-octanol are investigated with regard to their utilization in a diesel-type engine. In order to asses the fuels emission-reduction potential, both have been tested in a single cylinder engine (SCE) and a high pressure chamber (HPC) in comparison to conventional EN590 diesel at various load points. Due to its reduced reactivity 1-octanol features a longer ignition delay and thus higher degrees of homogenization at start of combustion, whereas DNBE ignites rather rapidly in both the HPC and the engine leading to a predominantly mixing controlled combustion. Thus, both fuels feature completely different combustion characteristics. However, compared to diesel, both fuels contribute to a significant reduction in Filter Smoke Number (FSN) up to a factor of 15.

Raising interest in Diesel powered passenger cars in the United States in combination with the government mandated policy to reduce dependency of foreign oil, leads to the desire of operating Diesel vehicles with Biodiesel fuel blends. There is only limited information related to the impact of Biodiesel fuels on the performance of advanced emission control systems. In this project the implementation of a NOx storage and a SCR emission control system and the development for optimal performance are evaluated. The main focus remains on the discussion of the differences between the fuels which is done for the development as well as useful life aged components. From emission control standpoint only marginal effects could be observed as a result of the Biodiesel operation. The NOx storage catalyst results showed lower tailpipe emissions which were attributed to the lower exhaust temperature profile during the test cycle. The SCR catalyst tailpipe results were fuel neutral.

Within the Cluster of Excellence “Tailor-Made Fuels from Biomass” (TMFB) at the RWTH Aachen University, two novel biogenic fuels, namely 1-octanol and its isomer dibutyl ether (DBE), were identified and extensively analyzed in respect of their suitability for combustion in a Diesel engine. Both biofuels feature very different properties, especially regarding their ignitability. In previous works of the research cluster, promising synthesis routes with excellent yields for both fuels were found, using lignocellulosic biomass as source material. Both fuels were investigated as pure components in optical and thermodynamic single cylinder engines (SCE). For 1-octanol at lower part load, almost no soot emission could be measured, while with DBE the soot emissions were only about a quarter of that with conventional Diesel fuel. At high part load (2400 min-1, 14.8 bar IMEP), the soot reduction of 1-octanol was more than 50% and for DBE more than 80 % respectively.

The occurrence of abnormal combustion events leading to high peak pressures and severe knock can be considered to be one of the main challenges for modern turbocharged, direct-injected gasoline engines. These abnormal combustion events have been referred to as Stochastic Pre-Ignition (SPI) or Low-Speed Pre-Ignition (LSPI). The events are characterized by an undesired, early start of combustion of the cylinder charge which occurs before or in parallel to the intended flame kernel development from the spark plug. Early SPI events can subsequently lead to violent auto-ignitions that are often referred to as Mega- or Super-Knock. These heavy knock events lead to strong pressure oscillations which can destroy production engines within a few occurrences. SPI occurs mainly at low engine speed and high engine load, thus limiting the engine operating area that is in particular important to achieve good drivability in downsized engines.

For gasoline engines controlled autoignition provides the vision of enabling the fuel consumption benefit of stratified lean combustion systems without the drawback of additional NOx aftertreatment. In this study the potential of certain biofuels on this combustion system was assessed by single-cylinder engine investigations using the exhaust strategy "combustion chamber recirculation" (CCR). For the engine testing sweeps in the internal EGR rate with different injection strategies as well as load sweeps were performed. Of particular interest was to reveal fuel differences in the achievable maximal load as well as in the NOx emission behavior. Additionally, experiments with a shock tube and a rapid compression machine were conducted in order to determine the ignition delay times of the tested biofuels concerning controlled autoignition-relevant conditions.

In this study the fuel influence of several bio-fuel candidates on homogeneous engine combustion systems with direct injection is investigated. The results reveal Ethanol and 2-Butanol as the two most knock-resistant fuels. Hence these two fuels enable the highest efficiency improvements versus RON95 fuel ranging from 3.6% - 12.7% for Ethanol as a result of a compression ratio increase of 5 units. Tetrahydro-2-methylfuran has a worse knock resistance and a decreased thermal efficiency due to the required reduction in compression ratio by 1.5 units. The enleanment capability is similar among all fuels thus they pose no improvements for homogeneous lean burn combustion systems despite a significant reduction in NOX emissions for the alcohol fuels as a consequence of lower combustion temperatures.

This study investigated dual-fuel operation with a light duty Diesel engine over a wide engine load range. Ethanol was hereby injected into the intake duct, while Diesel was injected directly into the cylinder. At low loads, high ethanol shares are critical in terms of combustion stability and emissions of unburnt hydrocarbons. As the load increases, the rates of heat release become problematic with regard to noise and mechanical stress. At higher loads, an advanced injection of Diesel was found to be beneficial in terms of combustion noise and emissions. For all tests, engine-out NOx emissions were kept within the EU-6.1 limit.