Gas-to-liquid Fuels Research Articles

Investigations into the transition to sustainable alternative fuels in a South African underground platinum mine

Adverse environmental impacts associated with the use of fossil fuels and the over-dependence thereon has made energy security and sustainability a critical issue worldwide particularly for key energy intensive economic sectors which are heavily dependent on diesel. We thus investigated the feasibility of a transition to two different alternative fuels namely, rapeseed methyl ester (RME) biodiesel and gas-to-liquid fuel (GTL), in the platinum mining industry in South Africa. Load haul dump vehicles are the most abundant workhorses underground and were the selected vehicles to test alternative fuels at 100% without any engine modification. Potential reduction of harmful unregulated polycyclic aromatic hydrocarbon (PAH) emissions was the focus of the research due to their adverse impacts on the environment, human health and engine operations. Quantitative collection of gas and particle phase PAHs was made possible using portable denuder devices followed by analysis by two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. Results showed that total PAH emissions from a high idling vehicle decreased dramatically when diesel was substituted with both biofuels (total gas phase PAH concentrations of 34; 14 and 9 µg m-3 for diesel, GTL and RME, respectively) and no substantial hinderance on engine performance was reported. This novel sector specific study on unmodified heavy duty working vehicles can potentially translate into a real-world, immediate solution, as not only would the selected biofuels be able to directly replace diesel, but both have high potential of being locally produced in South Africa and assist in the promotion of a circular economy.

Spray and engine performance of cerium oxide nanopowder and carbon nanotubes modified alternative fuel

This work aims to experimentally investigate and demonstrate the impacts of using Cerium Oxide (CeO2) and multi-wall carbon nanotube (CNT) blended with the alternative fuel, which is gas-to-liquid fuel (GTL) in this study, compared to diesel fuel (DF) on engine performance and study the macroscopic spray characteristics through a Constant Volume Vessel (CVV). Results demonstrate Cerium Oxide nanopowder and carbon nanotubes have very limited impacts on the average cone angle of gas-to-liquid fuel and diesel fuel. Cerium Oxide nanopowder and carbon nanotubes can individually reduce spray penetration during injection under a small ambient pressure when blended with diesel fuel, whilst the effect on gas-to-liquid fuel is less significant because the smaller density and lighter compositions of gas-to-liquid fuel promote its breakup process. In the post-injection period, carbon nanotubes increases the spray penetration of gas-to-liquid fuel, because gas-to-liquid fuel molecules are smaller than diesel fuel. Consequently, more gas-to-liquid fuel molecules stay inside the carbon nanotubes, which can only evaporate through two ends, and thus results in an overall reduced evaporation rate. Moreover, experiments also demonstrate that the average cone angle is independent of rail pressure, but it can be reduced by decreasing ambient pressure and increasing ambient temperature. During injection, both ambient pressure and rail pressure can influence the spray penetration, whilst after the end of injection, only ambient temperature has an effect on it. The engine experiment indicates that Cerium Oxide nanopowder can reduce nitrogen oxides, unburnt hydrocarbons and particulate number emissions simultaneously for both diesel fuel and gas-to-liquid fuel due to its catalysis at high-temperature conditions, whilst carbon nanotubes has a weaker effect on reducing nitrogen oxides and particulate number for gas-to-liquid fuel than diesel fuel.

Effect of Utilizing a Novel Intake Manifold Design on Smoke Emissions and Particulate Size Distributions of a Gas-to-Liquid (GTL) Diesel Engine

Abstract Smoke emissions and particulate matter (PM) size distributions were investigated on a direct-injection single-cylinder diesel engine running on both gas-to-liquid (GTL) and diesel fuels utilizing a novel spiral-helical intake manifold design. Smoke opacity was measured at a wide range of engine loads and speeds with both fuels to examine the effect of using the new manifold on smoke emissions. In addition, total PM numbers of fine particles (PM diameter = 1.0 µm) and coarse particles (>1.0 µm) were quantified with both fuels. Moreover, high-resolution transmission electron microscopy (HRTEM) images were taken with different resolutions to observe the PM sizes produced from each fuel when using the new and normal manifolds. The results showed that using the novel manifold reduced smoke emissions for both GTL and diesel fuels with about 36% at low loads and 7% at high loads. However, using the new manifold with GTL fuel showed superior performance to reduce smoke with about 60% at low loads and 10% at high loads. For the PM size distribution, the new manifold reduced total PM emissions in general. However, significant reductions were obtained with fine PM sizes (0.3 – 1.0 µm) when GTL fuel was used with about 30% for constant load tests, and about 40% for constant speed tests. On the other hand, the new manifold tended to increase slightly the coarse PM sizes. The HRTEM images of the PM structure for both manifolds and fuels have confirmed the above results.

Transient 3D simulations of turbulent premixed flames of gas-to-liquid (GTL) fuel in a fan-stirred combustion vessel

This work aims to conduct turbulent flame studies of GTL fuel and 50/50 diesel-GTLblend and compare them to diesel under a wide range of equivalence ratio (0.7 < Ф < 1.3) and turbulence intensities (0.5 m/s < u′ < 3.0 m/s). For this purpose, Zimont Turbulent Flame Speed Closure (Zimont TFC) model is adapted and implemented into ANSYS Fluent to study the influence of turbulence on premixed combustion. The model is verified against the experimental results of the turbulent flame speeds for methane-air mixture using a cylindrical fan-stirred combustion vessel. Results show that (i) rich diesel and lean GTL fuels are characterized by a faster flame development and higher turbulent flame speeds; (ii) at the same elapsed time, ReT and Da are found to be greater for stoichiometric GTL fuel compared to diesel and 50/50 diesel GTL blend, which indicates that the flame propagates towards the vessel’s wall at a faster rate and the chemistry has dominated turbulence in a shorter time, and (iii) at low turbulence intensity level (u′=0.5 m/s), the flame morphology is defined by a wrinkled flamelet regime in Borghi diagram. However, at moderate and higher turbulence levels (u′=1.5 m/s and u′=3.0 m/s, respectively), the flame structure is defined by the corrugated flamelets regime. Furthermore, the turbulence homogeneity and isotropy have been investigated throughout the combustion vessel by conducting a study for the turbulent kinetic energy balance.

Effect of the In-Cylinder Back Pressure on the Injection Process and Fuel Flow Characteristics in a Common-Rail Diesel Injector Using GTL Fuel

The presented paper aims to study the influence of mineral diesel fuel and synthetic Gas-To-Liquid fuel (GTL) on the injection process, fuel flow conditions, and cavitation formation in a modern common-rail injector. First, the influence on injection characteristics was studied experimentally using an injection system test bench, and numerically using the one-dimensional computational program. Afterward, the influence of fuel properties on internal fuel flow was studied numerically using a computational program. The flow inside the injector was considered as multiphase flow and was calculated through unsteady Computational Fluid Dynamics simulations using a Eulerian–Eulerian two-fluid approach. Finally, the influence of in-cylinder back pressure on the internal nozzle flow was studied at three distinctive back pressures. The obtained numerical results for injection characteristics show good agreement with the experimental ones. The results of 3D simulations indicate that differences in fuel properties influence internal fuel flow and cavitation inception. The location of cavitation formation is the same for both fuels. The cavitation formation is triggered regardless of fuel properties. The size of the cavitation area is influenced by fuel properties and also from in-cylinder back pressure. Higher values of back pressure induce smaller areas of cavitation and vice versa. Comparing the conditions at injection hole exit, diesel fuel proved slightly higher average mass flow rate and velocities, which can be attributed to differences in fluid densities and viscosities. Overall, the obtained results indicate that when considering the injection process and internal nozzle flow, GTL fuel can be used in common-rail injection systems with solenoid injectors.

Macroscopic spray performance of alternative and conventional jet fuels at non-reacting, elevated ambient conditions

Gas-to-liquid (GTL) jet fuel, a liquid fuel synthesized from natural gas, has recently gained significant global attention due to its cleaner combustion characteristics when compared to the conventional jet fuels. The critical physical and chemical properties of GTL fuels are different from those of the conventional fuels, which in turn, influence the atomization, combustion, and eventually, the emission characteristics of the fuel in a jet engine. To this end, this work investigates the non-reacting near-nozzle spray performance of GTL and conventional Jet A-1 fuels using a pressure-swirl nozzle at elevated ambient conditions, which are relevant to practical combustors in a jet engine. The macroscopic spray features, such as spray cone angle, liquid sheet dynamics, and the sheet velocity, are determined using the high-speed imaging and shadowgraph technique. The ambient gas pressure is varied from 100 to 1300 kPa, and the ambient gas temperature is varied from 300 to 375 K, while the pressure difference across the nozzle is kept constant, in order to study their effect on the spray characteristics. The results show that the ambient gas pressure has a significant impact on the spray dynamics when compared to that of the ambient gas temperature, in the range examined in this work. The comparison of macroscopic spray results between the conventional and alternative jet fuels shows that the far-field spray cone angle for the GTL jet fuel is higher than those of the Jet A-1 fuel. Furthermore, in the near nozzle region, the sheet breakup region for the GTL jet fuel is slightly longer than that of the conventional fuel under the conditions studied.

Combustion and Emission Reduction Characteristics of GTL-Biodiesel Fuel in a Single-Cylinder Diesel Engine

The purpose of this paper is to investigate the effects of using gas to liquid (GTL)-biodiesel blends as an alternative fuel on the physical properties as well as the combustion and emission reduction characteristics in a diesel engine. In order to assess the influence of the GTL-biodiesel blending ratio, the biodiesel is blended with GTL fuel, which is a test fuel with various blending ratios. The effects of GTL-biodiesel blends on the fuel properties, heat release, and emission characteristics were studied at various fuel injection timing and blending ratios. The test fuels investigated here were GTL, biodiesel, and biodiesel blended GTL fuels. The biodiesel blending ratio was changed from 0%, 20% and 40% by a volume fraction. The GTL-biodiesel fuel properties such as the fuel density, viscosity, lower heating value, and cetane number were analyzed in order to compare the effects of different mixing ratios of the biodiesel fuel. Based on the experimental results, certain meaningful results were derived. The increasing rate of the density and kinematic viscosity of the GTL-biodiesel blended fuels at various temperature conditions was increased with the increase in the biodiesel volumetric fraction. The rate of density changes between biodiesel-GTL and GTL are 2.768% to 10.982%. The combustion pressure of the GTL fuel showed a higher pressure than the biodiesel blended GTL fuels. The biodiesel-GTL fuel resulted in reduced NOx and soot emissions compared to those of the unblended GTL fuel. Based on the experimental results, the ignition delay of the GTL-biodiesel blends increased with the increase of the biodiesel blending ratio because of the low cetane number of biodiesel compared to GTL. As the injection timing is advanced, the NOx emissions were significantly increased, while the effect of the injection timing on the soot emission was small compared to the NOx emissions. In the cases of the HC and CO emissions, the GTL-biodiesel blended fuels resulted in similar low emission trends and, in particular, the HC emissions showed a slight increase at the range of advanced injection timings.

Thermoelectric Energy Recovery in a Light-Duty Diesel Vehicle under Real-World Driving Conditions at Different Altitudes with Diesel, Biodiesel and GTL Fuels

This work focuses on the potential for waste energy recovery from exhaust gases in a diesel light-duty vehicle tested under real driving conditions, fueled with animal fat biodiesel, Gas To Liquid (GTL) and diesel fuels. The vehicle was tested following random velocity profiles under urban driving conditions, while under extra-urban conditions, the vehicle followed previously defined velocity profiles. Tests were carried out at three different locations with different altitudes. The ambient temperature (20 ± 2 °C) and relative humidity (50 ± 2%) conditions were similar for all locations. Exergy analysis was included to determine the potential of exhaust gases to produce useful work in the exhaust system at the outlet of the Diesel Particle Filter. Results include gas temperature registered at each altitude with each fuel, as well as the exergy to energy ratio (percentage of energy that could be transformed into useful work with a recovery device), which was in the range of 20–35%, reaching its maximum value under extra-urban driving conditions at the highest altitude. To take a further step, the effects of fuels and altitude on energy recovery with a prototype of a thermoelectric generator (TEG) were evaluated.

Influence on Performance and Emissions of an Automotive Diesel Engine Fueled with Biodiesel and Paraffinic Fuels: GTL and Biojet Fuel Farnesane

The effects of a paraffinic biofuel (farnesane) obtained from sugar cane, a gas to liquid (GTL) fuel, and a biodiesel fuel on performance and emissions of a light duty engine were evaluated. Similar engine performance is obtained with all fuels maintaining the default electronic control unit (ECU) configuration. Clear reductions in total hydrocarbon (THC) emissions were observed with all alternative fuels, and, comparing both paraffinic fuels, farnesane was more beneficial. Reductions were also obtained with these fuels in particle emissions, with the exception of the mode G, which is not an operating mode included in the New European Driving Cycle (NEDC), where particle number concentration of paraffinic fuels was higher compared with diesel and biodiesel fuels. This behavior could be explained by the nonoptimization of ECU at this engine work condition. The benefits in terms of pollutant emission obtained with farnesane make it a potential biofuel for use in diesel engines.

Chemical composition and heterogeneous reactivity of soot generated in the combustion of diesel and GTL (Gas-to-Liquid) fuels and amorphous carbon Printex U with NO2 and CF3COOH gases

The heterogeneous reactions of nitrogen dioxide (NO2) and trifluoroacetic acid (CF3COOH) with soot produced by diesel and GTL (gas-to-liquid) fuels were investigated using a Knudsen flow reactor with mass spectrometry as a detection system for gas phase species. Soot was generated with a 4 cylinder diesel engine working under steady-state like urban operation mode. Heterogeneous reaction of the mentioned gases with a commercial carbon, Printex U, used as reference, was also analyzed. The initial and the steady-state uptake coefficients, γ0 and γss, respectively, were measured indicating that GTL soot reacts faster than diesel soot and Printex U carbon for NO2 gas reactant. According to the number of reacted molecules on the surface, Printex U soot presents more reducing sites than diesel and GTL soot. Initial uptake coefficients for GTL and diesel soot for the reaction with CF3COOH gas reactant are very similar and no clear conclusions can be obtained related to the initial reactivity. The number of reacted molecules calculated for CF3COOH reactions shows values two orders of magnitude higher than the corresponding to NO2 reactions, indicating a greater presence of basic functionalities in the soot surfaces. More information of the surface composition has been obtained using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) before and after the reaction of soot samples with gas reactants. As conclusion, the interface of diesel and GTL soot before reaction mainly consists of polycyclic aromatic hydrocarbons (PAHs), nitro-compounds as well as ether functionalities. After reaction with gas reactant, it was observed that PAHs and nitro-compounds remain on the soot surface and new spectral bands such as carbonyl groups (carboxylic acids, aldehydes, esters and ketones) are observed. Physical properties of soot from both fuels studied such as BET surface isotherm and SEM analysis were also developed and related to the observed reactivity.

An experimental study on the effect of using gas-to-liquid (GTL) fuel on diesel engine performance and emissions

Gas to Liquid (GTL) fuel is considered one of the most propitious clean alternative fuels for the diesel engines. The aim of this study was to experimentally compare the performance and emissions of a diesel engine fueled by GTL fuel, diesel, and a blend of GTL and diesel fuels with a mixing ratio of 1:1 by volume (G50) at various engine load and speed conditions. Although using the GTL and G50 fuels decreased slightly the engine maximum power compared to the diesel fuel, both the engine brake thermal efficiency and engine brake specific fuel consumption were improved. In addition, using the GTL and G50 fuels as alternatives to the diesel resulted in a significant decrease in engine CO, NOx, and SO2 emissions.

Measurements of Laminar Flame Speeds of Gas-to-Liquid-Diesel Fuel Blends

This work investigates the laminar flame speed, SN, of gas-to-liquid (GTL) fuel and its 50–50% by volume blends with conventional diesel, in a cylindrical bomb capable of measuring SN at different initial temperatures and equivalence ratios at ambient pressure. SN was measured by analysing the pressure signals after combustion detected by a pressure transducer mounted on the bomb. Direct visualization has also been conducted to observe the ignition and flame propagation. It was found that pure GTL fuel has the highest SN near stoichiometric conditions, which is about 88.3 cm/s. However, at lean and rich mixtures, SN of GTL is slightly lower than that of the conventional diesel. The blended fuel has the lowest SN at lean and rich mixture conditions comparing with those of GTL and diesel fuels. Studying the effect of increasing the initial temperature on SN revealed that SN of the three tested fuels increases with the increase in the initial temperature almost linearly. However, the blended fuel has the lowest SN at the highest temperature, about 89.7 cm/s at 250 °C.

Multi-Technique Analysis of Soot Reactivity from Conventional and Paraffinic Diesel Fuels

A 2.0 L, 4-cylinder, turbocharged, common rail diesel engine was used for generating soot samples. Three fuels were tested: a “first fill” diesel fuel, a gas-to-liquid fuel (GTL) and a hydrotreated fuel derived from vegetable oils (HVO). A stationary low-load operating mode (1667 rpm and 78 Nm) was selected for testing, and some modifications in the injection process (strategy, timing and pressure) were evaluated experimentally to assess their influence in the soot reactivity. The collected soot samples were characterized using a thermogravimetric analyzer (TGA), a differential scanning calorimeter (DSC), a diffuse reflectance infrared Fourier transform spectrometer (DRIFTS) and a surface area analyzer. All techniques anticipated that HVO and GTL soot samples are more reactive (i.e. show higher potential to be oxidized at lower temperatures leading to more efficient regeneration processes in a Diesel Particle Filter – DPF) compared to diesel soot. Additionally, the four characterization techniques showed the same tendencies when analyzing the effect of the engine operating parameters. In view of the results, the paraffinic fuels – HVO and GTL – here tested confirm their promising perspective for future use in automotive diesel engines, while some guides are proposed to enhance the soot reactivity via calibration of engine operating parameters.

Impact of Animal Fat Biodiesel, GTL, and HVO Fuels on Combustion, Performance, and Pollutant Emissions of a Light-Duty Diesel Vehicle Tested under the NEDC

AbstractThis paper presents the performance, combustion, and emissions characteristics of a light-duty vehicle equipped with a Euro 4 diesel engine, operating with animal fat biodiesel, gas to liquid (GTL), hydrotreated vegetable oil (HVO), and a commercial diesel fuel (with 5.8% of biodiesel) as reference. Tests were carried out in on a chassis dynamometer under controlled ambient conditions following the New European Driving Cycle (NEDC). One of the engine cylinders was instrumented with a Kistler Kibox device combined with an opened electronic control unit (ECU) and ETAS-INCA PC system for online thermodynamic combustion diagnosis. Regulated emissions and thermodynamic diagnosis parameters have been compared at different time windows along the NEDC. Tested fuels exhibited significant reduction of CO and small variations in total hydrocarbons (THC) and NOx in comparison with commercial diesel fuel. Both specific particulate number and particulate mass were below Euro 5b directive for all tested fuels du...

Comparative Study of Biodiesel, GTL Fuel and Their Blends in Context of Engine Performance and Exhaust Emission

Crude oil price hikes, energy security concerns and environmental drivers have turned the focus on alternative fuels. Gas to liquid fuel (GTL) derived from Fisher-Tropsch synthesis, is regarded as a promising alternative diesel fuel, considering the adeptness to use directly as a diesel fuel or in blends with petroleum-derived diesel in CI engines. GTL has distinctly different characteristics than fossil diesel fuel due to its paraffinic nature, virtually zero sulphur, low aromatic contents and very high cetane number. In this study, an unmodified single cylinder 4 –stroke diesel engine was used to investigate diesel, GTL fuel and their blends in terms of engine performance and exhaust emission characteristics. GTL and its blends demonstrated improved engine performance increasing maximum power 9.1%, brake thermal efficiency 20% and lowering BSFC 9.1% than diesel. Exhaust emissions also showed diminutions in CO (22∼25%), HC (30∼40%) and NO (6∼8%). These improvements ensure the potential for the application of GTL diesel blends.

EFFECT OF FUEL PROPERTIES ON SPRAY CHARACTERISTICS OF ALTERNATIVE JET FUELS USING GLOBAL SIZING VELOCIMETRY

Increasing oil prices and strict emission policies drive the need for cleaner, alternative energy sources. Gas-to-liquid (GTL) jet fuel, a synthetic jet fuel produced from natural gas using Fischer−Tropsch synthesis, has grabbed global attention due to its cleaner combustion aspects when compared to conventional jet fuels. Since the production methodology of GTL and conventional jet fuels are different, their chemical and physical properties are different from each other. Consequently, these differences can affect atomization, mixing, combustion, and pollutant formation in the combustion chamber. Atomization is the precursor to evaporation and mixing processes. Hence, it is important to study atomization in detail in order to gain a better understanding of the other processes that directly affect combustion and emission characteristics. In this work, the microscopic spray characteristics of two GTL fuels and conventional Jet A-1 fuel are investigated and compared with each other. The spray characteristics of these fuels are studied for three injection pressures at different spatial locations downstream of a pressure swirl nozzle exit using a planar-laser diagnostic technique known as global sizing velocimetry. The results demonstrate that the influence of change in the fuel physical properties is insignificant on the spray characteristics at high injection pressures. Furthermore, the spray characteristics of the GTL fuels are found to be similar to those of the conventional Jet A-1 fuel.

Comparative study of pollutant emissions from engine starting with animal fat biodiesel and GTL fuels

Starting is a special transient process of engine operation. Due to its relevance on the overall emissions, it was included in the New European Driving Cycle (NEDC) for certification of light duty vehicles. In this work, a turbocharged, direct injection (DI), diesel engine equipped with common rail injection system and exhaust gas recirculation (EGR) strategy was tested during the starting at thermal conditions specified by NEDC, cold and warm conditions. In order to evaluate the effect of fuel composition on main pollutant emissions (nitrogen oxides, total unburned hydrocarbons, carbon monoxide, smoke opacity and number of particles) produced during this transient process, three different fuels were tested: an animal fat biodiesel, a Gas-To-Liquid (GTL) fuel from natural gas and a conventional diesel fuel with 5.83% of biodiesel, which was used as reference. Results showed that, independently of the fuel used, higher emissions were obtained at cold start. However, depending on the fuel composition pollutant emissions presented different trends.

Evaluation of the Impacts of Biodiesel and Second Generation Biofuels on NOx Emissions for CARB Diesel Fuels

The impact of biodiesel and second generation biofuels on nitrogen oxides (NO(x)) emissions from heavy-duty engines was investigated using a California Air Resources Board (CARB) certified diesel fuel. Two heavy-duty engines, a 2006 engine with no exhaust aftertreatment, and a 2007 engine with a diesel particle filter (DPF), were tested on an engine dynamometer over four different test cycles. Emissions from soy- and animal-based biodiesels, a hydrotreated renewable diesel, and a gas to liquid (GTL) fuel were evaluated at blend levels from 5 to 100%. NO(x) emissions consistently increased with increasing biodiesel blend level, while increasing renewable diesel and GTL blends showed NO(x) emissions reductions with blend level. NO(x) increases ranged from 1.5% to 6.9% for B20, 6.4% to 18.2% for B50, and 14.1% to 47.1% for B100. The soy-biodiesel showed higher NO(x) emissions increases compared to the animal-biodiesel. NO(x) emissions neutrality with the CARB diesel was achieved by blending GTL or renewable diesel fuels with various levels of biodiesel or by using di-tert-butyl peroxide (DTBP). It appears that the impact of biodiesel on NO(x) emissions might be a more important consideration when blended with CARB diesel or similar fuels, and that some form of NO(x) mitigation might be needed for biodiesel blends with such fuels.

Fuel economy and emission characteristics of Gas-to-Liquid (GTL) and Rapeseed Methyl Ester (RME) as alternative fuels for diesel engines

The effect of RME (Rapeseed Methyl Ester) biodiesel and GTL (Gas-to-Liquid) fuels on the fuel consumption and emission characteristics including particulate matter of diesel engine was investigated. The engine tests were carried out based on the ESC 13-mode test procedure. Particulate Matter (PM) distribution was analyzed using the scanning mobility particle seizer (SMPS). Compared to the base line diesel fuel;biodiesel (RME) emitted up to 70% less specific CO;up to 50% less specific HC;and 60% less specific PM emissions. For RME fuel;the majority of the particle numbers were in the diameter range of 10–30nm. For the conventional diesel and GTL fuels;the majority of PM emissions were in the diameter range of 30–200nm. The GTL fuel emitted slightly less specific CO;HC;NOx;and PM than the conventional diesel fuel. The major deficit of the biodiesel fuel was its higher specific fuel consumption rate that was in the range up to 15% (by weight) higher than the other fuels. A relatively higher NOx and CO2 emission at most of the engine loads was encountered for biodiesel fuel. The CO2 emission of the GTL fuel was up to 5% lower than the specific CO2 emission of the other two fuels.

Premixed combustion of GTL and RME fuels in a single cylinder research engine

In this paper we report the use of the optical technique applied in the cylinder of an optically accessible engine equipped with the latest-generation diesel engine head of a European passenger car. The injection strategy with high percentage of EGR, characteristic of real engine operating point, was adopted. Alternative diesel fuels were used. In particular, rapeseed methyl ester (RME) and gas to liquid (GTL) were selected as representative of 1st and 2nd generation alternative diesel fuels, respectively. Combustion analysis was carried out in the engine combustion chamber by means of 2D spectroscopic measurements from UV to visible. These measurements helped to analyze the chemical and physical events occurring during the mixture preparation and the combustion development. Ultraviolet (UV) digital imaging was also performed and the presence of characteristic radical, like OH, in the various phases of combustion was detected as well. OH spatial distribution and temporal evolution were measured. Two color pyrometry technique was applied in order to measure the soot volume fraction within the combustion chamber. The GTL fuel showed better performance in terms of indicated mean effective pressure (IMEP) with respect to the diesel reference fuel with different effects on particulate matter (PM) and gaseous emissions. It showed the highest in cylinder soot production, while the OH radical had maximum intensity value close to the reference diesel (REF) one. On the other hand, the RME fuel showed a decrease in IMEP that can be adjusted with a little increase of fuel injected quantity, and very low production of soot in the cylinder and PM at the exhaust compared to the diesel reference fuel. Finally, the OH radical had the lowest intensity value.