Low-octane Gasoline Research Articles

Physical and chemical effects of low octane gasoline fuels on compression ignition combustion

Gasoline compression ignition (GCI) engines running on low octane gasoline fuels are considered an attractive alternative to traditional spark ignition engines. In this study, three fuels with different chemical and physical characteristics have been investigated in single cylinder engine running in GCI combustion mode at part-load conditions both experimentally and numerically. The studied fuels are: Saudi Aramco light naphtha (SALN) (Research octane number (RON)=62 and final boiling point (FBP)=91°C), Haltermann straight run naphtha (HSRN) (RON=60 and FBP=140°C) and a primary reference fuel (PRF65) (RON=65 and FBP=99°C). Injection sweeps, where the start of injection (SOI) is changed between −60 and −11 CAD aTDC, have been performed for the three fuels. Full cycle computational fluid dynamics (CFD) simulations were executed using PRFs as chemical surrogates for the naphtha fuels. Physical surrogates based on the evaporation characteristics of the naphtha streams have been developed and their properties have been implemented in the engine simulations. It was found that the three fuels have similar combustion phasings and emissions at the conditions tested in this work with minor differences at SOI earlier than −30 CAD aTDC. These trends were successfully reproduced by the CFD calculations. The chemical and physical effects were further investigated numerically. It was found that the physical characteristics of the fuel significantly affect the combustion for injections earlier than −30 CAD aTDC because of the low evaporation rates of the fuel because of the higher boiling temperature of the fuel and the colder in-cylinder air during injection.

NMR Express-analyser for quality monitoring of motor fuel

A method for the rapid analysis of motor fuel quality was developed by artificial increase of the octane number through dissolving ferrocene in a low-octane gasoline (C10H10Fe). Measurements of the spin-lattice relaxation time of nuclear magnetic resonance is used for determination of ferrocene presence in standardized and real fuel from gas stations. The results of measurements of the relaxation characteristics among certain grades of motor fuel with dissolving ferrocene therein are presented.

Compression ignition of low-octane gasoline: Life cycle energy consumption and greenhouse gas emissions

The use of low-octane gasoline on Gasoline Compression Ignition (GCI) engines is considered as a competitive alternative to the conventional vehicle propulsion technologies. In this study, a process-based, well-to-wheel conceptualized life cycle assessment model is established to estimate the life cycle energy consumption and greenhouse gas (GHG) emissions of the conventional gasoline-Spark Ignition (SI) and low-octane gasoline-GCI pathways. It is found that compared with the conventional pathway, the low-octane gasoline-GCI pathway leads to a 24.6% reduction in energy consumption and a 22.8% reduction in GHG emissions. The removal of the isomerization and catalytic reforming units in the refinery and the higher energy efficiency in the vehicle use phase are the substantial drivers behind the reductions. The results indicate that by promoting the use of low-octane gasoline coupled with the deployment of GCI vehicles, considerable reductions of energy consumption and GHG emissions in the transport sector can be achieved. However, significant technical and market barriers are still to be overcome. The inherent problems of NOx and PM exhaust emissions associated with GCI engines need to be further addressed with advanced combustion techniques. Besides, the yield of low-octane gasoline needs to be improved through adjusting the refinery configurations.

Numerical Simulations of Hollow-Cone Injection and Gasoline Compression Ignition Combustion With Naphtha Fuels

Gasoline compression ignition (GCI), also known as partially premixed compression ignition (PPCI) and gasoline direct injection compression ignition (GDICI), engines have been considered an attractive alternative to traditional spark ignition (SI) engines. Lean-burn combustion with the direct injection of fuel eliminates throttle losses for higher thermodynamic efficiencies, and the precise control of the mixture compositions allows better emission performance such as NOx and particulate matter (PM). Recently, low octane gasoline fuel has been identified as a viable option for the GCI engine applications due to its longer ignition delay characteristics compared to diesel and lighter evaporation compared to gasoline fuel (Chang et al., 2012, “Enabling High Efficiency Direct Injection Engine With Naphtha Fuel Through Partially Premixed Charge Compression Ignition Combustion,” SAE Technical Paper No. 2012-01-0677). The feasibility of such a concept has been demonstrated by experimental investigations at Saudi Aramco (Chang et al., 2012, “Enabling High Efficiency Direct Injection Engine With Naphtha Fuel Through Partially Premixed Charge Compression Ignition Combustion,” SAE Technical Paper No. 2012-01-0677; Chang et al., 2013, “Fuel Economy Potential of Partially Premixed Compression Ignition (PPCI) Combustion With Naphtha Fuel,” SAE Technical Paper No. 2013-01-2701). The present study aims to develop predictive capabilities for low octane gasoline fuel compression ignition (CI) engines with accurate characterization of the spray dynamics and combustion processes. Full three-dimensional simulations were conducted using converge as a basic modeling framework, using Reynolds-averaged Navier–Stokes (RANS) turbulent mixing models. An outwardly opening hollow-cone spray injector was characterized and validated against existing and new experimental data. An emphasis was made on the spray penetration characteristics. Various spray breakup and collision models have been tested and compared with the experimental data. An optimum combination has been identified and applied in the combusting GCI simulations. Linear instability sheet atomization (LISA) breakup model and modified Kelvin–Helmholtz and Rayleigh–Taylor (KH-RT) break models proved to work the best for the investigated injector. Comparisons between various existing spray models and a parametric study have been carried out to study the effects of various spray parameters. The fuel effects have been tested by using three different primary reference fuel (PRF) and toluene primary reference fuel (TPRF) surrogates. The effects of fuel temperature and chemical kinetic mechanisms have also been studied. The heating and evaporative characteristics of the low octane gasoline fuel and its PRF and TPRF surrogates were examined.

Conversion of Straight-Run Gasoline Fraction on Combined Zeolite-Containing Catalysts

Experiments were performed on catalytic hydrogen-free upgrading of low-octane gasoline fractions on zeolite-containing catalysts with various silicate moduli. Chromatographic analysis showed the influence of a change in the molecular-sieve characteristics of zeolite-containing catalysts on the individual and group composition of the obtained gasolines. It was found to be expedient to combine zeolite-containing catalysts with various silicate moduli in the catalyst composite in order to increase the conversion of the feedstock fraction.

Temporally and spatially distributed combustion in low-octane gasoline multiple premixed compression ignition mode

An advanced combustion strategy namely “multiple premixed compression ignition” (MPCI) can exploit multiple combustion regimes. In this paper, the two-stage premixed combustion (i.e. low-temperature combustion and high-temperature combustion) using relatively low-reactivity and high volatility fuel is uncovered in MPCI mode. The mixture formation and combustion processes of low-octane gasoline MPCI mode is resolved by KIVA–CHEMKIN. The low-octane gasoline (G70H30) modeled in this study is a mixture of 70% gasoline and 30% n-heptane by volume, and it is represented by iso-octane and n-heptane oxidation mechanism. A discrete multi-component (DMC) vaporization model is used to simulate the evaporation process of G70H30, while a simplified 12-step GRI-Mech model and a two-step soot model are applied for the NOx and soot calculation, respectively. As a comparative study, partially premixed compression ignition (PPCI) mode of G70H30 is also simulated using the same numerical models. From the longitudinal and transverse sections of the combustion chamber, temporally and spatially distributed combustion events are found in the MPCI mode. That is to say, the first low temperature premixed compression ignition occurs outside of the piston bowl, and it occurs mainly in the squeeze zone above the piston triggered by the local fuel rich region. Then the second high temperature premixed combustion, which is controlled by the local turbulence resulting from the second fuel injection and chamber wall interaction, is located in the center of the combustion chamber. The temporally and spatially distributed combustion in MPCI mode decreases the local temperature, resulting in less NOx formation and lower heat transfer losses. However, there is no marked combustion distribution phenomenon in the G70H30 PPCI mode, and more NOx is generated due to higher local temperature. In addition, the early first injection of MPCI and PPCI causes spray-liner impingement, and becomes the main source of soot formation in the subsequent combustion processes.

Combustion and emission characteristics of Multiple Premixed Compression Ignition (MPCI) mode fuelled with different low octane gasolines

This paper studies the combustion and emission characteristics of three low octane fuels: naphtha, the blend of gasoline and diesel (G70D30), and the blend of gasoline and n-heptane (G70H30) in Multiple Premixed Compression Ignition (MPCI) mode. A commercial diesel fuel is also tested in conventional diesel combustion mode and double injection mode as a comparison. The study is carried out in a single cylinder diesel engine with a compression ratio of 16.7. By varying the common rail pressure, the effect of injection pressure on combustion and emissions is investigated.The results illustrate that the combustion delay of the gasoline-type fuels is extended with the increase of injection pressure. The soot emission decreases at high injection pressure with a penalty of higher CO and HC emissions. Increasing the injection pressure also reduces the particle number in accumulation mode, but produces more in nucleation mode. Among the test fuels, naphtha has the lowest NOx emission due to low combustion temperature but the highest CO and HC emissions. There is no significant difference in particle size distribution for the three fuels. The indicated thermal efficiency of gasoline-type fuels increases with the rise of injection pressure and is higher than that of diesel at high injection pressure. Naphtha has the highest efficiency as a result of its low heat transfer and exhaust loss.The diesel fuel has lower CO and HC emissions than the gasoline-type fuels do, but much higher pressure rise rate, NOx and soot emissions due to high combustion temperature and poor premixing. Therefore, the low octane gasoline fuels are more suitable than the diesel for compression ignition engines in terms of the emissions.

Effect of Premixed Fuel Preparation for Partially Premixed Combustion With a Low Octane Gasoline on a Light-Duty Multicylinder Compression Ignition Engine

Gasoline compression ignition (GCI) concepts with the majority of the fuel being introduced early in the cycle are known as partially premixed combustion (PPC). Previous research on single- and multicylinder engines has shown that PPC has the potential for high thermal efficiency with low NOx and soot emissions. A variety of fuel injection strategies have been proposed in the literature. These injection strategies aim to create a partially stratified charge to simultaneously reduce NOx and soot emissions while maintaining some level of control over the combustion process through the fuel delivery system. The impact of the direct injection (DI) strategy to create a premixed charge of fuel and air has not previously been explored, and its impact on engine efficiency and emissions is not well understood. This paper explores the effect of sweeping the direct injected pilot timing from −91 deg to −324 deg ATDC, which is just after the exhaust valve closes (EVCs) for the engine used in this study. During the sweep, the pilot injection consistently contained 65% of the total fuel (based on command duration ratio), and the main injection timing was adjusted slightly to maintain combustion phasing near top dead center. A modern four cylinder, 1.9 l diesel engine with a variable geometry turbocharger (VGT), high pressure common rail injection system, wide included angle injectors, and variable swirl actuations was used in this study. The pistons were modified to an open bowl configuration suitable for highly premixed combustion modes. The stock diesel injection system was unmodified, and the gasoline fuel was doped with a lubricity additive to protect the high pressure fuel pump and the injectors. The study was conducted at a fixed speed/load condition of 2000 rpm and 4.0 bar brake mean effective pressure (BMEP). The pilot injection timing sweep was conducted at different intake manifold pressures, swirl levels, and fuel injection pressures. The gasoline used in this study has relatively high fuel reactivity with a research octane number of 68. The results of this experimental campaign indicate that the highest brake thermal efficiency (BTE) and lowest emissions are achieved simultaneously with the earliest pilot injection timings (i.e., during the intake stroke).

Combustion and Emission Characteristics of Multiple Premixed Compression Ignition (MPCI) Mode with Low Octane Gasoline Fuels

This paper studies the combustion and emission characteristics of three kinds of low octane fuels which are naphtha, the blend of gasoline and diesel (G70D30), the blend of gasoline and n-heptane (G70H30) in multiple premixed compression ignition (MPCI) mode. Commercial diesel is also tested in conventional diesel combustion mode as a reference. The study is carried out in a single cylinder diesel engine with a compression ratio of 16.7. By varying the common rail pressure, the effect of injection pressure on combustion and emissions is investigated.The results illustrate that the combustion delay of the gasoline-type fuels is extended with the increase of injection pressure. The soot emission decreases at high injection pressure with a penalty of higher CO and HC emissions. Increasing the injection pressure also reduces the particle number in accumulation mode, but produces more in nucleation mode. Among the test fuels, naphtha has the lowest NOx emission due to low combustion temperature but the highest CO and HC emissions. There is no significant difference in particle size distribution for the three fuels. The indicated thermal efficiency of gasoline-type fuels increases with the rise of injection pressure and it is higher than that of diesel at high injection pressure.The diesel fuel has lower CO and HC emissions than the gasoline-type fuels, but much higher pressure rise rate, NOx and soot emissions due to high combustion temperature and poor premixing. Therefore, the low octane gasoline fuels are more suitable than the diesel for the compression ignition engines in terms of the emissions.

Effects of a Low Octane Gasoline Blended Fuel on Negative Valve Overlap Enabled HCCI Load Limit, Combustion Phasing and Burn Duration

Homogeneous charge compression iginition (HCCI) combustion allows for the use of fuels with octane requirements below that of spark-ignited engines. A reference gasoline was compared with iso-octane and a low octane blend of gasoline and 40% n-heptane, NH40. Experiments were conducted on a single cylinder engine operating with negative valve overlap (NVO). The fuel flow rate per cycle was compensated based on the lower heating value to maintain a constant energy addition across fuels. Iso-octane and gasoline demonstrated similar maximum load, achieving a gross IMEPg of ~430 kPa, whereas the NH40 demonstrated an increased IMEPg of ~460 kPa. The NH40 could be operated at a later phasing compared with the higher octane fuels, and exhibited a shorter burn duration at a given fueling rate and phasing. These results could be due to compositional differences, as NH40 required less NVO compared to iso-octane and gasoline, leading to less thermal and compositional stratification, as well as a higher O2 concentration and less residual gas. Additionally, the NH40 fuel demonstrated a higher intermediate temperature heat release than the higher octane fuels, potentially contributing to the shorter burn duration. Overall, these results demonstrate clear benefits to NVO enabled HCCI combustion with low octane fuels.

Comparative Study of Low Octane Gasoline Multiple Premixed Compression Ignition and Conventional Diesel Combustion

This article proposes a novel combustion mode, namely “multiple premixed compression ignition” (MPCI), in gasoline direct-injection compression ignition (GDICI) regime. Its predominant feature is the multiple premixed combustion processes in a sequence of “spray–combustion–spray–combustion” around the compression top dead center. The multiple-stage premixed combustion decouples the pressure rise with the pollutant formation process. With optimization, it can lower the rate of pressure rise and emissions simultaneously while achieving high thermal efficiency. The experimental study has been carried out in a single-cylinder research engine with a compression ratio of 18.5. Gasoline with the research octane number of 66 was tested under MPCI mode with different exhaust gas recirculation rates and injection timings. Compared to the single-stage diffusion combustion mode of conventional diesel engines, the low octane gasoline MPCI mode achieves lower emissions of smoke, NO, and CO as well as greater thermal efficiency, with a penalty of greater total hydrocation emissions.

Fuel converter for an internal combustion engine

In the paper there is proposed a fuel converter that allows to save fuel, use low-octane gasoline, and reduce exhaust emissions to meet international standards EURO 4.

Parameter study of common rail pressure for low octane gasoline multiple premixed compression ignition (MPCI) in light-duty diesel engine

A novel combustion concept called ‘multiple premixed compression ignition’ in the gasoline direct injection compression ignition regime is proposed. Its predominant feature is the first premixed and subsequent quasi-premixed combustion processes in a sequence of ‘spray–combustion–spray-combustion’ around the compression top dead center. The multiple-stage premixed combustion decouples the pressure rise from the pollutants formation process, which means the pressure rise rate and emissions can be reduced simultaneously, while achieving a high thermal efficiency. The experimental study of the multiple premixed compression ignition mode has been carried out in a single cylinder research engine retrofitted from a light-duty diesel engine with a compression ratio of 18.5. Low octane gasoline with the research octane number of 66 was tested under 1400 r/min, 0.8 MPa indicated mean effective pressure conditions, without exhaust gas recirculation or intake conditioning. A parameter study of common rail pressure was implemented to investigate its effect on the performance of the multiple premixed compression ignition mode. When the common rail pressure is 60 MPa under the foregoing operating conditions, the shortest ignition delay of the test fuel is observed. In addition, compared to the single-stage diffusion combustion in traditional diesel engines, the multiple premixed compression ignition mode with the test fuel achieves lower emissions of soot, NO and CO, as well as slightly higher indicated efficiency, with a penalty of higher total hydrocarbon emissions.

Boosted HCCI Combustion Using Low-Octane Gasoline with Fully Premixed and Partially Stratified Charges

High-load HCCI combustion has recently been demonstrated with conventional gasoline using intake pressure boosting. The key is to control the high combustion heat release rates (HRR) by using combustion timing retard and mixture stratification. However, at naturally aspirated and moderately boosted conditions, these techniques did not work well due to the low autoignition reactivity of conventional gasoline at these conditions. This work studies a low-octane distillate fuel with similar volatility to gasoline, termed Hydrobate, for its potential in HCCI engine combustion at naturally aspirated and low-range boosted conditions. The HCCI combustion with fully premixed and partially stratified charges was examined at intake pressures (Pin) from 100 to 180 kPa and constant intake temperature (60°C) and engine speed (1200 rpm). First, the key parameters for high-load HCCI operation were investigated, including 1) intermediate temperature heat release (ITHR), which determines the potential of using combustion retard to control the HRR, and 2) φ-sensitivity, which determines the effectiveness of mixture stratification for controlling the HRR. It is found that consistent with the low octane number, Hydrobate shows strong ITHR and φ-sensitivity even at Pin = 100 kPa. However, the ITHR of Hydrobate is not enhanced by increasing intake pressure, which is different from gasoline at Pin = 100-180 kPa, but similar to gasoline at Pin ≥ 180 kPa. For high-load operation, it is found that with a fully premixed charge, Hydrobate allowed higher loads than conventional gasoline for Pin < 160 kPa, mainly due to the lower intake temperature allowing a higher fueling rate. However, for Pin ≥ 160 kPa, the maximum load reached by Hydrobate was lower than gasoline due to the higher level of EGR required, which limited the oxygen available for combustion. On the other hand, higher thermal efficiency was consistently observed with Hydrobate at all Pin tested, mainly due to the lower intake temperature and more advanced combustion phasing. Applying partial fuel stratification to Hydrobate combustion further improved thermal efficiency compared to the fully premixed case, since it allowed even more advanced combustion phasing; however, it only slightly extended the high-load limit, again due to the limited oxygen availability. This work indicates that low-octane gasoline is a superior HCCI fuel for naturally aspirated and modestly boosted operations. Copyright © 2012 SAE International.

Liquid-phase adsorption and isomerization of C5-C8 n-paraffins

The liquid-phase adsorption of n-pentane, n-hexane, n-heptane, and n-octane from natural gasoline on zeolite CaA and their catalytic isomerization has been investigated experimentally and theoretically with the aim of increasing the octane number of a low-octane gasoline. An integrated process flowsheet combining processes in an adsorber and in an isomerization reactor has been developed. The basic results are as follows: the ultimate activity of CaA with respect to n-pentane, n-hexane, n-heptane, and n-octane in the case of their simultaneous adsorption at 25.0°C is 4.2, 4.7, 5.1, and 6.3 kg/100 kg, respectively. Kinetic and outlet adsorption data are also presented. The maximum yield of C5, C6, C7, and C8iso-paraffins is 62.0, 70.0, 66.0, and 47.0%, respectively. A mathematical model of the processes has been developed, and their parameters have been calculated. Calculated and experimental data are in satisfactory agreement.

Impacto económico del aumento en el precio de la gasolina en México: un análisis de cointegración y vectores autorregresivos

This article shows that the rise in the cost of low and high octane gasoline has not caused inflation in Mexico. Through an error correction model (VEC), using information from the consumer price index (CPI) and the low and high octane gasoline index for the period 2002 to 2009, the Granger-Causality test shows that CPI and Magna and Premium gasoline indexes, as well as annualized percentage changes did not cause inflation. The impulse response function and the decomposition analysis of variance in the VEC and VAR models indicate that there is not a significant effect on the level of the consumer price index during the first four months, this is due to low household spending on gasoline (3.7% of total) combined with the inelasticity of gasoline demand and the small weight of the fuel as an input in the production process (0.18% in intermediate goods and final goods 0.55% ) and the pricing of gasoline by the Federal Government. Although the gasoline indexes and the consumer price index are cointegrated, their impact on the CPI is not significant, reflecting the price control of gasoline in Mexico

Improving catalysts for the refining of straight-run gasoline fractions of petroleum

We propose a method for modifying catalysts based on a high-silica zeolite of the ZSM-5 type using Ni nanopowder to improve catalysts for the refining of straight-run gasoline fractions. The proposed method, which involves solid-phase mechanical mixing with Ni nanopowder, is more environmentally friendly than conventional methods of impregnation and ion exchange; the developed Ni-containing zeolite catalysts allow us to lower the temperature for the refining of low-octane gasoline fractions by 20–40°C and to increase the yield of target products containing high amounts of high-octane components, i.e., isoalkanes. The acidic and catalytic properties of high-silica zeolites containing different amounts of Ni nanopowder were studied. The activity of the catalyst systems in the conversion of straight-run gasoline fractions of petroleum was analyzed. The optimum catalyst composition and the process conditions for obtaining a maximum yield of the target product, i.e., high-octane gasoline, are determined.

An Experimental Investigation of Low-Octane Gasoline in Diesel Engines

Conventional combustion techniques struggle to meet the current emissions norms. In particular, oxides of nitrogen (NOx) and particulate matter (PM) emissions have limited the utilization of diesel fuel in compression ignition engines. Advance combustion concepts have proved the potential to combine fuel efficiency and improved emission performance. Low-temperature combustion (LTC) offers reduced NOx and PM emissions with comparable modern diesel engine efficiencies. The ability of premixed, low-temperature compression ignition to deliver low PM and NOx emissions is dependent on achieving optimal combustion phasing. Diesel operated LTC is limited by early knocking combustion, whereas conventional gasoline operated LTC is limited by misfiring. So the concept of using an unconventional fuel with the properties in between those two boundary fuels has been experimented in this paper. Low-octane (84 RON) gasoline has shown comparable diesel efficiencies with the lowest NOx emissions at reasonable high power densities (NOx emission was 1 g/kW h at 12 bar BMEP and 2750 rpm).

Catalytic activation of C1—C3 alkanes

The conversion of CH4 and the C6H6—C3H8 mixture over (M, ReOx)/Al2O3 (M = Ni, Co, Pt) analogues of industrial low-octane gasoline reforming catalysts containing 0.5 wt % M in a finely divided state and 0.3–1.0 wt % Re is reported. The unreduced catalysts activate the conversion of CH4 into C6H6 at 650°C. Using (M, ReOx)/Al2O3 + HZ catalytic mixtures (HZ = H-form of zeolite Y, M, or ZSM-5), it is possible to carry out low-temperature C6H6 alkylation or C3H8 dehydrogenation at 180–350°C. These processes are aimed at involving oil refining waste into obtaining valuable hydrocarbons. The processes can be commercial- ized at low-octane reforming and gas-phase benzene alkylation plants and can be intensified by separating the resulting H2 in membrane reactors.

Production of olefin and aromatic hydrocarbons by pyrolysis of gas condensate

0009-3092/09/4506–0440 © 2009 Springer Science+Business Media, Inc. In Algeria, gas condensates occupy second place after crude with respect to volume of recovery. They are exported to France, Belgium, countries of South America, and certain other countries, and are also used to produce the 85-180°C cut and diesel fuel. The 85-180°C cut is directed into a reformer for the production of high-octane reformate. Algerian gas condensates contain mixtures of paraffins and naphthenes, and also a small amount of aromatic hydrocarbons. Since these condensates have a paraffin-naphthene base, it is possible to use them as pyrolysis feedstock for the production of olefins and aromatic condensates [1, 2]. The olefin hydrocarbons serve as feedstock for the production of polymers, and the aromatic hydrocarbons as feedstock for pyrolysis – high-octane additives to premium-grade commercial gasolines At the present time, low-octane gasoline cuts are subjected to pyrolysis, as a result of which the volume of the 85-180°C cut – reformer feedstock, is reduced. The purpose of this paper is to investigate laws governing pyrolysis of the 36-279°C cut of gas condensate, and ascertain optimal conditions for the production of ethylene and propylene. Physico-chemical characteristics of this cut are presented below: