Low Octane Number Research Articles

Effect of diesel injection strategies on natural gas/diesel RCCI combustion characteristics in a light duty diesel engine

Reactivity controlled compression ignition (RCCI) combustion mode is an attractive combustion strategy due to its potential in satisfying the strict emission standards. In this study, the effects of direct injection (DI) strategies on the combustion and emission characteristics of a modified light duty RCCI engine, fueled with natural gas (NG) and diesel were numerically investigated. In this way, Converge CFD code employing a detail chemical kinetics mechanism was used for 3D simulation of combustion process and emissions prediction. NG with higher octane number (ON) is mixed with air through intake port, while diesel fuel with lower ON is directly injected into the combustion chamber during compression stroke by means of split injection strategy. The effects of several parameters, including the premixed ratio (PR) of NG, diesel fuel fraction in first and second injection pulses, first and second start of injection timing (SOI1 and 2), injection pressure and the spray angle on the engine performance and emission characteristics are investigated. The results indicate that these parameters have significant effects on the light duty RCCI engine performance and engine out emissions. Also, it was demonstrated that by decreasing the first injection pressure from 450 to 300bar, the gross indicated efficiency increases by 5% and CA50 is retarded by 4 CAD. Moreover, by reducing the spray angle from 144° to 100°, the gross indicated efficiency decreases by 4% and CA50 is advanced by 6 CAD. The results showed that reduction in NOx emission is achievable, while controlling HC and CO emissions, by means of increasing the NG fraction, advancing the SOI1, increasing the fuel fraction in first DI injection with lower injection pressure and employing a wider injector spray angle.

LES analysis for auto-ignition induced abnormal combustion based on a downsized SI engine

Engine knock and super-knock have become the main barriers to significantly improving engine thermal efficiency. To further study the nature of the abnormal combustion, this work quantitatively investigates engine knock and super-knock using a Large Eddy Simulation framework coupling detailed chemistry solver. Firstly, classical knocking cycles with different knocking intensities have been calculated through adjusting spark-ignition timing. It shows that knocking onset and intensity vary proportionally with the advance of spark-ignition timing, however, super-knock events are not observed under the operation conditions. Then for a given spark-ignition timing, the blends of Primary Reference Fuels are introduced in order to obtain different octane number of mixture, through which super-knock events with stronger knocking intensity are observed. The results show that as the decreases of octane number, knocking onset is significantly advanced due to the enhancement of low-temperature chemical reactivity. Consequently, more auto-ignition centers appear at hot exhaust valve side and even cool intake valve side at very low octane number. But for the knocking intensity, it does not always show a proportional correlation with octane number during super-knock. Further auto-ignition scenarios show that developing detonation wave can be induced by both multiple hot-spots auto-ignition and directly by single hot-spot auto-ignition, with different reaction front curvatures. However, the later seems to produce much stronger knocking intensity, especially when there are several developing detonation waves during super-knock. Therefore, how to effectively regulate local auto-ignition initiation and development seems the key to the avoidance of abnormal combustion in modern engines.

PPC Operation with Low RON Gasoline Fuel. A Study on Load Range on a Euro 6 Light Duty Diesel Engine

Gasoline Partially Premixed Combustion (PPC) is a promising alternative combustion concept that can offer both high indicated efficiency and low exhaust emissions in terms of NOx and soot, compared to conventional diesel combustion (CDC). Previous research has shown that PPC can operate with gasoline-like fuels of varying RON numbers. Some of the most promising results come with the use of gasoline of low octane number, around RON 70. In this study, a commercially available; 2 litre Euro 6 light duty diesel engine is being operated under various load and speed conditions with the use of RON 75 gasoline. The aim is to evaluate the ability of the engine to operate under PPC conditions with the use of as much OEM hardware installed as possible, in this case a double stage turbocharger. High amount of EGR, approximately 30%, is used in order to control NOx production and combustion reaction rates, together with a double injection strategy, which is beneficial at controlling the pressure rise rate and enable high load operation. The engine is operated at three different RPM levels, 1200-1800-2400 and between 2 to 16 bar IMEPg. Results show that combustion instability poses the limit at the low load while low oxygen content restricts the high load operation. Due to the premixed type of combustion, a fast combustion event is possible, giving a higher effective expansion ratio, which improves the indicated efficiency to levels higher than CDC, while indicated emissions are comparable to CDC operation. (Less)

EMISI GAS BUANG KENDARAAN BERMOTOR BERBAHAN BAKAR GAS CAIR (LGV) DAN PERTAMAX PADA KONDISI UJI AWAL DINGIN DAN PANAS

Liquid Gas Vehicle (LGV) is one of an alternative hydrocarbon fuel, which is the dominant composition are propane and butane, and now is already available in the market. With low sulfur content and high octane number, theoritically vehicle emissions using LGV are better than gasoline. But it is need a good mixture ratio of air to LGV (AFR) in the gas mixer before enter to the engine. This paper describes a study that compared emission test results from gasoline engine using LGV with standard mixer and Pertamax market fuel. The study was based on the vehicle chassis dynamometer test results according to the UN-ECE R83-04 test cycle standard on both cold and hot starts. The test results have shown that on urban cycle CO and HC emissions of Pertamax fuel was better than LGV on both cold and hot starts. Whereis on extra urban cycle CO emission of LGV fuel was better than Pertamax. NOx emission of LGV fuel was very low and practically undetected for all test condition. Utilisation of LGV fuel reduce CO2 emission in order of 15% for urban drive cycle for both cold and hot start, and in order of 9,2% for cold start and 10.5% for hot start for mixed cycle.

Spark assisted premixed charge compression ignition engine prototype development

Thermal efficiency of compression ignition (CI) engine is higher than spark ignition (SI) engine however heterogeneous fuel-air mixing in CI engine leads to higher NOx and soot formation. Fuel quality is deteriorating with time because of availability of heavier crude reserves. There is a need to use low volatility, low octane number fuels in the engines in an environment friendly manner. To investigate this, gasoline was blended with low volatility fuels such as diesel and kerosene. In order to improve fuel-air mixing, spark ignition of gasoline like fuels blended with low volatility diesel like fuels at higher compression ratio (11) was experimentally investigated in a prototype single cylinder partially premixed charged compression ignition (PCCI) engine. Experiments were conducted at a constant engine speed using five test fuels namely GD5 (5% v/v diesel blended with 95% v/v gasoline), GD15 (15% v/v diesel blended with 85% v/v gasoline), GK5 (5% v/v kerosene blended with 95% v/v gasoline), GK15 (15% v/v kerosene blended with 85% v/v gasoline) and G100 (100% gasoline), which was used as baseline fuel. Relative air-fuel ratio (RAFR) was maintained at 0.95 to avoid misfire at lower engine loads. Mixing and manifold injection of gasoline blended with diesel and kerosene was carried out at low pressure (3bar) using a customized common rail fuel injection system. Spark plug was used for triggering the start of combustion at a fixed spark timing of 25° bTDC. Compression ratio of spark assisted partially premixed charge compression ignition (SAPCCI) engine was kept lower than conventional CI engine to avoid auto-ignition of test fuels however it was higher than conventional SI engine to achieve greater thermal efficiency. Fuel injection timing and injection duration were controlled by a customized electronic circuit. Engine performance, emissions and combustion characteristics were investigated and compared with baseline gasoline at different engine loads. GK5 and GD5 blends exhibited higher brake thermal efficiency than baseline gasoline in SAPCCI mode, which suggested that low volatility fuels can be used in SAPCCI mode in an engine efficiently.

Experimental study on partially premixed compression ignition combustion fueled with a low octane number primary reference fuel using two-stage fuel supplying

An experimental study of partially premixed compression ignition combustion with low octane fuel was conducted on a single-cylinder engine. The effects of the external exhaust gas recirculation and intake boost on this partially premixed compression ignition combustion and emissions were investigated. During the experiments, a trade-off relationship between the NOx and smoke emissions was observed in this partially premixed compression ignition combustion. However, heavy exhaust gas recirculation usage has the potential to decrease NOx and soot emissions simultaneously at the expense of the fuel economy. It is determined that at an increased intake port pressure, the maximum in-cylinder pressure increases, and the ignition timing of the high-temperature combustion is retarded. Also, the peak value of the low-temperature combustion is slightly depressed, the peak value of the high-temperature heat release decreases significantly, and the maximum value of the diffusing burn increases to some extent. Compared to natural aspirated condition, the partially premixed compression ignition combustion with intake boost has the capability of simultaneously reducing NOx and soot emissions to ultra-low levels, that is, the intake boost could be an important strategy for the combustion and emission improvement in this advanced engine combustion mode.

Enhancement the Octane Number of Sudanese Gasoline (Nile Blend)

Gasoline is one of most important sources of energy but when manufactured with low octane number may leave great risk that affect the human health and environment impact. Therefore processes of gasoline production must be developed. Zeolite material dependence on their extremely high frame work extended interactive surface, ability to interact with molecule and cations. They show a wide variety of interesting properties which result in remarkable applications in the fields of catalysts, gas separations, selective adsorption and water softening. Zeolite catalyst loaded with finely (Sr) metal have been used in hydro-cracking, catalytic cracking. The zeolite used is the synthetic zeolite (type Y) has high thermal stability, good surface area and its heterogeneous catalyst which can be separated after treatment and may be reactivated. The study of the octane number was carried out for this zeolite. The gasoline was obtained from market (commercial gasoline) it has octane number 91.7 determined by IROX-2000.The gasoline was treated by zeolite in the temperature about 331 Kelvin. The synthetic zeolite (type-Y) raised the octane number (from 91.7 to 92.4).

Enhancement the Octane Number of Sudanese Gasoline (Nile Blend)

Gasoline is one of most important sources of energy but when manufactured with low octane number may leave great risk that affect the human health and environment impact. Therefore processes of gasoline production must be developed. Zeolite material dependence on their extremely high frame work extended interactive surface, ability to interact with molecule and cations. They show a wide variety of interesting properties which result in remarkable applications in the fields of catalysts, gas separations, selective adsorption and water softening. Zeolite catalyst loaded with finely (Sr) metal have been used in hydro-cracking, catalytic cracking. The zeolite used is the synthetic zeolite (type Y) has high thermal stability, good surface area and its heterogeneous catalyst which can be separated after treatment and may be reactivated. The study of the octane number was carried out for this zeolite. The gasoline was obtained from market (commercial gasoline) it has octane number 91.7 determined by IROX-2000.The gasoline was treated by zeolite in the temperature about 331 Kelvin. The synthetic zeolite (type-Y) raised the octane number (from 91.7 to 92.4).

Development of a new multi zone model for prediction of HCCI (homogenous charge compression ignition) engine combustion, performance and emission characteristics

Nowadays, computer models have contributed to a better understanding and solution of long standing practical combustion problems in HCCI (homogenous charge compression ignition) engines. In this study, a new multi zone model is developed for HCCI engines simulation. Model contains four different types of zones, which are core, boundary layer, zones between them, and crevice zone. Heat and mass transfer are considered between all of zones. For accurate calculation of initial conditions at IVC, multi zone model is coupled with a single zone model, which simulates gas exchange process. The developed model is validated by using two types of fuels, n-heptane as a fuel with low octane number and methane as a fuel with high octane number. Semi detailed chemical kinetics mechanisms of fuels are used for their combustion simulation. A new heat transfer model is used for calculating convective heat transfer, which enhanced the model ability in prediction of combustion and performance characteristics of engine accurately. Model results are in good agreement with experimental data in prediction of in-cylinder pressure, NOx, CO and UHC emissions. Accurate mass transfer model caused to accurate prediction of UHC (maximum error is 20.2%) and CO (maximum error is 1.8%). Near zero NOx, which is lower than 10 ppm for all of examined cases, is predicted well, too.

The outlook for fuels for internal combustion engines

The demand for transport energy is increasing, but this increase is heavily skewed toward heavier fuels such as diesel and jet fuel while the demand for gasoline might decrease. As spark-ignition engines develop to become more efficient, abnormal combustion such as knock and preignition will become more likely. High antiknock quality fuels, those with high research octane number and preferably low motor octane number, will enable future spark-ignition engines to reach their full potential. Higher fuel antiknock quality is also likely to mitigate “superknock” resulting from preignition—an abnormal combustion problem in turbocharged spark-ignition engines. In many parts of the world, fuel antiknock specifications are set on the assumption that higher motor octane number contributes to increased knock resistance. Specifications for fuel antiknock quality have a great impact on fuels manufacture and will need to be revised as this mismatch between existing specifications and engine requirements widens. The primary challenge for diesel engines is to reduce emissions of soot and NOx while maintaining high efficiency, and this becomes much easier if such engines are run on fuels of extremely low cetane. Significant development is needed before such engines can be seen on practical vehicles. In the long term, compression ignition engines are likely to use fuels with research octane number in the range of 70–85 (cetane number<∼30) but with no strict requirements on volatility. Such fuels would require less processing in the refinery than today’s fuels. Such an engine/fuels system will be at least as efficient as today’s diesel engine but could be significantly cheaper and also open a path to mitigate the imbalance in demand growth between heavy and light fuels that is expected to arise otherwise. The review concludes with a possible long-term fuel scenario.

On the Possibility to Run an Internal Combustion Engine on Acetylene and Alcohol

It is well known that acetylene is a high flammable and explosive compound. In comparison with commercial liquid fuels, very wide flammability limits and a low Octane Number have relegated the acetylene into the “iperdetonat” fuels category. Thus, it is impossible to run an internal combustion engine on acetylene without a detonation phenomena control system.The current paper deals with a theoretical and experimental analysis of an internal combustion engine running on acetylene and alcohol.A standard 8kW spark ignition engine with carburettor was modified with electronic injection control system (ECU) and two standard commercial injectors: one for the acetylene and one for the alcohol. The two injectors were installed using a modified engine intake system. The ECU is able to manage two fuels: acetylene and alcohol. Moreover, an optimization method base on Genetic Algorithms and Neural Networks was used to cerate engine parameters map. Thus, Running an ICE on acetylene and alcohol it is possible to achieve acceptable engine performance and very low pollutant emissions.

Effect of Feed Composition Changing at Naphtha Catalytic Reforming Unit Due to Involvement of Gasoline Fraction Obtained by Diesel Fuels Hydrodewaxing into the Processing

One of the primary products of hydrodewaxing process is stable gasoline, which is characterized by low octane number on the one hand. On the other hand, it contains a significant amount of iso-paraffins (on average 45% wt.) and naphthenes (on average 25% wt.), which are reagents in the naphtha catalytic reforming process primary reactions. Feasibility of stable gasoline obtained by means of diesel fuel catalytic hydrodewaxing process involving into the processing at the naphtha catalytic reforming unit has been estimated using naphtha catalytic reforming mathematical model. Technological scheme of stable gasoline from hydrodewaxing unit supply to the reforming unit is presented. Naphtha catalytic reforming and diesel fuels hydrodewaxing processes resource efficiency increases by 15–20% due to rise in catalytic reforming feed source.

N-hydrocarbons conversions over metal-modified solid acid catalysts

The quality of a straight-run fuel oil can be improved if saturated n-hydrocarbons of low octane number are converted to their branched counterparts. Poor reactivity of traditional catalysts in isomerization reactions imposed the need for the development of new catalysts among which noble metal promoted acid catalysts, liquid and/or solid acid catalysts take a prominent place. Sulfated zirconia and metal promoted sulfated zirconia exhibit high activity for the isomerization of light alkanes at low temperatures. The present paper highlights the original results which indicate that the modification of sulfated zirconia by incorporation of metals (platinum and rhenium) significantly affects catalytic performances in n-hydrocarbon conversion reactions. Favourable activity/selectivity of the promoted sulfated zirconia depends on the crystal phase composition, critical crystallites sizes, platinum dispersion, total acidity and type of acidity. Attention is also paid to the recently developed solid acid catalysts used in other conversion reactions of hydrocarbons.

자동차용휘발유의 산화열화특성 규명 연구

Gasoline generates organic acid and polymer (gum) by hydrocarbon oxidation depending on the storage environment such as temperature and exposure to sunlight, which can cause metal corrosion, rubber and resin degradation and vehicle malfunction caused by accumulation in fuel supply system. The gasoline which has not been used for a long time in bi-fuel (LPG-Gasoline) vehicle causes problems, and low octane number gasoline have evaporated into the field, but the exact cause has not been studied yet. In this study, we suggest a plan of quality management by investigating the gasoline oxidation behavior. In order to investigate the oxidation behavior of gasoline, changes of gasoline properties were analyzed at various storage conditions such as storage time, storage vessel type (vehicle fuel tank, PE vessel and Fe vessel) and storage circumstances (sunlight exposure and open system, etc.). Currently distributing gasoline and bioethanol blended fuel (blended 10%) were stored for 18 weeks in summer season. The sample stored in PE vessel was out of quality standard (octane number, vapor pressure, etc.) due to the evaporation of the high octane number and low boiling point components through the vessel cap and surface. Especially, the sunlight exposure sample stored in PE vessel showed rapid decrease of vapor pressure and increase of gum. Bioethanol blended fuel showed similar results as gasoline.

Predicted Nitric Oxide Emission from an Ethanol/Gasoline HCCI Engine

The main aim of this study is to investigate theoretically the formation of nitric oxide (NO) in a homogeneous charge compression ignition (HCCI) engine fueled with blends of ethanol and synthetic gasoline (RON25, RON50, RON75). A detailed kinetic mechanism involving 1086 chemical species and 4754 elementary reactions taking place in a HCCI engine modeled as an adiabatic single-zone reactor was applied to simulate the emission of the investigated pollutant. A close agreement between experimental and calculated results of ignition delay, species concentrations in ideal reactors, and laminar flame velocities of pure ethanol, n-heptane and iso-octane confirmed the reliability of the kinetic model. An analogous comparison, but considering a set of data (NO formation, temperature, and pressure) obtained in a single-cylinder HCCI engine operated with different mixtures of primary reference fuels (n-heptane and iso-octane) over the equivalence ratio range from approximately 0.15 to 0.4, revealed the consistency of the adiabatic single-zone model. Despite the low to moderate content of NO typically observed in the exhausts from HCCI engines, a further decrease of this pollutant was still revealed at all the considered simulating conditions when the percentage of ethanol in the fuel (synthetic gasoline) was increased. However, the extent of NO reduction was more evident for blends involving up to approximately 20% of ethanol (<E20) and synthetic gasolines with low octane number (<RON50). From a practical point-of-view, this finding reveals that the injection of a small volume of ethanol to gasoline (<20%) could be an alternative procedure to reduce the rates of exhaust gas recirculation applied to control the HCCI operation, making it a promising strategy to have a conciliation between low NO and moderate UHC and CO emissions in gasoline HCCI.

Preparation of bifunctional NiPb/ZnO-diatomite-ZSM-5 catalyst and its reactive adsorption desulfurization coupling aromatization performance in FCC gasoline upgrading process

A bifunctional NiPb/ZnO-diatomite-ZSM-5 (NiPb/ZnO-DZSM-5) catalyst for FCC gasoline upgrading by reactive adsorption desulfurization (RADS) coupling olefin aromatization function was prepared by wet-mixed squeezed method to avoid octane number loss from olefins hydro-saturation in traditional RADS processing. The crystalline structure and textural property of as-prepared adsorbents/catalysts were characterized by X-ray powder diffraction (XRD) and N2 adsorption analysis, respectively. Adsorption desulfurization and aromatization activities evaluation of FCC gasoline and model gasoline over different adsorbents/catalysts were investigated. The results showed directly introducing the composite of aromatization catalyst into the reactive adsorption desulfurization adsorbent is difficult to conquer the loss of gasoline octane number from olefin saturation and sustain the ultra deep desulfurization ability of the reactive adsorption desulfurization process simultaneously. However, the prepared Pb-modified Ni/ZnO-DZSM-5 catalysts (by introducing second metal into Ni/ZnO-DZSM-5 catalyst), exhibited improved aromatization and desulfurization performance with low octane number loss. The aromatic concentration in products increased with the additive amount of ZSM-5 in catalyst composition, meanwhile, as the adding Pb cannot destroy the original crystalline phase, Pb-modified NiPb/ZnO-ZSM-5 catalyst can inhibit olefin saturation effectively with high desulfurization activity. Regenerated bifunctional NiPb/ZnO-DZSM-5 catalyst also exhibits excellent desulfurization and aromatization performance with no octane number loss.

Kinetic Investigation of Catalyst Deactivation in Catalytic Reforming of Naphtha

Abstract Catalytic reforming of naphtha is one of the important processes for converting the naphtha with low octane number to high octane number gasoline. One the main problems in this process are deactivation of its catalysts. The catalytic reforming unit of Tabriz oil refining company was investigated in this article. This unit uses four radial reactors in series, and the Smith’s model was used for its reaction kinetics. Several models were considered for activity of catalysts to determine the major reason of catalyst deactivation. Presented models have parameters, as the objective function is optimized these parameters are obtained. In definition of the objective function the outlet temperature of reactors and outlet composition of fourth reactor should have high overlapping with experimental values. Optimization shows that deposition of coke and slightly high temperature cause the deactivation of catalysts in catalytic reforming of naphtha.

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.

Crude oil from the Guneshli deep-water oil field

The results of studying crude oil from the Guneshli deep-water oil field are reported. The oil is light, low-sulfur, low-resin, waxy crude. The naphtha cut is characterized by a low octane number. Brand KO-20 clarified kerosene and brand TS-1 jet fuel can be obtained from the light kerosene cuts, while local-grade diesel can be obtained from the diesel cuts. The potential content of base oils with a viscosity index of 72–85 in the crude is 31.4 wt. %. The crude can be refined with the fuel-oil scheme.

Selective desulphurization and denitrogenation of hydrocarbon mixtures rich in olefins

Selective desulphurization and denitrogenation of hydrocarbon mixtures rich in olefins (FCC-, pyrolysis- and coker naphtha) were investigated over three different catalysts (conventional and new generation CoMo/Al 2O 3, Pt(0.1%)Pd(0.3%)/USY). According to the experiments carried out in a wide range of operation parameters it was concluded that the sulphur removal efficiency of the PtPd/USY approximately equals to that of the new generation CoMo/Al 2O 3 up to about 200 mg/kg sulphur and 35 mg/kg nitrogen content, but the octane number loss is lower and the nitrogen removing efficiency is significantly better (nearly 100%) as well, than in case of the previous catalyst. In case of feedstock having higher sulphur and nitrogen content, the utilisation of CoMo/Al 2O 3 together with PtPd/USY in one reactor enables the production of very low sulphur (<5 mg/kg) and nitrogen (<2 mg/kg) containing products with low octane number loss.