High Cetane Number Fuels Research Articles

IMPACT OF OPERATING PARAMETERS ON ENERGY EFFICIENCY AND REGULATED EMISSIONS OF DUAL FUEL DIRECT INJECTED REACTIVITY-CONTROLLED COMPRESSION-IGNITION COMBUSTION

ABSTRACT In the current investigation, a modified non-road naturally aspirated conventional RCCI (i.e., PFI RCCI) engine has been replaced with low-pressure gasoline and high-pressure diesel dual fuel direct injection (DFDI) system and successfully investigated. Direct injection of low and high Cetane number fuels enhanced the in-cylinder stratification of the injected fuels and decreased the gasoline contact with the crevice region. Detailed tests have been conducted on the DFDI engine by sweeping the operating parameters, such as gasoline energy ratio (GER), the number of gasoline/diesel injection, gasoline/diesel mass and exhaust gas recirculation (EGR). The experimental results indicated that DFDI RCCI combustion increased the combustion efficiency by 8% and brake thermal efficiency (BTE) by 3% compared to conventional RCCI combustion. The simultaneous reduction in NO and Soot emission was observed in DFDI RCCI. Also, hydrocarbon (HC) and carbon monoxide (CO) emissions decreased by about 35% and 12%, respectively, in DFDI RCCI than conventional RCCI combustion. The results indicated that each parameter had an impact on the BTE and emission characteristics of DFDI RCCI, particularly GER and EGR. Abbreviations: aTDC: after Top Dead Center; bTDC: before Top Dead Center; BTE: Brake Thermal Efficiency; CA: Crank Angle; CDC: Conventional Diesel Combustion; CE: Combustion Efficiency; CO: Carbon Monoxide; COV: Coefficient of Variation; DDFS: Dual Direct Fuel Stratifications; DFDI: Dual Fuel Direct Injection; DGI: Double Gasoline Injection; DIP: Diesel Injection Pressure; EGR: Exhaust Gas Recirculation; GDI: Gasoline Direct injection; GER: Gasoline Energy Ratio; GIP: Gasoline Injection Pressure; HC: Hydrocarbon; HCCI: Homogeneous Charge Compression Ignition; HR: High reactivity; IMEP: Indicated Mean Effective Pressure; ITE: Indicated Thermal Efficiency; LTC: Low-Temperature Combustion; LR: Low reactivity; NO: Nitric Oxide; NOx: Oxides of Nitrogen; PCCI: Premixed Charge Compression Ignition; PFI: Port Fuel Injection; PPCI: Partial Premixed Charge Ignition; RCCI: Reactivity Controlled Compression Ignition; RoHR: Rate of Heat Release; RoPR: Rate of Pressure Rise; SGI: Single Gasoline Injection; SOI-1: HRF first pulse start angle; SOI-1mass:HRF first pulse mass quantity; SOI-2: HRF Second pulse start angle

Combustion Mode Design with High Efficiency and Low Emissions Controlled by Mixtures Stratification and Fuel Reactivity

This paper presents a review on the combustion mode design with high efficiency and low emissions controlled by fuel reactivity and mixture stratification that have been conducted in the authors’ group, including the charge reactivity controlled homogeneous charge compression ignition (HCCI) combustion, stratification controlled premixed charge compression ignition (PCCI) combustion, and dual-fuel combustion concepts controlled by both fuel reactivity and mixture stratification. The review starts with the charge reactivity controlled HCCI combustion, and the works on HCCI fuelled with both high cetane number fuels, such as DME and n-heptane, and high octane number fuels, such as methanol, natural gas, gasoline and mixtures of gasoline/alcohols, are reviewed and discussed. Since single fuel cannot meet the reactivity requirements under different loads to control the combustion process, the studies related to concentration stratification and dual-fuel charge reactivity controlled HCCI combustion are then presented, which have been shown to have the potential to achieve effective combustion control. The efforts of using both mixture and thermal stratifications to achieve the auto-ignition and combustion control are also discussed. Thereafter, both charge reactivity and mixture stratification are then applied to control the combustion process. The potential and capability of thermal-atmosphere controlled compound combustion mode and dual-fuel reactivity controlled compression ignition (RCCI)/highly premixed charge combustion (HPCC) mode to achieve clean and high efficiency combustion are then presented and discussed. Based on these results and discussions, combustion mode design with high efficiency and low emissions controlled by fuel reactivity and mixtures stratification in the whole operating range is proposed.

An Experimental and Numerical Study on the Effects of Fuel Properties on the Combustion and Emissions of Low-Temperature Combustion Diesel Engines

Experimental and numerical investigations on the effects of fuel properties on combustion and soot emissions under both conventional and premixed low-temperature combustion (LTC) conditions have been conducted. Three different fuels, diesel, gasoline, and n-butanol, were used to formulate five fuels with different fuel properties. Computational fluid dynamic (CFD) simulations were conducted to predict the combustion processes and soot emissions of the various fuels. The results show that under both conventional and premixed combustion conditions, the cetane number (CN) has the dominant effect on the ignition delay; the volatility, aromatic, and oxygen contents only have a minor influence on ignition delay. High CN fuels need much higher exhaust gas recirculation (EGR) to provide a sufficiently long ignition delay compared to the fuels with lower CN. As a result, the carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions of the high CN fuels are higher than the low CN fuels due to the lower intake oxygen concentrations. The volatility can be important under high, mixing-controlled, conventional combustion conditions, and the high volatility and oxygen content are also beneficial for CO and UHC reduction under high EGR premixed LTC conditions. The CN plays a dominant role in soot emissions, followed by the oxygen content and the volatility under low oxygen concentration conditions. The experiments show that the trade-off between NOx and soot can be totally eliminated by optimizing the diesel/gasoline/butanol blended fuel. A reduced primary reference fuel (PRF)-n-butanol-polycyclic aromatic hydrocarbon (PAH) mechanism was formulated to predict the combustion and soot emissions of the tested fuels, and the effects of fuel chemistry properties on the combustion processes and soot emissions were well predicted. The simulation results show that the mixing process can be greatly improved by adjusting the fuel chemistry properties, which leads to improved combustion and low soot emissions.

Experimental Study on Emission Characteristics of HCCI Operation with N-Heptane

Homogeneous Charge Compression Ignition (HCCI) is a new combustion mode with higher thermal efficiency and lower emission. With the recent development of experimental and theoretical investigations, HCCI operation for high cetane number fuels has attracted more attention. As a reference fuel, n-heptane is very easy to be ignited for high cetane number and shows obviously two-stage heat release in homogeneous charge compression ignition process due to chemical properties. HC, CO and NOx emissions of n-heptane HCCI combustion with intake temperature and excess air coefficient are studied in this paper. Intake temperature and excess air coefficient have a great impact on HCCI combustion and provide important approaches to widen HCCI operating range.

Controlling Soot Formation with Filtered EGR for Diesel and Biodiesel Fuelled Engines

Although exhaust gas recirculation (EGR) is an effective strategy for controlling the levels of nitrogen oxides (NO(X)) emitted from a diesel engine, the full potential of EGR in NO(X)/PM trade-off and engine performance (i.e., fuel economy) has not fully been exploited. Significant work into the cause and control of particulate matter (PM) has been made over the past decade with new cleaner fuels and after-treatment devices emerging to comply with the current and forthcoming emission regulations. In earlier work, we demonstrated that engine operation with oxygenated fuels (e.g., biodiesel) reduces the PM emissions and extends the engine tolerance to EGR before it reaches smoke-limited conditions. The same result has also been reported when high cetane number fuels such as gas-to-liquid (GTL) are used. To further our understanding of the relationship between EGR and PM formation, a diesel particulate filter (DPF) was integrated into the EGR loop to filter the recirculated soot particulates. The control of the soot recirculation penalty through filtered EGR (FEGR) resulted in a 50% engine-out soot reduction, thus showing the possibility of extending the maximum EGR limit or being able to run at the same level of EGR with an improved NO(X)/soot trade-off.

Fuel Property Effects on PCCI Combustion in a Heavy-Duty Diesel Engine

An experimental study was performed to investigate fuel property effects on premixed charge compression ignition (PCCI) combustion in a heavy-duty diesel engine. A matrix of research diesel fuels designed by the Coordinating Research Council, referred to as the Fuels for Advanced Combustion Engines (FACE), was used. The fuel matrix design covers a wide range of cetane numbers (30 to 55), 90% distillation temperatures (270 to 340 °C) and aromatics content (20 to 45%). The fuels were tested in a single-cylinder Caterpillar diesel engine equipped with a common-rail fuel injection system. The engine was operated at 900 rpm, a relative air/fuel ratio of 1.2 and 60% exhaust gas recirculation (EGR) for all fuels. The study was limited to a single fuel injection event starting between −30° and 0 °CA after top dead center (aTDC) with a rail pressure of 150 MPa. The brake mean effective pressure (BMEP) ranged from 2.6 to 3.1 bar depending on the fuel and its injection timing. The experimental results show that cetane number was the most important fuel property affecting PCCI combustion behavior. The low cetane number fuels had better brake specific fuel consumption (BSFC) due to more optimized combustion phasing and shorter combustion duration. They also had a longer ignition delay period available for premixing, which led to near-zero soot emissions. The two fuels with high cetane number and high 90% distillation temperature produced significant soot emissions. The two fuels with high cetane number and high aromatics produced the highest brake specific NOx emissions, although the absolute values were below 0.1 g/kW-h. Brake specific HC and CO emissions were primarily a function of the combustion phasing, but the low cetane number fuels had slightly higher HC and lower CO emissions than the high cetane number fuels.

저온디젤연소에서 고세탄가 연료의 방향족 및 T90 온도가 배기가스에 미치는 영향

1.9L 커먼레일 직접분사 디젤 엔진을 이용하여 1500rpm 2.6bar BMEP 에서 다량의 EGR(약 41%)과 연료분사 제어를 통한 저온디젤연소 영역에서 연료의 특성이 연소와 배기가스에 미치는 영향을 분석하였다. 사용한 연료는 세탄가 55 에 대하여 방향족 성분(20%, 45%, vol. %)과 T90 온도(270℃, 340℃)의 조합으로 네 개이다. 주어진 실험 조건에서 모든 연료에 대하여 착화지연 기간이 증가함에 따라 PM 은 단조적으로 저감되었다. 동일한 착화지연 기간에 대하여 T90 온도가 높은 연료들의 PM 발생이 높았다. NOx 는 동일한 MFB50% 위치에서 모든 연료가 동등 수준이었다. THC, CO 발생은 연료 조성에 관계없이 동일한 착화지연 기간에 대하여 동등 수준이었다. 또한 착화지연 기간 증가에 따라 THC, CO 배출이 증가하였는데 이는 과혼합 증가가 주 원인으로 판단된다.

The effect of fuel properties on exhaust emissions from diesel passenger car

The effect of diesel fuel sulphur content and cetane number on regulated emissions was investigated in a Euro III diesel passenger car. Experimental results indicated that fuel sulphur level had a significant impact on all regulated emission, especially on PM. Testing fuels of different ignition qualities showed that HC and CO emissions of high cetane number fuels were significantly lower than emissions of a low cetane number fuel. We also observed a little decrease in NOx emissions with an increase in the cetane number.

A fundamental study on the control of the HCCI combustion and emissions by fuel design concept combined with controllable EGR. Part 2. Effect of operating conditions and EGR on HCCI combustion

In Part 1, the effects of octane number of primary reference fuels and equivalence ration on combustion characteristics of a single-cylinder HCCI engine were studied. In this part, the influence of exhaust gas recirculation (EGR) rate, intake charge temperature, coolant temperature, and engine speed on the HCCI combustion characteristics and its emissions were evaluated. The experimental results indicate that the ignition timing of the first-stage combustion and second-stage combustion retard, and the combustion duration prolongs with the introduction of cooled EGR. At the same time, the HCCI combustion using high cetane number fuels can tolerate with a higher EGR rate, but only 45% EGR rate for RON75 at 1800 rpm. Furthermore, there is a moderate effect of EGR rate on CO and UHC emissions for HCCI combustion engines fueled with n-heptane and RON25, but a distinct effect on emissions for higher octane number fuels. Moreover, the combustion phase advances, and the combustion duration shorten with the increase of intake charge temperature and the coolant out temperature, and the decrease of the engine speed. At last, it can be found that the intake charge temperature gives the most sensitive influence on the HCCI combustion characteristics.

Alaska North Slope crude oil price and the behavior of diesel prices in California

This paper first of all summarized the auto-ignition mechanism of high cetane and high octane number fuels from the aspect of chemical reaction kinetics with the main purpose of explaining different auto-ignition characteristics of the two kinds of fuel and providing a classification of fuels with the same ignition principles. High cetane number fuels cover major real compression-ignition internal combustion engine fuels and references fuels in use, including straight-chain alkanes, straight-chain ethers, straight-chain esters and cetane number improvers while high octane number fuels cover major real spark-ignition internal combustion engine fuels and references fuels in use, including hydrogen, carbon monoxide, small molecular alkanes, small molecular ethanol, branched alkanes, cycloalkanes, light olefins, simple aromatic hydrocarbons and gasoline antiknock branched ethers. On this basis, 8 representative high octane number fuels were selected for mixing with the high cetane number fuel n-heptane to study the ignition characteristics of mixed fuels in order to find mechanism and corresponding rules.

Gas sampling analysis of combustion processes in a homogeneous charge compression ignition engine

In-cylinder gas sampling experiments were conducted to clarify the chemical reaction processes of homogeneous charge compression ignition (HCCI) combustion. To study the differences in ignition processes by the ignitability of fuels, three kinds of straight-chain saturated hydrocarbons, such as n-pentane, n-hexane and n-heptane, were used as the fuels. Also, to study specific differences in the ignition processes between a single-component fuel and a dual-component fuel, n-pentane was used as the single-component fuel and n-hexane and ethylene, with compositions adjusted in order to have the same ignitability as n-pentane, were used as the dual-component fuel. The results show that the chemical processes in the low-temperature oxidation range, from 700 to 900 K, need to be controlled for the ignition timing control of HCCI combustion. Controlling ignition timing by dual fuel means controlling the oxidation starting time by the ignitability of a high cetane number fuel and controlling the low-temperature oxidation rate by varying the composition of the high and low cetane number fuels.