scholarly journals Isolating the effects of reactivity stratification in reactivity-controlled compression ignition with iso-octane and n-heptane on a light-duty multi-cylinder engine

2017 ◽  
Vol 19 (9) ◽  
pp. 907-926 ◽  
Author(s):  
Martin L Wissink ◽  
Scott J Curran ◽  
Greg Roberts ◽  
Mark PB Musculus ◽  
Christine Mounaïm-Rousselle
Keyword(s):  
High Efficiency ◽  
Direct Injection ◽  
Combustion Process ◽  
High Reactivity ◽  
Low Temperature Combustion ◽  
Compression Ignition ◽  
Reactivity Controlled Compression Ignition ◽  
Fundamental Understanding ◽  
Primary Reference ◽  
Primary Reference Fuels

Reactivity-controlled compression ignition (RCCI) is a dual-fuel variant of low-temperature combustion that uses in-cylinder fuel stratification to control the rate of reactions occurring during combustion. Using fuels of varying reactivity (autoignition propensity), gradients of reactivity can be established within the charge, allowing for control over combustion phasing and duration for high efficiency while achieving low NOx and soot emissions. In practice, this is typically accomplished by premixing a low-reactivity fuel, such as gasoline, with early port or direct injection, and by direct injecting a high-reactivity fuel, such as diesel, at an intermediate timing before top dead center. Both the relative quantity and the timing of the injection(s) of high-reactivity fuel can be used to tailor the combustion process and thereby the efficiency and emissions under RCCI. While many combinations of high- and low-reactivity fuels have been successfully demonstrated to enable RCCI, there is a lack of fundamental understanding of what properties, chemical or physical, are most important or desirable for extending operation to both lower and higher loads and reducing emissions of unreacted fuel and CO. This is partly due to the fact that important variables such as temperature, equivalence ratio, and reactivity change simultaneously in both a local and a global sense with changes in the injection of the high-reactivity fuel. This study uses primary reference fuels iso-octane and n-heptane, which have similar physical properties but much different autoignition properties, to create both external and in-cylinder fuel blends that allow for the effects of reactivity stratification to be isolated and quantified. This study is part of a collaborative effort with researchers at Sandia National Laboratories who are investigating the same fuels and conditions of interest in an optical engine. This collaboration aims to improve our fundamental understanding of what fuel properties are required to further develop advanced combustion modes.

An integrated effort of medium reactivity fuel, in-cylinder, and after-treatment strategies to demonstrate potential reduction in challenging emissions of reactivity controlled compression ignition combustion

2019 ◽  
Vol 234 (5) ◽  
pp. 1260-1278
Author(s):  
R Murugan ◽  
D Ganesh ◽  
G Nagarajan
Keyword(s):  
Carbon Monoxide ◽  
Direct Injection ◽  
Cetane Number ◽  
Combustion Process ◽  
Oxidation Catalyst ◽  
Compression Ignition ◽  
Reactivity Controlled Compression Ignition ◽  
Potential Reduction ◽  
Carbon Monoxide Emission ◽  
Compression Ignition Combustion

Previous studies on reactivity controlled compression ignition combustion indicated that, reducing the hydrocarbon and carbon monoxide emissions at low load conditions still remains a challenge because of lower in-cylinder temperatures due to lower global reactivity gradient and reduced oxidation process. Research in this direction has not been reported so far and with this motivation, an attempt has been made to increase the global reactivity gradient and oxidation of fuel–air mixture by converting the low reactivity fuel methanol into medium reactivity fuel. This is achieved by mixing high octane oxygenated fuel, methanol (Octane Number: 110), with an oxygenated better cetane and volatility fuels like polyoxymethylene dimethyl ether (Cetane Number: 78) and isobutanol (Cetane Number: 15). The medium reactivity fuel with multiple direct injection of diesel fuel timed the combustion of dual fuel–air mixture to avoid too late or too advanced combustion which are the prime factors in controlling the unburnt emissions in a low temperature combustion process. Four medium reactivity fuel samples, M80IB20, M60IB40, M90P10, and M80P20, on percentage volume basis have been prepared and tested on the modified on-road three-cylinder turbocharged common rail direct injection diesel engine to demonstrate higher indicated thermal efficiency and potential reduction in unburnt and oxides of nitrogen/particulate matter emissions from reactivity controlled compression ignition combustion. Experimental results show that, use of medium reactivity fuel with optimized diesel injection strategy resulted in 66% decrease in hydrocarbon emission and 74% decrease in carbon monoxide emission by enhancing the oxidation of fuel–air mixture at lower temperatures which is evidently noticed in the combustion characteristics. Further reduction in hydrocarbon and carbon monoxide emission of about 90% has been achieved by integrating the diesel oxidation catalyst with the engine.

Reactivity Controlled Compression Ignition Using Premixed Hydrated Ethanol and Direct Injection Diesel

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Adam B. Dempsey ◽  
Bishwadipa Das Adhikary ◽  
Sandeep Viswanathan ◽  
Rolf D. Reitz
Keyword(s):  
Direct Injection ◽  
Fuel Efficiency ◽  
High Reactivity ◽  
Water Mixture ◽  
Compression Ignition ◽  
Load Range ◽  
Reactivity Controlled Compression Ignition ◽  
Hcci Combustion ◽  
Heavy Duty Diesel Engine ◽  
Heavy Duty Diesel

The present study uses numerical simulations to explore the use of hydrated (wet) ethanol for reactivity controlled compression ignition (RCCI) operation in a heavy duty diesel engine. RCCI uses in-cylinder blending of a low reactivity fuel with a high reactivity fuel and has demonstrated significant fuel efficiency and emissions benefits using a variety of fuels, including gasoline and diesel. Combustion timing is controlled by the local blended fuel reactivity (i.e., octane number), and the combustion duration can be controlled by establishing optimized gradients in fuel reactivity in the combustion chamber. In the present study, the low reactivity fuel was hydrated ethanol while the higher reactivity fuel was diesel. First, the effect of water on ethanol/water/diesel mixtures in completely premixed HCCI combustion was investigated using GT-Power and single-zone CHEMKIN simulations. The results showed that the main impact of the water in the ethanol is to reduce the initial in-cylinder temperature due to vaporization cooling. Next, multi-dimensional engine modeling was performed using the KIVA code at engine loads from 5 to 17 bars IMEP at 1300 rev/min with various grades of hydrated ethanol and a fixed diesel fraction of the total fuel. The results show that hydrated ethanol can be used in RCCI combustion with gross indicated thermal efficiencies up to 55% and very low emissions. A 70/30 ethanol/water mixture (by mass) was found to yield the best results across the entire load range without the need for EGR.

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

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Jihad A. Badra ◽  
Jaeheon Sim ◽  
Ahmed Elwardany ◽  
Mohammed Jaasim ◽  
Yoann Viollet ◽  
...  
Keyword(s):  
Experimental Data ◽  
High Efficiency ◽  
Direct Injection ◽  
Compression Ignition ◽  
Hollow Cone ◽  
Direct Injection Engine ◽  
Technical Paper ◽  
Primary Reference ◽  
Partially Premixed ◽  
Compression Ignition Combustion

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.

Reactivity Controlled Compression Ignition (RCCI) Using Premixed Hydrated Ethanol and Direct Injection Diesel

2011 ◽  
Author(s):  
A. B. Dempsey ◽  
B. Das Adhikary ◽  
S. Viswanathan ◽  
R. D. Reitz
Keyword(s):  
Direct Injection ◽  
Fuel Efficiency ◽  
High Reactivity ◽  
Net Energy ◽  
Water Mixture ◽  
Compression Ignition ◽  
Load Range ◽  
Pure Ethanol ◽  
Reactivity Controlled Compression Ignition ◽  
Heavy Duty Diesel

Previous research has shown that a Homogeneous Charge Compression Ignition (HCCI) engine with efficient heat recovery can operate on a 35 to 65% volumetric mixture of ethanol-in-water while achieving high brake thermal efficiency (∼39%) and very low NOx emissions [4]. The major advantage of utilizing hydrated ethanol as a fuel is that the net energy gain improves from 21 to 55% of the heating value of ethanol and its co-products, since significant energy must be expended to remove water during production. This is required because wet ethanol is not suitable for conventional combustion engines. For example, spark ignition engines demand the use of pure ethanol because the dilution caused by water reduces the flame speed, resulting in misfire and problems due to condensation. The present study uses numerical simulations to explore the use of wet ethanol for Reactivity Controlled Compression Ignition (RCCI) operation in a heavy duty diesel engine. RCCI uses in-cylinder blending of a low reactivity fuel with a high reactivity fuel and has demonstrated significant fuel efficiency and emissions benefits using a variety of fuels, including gasoline and diesel. Combustion timing is controlled by the local blended fuel reactivity (i.e. octane number), and the combustion duration can be controlled by establishing optimized gradients in fuel reactivity in the combustion chamber. In the present study, the low reactivity fuel was hydrated ethanol while the higher reactivity fuel was diesel. First, the effect of water on ethanol/water/diesel HCCI was investigated using GT-Power and single-zone CHEMKIN simulations. The results showed that the main impact of the water in the ethanol is to reduce the IVC temperature due to vaporization cooling. Next, multidimensional engine modeling was performed using the KIVA code at engine loads from 5 to 17 bar IMEP at 1300 rev/min with various grades of hydrated ethanol and a fixed diesel fraction of the total fuel. The results show that hydrated ethanol can be used in a RCCI engine with gross indicated thermal efficiencies up to 55% and very low emissions. A 70/30 ethanol/water mixture (by mass) was found to yield the best results across the entire load range without the need for EGR.

Reactivity Controlled Compression Ignition Performance With Renewable Fuels

2012 ◽  
Author(s):  
Scott J. Curran ◽  
James P. Szybist ◽  
Robert M. Wagner
Keyword(s):  
High Efficiency ◽  
Fuel Injection ◽  
Combustion Process ◽  
Renewable Fuels ◽  
Compression Ignition ◽  
Reactivity Controlled Compression Ignition ◽  
Engine Efficiency ◽  
Fuel Charge ◽  
Performance And Emissions ◽  
Ethanol Blends

Reactivity controlled compression ignition (RCCI) combustion makes use of in-cylinder blending of two fuels with differing reactivity to tailor the reactivity of the fuel charge for improved control of the combustion process. This approach has been shown in simulations and engine experiments to have the potential for high efficiency with very low NOX and particulate matter (PM) emissions. Previous multi-cylinder RCCI experiments have been completed to understand the potential of this approach under more real-world conditions in a light-duty multi-cylinder engine (MCE) with production viable hardware. MCE experiments explored fuel injection strategy, dilution levels, piston geometry (including compression ratio), and fuel properties. Many renewable fuels have unique properties which enable expanded operation of advanced combustion methods for higher engine efficiency and lower energy requirements for emissions control devices. This study investigates the effect that renewable gasoline and diesel fuel replacements have on the load-expansion of RCCI, performance and emissions. The study focuses on ethanol blends for replacement of gasoline as the port-injected fuel (PFI) and biodiesel blends as the replacement for the direct injected (DI) fuel.

Coordination of fuel reactivity and injection timing to achieve highly efficient and stable gasoline compression ignition combustion in a wide load range

2020 ◽  
Vol 234 (7) ◽  
pp. 1840-1853
Author(s):  
Chenxu Jiang ◽  
Zilong Li ◽  
Guibin Liu ◽  
Yong Qian ◽  
Xingcai Lu
Keyword(s):  
High Efficiency ◽  
Pressure Rise ◽  
Injection Timing ◽  
Compression Ignition ◽  
Load Range ◽  
Start Of Injection ◽  
Rise Rate ◽  
Primary Reference ◽  
Primary Reference Fuels ◽  
Compression Ignition Combustion

Gasoline compression ignition combustion is a new combustion mode with great development potential and is highly influenced by fuel reactivity and injection strategy. This paper coordinates the fuel octane number and single-injection timing to operate gasoline compression ignition combustion with high efficiency in a wide load range, with the speed fixed at 1500 r/min. The primary reference fuels with octane numbers 60, 70, 80, and 90 were used, labeled as PRF60, PRF70, PRF80, and PRF90, respectively. The results proved that under steady-state conditions where the speed and load changed slightly, taking the fuel economy and combustion and emission performance into account, PRF60 and PRF70 should be applied at a load lower than 2 bar and 2–8 bar, respectively, and the start of injection timing should be set at 13 °CA before top dead center. When the load is higher than 8 bar, PRF90 should be applied at the start of injection timing of 11 °CA before top dead center. It is noteworthy that PRF70 under medium-load conditions could achieve the indicated thermal efficiency of up to 47%. The injection timing of PRF90 was limited to 9–1711 °CA before top dead center due to the limit of the peak value of pressure rise rate, whereas PRF60 had a wider injection timing boundary than PRF90.

Computational optimization of reactivity controlled compression ignition combustion to achieve high efficiency and clean combustion

2020 ◽  
pp. 146808742093173 ◽  
Author(s):  
Avilash Jain ◽  
Anand Krishnasamy ◽  
Pradeep V
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Fuel Injection ◽  
Direct Injection ◽  
Network Models ◽  
Compression Ignition ◽  
Neural Network Models ◽  
Reactivity Controlled Compression Ignition ◽  
Artificial Neural ◽  
Artificial Neural Network Models

One of the major limitations of reactivity controlled compression ignition is higher unburned hydrocarbon and carbon monoxide emissions and lower thermal efficiency at part load operating conditions. In the present study, a combined numerical approach using a commercial three-dimensional computational fluid dynamics code CONVERGE along with artificial neural network and genetic algorithm is presented to address the above limitation. A production light-duty diesel engine is modified to run in reactivity controlled compression ignition by replacing an existing mechanical fuel injection system with a flexible electronic port fuel injection and common rail direct injection systems. The injection schedules of port fuel injection and direct injection injectors are controlled using National Instruments port and direct injection driver modules. Upon validation of combustion and emission parameters, parametric investigations are carried out to establish the effects of direct-injected diesel fuel timing start of injection (SOI), premixed fuel ratio and intake charge temperature on the engine performance and emissions in reactivity controlled compression ignition. The results obtained show that the start of injection timing and intake charge temperature significantly influence combustion phasing, while the premixed fuel ratio controls mixture reactivity and combustion quality. By utilizing the data generated with the validated computational fluid dynamics models, the artificial neural network models are trained to predict the engine exhaust emissions and efficiency. The artificial neural network models for gross indicated efficiency and oxides of nitrogen (NOx) are then coupled with genetic algorithm to maximize gross indicated efficiency while keeping the NOx and soot emissions within Euro VI emission limits. By optimizing the start of injection timing, premixed fuel ratio and intake charge temperature simultaneously using the artificial neural network models coupled with genetic algorithm, 19% improvement in gross indicated efficiency, 60% and 64% reduction in hydrocarbon and carbon monoxide emissions, respectively, are obtained in reactivity controlled compression ignition compared to the baseline case.

Low Cetane Fuels in Compression Ignition Engine to Achieve LTC

2011 ◽  
Author(s):  
Swami Nathan Subramanian ◽  
Stephen Ciatti
Keyword(s):  
Low Temperature ◽  
Internal Combustion Engines ◽  
High Efficiency ◽  
Fuel Efficiency ◽  
Nox Emissions ◽  
Low Temperature Combustion ◽  
Compression Ignition ◽  
Oxides Of Nitrogen ◽  
Compression Ignition Engine ◽  
Conventional Combustion

The conventional combustion processes of Spark Ignition (SI) and Compression Ignition (CI) have their respective merits and demerits. Internal combustion engines use certain fuels to utilize those conventional combustion technologies. High octane fuels are required to operate the engine in SI mode, while high cetane fuels are preferable for CI mode of operation. Those conventional combustion techniques struggle to meet the current emissions norms while retaining high efficiency. In particular, oxides of nitrogen (NOx) and particulate matter (PM) emissions have limited the utilization of diesel fuel in compression ignition engines, and conventional gasoline operated SI engines are not fuel efficient. Advanced combustion concepts have shown the potential to combine fuel efficiency and improved emissions 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. Variations in injection pressures, injection schemes and Exhaust Gas Recirculation (EGR) are studied with low octane gasoline LTC. Reductions in emissions are a function of combustion phasing and local equivalence ratio. Engine speed, load, EGR quantity, compression ratio and fuel octane number are all factors that influence combustion phasing. Low cetane fuels have shown comparable diesel efficiencies with low NOx emissions at reasonably high power densities.

Diesel Oxidation Catalyst Control of Hydrocarbon Aerosols From Reactivity Controlled Compression Ignition Combustion

2011 ◽  
Author(s):  
Vitaly Y. Prikhodko ◽  
Scott J. Curran ◽  
Teresa L. Barone ◽  
Samuel A. Lewis ◽  
John M. Storey ◽  
...  
Keyword(s):  
Combustion Process ◽  
Diesel Oxidation Catalyst ◽  
Oxidation Catalyst ◽  
Hydrocarbon Emissions ◽  
Compression Ignition ◽  
Reactivity Controlled Compression Ignition ◽  
Diesel Oxidation ◽  
Homogeneous Combustion ◽  
Compression Ignition Combustion ◽  
And Control

Reactivity Controlled Compression Ignition (RCCI) is a novel combustion process that utilizes two fuels with different reactivity to stage and control combustion and enable homogeneous combustion. The technique has been proven experimentally in previous work with diesel and gasoline fuels; low NOx emissions and high efficiencies were observed from RCCI in comparison to conventional combustion. In previous studies on a multi-cylinder engine, particulate matter (PM) emission measurements from RCCI suggested that hydrocarbons were a major component of the PM mass. Further studies were conducted on this multi-cylinder engine platform to characterize the PM emissions in more detail and understand the effect of a diesel oxidation catalyst (DOC) on the hydrocarbon-dominated PM emissions. Results from the study show that the DOC can effectively reduce the hydrocarbon emissions as well as the overall PM from RCCI combustion. The bimodal size distribution of PM from RCCI is altered by the DOC which reduces the smaller mode 10 nm size particles.

Sign in / Sign up

Export Citation Format

Share Document