EGR Oxidation and Catalytic Fuel Reforming for Diesel Engines

2008 ◽  
Author(s):  
Usman Asad ◽  
Ming Zheng
Keyword(s):  
Soot Formation ◽  
Preliminary Investigation ◽  
Low Temperature Combustion ◽  
Operating Characteristics ◽  
Water Addition ◽  
Fuel Reforming ◽  
Treatment Techniques ◽  
Temperature Combustion ◽  
Cyclic Variations ◽  
Engine Emission

Exhaust gas recirculation (EGR) treatment techniques that include combustible substance oxidation, catalytic fuel reforming, and partial bypass-flow control have been experimentally investigated on a single cylinder diesel engine. Application tests are conducted to investigate the effects of the reformed gases on the diesel combustion characteristics and exhaust emissions. This research is aimed at stabilizing and expanding the limits of heavy EGR during steady and transient operations by enhancing the premixed combustion that may significantly alleviate problems with soot formation and cyclic variations. Additionally, the heavy treated EGR is applied to enable in-cylinder low temperature combustion. A preliminary investigation on the effects of water addition to the high temperature catalyst bed is also conducted. The potential of EGR reforming is also examined for possible generation of synthetic EGR (CO2) at low engine loads. The effectiveness of the treated EGR on engine emission and operating characteristics are therefore reported.

Modeling Soot Formation Using Reduced PAH Chemistry in n-Heptane Lifted Flames With Application to Low Temperature Combustion

2008 ◽  
Author(s):  
Gokul Vishwanathan ◽  
Rolf D. Reitz
Keyword(s):  
Low Temperature ◽  
Soot Formation ◽  
Numerical Study ◽  
Low Temperature Combustion ◽  
Constant Volume Chamber ◽  
Soot Mass ◽  
Temperature Combustion ◽  
Lifted Flames ◽  
Polycyclic Aromatic ◽  
Species Comparisons

A numerical study of in-cylinder soot formation and oxidation processes in n-heptane lifted flames using various soot inception species has been conducted. In a recent study by the authors, it was found that the soot formation and growth regions in lifted flames were not adequately represented by using acetylene alone as the soot inception species. Comparisons with a conceptual model and available experimental data suggested that the location of soot formation regions could be better represented if polycyclic aromatic hydrocarbon (PAH) species were considered as alternatives to acetylene for soot formation processes. Since the local temperatures are much lower under low temperature combustion (LTC) conditions, it is believed that significant soot mass contribution can be attributed to PAH rather than to acetylene. To quantify and validate the above observations, a reduced n-heptane chemistry mechanism has been extended to include PAH species up to four fused aromatic rings (pyrene). The resulting chemistry mechanism was integrated into the multidimensional CFD code KIVA-CHEMKIN for modeling soot formation in lifted flames in a constant volume chamber. The investigation revealed that a simpler model that only considers up to phenanthrene (three fused rings) as the soot inception species has good possibilities for better soot location predictions. The present work highlights and illustrates the various research challenges toward accurate qualitative and quantitative predictions of soot for new low emission combustion strategies for I.C. engines.

Application of Dynamic ϕ–T Map: Analysis on a Natural Gas/Diesel Fueled RCCI Engine

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Jing Li ◽  
Wenming Yang ◽  
Hui An ◽  
Dezhi Zhou ◽  
Markus Kraft
Keyword(s):  
Natural Gas ◽  
Soot Formation ◽  
Combustion Process ◽  
Diesel Oil ◽  
Chemical Mechanism ◽  
Low Temperature Combustion ◽  
Injection Duration ◽  
Start Of Injection ◽  
Temperature Combustion ◽  
Map Analysis

In this study, dynamic ϕ–T map analysis was applied to a reactivity controlled compression ignition (RCCI) engine fueled with natural gas (NG) and diesel. The combustion process of the engine was simulated by coupled kiva4-chemkin with a diesel oil surrogate (DOS) chemical mechanism. The ϕ–T maps were constructed by the mole fractions of soot and NO obtained from senkin and ϕ–T conditions from engine simulations. Five parameters, namely, NG fraction, first start of injection (SOI) timing, second SOI timing, second injection duration, and exhaust gas recirculation (EGR) rate, were varied in certain ranges individually, and the ϕ–T maps were compared and analyzed under various conditions. The results revealed how the five parameters would shift the ϕ–T conditions and influence the soot–NO contour. Among the factors, EGR rate could limit the highest temperature due to its dilute effect, hence maintaining RCCI combustion within low-temperature combustion (LTC) region. The second significant parameter is the premixed NG fraction. It could set the lowest temperature; moreover, the tendency of soot formation can be mitigated due to the lessened fuel impingement and the absence of C–C bond. Finally, the region of RCCI combustion was added to the commonly known ϕ–T map diagram.

The role of the diffusion-limited injection in direct dual fuel stratification

2016 ◽  
Vol 18 (4) ◽  
pp. 351-365 ◽  
Author(s):  
Martin Wissink ◽  
Rolf Reitz
Keyword(s):  
Low Temperature ◽  
Heat Release ◽  
Thermal Efficiency ◽  
Soot Formation ◽  
Combustion Stability ◽  
Dual Fuel ◽  
Low Temperature Combustion ◽  
Fuel Stratification ◽  
Diffusion Limited ◽  
Temperature Combustion

Low-temperature combustion offers an attractive combination of high thermal efficiency and low NO x and soot formation at moderate engine load. However, the kinetically-controlled nature of low-temperature combustion yields little authority over the rate of heat release, resulting in a tradeoff between load, noise, and thermal efficiency. While several single-fuel strategies have achieved full-load operation through the use of equivalence ratio stratification, they uniformly require retarded combustion phasing to maintain reasonable noise levels, which comes at the expense of thermal efficiency and combustion stability. Previous work has shown that control over heat release can be greatly improved by combining reactivity stratification in the premixed charge with a diffusion-limited injection that occurs after low-temperature heat release, in a strategy called direct dual fuel stratification. While the previous work has shown how the heat release control offered by direct dual fuel stratification differs from other strategies and how it is enabled by the reactivity stratification created by using two fuels, this paper investigates the effects of the diffusion-limited injection. In particular, the influence of fuel selection and the pressure, timing, and duration of the diffusion-limited injection are examined. Diffusion-limited injection fuel type had a large impact on soot formation, but no appreciable effect on performance or other emissions. Increasing injection pressure was observed to decrease filter smoke number exponentially while improving combustion efficiency. The timing and duration of the diffusion-limited injection offered precise control over the heat release event, but the operating space was limited by a tradeoff between NO x and soot.

An Experimental Investigation on the Effect of Post-Injection Strategies on Combustion and Emissions in the Low-Temperature Diesel Combustion Regime

2005 ◽  
Vol 129 (1) ◽  
pp. 279-286 ◽  
Author(s):  
Hanho Yun ◽  
Rolf D. Reitz
Keyword(s):  
Low Temperature ◽  
Soot Formation ◽  
Combustion Regime ◽  
Nox Emissions ◽  
Diesel Combustion ◽  
Low Temperature Combustion ◽  
Post Injection ◽  
Temperature Combustion ◽  
Soot Emissions ◽  
Injection Strategies

In order to meet future emissions regulations, new combustion concepts are being developed. Among them, the development of low-temperature diesel combustion systems has received considerable attention. Low NOx emissions are achieved through minimization of peak temperatures during the combustion process. Concurrently, soot formation is inhibited due to a combination of low combustion temperatures and extensive fuel-air premixing. In this study, the effect of late-cycle mixing enhancement by post-injection strategies on combustion and engine-out emissions in the low-temperature (low soot and NOx emissions) combustion regime was experimentally investigated. The baseline operating condition considered for low-temperature combustion was 1500rpm, 3bar IMEP with 50% EGR rate, and extension to high loads was considered by means of post injection. Post-injection strategies gave very favorable emission results in the low-temperature combustion regime at all loads tested in this study. Since post injection leads to late-cycle mixing improvement, further reductions in soot emissions were achieved without deteriorating the NOx emissions. With smaller fuel injected amounts for the second pulse, better soot emissions were found. However, the determination of the dwell between the injections was found to be very important for the emissions.

An Experimental and Numerical Investigation on the Effect of Post Injection Strategies on Combustion and Emissions in the Low-Temperature Diesel Combustion Regime

2005 ◽  
Author(s):  
Hanho Yun ◽  
Yong Sun ◽  
Rolf D. Reitz
Keyword(s):  
Low Temperature ◽  
Soot Formation ◽  
Combustion Regime ◽  
Nox Emissions ◽  
Diesel Combustion ◽  
Low Temperature Combustion ◽  
Post Injection ◽  
Temperature Combustion ◽  
Soot Emissions ◽  
Injection Strategies

In order to meet future emissions regulations, new combustion concepts are being developed. Among them, the development of low-temperature diesel combustion systems has received considerable attention. Low NOx emissions are achieved through minimization of peak temperatures occurring during the combustion process. Concurrently, soot formation is inhibited due to a combination of low combustion temperatures and extensive fuel-air pre-mixing. In this study, the effect of late-cycle mixing enhancement by post injection strategies on combustion and engine-out emissions in the low-temperature combustion regime was investigated experimentally and numerically. The baseline operating condition considered for low-temperature combustion was 1500 rev/min, 3bar IMEP with 50% EGR rate, and extension to high loads was considered by means of post injection. Post injection strategies gave very favorable emission results in the low temperature combustion regime at all loads. With small second fuel injected amounts, better soot emissions were found. However, the determination of the dwell between the injections was found to be very important for the emissions. Since post injection leads to late-cycle mixing improvement, further reductions in soot emissions were achieved without deteriorating the NOx emissions. To explain these results, numerical analysis was also done using the KIVA-CHEMKIN code. The simulations show that optimal combustion requires that the post injection fuel avoid fuel rich regions formed from the main injection.

Modeling Soot Formation Using Reduced Polycyclic Aromatic Hydrocarbon Chemistry in n-Heptane Lifted Flames With Application to Low Temperature Combustion

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Gokul Vishwanathan ◽  
Rolf D. Reitz
Keyword(s):  
Low Temperature ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Internal Combustion Engines ◽  
Soot Formation ◽  
Numerical Study ◽  
Low Temperature Combustion ◽  
Temperature Combustion ◽  
Lifted Flames ◽  
Polycyclic Aromatic

A numerical study of in-cylinder soot formation and oxidation processes in n-heptane lifted flames using various soot inception species has been conducted. In a recent study by the authors, it was found that the soot formation and growth regions in lifted flames were not adequately represented by using acetylene alone as the soot inception species. Comparisons with a conceptual model and available experimental data suggested that the location of soot formation regions could be better represented if polycyclic aromatic hydrocarbon (PAH) species were considered as alternatives to acetylene for soot formation processes. Since the local temperatures are much lower under low temperature combustion conditions, it is believed that significant soot mass contribution can be attributed to PAH rather than to acetylene. To quantify and validate the above observations, a reduced n-heptane chemistry mechanism has been extended to include PAH species up to four fused aromatic rings (pyrene). The resulting chemistry mechanism was integrated into the multidimensional computational fluid dynamics code KIVA-CHEMKIN for modeling soot formation in lifted flames in a constant volume chamber. The investigation revealed that a simpler model that only considers up to phenanthrene (three fused rings) as the soot inception species has good possibilities for better soot location predictions. The present work highlights and illustrates the various research challenges toward accurate qualitative and quantitative predictions of the soot for new low emission combustion strategies for internal combustion engines.

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