Effect of Fuelling Control Parameters on Combustion Characteristics of Diesel-Ignited Natural Gas Dual-Fuel Combustion in an Optical Engine

2016 ◽  
Author(s):  
Mahdiar Khosravi ◽  
Jeremy Rochussen ◽  
Jeff Yeo ◽  
Patrick Kirchen ◽  
Gordon McTaggart-Cowan ◽  
...  
Keyword(s):  
Direct Injection ◽  
Injection Pressure ◽  
Fuel Combustion ◽  
Conversion Process ◽  
Dual Fuel ◽  
Pilot Injection ◽  
Fuel Conversion ◽  
Auto Ignition ◽  
Dual Fuel Combustion ◽  
Ci Engines

Its inherent economic and environmental advantages as an internal combustion engine fuel make natural gas (NG) an attractive alternative to diesel fuel as the primary energy source for some compression ignition (CI) engine applications. Diesel pilot-ignition of NG is an attractive fueling strategy as it typically requires minimal modification of existing CI engines. Furthermore, this strategy makes use of the highly developed direct injection (DI) diesel fuel systems already employed on modern CI engines for to control dual-fuel (DF) combustion. Despite the increasing popularity of the dual-fuel NG engine concept, the fundamental understanding of the fuel conversion mechanisms and the impact of the fueling parameters is still incomplete. A conceptual understanding of the relevant physics is necessary for further development of fueling and pilot-ignition strategies to address the shortcomings of dual-fuel combustion, such as low-load emissions and combustion stability. An experimental facility supporting optical diagnostics via a Bowditch piston arrangement in a 2-litre, single-cylinder research engine (Ricardo Proteus) was used in this study to consider the effect of fueling parameters on the fuel conversion process in a dual fuel engine. Fueling was achieved with port injected CH4 and diesel direct injection using a common rail system. Simultaneous, high-speed natural luminosity (NL) and OH* chemiluminescence imaging was used to characterize dual-fuel combustion and the influence of pilot injection pressure (300 bar vs. 1300 bar) and relative diesel-CH4 ratios (pilot ratio, PR), as these have been noted as key operating dual-fuel control metrics. The pilot injection pressure was observed to have a significant impact on the fuel conversion process. At higher pilot injection pressures, the auto-ignition sites were concentrated around the piston bowl periphery and the reaction zone propagated towards the center of the bowl. At lower pilot injection pressures, ignition initiated in the vicinity of the pilot fuel jet structures and resulted in a more heterogeneous fuel conversion process with regions of intense natural luminosity, attributed to particulate matter. An increase in the pilot ratio (i.e., increased diesel fraction) resulted in a more aggressive combustion event, due to a larger fraction of energy released in a premixed auto-ignition event. This was coupled with a decrease in the fraction of the combustion chamber with significant OH* or NL light emission, indicating incomplete fuel conversion in these regions. The insight to the dual-fuel conversion processes presented in this work will be ultimately used to develop dual-fuel injection strategies, as well as provide much needed validation data for modeling efforts.

Mapping the combustion modes of a dual-fuel compression ignition engine

2021 ◽  
pp. 146808742110183
Author(s):  
Jonathan Martin ◽  
André Boehman
Keyword(s):  
Direct Injection ◽  
Fuel Combustion ◽  
Dual Fuel ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Combustion Modes ◽  
Si Engines ◽  
Dual Fuel Combustion ◽  
Soot Emissions ◽  
Ci Engines

Compression-ignition (CI) engines can produce higher thermal efficiency (TE) and thus lower carbon dioxide (CO2) emissions than spark-ignition (SI) engines. Unfortunately, the overall fuel economy of CI engine vehicles is limited by their emissions of nitrogen oxides (NOx) and soot, which must be mitigated with costly, resource- and energy-intensive aftertreatment. NOx and soot could also be mitigated by adding premixed gasoline to complement the conventional, non-premixed direct injection (DI) of diesel fuel in CI engines. Several such “dual-fuel” combustion modes have been introduced in recent years, but these modes are usually studied individually at discrete conditions. This paper introduces a mapping system for dual-fuel CI modes that links together several previously studied modes across a continuous two-dimensional diagram. This system includes the conventional diesel combustion (CDC) and conventional dual-fuel (CDF) modes; the well-explored advanced combustion modes of HCCI, RCCI, PCCI, and PPCI; and a previously discovered but relatively unexplored combustion mode that is herein titled “Piston-split Dual-Fuel Combustion” or PDFC. Tests show that dual-fuel CI engines can simultaneously increase TE and lower NOx and/or soot emissions at high loads through the use of Partial HCCI (PHCCI). At low loads, PHCCI is not possible, but either PDFC or RCCI can be used to further improve NOx and/or soot emissions, albeit at slightly lower TE. These results lead to a “partial dual-fuel” multi-mode strategy of PHCCI at high loads and CDC at low loads, linked together by PDFC. Drive cycle simulations show that this strategy, when tuned to balance NOx and soot reductions, can reduce engine-out CO2 emissions by about 1% while reducing NOx and soot by about 20% each with respect to CDC. This increases emissions of unburnt hydrocarbons (UHC), still in a treatable range (2.0 g/kWh) but five times as high as CDC, requiring changes in aftertreatment strategy.

scholarly journals Analysis of Ignition Behavior in a Turbocharged Direct Injection Dual Fuel Engine Using Propane and Methane as Primary Fuels

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
A. C. Polk ◽  
C. M. Gibson ◽  
N. T. Shoemaker ◽  
K. K. Srinivasan ◽  
S. R. Krishnan
Keyword(s):  
Ignition Delay ◽  
Direct Injection ◽  
Critical Role ◽  
Combustion Process ◽  
Fuel Combustion ◽  
Operating Conditions ◽  
Dual Fuel ◽  
Brake Mean Effective Pressure ◽  
Auto Ignition ◽  
Dual Fuel Combustion

Dual fuel engine combustion utilizes a high-cetane fuel to initiate combustion of a low-cetane fuel. The performance and emissions benefits (low NOx and soot emissions) of dual fuel combustion are well-known. Ignition delay (ID) of the injected high-cetane fuel plays a critical role in quality of the dual fuel combustion process. This paper presents experimental analyses of the ID behavior for diesel-ignited propane and diesel-ignited methane dual fuel combustion. Two sets of experiments were performed at a constant engine speed (1800 rev/min) using a four-cylinder direct injection diesel engine with the stock electronic conversion unit (ECU) and a wastegated turbocharger. First, the effects of fuel–air equivalence ratios (Фpilot ∼ 0.2–0.6 and Фoverall ∼ 0.2–0.9) on IDs were quantified. Second, the effects of gaseous fuel percent energy substitution (PES) and brake mean effective pressure (BMEP) (from 2.5 to 10 bars) on IDs were investigated. With constant Фpilot (>0.5), increasing Фoverall with propane initially decreased ID but eventually led to premature propane auto-ignition; however, the corresponding effects with methane were relatively minor. Cyclic variations in the start of combustion (SOC) increased with increasing Фoverall (at constant Фpilot) more significantly for propane than for methane. With increasing PES at constant BMEP, the ID showed a nonlinear trend (initially increasing and later decreasing) at low BMEPs for propane but a linearly decreasing trend at high BMEPs. For methane, increasing PES only increased IDs at all BMEPs. At low BMEPs, increasing PES led to significantly higher cyclic SOC variations and SOC advancement for both propane and methane. Finally, the engine ignition delay (EID), defined as the separation between the start of injection (SOI) and the location of 50% of the cumulative heat release, was also shown to be a useful metric to understand the influence of ID on dual fuel combustion. Dual fuel ID is profoundly affected by the overall equivalence ratio, pilot fuel quantity, BMEP, and PES. At high equivalence ratios, IDs can be quite short, and beyond a certain limit, can lead to premature auto-igniton of the low-cetane fuel (especially for a reactive fuel like propane). Therefore, it is important to quantify dual fuel ID behavior over a range of engine operating conditions.

Numerical Investigation of the Performance of a High Pressure Direct Injection (HPDI) Natural Gas Engine

2014 ◽  
Author(s):  
Won Geun Lee ◽  
David Montgomery
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Direct Injection ◽  
Gas Injection ◽  
Load Condition ◽  
Fuel Combustion ◽  
Dual Fuel ◽  
Injection Timing ◽  
Pilot Injection ◽  
Dual Fuel Combustion

High Pressure Direct-Injection (HPDI) is a technology option for engines used in mobile equipment applications where use of LNG as a fuel is desired. Using the combination of a diesel pilot injection and direct gas injection, HPDI has the potential to deliver low emissions, excellent transient performance, high efficiency, and high gas substitution. When the HPDI program was initially undertaken, in order to aid in initial hardware design, 3-dimensional computational fluid dynamic modeling was conducted to understand the mixing and reaction processes in the combustion chamber of an HPDI engine. Gaining insight into qualitative trends of operation parameters and hardware configurations was a first critical step toward delivering a hardware set to demonstrate HPDI natural gas combustion system capabilities. To model the combustion of multi-component fuel at arbitrary constituent ratios, a combustion model based on a detailed chemical kinetics approach was employed. Several published mechanisms and combinations of established mechanisms were tested by comparing results with existing fumigated dual fuel engine results. The result shows that some of combined mechanisms for n-heptane combustion and methane combustion are capable of adequately predicting combustion behavior in diesel-natural gas dual fuel combustion systems. One of the reduced n-heptane mechanisms (by Patel et al.) also matched dual fuel combustion results reasonably well. This preliminary simulation study was conducted with typical trapped air conditions and fuel quantities matching the energy delivery for a 100 % load condition in existing DI diesel engines. A full 360-degree mesh at intake valve closing was constructed and a detailed geometry of the gas injector nozzle and sac area was modeled in locally refined grids using a Caterpillar proprietary CFD code that accepts industry standard mechanisms. The diesel pilot injection followed by gas injection and resulting combustion inside an HPDI engine was simulated from IVC through the compression and combustion strokes. The operating parameters — such as diesel pilot injection timing, pilot injection amount, and start of gas injection — were varied, and the effect on IMEP, NOx, CO and cylinder pressure were investigated. It was shown that the start of gas injection is the strongest parameter for control of combustion. Subsequent to the work discussed in this paper, the hardware configuration established as optimal during the modeling work was carried forward to the physical engine testing and was successful in delivering the performance and emissions goals without modification, demonstrating the accuracy and value of modern combustion modeling.

scholarly journals Assessment of late pilot injection effect in dual-fuel combustion

2020 ◽  
Vol 197 ◽  
pp. 06010
Author(s):  
Antonio Caricato ◽  
Antonio Paolo Carlucci ◽  
Antonio Ficarella ◽  
Luciano Strafella
Keyword(s):  
Injection Pressure ◽  
Dual Fuel ◽  
Injection Timing ◽  
Pilot Injection ◽  
Compression Ignition Engine ◽  
Engine Load ◽  
Pilot Fuel ◽  
Dual Fuel Combustion ◽  
Cylinder Compression ◽  
Injection Effect

In this paper, the effect of late injection on combustion and emission levels has been investigated on a single cylinder compression ignition engine operated in dual-fuel mode injecting methane along the intake duct and igniting it through a pilot fuel injected directly into the combustion chamber. During the tests, the amount of pilot fuel injected per cycle has been kept constant, while the amount of methane has been varied on three levels. Therefore, three levels of engine load have been tested, while speed has been kept constant equal to 1500rpm. Pilot injection pressure has been varied on three set points, namely 500, 1000 and 1500 bar. For each engine load and injection pressure, pilot injection timing has been swept on a very broad range of values, spanning from very advanced to very late values. The analysis of heat release rate indicates that MK-like conditions are established in dual-fuel mode with late pilot injection. In these conditions, pollutant species, and NOx levels in particular, are significantly reduced without penalization – and in several conditions with improvement – on fuel conversion efficiency.

Early Pilot Injection Strategies for Reactivity Control in Diesel-ethanol Dual Fuel Combustion

2018 ◽  
Author(s):  
Shui Yu ◽  
Shouvik Dev ◽  
Zhenyi Yang ◽  
Simon Leblanc ◽  
Xiao Yu ◽  
...  
Keyword(s):  
Fuel Combustion ◽  
Dual Fuel ◽  
Pilot Injection ◽  
Dual Fuel Combustion ◽  
Injection Strategies

Performance and Emissions Characteristics of Diesel-Ignited Gasoline Dual Fuel Combustion in a Single-Cylinder Research Engine

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
U. Dwivedi ◽  
C. D. Carpenter ◽  
E. S. Guerry ◽  
A. C. Polk ◽  
S. R. Krishnan ◽  
...  
Keyword(s):  
Injection Pressure ◽  
Fuel Combustion ◽  
Injection System ◽  
Dual Fuel ◽  
Heterogeneous Combustion ◽  
Boost Pressure ◽  
Fuel Injector ◽  
Single Cylinder ◽  
Diesel Injection ◽  
Dual Fuel Combustion

Diesel-ignited gasoline dual fuel combustion experiments were performed in a single-cylinder research engine (SCRE), outfitted with a common-rail diesel injection system and a stand-alone engine controller. Gasoline was injected in the intake port using a port-fuel injector. The engine was operated at a constant speed of 1500 rev/min, a constant load of 5.2 bar indicated mean effective pressure (IMEP), and a constant gasoline energy substitution of 80%. Parameters such as diesel injection timing (SOI), diesel injection pressure, and boost pressure were varied to quantify their impact on engine performance and engine-out indicated specific nitrogen oxide emissions (ISNOx), indicated specific hydrocarbon emissions (ISHC), indicated specific carbon monoxide emissions (ISCO), and smoke emissions. Advancing SOI from 30 degrees before top dead center (DBTDC) to 60 DBTDC reduced ISNOx from 14 g/kW h to less than 0.1 g/kW h; further advancement of SOI did not yield significant ISNOx reduction. A fundamental change was observed from heterogeneous combustion at 30 DBTDC to “premixed enough” combustion at 50–80 DBTDC and finally to well-mixed diesel-assisted gasoline homogeneous charge compression ignition (HCCI)-like combustion at 170 DBTDC. Smoke emissions were less than 0.1 filter smoke number (FSN) at all SOIs, while ISHC and ISCO were in the range of 8–20 g/kW h, with the earliest SOIs yielding very high values. Indicated fuel conversion efficiencies were ∼ 40–42.5%. An injection pressure sweep from 200 to 1300 bar at 50 DBTDC SOI and 1.5 bar intake boost showed that very low injection pressures lead to more heterogeneous combustion and higher ISNOx and ISCO emissions, while smoke and ISHC emissions remained unaffected. A boost pressure sweep from 1.1 to 1.8 bar at 50 DBTDC SOI and 500 bar rail pressure showed very rapid combustion for the lowest boost conditions, leading to high pressure rise rates, higher ISNOx emissions, and lower ISCO emissions, while smoke and ISHC emissions remained unaffected by boost pressure variations.

Characterization of reaction zone growth in an optically accessible heavy-duty diesel/methane dual-fuel engine

2018 ◽  
Vol 20 (5) ◽  
pp. 483-500 ◽  
Author(s):  
Jeremy Rochussen ◽  
Patrick Kirchen
Keyword(s):  
Growth Rate ◽  
Reaction Zone ◽  
Flame Propagation ◽  
High Speed ◽  
Dual Fuel ◽  
Pilot Injection ◽  
Fuel Conversion ◽  
Dual Fuel Engines ◽  
Dual Fuel Combustion ◽  
Zone Growth

The performance of dual-fuel engines in terms of fuel conversion efficiency and unburned hydrocarbon emission is strongly influenced by the turbulent flame propagation through the premixed natural gas. To improve dual-fuel engine design and provide validation data for numerical models, the fuel conversion process must be better characterized, specifically the reaction zone growth rate. In this work, high-speed imaging of OH*-chemiluminescence is performed in an optically accessible 2 L engine operated with port-injected CH4 and direct-injected diesel for different diesel and CH4 fueling rates and pilot injection pressures ( Ppilot). The cumulative histogram time series is introduced for directly comparing high-speed optical data of dual-fuel combustion with simultaneously measured apparent heat release rate. The cumulative histogram time series diagram is also used to evaluate a “global” reaction zone speed, SRZ,g, based on OH*-chemiluminescence images. The SRZ,g calculation normalizes the reaction zone area growth rate by the perimeter of the reaction zone to determine the velocity scale, while a “local” reaction zone speed, SRZ,l, is based on the local displacement of the reaction zone boundary per unit time. From the distribution of SRZ,l for each image frame, a previously proposed metric for determining the transition from pilot autoignition based on apparent heat release rate was validated and used to evaluate a single mean flame propagation speed, [Formula: see text]. Using these metrics, it was noted that increasing ϕCH4 from 0.40 to 0.69 results in an increase in [Formula: see text] from 4 to 8 m/s and 8 to 14 m/s for pilot injection pressures of 300 and 1300 bar, respectively. The spatial distribution of SRZ,l also indicates that autoignition of the pilot jets is not simultaneous (arising from asymmetric injector geometry) and leads to an overlap of the autoignition and flame propagation processes. This is not considered in the conventional conceptual model of dual-fuel combustion and impacts calculation of [Formula: see text] for the small diesel injections commonly used for dual-fuel engines.

Effects of N-Butanol Content on the Dual-Fuel Combustion Mode With CNG at Two Engine Speeds

2018 ◽  
Author(s):  
Xiangyu Meng ◽  
Wuqiang Long ◽  
Yihui Zhou ◽  
Mingshu Bi ◽  
Chia-Fon F. Lee
Keyword(s):  
Thermal Efficiency ◽  
Engine Speed ◽  
Direct Injection ◽  
Fuel Combustion ◽  
Dual Fuel ◽  
Combustion Mode ◽  
Start Of Injection ◽  
Wide Range ◽  
Pilot Fuel ◽  
Dual Fuel Combustion

Because of the potential to reduce NOx and PM emissions simultaneously and the utilization of biofuel, diesel/compressed natural gas (CNG) dual-fuel combustion mode with port injection of CNG and direct injection of diesel has been widely studied. While in comparison with conventional diesel combustion mode, the dual-fuel combustion mode generally leads lower thermal efficiency, especially at low and medium load, and higher carbon monoxide (CO) and total hydrocarbons (THC) emissions. In this work, n-butanol was blended with diesel as the pilot fuel to explore the possibility to improve the performance and emissions of dual-fuel combustion mode with CNG. Various pilot fuels of B0 (pure diesel), B10 (90% diesel/10% n-butanol by volume basis), B20 (80% diesel/20% n-butanol) and B30 (70% diesel/30% n-butanol) were compared at the CNG substitution rate of 70% by energy basis under the engine speeds of 1400 and 1800 rpm. The experiments were carried out by sweeping a wide range of pilot fuel start of injection timings based on the same total input energy including pilot fuel and CNG. As n-butanol was added into the pilot fuel, the pilot fuel/CNG/air mixture tends to be more homogeneous. The results showed that for the engine speed of 1400 rpm, pilot fuel with n-butanol addition leads to a slightly lower indicated thermal efficiency (ITE). B30 reveals much lower NOx emission and slightly higher THC emissions. For the engine speed of 1800 rpm, B20 can improve ITE and decrease the NOx and THC emissions simultaneously relative to B0.

Sign in / Sign up

Export Citation Format

Share Document