scholarly journals Experimental Study of the Effect of Start of Injection and Blend Ratio on Single Fuel Reformate RCCI

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Deivanayagam Hariharan ◽  
Brian Gainey ◽  
Ziming Yan ◽  
Sotirios Mamalis ◽  
Benjamin Lawler
Keyword(s):  
Oxygen Deficiency ◽  
Fuel Mixture ◽  
Combustion Efficiency ◽  
High Reactivity ◽  
Inert Gases ◽  
Injection Timing ◽  
Indicated Mean Effective Pressure ◽  
Start Of Injection ◽  
The Difference ◽  
Blend Ratios

Abstract A new concept of single fuel reactivity-controlled compression ignition (RCCI) has been proposed through the catalytic partial oxidation (CPOX) reformation of diesel fuel. The reformed fuel mixture is then used as the low reactivity fuel and diesel itself is used as the high reactivity fuel. In this paper, two reformate mixtures from the reformation of diesel were selected for further analysis. Each reformate fuel mixture contained a significant fraction of inert gases (89% and 81%). The effects of the difference in the molar concentrations of the reformate mixtures were studied by experimenting with diesel as the direct injected fuel in RCCI over a varying start of injection timings and different blend ratios (i.e., the fraction of low and high reactivity fuels). The reformate mixture with the lower inert gas concentration had earlier combustion phasing and shorter combustion duration at any given diesel start of injection timing. The higher reactivity separation between reformate mixture and diesel, compared with gasoline and diesel, causes the combustion phasing of reformate-diesel RCCI to be more sensitive to the start of injection timing. The maximum combustion efficiency was found at a CA50 before top dead center (TDC), whereas the maximum thermal efficiency occurs at a CA50 after TDC. The range of energy-based blend ratios in which reformate-diesel RCCI is possible is between 25% and 45%, limited by ringing intensity (RI) at the low limit of blend ratios, and coefficient of variance (COV) of net indicated mean effective pressure (IMEPn) and combustion efficiency at the high limit. Intake boosting becomes necessary due to the oxygen deficiency caused by the low energy density of the reformate mixtures as it displaces intake air.

scholarly journals Experimental Study of the Effect of Start of Injection and Blend Ratio on Single Fuel Reformate RCCI

2019 ◽  
Author(s):  
Deivanayagam Hariharan ◽  
Brian Gainey ◽  
Ziming Yan ◽  
Sotirios Mamalis ◽  
Benjamin Lawler
Keyword(s):  
Oxygen Deficiency ◽  
Fuel Mixture ◽  
Combustion Efficiency ◽  
High Reactivity ◽  
Inert Gases ◽  
Injection Timing ◽  
Start Of Injection ◽  
Combustion Duration ◽  
The Difference ◽  
Blend Ratios

Abstract A new concept of single-fuel RCCI has been proposed through the catalytic partial oxidation reformation of diesel fuel. The reformed fuel mixture is then used as the low reactivity fuel and diesel itself is used as the high reactivity fuel. In this paper, two selected reformates mixture from the reformation of diesel were selected for further analysis. Each reformate fuel mixture contained a significant fraction of inert gases (89% and 81%). The effects of the difference in the molar concentrations of the reformate mixtures were studied by experimenting with diesel as the direct injected fuel in RCCI over a varying start of injection timings and different blend ratios (i.e., the fraction of low and high reactivities fuels). The reformate mixture with the lower inert gas concentration had earlier combustion phasing and shorter combustion duration at any given diesel start of injection timing. The higher reactivity separation between reformate mixture and diesel, compared with gasoline and diesel, causes the combustion phasing of reformate-diesel RCCI to be more sensitive to the start of injection timing. The maximum combustion efficiency was found at a CA50 before TDC, whereas the maximum thermal efficiency occurs at a CA50 after TDC. The range of energy-based blend ratios in which reformate-diesel RCCI is possible is between 25% and 45%, limited by ringing intensity (RI) at the low limit of blend ratios, and COV of IMEP and combustion efficiency at the high limit. Intake boosting becomes necessary due to the oxygen deficiency caused by the low energy density of the reformate mixtures as it displaces intake air.

Numerical Simulation of a Naturally Aspirated Natural Gas/Diesel RCCI Engine for Investigating the Effects of Injection Timing on the Combustion and Emissions

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Amir Hossein Fakhari ◽  
Rouzbeh Shafaghat ◽  
Omid Jahanian
Keyword(s):  
Natural Gas ◽  
Fuel Mixture ◽  
Injection Timing ◽  
Reactivity Controlled Compression Ignition ◽  
Piston Bowl ◽  
Start Of Injection ◽  
Performance And Emissions ◽  
The Difference ◽  
The Impact ◽  
Co Emission

Abstract The start of injection (SOI) timing has a significant effect on increasing the homogeneity of the air–fuel mixture in an reactivity controlled compression ignition (RCCI) engine. In this paper, the impact of the SOI timing from 14 deg to 74 deg before top dead center (bTDC) and different inlet valve closing (IVC) temperatures on natural gas/diesel RCCI performance and emissions have been studied. Also, the simulations carried out by avl fire which is coupled with chemical kinetics. The results showed that in the SOIs of 14 deg, 24 deg, and 34 deg bTDC, the fuel is sprayed into the piston bowl; however, in the SOI of 44 deg bTDC, the fuel collides the bowl rim edge, because of the downward movement of the piston. With the advancement of diesel SOI timing from 14 deg to 74 deg bTDC, two different combustion trends can be observed. However, this advancement leads to a lower CO emission, but it raises the CO2 emission level. Although the pressure is a primary parameter for NOx emission, the difference between the trends of NOx and pressure plots indicates that different factors affect the NOx production and also increase the IVC temperature, and raises the in-cylinder pressure, heat release rate, NOx and CO2 emissions, while it reduces the CO emission.

Analysis of cycle-by-cycle variation in a direct injection gasoline engine using a laser-induced fluorescence technique

2003 ◽  
Vol 4 (2) ◽  
pp. 143-153 ◽  
Author(s):  
T Fujikawa ◽  
Y Nomura ◽  
Y Hattori ◽  
T Kobayashi ◽  
M Kanda
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Mixture Distribution ◽  
Fuel Mixture ◽  
Laser Induced Fluorescence ◽  
Injection Timing ◽  
Indicated Mean Effective Pressure ◽  
Cycle Variation ◽  
Spark Timing ◽  
Direct Injection Gasoline Engine

To analyse the cycle-by-cycle variation of combustion in a direct injection gasoline engine equipped with a fan-shape spray nozzle and operated with exhaust gas recirculation (EGR), the fuel mixture distribution was measured at a time of spark and during the combustion period by the laser-induced fluorescence (LIF) technique. It was found that in the case of advanced or retarded injection timing, the initial combustion period tends to extend and the indicated mean effective pressure (i.m.e.p.) becomes low when lean mixtures appear at the spark position and at the spark timing. This suggests that the cycle-by-cycle variation of combustion under these conditions is dominated by the fuel concentration at the spark position and spark timing. In contrast to this, for the best injection timing, which allows the lowest cycle-by-cycle variation, the i.m.e.p. fluctuation is affected not by the initial combustion period but by the main combustion period. The observation of LIF images revealed that the i.m.e.p. fluctuation at this condition is strongly correlated to the unburned mixture quantity at the side area of the piston cavity during the latter half of the combustion period. It was shown by a computational fluid dynamics (CFD) calculation that the combination of a uniform spray pattern and a compact cavity shape is effective to reduce the over-lean mixture region in the edge of the piston cavity, which is responsible for the cycle-by-cycle variation of combustion at the condition of best-tuned injection timing.

scholarly journals Investigation Into Reactivity Separation Between Direct Injected and Premixed Fuels in RCCI Combustion Mode

2019 ◽  
Author(s):  
Ziming Yan ◽  
Brian Gainey ◽  
Deivanayagam Hariharan ◽  
Benjamin Lawler
Keyword(s):  
Thermal Efficiency ◽  
Fuel Injection ◽  
Direct Injection ◽  
Combustion Efficiency ◽  
High Reactivity ◽  
Injection System ◽  
Injection Timing ◽  
Nox Emissions ◽  
Light Duty ◽  
Primary Reference

Abstract This experimental study focuses on the effects of the reactivity separation between the port injected fuel and the direct injection fuel, the amount of external-cooled exhaust gas recirculation (EGR), and the direct injection timing of the high reactivity fuel on Reactivity Controlled Compression Ignition (RCCI) combustion. The experiments were conducted on a light-duty, single-cylinder diesel engine with a production GM/Isuzu engine head and piston and a retrofitted port fuel injection system. The global charge-mass equivalence ratio, ϕ′, was fixed at 0.32 throughout all of the experiments. To investigate the effects of the fuel reactivity separation, different Primary Reference Fuels (PRF) were port injected, with the PRF number varying from 50 to 90. To investigate the effects of EGR, an EGR range of 0 to 55% was used. To investigate the effects of the injection timing, an injection timing window of −65 to −45 degrees ATDC was chosen. The results indicate that there are several tradeoffs. First, decreasing the port injected fuel reactivity (increasing the PRF number) delays combustion phasing, decreases the combustion efficiency by up to 9%, increases the gross indicated thermal efficiency up to 22%, enhances the combustion sensitivity to the direct injection timing, and slightly increases the UHC, CO, and NOx emissions. Second, increasing the EGR percentage delays combustion phasing, lowers the peak heat release rate, and lowers the NOx emissions. The combustion efficiency first increases and then decreases with EGR percentage for high reactivity fuels (low PRF number), but only decreases for low reactivity fuels. Finally, delaying the injection timing advances combustion phasing and increases the combustion efficiency, but decreases the gross indicated thermal efficiency and increases the NOx emissions. Across all of the experiments, delays in CA50 increase the gross indicated thermal efficiency and decrease the combustion efficiency, which represents an inherent tradeoff for RCCI combustion on a light-duty engine.

scholarly journals Cycle-by-cycle variations in autonomous and spark assisted homogeneous charge compression ignition combustion of stoichiometric air–fuel mixture

2018 ◽  
Vol 10 (3) ◽  
pp. 231-243 ◽  
Author(s):  
Jacek Hunicz
Keyword(s):  
Homogeneous Charge Compression Ignition ◽  
Fuel Injection ◽  
Fuel Mixture ◽  
Compression Ignition ◽  
Indicated Mean Effective Pressure ◽  
Start Of Injection ◽  
Negative Valve Overlap ◽  
Compression Ignition Combustion ◽  
Valve Overlap ◽  
Homogeneous Charge

This study investigates cycle-by-cycle variations in a gasoline fuelled, homogeneous charge compression ignition (HCCI) engine with internal exhaust gas recirculation. In order to study the effects of exhaust-fuel reactions occurring prior to the main combustion event fuel was injected directly into the cylinder at two selected timings during the negative valve overlap period. The engine was operated as both autonomous HCCI and spark assisted HCCI (SA-HCCI). The primary interest in this work was the operating region where the engine is switched between HCCI and spark ignition modes, thus operation with stoichiometric air–fuel mixture, which is typical for this region, was considered. Cycle-by-cycle variations in both combustion timing and indicated mean effective pressure (IMEP) were investigated. It was found that long-period oscillations of the IMEP occur when fuel injection is started at early stages of the negative valve overlap period, and that these can be suppressed by delaying the start of injection. This behaviour remained even when fuel injection was split into early and late-negative valve overlap injections. Spark assisted operation allowed eliminating late combustion cycles, thus improving thermal efficiency. However, characteristic patterns of IMEP variations were found to be the same for both HCCI and SA-HCCI operations, irrespective of the adopted negative valve overlap fuel injection strategy, as evidenced by using symbol-sequence statistics.

scholarly journals An Experimental Investigation on the Influence of Port Injection at Valve on Combustion and Emission Characteristics of B5/Biogas RCCI Engine

2020 ◽  
Vol 10 (2) ◽  
pp. 452
Author(s):  
Ibrahim B. Dalha ◽  
Mior A. Said ◽  
Zainal A. Abdul Karim ◽  
Salah E. Mohammed
Keyword(s):  
Fuel Mixture ◽  
Injection Timing ◽  
Compression Ignition ◽  
Reactivity Controlled Compression Ignition ◽  
Indicated Mean Effective Pressure ◽  
Unburned Hydrocarbon ◽  
Crank Angle ◽  
Slow Combustion ◽  
Low Load ◽  
Co Emission

High unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions, on account of the premixed air-fuel mixture entering the crevices and pre-mature combustion, are setbacks to reactivity-controlled compression ignition (RCCI) combustion at a low load. The influence of direct-injected B5 and port injection of biogas at the intake valve was, experimentally, examined in the RCCI mode. The port injection at the valve was to elevate the temperature at low load and eliminate premixing for reduced pre-mature combustion and fuel entering the crevices. An advanced injection timing of 21° crank angle before top dead centre and fraction of 50% each of the fuels, were maintained at speeds of 1600, 1800 and 2000 rpm and varied the load from 4.5 to 6.5 bar indicated mean effective pressure (IMEP). The result shows slow combustion as the load increases with the highest indicated thermal efficiency of 36.33% at 5.5 bar IMEP. The carbon dioxide and nitrogen oxides emissions increased, but UHC emission decreased, significantly, as the load increases. However, CO emission rose from 4.5 to 5.5 bar IMEP, then reduced as the load increases. The use of these fuels and biogas injection at the valve were capable of averagely reducing the persistent challenge of the CO and UHC emissions, by 20.33% and 10% respectively, compared to the conventional premixed mode.

Two-Stroke Marine Diesel Engine Variable Injection Timing System Performance Evaluation and Optimum Setting for Minimum Fuel Consumption at Acceptable NOx Levels

2014 ◽  
Author(s):  
Dimitrios T. Hountalas ◽  
Spiridon Raptotasios ◽  
Antonis Antonopoulos ◽  
Stavros Daniolos ◽  
Iosif Dolaptzis ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Engine Performance ◽  
Operating Conditions ◽  
Specific Fuel Consumption ◽  
Injection Timing ◽  
Nox Emissions ◽  
Pressure Measurements ◽  
Cylinder Pressure ◽  
Start Of Injection

Currently the most promising solution for marine propulsion is the two-stroke low-speed diesel engine. Start of Injection (SOI) is of significant importance for these engines due to its effect on firing pressure and specific fuel consumption. Therefore these engines are usually equipped with Variable Injection Timing (VIT) systems for variation of SOI with load. Proper operation of these systems is essential for both safe engine operation and performance since they are also used to control peak firing pressure. However, it is rather difficult to evaluate the operation of VIT system and determine the required rack settings for a specific SOI angle without using experimental techniques, which are extremely expensive and time consuming. For this reason in the present work it is examined the use of on-board monitoring and diagnosis techniques to overcome this difficulty. The application is conducted on a commercial vessel equipped with a two-stroke engine from which cylinder pressure measurements were acquired. From the processing of measurements acquired at various operating conditions it is determined the relation between VIT rack position and start of injection angle. This is used to evaluate the VIT system condition and determine the required settings to achieve the desired SOI angle. After VIT system tuning, new measurements were acquired from the processing of which results were derived for various operating parameters, i.e. brake power, specific fuel consumption, heat release rate, start of combustion etc. From the comparative evaluation of results before and after VIT adjustment it is revealed an improvement of specific fuel consumption while firing pressure remains within limits. It is thus revealed that the proposed method has the potential to overcome the disadvantages of purely experimental trial and error methods and that its use can result to fuel saving with minimum effort and time. To evaluate the corresponding effect on NOx emissions, as required by Marpol Annex-VI regulation a theoretical investigation is conducted using a multi-zone combustion model. Shop-test and NOx-file data are used to evaluate its ability to predict engine performance and NOx emissions before conducting the investigation. Moreover, the results derived from the on-board cylinder pressure measurements, after VIT system tuning, are used to evaluate the model’s ability to predict the effect of SOI variation on engine performance. Then the simulation model is applied to estimate the impact of SOI advance on NOx emissions. As revealed NOx emissions remain within limits despite the SOI variation (increase).

A comparative numerical study of the combustion performance of the syngas-fueled HCCI engine using a toroidal piston, square bowl piston, and flat piston shape at different loads

2021 ◽  
pp. 1-27
Author(s):  
Kabbir Ali ◽  
Changup Kim ◽  
Yonggyu Lee ◽  
Seungmook Oh ◽  
Ki-Seong Kim
Keyword(s):  
Numerical Study ◽  
Pressure Rise ◽  
Fuel Mixture ◽  
Combustion Efficiency ◽  
Maximum Pressure ◽  
Cross Sectional ◽  
Combustion Performance ◽  
Hcci Engine ◽  
Heat Loss Rate ◽  
Piston Bowl

Abstract This study analyzes the combustion performance of a syngas-fueled homogenous charge compression ignition (HCCI) engine using a toroidal piston, square bowl, and flat piston shape, at low, medium, and high loads, with a constant compression ratio of 17.1. In this study, the square bowl shape is optimized by reducing the piston bowl depth and squish area ratio (squish area/cylinder cross-sectional area) from (34 to 20, 10, and 2.5) %, and compared with the flat piston shape and toroidal piston shape. This HCCI engine operates under an overly lean air–fuel mixture condition for power plant usage. ANSYS Forte CFD with GRI Mech3.0 chemical kinetics is used for combustion analysis, and the calculated results are validated by the experimental results. All simulations are accomplished at maximum brake torque (MBT) by altering the air–fuel mixture temperature at IVC with a constant equivalence ratio of 0.27. This study reveals that the main factors that affect the start of combustion , maximum pressure rise rate (MPRR), combustion efficiency, and thermal efficiency by changing the piston shape are the squish flow and reverse squish flow effects. Therefore, the square bowl piston D is the optimized piston shape that offers low MPRR and high combustion performance for the syngas-fueled HCCI engine, due to the weak squish flow and low heat loss rate through the combustion chamber wall, respectively, compared to the other piston shapes of square bowl piston A, B, and C, flat piston, and toroidal (baseline) piston shape.

Exploring the Effects of Piston Bowl Geometry and Injector Included Angle On Dual-Fuel and Single-Fuel RCCI

2021 ◽  
Author(s):  
Deivanayagam Hariharan ◽  
Mozhgan Rahimi Boldaji ◽  
Ziming Yan ◽  
Brian Gainey ◽  
Benjamin Lawler
Keyword(s):  
Thermal Efficiency ◽  
Lower Surface ◽  
Combustion Efficiency ◽  
Low Temperature Combustion ◽  
Included Angle ◽  
Piston Bowl ◽  
Start Of Injection ◽  
Lower Reactivity ◽  
Secondary Fuel ◽  
Temperature Combustion

Abstract Reactivity Control Compression Ignition (RCCI) is a Low-Temperature Combustion (LTC) technique that have been proposed to meet the current demand for high thermal efficiency and low engine-out emissions. However, its requirement of two separate fuel systems has been one of its major challenges in the last decade. This leads to the single-fuel RCCI concept, where the secondary fuel is generated from the primary fuel through CPOX reformation. After studying three different fuels, diesel was found to be the best candidate for the reformation process, where the reformed gaseous fuel (with lower reactivity) was used as the secondary fuel and the parent diesel fuel (with higher reactivity) was used as the primary fuel. Previously, the effects of the start of injection (SOI) timing of diesel and the energy-based blend ratio were studied in detail. In this study, the effect of piston profile and the injector included angles were experimentally studied using both conventional fuel pairs and reformate RCCI. A validated CFD model was also used for a better understanding of the experimental trends. Comparing a re-entrant bowl piston with a shallow bowl piston, the latter showed better thermal efficiency, regardless of the fuel combination, due to its 10% lower surface area for the heat transfer. Comparing the 150-degree and 60-degree included angle, the latter showed better combustion efficiency, regardless of the fuel combination, due to its earlier combustion phasing (at constant SOI timing) as the fuel spray targets better region of the cylinder.

Experimental Investigation of Effects of Split Diesel-Pilot Injection on Emissions From Ammonia-Diesel Dual Fuel Engine

2021 ◽  
Author(s):  
Yoichi Niki
Keyword(s):  
Diesel Fuel ◽  
Internal Combustion Engines ◽  
Ghg Emissions ◽  
High Reactivity ◽  
Dual Fuel ◽  
N2o Emissions ◽  
Injection Timing ◽  
Pilot Injection ◽  
Reduce Emissions ◽  
And Performance

Abstract NH3 has been investigated for its use as an alternative fuel including for use in internal combustion engines. In NH3 combustion, emissions of unburned NH3 with toxicity and N2O as a combustion product with high global warming potential (GWP) are important issues. However, few researchers have investigated NH3 and N2O emissions from NH3 assisted diesel engines operated using NH3–diesel dual fuel. We investigate a combustion strategy to reduce these emissions with a single-cylinder diesel engine mixed NH3 gas into the intake air. We found that an early diesel pilot injection reduced unburned NH3 and N2O emissions while HC and CO emissions increased. It was also reported that NH3 and diesel fuel work as low and high reactivity fuel for reactivity controlled compression ignition combustion (RCCI), respectively. Our previous study reports the aspects of RCCI on NH3–diesel dual fuel engine to some extent. The injection timing of diesel fuel and the quantity of NH3 govern the emissions and performance on RCCI combustion. These effects need to be investigated to manipulate the RCCI combustion and reduce emissions. This paper reports the efficiency and emissions for the diesel pilot injection timing sweep at various NH3 supply quantities and the effects of a split injection on the emissions and a combustion phase. In addition, we estimated the reduction in GHG emissions using a NH3–diesel dual fuel engine, which applied the early diesel pilot injection, compared with the diesel only operation, considering the N2O GWP.

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