Effect Of Multiple Injection Strategies Research Articles

Numerical study on the effect of multiple injection strategies on ignition processes for low-temperature diesel spray

The multiple-injection strategies can significantly improve the diesel engine startability at low-temperature conditions, but the processes are extremely complex due to the effect of various factors simultaneously. To find out how the pilot injection affects the main injection, the spray and ignition with different injection strategies at low temperatures, and the effect of the interaction of the pilot and main injections on mixing and ignition are studied numerically. The results show that the main injection fuel can catch up with the pilot injection which has been pre-heated, making the peripheral fuel of the main injection has a higher temperature and equivalence ratio compared to the single injection, which can accelerate the chemical reaction process and thus shorten the ignition delay. The products of the pre-reacted pilot fuel are mixed with the peripheral fuel of the main injection and affect the reaction process. The pre-injected fuel can promote the combustion and shorten the ignition delay of the main injection fuel because the remaining species of pre-injected fuel can make n-dodecane dehydrogenated with the intermediate products such as OH in preference to O2. However, mixing the injections too late prevents the pre-injected fuel from promoting the combustion of the main injection. The concentration of CH2O increases rapidly during the first heat release, and the species at this moment significantly inhibit the combustion of the new fuel.

Effects of Multiple Injection Strategies on Heavy-Duty Diesel Energy Distributions and Emissions Under High Peak Combustion Pressures

Peak combustion pressures (PCP) are increased in heavy-duty diesel engines to obtain higher thermal efficiency. Fuel injection strategy has been a major measure to improve the combustion and emissions of diesel engines. But most existing work of multi-injection strategies was not limited by PCP or was conducted under lower PCP (∼15 MPa). In this study, an experimental study is conducted to further improve the understanding of injection strategies on engine performance under a relative higher peak combustion pressure at 20 MPa. The four tested injection strategies are single main injection, pilot-main injection, main-post injection, and pilot-main-post injection. The effects of PCP on brake thermal efficiency (BTE) and other engine performances are also investigated under the same NOx emissions conditions. Results indicate that more advanced injection timing can obtain higher BTE, while the injection pressure has less effects on BTE as it is higher than 120 MPa. For double-injection, the smaller interval on pilot-main or main-post and the less pilot or post mass improves BTE and emissions. The PCPs are linearly correlated to the BTE, peak average temperature, and peak pressure rise rate (PRR), and the increment of BTE, peak average temperature, and peak PRR are about 0.3%, 30 K, and 0.1 MPa/CA for every 1 MPa increase in PCP, respectively. This also means that the improvement on BTE by the increase of PCP imparts greater thermal and mechanical loads on engine materials and components. At 20 MPa PCP, based on the optimized injection strategies, the BTE of all four strategies is about 42.8%, and the peak PRR of all four strategies is about 0.8 MPa/CA. At a given NOx emission of 17.4 g/kWh and approximate 20 MPa PCP, all four injection strategies have minor effects on distribution of fuel energy and emissions. Therefore, it can be concluded that the injection strategies have fewer effects on BTE and emissions at the higher peak combustion pressure of 20 MPa; the main purpose of injection strategies is to reduce the peak PRR or reach the potentially required temperature for aftertreatment devices.

A comprehensive study on the effects of multiple injection strategies and exhaust gas recirculation on diesel engine characteristics that utilize waste high density polyethylene oil

ABSTRACT The present study utilized the catalytic pyrolysis method for extracting oil from waste high-density polyethylene (WHDPE) plastics. Experiments were carried out with D70H30 (diesel-70%, WHDPE oil-30%) blend under the influence of three start of pilot injection (SoPI) timings [45° before top dead center (bTDC), 50°bTDC, and 55°bTDC] and three pilot fuel injection quantity (PFIQ) (10%, 20%, and 30%) at the engine’s rated power output. Later, the impact of exhaust gas recirculation (EGR) (0%, 10%, and 20%) was studied with the optimum SoPI and PFIQ. Experimental results indicated that at SoPI timing of 55°bTDC and at PFIQ of 30%, the brake thermal efficiency (BTE) increased by 8.5%, nitrogen oxides (NOx) increased by 19.25%, while smoke, hydrocarbons (HC), and CO emission got lowered with baseline operation of the blend and found to be best among other modifications. In the next phase of the work, exhaust gas is recirculated at 10% and 20%. The results portray that inclusion of 10% EGR in the intake at SoPI 55°bTDC and at PFIQ 30% has shown 1.7% higher BTE, with 3.7% and 28.9% lower NOx and smoke emission compared to the single main injection of the blend. It is concluded that pilot injection strategy with 30% PFIQ and SoPI timing of 55°bTDC at 10% EGR rate can be adopted to utilize WHDPE oil/diesel in diesel engines effectively.

Experimental Analysis on the Effects of Multiple Injection Strategies on Pollutant Emissions, Combustion Noise, and Fuel Consumption in a Premixed Charge Compression Ignition Engine

Experimental Analysis on the Effects of Multiple Injection Strategies on Pollutant Emissions, Combustion Noise, and Fuel Consumption in a Premixed Charge Compression Ignition Engine

Analysis of the effects of multiple injection strategies with hydrogen on engine performance and emissions in diesel engine

In this study, firstly, the turbocharged, compression-ignition, light duty vehicle engine was loaded with a DC dynamometer. The real test engine was run at partial load (90%) and at different engine speeds with normal diesel fuel. In the second stage, a model engine was created and verified with the mixing control combustion (MCC) module suitable for hydrogen combustion using AVL BOOST simulation software with real test parameters such as engine performance and cylinder pressure values. At the last stage, multiple hydrogen injection strategies were applied in the simulation program using pure hydrogen as pilot and post fuel and diesel as the main fuel, and were examined numerically in terms of performance and emissions. The results showed that 2 pilot injections and 1 post-injection strategy reduced soot emissions more than 1 pilot injection strategy. However, NOx increased slightly in all three injection applications. In addition, a significant increase in engine power was observed.

Effects of multiple injection strategies on gaseous emissions and particle size distribution in a two-stroke compression-ignition engine operating with the gasoline partially premixed combustion concept

In order to improve performance of internal combustion engines and meet the requirements of the new pollutant emission regulations, advanced combustion strategies have been investigated. The newly designed partially premixed combustion concept has demonstrated its potential for reducing NOx and particulate matter emissions combined with high indicated efficiencies while still retaining proper control over combustion process by using different injection strategies. In this study, parametric variations of injection pressure, second injection and third injection timings were experimentally performed to analyze the effect of the injection strategy over the air/fuel mixture process and its consequent impact on gaseous compound emissions and particulate matter emissions including its size distribution. Tests were carried out on a newly designed two-stroke high-speed direct injection compression-ignition engine operating with the partially premixed combustion concept using 95 research octane number gasoline fuel. A scanning particle sizer was used to measure the particles size distribution and the HORIBA 7100DEGR gas analyzer system to determine gaseous emissions. Three different steady-state operation modes in terms of indicated mean effective pressure and engine speed were investigated: 3.5 bar indicated mean effective pressure and 2000 r/min, 5.5 bar indicated mean effective pressure and 2000 r/min, and 5.5 bar indicated mean effective pressure and 2500 r/min. The experimental results confirm how the use of an adequate injection strategy is indispensable to obtain low exhaust emissions values and a balance between the different pollutants. With the increase in the injection pressure and delay in the second injection, it was possible to obtain a trade-off between NOx and particulate matter emission reduction, while there was an increase in hydrocarbon and carbon monoxide emissions under these conditions. In addition, the experiments showed an increase in particle number emissions and a progressive shift in the particles size distribution toward larger sizes, increasing the accumulation-mode particles and reducing the nucleation-mode particles with the decrease in the injection pressure and delay in the third injection.

Effect of multiple injection strategies on emissions and performance in the Wärtsilä 6L 46 marine engine. A numerical approach

The present paper proposes a Computational Fluid Dynamics model to analyze the operation cycle and exhaust gas composition in a four-stroke marine diesel engine, the Wärtsilä 6L 46. Once validated, the numerical model was employed to study the influence of several pre-injection parameters such as pre-injection rate, duration, starting instant and number of pre-injections. The purpose is to reduce consumption and emissions, especially nitrogen oxides, due to the current increasingly restrictive legislation. It was found that the fuel injection is a critical factor influencing combustion and emission characteristics. Important nitrogen oxides emission reductions were obtained for the parameters analyzed. Particularly, a 31.9% nitrogen oxides reduction was obtained using 20% pilot injection, 65.7% advancing 4° the pre-injection start angle, 20.1% shorting 4° the pre-injection duration and 36.7% using 4 pre-injections. A slight increment of hydrocarbons, carbon monoxide and consumption was obtained, lower than 5% for almost all the cases analyzed, and a negligible effect on carbon dioxide emissions.

Improvement of diesel combustion with multiple injections at cold condition in a constant volume combustion chamber

A series of diesel spray combustion tests was carried out in a constant volume combustion chamber (CVCC) to investigate the effect of multiple injection strategies on cold startability. The experiments were performed under a simulated low temperature cold start condition. In-chamber pressure analysis and high speed flame imaging were conducted to compare the effectiveness of each injection strategy on cold startability. Spray targeting visualization was also performed to examine the wall impingement of injected fuel. The diesel fuel was injected into the CVCC with an injection pressure of 35MPa. Multiple injection strategies with different amounts of pilot injection quantities were applied to improve the diesel combustion under simulated cold start ambient condition. The flame imaging and in-chamber pressure results showed that the multiple injection strategy provided better cold startability than the single injection condition. According to the pilot injection quantity, the peak of the flame luminosity and in-chamber pressure were gradually increased with larger pilot injection quantity cases. The peak of the variation rate of the in-chamber pressure with a multiple injection strategy was approximately 2 times higher than that of the single injection case. In terms of spray targeting imaging, the results indicated that the fuel impingement and flow to the piston crevice volume were increased with a larger amount of pilot2 injection. Therefore, the increment of the pilot1 injection quantity rather than the pilot2 injection quantity was suggested not only to improve cold startability, but also to reduce unburned hydrocarbon emissions under a cold start condition in a real engine.

Experimental investigation on the influence of engine operating conditions on combustion and nanoparticle emission characteristics of a small DI diesel engine

The influence of variations in engine speed, injection pressure, injection timing, and multiple injection strategies on the combustion and nanoparticle characteristics of a small Direct injection (DI) diesel engine was experimentally investigated. To measure the size distribution and number concentration of particle emissions, a rotating disk thermo-diluter (dilution system), a Condensation particle counter (CPC), and a Scanning mobility particle sizer (SMPS) were used. The injection pressure was changed from 60 MPa to 120 MPa, at an engine speed of 1200 rpm. Injection timing was varied from Before top dead center (BTDC) 40˚ to Top dead center (TDC). To investigate the effect of multiple-injection strategies, the injection strategies consisted of two pulse signals with different dwell time. The experimental results show that the peak combustion pressure and Rate of heat release (ROHR) profile are increased and ignition delay is shortened with the increase of injection pressure from 60 MPa to 120 MPa. The concentration of soot emission for 120 MPa is lower than that of 60 MPa at advanced injection timing from TDC up to BTDC 25°. As the injection timing advances to over BTDC 30°, soot emissions rapidly increase and the high injection pressure case (120 MPa) creates more emissions than the 60 MPa case. The overall trends of total particle number are relatively increased with high injection pressure for single injection conditions. In the advanced injection timings of over BTDC 30°, the trend of total particle number is high for all injection pressures. For multiple injections, the peak combustion pressures and ROHR of multiple-injection strategies are slightly lower compared with those of single-combustion results. Comparing the multiple injection strategies, soot emission is reduced with the retard of second injection timing (-30°+5°). The overall trends of particle size and total number for the 7 mg+3 mg case revealed the lowest level compared with other cases, which is 50% lower than that for the 5 mg+5 mg case. When compared with single injection results, the total particle number and Dp of multiple injection cases were eventually lower.

Effect of Multiple Injection Strategies on Combustion and Emission Characteristics in a Diesel Engine

This paper presents an experimental and numerical investigation on the spray and combustion characteristics in a common rail diesel engine with two different multiple injection strategies involving a fixed injection interval (double injection strategy) and a fixed second injection timing (split injection strategy). In this study, the double injection strategy had a fixed 10° interval with before top dead center (BTDC) 40°, 30°, and 20° of first injection timing. The split injection strategy consisted of a two-stage injection, in which the second injection timing was fixed at top dead center (TDC), followed by a first injection that varied in timing from BTDC 40–10°. A high-pressure chamber with a maximum pressure of up to 4 MPa was used to analyze the spray characteristics of the various injection strategies at high ambient pressures. Spray images were obtained using a spray visualization system to analyze the spray behavior with multiple injection conditions. The KIVA-3V code was coupled with a reduced n...

Effect of multiple-injection strategies on diesel engine exhaust particle size and nanostructure

Multiple-injection has been widely investigated to simultaneously reduce diesel NOx and soot emissions. While the comprehensive understanding of the effects of multiple injection on exhaust PM physical characteristics is still lacking. Three injection modes, single main, pilot-main and main-post injections, were compared in this work. The main objective is to better understand the influence of pilot and post injections on particle size and nanostructure characteristics in diesel exhaust. Experimental tests have shown that, for the pilot-main injection case, less premixed combustion and more diffusion combustion occur compared with the single main injection, which promotes formation of soot nuclei and results in a significant increase of number and mass of particles with the diameter above 100nm. On the contrary, soot oxidation later in the combustion is improved due to the enhancement of gas mean temperature (GMT) and air/fuel mixing for the main-post injection case, which favors soot oxidation and leads to the decrease of particle number and diameter. A comparison of particle nanostructures for the pilot-main injection case and main-post injection case has been conducted, which indicates that both low in-cylinder temperature and relative short carbonization time lead to the particles of less carbonization level (short fringe length and large fringe tortuosity) for the pilot-main injection case. Particles exhibit highly ordered graphitic structure for the main-post injection case due to the increase of combustion duration and the enhancement of in-cylinder temperature during the later stage of combustion derived by post combustion, which presents potential negative effect on diesel particle filters (DPF) regeneration efficiency.

An Insight into the Effect of Advanced Injection Strategies on Pollutant Emissions of a Heavy-Duty Diesel Engine

An advanced numerical investigation has been carried out in order to study the effect of multiple injection strategies on Caterpillar heavy-duty diesel engine emissions. Both different injected fuel percentages for each pulse and several dwells between main and post phase were investigated via computational fluid dynamics (CFD) and large eddy simulation (LES). Two sets of simulations were taken into account for 10% and 20% exhaust gas recirculation (EGR) fractions. In the first one, the main injection was split into two identical phases, while in the second one into three pulses. Within each set, three strategies were considered, increasing the amount of fuel injected during the main and concurrently decreasing the post pulse. Overall, 48 simulations were employed, since four different dwells between the last phase of the main and post injection were considered. Results show that the pollutant emissions minimization has been obtained for the Schemes injecting 65% and 70% of fuel for both two and three split strategies, but for different values of dwell. In fact, emissions very close to each other for NOx and particulate matter have been reached for these cases. Reductions of about −30% and −71% were respectively obtained for NOx and soot in comparison with experimental emissions related to the single injection case.

Comparison of the effects of multiple injection strategy on the emissions between moderate and heavy EGR rate conditions: part 1-pilot injections

As vehicle emissions regulations have become stricter, improving injection strategies and using high EGR rates has become important to reduce engine-out emissions. Previous research has found that, a multiple injection strategy with a pilot or post injection has the potential to improve the distribution of the air-fuel mixture or oxidation. Thus, it is important to determine the effect of multiple injection strategies on the engine-out emissions. Especially, since the latest diesel engines have used high EGR rates to reduce NOx emission, the target of emissions is different from that of moderate EGR rate condition. Under heavy EGR rate condition, it is needed to improve combustion efficiency by reduction of CO and THC emissions. Therefore, in the first research as part 1, the effects of pilot injection on the engine-out emissions were systemically evaluated for two different EGR rate conditions (30% and 60%). The characteristics of the pilot injection were different between the two EGR rate conditions because the behavior of diesel combustion is significantly different when the EGR rate is changed. This research condition was investigated using varying injection parameters such as the timing and quantity of the pilot injection. The results show that each different pilot injection strategy was suggested between two EGR rate conditions to reduce engine-out emissions. Under moderate EGR rate condition, very earlier pilot SOI with large amount has the potential to reduce NOx and PM emissions simultaneously. On the other hand, under heavy EGR rate condition, the closest pilot SOI to main SOI has the potential to reduce CO and THC emissions.

Effects of multiple-injection strategies on overall spray behavior, combustion, and emissions reduction characteristics of biodiesel fuel

This study described the combustion and exhaust emissions characteristics of biodiesel fuel with multiple-injection strategies. Also, this investigation included the free spray characteristics and in-cylinder spray behaviors of the multiple-injection modes. Free spray and in-cylinder spray images were obtained from the spray visualization system. Combustion and exhaust emissions characteristics were analyzed using a single cylinder diesel engine with a displacement volume of 373.33 cm 3 and a compression ratio of 17.8. The exhaust emissions were analyzed using a smoke meter and an exhaust gas analyzer. A scanning mobility particle sizer (SMPS) was utilized to measure the particle number and size distribution of the nano-sized particle matter. It revealed that the injected spray before BTDC 25° developed toward the piston bowl region, and then progressed along the piston wall. When the biodiesel spray was injected at BTDC 25°, the spray targeted the piston lib. In single-injection combustion, the combustion pressure and rate of heat release at an injection timing of BTDC 30° dramatically decreased. These characteristics influenced on the decrease of the indicated mean effective pressure (IMEP) and the increase of soot, HC, and CO emissions because of the incomplete combustion. The multiple-injection modes showed a higher IMEP than the single-injection mode. In addition, the pilot injection strategy represented a higher IMEP than the split injection mode. The analysis of exhaust emissions characteristics of the multiple-injection modes showed that a short injection interval induced a decrease in soot, HC, and CO emissions, while NO x emission increased. On the other hand, when the multiple-injection modes applied to the diesel engine, particles with large sizes were significantly decreased compared to single-injection combustion.

Effect of Multiple Injection Strategies on the Spray Atomization and Reduction of Exhaust Emissions in a Compression Ignition Engine Fueled with Dimethyl Ether (DME)

This experimental research paper presents the effect of multiple injection strategies on the neat dimethyl ether (DME) fuel atomization and reduction of exhaust emission characteristics within a compression ignition (CI) engine. Pilot and split injections under various injection mass (minj) and timing (tinj) conditions as a multiple injection strategies were applied to reveal its effect on the improvement of spray atomization and the reduction of exhaust emissions in terms of spray tip penetration, Sauter mean diameter (SMD), rate of heat release (ROHR), indicated mean effective pressure (IMEP), and generation of exhaust emissions (such as CO, HC, NOX, and soot). These experimental results were then compared with those from diesel fuel cases. It was revealed that multiple injection strategies for DME fuels lead to poor atomization characteristics, because the second injection of fuel influences both the density and velocity of spray droplets at the points of measurement. This issue can be resolved by controlling the injection mass and the second injection timing, or by increasing the injection pressure. However, multiple injection strategies can achieve a simultaneous reduction of NOX and soot emissions in comparison to single injection results, and NOX emissions gradually decreased with the advance of the first injection timing without increasing soot emissions due to a lower C−H ratio. It was also observed that the concentrations of HC and CO emissions for DME are influenced by the first injection timing. For a retarded first injection timing (BTDC 20°), HC and CO emissions for DME indicated relatively low levels, in comparison to the single injection case.

Effect of Multiple Injection Strategies on the Emission Characteristics of Dimethyl Ether (DME)-Fueled Compression Ignition Engine

An experimental investigation was conducted to evaluate the effect of multiple injection strategies on the performance of DME-fueled engine and the reduction of exhaust emissions. In this work, three types of multiple injection strategiesincluding split injection, pilot injection, and partial premixed charge compression ignition (PPCCI)are introduced, and the results are compared with those obtained by single injection under optimal operating conditions. To analyze the injection characteristics of dimethyl ether (DME) fuel, the injection rate profiles for multiple injections were investigated, in terms of their energizing current and injection rate. The result of an engine test reveals that multiple injection strategies of split and pilot injection showed a reduction in NOx emissions of ∼75% with a minor reduction in the indicated mean effective pressure (IMEP). PPCCI combustion offered a reduction in NOx emissions of ∼97.1%, whereas the IMEP was reduced by 23%. Under all operating conditions, no measureable soot emission was observed in the DME engine.

Experimental investigation on the effect of multiple injection strategies on emissions, noise and brake specific fuel consumption of an automotive direct injection common-rail diesel engine

High-pressure common-rail injection systems nowadays allow a very high degree of flexibility in the timing and quantity control of multiple injections, which can be used to obtain significant reductions in engine noise and emissions. The aim of this study is to develop a better understanding of the relationship between injection strategies and the combustion and emission formation process. Some multiple injection strategies (pilot-pilot-main and pilot-main-after) have therefore been analysed to highlight their influence on the soot, NOx combustion noise and b.s.f.c. (brake specific fuel consumption) of a passenger car direct injection diesel engine prototype. Finally, the main combustion characteristics were determined, for each operating condition, on the basis of a heat release analysis and a correlation was attempted between the combustion parameters and emissions, noise and b.s.f.c.