Start Of Injection Timing Research Articles

Modeling and analysis of fuel injection parameters for combustion and performance of an RCCI engine

The Reactivity Controlled Compression Ignition (RCCI) is a promising dual-fuel Low Temperature Combustion (LTC) strategy that provides a precise means for controlling the heat release rate and combustion phasing. Optimum RCCI engine operation depends on optimum selection of fuel injection parameters. In this study, a detailed 3D/Computational Fluid Dynamics (CFD) combustion model in CONVERGE CFD code is developed and validated against experimental data at different engine operating conditions. Next, the effects of fuel injection parameters on the performance and emissions characteristics of an RCCI engine are analyzed. The fuel injection parameters include spray angle, injection pressure, Start of Injection (SOI) timing, and Premixed Ratio (PR). The baseline simulation results show that a proper selection of spray angle can cause significant reduction in HC and CO emissions, while improving combustion and gross indicated efficiencies. Furthermore, decreasing injection pressure and PR along with advancing SOI timing can improve the RCCI engine’s HC and CO emissions productions. The developed CFD model is then used in an extensive computational study to determine optimum fuel injection parameters for the best RCCI engine performance. The optimization results show that spray angle 55°, SOI=−53° aTDC, 580bar injection pressure, and PR=0.76 provide the best combination of four major fuel injection parameters for the speed and load conditions studied. By choosing this set of parameters, HC and CO emissions decrease by 23% and 39% from the baseline condition while a notable improvement is observed in gross indicated and combustion efficiencies.

Combustion, performance and emissions characteristics of a newly developed CRDI single cylinder diesel engine

For improving engine performance, combustion and controlling emissions from compression ignition (CI) engines, common rail direct injection (CRDI) technology offers limitless possibilities by controlling fuel injection parameters such as fuel injection pressure, start of injection (SOI) timing, rate of fuel injection and injection duration. CRDI systems available commercially are quite complex and use a large number of sensors, hardware and analytical circuits, which make them very expensive and unfeasible for cheaper single cylinder engines, typically used in agricultural sector and decentralized power sector.This paper covers experimental investigations of a simpler version of CRDI system developed for a constant-speed, single-cylinder engine. Modifications in the cylinder head for accommodating solenoid injector, designing injector driver circuit and development of high pressure stage controls were some of the engine modification and development tasks undertaken. SOI timing is an important parameter for improving engine’s combustion characteristics. SOI timings were varied between 25° and 40° BTDC for investigating engine’s performance, emissions and combustion characteristics. Advanced fuel injections showed higher heat release rate (HRR), cylinder pressure and rate of pressure rise (RoPR) because of relatively longer ignition delay experienced. Lowest brake specific fuel consumption (BSFC) was obtained for 34° CA BTDC SOI. Reduction in engine out emissions except NOx was observed for advanced fuel injection timings for this newly developed CRDI system.

Effects of diesel injection strategy on natural gas/diesel reactivity controlled compression ignition combustion

The effects of diesel injection strategies on the combustion and pollutant emission characteristics of a modified heavy-duty reactivity controlled compression ignition engine fueled with natural gas/diesel are studied. Natural gas with low reactivity is assumed to be inducted into the engine through the intake port, while diesel fuel with high reactivity is directly injected into the engine using a double injection strategy. Several parameters were studied including the premixed natural gas amount, the first and second injection timings and the injected diesel mass split between the two injections. The results showed improved engine efficiency with reductions in soot and oxides of nitrogen emissions could be achieved with the injection strategies studied, but hydrocarbons and carbon monoxide emissions were deteriorated. Three factors, namely first start of injection timing, second start of injection timing and the diesel injection fuel fractions, had pronounced effects on reactivity controlled compression ignition engine combustion performance and emissions. To reduce soot and oxides of nitrogen emissions, increasing the natural gas percentage, advancing first and second starts of injection timing beyond a certain point and increasing fuel fraction in first start of injection timing are preferred, but they had an adverse effect on hydrocarbons and carbon monoxide emissions.

Nonlinear Model Predictive Control of Integrated Diesel Engine and Selective Catalytic Reduction System for Simultaneous Fuel Economy Improvement and Emissions Reduction

The applications of diesel engines in ground vehicles have attracted much attention over the past decade for the reasons of outstanding fuel economy, power capability, and reliability. With the increasing demand of less greenhouse gas emissions, the current diesel engine fuel efficiency remains unsatisfactory partially due to the conflict between the engine fuel efficiency and engine-out NOx emissions. While advanced aftertreatment systems, such as selective catalytic reduction (SCR) systems or lean NOx trap, have been integrated to diesel engines for reducing the tailpipe NOx emissions, the integrated controls for coordinating diesel engine and SCR system to achieve high engine efficiency and low tailpipe emissions are still limited. The purpose of this study is to develop such an integrated diesel engine and SCR system control method using nonlinear model predictive control (NMPC) approach with both start of injection (SOI) timing and urea solution injection rate as the control inputs. Control-oriented engine models were developed to quantify the influences of SOI timing on engine efficiency and engine-out NOx emissions. Simulation results under US06 driving cycle demonstrate that, given the same catalyst size in total, the proposed controllers are capable of reducing total engine fuel consumption over the driving cycle by 9.36% and 9.50%, respectively, for lumped SCR system and two-cell SCR system, while maintaining high NOx conversion efficiencies and low tailpipe ammonia slip.

Effects of fuel ratio and injection timing on gasoline/biodiesel fueled RCCI engine: A modeling study

RCCI (reactivity controlled compression ignition) has drawn much attention since it was proposed, as it could lead to high performance and clean combustion. The original concept of an RCCI engine is to use gasoline and diesel as the low and high reactivity fuels, respectively. In this study, biodiesel is considered as a substitute of diesel. Hence, research was numerically conducted on a gasoline/biodiesel fueled RCCI engine. To simulate the combustion process, coupled KIVA4–CHEMKIN was used. The gasoline/biodiesel reaction mechanism as implemented in the code was developed by the authors. Two major factors, namely gasoline to total input energy ratio and SOI (start of injection) timing, have been considered. The varied gasoline energy ratios were applied to both C-SOI (conventional SOI) and A-SOI (advanced SOI) timings. Comparing the combustion characteristics between two SOI timings with varied gasoline energy ratios, it is found that A-SOI could offer more controllability on start of combustion, combustion phasing etc. when varying gasoline ratio. As for the emissions formation, increases in gasoline could reduce NOx and soot emissions simultaneously by achieving more homogeneous combustion. However, the designed spray angle of 78° for C-SOI, when used with A-SOI, would increase the soot formation especially when more biodiesel is injected.

Computational Fluid Dynamics Simulation of Gasoline Compression Ignition

Gasoline compression ignition (GCI) is a low temperature combustion (LTC) concept that has been gaining increasing interest over the recent years owing to its potential to achieve diesel-like thermal efficiencies with significantly reduced engine-out nitrogen oxides (NOx) and soot emissions compared to diesel engines. In this work, closed-cycle computational fluid dynamics (CFD) simulations are performed of this combustion mode using a sector mesh in an effort to understand effects of model settings on simulation results. One goal of this work is to provide recommendations for grid resolution, combustion model, chemical kinetic mechanism, and turbulence model to accurately capture experimental combustion characteristics. Grid resolutions ranging from 0.7 mm to 0.1 mm minimum cell sizes were evaluated in conjunction with both Reynolds averaged Navier–Stokes (RANS) and large eddy simulation (LES) based turbulence models. Solution of chemical kinetics using the multizone approach is evaluated against the detailed approach of solving chemistry in every cell. The relatively small primary reference fuel (PRF) mechanism (48 species) used in this study is also evaluated against a larger 312-species gasoline mechanism. Based on these studies, the following model settings are chosen keeping in mind both accuracy and computation costs—0.175 mm minimum cell size grid, RANS turbulence model, 48-species PRF mechanism, and multizone chemistry solution with bin limits of 5 K in temperature and 0.05 in equivalence ratio. With these settings, the performance of the CFD model is evaluated against experimental results corresponding to a low load start of injection (SOI) timing sweep. The model is then exercised to investigate the effect of SOI on combustion phasing with constant intake valve closing (IVC) conditions and fueling over a range of SOI timings to isolate the impact of SOI on charge preparation and ignition. Simulation results indicate that there is an optimum SOI timing, in this case −30 deg aTDC (after top dead center), which results in the most stable combustion. Advancing injection with respect to this point leads to significant fuel mass burning in the colder squish region, leading to retarded phasing and ultimately misfire for SOI timings earlier than −42 deg aTDC. On the other hand, retarding injection beyond this optimum timing results in reduced residence time available for gasoline ignition kinetics, and also leads to retarded phasing, with misfire at SOI timings later than −15 deg aTDC.

Effect of fuel injection pressure and injection timing of Karanja biodiesel blends on fuel spray, engine performance, emissions and combustion characteristics

In this investigation, effect of 10%, 20% and 50% Karanja biodiesel blends on injection rate, atomization, engine performance, emissions and combustion characteristics of common rail direct injection (CRDI) type fuel injection system were evaluated in a single cylinder research engine at 300, 500, 750 and 1000bar fuel injection pressures at different start of injection timings and constant engine speed of 1500rpm. The duration of fuel injection slightly decreased with increasing blend ratio of biodiesel (Karanja Oil Methyl Ester: KOME) and significantly decreased with increasing fuel injection pressure. The injection rate profile and Sauter mean diameter (D32) of the fuel droplets are influenced by the injection pressure. Increasing fuel injection pressure generally improves the thermal efficiency of the test fuels. Sauter mean diameter (D32) and arithmetic mean diameter (D10) decreased with decreasing Karanja biodiesel content in the blend and significantly increased for higher blends due to relatively higher fuel density and viscosity. Maximum thermal efficiency was observed at the same injection timing for biodiesel blends and mineral diesel. Lower Karanja biodiesel blends (up to 20%) showed lower brake specific hydrocarbon (BSHC) and carbon monoxide (BSCO) emissions in comparison to mineral diesel. For lower Karanja biodiesel blends, combustion duration was shorter than mineral diesel however at higher fuel injection pressures, combustion duration of 50% blend was longer than mineral diesel. Up to 10% Karanja biodiesel blends in a CRDI engines improves brake thermal efficiency and reduces emissions, without any requirement of hardware changes or ECU recalibration.

Effect of hydrogen peroxide addition to methane fueled homogeneous charge compression ignition engines through numerical simulations

The effect of the direct injection of hydrogen peroxide into a port-injected methane fueled homogeneous charge compression ignition engine was investigated numerically. The injection of aqueous hydrogen peroxide was implemented as a means of combustion phasing control. A single-cylinder homogeneous charge compression ignition engine (2.43 L Caterpillar) was modeled using the Cantera 2.0 flame code toolkit, the GRI-Mech 3.0 chemical reaction mechanism, and a single-zone slider-crank engine model. Start of injection timing and the amount of injected hydrogen peroxide were manipulated to achieve desired combustion phasing under a wide range of intake temperatures. As the concentration of hydrogen peroxide is increased, the combustion phasing is advanced up to 22° for the conditions investigated in this study. This advancing effect is most pronounced at small concentrations (<10 g H2O2/kg CH4) and early injection timings (start of injection < 25° before top dead center). The model suggests hydrogen peroxide can be introduced as a means of combustion phasing control while maintaining the low emissions and peak in-cylinder pressures inherent in homogeneous charge compression ignition engines.

Fuel System Response of a Common Rail Passenger Car Engine Fuelled with Palm Oil Biodiesel

This study investigated the effects of palm oil methyl ester blends on a common rail passenger car engine in terms of changes in the fuel system response. Up to 40% biodiesel blend was used in this study. Operating on biodiesel causes the engine control system to modify the injection parameters by increasing the injection pressure and duration while advancing the start of injection timing for the same power output. This engine control system-response to biodiesel is due to the inherent low energy density of biodiesel. Low and medium speed/load region was proposed as an area where improvement by injection strategies optimization can be made.

Study on RCCI (reactivity controlled compression ignition) engine by means of statistical experimental design

Recently some studies have been carried out on RCCI (reactivity controlled compression ignition) engines; however, they routinely used the “one factor at a time” approach, which may neglect interactions among the manipulated factors. This paper reports the use of a more effective approach based on fractional factorial design to investigate the way that injection strategy might affect performance and emissions formation of such engines. In this work, six factors, namely the first SOI (start of injection) timing, the first ID (injection duration), the second SOI timing, the second ID, the diesel mass fraction in the first injection and the ratio of natural gas to total air, were considered. Sixteen simulated runs were conducted to evaluate the performance and emissions of an engine by using coupled KIVA4–CHEMKIN code with detailed reaction mechanism. The results show that premixed natural gas, which is the most dominant one, has a positive correlation with indicated power, and could reduce CO (Carbon Monoxide), NOx (Nitrogen Oxides) and soot emissions simultaneously. To further reduce NOx, both retarded second SOI timing and extended second ID are suggested. Finally, sequential studies are suggested to the direction with higher percentages of premixed low cetane number fuel.

Effects of direct injection timing of ethanol fuel on engine knock and lean burn in a port injection gasoline engine

Ethanol is a promising alternative fuel for internal combustion engines due to its renewable feature. To make the use of ethanol fuel more effective and efficient, ethanol direct injection plus gasoline port injection (EDI+GPI) has been investigated in recent years. By directly injecting ethanol into the engine, the advantages of ethanol fuel such as high latent heat of vaporization, fast laminar flame speed, wide flammability and better low temperature combustion stability can be well utilized to enhance engine anti-knock ability and improve lean burn performance. For an engine equipped with direct injection (DI) system, start of injection (SOI) timing is an important control parameter which directly affects the engine performance. This paper reports the investigation to the effect of ethanol fuel SOI timing on knock mitigation and lean burn. Experiments were conducted on a 250cc single cylinder spark ignition (SI) engine equipped with EDI+GPI system. Ethanol fuel SOI timing before and after the inlet valve closing, defined as early and late injection timings (EEDI and LEDI) were investigated in engine conditions at knock limited spark advance (KLSA) and lean burn limit. The experimental results showed that LEDI was effective on suppressing engine knock and permitting more advanced spark timing. EEDI was less effective than LEDI on mitigating knock due to the increased heat transfer from cylinder wall to gases. The mixture quality may be deteriorated in LEDI conditions which resulted in low engine efficiency and high emissions. Volumetric efficiency was increased and combustion duration was reduced in EEDI conditions. The combined effects of improved volumetric efficiency, reduced combustion duration and moderately advanced spark timing resulted in increased engine thermal efficiency in EEDI conditions. In lean burn, EEDI was more effective on extending lean burn limit. The maximum lambda achieved in EEDI condition was 1.29 when ethanol energy ratio (EER) was 24% and SOI timing was 290 CAD BTDC. LEDI only slightly increased lean burn limit which was just over stoichiometric air–fuel ratio (AFR). In EEDI conditions, IMEP was greater and combustion stability (COV) was better than that in LEDI conditions. The emissions in EEDI conditions were also lower than that in LEDI conditions.

Effect of fuel injection pressure and injection timing on spray characteristics and particulate size–number distribution in a biodiesel fuelled common rail direct injection diesel engine

In this paper, effect of varying fuel injection pressures and injection timings on particulate size number distribution and spray characteristics was investigated in a single cylinder, common rail direct injection (CRDI) compression ignition (CI) engine fueled with Karanja biodiesel blends vis-à-vis baseline mineral diesel. The investigation results of spray tip penetration and spray area of biodiesel blends and diesel showed that higher fuel injection pressure result in a longer spray tip penetration and larger spray area than that at lower injection pressures at same elapsed time after the start of injection (SOI). In order to compare the effect of fuel injection parameters, 10, 20 and 50% Karanja biodiesel blends at 1500rpm engine speed were compared with baseline data from mineral diesel. It was observed that average particulate size increased with retarding the SOI timings. Particulate number concentration was lowest for 10% biodiesel blend, which increased with further increase in biodiesel content in the blended test fuel. Addition of even very small quantity of biodiesel in the test fuel helped in reducing particulate emissions.

An evaluation of cetane sensitivity in low-temperature combustion and options to compensate for market cetane variation

A single-cylinder engine was used to assess the sensitivity of emissions, noise and fuel consumption to variation in cetane number when operated in low temperature combustion both with and without the application of compensation strategies. Without compensation, changes in cetane caused greater variability in all of the parameters studied when operated in low temperature combustion as compared to conventional diesel combustion. Correcting combustion phasing was explored by adjusting three different parameters: start of injection timing, burnt gas fraction and intake manifold temperature. None of these methods were able to achieve substantially equivalent combustion and emissions across all fuels evaluated. Large variations in hydrocarbon and particulate emissions were observed when start of injection was adjusted to correct combustion phasing. Adjusting the burnt gas fraction caused large differences in nitrogen oxides and noise, particularly with low cetane fuels. Finally, intake manifold temperatures low enough to reach the target combustion phasing with the higher cetane fuel were unachievable, suggesting that this method would not be viable as a production solution. It was concluded that the most effective way to ensure robust combustion and emissions in low temperature combustion is to reduce ignition delay variability by refining the fuel specification, either through tighter control over the cetane number range or by shifting the fuel specification toward higher cetane number, where ignition delay is less sensitive to changes in cetane rating.

Experimental investigation of diesel and biodiesel post injections during active diesel particulate filter regenerations

The purpose of this study is to investigate the common-rail diesel engine and aftertreatment system behaviors during active diesel particulate filter (DPF) regenerations with pure biodiesel and conventional diesel fuels. The experiments were conducted on a medium-duty diesel engine equipped with a high pressure common-rail fuel injection system. The comparative effects of post start of injection (SOI) timing, post fuel injection rate, and the number of post injections, on the engine behaviors including exhaust emissions (total hydrocarbon (THC), carbon monoxide (CO), and oxides of nitrogen (NOx)), exhaust gas temperatures, torque output, and the THC and CO conversion efficiencies inside a diesel oxidation catalyst (DOC), are presented and discussed. Experimental results show that, for both fuels, the engine-out THC emissions at late post injection timings are significantly higher than that at early post injection timings, while the engine-out CO emissions reach the peak values in mid phase of power strokes and the engine-out NOx emissions can be reduced with a late-cycle post injection. Engine torque output and cylinder-out gas temperatures can be promoted obviously with an early post injection. Post injection rate is the dominant factor influencing the exhaust emissions at fixed post SOI timings. Regarding the main differences between the two fuels, substantially lower engine-out THC and CO emissions can be observed from late post injection with biodiesel than those with diesel. The addition of an early post injection to a late post injection has little effect on the engine-out THC emissions, but can lead to higher engine-out CO emissions and higher cylinder-out gas temperatures. Furthermore, substituting diesel with biodiesel in the engine can lower the cylinder-out gas temperature, the engine torque disturbance, and the THC and CO conversion efficiencies inside the DOC.

실험계획법에 의한 가솔린 GDI+MPI 엔진의 연비 및 성능향상 관점에서의 운전영역별 연료분사 전략에 관한 연구

The gasoline direct injection (GDI) system is considerably spreading in automotive market due to its advantages. Nevertheless, since GDI system emit higher particle matter (PM) due to its combustion characteristics, it is difficult to meet strengthened emission regulation in near future. For this reason, a combined GDI with MPI system, so-called, dual injection (DUI) system is being investigated as a supplemental measure for the GDI system. This paper focused on power and fuel consumption effect by injection mode strategy of DUI system in part load and idle engine operating condition. In this study, port fuel injectors are installed on 2.4 liters GDI production engine in order to realize DUI system. And, at each injection mode, DOE (design of experiment) method is used to optimize engine control parameters such as dual injection ratio, start of injection timing, end of injection timing, CAM position and so on. As a consequence, DUI mode shows slightly better or equivalent fuel efficiency compared to conventional GDI engine on 9 points fuel economy mode as well as MPI mode shows less fuel consumption than GDI mode during idle operation. Furthermore, DUI system shows improvement potential of maximum 2.0% fuel consumption and 1.1% performance compared to GDI system in WOT operating condition.

Modeling study of soot formation and oxidation in DI diesel engine using an improved soot model

Particulate emission is one of the most deleterious pollutants generated by Diesel fuel combustion. The ability to predict soot formation is one of the key elements needed to optimize the engine performance and minimize soot emissions. This paper reports work on developing, a phenomenological soot model to better model the physical and chemical processes of soot formation in Diesel fuel combustion. This hybrid model features that the effect of turbulence on the chemical reaction rate was considered in soot oxidation. Soot formation and oxidation processes were modeled with the application of a hybrid method involving particle turbulent transport controlled rate and soot oxidation rate. Compared with the original soot model, the in-cylinder pressures, heat release rate and soot emissions predicted by this hybrid model agreed better with the experimental results. The verified hybrid model was used to investigate the effect of injection timing on engine performance. The results show that the new soot model predicted reasonable soot spatial profiles within the combustion chamber. The high temperature gas zone in cylinder for hybrid model case is distributed broadly soot and NOx emission dependence on the start-of-injection (SOI) timing. Retarded SOI timing increased the portion of diffusion combustion and the soot concentration increased significantly with retarding of the fuel injection timing. The predicted distributions of soot concentration and particle mass provide some new insights on the soot formation and oxidation processes in direct injection (DI) engines. The hybrid phenomenological soot model shows greater potential for enhancing understanding of combustion and soot formation processes in DI diesel engines.

CFD modelling of soot entrainment via thermophoretic deposition and crevice flow in a diesel engine

Combustion soot entrainment into engine oil has been linked to oil starvation and damage of the engine piston. In this computational work, the direct impact of different injection strategies on the spatial evolution of combustion soot and the soot entrainment process in a light-duty diesel engine is examined. Here, the main focus is on the thermophoretic soot deposition on the cylinder liner as well as soot transport into the crevice region via blowby. Numerical simulation of in-cylinder diesel combustion is performed using a commercial Computational Fluid Dynamics (CFD) software, ANSYS FLUENT 13, coupled with a chemical kinetic model via a plug-in chemistry solver, CHEMKIN-CFD. A chemical reaction mechanism of n-heptane combined with soot precursor formation mechanism is adopted as the diesel surrogate fuel model, with the Eddy-Dissipation Concept (EDC) model employed to represent the turbulence-chemistry interaction. The inclusion of a top land volume in the computation mesh and the implementation of crevice model in the CFD solver allow soot mass to be predicted in this region, which is used here to represent the soot mass transport into the crevice via blowby. With thermophoresis as the primary mechanism of soot deposition on the liner, a User-Defined Function (UDF) is written to incorporate the transport equations for the calculations of the mass and particle size of soot deposited. During the closed cycle combustion process, the mass of soot deposited on liner via thermophoresis is more significant, averaging to between 17 and 170 times of those transported into crevice region through blowby. Other than the soot concentration near the liner, thermophoretic deposition is observed to be also affected by the wall temperature gradient. With single injection strategy, advancement in the start of injection (SOI) timing from +2 crank angle degrees (CAD) to −6 CAD after top dead centre (ATDC) is found to reduce soot entrainment by 22% and the size of deposited soot particles by 4%. The adoption of split-main injection scheme with early injection reduces the quantity and size of the entrained soot as the fuel split ratio is lowered. However, the split injection scheme produces an opposing effect at late SOI timing, where the smallest quantity and size of the entrained soot is produced. Variation in the injection strategy is found to affect the soot entrainment process by influencing the in-cylinder gas motion, the location of combustion event and the evolution of soot cloud. This study provides a detailed insight into the effects of injection parameters on key in-cylinder processes governing soot entrainment, which can potentially help in formulating engine operating guidelines to mitigate soot-in-oil problem.

Parametric study of instantaneous heat transfer based on multidimensional model in direct-injection hydrogen-fueled engine

This paper presents a parametric study on instantaneous heat transfer of a direct-injection hydrogen-fueled engine using a multidimensional model. A simplified single-step mechanism was considered for estimating the reaction rate of hydrogen oxidation. The modified wall-function was used for resolving the near-wall transport. An arbitrary Lagrangian–Eulerian algorithm was adopted for solving the governing equations. Experimental measurements were implemented to verify the developed model. They show that the instantaneous heat-transfer model is sufficiently accurate. The influence of engine speed, equivalence ratio, and the start of injection timing were investigated. The flow fields appeared to have greater size vectors and coarser distribution with an increase of engine speed. A heterogeneous distribution was obtained for an ultra-lean mixture condition (φ ≤ 0.5), which decreased with an increase of equivalence ratio. There was no pronounced influence of the start of injection on the flow field pattern and mixture homogeneity. Thermal field analysis was used to demonstrate trends in the instantaneous heat transfer. It was observed that there was a crucial distinction between the lean and ultra-lean mixtures as well as the engine speed. Furthermore, a non-uniform behavior was found for the impact of the equivalence ratio on temperature distribution. It is clear that the developed models are powerful tools for estimating the heat transfer of the hydrogen-fueled engine. The developed predictive correlation is highly accurate in predicting the heat transfer of the hydrogen-fueled engine, focusing on the equivalence ratio as a governing variable.

Effect of fuel injection pressure on diesel particulate size and number distribution in a CRDI single cylinder research engine

Particulate and NOx emissions from diesel engine are the biggest challenges faced in making diesel engines environmentally benign. Measures adopted for reducing gravimetric particulate emission to meet the prevailing emission regulations necessarily always do not reduce particulate number concentration, which has profound adverse health effects. Therefore it is important to investigate effect of fuel injection parameters, especially fuel injection pressure and start of injection timings on particulate size and number distribution in diesel exhaust. In the present study, a single cylinder research engine is used for experimental assessment of the effects of fuel injection strategies and start of fuel injection timing on particulate size–number, surface area, and volume concentration distributions by using engine exhaust particulate sizer (EEPS) spectrometer. Investigations have been conducted at three different fuel injection pressures (300, 500, 750bar) and four different start of injection timings. The experimental data indicates that the particulate size–number concentration increases with increasing engine load (BMEP) and it reduces with increasing fuel injection pressure.

Impact of engine operating modes and combustion phasing on the reactivity of diesel soot

The present work focuses on the impacts of engine operating conditions and combustion phasing on diesel soot properties. The study was carried out in a 2.5L direct injection common-rail turbodiesel engine using an ultra low sulfur diesel fuel (BP15). The study has two objectives. The first objective is to investigate the reactivity difference of the soot generated at four engine modes, spanning conditions of most interest in the engine operating map. The results show that the impact of engine speed at constant torque is more pronounced than the impact of engine torque (equivalence ratio) at constant engine speed. The effect of the engine torque at constant engine speed, especially at higher speed, is not observable in this experiment. The second objective is to investigate the reactivity and nanostructure of soot generated at different combustion phasing by advancing and retarding the fuel start of injection (SOI) timing. Reaction kinetics obtained from thermogravimetric analysis show that the rate constant of the sample for retarding SOI timing (retarded 2 CAD) is 2.3 times that for advancing SOI timing (advanced 2 CAD). In summary, the results presented here provide unique insights into the methodology that should be used when investigating soot samples generated by different fuels: matching operating modes and combustion phasing for different fuels is suggested while collecting soot samples for characterization.