Post Injection Timing Research Articles

A novel approach of in-cylinder NOx control by inner selective non-catalytic reduction effect for high-pressure direct-injection ammonia engine

As an efficient hydrogen carrier and carbon-free fuel, ammonia shows great promise in realizing zero-carbon propulsions. However, challenges such as poor ignition stability, low combustion efficiency, and fuel-NOx emissions are yet to overcome. In this paper, the high-pressure direct-injection ammonia/diesel dual-fuel combustion mode (HPDF) with post injection strategy is proposed as a solution. The study reveals that HPDF combustion mode enables in-cylinder reduction of NOx, which is attributed to the selective non-catalytic reduction (SNCR) reaction. The results uncover that NH2, NH, and N radicals have a significant reducing effect on NO and NO2, while N2O serves as an important byproduct of the reduction reactions. Subsequently, the generated N2O can be further reduced to N2 through the involvement of O, H, and OH radicals. Building upon these findings, an innovative ammonia post injection method for reducing NOx emissions is explored. The post injection strategy effectively reduces the NOx emissions with only a minor decrease in indicated thermal efficiency, but an over-delayed post injection could also cause significant increase in N2O and unburned NH3 emissions. A post injection proportion of 20%-30% with appropriate post injection timing is found to achieve desired emission reduction. Overall, the HPDF combustion mode is a promising solution for ammonia engine, due to the high thermal efficiency and low nitrogen oxide emissions, as well as the ability to further reduce the NOx emissions through ammonia post injection strategy.

Combination of high cetane diesel fuel and post injection mode in a diesel engine: A path towards lower exhaust emissions

The major objective of the presented work is to explore the effect of post injection (PI) strategy using neat diesel fuel (D100) blended with cetane number enhancer (CNE). The motive behind adding CNE in diesel fuel was to lower its self-ignition temperature and hence delay period subsequently. This can lead to more efficient combustion of post injected fuel which leads to lower incomplete combustion losses. The CNE used was Di-Tert-Butyl Peroxide (DTBP) which was blended with D100 in proportion of 1 % by volume. Initially experiments were conducted with D100 under various PI modes where variation of post injection timing (PIT) as well as post quantity (PQ) was considered. The experimental results showed that implementing PI resulted in lower smoke, unburned hydrocarbon (UHC), carbon monoxide (CO) and nitrogen oxides (NOx) emissions compared to single injection while affecting fuel consumption negatively. Then after similar experiments under various PI modes were repeated using blends of D100 and DTBP (D/DTBP) and results were compared with D100 case. It was found that addition of CNE in D100 resulted in more complete combustion of post fuel which further reduced CO and UHC emissions. The shorter delay period in case of D/DTBP blend compared to D100 case led to lower NOx emissions as well as higher smoke emissions. The obtained results revealed that PI mode with 3 mg PQ and 20° after top dead center (ATDC) PIT with D/DTBP blend offered 41.18 %, 17.55 %, 64 % and 62.5 % reduction in smoke, NOx, UHC and CO emissions respectively compared to single injection mode using D100 fuel.

Study on partial oxidation phenomena of post-injection fuel in diesel engines

In diesel engines, post fuel is injected in the expansion stroke, oxidized by the diesel oxidation catalysts and the high temperature gas re-generates the diesel particulate filters. However, it is empirically known that the post fuel at advanced injection timing is partially oxidized in the cylinder due to the high temperature-pressure conditions and it is a cause of the reduction of fuel consumption. The purpose of this research is to analyze post-injection fuel behaviors in cylinder and investigate the optimum fuel injections that maximize the unburnt hydrocarbons to the diesel oxidation catalysts. The engine employed in this research is a turbo charged 2.0 L four-cylinder DI diesel engine with two fuel injection systems to change the heterogeneity of air-fuel mixture and temperature distributions in cylinder; n-hexane is injected in the intake manifold to produce the homogeneous air-fuel mixture and diesel fuel is directly injected into the cylinder. The partial oxidation ratio of post fuel and the fuel loss mainly by fuel adhesion was calculated by injected fuel quantity, air quantity, and emission data. The 3D-CFD software was introduced to analyze the partial oxidation of post fuel and flow in the cylinder. The heterogeneity of burned gas mixture of post injection atmosphere and the post-injection timings were the parameters of engine tests and 3D-CFD simulations. The results suggest that the heterogeneity of equivalence ratio and the non-uniformity of gas temperature inside the cylinder at the start of post injection affect the partial oxidation of post-injection fuel. The more homogeneous these conditions are, the better the suppression of partial oxidation of post-injection fuel and the avoidance of fuel adhesion to the cylinder wall can be achieved.

Investigating the potential of a higher reactivity fuel to achieve faster heat-up of aftertreatment systems

Shortening the aftertreatment system heat-up period will be crucial to meet upcoming emissions regulations, which mandate significant reductions in tail-pipe emissions for on-road heavy-duty vehicles. This work studies the impact of increasing fuel reactivity on the combustion of post injections during the expansion stroke. The work demonstrates an operating strategy using a blend of di-butyl ether (a potential low-carbon biofuel component) and #2 diesel that achieves higher exhaust enthalpy, while maintaining similar engine-out emissions (NOx and combustion efficiency) in comparison to the baseline #2 diesel fuel (cetane number 41). On average, a 12% increase in exhaust enthalpy was observed for the blend (cetane number 60) relative to the baseline fuel. The ability to operate the higher reactivity fuel at a more retarded post-injection timing, where combustion with #2 diesel was found to be more unstable, and less complete was key to achieving higher exhaust enthalpy. However, a small fuel penalty (∼ 3%–5%) was also associated with the higher reactivity fuel with this operating strategy. The formation of fuel lean regions, due to the long ignition delays at late injection conditions, was predicted to be the leading contributor to the increased emissions of products of partial combustion. Chemical kinetic simulations using surrogates for the fuels used in the experiments, demonstrated the ability of a higher cetane fuel to outperform the baseline fuel under fuel lean conditions with equivalence ratios less than 0.7.

Errors in measurement of glomerular filtration rate using the slope-intercept technique and their identification.

GFR measured from plasma sampling may be expressed as slope-intercept GFR (SI-GFR) and scaled to body surface area (mGFR/BSA) or as GFR per unit extracellular fluid volume (mGFR/ECV), which is based only on half-time. Measurement errors comprise 3 categories. Pre-injection error arises from error in administered marker and is suspected when mGFR/BSA and mGFR/ECV disagree. Injection errors include 'tissued' injections. Post-injection errors include inaccurate sample timing, inaccurate pipetting, sample haemolysis and sampling through long IV lines through which marker was administered. The aim of the study was to evaluate the impact of errors on mGFR. We compared mGFR/BSA with mGFR/ECV in 898 patients undergoing routine investigation. To investigate post-injection error, we took two further patient datasets with r values (correlation coefficient of the 3-sample fit) of 1.0 and introduced errors, in isolation, into each of the 3 recorded sample values, as follows: pipetting (volume) errors of -20%, -10%, -5%, 5%, 10% and 20%, and timing errors of -15 min, -10 min, -5 min, 5 min, 10 min and 15 min. The correlation between mGFR/BSA and mGFR/ECV was close and independent of r. Post-injection error depended on the time of the sample in which it occurred. r correlated poorly with error magnitude for both volume and timing errors. When a 'rogue' sample is suspected its error needed to be substantial for it to be identified by single sample estimates applied to the other samples. SI-GFR is resistant to post-injection timing and volume errors but not to pre-injection error.

Formation of CH2O and UHC emissions during catalyst-heating operation in compression ignition engines: High-speed FID and mid-IR extinction diagnostics

To comply with increasingly stringent pollutant emissions regulations, catalyst-heating operation in diesel engines is critical to achieving rapid light-off of exhaust aftertreatment catalysts during the first minutes of cold start. Current approaches to catalyst-heating operation typically involve one or more late post injections to retard combustion phasing and increase exhaust gas temperatures. The ability to retard post injection timings while maintaining acceptable pollutant emissions levels is pivotal for improved catalyst-heating operations. This experimental study aims to provide further insight into unburned hydrocarbons (UHC) and formaldehyde (CH2O) formation under catalyst-heating operation.In this study, high-speed laser extinction based measurements of CH2O are demonstrated in an optically accessible exhaust runner, and high-speed UHC measurements are also performed using a fast flame ionization detector analyzer during catalyst-heating operation. Time-resolved CH2O and UHC emission measurements are used to analyze the effect of each injection event in a five-injection strategy (two pilots, one main and two posts) on the pollutant emissions. The first pilot injection generates a significant amount of UHC unevenly distributed in the chamber, with UHC trapped primarily in the upper-cylinder and inside-the-bowl regions. The fuel delivered with the second pilot injection partially burns the unburned fuel from the first pilot injection particularly in inner-bowl region, creating short-chain hydrocarbons corresponding to formation of CH2O. UHC is dramatically reduced in the presence of the main injection, reinforcing the hypothesis by showing large CH2O emission during intermediate and later exhaust process. The first post injection produces UHC and CH2O in the upper-cylinder area due to over-mixing, which is further promoted by the second post injection, while these post-injections do not substantially affect near-bowl emissions.

An Experimental and Computational Study on Triple Injection Strategies to Reduce Cold Start Diesel Engine Emissions

Abstract The effect of triple injection strategies in a diesel engine to reduce cold start emissions were experimentally and computationally investigated in this work. The experiments were performed using a 1.9 L four-cylinder, turbocharged compression ignition engine with diesel fuel. As a representative of the cold start condition in the diesel engine, a low load condition of 1500 rpm and 2 bar brake mean effective pressure (BMEP) was chosen as the fixed condition for this study. The injection strategy made use of a late post injection to reduce catalyst light-off time. The pilot and main injections are fixed and the post injection timing is swept later into the expansion stroke to increase exhaust enthalpy available to heat the aftertreatment system. To further understand the source of hydrocarbon (HC) emissions from late injections, equivalent experiments were conducted with a mixture of n-heptane and iso-octane that matched the reactivity of the diesel fuel. The mixture of primary reference fuels (i.e., PRF 34) obtained by matching the cetane number (CN) of diesel fuel, showed similar combustion characteristics of diesel, but is much more volatile due to lighter components in the PRF mixture. The increased volatility of PRF 34 suppressed liquid fuel impingement on the cylinder liner, which isolated liner impingement as a possible source of HC emissions. Simulations were also performed for the present engine configuration and operating conditions in a sector mesh using CONVERGE™. The physical properties of diesel fuel were modeled using a five-component surrogate. The chemical kinetics of the diesel fuel were modeled with a reduced n-heptane model. The simulations were able to capture the experimental trends of combustion characteristics and emissions. The HC emissions were observed to increase for both fuels with retarded post injection timings in engine experiments. PRF 34 had comparable HC emissions to diesel experiments, which indicated that the liner impingement is not the main source of the increase in HC emissions. Overmixing of the fuel and air was identified as the major cause of increase in HC emissions. Additionally, exhaust gas recirculation (EGR) also intensified the overmixing phenomenon and thereby increase in HC emissions.

Timing of hypoxia PET/CT imaging after 18F-fluoromisonidazole injection in non-small cell lung cancer patients

Positron emission tomography (PET)/computed tomography (CT) using the radiotracer 18F-Fluoromisonidazole (FMISO) has been widely employed to image tumour hypoxia and is of interest to help develop novel hypoxia modifiers and guide radiation treatment planning. Yet, the optimal post-injection (p.i.) timing of hypoxic imaging remains questionable. Therefore, we investigated the correlation between hypoxia-related quantitative values in FMISO-PET acquired at 2 and 4 h p.i. in patients with non-small cell lung cancer (NSCLC). Patients with resectable NSCLC participated in the ATOM clinical trial (NCT02628080) which investigated the hypoxia modifying effects of atovaquone. Two-hour and four-hour FMISO PET/CT images acquired at baseline and pre-surgery visits (n = 58) were compared. Cohort 1 (n = 14) received atovaquone treatment, while cohort 2 (n = 15) did not. Spearman’s rank correlation coefficients (ρ) assessed the relationship between hypoxia-related metrics, including standardised uptake value (SUV), tumour-to-blood ratio (TBR), and tumour hypoxic volume (HV) defined by voxels with TBR ≥ 1.4. As the primary imaging-related trial endpoint used to evaluate the action of atovaquone on tumour hypoxia in patients with NSCLC was change in tumour HV from baseline, this was also assessed in patients (n = 20) with sufficient baseline 2- and 4-h scan HV to reliably measure change (predefined as ≥ 1.5 mL). Tumours were divided into four subregions or distance categories: edge, outer, inner, and centre, using MATLAB. In tumours overall, strong correlation (P < 0.001) was observed for SUVmax ρ = 0.87, SUVmean ρ = 0.91, TBRmax ρ = 0.83 and TBRmean ρ = 0.81 between 2- and 4-h scans. Tumour HV was moderately correlated (P < 0.001) with ρ = 0.69 between 2- and 4-h scans. Yet, in tumour subregions, the correlation of HV decreased from the centre ρ = 0.71 to the edge ρ = 0.45 (P < 0.001). SUV, TBR, and HV values were consistently higher on 4-h scans than on 2-h scans, indicating better tracer-to-background contrast. For instance, for TBRmax, the mean, median, and interquartile range were 1.9, 1.7, and 1.6–2.0 2-h p.i., and 2.6, 2.4, and 2.0–3.0 4-h p.i., respectively. Our results support that FMISO-PET scans should be performed at 4 h p.i. to evaluate tumour hypoxia in NSCLC.Trial registration: ClinicalTrials.gov, NCT02628080. Registered 11/12/2015, https://clinicaltrials.gov/ct2/show/NCT02628080.

Exploring the potential of third-generation microalgae bio-alcohol and biodiesel in arresting particulate smoke emissions and greenhouse gases using CART.

Due to the rise in vehicular emissions, the rapid deterioration of the atmospheric air quality is a cause for concern in a global scale. In this context, the objective of this study is to explore the effect of post-injection parameters on a continuous active regeneration trap (CART) to mitigate harmful greenhouse gases (GHG) and particulate smoke emissions (PSE) using diesel fuel reformulated by long-chain microalgae bio-alcohol and low-density microalgae biodiesel. Furthermore, the efficiency of the CART unit is analyzed based on its ability to mitigate the harmful emissions without sacrificing the engine performance characteristics. From the study, it was observed that the maximum de-smoke efficiency of 67.85% is observed at a post-injection timing (PIT) of 20°CA aTDC at a post-injection mass (PIM) of 4mg for low load condition while operating on microalgae biodiesel. While operating on microalgae bio-alcohol, the maximum de-smoke CART efficiency was observed as 67.25% and 55.78% for low and medium load conditions at a PIT and PIM of 20°CA aTDC and 2mg while operating on the microalgae bio-alcohol. Likewise, the maximum de-HC CART efficiency was obtained at a PIT and PIM of 10°CA aTDC and 1mg with a reduction of about 75% and 73.8% for medium and high load conditions. A slight reduction in oxides of nitrogen with the complete elimination of carbon monoxide emissions is observed after CART treatment for both the fuels.

Numerical analysis of diesel injection strategies on emissions and performance in CH4/diesel powered RCCI diesel engine with high ratio EGR

In this study, the effects of intake port injection of methane and direct of injection diesel on emissions and the combustion of a light-duty RCCI engine were numerically researched. In this way, AVL Boost software was used for 1-dimensional simulation of the combustion process and emission estimation. Higher octane number methane gas was mixed with air from the intake port, while lower octane number diesel fuel was injected directly into the combustion chamber during the compression stroke. Methane gas was injected at a rate of 65% and diesel fuel at a rate of 35%. The diesel injected directly into the combustion chamber was sprayed at a rate of 5% between 0 and 35 °CA with 8 different injection timings after the main injection. In the model engine, 50% high EGR rate was applied in all combustion modes. The results showed that these parameters have significant effects on performance and emissions. The results in summary; NOx emission reduced at all engine speeds with delayed diesel post-injection timing. The maximum drop of NOx emission was 57.34% with Post15. Although the addition of methane slightly increased the soot emission, it was significantly reduced by the simultaneous addition of methane and application of post-injection strategies of diesel fuel. The soot emission was reduced by 58.85% with the Post35 injection strategy.

Prediction of split injection strategy assisted diesel engine combustion, performance and emission characteristics fuelled waste frying oil methyl ester through central composite design

The objective of this study is to use response surface methodology to forecast the performance, combustion, and emission characteristics of an advanced injection strategy-assisted diesel engine running on waste frying oil methyl ester. The experiment was carried out on a diesel engine using a high-pressure fuel injection system. The main injection timing ranges varied from 16 to 24 °CA bTDC, whereas the post-injection ranges from −6 °CA bTDC to 6 °CA aTDC. The injection quantity for the main and post injections quantity varied from 70 % to 90 %, 10 % to 30 %, and the injection pressure is set at 500 bar. Experiments were carried out using a design matrix developed by the design of experiments. At 100 % load, B100-90 %-10 % obtained the highest BTE of 33.87 % and the lowest fuel consumption of 0.268 kg/kW-hr. At the main injection timing of 22 °CA and post-injection timing of −4 °CA, D100-80 %-20 % achieved the lowest unburned hydrocarbon, Smoke emission of 13 ppm, and 1.613 FSN respectively. The point prediction approach was used to forecast the combustion and emission parameters of a diesel engine, and the predicted results were in good agreement with the experimental results. Furthermore, when compared to advance injection timing for biodiesel fuel, retarded injection timing reduces nitric oxide emission. The Split injection strategy is one of the most effective techniques to reduce soot and NO × emissions while maintaining diesel engine efficiency.

Zygote Diameter and Total Cytoplasmic Volume as Useful Predictive Tools of Blastocyst Quality.

Introduction According to the Embryo Protection Act, the selection of embryos with the greatest potential for successful implantation in Germany must be performed in the pronucleus stage. The main aim of this study was to identify morphokinetic parameters that could serve as noninvasive biomarkers of blastocyst quality in countries with restrictive reproductive medicine laws. Materials and Methods The sample comprised 191 embryos from 40 patients undergoing antagonist cycles for intracytoplasmic sperm injection. Blastocysts were cultured in an EmbryoScope chamber and video records were validated to determine the post-injection timing of various developmental stages, cleavage stages, and blastocyst formation. The Gardner and Schoolcraft scoring system was used to characterize blastocyst quality. Results Morphokinetic data showed that the zygote diameter and total cytoplasmic volume were significantly different between good and poor blastocysts quality groups, where zygotes, which formed better blastocyst quality, had smaller diameter and smaller total cytoplasmic volume. Zygotes with more rapid pronuclear disappearance developed in better-quality blastocysts. Differences between good- and poor-quality blastocysts were also observed for late-stage parameters and for the spatial arrangement of blastomere where tetrahedral embryos more frequently forming good-quality blastocyst compare to the non-tetrahedral. Conclusions The study findings could be used to enhance embryo selection, especially in countries with strict Embryo Law Regulations. Further studies, including those in which the implantation potential and pregnancy rate are considered, are warranted to confirm these preliminary results.

Investigation of Human Intrathecal Solute Transport Dynamics Using a Novel in vitro Cerebrospinal Fluid System Analog.

Understanding the relationship between cerebrospinal fluid (CSF) dynamics and intrathecal drug delivery (ITDD) injection parameters is essential to improve treatment of central nervous system (CNS) disorders. An anatomically detailed in vitro model of the complete CSF system was constructed. Patient-specific cardiac- and respiratory-induced CSF oscillations were input to the model in the subarachnoid space and within the ventricles. CSF production was input at the lateral ventricles and CSF absorption at the superior sagittal sinus. A model small molecule simulated drug product containing fluorescein was imaged within the system over a period of 3-h post-lumbar ITDD injections and used to quantify the impact of (a) bolus injection volume and rate, (b) post-injection flush volume, rate, and timing, (c) injection location, and (d) type of injection device. For each experiment, neuraxial distribution of fluorescein in terms of spatial temporal concentration, area-under-the-curve (AUC), and percent of injected dose (%ID) to the brain was quantified at a time point 3-h post-injection. For all experiments conducted with ITDD administration in the lumbar spine, %ID to the brain did not exceed 11.6% at a time point 3-h post-injection. Addition of a 12 mL flush slightly increased solute transport to the brain up to +3.9%ID compared to without a flush (p < 0.01). Implantation of a lumbar catheter with the tip at an equivalent location to the lumbar placed needle, but with rostral tip orientation, resulted in a small improvement of 1.5%ID to the brain (p < 0.05). An increase of bolus volume from 5 to 20 mL improved solute transport to the brain from 5.0 to 6.3%ID, but this improvement was not statistically significant. Increasing bolus injection rate from 5 to 13.3 mL/min lacked improvement of solute transport to the brain, with a value of 6.3 compared to 5.7%ID. The in vitro modeling approach allowed precisely controlled and repeatable parametric investigation of ITDD injection protocols and devices. In combination, the results predict that parametric changes in lumbar spine ITDD-injection related parameters and devices can alter %ID to the brain and be tuned to optimize therapeutic benefit to CNS targets.

Impacts of different exhaust thermal management methods on diesel engine and SCR performance at different altitude levels

Exhaust thermal management is important for efficient operation of the diesel engine aftertreatment system to meet emissions requirements at low speed and low load conditions. In order to study the impacts of exhaust thermal management strategies on diesel engine performance and SCR conversion efficiency at different altitudes, the effects of the altitudes (2000, 1000, and 0 m), intake throttling, exhaust throttling, and post injection were experimentally studied with a high-pressure common-rail diesel engine that consisted of a diesel oxidation catalyst (DOC) and a selective catalytic reduction (SCR) aftertreatment device. The results showed that the exhaust temperature and the SCR conversion efficiency were improved by intake or exhaust throttling or post injection at any altitudes. However, the intake or exhaust throttling resulted in engine air flow rate reduction, combustion deterioration, brake specific fuel consumption (BSFC) increase, and NOx emissions decrease. When the intake throttling and the exhaust throttling were compared with the same pressure change amplitude, the intake throttling provided better effects on exhaust temperature enhancement, SCR conversion efficiency increase, while the exhaust throttling provided worse effects on BSFC. As the altitudes increased, the impacts of the intake or exhaust throttling on the SCR conversion efficiency and the BSFC became more prominent. Moreover, increasing post injection fuel quantity or retarding post injection timing made combustion worse, BSFC higher, and NOx emissions lower with benefits of exhaust gas temperature increase and SCR conversion efficiency increase. Therefore, post injection is an effective method of exhaust thermal management and should be adopted first. Then, intake throttling should be used. Finally, exhaust throttling can be considered.

Parameter investigation of the pilot fuel post-injection strategy on performance and emissions characteristics of a large marine two-stroke natural gas-diesel dual-fuel engine

This study aimed to conduct a parametric study to investigate the effect arising from pilot fuel post-injection strategy on engine combustion, performance, and emissions of a large two-stroke natural gas-diesel dual-fuel engine for marine applications. The one-dimensional and three-dimensional simulation models were built in AVL-BOOST and CONVERGE, respectively, and validated according to experimental results. The effects of post-injection strategies on post-injection timing and mass ratio on engine combustion, performance, and emissions were investigated. As revealed by the results, an appropriate pilot fuel post-injection strategy could achieve lower NOx emissions with less loss of performance. As post-injection timing was delayed, the NOx emission first decreased and then increased. Subsequently, it decreased to the lowest and finally increased. With the increase in the post-injection mass ratio, the NOx emission was kept decreasing. Compared with the original engine, the NOx emission decreased by 81.85 ppm with a post-injection timing of 18 deg after top dead center and with a mass ratio of 0.7. However, the indicated power only decreased by 4.82 kW, and the indicated specific fuel consumption only increased by 0.2 g/kWh. This study can provide some theoretical guidance for the injection strategy optimization of the marine two-stroke natural gas-diesel dual-fuel engines and provide technical suggestions for practical application.

Effect of Fuel Cetane Number on the Performance of Catalyst-Heating Operation in a Medium-duty Diesel Engine

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;To comply with increasingly stringent pollutant emissions regulations, diesel engine operation in a catalyst-heating mode is critical to achieve rapid light-off of exhaust aftertreatment catalysts during the first minutes of cold starting. Current approaches to catalyst-heating operation typically involve one or more late post injections to retard combustion phasing and increase exhaust temperatures. The ability to retard post injection timing(s) while maintaining acceptable pollutant emissions levels is pivotal for improved catalyst-heating calibrations. Higher fuel cetane number has been reported to enable later post injections with increased exhaust heat and decreased pollutant emissions, but the mechanism is not well understood. The purpose of this experimental and numerical simulation study is to provide further insight into the ways in which fuel cetane number affects combustion and pollutant formation in a medium-duty diesel engine.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;Three full boiling-range diesel fuels with cetane numbers of approximately 45, 50, and 55 are employed in this study with a well-controlled set of calibrations employing a five-injection strategy. The two post injections are block-shifted to increasingly retarded timings, and the effects on exhaust heat and pollutant emissions are quantified for each fuel. For a given injection strategy calibration, increasing cetane number enables increased exhaust temperature and decreased hydrocarbon and carbon monoxide emissions for a fixed load. The increase in exhaust temperature is attributed to an increased fueling requirement to compensate for additional wall heat losses caused by earlier, more robust pilot combustion with the more reactive fuels. Formaldehyde is predicted to form in the fuel-lean periphery of the first pilot injection spray and can persist until exhaust valve opening in the absence of direct interactions with subsequent injections. Unreacted fuel-air mixture in the fuel-rich interior of the first-pilot spray is likely too cool for any significant reactions, and can persist until exhaust valve opening in the absence of turbulence/chemistry interactions and/or direct heating through interactions with subsequent injections.&lt;/div&gt;&lt;/div&gt;

Impact characteristics of post injection on exhaust temperature and hydrocarbon emissions of a diesel engine

Increasing exhaust gas temperature (EGT) and providing hydrocarbon (HC) reactants by in-cylinder post injection are effective measures to assist diesel engine exhaust aftertreatment operation for efficient pollution control. The aim of this study is to explore calibration guidance of post injection for base engine performance and aftertreatment requirements. Therefore, the effect of start of post injection (SOPI) timing on engine performance and emissions, especially the relationship between the variations of the EGT and HC emissions caused by different post injection timings were experimentally studied with a 2.0 L high-pressure common-rail diesel engine at different loads. The results showed that the maximum torque contribution was produced by post injection at the earliest SOPI timing at all load levels. When the post injection timing was retarded, the engine brake torque decreased gradually, and more energy of the post injected fuel raised the EGT. The EGT decreased and the HC emissions increased significantly as the SOPI timing was further retarded. At the 20%, 50%, and 80% loads, the maximum EGTs were 357.7, 465.4, and 615.8 °C, increased by 11.6%, 8.6%, and 7%, respectively. The maximum HC emissions were 4932, 3929, and 2746 ppm, increased by 12.44, 1.8, and 5.18 times, respectively. Moreover, a tradeoff relationship between the EGT and the HC emissions was observed at different SOPI timings by a normalized analysis. However, no clear tradeoff relationship between the soot and the NOx emissions was found in the SOPI timing sweep. Consequently, the appropriate SOPI timing range should be determined based on the needs of the aftertreatment system, and multiple post injections may be required to simultaneously increase the EGT and provide the HC reactants for aftertreatment. The optimal SOPI timing also needs to be selected based on impacts on soot and NOx at different loads.

Influence of post-injection parameters on the performance of continuous regeneration trap to mitigate greenhouse gas and particulate emissions from CI engine

The present study explores the influence of post-injection parameters, namely, post-injection angle and post-injection mass, on a continuous active regeneration trap to mitigate vehicular emissions using diesel enriched by active amyl alcohol from Scenedesmus quadricauda microalgae. From the study, while operating on active amyl alcohol-diesel blend, the maximum de-smoke efficiency for low, medium and high load conditions observed were 67.25%, 55.78% and 46.94% respectively at a post-injection timing of 20°CA aTDC and at a post-injection mass of 2 mg. Furthermore, the maximum de-hydrocarbon efficiency was obtained at a post-injection timing and mass of 10°CA aTDC and 1 mg with a reduction of about 65.45%, 75% and 73.8% for low, medium and high load conditions. However, a 1.36% increase in fuel consumption is observed at late post-injections as compared to diesel fuel. At all cases, simultaneous reduction of particulate smoke emissions and oxides of nitrogen of up to 65.45% and 29% were observed with the complete elimination of carbon monoxide emissions by catalytic oxidation treatment within the after-treatment unit. The novelty of this study is to establish third generation bio-energy as a suitable diesel fuel surrogate for a post-injection activated after-treatment unit.

Evolution of unregulated hydrocarbons distribution with different post injection strategies in a common-rail diesel engine

The experiments were carried out to investigate the influence of different post injection timing and post injection rate on the performance of combustion and unregulated hydrocarbons species emissions from a common-rail diesel engine. Fourier transform infrared spectroscopy was used to measure and analyze the unregulated hydrocarbons emissions which include light hydrocarbons (HCs), aromatic hydrocarbon (AHC), and n-octane (NC8). The results showed that the emissions of individual hydrocarbon species were the similar to that of single injection when the post injection time was at 20 °CA and 40 °CA. In the measured hydrocarbons components, CH4 and C4H6 species maintained a low level and weak sensitivity to the different post injection conditions. The overall variation of NC8 species emission was similar to that of THC emission and accounted for most of the THC, which indicated that most of the fuel had no chemical change and entered the exhaust directly under different post injection conditions. It should be noticed that the olefin species decreased and the alkane species increased gradually as the HCs species raised from C1 to C4. Furthermore, the distribution of HC species at 60 °CA was less changed than that of 40 °CA under different post injection rates and was closer to the required after-treatment gas atmosphere due to its larger proportion of highly reactive components.

Model-based on-board post-injection control development for marine diesel engine

Abstract The increasing demands for reducing fuel consumption and emissions in contemporary technology solutions lead to the use of more sensors, actuators, and control applications. With this increasing engine complexity, the feedback design is complex due to the coupling between inputs and combustion parameters. To be able to design the controller systematically, model predictive control (MPC) comes to the scope because of its advantages in the design of multi-input multi-output (MIMO) systems, especially with its constraints handling ability and performance in simultaneously optimizing the engine fuel efficiency and emission reduction. Multi-injection is one of the promising techniques for achieving better engine performance. In this work, post-injection control is implemented utilizing MPC MIMO strategy with the target of exploring the possibility of reducing emissions and improving engine efficiency by controlling post-injection duration and injection timing. The workflow of the MPC controller design from control-oriented model (COM) establishing to MPC problem formation and solution methodology is discussed in this work. Moreover, one contribution from this work is the different implementation angle when compared with the state-of-the-art approaches, where the MPC controller is implemented purely by Matlab Simulink to enable the rapid control prototyping design. The simulation result demonstrated the ability of the controller’s tracking performance and showed a preliminary step towards the nonlinear combustion model-based multi-injection MPC design. The systematic model-based controller framework developed in this work can be applied to other control applications and enables a fast path from design to test.