Numerical investigation on the impact of multiple injection strategies and spray included angles on combustion and emissions in a marine diesel engine

The computational fluid dynamical software AVL-FIRE code was used for investigating the impact of multiply injection strategies and spray included angles on combustion and emissions in a marine diesel engine. The fuel injection parameters of spray included angle and pilot injection timing with pilot-main injection, as well as post injection ratio and post injection duration angle with pilot-main-post injection, were all investigated and optimized. The results indicate that retarding pilot injection timing with pilot-main injection declines high temperature region, resulting in a notable reduction in NOx emissions. Since fuel evaporation and burn are hampered by long spray penetration due to low temperature and pressure with pilot injection, a suitable spray included angle are used to offer more efficient air-fuel mixing process. A wider spray included angle simultaneously reduces soot emission and indicated specific fuel consumption (ISFC). Post injection fuel exerts impact on combustion process by causing a great disturbance to flow field during post combustion. Increasing post injection ratio from 4% to 10% at a small post injection duration angle great emission performance is achieved by simultaneous reduction in NOx and soot emissions while only using a slight consumption of ISFC. To summarize, the defeat of traditional NOx-soot trade-off occurs as both NOx and soot emissions are decreased with optimized multiple injection strategy and spray included angle. Particularly, there are respectively four cases with pilot-main injection and two cases with pilot-main-post injection, that achieve simultaneous reduction in NOx emissions, soot emission, and ISFC, compared to the prototype.

Predictors of Clinically Important Improvements in Motor Function and Daily Use of Affected Arm after a Botulinum Toxin A Injection in Patients with Chronic Stroke

Identifying patients who can gain minimal clinically important difference (MCID) in active motor function in the affected upper extremity (UE) after a botulinum toxin A (BoNT-A) injection for post-stroke spasticity is important. Eighty-eight participants received a BoNT-A injection in the affected UE. Two outcome measures, Fugl–Meyer Assessment Upper Extremity (FMA-UE) and Motor Activity Log (MAL), were assessed at pre-injection and after 24 rehabilitation sessions. We defined favorable response as an FMA-UE change score ≥5 or MAL change score ≥0.5.Statistical analysis revealed that the time since stroke less than 36 months (odds ratio (OR) = 4.902 (1.219–13.732); p = 0.023) was a significant predictor of gaining MCID in the FMA-UE. Medical Research Council scale -proximal UE (OR = 1.930 (1.004–3.710); p = 0.049) and post-injection duration (OR = 1.039 (1.006–1.074); p =0.021) were two significant predictors of MAL amount of use. The time since stroke less than 36 months (OR = 3.759 (1.149–12.292); p = 0.028), naivety to BoNT-A (OR = 3.322 (1.091–10.118); p = 0.035), and education years (OR = 1.282 (1.050–1.565); p = 0.015) were significant predictors of MAL quality of movement. The findings of our study can help optimize BoNT-A treatment planning.

Simulation Study on the Influence of Injector Coupling Leakage on Fuel Injection

In order to study the effect of fuel leakage of an ultra-high pressure common rail injector control valve coupling on fuel injection performance, a simulation model was established by AMESim and the accuracy was verified by fuel injection test data. The leakage law of couples with different clearances was analyzed by using numerical simulation method and then the influence of control valve coupling on fuel injection performance was analyzed. The results demonstrate that the increase of the matching clearance of the slide valve coupling makes the start time of needle valve advanced and delay its end time. The injection rate and injection duration increase with the increase of the matching clearance of slide valve coupling. The increase of the matching clearance of the control plunger coupling keeps the start time of the needle valve unchanged at first, and then delay slightly, while the end time remains unchanged at first, and then show the trend of advance. The injection rate and injection duration decrease with the increase of the matching clearance of plunger coupling.

Optimization of Liquid Accumulation and Gas Injection Duration in Intermitter for Maximizing Production: Case Study

Gas lift is the process of injecting gas into the tubing at a predetermined depth in order to lift the crude oil to the surface. Gas lift is applied to a well when the reservoir pressure falls to such a level that it does not produce without application of external energy. There are mainly two types of gas lift which are Continuous and Intermittent gas lift. This paper deals with the theoretical determination of relationship between liquid accumulation and gas injection duration in an intermittent gas lift well and how this knowledge can be combined with the experience of Engineers to maximize the production of a well. In order to find the relationship between the given durations, a simple mathematical approach with the assumption that the gas injection time is independent of liquid accumulation time is followed. We, then apply various tools of mathematics such as the principles of maxima and minima, Leibnitz theorem, definition of the slope of a line etc. to finally prove the interdependence of liquid accumulation and gas injection time at which the well can produce at its maximum capacity. This interdependence is plotted on a separate graph with the given times on two axis. This curve represents the values at which the reservoir inflow is maximised and hence another curve representing the tubing outflow is drawn on the same graph to intersect the former curve at the optimum value of liquid accumulation and gas injection time. The paper also discusses the physical significance of the cases in which the two curves do not intersect and its possible solutions which vary in accordance with the experience of engineers and conditions of well. Our mathematical calculation led to an astonishing result that the interdependence between the two given durations is elegant and can be easily found without the use of computer in a very short interval of time. The result indicated that if a tangent is drawn from a point representing gas injection time to the graph of accumulation height versus time, it touches the graph at the value of liquid accumulation time at which the production of well is maximized. This novel approach to determine the value of time in an intermitter or time cycle controller in an intermittent well can be proved to be a boon for gas lift optimizers who would otherwise spend a large part of the time in setting the value on hit and trial basis. The graphical method can determine the optimum value in a shorter interval of time and with greater accuracy saving companies from extra man-hours and unscientific approach to optimizing any intermittent gas lift well.

ANALYSIS OF THE PRE-INJECTION CONFIGURATION IN A MARINE ENGINE THROUGH SEVERAL MCDM TECHNIQUES

The present manuscript describes a computational model employed to characterize the performance and emissions of a commercial marine diesel engine. This model analyzes several pre-injection parameters, such as starting instant, quantity, and duration. The goal is to reduce nitrogen oxides (NOx), as well as its effect on emissions and consumption. Since some of the parameters considered have opposite effects on the results, the present work proposes a MCDM (Multiple-Criteria Decision Making) methodology to determine the most adequate pre-injection configuration. An important issue in MCDM models is the data normalization process. This operation is necessary to convert the available data into a non-dimensional common scale, thus allowing ranking and rating alternatives. It is important to select a suitable normalization technique, and several methods exist in the literature. This work considers five well-known normalization procedures: linear max, linear max-min, linear sum, vector, and logarithmic normalization. As to the solution technique, the study considers three MCDM models: WSM (Weighted Sum Method), WPM (Weighted Product Method) and TOPSIS (Technique for Order Preference by Similarity to Ideal Solution). The linear max, linear sum, vector, and logarithmic normalization procedures brought the same result: -22º CA ATDC pre-injection starting instant, 25% pre-injection quantity and 1-2º CA pre-injection duration. Nevertheless, the linear max min normalization procedure provided a result, which is different from the others and not recommended.

Innovative Use of Injectivity Tests as Interference Tests during Field Development: The EGINA Experience

This paper presents the innovative use of interference tests in the assessment of reservoir connectivity and the field oil production rate during the development phase and prior to the first oil of the EGINA field, which is located in a water depth of 1600 m, deep offshore Niger Delta. The interference test campaign involved 26 pre-first oil wells (13 oil producers and 13 water injectors) to assess and subsequently mitigate reservoir connectivity uncertainties arising from the numerous faults and between the different channels within the complexes. The results proved valuable in confirming or otherwise reservoir connectivity, field oil production rate and the number of wells required at first oil to achieve the production plateau. The tests were designed using the analytical method (PIE software) and the reservoir simulation models enabling to establish the cumulative water injection required, the injection duration and the time a response is expected at the observers. These all had impacts on the planning, OIMR vessel requirements and selection of permanent downhole gauges for the wells. In addition, the tests were performed with the water injectors as pulsers and the oil producers as observers allowing to avoid and the associated environmental impact. Ten interference tests were realized compared to four planned in the FDP partly due to the use of the more cost effective OIMR vessel in addition to the rig.