جستجوی مقالات مرتبط با کلیدواژه "blow-by" در نشریات گروه "مکانیک"
تکرار جستجوی کلیدواژه «blow-by» در نشریات گروه «فنی و مهندسی»-
A multi-objective optimization study and sensitivity analysis of a SI engine piston-rings pack using dynamics analysis software (AVLExcite Piston&Rings) and optimizer software (modeFRONTIER) are presented. The effects of changing the piston rings' tangential force and face profile on the oil and gas flow behavior inside the piston-rings pack are investigated by calculating the lubrication oil consumption, blow-by, and power losses. The feasibility of the simulation model was determined by comparing it to empirical data obtained from experimental testing of the engine to estimate the amount of oil consumption and blow-by gas flow. Using the statistical modeling algorithm SS-ANOVA, multi-objective optimization investigates the individual and interaction effects of the three rings' tangential forces. This method significantly reduces the time and cost required to find the optimal design, an approach not reported in previous studies. The results showed a strong correlation between simulation and experimental test results, indicating an acceptable match during model validation. Furthermore, the predictions show that tangential forces affect sealing performance; thus, modifying the tangential force resulted in a 30% reduction in oil consumption and less than a 0.8 percent increase in friction. Furthermore, the LKZ oil control ring model efficiently reduces oil consumption by 25% while slightly increasing friction (about 10 percent without face coating).Keywords: Internal combustion engines, Blow-by, power loss, Friction, Lubrication oil consumption, Multi-objective optimization, AVLExcite, modeFRONTIER
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امروزه می توان به کمک مدل های شبیه سازی، عملکرد موتور را با دقت بسیار مطلوبی مدل ریزی نموده و راه کارهایی را در راستای عملکرد موتور از جمله ترکیب سوزکردن آن ها بررسی کرد. در پژوهش حاضر یک کد شبیه ساز ورودی ترمودینامیکی چندمنطقه ای ترکیب سوز بنزین-گازطبیعی با زیرمدل نشتی و مکانیزم پیش بینی آلاینده NO توسعه داده شد. سپس از یک موتور تک سیلندر پژوهشی، داده های تجربی سیکل هایی با تکنیک پرش جرقه در نسبت تراکم 10 برای ترکیب های100، 90، 75 و 60 درصد بنزین و مابقی گازطبیعی استخراج شد. از نتایج تجربی به دست آمده با تکنیک پرش جرقه، دو مجموعه 200 سیکلی موتورگردانی و احتراقی بدون گازهای باقیمانده از سیکل قبلی برای اهداف تایید کد شبیه ساز فراهم شد. در حالت موتورگردانی نتایج کد شبیه ساز مجهز به زیرمدل نشتی با نتایج تجربی فشار-زاویه میل لنگ موتورگردانی مقایسه شد. سپس در حالت احتراقی نتایج کد شبیه ساز با میانگین داده های تجربی فشار-زاویه میل لنگ مجموعه احتراقی در هر ترکیب مقایسه شد و با خطای کم تر از چهار درصد عملکرد کد شبیه ساز تایید شد. هم چنین هر دو نتایج مدل شبیه سازی و تجربی نشان دادند که با افزایش گازطبیعی در ترکیب، imep < /span> کاهش یافته است. در نهایت زیرمدل پیش بینی NO نشان داد که با افزایش کسر گازطبیعی در سوخت ترکیبی، کسر NO تولیدی کاهش یافته است.
کلید واژگان: آلاینده اکسیدنیتروژن, ترکیب سوز, مدل چند منطقه ای, موتور اشتعال جرقه ای, نشتیToday, with the help of simulation models, engine performance can be modelled with a high level of precision, and thereby various strategies for the improvement of engine performance including the use of dual-fuel mixtures can be investigated. In the present study, a multi-zone thermodynamic simulation-code in Gasoline-Natural Gas (NG) mode with a Blow-by sub-model and a NO predicting-mechanism was developed. Then using a single-cylinder research-engine, experimental data were collected from various cycles via the use of skip < /span>-fire technique at the compression ratio of 10 for the dual-fuel mixtures of 100%, 90%, 75% and 60% Gasoline and the rest NG. From the obtained experimental data, two 200-cycle series of motoring and combustion without residual-gases were provided to verify the simulation code. In the motoring mode, the results of the simulating code equipped with Blow-by sub-model were compared with the experimental results. Then in the combustion mode, the results of the simulation code were compared with the average of pressure-crank angle experimental data in each dual-fuel mode. The performance of the simulation code was confirmed with an error of less than 4%. Finally, the sub-model for the prediction of NO emission revealed that NO emission decreased with the increase of NG fraction.
Keywords: Blow-by, Dual-Fuel, Multi Zone Model, NO emission, SI Engine -
The objective of this research is to numerically investigate heat transfer and pressure drop characteristic of a baffle assisted multi-jet impingement of air on a heated plate subjected to constant heat flux and cross flow. Two baffle configurations were considered for the present study. An array of jets with 3 x 3 configurations discharging from round orifices of diameter D=5 mm and with jet-to-heated plate distance ranging from 2D to 3.5D were studied. SST k-ω turbulence model was used for numerical simulation to examine the effect of blow ratio and baffle clearance on heat transfer and pressure drop characteristics. Blow ratios of 0.25, 0.5, 0.75 and 1.0 and baffle clearances of 1 mm, 2 mm, and 3mm were considered for CFD simulations. The split baffle configuration with baffle clearance of 3 mm is found to be more advantageous when both heat transfer and pressure drop are considered. However, the segmented baffle configuration with a baffle clearance of 1 mm gave better results for heat transfer alone. The present study also deals with determination of optimal operating parameters with the help of Genetic Algorithm and Artificial Neural Network. A pareto front was obtained for selecting the desired value of heat transfer or pressure drop. It was found that Artificial Neural Network based predictions strongly agree with CFD simulation results, and hence seems to be very useful in arriving at the optimum values of operating parameters.Keywords: Jet impingement, Baffles, Blow ratio, Artificial neural network, Genetic algorithm
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در کار حاضر از موتور تک سیلندر پژوهشی، نتایج تجربی سیکل های با مد پرش جرقه در نسبت تراکم 9 و سرعت rpm1800 برای ترکیب های100%، 90%، 75% و 60% بنزین و مابقی گازطبیعی در نسبت هم ارزی استوکیومتری استخراج گردید. سپس یک کد شبیه ساز ورودی ترمودینامیکی چندمنطقه ای ترکیب سوز بنزین-گازطبیعی با زیر مدل نشتی توسعه داده شد. از نتایج تجربی با پرش جرقه، دو مجموعه 200 سیکلی موتورگردانی و احتراقی برای اهداف تایید کد فراهم گردید. در حالت موتورگردانی نتایج کد شبیه ساز با نشتی با میانگین داده های فشار-زاویه میل لنگ مجموعه موتورگردانی مقایسه شد و زیر مدل نشتی کد شبیه ساز تایید گردید. سپس در حالت احتراقی نیز نتایج کد شبیه ساز با میانگین داده های فشار-زاویه میل لنگ مجموعه احتراقی برای هر ترکیب بررسی و با خطای کمتر از 4% تایید شد. در حالت احتراقی جرم نشتی به شکاف ها قابل توجه تر از حالت موتورگردانی برآورد شد و با توجه به اینکه انحراف نتایج کد بدون نشتی با نتایج تجربی در مقایسه با انحراف نتایج کد با نشتی در حالت موتورگردانی انحراف جدی داشت، اعمال زیر مدل نشتی در کد شبیه ساز از اهمیت ویژه ای برخوردار است.
کلید واژگان: مدل چند منطقه ای, نشتی, بنزین- گازطبیعی, ترکیب سوز, موتور اشتعال جرقه ایIn the present study, a single-cylinder research engine was utilized to capture experimental data at 9 compression ratio and 1800 rpm engine speed for dual fuel mixtures of 100%, 90%, 75% and 60% gasoline and the rest natural gas in skip-fire mode. Then, a gasoline- natural gas multi-zone thermodynamic entrainment simulation-code equipped with blow-by sub-model was developed. Two 200-cycle sets of free residual motoring and firing cycles were separated from the experimental data to check the response of the code. In motoring-case, the ensemble-average P-θ of the motoring set was compared with that of the code and the blow-by sub-model was verified. Next, in the firing-case, the results obtained from the code were compared with the ensemble-average P-θ of the firing set in each fuel combination and the code was validated. In the firing-case, the leakage to crevices was estimated to be considerably more than that of the motoring-case. In the firing mode of the code, the deviation of the obtained results of the code without blow-by option from the experimental results was more serious as compared to those of the code with blow-by, emphasizing the importance of the blow-by sub-model in the code.
Keywords: Multi-Zone Model, Blow-By, Gasoline-Natural Sas, Dual Fuel, Spark-Ignition Engine -
The deposition efficiency and pressure drop of inertial impactor with variable area has been studied numerically and experimentally. The effect of volumetric flow rate, vertical barrier, oblique barrier and flexible concave plate versus deposition and impaction efficiency and pressure drop is investigated. Numerical simulation is carried out with DPM (discrete phase method) and turbulent model of SST k-ω. To validate the numerical results a special test rig is designed to study the deposition efficiency of engine oil droplets (blow-by) with a diameter of 0.1 to 6 μm. Experimental Tests are done in 8, 12, 16 and 20 L/min. To ensure the accuracy of the experimental results, all the tests are repeated at least three times for each volumetric flow rate. Gravimetric method is implemented to calculate the deposition efficiency. According to the results, the deposition efficiency is obtained between 73 and 94 percent for different mentioned impactors and different volumetric flow rate. The numerical results are confirmed by experimental results. Using the barriers increase the efficiency maximum 6 percent in different volumetric flow rate. The results show that by reducing the distance between the vertical barrier and the outlet of nozzle, the deposition and impaction efficiency are increased. Also, the Concave flexible plate with vertical barrier located at 1 mm from the outlet of nozzle is the most efficient case.Keywords: Blow-by, Micro droplets of engine oil, inertial impactor with variable area, Pressure drop
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This work regards the extension of the Miles and Jeffreys theories of growth of wind-waves in water of finite depth. It is divided in two major sections. The first one corresponds to the surface water waves in a linear regimes and the second one to the surface water waver considered in a weak nonlinear, dispersive and antidissipative regime. In the linear regime, we extend the Miles theory of wind wave amplification to finite depth. The dispersion relation provides a wave growth rate depending to depth. A dimensionless water depth parameter depending to depth and a characteristic wind speed, induces a family of curves representing the wave growth as a function of the wave phase velocity and the wind speed. We obtain a good agreement between our theoretical results and the data from the Australian Shallow Water Experiment as well as the data from the Lake George experiment. In a weakly nonlinear regime the evolution of wind waves in finite depth is reduced to an anti-dissipative Kortewegde Vries-Burgers equation and its solitary wave solution is exhibited. Anti-dissipation phenomenon accelerates the solitary wave and increases its amplitude which leads to its blow-up and breaking. Blow-up is a nonlinear, dispersive and anti-dissipative phenomenon which occurs in finite time. A consequence of anti-dissipation is that any solitary waves adjacent planes of constants phases acquire different velocities and accelerations and ends to breaking which occurs in finite space and in a finite time prior to the blow-up. It worth remarking that the theoretical amplitude growth breaking time are both testable in the usual experimental facilities. At the end, in the context of wind forced waves in finite depth, the nonlinear Schrödinger equation is derived and for weak wind inputs, the Akhmediev, Peregrine and Kuznetsov-Ma breather solutions are obtained.Keywords: Surface waves, Wind waves, Interface waves, Rogue waves, Blow-up, Asymptotic models, Miles's mechanism, Jeffrey's mechanism
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بررسی آزمایشگاهی احتراق کم پیچش پیش آمیخته و اثر تغییر پارامترهای هندسی بر عملکرد آناحتراق کم پیچش روشی کم هزینه و موثر را برای ایجاد پایداری در شعله های پیش آمیخته رقیق ارائه مید هد. پیش از این مطالعات متعددی در خصوص نحوه کارکرد مشعل های کم پیچش در شرایط مختلف فشار، سرعت مخلوط، نسبت هم ارزی و مشخصات هندسی متفاوت صورت گرفته و عدد پیچش به عنوان اصلی ترین پارامتر اثرگذار بر عملکرد این مشعل ها به صورت تابعی از ابعاد هندسی مشعل معرفی شده است. فاصله پیچنده از سر مشعل (فاصله درنگ) یکی دیگر از پارامترهای اصلی در طراحی مشعل های کم پیچش است که به طور مستقیم در کاهش نرخ پیچش اثرگذار بوده و تاثیر آن بر عملکرد مشعل و عدد پیچش در مطالعات گذشته مورد توجه قرار نگرفته است. در این تحقیق با برپایی یک بستر آزمون اثر تغییر فاصله پیچنده از سرمشعل در نسبت های هم ارزی مختلف بر توزیع دما و رژیم شعله مورد مطالعه قرار گرفته است. نتایج نشان می دهد افزایش فاصله درنگ موجب افزایش میزان برخاستگی شعله و افزایش بازه عملکرد پایدار آن می گردد. همچنین نتایج نشان می دهد شکل خاص شعله برخاسته حاصل از احتراق کم پیچش که کاسه ای و واگراست، موجب توزیع یکنواخت دما در داخل محفظه احتراق شده و همزمان موجب کاهش تولید آلاینده NOx می گردد.
کلید واژگان: احتراق کم پیچش, پیش آمیخته, پرش شعله, پیچندهExperimental investigation on low swirl premixed combustion and effects of geometrical parameters on its performanceLow swirl burner provides an effective and low cost solution for stable lean premixed combustion. Several studies have been conducted on the performance of these burners in different pressures, temperatures, capacities, mixture velocities and equivalence ratios. The main design parameters of low swirl burners are the swirl number and the recess length. The objective of this paper is the investigation of recess length effects on the burner performance. A rig test has been established and utilized to study the effects of different equivalence ratios and recess lengths on the temperature distribution and flame regime of low swirl burners. Results revealed that increasing the recess length causes the increase in axial bulk velocity and hence the lifted flame would be stable in wider range of equivalence ratios. Observations also show the significant effect of the specific divergent flame regime of low swirl burners on result in uniform temperature distribution inside the combustion chamber and lower NOx production.Keywords: Low Swirl Combustion, Premixed, Blow off, Swirler
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