Investigations on premixed charge compression ignition engine with external mixture formation and exhaust gas recirculation technique

Journal of Mechanical Science and Technology - In present scenario it is need for automobile sector to develop clean technology which will result in less fuel consumption and green house gas. The...     

Analysis on possibility of expanding low-load operation area for homogeneous charge compression ignition in CI engine with variable exhaust valve actuation

Various technologies are being studied for the advancement of diesel passenger cars and associated environmental regulations. Effective compression ignition combustion in diesel engines is highly dependent on the cylinder charging temperature, composition, and cylinder pressure during valve train operation. The application of variable valve control in diesel engines has several potential advantages. In this study, we applied the variable valve actuation system to a single-cylinder engine model using a GT-POWER simulation and analyzed the effects of the recompression and rebreathing valve profiles, and fuel-injection pressure on the combustion characteristics of a compression ignition engine. As a result, NOx emissions were reduced by more than 90 %, while those of indicated mean effective pressure were reduced by up to 35 %. The benefits of recompression strategies in terms of NOx emissions reduction were confirmed.

     

Effects of equivalence ratio and carbon dioxide concentration on premixed charge compression ignition of gasoline and diesel-like fuel blends

The effects of fuel/air equivalence ratio and CO₂ concentration in fuel/air charge on the ignition process of gasoline and diesel-like fuel (n-heptane) blends on a rapid compression machine are investigated in this study. Results showed that the effects of equivalence ratio on ignition delays of two ignition stages are varied. As equivalence ratio increases from 0.3 to 0.5, the first stage ignition delay slightly increases because the increased equivalence ratio improves the mixture heat capacity, reducing the in-cylinder temperature and weakening the low-temperature heat release process of the fuel. The second stage ignition delay is shortened with the increased equivalence ratio because increased fuel concentration facilitates mixture reactivity. CO₂ addition to the cylinder charge can effectively reduce the peak cylinder pressure and the two stage pressure rise rates, as well as extend the durations of ignition delays of two ignition stages.     

基于黑箱模型和RBF-PID的HCCI发动机燃烧正时控制

由于均质充气压缩点燃(HCCI)发动机缺少直接控制其燃烧的手段,导致HCCI发动机的燃烧正时控制成为HCCI发动机的研究热点。以HCCI发动机进气歧管的温度和压力、燃油当量比、转速以及进气门关闭正时为输入,利用BP神经网络建立用于估计HCCI发动机燃烧正时的黑箱模型。在此模型基础上,以进气门关闭正时为控制量设计了PID控制器,并利用径向基神经网络对其参数进行整定,以实现对燃烧正时的反馈控制。实验结果表明,BP神经网络估计模型对HCCI发动机燃烧正时的估计误差小于0.4(CAD),能实现准确的估计;此外,与传统的PID控制器相比,设计的RBF-PID控制器在超调量、调节时间以及抗干扰性等性能方面均有改善。     

The experimental investigations of recirculated exhaust gas on exhaust emissions in a diesel engine

The effects of recirculated exhaust gas on the characteristics of NOx and soot emissions under a wide range of engine loads were experimentally investigated by using a four-cycle, four-cylinder, swirl chamber type, water-cooled diesel engine operating at three engine speeds. The purpose of this study was to develop the EGR-control system for reducing NOx and soot emissions simultaneously in diesel engines. The EGR system is used to reduce NOx emissions, and a novel diesel soot removal device with a cylinder-type scrubber for the experiment system was specially designed and manufactured to reduce soot contents in the recirculated exhaust gas to the intake system of the engine. The experiments were performed at the fixed fuel injection timing of 4° ATDC regardless of experimental conditions. It was found that soot emissions in exhaust gases were reduced by 20 to 70% when the scrubber was applied in the range of the experimental conditions, and that NOx emissions decreased markedly, especially at higher loads, while soot emissions increased owing to the decrease in intake and exhaust oxygen concentrations, and the increase in equivalence ratio as the EGR rate is elevated.     

The characteristics of biodiesel and oxygenated additives in a compression ignition engine

In this study, experiments on the simultaneous reduction of smoke and NOx emissions of indirect-injection (IDI) diesel engines were conducted using a biodiesel fuel (BDF) and ethylene glycol mono-n-butyl ether (EGBE), which is an oxygenated fuel of mono-ethers, as a pre-processing method and by applying cooled EGR. A four-cylinder, water-cooled IDI diesel engine was used, while the engine performance and emission characteristics were considered using diesel fuel, BDF 100%, and a mixed fuel BDF and EGBE (maximum EGBE mixing ratio in mixed fuel: 20 vol-%). Results showed the BDF and the BDF and EGBE mix had significantly better smoke reduction effects than the diesel fuel. In particular, the use of the BDF and EGBE mix and the simultaneous application of 10% cooled EGR were confirmed to have reduced both smoke and NOx emissions.     

The effect of exhaust gas recirculation (EGR) on combustion stability, engine performance and exhaust emissions in a gasoline engine

The EGR system has been widely used to reduce nitrogen oxides (NOx) emission, to improve fuel economy and suppress knock by using the characteristics of charge dilution. However, as the EGR rate at a given engine operating condition increases, the combustion instability increases. The combustion instability increases cyclic variations resulting in the deterioration of engine performance and emissions. Therefore, the optimum EGR rate should be carefully determined in order to obtain the better engine performance and emissions. An experimental study has been performed to investigate the effects of EGR on combustion stability, engine performance, NOx and the other exhaust emissions from 1. 5 liter gasoline engine. Operating conditions are selected from the test result of the high speed and high acceleration region of SFTP mode which generates more NOx and needs higher engine speed compared to FTP-75 (Federal Test Procedure) mode. Engine power, fuel consumption and exhaust emissions are measured with various EGR rate. Combustion stability is analyzed by examining the variation of indicated mean effective pressure (COV_imep) and the timings of maximum pressure (P_max) location using pressure sensor. Engine performance is analyzed by investigating engine power and maximum cylinder pressure and brake specific fuel consumption (BSFC).     

Running-in wear of a compression ignition engine: Factors influencing the conformance between cylinder liner and piston rings

The conformance between the liner and rings of an internal combustion engine depends mainly on their linear wear (dimensional loss) during running-in. Running-in wear studies, using the factorial design of experiments, on a compression ignition engine show that at certain dead centre locations of piston rings the linear wear of the cylinder liner increases with increase in the initial surface roughness of the liner. Rough surfaces wear rapidly without seizure during running-in to promote quick conformance, so an initial surface finish of the liner of 0.8 μm c.l.a. is recommended. The linear wear of the cast iron liner and rings decreases with increasing load but the mass wear increases with increasing load. This discrepancy is due to phase changes in the cast iron accompanied by dimensional growth at higher thermal loads. During running-in the growth of cast iron should be minimised by running the engine at an initial load for which the exhaust gas temperature is approximately 180 °C.     

An effect of alcohol-plastic oil petrol blends on SI engine performance and exhaust emissions

Energy is becomes a vital and crucial parameter in many technical, commercial and self-development sectors of an individualistic in any countries. In this context, fossil fuels are devaluing and their costs are rises and hovering. While generating energy from the existing fossil fuels not alone economically infeasible but also provoke many sensitive environmental issues. Along with emissions from automobile sector, one of the other culprits in eco system is disposal of waste plastics. To meet the acute energy needs with eco-balance is utilizing plastic oil as functional fuel to run the engines. In the present work experimental investigations are carried out on multi cylinder petrol engine operating with 25 % plastic pyrolysis oil, with and without alcohol additives at 5 % volume basis is blended with petrol. It is noticed from the experimental results that, the engine performance with methanol additive is improved by 8.1 % than petrol and 21.74 % compared to without additive in plastic oil blend. Hydrocarbon emissions are substantially controlled by 54 % compared to petrol and 34.59 % than without additive in plastic oil blend at full load condition.

     

Analysis of compression ignition combustion in a schnurle-type gasoline engine comparison of performance between direct injection and port injection systems-

A two-stroke Schnurle-type gasoline engine was modified to enable compression-ignition in both the port fuel injection and the in-cylinder direct injection. Using the engine, examinations of compression-ignition operation and engine performance tests were carried out. The amount of the residual gas and the in-cylinder mixture conditions were controlled by varying the valve angle rate of the exhaust valve (VAR) and the injection timing for direct injection conditions. It was found that the direct injection system is superior to the port injection system in terms of exhaust gas emissions and thermal efficiency, and that almost the same operational region of compression-ignition at medium speeds and loads was attained. Some interesting combustion characteristics, such as a shorter combustion period in higher engine speed conditions, and factors for the onset of compression-ignition were also examined.     

The effect of hydrogen enrichment on exhaust emissions and thermal efficiency in a LPG fuelled engine

The concept of hydrogen enriched LPG fuelled engine can be essentially characterized as low emissions and reduction of backfire for hydrogen engine. The purpose of study is obtaining low-emission and high-efficiency in LPG engine with hydrogen enrichment. In order to determine the ideal compression ratio, a variable compression ratio single cylinder engine was developed. The objective of this paper is to clarify the effects of hydrogen enriched LPG fuelled engine on exhaust emission, thermal efficiency and performance. The compression ratio of 8 was selected to minimize abnormal combustion. To maintain equal heating value, the amount of LPG was decreased, and hydrogen was gradually added. In a similar manner, the relative air-fuel ratio was increased from 0.8 to 1.3 in increment of 0.1, and the ignition timing was controlled to be at MBT each case.     

A simulation model including intake and exhaust systems for a single cylinder four-stroke cycle spark ignition engine

A comprehensive simulation model is presented for a spark ignition engine including intake and exhaust systems. The power cycle simulation requires only one empirical factor to correct for turbulent speed of the flame front in order to complete the cycle calculation including NO. The exhaust pipe gas dynamics include chemical reactions along path lines. Calculations are presented which compare well with experimental results. The model predictions compare favourably with previous work.     

Effect of water induction on the performance and exhaust emissions in a diesel engine (II)

This study was to investigate the effects of water induction through the air intake system on the characteristics of combustion and exhaust emissions in an IDI diesel engine. The fuel injection timing was also controlled to investigate a method for the simultaneous reduction of smoke and NOx when water was injected into the combustion chamber. The formation of NOx was significantly suppressed by decreasing the gas peak temperature during the initial combustion process because the water played a role as a heat sink during evaporating in the combustion chamber, while the smoke was slightly increased with increased water amount. Also, NOx emission was significantly decreased with increase in water amount. A simultaneous reduction in smoke and NOx emissions was obtained when water was injected into the combustion chamber by retarding more 2°CA of the fuel injection timing than without water injection.     

Improvement and experimental validation of a multi-zone model for combustion and NO emissions in CNG fueled spark ignition engine

This article reports the experimental and theoretical results for a spark ignition engine working with compressed natural gas as a fuel. The theoretical part of this work uses a zero-dimensional, multi-zone combustion model in order to predict nitric oxide (NO) emission in a spark ignition (SI) engine. The basic concept of the model is the division of the burned gas into several distinct zones for taking into account the temperature stratification of the burned mixture during combustion. This is especially important for accurate NO emissions predictions, since NO formation is strongly temperature dependent. During combustion, 12 products are obtained by chemical equilibrium via Gibbs energy minimization method and nitric oxide formation is calculated from chemical kinetic by the extended Zeldovich mechanism. The burning rate required as input to the model is expressed as a Wiebe function, fitted to experimentally derived burn rates. The model is validated against experimental data from a four-cylinder, four-stroke, SI gas engine (EF7) running with CNG fuel. The calculated values for pressure and nitric oxide emissions show good agreement with the experimental data. The superiority of the multizone model over its two-zone counterpart is demonstrated in view of its more realistic in-cylinder NO emissions predictions when compared to the available experimental data.     

Measurement and simulation of pollutant emissions from marine diesel combustion engine and their reduction by exhaust gas recirculation

Taking into account the complexity and cost of a direct experimental approach, the recourse to simulation, which can also predict inaccessible information by measurement, offers an effective and fast alternative to apprehend the problem of pollutant emissions from internal combustion engines. An analytical model based on detailed chemical kinetics employed to calculate the pollutant emissions of a marine Diesel engine in general gave satisfactory results compared to experimentally measured results. Especially, the nitric oxide (NO) emission values were found to be higher than the limiting values tolerated by the International Maritime Organization (IMO). Thus, this study was undertaken to reduce to the maximum these emissions. The reduction of pollutant emissions is apprehended with exhaust gas recirculation (EGR). This paper was recommended for publication in revised form by Associate Editor Kyoung Doug Min Nader Larbi, born on 28 of August 1973 in Tunis, received a Diploma of 2nd class from Merchant Navy of Sousse as an Engineer Officer, and went on to receive his Master and Ph.D. degrees from the Nation School of Engineers of Tunis.     

Multidimensional engine modeling: NO and soot emissions in a diesel engine with Exhaust Gas Recirculation

The effects of EGR (Exhaust Gas Recirculation) on heavy-duty diesel engine performance, NO and soot emissions were numerically investigated using the modified KIVA-3V code. For the fuel spray, the atomization model based on the linear stability analysis and spray wall impingement model were developed for the KIVA-3V code. The Zeldovich mechanism for the formation of nitric oxide and the soot model suggested by Hiroyasu et al. were used to predict the diesel emissions. In this paper, the computational results of fuel spray, cylinder pressure, and emissions were compared with experimental data, and the optimum EGR rates were sought from the NO and soot emissions trade-off. The results showed that the EGR is effective in suppressing NO but the soot emission was increased considerably by EGR. Using cooled EGR, soot emission could be enhanced without worsening of NO.     

Analysis and modeling of exhaust gas temperature in an ethanol fuelled HCCI engine

Low exhaust temperature in homogeneous charge compression ignition (HCCI) significantly limits efficiency of an exhaust aftertreatment system to mitigate high HC and CO emissions in HCCI engines. This article aims to understand the effect of varying input parameters on HCCI exhaust gas temperature (T_exh) for an ethanol fuelled engine. A single cylinder engine is used to collect experimental data at 100 different HCCI conditions. The results indicate that variation in combustion parameters such as start of combustion (SOC), burn duration (BD) and maximum in-cylinder pressure (P_max) are not effectively correlated with variations of Texh, but the indicated mean effective pressure (IMEP) and constant-volume adiabatic flame temperature (T_ad) are strongly related to T_exh. These experimental findings were then used to design an artificial neural network (ANN) model to predict T_exh. The model was validated with the experimental data, indicating an average error less than 4.5°C between predicted and measured T_exh.     

Visualization of liquid fuel behavior in a spark ignition engine during starting and warm-up

The liquid fuel behavior in the intake port and the cylinder during starting and warm-up was visualized through visualization windows using a high speed CCD camera. The videos were taken with the engine firing under cold conditions in the simulated start up process, at 1.000 and 1.200 RPM and intake manifold pressure of 0.5 bar. The variables examined were the injector geometry and injector type (normal and air-assisted). The visualization results show several features of the liquid fuel behavior: 1) backward strip-atomization of the fuel film along the periphery of the intake valves by the valve overlap backflow: 2) forward strip-atomization of the fuel film on the surfaces of the intake system into droplet streams by the intake air flow: 3) film flow which forms significant liquid puddles at the valve surface and at the vicinity of the intake value: and 4) squeezing of the liquid film at the valve lip and seat into large droplets in the valve closing process. Some of the liquid fuel survives combustion into the next cycle. The time evolution of the in-cylinder liquid film is influenced by the injection geometry and port surface temperature. Photographs showing the liquid fuel features and an explanation of the observed phenomena are given in the paper.     

Delay of ignition in early direct-injected PCCI engine combustion using fuel-evaporative cooling and cooled EGR

In early direct-injected PCCI combustion, one of the several approaches to ideal PCCI, the early injected fuel forms a nearly homogeneous air-fuel charge, but most or all of the mixture ignites and burns during the compression stroke, which limits its application to light load operation range with lower-than-expected thermal efficiency. In the present research a unique split fuel injection technique was developed to delay the combustion of the entire fuel for mixing with air before burning. Evaporative cooling effects provided by the fuel in the second injection at precise timing held the self-ignition of the early injected fuel, and thus allowed the entire fuel to burn in PCCI mode at a favorable time in a cycle, namely a little after the top center. The single cylinder test engine run this way demonstrated the diesel-like efficiency along with an-order-of-magnitude lower NOx emissions than in conventional diesel combustion.     

The influence of charge air temperature and exhaust gas recirculation on the availability analysis,performance and emission behavior of diesel - bael oil - diethyl ether blend operated diesel engine

Journal of Mechanical Science and Technology - In this work, the first and second laws of thermodynamic analyses were carried out on Kirloskar direct injection, variable compression ratio (VCR)...