Computational studies of soot paths to cylinder wall layers of a direct injection diesel engine

The investigation reported in this thesis is concerned with the topic of soot formation and soot particle motion in the cylinder of a light duty automotive diesel engine. CFD has been employed to simulate in-cylinder conditions and to investigate the source of particles which are transferred to the oil. The accumulation of soot in the lubricating oil of diesel engines is one of the factors limiting the interval between oil changes and hence service interval. Soot particles can be transferred to oil film on the cylinder wall layers through the complex motion of the fluid flow in the cylinder. The paths of soot particles from specific in-cylinder locations and crank angle instants have been explored using the results for cylinder charge motion predicted by the Kiva-3v CFD code. Using the velocity fields from the simulation data, massless tracking of the in-cylinder soot particles in space and time is carried out employing a particle tracking with trilinear interpolation technique. From this investigation, new computational codes for the prediction of soot particle paths and soot particle size change along a specific path in a diesel engine have been developed. This investigation is the first numerical study into soot particle trajectories within an engine and thus opens up a novel branch of research of soot formation within internal combustion engines. Computed soot paths from the investigation show that soot particles formed just below the fuel spray axis inside the middle bowl area during early injection period are more likely sources of soot particles on the cylinder wall layers than those formed later. Soot particles that are formed above the fuel axis have less tendency to be transported to the cylinder wall layers thus are not likely to be the main source of soot at the cylinder walls. Soot particles that are from the bowl rim area are found to be another source of soot transfer to the boundary layer, as they are directly exposed to reverse squish motion during the expansion stroke. Soot particles that are formed near the cylinder jet axis during fuel injection tend to move into the bowl. These soot particles are found to be from the relatively less concentrated area. In contrast, particles from the most concentrated areas tend to be moving into the bowl and pose least risk of contaminating oil films on the liner. Sensitivity studies of soot particle paths to swirl show that engine operating with low swirl ratios are more vulnerable to soot in oil problem as low swirls cause the bulk fluid flow to be moving closer to the cylinder walls due to fuel jet velocity and reverse squish motions. Decreasing the spray angle lessens the possibilities of soot particles from being transported close the cylinder wall layers while increasing the spray angle increases the possibilities of soot from the bowl region to be transported close to the cylinder wall layers. The temporal and spatial evolution of soot particle size can be predicted by using the history of temperature, pressure and gas species along the paths. An explorative investigation has been carried out to determine the most suitable method to tackle this soot particle evolution. With proper multipliers, all approaches perform quite satisfactorily in terms of predicting the trend of size change. Soot particles that are likely to be transferred to the cylinder wall layers are predicted to change in size parallel to the average mass profile in the whole cylinder where they quickly peak to maximum at around 18° CA ATDC, and gradually decrease in size through EVO

Computational studies of soot paths to cylinder wall layers of a direct injection diesel engine

The investigation reported in this thesis is concerned with the topic of soot formation and soot particle motion in the cylinder of a light duty automotive diesel engine. CFD has been employed to simulate in-cylinder conditions and to investigate the source of particles which are transferred to the oil. The accumulation of soot in the lubricating oil of diesel engines is one of the factors limiting the interval between oil changes and hence service interval. Soot particles can be transferred to oil film on the cylinder wall layers through the complex motion of the fluid flow in the cylinder. The paths of soot particles from specific in-cylinder locations and crank angle instants have been explored using the results for cylinder charge motion predicted by the Kiva-3v CFD code. Using the velocity fields from the simulation data, massless tracking of the in-cylinder soot particles in space and time is carried out employing a particle tracking with trilinear interpolation technique. From this investigation, new computational codes for the prediction of soot particle paths and soot particle size change along a specific path in a diesel engine have been developed. This investigation is the first numerical study into soot particle trajectories within an engine and thus opens up a novel branch of research of soot formation within internal combustion engines. Computed soot paths from the investigation show that soot particles formed just below the fuel spray axis inside the middle bowl area during early injection period are more likely sources of soot particles on the cylinder wall layers than those formed later. Soot particles that are formed above the fuel axis have less tendency to be transported to the cylinder wall layers thus are not likely to be the main source of soot at the cylinder walls. Soot particles that are from the bowl rim area are found to be another source of soot transfer to the boundary layer, as they are directly exposed to reverse squish motion during the expansion stroke. Soot particles that are formed near the cylinder jet axis during fuel injection tend to move into the bowl. These soot particles are found to be from the relatively less concentrated area. In contrast, particles from the most concentrated areas tend to be moving into the bowl and pose least risk of contaminating oil films on the liner. Sensitivity studies of soot particle paths to swirl show that engine operating with low swirl ratios are more vulnerable to soot in oil problem as low swirls cause the bulk fluid flow to be moving closer to the cylinder walls due to fuel jet velocity and reverse squish motions. Decreasing the spray angle lessens the possibilities of soot particles from being transported close the cylinder wall layers while increasing the spray angle increases the possibilities of soot from the bowl region to be transported close to the cylinder wall layers. The temporal and spatial evolution of soot particle size can be predicted by using the history of temperature, pressure and gas species along the paths. An explorative investigation has been carried out to determine the most suitable method to tackle this soot particle evolution. With proper multipliers, all approaches perform quite satisfactorily in terms of predicting the trend of size change. Soot particles that are likely to be transferred to the cylinder wall layers are predicted to change in size parallel to the average mass profile in the whole cylinder where they quickly peak to maximum at around 18° CA ATDC, and gradually decrease in size through EVO

Compressed Natural Gas Direct Injection: Comparison Between Homogeneous and Stratified Combustion

Due to abundance of natural gas, the use of natural gas for automotive use, particularly for internal combustion engine (ICE), is more practical and cheaper than their future successors. Even though natural gas is a cleaner fuel than other fossil fuels and has a higher octane number and can lead to higher thermal efficiency, its low carbon number makes it less attractive as compared to gasoline and diesel. Based on its potential, an engine referred to as compressed natural gas direct injection engine (CNGDI) was designed, developed and tested to operate on compressed natural gas (CNG) as monofuel directly and centrally injected into the engine. Computational and experimental works have been performed to investigate the viability of the design. Computational fluid dynamics (CFD) simulations and experimental works with homogenous combustion showed that the results were in good agreement. From experimental works, it is found that combustion characteristics could be improved by using a stratified charge piston configuration with some drawback on performance. In terms of exhaust emissions, stratified configuration causes slight increase in the emission of CO, CO2 and NOx, which highlight a need for further study on this issue

A Review of Surface Texturing in Internal Combustion Engine Piston Assembly

This paper presents a brief review of surface texturing with a focus on piston assembly application. The paper begins with a general discussion on surface texturing and the manufacturing process of micro dimples.  Further, it discusses the theory of hydrodynamic lift generation and the effect of parameters of micro dimples texture on the surface-to-surface friction. Finally, the effect of surface texturing on heat transfer is briefly discussed. In pursuits to improve internal combustion engine (ICE) efficiency, tribological improvement of moving surfaces by means of micro surface texturing seems to be one of the way. However, texturing parameters have to be carefully designed as it can cause detrimental effect if the designs are wrong. Studies has shown micro surface texturing at piston ring could reduce friction around 20%-50% compare with un-textured piston ring and also reduce fuel consumption at 4%. Micro Surface texturing could also improve heat transfer between the surfaces to reduce piston slap and lubrication oil temperature. As reports on the surface texturing on friction reduction and heat transfer improvement in piston assembly are relatively scarce, it is suggested that optimization of micro dimple parameters for piston skirt application and its effect on engine tribology and heat transfer characteristics be further investigated

Effect of Soot Particle Diameter to Soot Movement in Diesel Engine

Soot is one of the end product produced from the combustion of diesel engine. It can adversely affect the performance of the engine. It can cause the lubricant oil to be dirty thus increase its viscosity. These will results to frequent change of lubricant oil. Therefore, the focus of this study is related to the mechanism soot particles movement during the combustion process in the cylinder of diesel engine. The study of the path movement of soot particles from the initial position where it was formed to the last position was carried out. To analyze their movements, the data formation of soot particles was obtained through the simulation of combustion engine using Kiva-3V software which was used in previous investigation. The data that were obtained from the Kiva-3v simulation were velocity vectors of the soot, fuel, temperature, pressure and others. This data is used in the MATLAB routine to calculate the location of soot particles in the combustion chamber. Mathematics algorithm which is used in the MATLAB routine is trilinear interpolation and 4th order of Runge Kutta. In this study, the influence of soot particles diameter with different angular (θ) is included in the calculation to determine its movement. Results from this study shows that if the size of soot particles is bigger, the probability of the movement of soot particles to the combustion chamber wall is high thus contaminating the lubricant oil

Experimental Investigation Of Performance And Emissions Of A Stratified Charge CNG Direct Injection Engine With Turbocharger

This paper presents the results from 1.6 litre, 4 cylinders stratified charge compressed natural gas (CNG) direct injection engine with boosting device. A turbocharger with compressor trim of 40 was used to increase engine output. The engine was tested at wide open throttle (WOT) and speed ranging from 1000 to 5000 rpm. Engine performance and emissions data were recorded under steady state condition. Results show turbocharged CNG engine produced an average of 26% increment in brake power and 24% additional maximum brake torque as compared with natural aspirated (NA) CNG engine. Turbocharged CNG engine improved brake specific fuel consumption (BSFC) and yielded higher fuel conversion efficiency (FCE). Relatively turbocharged CNG engine showed lower emission of hydrocarbon (HC) and carbon monoxide (CO) throughout tested engine speed. Conversely, the carbon dioxide (CO2) and nitrogen oxide (NOx) emission produced were slightly higher compared with NA CNG engine

Effect of Vaned Diffuser on the Performance of Small Turbocharger

This work presents an experimental investigation of performance of small turbocharger compressor with vaned diffuser. The aim of the study is to investigate the effect of number vaned diffuser on peak pressure ratio in turbocharger. The study was carried out using cold-flow turbocharger test rig driven by compressed air with the impeller rotational speed from 40,000 to 70,000 rpm. Tests were conducted with 6, 8 and 10 number of vanes while maintaining the vane blades angle of 6°, turning angle of 30° and blade length of 21.8 mm. The vanes as a flow deflector were designed as a thin flat plate of 1 mm thickness. All the results were compared with original vaneless diffuser of the compressor. The results found that the proposed design of 6 and 8 vanes shifted the peak pressure ratio toward low mass flow rate region. It was observed that modification from conventional vaneless diffuser compressor to the one equipped with vaned diffuser has significant improvement on the overall pressure ratio of the turbocharger

Ulasan: kebolehan medan magnet merawat bahan api hidrokarbon dalam enjin pembakaran dalam

Peningkatan penggunaan bahan api fosil dan tahap pencemaran udara yang tinggi mendorong penyelidik meneroka pelbagai kaedah untuk mengurangkan kesannya. Selain daripada naiktaraf komponen enjin, modifikasi molekul bahan api juga berupaya menyumbang kepada penyelesaian. Penggunaan medan medan pada paip bahan api sebelum ianya dipancit dalam enjin menjadi salah satu alternatif penting bagi meningkatkan penyampaian enjin dan mengurangkan pembebasan gas ekzos yang mencemarkan. Kajian terdahulu membuktikan bawaha medan magnet berupaya meningkatkan kadar pembakaran dengan mempengaruhi molekul bahan api. Setelah rawatan magnet dilakukan, atom hidrogen dalam bahan api hidrokarbon lebih cenderung untuk bertindakbalas dengan molekul oksigen dan menghasilkan pembakaran yang lebih sempurna. Namun, keputusan yang diperolehi daripada penyelidik adalah berbeza-beza daripada segi kadar penjimatan dan pengeluaran gas ekzos yang bergantung kepada keadaan ujikaji tertentu. Walaupun sesetengah penyelidik berjaya merekodkan penjimatan bahan api yang signifikan dan persis, namun kaedah ini masih belum popular dikalangan pengeluar kenderaan dan pengguna. Objektif laporan ini diterbitkan adalah bagi membincangkan kajian berkaitan pengaruh medan magnet kepada bahan api hidrokarbon dan kesan pembakarannya dalam enjin. Penemuan daripada penyelidikan terdahulu hingga kini dirangkumkan yang menerangkan perihal tindakbalas molekul bahan api semasa rawatan magnet dijalankan serta faktor-faktor utama yang menyumbang kepada pengionan yang lebih berkesan dalam meningkatan prestasi enjin dan pengurangkan gas ekzos secara ketara

SOOT PARTICLE TRAJECTORIES OF A DI DIESEL ENGINE AT 18° ATDC CRANKSHAFT ANGLE

Among the major pollutants of diesel engine is soot. Soot is formed as an unwelcomed product in combustion system. Soot emission to the atmosphere leads to air global warming and health problem. Furthermore, deposition of soot particle on cylinder wall contaminates lubricant oil hence increases its viscosity. This reduces durability of lubricant oil, causing pumpability problems and increasing wear. Therefore, it is necessary to study soot formation and its movement in diesel engines. This study focuses on soot particle trajectories in diesel engine by considering diameter of soot particles that were formed at 18° ATDC crankshaft angle. These soot particle movement are under the influence of drag force with different radial, axial and angular settings and simulated by using MATLAB routine. Mathematical algorithm which was used in the MATLAB routine is trilinear interpolation and 4th order of Runge Kutta. Simulation was carried out for a combustion system of 4 valves DI diesel engine from inlet valve closing (IVC) to exhaust valve opening (EVO). The results show that small diameter of soot particles were transferred near the cylinder wall while bigger soot particle mostly moved in inner radius of the combustion chamber

Effect of vaned diffuser on the performance of small turbocharger / Hilmi Amiruddin...[et al.]

This work presents an experimental investigation of performance of small turbocharger compressor with vaned diffuser. The aim of the study is to investigate the effect of number vaned diffuser on peak pressure ratio in turbocharger. The study was carried out using cold-flow turbocharger test rig driven by compressed air with the impeller rotational speed from 40,000 to 70,000 rpm. Tests were conducted with 6, 8 and 10 number of vanes while maintaining the vane blades angle of 6°, turning angle of 30° and blade length of 21.8 mm. The vanes as a flow deflector were designed as a thin flat plate of 1 mm thickness. All the results were compared with original vaneless diffuser of the compressor. The results found that the proposed design of 6 and 8 vanes shifted the peak pressure ratio toward low mass flow rate region. It was observed that modification from conventional vaneless diffuser compressor to the one equipped with vaned diffuser has significant improvement on the overall pressure ratio of the turbocharger