Seung-Hyup Ryu

The Performance Evaluation With Diffuser Geometry Variations of the Centrifugal Compressor in a Marine Engine (70MW) Turbocharger

An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30-50% of the shaft work input to the compressor stage; for energy efficiency, it is important to recover as much of this as possible. This is the function of the diffuser, which follows the impeller. Effective pressure recovery downstream of an impeller is very important in order to realize a centrifugal compressor with a high efficiency and a high pressure ratio, and an appropriate selection of a diffuser for a specific impeller is a critical step in order to develop the compressor accordingly. The purpose of this study is to investigate the sensitivity of how compressor performances change as the vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and compared with its results. The first vaned diffuser type is based on a modified NACA airfoil, the second is a channel diffuser, and the third is a conformal transformation of NACA 65-(4A10)06 airfoil. A mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. Computational fluid dynamic (CFD) analyses and a detailed interior flow pattern study have been done. In this study, the off-design behavior of three different types of diffusers, given by the mean-line prediction, was investigated using CFD results and the NACA 65 diffuser geometry, which satisfies a wider operating range and has a higher pressure recovery than the others, was selected. The numerical results were compared with experimental data for validation and showed good agreement.

Experimental Study on the Effects of Injector Nozzle and Piston Bowl Geometry on Combustion and Performance in Medium-Speed Diesel Engines

In recent years, many regulations of exhaust gas emissions have been enhanced in not only automotive engines but also marine and power generation engines. So we have done the various studies to reduce NOx in a medium speed diesel engine, HYUNDAI HiMSEN, for satisfying the next IMO(International Maritime Organization) regulation (Tier2, 20∼30% reduction for current limit). The selected parameters for in this study are fuel injector nozzle and piston bowl geometry. These have significant effect on engine performance and combustion. In this study, engine performance experiments have been carried out to investigate the effects of fuel injector nozzle geometry including the nozzle hole diameter, hole number, hole length, and injection angle on the fuel oil consumption and NOx emission of HYUNDAI HiMSEN engine. Also experiments have been carried out to evaluate engine performance and combustion with changing piston bowl geometry including the diameter and depth of piston bowl. The measured parameters of engine performance include cylinder pressure, fuel pump pressure, injection pressure, and heat release rate and NOx, etc. We could find out the optimum point of the nozzle geometry and the piston bowl shape regarding to the trade-off curve on fuel oil consumption versus NOx emission to minimize fuel oil consumption and to satisfy NOx regulation of HYUNDAI HiMSEN engines.Copyright

A Study on Cavitation Damage Reduction in Fuel Injection Pumps

Cavitation phenomena during the spill process of the Bosch type fuel injection pump for medium-speed diesel engine were investigated by optical observations. Typically, these phenomena can cause a surface damage with material removal or round-off at the plunger and barrel port etc., and may shorten their expected life time. The images, which were recorded with high speed CCD camera and borescope, show that the plunger damage is mainly affected by fountain-like cavitation generated before the end of delivery. And the damages of barrel port and deflector are caused by jet-type cavitation generated after end of delivery. Based on the results of optical investigation, 12 different type pumps varied in the geometry of components were designed to alter the direction, distribution, and intensity of cavitations. Finally, the effects of each countermeasure were evaluated by the durability test on actual diesel engine (HiMSEN H21/32).Copyright

The Performance Evaluation of Variations of Diffuser Geometry of the Centrifugal Compressor in a Marine Engine (70MW) Turbocharger

An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30–50% of the shaft work input to the compressor stage, and for energy efficiency it is important to recover as much of this as possible. This is the function of the diffuser which follows the impeller. Effective pressure recovery downstream of an impeller is very important to realize a centrifugal compressor with high efficiency and high pressure ratio, and an appropriate selection of a diffuser for a specific impeller is a critical step to develop the compressor accordingly. The purpose of this study is to investigate the sensitivity of how compressor performances changes as vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and its results were compared. First vaned diffuser type is based on modified NACA airfoil and second is channel diffuser and third is conformal transformation of NACA 65 airfoil. A mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. And CFD analyses have been done for comparison and detailed interior flow pattern study. In this study, the off-design behavior of three different types of diffusers, given by mean-line prediction, was investigated using CFD results and selected the NACA 65 diffuser geometry which satisfy wider operating range and higher pressure recovery than the others. The numerical results were compared with experimental data for validation.Copyright

Aerodynamic Three Dimensional Geometry and Combustor Design for the Compressor of the Medium Speed Diesel Engine Turbocharger

An aerodynamic design for centrifugal compressor which was applied to medium speed diesel engine has been done. First of all, exact compressor specifications must be defined by accurate engine system matching. This matching program has been developed. Using the meanline prediction method, geometric design and performance curves for compressor were established and verified by comparing three dimensional viscous CFD results. The deviation at the design point was about 2.3%. Combustor has been designed and manufactured for the performance test of medium speed diesel engine turbocharger. Fuel nozzle of combustor was designed and its characteristics was analyzed by PIV and PDPA test equipment. Through these results, spray characteristics were studied and flow coefficient equation was deduced.

The Numerical Study on the Performance Evaluations and Flow Structures for the Diffuser of Centrifugal Compressor in a Marine Engine Turbocharger

The centrifugal compressor of marine engine turbocharger is composed of impeller, 1st vaneless diffuser, vaned diffuser, 2nd vaneless diffuser and volute casing. An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30–50% of the shaft work input to the compressor stage, and for energy efficiency it is important to recover as much of this as possible. This is the function of the diffuser which follows the impeller. Effective pressure recovery downstream of an impeller is very important to realize a centrifugal compressor with high efficiency and high pressure ratio, and an appropriate selection of a diffuser for a specific impeller is a critical step to develop the compressor accordingly. The purpose of this study is to investigate the sensitivity of how compressor performances changes as vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and its results were compared. First vaned diffuser type is based on NACA airfoil and second is channel diffuser and third is conformal transformation of NACA 65 airfoil. Mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. And CFD analyses have been done for comparison and detailed interior flow pattern study. In this study, the off design behavior of three different type of diffuser, given by mean-line prediction, was investigated using CFD results and selected best diffuser geometry which satisfy wider operating range and higher pressure recovery than the others. The numerical results were compared with experimental data for validation.Copyright

A Numerical Approach for the Design of the Compressor Impeller Exit Diameter Variations in a Marine Engine Turbocharger

A turbocharger has been designed to fulfill the requirements of medium speed marine engines, 900 kW output power at nominal operation point. The main objective of the design was to meet the requirements of engine power and increased engine operating range. This must be achieved by improving the degree of aerodynamic efficiency and the pressure ratio. The design was performed by the two stages. First, quasi-two dimensional program code was used to determine the main geometry of the compressor. Second, the detailed geometries of compressor blade were completed by using a three dimensional fluid flow analysis. The analyzed performance results were compared with the experimental data for the verification of their validity. Also, the designed three different impeller exits allow for a substantial performance variation. Increased compression ratio and mass flow rate of new optimized impeller were 10.08 and 27.3 percent higher than those of origin impeller, respectively. This simple change of design parameter offers considerable advantages to customers when upgrading their engines.Copyright

A Numerical Study on the Design and Flow Patterns of Compressor Impeller in a Marine Engine Turbocharger

The centrifugal compressor design of the high-speed marine engine (500–900 kW) turbocharger has been done. Increased Higher compressed air and power density help improvement of the engine performance and power. The centrifugal compressor of the marine engine turbocharger is composed of impeller, 1st vaneless diffuser, vaned diffuser, 2nd vaneless diffuser and volute casing. The design process is achieved by three following stages. First, quasi-two dimensional code is used to determine the main geometry of the compressor. Second, three-dimensional compressible Navier-Stokes equation is applied to analyze the flow pattern and structures of the compressor blade loading. Here, among compressor impeller geometry, blade height variables are mainly changed. Smooth flow guidance has to precede and flow separation symptoms must not appear within compressor impeller. When the loading distribution is inadequate from blade hub to shroud, new curved profile should be designed to minimize the pressure loss. By analyzing the internal flow fields for the compressor impeller geometry variations, three dimensional impeller design profile has been confirmed. Compressed air pressure and mass flow rates from new optimized design were 2.7%, 27.3% higher than that of old one each other. Third, analyzed results are compared with experimental data for the verification of the present design method.Copyright