• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.2
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• pp.79-84
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• 2009

Turbocharger has been widely used in many passenger cars in application with diesel engines because of high power and fuel efficiency. However, flow-induced noise (whoosh or hissing noise) which is generated within a compressor during its operation at marginal surge line can deteriorate noise characteristics. Hissing noise excitation is associated with the generation of turbulence within the turbocharger compressor and radiated through the transmission path in a turbocharger system. In this study, a expansion muffler with lids is devised and installed in the transmission path to reduce the hissing noise. Acoustic and fluid dynamic characteristics for the muffler are investigated which are related to the unsteadiness of turbulence and pressure in the turbocharger system. A transfer matrix method is used to analyze the transmission loss of the muffler. A simple expansion muffler with lids is proposed for the reduction of high frequency component noise. Turbulence simulation is carried out by a standard k - ${\varepsilon}$ model. An optimal design condition of the muffler is obtained by extensive acoustic and fluid dynamic analysis on the engine dynamometer with anechoic chamber. A significant reduction of the hissing noise is achieved at the optimal design of the muffler as compared with the conventional muffler.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.235-238
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• 2000

Current diesel engines are usually equipped with turbochargers for improving fuel economy as well as meeting more stringent emission regulations. These turbochargers usually cause noise problems because they spins vey high such as 100,000 to 200,000 rpm, These noises are largely divided into whistle and whine noises. The frequency of whistle noise corresponds to their rotation speed, and the frequency of whine noise does to the multiplication of their rotation speed and the number of compressor blades. Turbocharger manufacturers developed a special type of compressor, effectively compressing air sucked from a duct; Recirculation Compressor Cover (RCC) or Map Width Enhancement (MWE). This special structure improves turbocharger's capability by expanding compressor's working area, but it seriously causes a noise problem, whine noise. There were many trials to surpress the noise occurred inside a compressor such as modification of a compressor, noise baffles or secondary measurements. However, it was currently concluded that the whine noise caused by the special compressor can not be reduced to that done by a standard compressor, and the strength difference of whine noises between the two compressors is not negligible. Thus, the standard compressor is decided to be applied to a newly developing heavy-duty diesel engine in order to resolve the turbocharger noise problem with a stiffened suction duct directly connected to a compressor.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.1
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• pp.143-154
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• 1995

This study investigates the response characteristics of a four-cylinder four-stroke turbocharged diesel engine by using computer simulation and experiments when a rapid acceleration is applied to the fuelpump rack. In the theoretical analysis, linearization method is used to avoid the difficulty on the complex nonlinear functions. Comppressor exit pressure, pressure and temperature of turbine inlet, and turbocharger speed are chosen as the independent variables of transfer functions which represent the dynamic characteristics of the turbocharger system, and expressed as the functions with respect to the time. Experiments on the same eigine system are also carried out to prove the validity of theoretical study. Further, this study carried an experiment for improving transient response performance by injecting air into the inlet manifold under the rapid accelerating conditions. The effects of air injection on the response performances are also represented at varying conditions such as injection pressure, injection period, accelerating rate, accelerating time, engine speed and load.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.2
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• pp.97-103
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• 1994

This paper describes briefly the simulation program for predicting the performance of a high speed turbocharged four cycle diesel engine. The wave phenomena in the intake and exhaust systems are calculated by the characteristic method. The combustion process in the power cycle is represented by the heat release pattern which is given by the Wiebe's function or the pattern based on measured values. Turbocharger matching for the engine is described by utilizing the characteristic maps of both the compressor and turbine, which are obtained from quasi-steady states. A comparison of experimental and calculated results shows a good agreement. Then the influences of the intake system, the period of valve overlap and the characteristics of the turbine are numerically investigated by the simulation.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.2
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• pp.178-184
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• 2015

According to the regulation on the environment and fuel efficiency is becoming strict, many experiments are conducted to improve efficiency and emission in internal combustion engines. LTC (Low temperature combustion) technology is a promised solution for low emissions but there are a few barriers for the commercial engine. This paper includes optimization that applies LTC method to heavy duty diesel engine. Adequate LTC was applied to low and middle load as adaptability in heavy duty diesel engine, and optimization focused on reduction of fuel consumption was proceeded at high load. Through this research, strategy for practical use of LTC was selected, and fuel consumption has improved on the condition that satisfies the emission regulation at systematic viewpoint.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.101-107
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• 2019

This study conducted a simulation to observe the performance of a multi-turbocharged gasoline internal combustion engine for a high-altitude long-endurance unmanned aerial vehicle (HALE UAV). The WAVE 1-D engine simulation software from Ricardo was used for the engine system modeling and simulation. The specifications of a 2.4-L four cylinder gasoline engine from commercial vehicles and maps of commercial vehicle turbochargers were applied to the multi-stage turbocharged engine system model. Three turbochargers and intercoolers were installed in series for the appropriate intake of pressure for the gasoline engine at a high altitude of 60,000 ft. There was one wastegate for the turbochargers. The operability of the engine system was analyzed via this simulation model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.8
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• pp.546-552
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• 2015

In the previous study, the air flow noise around 1.6 k~1.8 kHz was analyzed, and could be reduced by machining a groove in the bore of compressor inlet in front of the main blades of a compressor wheel. It was proven that this groove was very effective for removing the noise without critical sacrifice of compressor performance, and in addition, it did not noticeably deteriorate vehicle performance, drivability and acceleration. It is interesting that the type of groove tried for 1.6~1.8 kHz noise reduction could be effective for another air flow noise, 4 k~6 kHz which is the 3rd order frequency range of turbocharger speed. This study tried various shapes of grooves for minimizing engine performance difference as well as reducing the 3rd order noise. Finally, it was shown that the groove should be round for the engine performance, and an optimal size exist for the noise and the engine performance.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.4
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• pp.69-74
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• 2014

A waste gate valve (WGV) assembly for a gasoline turbocharger is typically manufactured by means of precision casting. In this study, however, it was newly manufactured in a more innovative way, metal injection molding (MIM) using Inconel 713C alloy, and its performance was tested in a 1.6L direct injection gasoline engine by a thermal shock durability test that lasted 300 hours, after which the results were compared to those of a precision-cast WGV assembly with regard to the engine intake boost pressure, turbine wheel speed, and transient intake pressure. It was found that the two WGV assemblies showed similar performance levels throughout the durability test.

• International Journal of Fluid Machinery and Systems
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• v.6 no.3
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• pp.160-169
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• 2013

Two-stage turbocharging is an important way to raise engine power density, to realize energy saving and emission reducing. At present, turbine matching of two-stage turbocharger is based on MAP of turbine. The matching method does not take the effect of turbines' interaction into consideration, assuming that flow at high pressure turbine outlet and low pressure turbine inlet is uniform. Actually, there is swirl flow at outlet of high pressure turbine, and the swirl flow will influence performance of low pressure turbine which influencing performance of engine further. Three-dimension models of turbines with two-stage turbocharger were built in this paper. Based on the turbine models, mechanism of swirl flow at high pressure turbine outlet influencing low pressure turbine performance was studied and a two-stage radial counter-rotation turbine system was raised. Mechanisms of the influence of counter-rotation turbine system acting on low-pressure turbine were studied using simulation method. The research result proved that in condition of small turbine flow rate corresponding to engine low-speed working condition, counter-rotation turbine system can effectively decrease the influence of swirl flow at high pressure turbine outlet imposing on low pressure turbine and increases efficiency of the low-pressure turbine, furthermore increases the low-speed performance of the engine.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.5
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• pp.502-509
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• 2010

A test facility which can simultaneously measure turbocharger operating condition variables and vibro-acoustic emission in the situations that are quite similar to real internal combustion engine operating conditions has been introduced. Using this facility, a new method sweeping from full open throttle to deep surge region along constant speed curves can be utilized instead of the stationary method that has been traditionally used to obtain turbocharger compressor maps. Data covering an extensive range of the compressor performance map have been collected and analyzed. An experimental study is performed to define a noise diagram that correlates vibro-acoustic measurements to aerothermodynamic operating conditions. An instrumentation set in the facility allows the automatic definition of the operating point on the turbine and compressor map of the turbocharger. Also, radiated sound pressure and casing vibration data corresponding to the point are obtained by a microphone in the vicinity of the compressor casing and an accelerometer on the casing. The major source(s) of noise at specific operating point on the map can be easily identified with these maps. Also, acoustic characteristics of a given turbocharger at the vicinity of the surge as well as in the surge are also defined. Finally, the possibility to define mild surge region of a turbocharger using vibro-acoustic measurements is studied.