• 한국자동차공학회논문집
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• 제24권6호
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• pp.642-648
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• 2016

This paper deals with an analytical and experimental investigation to predict the axial thrust load that results from turbocharger operating conditions. The Axial forces acting on the turbocharger thrust bearing are caused by the unbalance between turbine wheel gas forces and compressor wheel air forces. It has a great influence on the friction losses, which reduces the efficiency and performance of high-speed turbocharger. This paper presents the calculation procedure for the axial thrust forces under operating conditions in a turbocharger. The first step is to determine the relationship between thrust forces and strains by experimental and numerical methods. The analysis results were verified by measuring the strains on a thrust bearing with the specially designed test device. And then, the operating strains and temperatures were measured to inversely calculate the thrust strains which were compensated the thermal effects. Therefore it's possible to calculate the magnitudes of the thrust forces under operating turbocharger by comparing the regenerated strains with the rig test results. It will possible to optimize the design of a thrust bearing for reducing the mechanical friction losses using the results.

• 한국자동차공학회논문집
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• 제19권3호
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• pp.29-37
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• 2011

The modal characteristics of a compressor wheel of an automotive turbocharger have been investigated using an experimental method based on an acoustic frequency response function, p/f(${\omega}$), where p is sound pressure radiated from a structure, and f is impact force. First, a well-defined annular disc with narrow radial slots was examined to check whether the vibro-acoustic test could precisely determine natural quencies and vibration modes of structures showing that the vibro-acoustic test proposed in this paper was comparable to the conventional modal test with an accelerometer and the numerical analysis. The conventional method has been found to be inappropriate for compressor wheel because of additional mass due to the accelerometer and additional damping from the accelerometer cable alter the dynamic responses of the wheel blades. odal characteristics of the wheel have been defined using vibro-acoustic test and verified with the results from another conventional method using a laser vibrometer. Natural quencies and mode shapes of a turbocharger wheel, which can't be precisely obtained with onventional method, could be defined accurately without the additional effects from sensor and cable. Proposed method can be applied to small structures where conventional sensors and cables could generate troubles.

• 한국자동차공학회논문집
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• 제24권1호
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• pp.33-38
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• 2016

The turbocharger is an essential component to realize the engine down-sizing. The moment of inertia of turbocharger rotor is an important parameter with respect to acceleration performance of the vehicle. It can be calculated from the CAD software based the geometry data and the material properties. But the accurate value of the inertia of turbocharger rotor must be measured through the experimental method. In this study, the measurement of moment of inertia of turbocharger rotor for 2.0 L spark-ignition engine was carried out. First, an experimental equipment using a trifilar method was designed and fabricated. Some optical devices, that is, photo sensor, counter, convex lens, etc, were used to increase the accuracy of the measurement. Second, error sensitivity for the equipment was analyzed. The error of period time and the radius can give big affects to the accuracy of the moment of inertia. When the amount of error of these two were each 1.0 %, maximum error of the moment of inertia was under 3.0 %. Third, the calibration for the equipment was performed using a calibration rotor which has similar shape to turbine rotor but simple. Calculated value from CAD software and measured one for the calibration rotor were compared. The total error of the equipment and the measurement is about 1.3 %. This result shows that the equipment can give the good result with resonable accuracy. Finally the moment of inertia of the turbine rotor and compressor wheel were measured. The coefficient of variations, the ratio of standard deviation to mean value, were reasonably small at 0.57 % and 0.73 % respectively. Therefore this equipment is suitable for the measurement of the moment of inertia of the turbine rotor and compressor wheel.

• 한국주조공학회지
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• 제42권6호
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• pp.392-397
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• 2022

In order to compliant the stringent exhaust emission regulations, higher fuel efficiency and cleaner exhaust gas in combustion engines have been required. To improve combustion efficiency, an exhaust gas temperature is increasing, therefore higher temperature resistance is required for components in exhaust system, especially turbine wheel in turbocharger. IN100 looks quite attractive candidate as it has high temperature properties with low density, however it has low castability due to poor ductility at high temperature. In this study, the balance of Al and Ti composition was optimized from the base alloy IN100 to improve the high temperature ductility by expanding the γ single phase region below the solidification temperature, while obtaining the high temperature strength by maintaining the volume fraction of γ' phase equivalent to IN100 around 1000℃. Furthermore, the high temperature creep rupture life increased by adding a small amount of Ta. The alloy developed in this study has high castability, low density and high specific strength at high temperature.

• 한국주조공학회지
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• 제41권2호
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• pp.127-131
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• 2021

고온 환경에 대한 우수한 특성을 바탕으로 산업 장비의 고온 재료에 Ti-48Al-2Cr-2Nb 합금이 사용된다. 본 연구에서는 Ti-48Al-2Cr-2Nb 합금 터보 차저 터빈 휠을 진공 원심 주조 방법으로 제작했다. 알루미나 몰드를 이용한 원심 주조시 터보 차저 터빈 휠 블레이드의 미스런 불량을 방지하기 위한 조건을 조사하였다. 진공 원심 주조로 제조된 합금의 미세 구조는 광학 현미경 (OM), 마이크로 비커스 경도 분석기 (HV), X- 선 회절 (XRD) 및 SEM-EDS로 연구하였다. 주조된 Ti-48Al-2Cr-2Nb 합금의 경도 및 SEM-EDS 결과는 산화층 (α- 케이스)의 두께가 일반적으로 50㎛ 미만임을 보여주었다. 예열 온도 1,100oC, RPM 260, 게이트 크기가 큰 알루미나 몰드의 경우 미스런 불량이 거의 없었다. 따라서 높은 예열 온도, 중간 RPM, 큰 게이트 크기 및 알파 케이스 형성 억제를 위한 알루미나 몰드를 통해 미스런이 적은 Ti-48Al-2Cr-2Nb 합금 터보 차저 터빈 휠을 얻을 수 있음을 확인했다.

• 한국가스학회지
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• 제21권2호
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• pp.26-31
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• 2017

이 논문은 디젤 자동차의 터보차저 시스템에 관련된 고장사례를 연구하기 위한 것이목적이다. 첫 번째 사례는 터보차저를 분해하여 확인한 결과 터보 휠의 파손으로 터빈이 손상되어 작동되지 않음으로 배기관 구멍이 막혀 가속이 되지 않는 것을 확인하였다. 터보차저 장착차량의 경우 높은 회전수에서는 엔진을 바로 정지시키게 되면 고온에 의한 터보의 고착현상이 발생될 수 있으므로 공회전 상태를 충분히 유지한 다음 시동을 끄도록 한다. 두 번째 사례는 터보차저를 작동시키는 VGT 액튜에이터의 로드가 고착되어 가속불량 현상이 발생된 것으로 확인되었다. 세 번째 사례는 알터네이터(Alternator) 저항과 인터쿨로 팬 릴레이 커넥터 오조립으로 인해 주행 중 출력부족 현상이 발생한 것을 확인하였다. 따라서, 터보차저 시스템의 철저한 관리를 통해 고장이 발생하지 않도록 하여야 한다.

• 한국산학기술학회논문지
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• 제18권3호
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• pp.711-717
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• 2017

본 논문은 엔진 다운사이징의 관점에서 널리 사용되는 터보과급기 로터의 관성모멘트 측정에 관한 연구이다. Trifilar 방법을 이용하여 관성모멘트를 측정하기 위한 장치를 설계 제작한 후, 장치를 검증하기 위하여 교정로터의 관성모멘트를 측정하였다. 측정의 변동계수는 0.43%, CAD 도면의 관성모멘트와 비교하여 0.75% 오차를 보여 개발된 측정장치가 로터의 관성모멘트 측정에 적합함을 확인하였다. 소형 터보과급기의 터빈 로터와 압축기 휠 각 2개에 대한 관성모멘트 측정을 수행하여 1.0% 미만의 변동계수를 보여 정밀한 측정이 가능함을 보였다. 그러나 CAD 도면의 관성모멘트와 비교한 오차는 터빈 로터는 2.76%와 1.30%로 양호하였으나, 압축기 휠의 경우 27.6%와 24.4%로 상당히 크게 나타났다. 연구에 사용된 압축기 휠은 질량이 소형으로 상대적으로 공기저항이 크고 정확한 주기 측정의 어려움으로 큰 오차를 보였다. 따라서 터빈 로터와 압축기 휠을 결합한 상태에서 측정한 값에서 터빈 로터의 관성모멘트를 빼는 간접 방법으로 측정을 수행하였다. 이때 압축기 휠의 관성모멘트 측정에서 1.2% 미만의 변동계수를 보이고 오차는 5.68%, 7.88%의 값을 보였다.

• 열처리공학회지
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• 제34권6호
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• pp.309-314
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• 2021

Due to the superior corrosion resistance and mechanical properties of TiAl alloy at high temperature, it has been utilized as a turbine wheel of a turbocharger. The dissimilar metallic bonding is usually applied to combine the TiAl turbine wheel with the SCM440 structural steel which is used as a driving shaft. In this study, the TiAl and SCM440 joint were fabricated by using a friction welding technique. During bonding process, to suppress the martensitic transformation and the formation of cracks, which might reduce a strength of the joints, Cu was used as an insert metal to relieve stress. As a result, the intermetallic compounds (IMCs) layer was observed at TiAl/Cu interface while no IMC formation was formed at SCM440/Cu interface. Since understanding of the IMCs effects on the mechanical performance of welded joint is also essential for ensuring the reliability and integrity of the turbocharger system, we estimated the nanohardness of welded joint region through nanoindentation. The relation between the microstructural feature and its mechanical property is discussed in detail.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.851-856
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• 2012

Automotive turbochargers have become common in gasoline engines as well as diesel engines. They are excellent devices to effectively increase fuel efficiency and power of the engines, but they unfortunately cause several noise problems. The noises are classified into mechanical noises induced from movement of a rotating shaft and aerodynamic noises by air flow in turbochargers. The mechanical noises are whine and howling noises, and the aerodynamic noises are BPF (blade-passing frequency), pulsation, surge, some special frequency noises. These noises are bothering passengers because their levels are higher or their frequencies are clearly separated from engine or vehicle noises. The noise investigated in this paper is a BPF noise induced by compressor wheels, whose frequency is the multiplication of the number of compressor wheel blades and its rotational speed. The noise is strongly dependent upon the geometry of wheels and the number of blades. This study tried to apply a groove close to the inlet side of compressor wheels in order to reduce the BPF noise. The groove has successfully reduced the noise of narrow band frequency of a turbocharger. It shows that the groove could reduce the wide band frequency noise, the compressor BPF noise with a best shape of the groove.

• 한국유체기계학회 논문집
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• 제13권5호
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• pp.35-42
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• 2010

This paper deals with the development of analytical model of a turbocharger and its detail rotordynamic analysis. Two analytical models, which are verified by experimental modal testing, are proposed and the analytical model including rotor shaft extended to compressor and turbine wheel end side is chosen. A rotordynamic analysis includes the critical map, Campbell diagram, stability, and unbalance response, especially nonlinear transient response considering nonlinear fluid film force at bearings. Although the linearized analysis accurately predicts the critical speeds, stability limit, and stability threshold speed, the predicted vibration results are not valid for speeds above the stability threshold speed since the rotor vibrates with a subsynchronous component much larger than the one synchronous with rotor speed. Hence, for operating speed above the stability threshold, a nonlinear transient analysis considering nonlinear fluid film force must be performed in order to accurately predict vibration responses of rotor and guarantee results of analysis.