Motion mode of the optimal damping particle in particle dampers

Kai Zhang,Tianning Chen,Xiaopeng Wang,Jianglong Fang 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.4

To explore the optimal damping mechanism of Particle dampers (PDs), experimental studies on the relationship between the optimal damping performance of PDs and the motion mode of damping particles in PDs were conducted. First, the damping performance of PDs under a certain initial condition was investigated via cantilever system experiments. Then a simple evaluation of the effective mass and effective damping of PDs was performed by fitting the experimental data to an equivalent Single-degree-of-freedom (SDOF) system without damping particles. Finally, the motion mode of damping particles playing the optimal damping effect was determined by vibration table tests with the corresponding control parameters used in the cantilever system experiments. The study results indicate that when the optimal damping performance of PDs is obtained, the granular Leidenfrost effect, whereby the entire damping particle bed is levitated above the vibrating base by a layer of highly energetic particles, is observed in PDs. The optimal damping performance of PDs is mainly caused by the dissipative properties of damping particles in Leidenfrost state.

Optimizing location of particle damper using principles of gas-solid flow

Xiaofei Lei,Chengjun Wu,Peng Chen,Hengliang Wu,Jianyong Wang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6

Particle damping is a passive control technology with strong nonlinearity whose damping effect is relative to the vibration intensity where a particle damper is installed. Then, seeking the optimal installing location of the particle damper to improve the damping effect and vibration control performance is an important research project. To this problem, bound optimization by quadratic approximation (BOBYQA) was employed to discuss the optimal location of a particle damper at the both fixed end plate. For theoretically evaluating the damping effect and invoking it into BOBYQA, the principle of gas-solid flow was used to study the damping effect and establish the theoretical model of particle damping. Further, the estimation precision of the mathematical model was verified by experiment; the results indicate that the proposed mathematical model can more accurately predict the dynamic response of a particle damper installed at both fixed end plate. Therefore, a mathematical model was employed to discuss the optimal position of the particle damper for minimizing maximum amplitude (MMA). The results indicate that particle damper should be installed at the model top close to the monitoring point; if there are two resonances whose amplitudes are equivalent or approximate, the particle damper should be installed at the junction of these model tops.

로켓 모터 연소 불안정에서 추진제 입자의 영향 연구

김태진(Taejin Kim),서성현(Seonghyeon Seo) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12

고체 로켓 모터 내에서 발생하는 연소 불안정을 억제하는 다양한 방법이 존재한다. 입자에 의한 감쇠는 연소실내의 가스보다 밀도가 매우 높은 입자들이 연소가스가 진동하는 동안 가스의 움직임이나 온도의 변화에 즉각적으로 반응하지 못하고 연소가스가 입자를 사이에 두고 진동할 때 감쇠효과를 갖는다. 일반적으로 사용되는 입자는 Al₂O₃와 ZrC가 사용되고 있다. 입자 감쇠는 입자의 직경과 연소가스에 대한 입자의 질량 분율에 관련되며 특정 주파수에서 최대값을 갖는 크기의 입자가 존재한다. 또한, 입자의 직경이 작을수록 고주파 연소 불안정을 효과적으로 억제하고 큰 입자의 경우 저주파 연소 불안정을 억제한다. There are a variety of methods that occur in solid rocket motors for suppression of combustion instability. The solid particle mass is more weighty than the combustion gas mass at the same chamber volume. The solid particles can’t respond immediately to change of motion and temperature while the gas is vibrated. The particle damping occurs because it vibrate between gas and solid particles. Generally, Al₂O₃ and ZrC are used for propellant in rocket motors. Particle damping is related to particle size and mass fraction. In addition, there is a particle size having the maximum attenuation magnitude at a particular frequency. The smaller size of the particles more effectively suppressing high frequency combustion instability. The larger size of the particles suppresses low frequency combustion instability.

진동저감형 의료용 Saw-Blade System의 개발

안영명,이창훈 한국기계기술학회 2013 한국기계기술학회지 Vol.15 No.6

Instruments for surgical and dental application based on oscillatory mechanics submit unwanted vibrations to the surgeon's and dentist's hands. frequently the weight of the instrument's body is increased to dampen its vibration. Because medical devices to contact with human body directly are sterilized before use, conventional damping method and damper are not good for medical use. For dissipation of vibration, based on recent research regarding the optimization of particle damping, we made a prototype particle damper that dissipate the vibration of oscillatory saw and tested for validation of particle damping. As a result we found that particle damper operate more efficiently than solid mass damper if the geometry of the damper is optimized with respect to the specific amplitude of the vibration.

Particle Impact Damper의 성능에 대한 실험적 연구

강한선(Han Seon Kang),김미르(Mir Kim),김현욱(Hyun Wook Kim),이재응(Jae Eung Lee) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11

A variety of damping devices have been developed to solve problems of vibration, and particle impact damper(PID) is studied actively in recent years. Particle impact damper(PID) is a form of the damper that has particles within the cylinder type enclosure and has gap between enclosure and particles. System’s amplitude can be reduced by kinetic energy of the particle itself, collision between particles and the enclosure and the friction between the particles. In this paper, the performance of the PID has been investigated by changing the performance factors such as mass ratio, gap size, particle size through the experiments.

고체 입자와 유동방향 변환에 의한 로켓 모터 내 음향 감쇠에 대한 고찰

김태진(Taejin Kim),성홍계(Hong-Gye Sung),서성현(Seonghyeon Seo) 한국항공우주학회 2015 韓國航空宇宙學會誌 Vol.43 No.9

본 논문은 고체 로켓 모터 연소실 내의 연소과정 중 발생하는 연소 불안정 현상을 억제하는 여러 요소들 중 입자에 의한 감쇠와 유동방향 변환 감쇠에 대한 선행연구의 연구결과를 정리 분석하였다. 입자에 의한 감쇠는 연소실 내에서 발생하는 고주파 연소불안정을 억제하는데 있어 가장 효과적이며 입자의 직경과 질량 분율에 영향을 받는다. 한편 입자에 의한 감쇠에 비해 적은 감쇠량을 갖는 유동방향 변환 감쇠는 추진제의 구조에 따라 변하며, 추진제 표면에서 생성된 와도를 고려한다면 펌핑에 의한 증폭을 고려해야한다. 그러나 추진제의 형상이 원통형일 경우 유동방향 변환 감쇠와 펌핑에 의한 증폭의 크기는 같아지고 상쇄가 일어나 연소 안정성을 보다 쉽게 평가할 수 있다. This paper includes summarization and analysis of previous research results on acoustic attenuation due to particles and flow turning in rocket motors among various damping parameters. Particle damping is the most effective mechanism in suppressing high-frequency combustion instabilities occurring in rocket combustion chambers, which is dependent on the size and the mass fraction of particles. Relatively weak attenuation by flow turning compared to particle damping depends on the geometry of propellant and a combustion chamber. Pumping driving effects need to be taken into account when realizing vorticity generation on the propellant surface. However, its driving effects become cancelled out by flow turning loss when the propellant geometry is cylindrical.

자기장 응답 입자의 배향이 자기유변 탄성체의 전달성에 미치는 영향

이주환 ( Joo Hwan Lee ),정경호 ( Kyung Ho Chung ),윤지현 ( Ji Hyun Yoon ),오재응 ( Jae Eung Oh ),김민수 ( Min Soo Kim ),양경모 ( Kyung Mo Yang ),이성훈 ( Seong Hoon Lee ) 한국고무학회 2011 엘라스토머 및 콤포지트 Vol.46 No.4

자기장 응답 입자를 효율적으로 배향시킬 수 있는 네오디뮴 자석이 삽입된 몰드가 제시되었다. 입자 배향 공정을 통해 이방성 자기유변 탄성체가 제조되었으며 입자의 최적 첨가량은 30 vol.% 였다. 입자 배향성이 증가할수록 자기유변 탄성체의 인장강도는 감소하고 경도는 증가하였다. FFT 분석기를 통해 측정된 최대 자기유변 특성은 30 vol.%의 자기장 응답 입자를 포함한 자기유변 탄성체에서 나타났으며 인가전류 3 A에서 최대 59%의 전단 모듈러스 변화율을 나타내었다. 또한 인가전류와 자기장 응답 입자의 첨가량이 증가할수록 자기유변 탄성체의 전달성은 감소하였고 흡수 주파수 영역은 증가하여 우수한 댐핑 특성을 나타내었다. The neodymium magnet inserted mold was proposed to orient magneto-responsible particles efficiently. The anisotropic magneto-rheological elastomer(MRE) was prepared using the new mold and the optimum amounts of the particles was 30 vol.%. As the orientation of particles was increased, the tensile strength of MRE was decreased, while the hardness of MRE was increased. It was found that the MRE containing 30 vol.% of magneto-responsible particles showed the maximum magneto-rheological effect. The ratio of shear modulus shift was 59% at the input current of 3 A. The transmissibility of MRE was decreased with increasing the input current and loading amounts of magneto-responsible particles. Therefore, the damping property of MRE could be improved by preparing the anisotropic MRE.

알루미나 입자에 의한 음향 감쇠 실험 연구

김태진(Taejin Kim),서성현(Seonghyeon Seo) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.5

고체 로켓 모터에서 발생하는 연소 불안정 현상을 억제하는 방법에는 많은 방법들이 존재한다. 이중 추진제 조성시 금속 입자를 첨가함으로써 연소 메커니즘을 변화시켜 고주파 연소 불안정을 효과적으로 억제한다. 주로 첨가되는 금속 입자는 알루미늄(Al) 입자가 사용된다. 알루미늄 입자는 연소과정을 통해 알루미나(Al₂O₃)가 된다. 알루미나 입자들은 연소가스보다 밀도가 높기 때문에 연소가스가 진동하는 동안 가스의 움직임에 즉각적으로 반응하지 못하고 음향 감쇠가 발생한다. 본 논문에서는 비연소 실험을 통해 입자에 의한 감쇠 효과를 확인하였다. There are many ways of suppressing combustion instability generated in the solid rocket motor. Changing the combustion mechanisms by adding the metal particles in the propellant effectively suppresses the high-frequency combustion instability. The metal particles are mostly added of aluminum(Al) particles in propellant. Aluminum particles are changed to alumina(Al₂O₃) through the combustion process. Acoustic attenuation occurs by the alumina particles. Because the density of alumina particles is more than denser the combustion gas. Particles does not react immediately to the movement of gas during the oscillation. In this paper, carry out the acoustic attenuation by the particles over a cold-flow experiment.

Respiratory Health among Korean Pupils in Relation to Home, School and Outdoor Environment

김정림,Lena Elfman,Gunilla Wieslander,Martin Ferm,Kjell Torén,Dan Norbäck 대한의학회 2011 Journal of Korean medical science Vol.26 No.2

There are few studies about school-environment in relation to pupils’ respiratory health,and Korean school-environment has not been characterized. All pupils in 4th grade in 12selected schools in three urban cities in Korea received a questionnaire (n = 2,453), 96%participated. Gaseous pollutants and ultrafine particles (UFPs) were measured indoors (n =34) and outdoors (n = 12) during winter, 2004. Indoor dampness at home was investigated by the questionnaire. To evaluate associations between respiratory health and environment, multiple logistic- and multi-level regression models were applied adjusting for potential confounders. The mean age of pupils was 10 yr and 49% were boys. No school had mechanical ventilation and CO2-levels exceeded 1,000 ppm in all except one of the classrooms. The indoor mean concentrations of SO2, NO2, O3 and formaldehyde were 0.6 μg/m3, 19 μg/m3, 8 μg/m3 and 28 μg/m3, respectively. The average level of UFPs was 18,230 pt/cm3 in the classrooms and 16,480 pt/cm3 outdoors. There were positive associations between wheeze and outdoor NO2, and between current asthma and outdoor UFPs. With dampness at home, pupils had more wheeze. In conclusion, outdoor UFPs and even low levels of NO2 may adversely contribute to respiratory health in children. High CO2-levels in classrooms and indoor dampness/mold at home should be reduced.

A novel prediction method of vibration and acoustic radiation for rectangular plate with particle dampers

Dongqiang Wang,Chengjun Wu 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.3

Particle damping technology is widely used in mechanical and structural systems or civil engineering to reduce vibration and suppress noise as a result of its high efficiency, simplicity and easy implementation, low cost, and energy-saving characteristic without the need for any auxiliary power equipment. Research on particle damping theory has focused on the vibration response of the particle damping structure, but the acoustic radiation of the particle damping structure is rarely investigated. Therefore, a feasible modeling method to predict the vibration response and acoustic radiation of the particle damping structure is desirable to satisfy the actual requirements in industrial practice. In this paper, a novel simulation method based on multiphase flow theory of gas particle by COMSOL multiphysics is developed to study the vibration and acoustic radiation characteristics of a cantilever rectangular plate with Particle dampers (PDs). The frequency response functions and scattered far-field sound pressure level of the plate without and with PDs under forced vibration are predicted, and the predictions agree well with the experimental results. Results demonstrate that the added PDs have a significant effect on vibration damping and noise reduction for the primary structure. The presented work in this paper shows that the theoretical work is valid, which can provide important theoretical guidance for low-noise optimization design of particle damping structure. This model also has an important reference value for the noise control of this kind of structure.