• 소음진동
• /
• 제6권2호
• /
• pp.197-203
• /
• 1996

This study is to analyze the rotordynamic effect of surface-friction- factor characteristics on an annular seal. The honeycomb geometry which shows friction-factor-jump phenomena is used in this study. A rotordynamic analysis for a contered annular seal has been developed by incorporating empirical friction-factor model for honeycomb stator surfaces. The results of the analysis for the honeycomb seal showing the friction-factor jump is compared to the non- friction-factor-jump case. The results yield that the friction-factor-jump decreasesdirect stiffness and cross coupled stiffness coefficients, and increases damping coefficient to stabilize rotating machinery in a rotordynamic point of view. The analysis of the honeyeomb seal for the friction-factor-jump case shows reasonably good compared to experimental results, especially, for cross coupled and damping coeffcients.

• 대한기계학회논문집
• /
• 제18권6호
• /
• pp.1439-1447
• /
• 1994

Test results of friction-factor for the flow of air in a narrow channel lined with various honeycomb geometries show that, generally, the friction-factor is nearly constant or slightly decreases as the Reynolds number(or Mach number) increases, a characteristic common to turbulent flow in pipes. However, in some test geometries this trend is remarkably different. The friction factor dramatically drops and then rises as the Mach number increases. This phenomenon can be characterized as a "friction-factor jump." Further investigations of the acoustic spectrum indicate that the "friction-factor jump" phenomenon is accompanied by an onset of a normal mode resonance excited coherent flow fluctuation structure, which occurs at Reynolds number of the order of $10^4$. New empirical friction-factor model for "friction-factor jump" cases is developed as a function of Mach number and local pressure.ach number and local pressure.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
• /
• pp.153-157
• /
• 2000

Honeycomb seals are used widely in gas turbines due to their good sealing performance and rotor-dynamic stability. Three-Dimensional complex flows in a honeycomb seal were analyzed in the present study. Friction factors were computed to predict the performance of a honeycomb seal based on pressure drop results for various honeycomb cell geometry and Reynolds numbers. Computed results for friction factor are compared to the available experimental data. Unlike in the experiment, where 'Friction-Factor Jump' phenomena are reported for some cases, computed results show no jump phenomena. The friction factors, however, are in good agreement with the experiment in no-jump cases.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
• /
• pp.247-253
• /
• 1996

The Interfacial friction factor for the countercurrent stratified air-wafer flow has been experimentally investigated in nearly horizontal and inclined pipes. The presence of the hydraulic jump may significantly affect both the flow pattern and the interfacial friction factor. The measured values of f$_{i}$ in nearly horizontal and two inclined pipes are of the same order of magnitude but the dependencies of the air and water velocities are slightly different.t.

• 한국항해학회지
• /
• 제25권4호
• /
• pp.347-360
• /
• 2001

The purpose of this study is to find out the subjective and objective fatigue level and the characteristics of seamen's physical strength with the service period on board, to have a new understanding of the vocation, and to explore a physical exercising program for the seamen. The questionnaire survey for the seamen who had been in service on the ocean going vessels was conducted and the results are fumed out as the followings. Total number of seamen who had answered the questionnaire was 64 persons and the distribution status of service period group was identified as 16 persons for each of 4 groups； the group was classified as the group of less than 5 years, 5 - 10 years, 10 - 15 years, and more than 15 years. 1. Working conditions Working hours in a week was identified as 44－56 hours(45.3%) and the number of 45.3% of the seamen answered the working hours in week is more than 56 hours. The seamen of 25.0% are unsatisfied or very unsatisfied with their vocation. The seamen of 65.6% are smoking, and 45.3% of them drink. The seamen of 44.,3% drink once or more in a week. And the seamen of 67.2% do not take any exercise in a week. 2. Contribution to the seamen's fatigue and subjective symptom The most contributive factor to the seamen's fatigue was identified as the short of sleeping(21.5%), overwork(19.2%), poor working conditions (18.6%), and the friction in human relations also becomes one the contribution to the fatigue(14.0%). The subjective symptom by fatigue was identified as the feeling of languid, sleepy and tiredness of eyes. 3. Characteristics of the seamen's physical strength and Interrelations The grip strength and back strength of the seamen whose service period is less than 5 years were measured as 40.44kg and 127.8kg. The sit ups in the group of service period less than 5 years was measured as 36.84 times, and the vertical jump for the seamen in this group was measured as 46.55cm. The closed-eyes foot balance was measured as 33.64 seconds in the group of service period between 5 and 10 years, and side-step was measured as 35.31 times in the group of service period less than 5 years. The standing trunk flexion was measured as 10.54cm for the seamen whose service period is between 10-15 years, and the trunk extension was measured as 50.70cm for the seamen whose service period is less than 5 years. And the step test of the seamen whose service period is between 10-15 years was measured as 54.44 numbers, and the number of flickers of the seamen whose service period is less than 5 years was measured as 32.94.