• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.6
• /
• pp.45-54
• /
• 2019

In this study, we analyze the rattle noise of a power takeoff (PTO) driveline and develop a PTO driveline resonance model. We measured the rattle noise of the PTO driveline on the output shaft and, by analyzing the rattle noise in the time domain, we determine that the engine expansion stroke period matches the sound pressure of rattle noise. This finding helped us demonstrate that the rattle noise is caused by the collision between the PTO driving gear and the gear driven by the engine expansion stroke; the torsional vibration caused by this collision is affected by the angular velocity fluctuation of the PTO drive shaft. By measuring the angular velocity of the PTO drive shaft, we confirm that the angular velocity fluctuation of the engine flywheel tends to excessively amplify the PTO drive shaft angular velocity fluctuation. We conclude that the resonance, which occurs when the operating frequency of the engine is close to the natural frequency of the tractor power transmission system, causes the excessive angular velocity fluctuation of the PTO drive shaft. We performed a modal analysis of the PTO driveline resonance and, using the characteristic equation, we show that the resonance occurs when the engine rotation speed is close to 850 rpm, which matches the natural frequency of the PTO driveline.

• Journal of Aerospace System Engineering
• /
• v.10 no.1
• /
• pp.95-102
• /
• 2016

There are many possible disturbance sources on such a spacecraft, but reaction wheel assembly (RWA) which is generally used for spacecraft attitude control is anticipated to be the largest. These effects on degradation of performance of spacecraft such as attitude stability. In reaction wheel, disturbance caused by imbalance and speed error. It is hard to emulate speed error disturbance because it is not coincide with wheel frequency. This paper concentrates on emulating and analyzing the speed error disturbance. Firstly, classify the causes that lead to speed error disturbance which generate RPM fluctuation. Secondly, simulated with disturbance driver module and reaction wheel assembly which are developed by Spacecraft Control Lab. Experimental investigations have been carried out to test the disturbance emulator module as a disturbance generator for RWA. Measurements and test have been conducted on various fault. Frequency analysis of test data show that speed error disturbance effects on wheel settling wheel speed or fluctuation type.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.6 no.2
• /
• pp.257-268
• /
• 2014

In this study, flow-driven rotor simulations with a given load are conducted to analyze the operational characteristics of a vertical-axis Darrieus turbine, specifically its self-starting capability and fluctuations in its torque as well as the RPM. These characteristics are typically observed in experiments, though they cannot be acquired in simulations with a given tip speed ratio (TSR). First, it is shown that a flow-driven rotor simulation with a two-dimensional (2D) turbine model obtains power coefficients with curves similar to those obtained in a simulation with a given TSR. 3D flow-driven rotor simulations with an optimal geometry then show that a helical-bladed turbine has the following prominent advantages over a straight-bladed turbine of the same size: an improvement of its self-starting capabilities and reduced fluctuations in its torque and RPM curves as well as an increase in its power coefficient from 33% to 42%. Therefore, it is clear that a flow-driven rotor simulation provides more information for the design of a Darrieus turbine than a simulation with a given TSR before experiments.

• Journal of Biosystems Engineering
• /
• v.2 no.1
• /
• pp.1-6
• /
• 1977

The dilution of crankcase oil with unburned portions of the fuel during operating is one source of the oil contaminations which will reduce engine life.It has been learned that major causes of oil dilution may be the result of using impure fuels which were mixed with water, dust, and some others, but very little was known about this. This study was conducted to develop a more intimate understanding about oil dilution of the farm kerosene engine while using impure fuel mixed with expecially diesel. Fuels being used in this study were 9 kinds of mixed fuels, kerosene and diesel. Farm kerosenen engine of 10 P.S. was tested at no-load of 1000 and 2000 rpm., such as 1/4, 2/4, 3/4, 4/4, and 11/10 loads for understanding about oil dilution of keresene engine.The result of this study are summarized as follows : 1. The amounts of oil dilution of the engine being tested was increased with increase in the applied loads and the contents of diesel in the mixed fuels when using fuels other than kerosenen and diesel, whereas at $D_100$ fuel the comount of oil dilution decreased in some cases. The lowest value was measured to be 20 cc/hr, at $K_90$ fuel of no-load condition, and the highest value to be 293cc/hr. at $K_{10}$ fuel of 4/4 load condition. 2. When the engine was operated at no-load condition, the amount of oil dilution at 100rpm. was much more than at 2000 rpm. 3. Because the fuel consumption and the oil dilution showed a similar tendency along the applied loads, the excessive fuel consumption of engines was supposed to be one of the important factors affecting oil dilution. 4. The temperature of crankcse oil was varied invesely with oil dilution, but they were not thought to be factors to determine each other variable. 5. The tested engine could be operated with high percentage of diesel mixed fuel from no-load condition to fully loaded condition, but it would be impossible to operate the engine for long hous continuously due to excessive speed fluctuation.

• 유체기계공업학회:학술대회논문집
• /
• 2002.12a
• /
• pp.191-198
• /
• 2002

Oil-free turbo-compressor supported by compliant foil bearings which remove oil-contamination by elimination of the conventional ball bearing and oil lubrication systems is presented. Turbo-compressor makes two individual air compression with two impellers at operating speed, 39,000rpm. In this study, the rotordynamic effects caused by aerodynamic instability were investigated with variable mass flow rate. Correlation between frequencies of pressure fluctuation in two diffusers and those of excitation forces on rotor were clearly developed in aerodynamic unsteady region. Thus, these results show that it is beneficial to design high speed rotating turbomachinery considering coupling effect between aerodynamic instability and rotordynamic force.

• The KSFM Journal of Fluid Machinery
• /
• v.6 no.2 s.19
• /
• pp.62-69
• /
• 2003

An oil-free turbo-compressor supported by compliant foil bearings which remove oil-contamination by elimination of a conventional ball bearing and oil lubrication systems is presented. Turbo-compressor makes two individual air compressions with two impellers at a operating speed of 39,000 rpm. In this study, the rotordynamic effects caused by aerodynamic instability were investigated with variable mass flow rates. Correlations between frequencies of pressure fluctuation in two diffusers and those of excitation forces on rotor were clearly observed in an aerodynamic unsteady region. Thus, these results show that it is beneficial to design high-speed rotating turbomachinery by considering coupling effect between aerodynamic instability and rotordynamic force.

• Journal of Advanced Marine Engineering and Technology
• /
• v.13 no.3
• /
• pp.26-36
• /
• 1989

Recently digital governor system is commonly adapted for the speed control of the marine diesel engine because of too much fluctuation of rpm resulted by the low speed, long stroke, high efficiency and a small number of cylinder of it, and versatile studies on the development of digital governor system are progressed. On this subject the new control method in which the fuel is controlled by feedforwarding the change of load as well as the feedback of angular velocity in case of disregarding the engine dead time and influence of scavenging air was proposed by the authors, and found the method has shown quite a good control performance in comparision to the conventional control method by the simulation using a digital computer for various load change. In this paper the speed control system of a diesel engine is simulated in case of regarding the engine dead time by the proposed method, and also confirm a good control performance of it under even more realistically simulated environment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.05a
• /
• pp.342-352
• /
• 2003

Idle NVH characteristics are one of the most important aspects among the vehicle performances. Vehicle developers are devoted to improve vehicle interior noise and steering wheel and seat vibrations. In order to improve the idle quality, noise and vibration transfer path should be carefully evaluated. Also, effects of various components related to the idle performance should be confirmed. A general procedure for improving the idle qualify is described in detail. The relationship among cylinder pressure characteristics, crankshaft rotational speed variation, and vehicle vibrations is also investigated. Influences of drive shaft, torque converter, air conditioning system, vehicle structure including engine mount system, and idle control parameters on the vehicle idle quality are studied. Weak points of typical vehicles on the idle qualify are identified. Some of improvement measures are proposed and verified.

• Journal of the Korean Society of Combustion
• /
• v.10 no.4
• /
• pp.10-17
• /
• 2005

Sustaining of flame stability of the burner installed in Dielsel exhaust pipe is very difficult because of steep fluctuation of pressure and flow rate. A burner for DPF (Diesel Particulate Filter) which clogged by collected soot regeneration has been made of metal fiber for the purpose of realization of flame stability even in unfavorable condition of Diesel engine exhaust. Flame stability of the metal fiber burner has been investigated in various condition of engine operation. It has been identified that metal fiber burner with liner which has swirl guide vane presents excellent flame stability even in the higher engine revolutions than 3000rpm and sudden variation. The results offer the possibility of development of full flow burner system for DPF regeneration.

• Journal of Radiation Protection and Research
• /
• v.45 no.3
• /
• pp.117-129
• /
• 2020

Background: Radiation portal monitors (RPMs) involving plastic scintillators installed at the border inspection sites can detect illicit trafficking of radioactive sources in cargo containers within seconds. However, RPMs may generate false alarms because of the naturally occurring radioactive materials. To manage these false alarms, we previously suggested an energy-weighted algorithm that emphasizes the Compton-edge area as an outstanding peak. This study intends to evaluate the identification of radioactive sources using an improved energy-weighted algorithm. Materials and Methods: The algorithm was modified by increasing the energy weighting factor, and different peak combinations of the energy-weighted spectra were tested for source identification. A commercialized RPM system was used to measure the energy-weighted spectra. The RPM comprised two large plastic scintillators with dimensions of 174 × 29 × 7 ㎤ facing each other at a distance of 4.6 m. In addition, the in-house-fabricated signal processing boards were connected to collect the signal converted into a spectrum. Further, the spectra from eight radioactive sources, including special nuclear materials (SNMs), which were set in motion using a linear motion system (LMS) and a cargo truck, were estimated to identify the source identification rate. Results and Discussion: Each energy-weighted spectrum exhibited a specific peak location, although high statistical fluctuation errors could be observed in the spectrum with the increasing source speed. In particular, ¹³⁷Cs and ⁶⁰Co in motion were identified completely (100%) at speeds of 5 and 10 km/hr. Further, SNMs, which trigger the RPM alarm, were identified approximately 80% of the time at both the aforementioned speeds. Conclusion: Using the modified energy-weighted algorithm, several characteristics of the energy weighted spectra could be observed when the used sources were in motion and when the geometric efficiency was low. In particular, the discrimination between ⁶⁰Co and ⁴⁰K, which triggers false alarms at the primary inspection sites, can be improved using the proposed algorithm.