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Mesin
Published by Institut Teknologi Bandung
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Core Subject : Engineering,
Mechanical Engineering
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Articles 5 Documents
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Search results for , issue "Vol 23, No 1 (2008)" : 5 Documents clear
COMPUTATIONAL AERODYNAMIC STUDY OF A HATCHBACK CAR MODEL Kurniawan, Rio Teguh; Zuhal, Lavi R; Amalia, Ema
Mesin Vol 23, No 1 (2008)
Publisher : Mesin

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Abstract

"Ahmed Body" is a well-established model of a hatchback car. In this study, computational simulations were conducted by using existing CFD software to capture "drag crisis" phenomena. Flow is assumed as incompressible flow with Reynolds Number of 4.3 x 10^6. A half of "Ahmed Body" was used in computational simulations with RANS method. Turbulence models that were employed mostly are k-e. The amount of grid cells used in computation is about 300.000. Computations were carried out mostly to get drag coefficients and also to examine vortex structure related to it. In "drag crisis" phenomena, maximum drag coefficient is reached at rear window angle of 30 degrees. Placement of spoilers and vortex generator has succesfully reduced the maximum drag coefficient at the critical angle of 30 degrees.
STUDI NUMERIK KARAKTERISTIK ALIRAN SILANG PADA SILINDER BUNDAR TUNGGAL Fajar, Berkah
Mesin Vol 23, No 1 (2008)
Publisher : Mesin

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Abstract

This study deals with numerical investigation of hydrodynamic properties of fluids flow accross a single circular cylinder. The flow is assumed incompressible, laminar with Reynolds number 0,0001, 2, 20, 40, 100, 200, 400, 1000, 4000 and 20000. The work started with generating geometrical mesh, and then continue with the numerical simulation. The simulations were done by varying the pressure with standardm linier or second order interpolation, momentum discretisation (first-order upwind, second-order upwind, Power law), and pressure velocity coupling (SIMPLE, SIMPLEC, and PISO). The simulation results agree with the experimental results done by other. The comparison parameter used were flow pattern, Strouhal number, drag coefficient, and separation position. The simulation results also show that the flow characteristic with Reynolds Number larger than 40 is depend on time (unsteady). This is caused by vortex shedding at the rear of the cylinder. The body force (lift and drag) on the cylinder change periodically and the value agree with the experimental results.
DEVELOPMENT OF EXPERIMENTAL TESTING SYSTEM AND PERFORMANCE MEASUREMENT OF SMALL TURBOJET ENGINE “OLYMPUS” Yuliartha, I.G.K Adhi; Hartono, Firman; Sardjadi, Djoko
Mesin Vol 23, No 1 (2008)
Publisher : Mesin

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Abstract

This paper describes the development of experimental testing system and performance measurement of small turbojet engine “Olympus” manufactured by AMT Netherlands. Variables that measured in the measurement are turbine exit gas temperature, fuel and air mass flow, compressor rotational speed, and thrust produced. In this testing, the thrust generated by the engine is measured using bending beam load cell that completed with four strain gauge (each load cell completed with two strain gauge). Strain gauge used in this testing is manufactured by Measurement Group, Inc with gauge factor 2.095 ± 0.5%. Air flow is measured by using Pitot tube which is installed in 400 mm long and 107 mm diameter inlet pipe. Measurement sensor of the Thermocouple, which is used to measure turbine exit gas temperature, and tachometer, which is used to measure compressor rotational speed, are connected to electronic control unit and displayed in engine data terminal. Fuel flow is measured by  using digital weight (1 gram resolution) and stopwatch. Fuel consumption at one time interval is recorded manually. The engine revolution was varied from 37000 RPM to 105000 RPM with 10000 RPM interval step. Measurement data are then corrected to get the results on standard pressure and temperature condition. Good agreement between the experiment result and data from references shows that the testing system works as expected.
STUDY ON APPLICATION OF DRAG-REDUCING TRIMETHYLOLETHANE SLURRY IN DISTRICR COOLING SYSTEM Usui, Hiromoto; Suzuki, Hiroshi; Komoda, Yoshiyuki; Indartono, Yuli Setyo
Mesin Vol 23, No 1 (2008)
Publisher : Mesin

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Abstract

Trimethylolethane (TME) trihydrate slurry is a proper phase-change material for latent heat transportation in cooling systems since it has excellence heat transfer performance and high thermal capacity. Additives, oleyl bishydroxyethyl methyl ammonium chloride (as surfactant) and sodium salicylate (as counter-ion), were used as drag-reducer substance. These additives not only induce drag reduction in TME slurry, but also control particle growth and agglomeration. In this study, energy saving estimation of drag-reducing TME slurry application in district cooling system is invesitgated. It is found that drag-reducing TME slurry gives remarkable pumping power suppresion in the district cooling system. To maintain high performance of heat exchangers, heat transfer enhancement technique may be needed in those exchangers.
ANALISIS KESALAHAN FUNGSI RESPON FREKUENSI AKIBAT KETERBATASAN WAKTU REKAM PADA PENGUJIAN GETARAN DENGAN EKSITASI IMPAK KASUS DOMAIN WAKTU KONTINU Lilansa, Noval; Abidin, Zainal; Suharto, Djoko
Mesin Vol 23, No 1 (2008)
Publisher : Mesin

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Abstract

This paper derives mathematical equation describing the relation between errors in FRF due to limited record time length, record time and the time constant of a vibration system modelled by the I- dof vibration system with viscious damping. It is assumed in derivation of the equations that both impact excitation as well as response signals are not contaminated by noises. Moreover, the impact excitation is assumed to be a delta Dirac function. Consequently, the spectrum of the excitation is constant for all frequencies. The derived mathematical equations results show that the FRF error is a complex function so that is can be expressed by the magnitude anf phase functions. The magnitude of FRF error represent the maximum possible error occuring in the FRF magnitude. The maximum possible error occuring in the FRF magnitude at fn is influenced by parameters, such as record time and time constant of the structures. This maximum possible error shows an exponentially decreasing nature as the ratio of these parameters increases. Based on the derived equation, a recording of the response signal within three times of the system time constant results in the maximum possible error at fn in the FRF magnitude in the order of 5% of the theoritical FRF magnitude. Such recording can be performed if the peak amplitude of the response signal ceases to about 5% of the initial peak amplitude at the end of the record time for between 0.001 and 0,1.

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