Troels Dyhr Pedersen.indd - Solid Mechanics

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ENGINE Page 9 of 21 Piston crown design Crevice height [mm] Radial clearance [mm] Crevice volume [mm 3 ] Flat chamber 19 0.35 1768 3.4 Bowl type chamber 27 0.5 3584 6.9 Ring shaped chamber 13.4 0.35 1247 2.4 Four side chambers 12.5 0.35 1163 2.2 Eight side chambers 10 0.35 931 1.8 Eight cylindrical chambers 27 0.5 3584 6.9 Seven hemispherical chambers 27 0.5 3584 6.9 Table 1: Clearance and crevice volumes of the piston crowns Amount of total volume [%] The engine used for the experiment is a two cylinder, four stroke DI CI engine. Data for the engine in DI CI operation is given in table 2. Bore 85 mm Stroke 85 mm Connecting rod length 160 mm Geometric compression ratio 18.5 Compression pressure 47 bar Inlet valve opens 32 BTDC Inlet valve closes 64 ABDC Exhaust valve opens 64 BBDC Exhaust valve closes 32 ATDC Power output 11.8 kW @ 2000 rpm
Page 10 of 21 16.7 kW @ 3000 rpm 17.9 kW @ 3600 rpm Maximum torque 55 Nm @ 2000 rpm Table 2: Engine data and performance An eddy-current dynamometer was used as engine load. Since the dynamometer did not have motoring capability, the cylinder on the engine not used in the test was run in normal diesel operating mode to keep the engine at operating temperature and at a constant speed. CYLINDER PRESSURE MEASUREMENTS An optical pickup was used to measure the cylinder pressure. The sensor measures the diaphragm deflection with light and outputs the reading in a voltage between 0.5 and 5 volts. The pickup is designed for peak pressures of 350 Bar, which is necessary for long life in knocking conditions. Sensitivity is however adjusted so that the highest output corresponds to 70 Bar, to obtain the best accuracy. The stiffness of the diaphragm provides a high resonance frequency of 120 kHz. The transducer is designed to detect frequencies up to 25 kHz. It is critical that the resonance frequency is not exited even under strong knocking conditions, as the sampling frequency is insufficient to avoid aliasing at frequencies above 36 kHz. It was verified that the sensor resonance frequency is not present, by sampling the sensor output at 400 kHz at higher amplitudes of knock than used in the tests. It was chosen to treat the cylinder pressure oscillations as sound pressure. This simple approach means that the sound pressure in the cylinder can be compared directly to the sound pressure of the radiated noise. The difference may then be expressed as attenuation. VIBRATION MEASUREMENTS The engine surface acceleration is measured by a ceramic axial shear accelerometer mounted in the top corner of the engine block, on the HCCI cylinder side. This position is favorable for measuring the frequencies transmitted from the chamber, but less favorable for measuring the engines lower resonant frequencies which are strongest in the middle of the large unsupported engine surfaces. The position was chosen since the direct transmission of sound from the cylinder was considered most relevant. SOUND MEASUREMENTS The instantaneous sound pressure was recorded with a sound level meter. The microphone was placed 1 meter away from the engine, perpendicular to the crank shaft and at the same elevation as the top of the cylinders. The walls and the floor in the test cell were partly covered with 50 mm insulation materiel to reduce the sound reverberation. With this material thickness and some distance to the wall it is possible to eliminate reflection of frequencies higher than approximately 1 kHz. Lower frequency noise could not be reduced much under the given circumstances. The noise of interest was however that which was generated by engine vibration, which
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Homogeneous Charge Compression Igni
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- 2 - - Table of contents 1 FOREWOR
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- 4 - - 11.5.3 Filtering of sample
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- 6 - - 1 Foreword The work describ
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3 Résumé - 8 - - This thesis is b
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4 Resumé (dansk) - 10 - - Denne af
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5 Introduction - 12 - - 5.1 About H
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- 14 - - 5.3 Scope of investigation
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6 The basics of HCCI combustion - 1
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- 18 - - the cylinder. In HCCI comb
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7 Combustion of DME - 20 - - 7.1 Co
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- 22 - - 8 Description of experimen
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- 24 - - 8.1.3 Piston modifications
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- 26 - - combustion event is often
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- 28 - - however not possible, sinc
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- 30 - - (excess air ratio 3) of ai
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dQ dt = h ⋅ A ⋅ - 32 - - ( T
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- 34 - - In addition, many reaction
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- 36 - - Arrows in the scheme indic
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- 38 - - formaldehyde (CH2O) and fo
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Figure 12: Termination of the low t
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- 42 - - The non-carbon radical act
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10.7 List of species Radicals of hy
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- 46 - - If a frequency analysis of
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- 48 - - 11.5.3 Filtering of sample
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- 50 - - The SPL of the cylinder pr
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Figure 17: Intensity chart for cyli
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- 54 - - 11.7.3 Axial modes Axial w
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- 56 - - A case was set up to make
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12 Simulation of detonation phenome
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- 60 - - provided more ideal condit
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- 62 - - positive in the x- directi
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3,0 x 10 6 2,5 x 10 6 2,0 x 10 6 1,
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- 66 - - A detailed drawing of the
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- 68 - - In the expressions above,
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( 21) ( 22) - 70 - - The mach numbe
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( 25) - 72 - - Δt v = u ⋅ Δx wh
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- 74 - - Figure 29: Development in
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- 76 - - 12.5 Observations of deton
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- 78 - - On figure 34, the individu
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- 80 - - • The engine load obtain
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- 82 - - 15. Takayugi Tsuchiya, Yos
Page 86 and 87: - 84 - - 15 Appendix A: Reduced sch
Page 88 and 89: 16 Appendix B: Detonation model in
Page 90 and 91: - 88 - - 17 Paper I: The Effect of
Page 92 and 93: - 90 - - 19 Paper III: Reducing HCC
Page 94 and 95: DESCRIPTION OF THE EXPERIMENT OBJEC
Page 96 and 97: Engine modification To obtain a low
Page 98 and 99: Pressure [Mpa] 6 5 4 3 2 1 lambda 2
Page 100 and 101: Pressure [Mpa] 6 5 4 3 2 1 lambda 4
Page 102 and 103: At lambda 4, IMEP peaks at a compre
Page 104: CONCLUSION • It was possible to a
Page 107 and 108: close to the lean limit. HC is comp
Page 109 and 110: Reactions do however not stop entir
Page 111 and 112: METHANOL TEST PROCEDURE In the firs
Page 113 and 114: Page 8 of 22 0 -5 -10 -15 -20 -25
Page 115 and 116: With EGR there was a notable change
Page 117 and 118: Page 12 of 22 9 8 7 6 5 4 3 2 MEOH
Page 119 and 120: Page 14 of 22 250 200 150 100 50 40
Page 121 and 122: EMISSIONS The emissions in table 6
Page 123 and 124: Page 18 of 22 15 12 9 6 3 0 1000 RP
Page 125 and 126: REFERENCES 1. Mingfa Yao: An Invest
Page 127 and 128: PM: Particulate matter THC: Total H
Page 129 and 130: Coupling of pressure waves and reac
Page 131 and 132: chambers which often have this flat
Page 133 and 134: The two piston crowns with chambers
Page 135: Page 8 of 21 Figure 10: Steel plate
Page 139 and 140: v v, ref T T ref with T and Tref be
Page 141 and 142: dB higher than the 8 cylindrical ch
Page 143 and 144: Page 16 of 21 Flat chamber 7 BTDC 3
Page 145 and 146: Page 18 of 21 diesel type chamber 3
Page 147 and 148: CONCLUSION HCCI combustion generate
Page 150: DTU Mechanical Engineering Section
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