Troels Dyhr Pedersen.indd - Solid Mechanics

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- 90 - - 19 Paper III: Reducing HCCI Combustion Noise through Piston Design
JSAE 20077134 SAE 2007-01-1860 A study on the effects of compression ratio, engine speed and equivalence ratio on HCCI combustion of DME Troels Dyhr Pedersen, Jesper Schramm Technical University of Denmark Copyright © 2007 Society of Automotive Engineers of Japan, Inc. and Copyright © 2007 SAE International Inc. ABSTRACT An experimental study has been carried out on the homogeneous charge compression ignition (HCCI) combustion of Dimethyl Ether (DME). The study was performed as a parameter variation of engine speed and compression ratio on excess air ratios of approximately 2.5, 3 and 4. The compression ratio was adjusted in steps to find suitable regions of operation, and the effect of engine speed was studied at 1000, 2000 and 3000 RPM. It was found that leaner excess air ratios require higher compression ratios to achieve satisfactory combustion. Engine speed also affects operation significantly. INTRODUCTION The HCCI combustion process is known to produce little or no particulate matter and low levels of NO, while having the potential of a high indicated efficiency at part load operation. In the recent years, the use of DME in the HCCI combustion process has caught the attention of automotive engineers. DME is an interesting fuel for the HCCI process, as it has auto ignition properties superior to normal diesel fuel, thereby ensuring ignition at moderate compression ratios without the need for preheating. Exhaust emissions of unburned DME and lower hydrocarbons as well as CO may be treated in a simple catalytic conversion. Studies on the application of DME in the HCCI combustion process may be divided into three categories with respect to the supplementary fuel or additive usage. These are studies on combustion of pure DME, studies on additive effects and studies of dual fuel combustion. Combustion of pure DME has previously been studied by Zheng et al [1] at a compression ratio of 17 and engine speeds from 1400 -2000 RPM. Highest IMEP achieved with pure DME was 3.1 Bar. Another study by Shenghua et al [2] used a lower compression ratio of 10.7 and engine speeds of 1800 and 2000. A BMEP of 3.2 bar was achieved in this study. In both of these cases it was concluded that DME is only suitable for part load operation, as higher engine loads causes unacceptable pressure rise rates and knock. Shenghua et al [3] made a later study were three different compression ratios (8, 10.7 and 14) were used with variation of speed and fuel input. A BMEP of 3.5 Bar at a compression ratio of 8 was demonstrated in this study. Hamada et al [4] have investigated the ignition timing through a study of the formation of OH and HCHO radicals in the low temperature reactions, using a spectroscopic method. A large interval of compression ratios at constant speed (1400 RPM) was used. Useful data on the duration and onset of low temperature reactions were presented here. The most common finding is that HCCI combustion of DME results in a very limited operability, and that timing of heat release is difficult. The use of EGR is now commonly regarded as a promising strategy to control HCCI combustion of pure DME [5, 6], whereas other strategies are concerned with the use of DME in combination with other fuels. Studies of additive effects include those of Yamada et al [7] who studied the reaction suppression effect of methanol and the reaction enhancing effect of ozone. Ogawa et al [8] studied the effect of direct injection of water and methanol in a premixed DME HCCI engine. Studies of dual fuel operation include those of Zheng et al, who have made an extensive theoretical and experimental research on dual fuel combustion of DME with natural gas, methane and methanol [9, 10]. Sato et al [11] also studied the use of DME and hydrogen in combination with methane. Other studies of dual fuel operation include those of Shudo et al [12], who used a DMEreformed gas as supplement to combustion of pure DME. It was found that control of ignition timing was enabled by varying the amount of reformed DME to pure DME. The combustion of pure DME in HCCI combustion mode is however still of interest, as information on the combustion of pure DME helps to clarify the need of additional fuel or additives. If the right operating strategy is used it may be argued that the benefits of this engine principle compensates for its shortcomings.
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Homogeneous Charge Compression Igni
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- 2 - - Table of contents 1 FOREWOR
Page 6 and 7:
- 4 - - 11.5.3 Filtering of sample
Page 8 and 9:
- 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
Page 18 and 19:
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
Page 24 and 25:
- 22 - - 8 Description of experimen
Page 26 and 27:
- 24 - - 8.1.3 Piston modifications
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- 26 - - combustion event is often
Page 30 and 31:
- 28 - - however not possible, sinc
Page 32 and 33:
- 30 - - (excess air ratio 3) of ai
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dQ dt = h ⋅ A ⋅ - 32 - - ( T
Page 36 and 37:
- 34 - - In addition, many reaction
Page 38 and 39:
- 36 - - Arrows in the scheme indic
Page 40 and 41:
- 38 - - formaldehyde (CH2O) and fo
Page 42 and 43: Figure 12: Termination of the low t
Page 44 and 45: - 42 - - The non-carbon radical act
Page 46 and 47: 10.7 List of species Radicals of hy
Page 48 and 49: - 46 - - If a frequency analysis of
Page 50 and 51: - 48 - - 11.5.3 Filtering of sample
Page 52 and 53: - 50 - - The SPL of the cylinder pr
Page 54 and 55: Figure 17: Intensity chart for cyli
Page 56 and 57: - 54 - - 11.7.3 Axial modes Axial w
Page 58 and 59: - 56 - - A case was set up to make
Page 60 and 61: 12 Simulation of detonation phenome
Page 62 and 63: - 60 - - provided more ideal condit
Page 64 and 65: - 62 - - positive in the x- directi
Page 66 and 67: 3,0 x 10 6 2,5 x 10 6 2,0 x 10 6 1,
Page 68 and 69: - 66 - - A detailed drawing of the
Page 70 and 71: - 68 - - In the expressions above,
Page 72 and 73: ( 21) ( 22) - 70 - - The mach numbe
Page 74 and 75: ( 25) - 72 - - Δt v = u ⋅ Δx wh
Page 76 and 77: - 74 - - Figure 29: Development in
Page 78 and 79: - 76 - - 12.5 Observations of deton
Page 80 and 81: - 78 - - On figure 34, the individu
Page 82 and 83: - 80 - - • The engine load obtain
Page 84 and 85: - 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 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 and 136: Page 8 of 21 Figure 10: Steel plate
Page 137 and 138: Page 10 of 21 16.7 kW @ 3000 rpm 17
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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