Troels Dyhr Pedersen.indd - Solid Mechanics

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7 Combustion of DME - 20 - - 7.1 Combustion stoichiometry The ideal combustion of DME in dry air is described by the reaction: λ ⋅ ⋅ ( 3. 76N + O ) + CH OCH → 3H O + 2CO + λ ⋅11. 28N + 3⋅ ( λ −1) ⋅O + 1329 kJ / mol 3 2 2 3 3 2 2 2 2 The stoichiometric fuel to air ratio (FA ratio) is derived: 3 mole ⋅ ( 3. 76 ⋅ 28. 01 g / mole + 32. 00 g / mole) + 1 mole ⋅ 46. 07 g / mole = 411. 95 g + 46. 07 g FA S , DME m = m fuel air 46. 07 g = = 411. 95 g 0. 1118 The equivalence ratio is given as the ratio of the actual FA ratio to the stoichiometric FA ratio: FA φ = FAS The typical equivalence ratio in engine experiments with DME is from 0.2 to 0.5. 7.2 Physical and chemical properties of DME Table 1: Properties of DME Chemical formula: CH3OCH3. Chemical weight: 46.07 g/mol. Melting point: -141 °C Boling point at atm. pressure: -24.4 °C Vapor pressure at 20 °C: 5.1 bars Critical pressure: 53.7 bars Critical temperature: 126.9 °C Heat of combustion, LHV: 28.84 MJ/kg Heat of vaporization at -20 °C: 410.2 kJ/kg Auto ignition temperature: 235 °C Flash point: -41 °C Flammability limit in air 3.4-17 vol. % The data are supplied by Haldor Topsøe A/S. More information about DME is available at [12]. DME has a cetane rating in the range of 55-60. The cetane ranking means that DME has a shorter delay than diesel fuel, which has a cetane ranking of 40-46 (45-50 for premium diesel).
- 21 - - 7.3 Development in the use of dimethyl ether as a fuel As oil derived fuels are becoming increasingly harder to exploit and hence more expensive, alternative fuels are starting to become both economically and politically attractable. In a future society it is most likely that a variety of sources are used to produce a variety of fuels for engines. The sources will likely be prioritized such that those domestically available will be given a primary role in the supply chain. A prime example of a nation shifting its focus from oil towards its domestic resources is China, which is undoubtedly the leader within DME production. The wish to avoid dependence on fuel import has led the country to utilize its coal resources for fuel production. Coal is now utilized to produce large quantities methanol, ethanol and DME. As of 2009, the country has capacity to produce more than 7 million tons of DME per year, a capacity which is expected to be near 15 million tones per year in 2010 [13]. The current production is used mainly as a supplement to LPG which has similar properties. The situation in China is therefore that DME is now commonly available in large quantities. There are a small number of buses in Shanghai that has been converted to DME and are operating in the city. In Japan, a few small scale DME plants have been built so far, and a small fleet of trucks are currently being tested [14, 15 and 16]. The National Traffic Safety and Environmental Laboratories (NTSEL) have been responsible for converting the trucks and engines. The government has taken large steps to the protection of the air quality in Tokyo, by implementing strict regulations for all vehicles. As an example, all diesel trucks operating within the city limits are required to be fitted with particulate filters. It is therefore likely that Japan will increase their efforts towards implementing DME as a diesel substitute in the future. The question remains which resources will be used for the production of DME, given that Japan does not have coal or natural gas, and thus are forced to import the feedstock for the production.
Page 1: Homogeneous Charge Compression Igni
Page 4 and 5: - 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
Page 10 and 11: 3 Résumé - 8 - - This thesis is b
Page 12 and 13: 4 Resumé (dansk) - 10 - - Denne af
Page 14 and 15: 5 Introduction - 12 - - 5.1 About H
Page 16 and 17: - 14 - - 5.3 Scope of investigation
Page 18 and 19: 6 The basics of HCCI combustion - 1
Page 20 and 21: - 18 - - the cylinder. In HCCI comb
Page 24 and 25: - 22 - - 8 Description of experimen
Page 26 and 27: - 24 - - 8.1.3 Piston modifications
Page 28 and 29: - 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
Page 34 and 35: 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,
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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
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- 84 - - 15 Appendix A: Reduced sch
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16 Appendix B: Detonation model in
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- 88 - - 17 Paper I: The Effect of
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- 90 - - 19 Paper III: Reducing HCC
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DESCRIPTION OF THE EXPERIMENT OBJEC
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Engine modification To obtain a low
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Pressure [Mpa] 6 5 4 3 2 1 lambda 2
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Pressure [Mpa] 6 5 4 3 2 1 lambda 4
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At lambda 4, IMEP peaks at a compre
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CONCLUSION • It was possible to a
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close to the lean limit. HC is comp
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Reactions do however not stop entir
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METHANOL TEST PROCEDURE In the firs
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Page 8 of 22 0 -5 -10 -15 -20 -25
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With EGR there was a notable change
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Page 12 of 22 9 8 7 6 5 4 3 2 MEOH
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Page 14 of 22 250 200 150 100 50 40
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EMISSIONS The emissions in table 6
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Page 18 of 22 15 12 9 6 3 0 1000 RP
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REFERENCES 1. Mingfa Yao: An Invest
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PM: Particulate matter THC: Total H
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Coupling of pressure waves and reac
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chambers which often have this flat
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The two piston crowns with chambers
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Page 8 of 21 Figure 10: Steel plate
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Page 10 of 21 16.7 kW @ 3000 rpm 17
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v v, ref T T ref with T and Tref be
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dB higher than the 8 cylindrical ch
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Page 16 of 21 Flat chamber 7 BTDC 3
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Page 18 of 21 diesel type chamber 3
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CONCLUSION HCCI combustion generate
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DTU Mechanical Engineering Section
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