Troels Dyhr Pedersen.indd - Solid Mechanics

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- 18 - - the cylinder. In HCCI combustion however, it is possible to use much higher quantities of EGR since there are no diffusion flames. It is only required that the equivalence ratio is kept below unity. The purpose of using EGR in HCCI engines is not to reduce the formation of nitric oxides, although it does have that effect as well on the already low level of nitric oxide formation. The primary purpose is to affect the combustion phasing. If hot EGR gases are used, either as an internal residual gas or an external un-cooled recycled gas, it advances combustion phasing. Cold EGR gas will usually retard the combustion phasing. The trapped residual gas within the cylinder is sometimes referred to as internal EGR. It has a promoting effect on combustion phasing, due both to its temperature as well as a certain level of radicals. It was used in one of the first successful implementations of HCCI in a gasoline powered two-stroke motorcycle engine, which competed in the Paris- Dakar race. The principle was named Active Thermo-Atmosphere Combustion (ATAC) [11]. 6.4 Thermal efficiency The HCCI concept is, for the time being, only considered practically applicable for part load operation, mainly due to the problems associated with combustion knock and engine noise. It is therefore not possible for an HCCI engine to obtain the same thermal efficiency as an SI or DI CI engine in full load operation. The indicated efficiency is however excellent with HCCI combustion, since it is close to being an ideal Otto process. Compared with an SI engine in part load operation, HCCI combustion at the same compression ratio is much more efficient. The main reason is that the inlet throttling losses greatly reduces the SI engine efficiency at part load. HCCI combustion may obtain the same efficiency as a diesel engine at part load, provided that the engine compression ratio is equal to a diesel engine. The diesel engine does not have throttling losses other than that produced by the EGR system. Combustion duration is longer for diesel engines, but the combustion efficiency is very high and the heat loss is low. The HCCI engine combustion efficiency is not as high as the diesel, which offsets the advantage of a faster combustion. 6.5 Emission characteristics One major advantage of the HCCI concept is that the lean and premixed combustion reduces the formation of harmful pollutants, mainly particulate matter and nitric oxides. Particulate matter is not formed since the combustion is fully premixed with a large excess of oxygen. Formation of particulate matter from the lubricating oil is still taking place, but the amount of PM related to combustion of lubrication oil is hardly measurable. As for NO formation it is very low, typically in the order of 10-50 ppm. The combustion temperature is below the level where the rate of production for NO becomes significant.
- 19 - - Elevated levels of hydrocarbons from crevice volumes and carbon monoxide are easily dealt with in a simple oxidation catalyst. After treatment systems for HCCI are therefore relatively inexpensive, compared to the cost of particulate filters and catalytic converters.
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 22 and 23: 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
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,
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
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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
Page 94 and 95:
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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