Troels Dyhr Pedersen.indd - Solid Mechanics

More documents

Recommendations

Info

- 26 - - combustion event is often very fast. Additionally, as a consequence of knocking combustion, there is usually a range of high frequencies present in the combustion chamber. It is therefore required that the sampling frequency is at least twice the highest frequency present in the chamber to avoid aliasing and erroneous measurements. When sampling 10 times per CAD, the sampling frequency becomes 72 kHz at 1200 rpm and the highest frequency that may be detected is therefore 36 kHz. This should be sufficient since the resonance frequencies are usually not higher than 15-20 kHz. It is necessary to correct the signal for zero level deviation, which can only be done by estimating the cylinder pressure. This is a source of some error in the heat release analysis, where pressure is relatively low in a large part of the cycle. A deviation of +/- 0.1 bar is however insignificant at higher pressures where the heat release is to be calculated, and the IMEP calculation is not affected at all since the error is the same during compression and expansion.
9 Heat release calculations - 27 - - 9.1 The Heat Release analysis In order to visualize the rate of the combustion it is necessary to perform a heat release analysis. This analysis can provide the crank angle resolved rate of combustion. The heat release analysis [18] looks as follows: dQ V HR dQwall d( m c T ) γ dV 1 dp + + = p ⋅ + V ⋅ dθ dθ dθ γ − 1 dθ γ − 1 dθ In this expression the terms on the left hand side are the chemical heat release, the wall heat transfer and the energy loss related to mass escaping the process. The mass loss is most often insignificant and is therefore usually not included. The heat transfer is in the order of +/- 2 Joule per CAD for a 1 liter cylinder. The heat release is in the order of 10-100 Joule per CAD or higher. The magnitude and shape of the heat release rate are therefore not affected much by the heat transfer. In many situations it is therefore irrelevant to improve the accuracy with the additional term for heat transfer. Only if the accumulated heat release and combustion efficiency is of interest should this be required. 9.2 Location of TDC The mechanical TDC position of the engine is possibly the most critical parameter in the heat release analysis. The impact of a deviation between the estimated and real TDC position on the IMEP with a typical combustion cycle can be seen in table 2. Table 2: Influence of TDC offset on IMEP calculation Position offset (CAD) -2.0 -1.0 -0.5 -0.1 0 +0.1 +0.5 +1.0 +2.0 IMEP 406 446 467 483 487 491 507 527 567 Deviation (%) -16 -8 -4 -0.8 0 +0.8 +4 +8 +16 It is clear that even a minor deviation from the correct TDC results in a significant error in the IMEP calculation. The peak pressure may be used as a preliminary indicator of the TDC. This assumption will result in a certain deviation depending on the engine size, as heat losses will reduce the pressure and cause it to peak shortly before TDC. For 4-stroke engines in typical vehicles the peak pressure may appear around 0.5 CAD before TDC, whereas for small two stroke engines the peak pressure may appear as much as 2 CAD before TDC due to relatively high heat losses in such small engines. It is possible to locate the TDC with reasonable accuracy with the cylinder head removed. Positioning the crank angle encoder so that the z-pulse occurs exactly in this position is
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 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 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
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 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 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
show all

Troels Dyhr Pedersen.indd - Solid Mechanics

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?