Effects of Buffer Gas Composition on Autoignition of Dimethyl Ether
Abstract
:1. Introduction
2. Experimental
2.1. Rapid Compression Machine
2.2. Definition of Ignition Delay and Repeatability of Experiments
2.3. Preparation of Gas Mixture
2.4. Experimental Conditions
Mole proportion | Dilution ratio (%) | φ | Pc (bar) | Tc (K) |
---|---|---|---|---|
Dimethyl ether (DME):O2:N2 = 1:3:20 | 36.31 | 1 | 10 | 670–795 |
DME:O2:N2:Ar = 1:3:10:10 | 36.31 | |||
DME:O2:Ar:CO2 = 1:3:12.245:7.755 | 36.31 | |||
DME:O2:N2 = 1:3:25 | 47.29 | |||
DME:O2:N2 = 1:3:30 | 55.04 |
3. Numerical Simulations
4. Results and Discussion
4.1. Thermal and Chemical Effects of Buffer Gas Composition
Reactions | N2 | Ar | CO2 | Ar/CO2 (61.2%/38.8%) |
---|---|---|---|---|
H + O2 (+M) <=> HO2 (+M) | 1 | 1 | 3.8 | 2.09 |
H2O2 (+M) <=> 2OH (+M) | 1 | 0.64 | 3.8 | 1.87 |
4.2. Dilution Effects of Buffer Gas Composition
5. Conclusions
- (1)
- Both experimental and simulation results show that the buffer gas composition has little impact on the first-stage ignition delay. In the low temperature region, the effects of buffer gas composition on the total ignition delay are also negligible. However, compared to N2, the N2/Ar (50%/50%) mixture reduces the total ignition delay by 31% and 14% in the NTC region for experimental and simulation data, respectively.
- (2)
- For ignition delays of N2 and the Ar/CO2 (61.2%/38.8%) mixture, experimental results show that the chemical effects have little impact on the first-stage and total ignition delays in the conditions studied, whereas the simulation results show that the chemical effects become pronounced at a compressed temperature higher than 770 K.
- (3)
- The simulation results using pure N2, Ar and CO2 as buffer gases show that the thermal effects are the dominant factor in a low temperature and NTC region. The chemical effects become pronounced in the NTC region, and the chemical effect of CO2 exceeds the thermal effect at a compressed temperature higher than 880 K.
- (4)
- With increasing buffer gas dilution ratio, the first-stage ignition delay slightly increases, but the total ignition delay has a significant increase due to the differences in heat release during first-stage ignition for different dilution ratios. The NTC behavior of total ignition delay becomes more pronounced at a high dilution ratio. The heat release during the first-stage ignition decreases with increasing buffer gas dilution ratio. Moreover, the heat release during first-stage ignition is sensitive to buffer gas composition.
Acknowledgments
Author Contributions
Conflicts of Interest
Nomenclature
P0 | Initial pressure (bar) |
T0 | Initial temperature (K) |
Pc | Compressed pressure (bar) |
Tc | Compressed temperature (K) |
Δτt,Ar | Thermal effect index of Ar |
Δτt,CO2 | Thermal effect index of CO2 |
Δτc,Ar | Chemical effect index of Ar |
Δτc,CO2 | Chemical effect index of CO2 |
Greek letters
φ | Equivalence ratio |
γ | Ratio of specific heat |
ε | Compression ratio |
τ1 | First-stage ignition delay |
τ2 | Second-stage ignition delay |
τ | Total ignition delay |
Acronyms
DME | Dimethyl ether |
RCM | Rapid compression machine |
NTC | Negative temperature coefficient |
EGR | Exhaust gas recirculation |
ICE | Internal combustion engine |
HCCI | Homogeneous charge compression ignition |
PCCI | Premixed charge compression ignition |
IMEP | Indicated mean effective pressure |
TDC | Top dead center |
ST | Shock tube |
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Shi, Z.; Zhang, H.; Liu, H.; Lu, H.; Li, J.; Gao, X. Effects of Buffer Gas Composition on Autoignition of Dimethyl Ether. Energies 2015, 8, 10198-10218. https://doi.org/10.3390/en80910198
Shi Z, Zhang H, Liu H, Lu H, Li J, Gao X. Effects of Buffer Gas Composition on Autoignition of Dimethyl Ether. Energies. 2015; 8(9):10198-10218. https://doi.org/10.3390/en80910198
Chicago/Turabian StyleShi, Zhicheng, Hongguang Zhang, Hao Liu, Haitao Lu, Jiazheng Li, and Xiang Gao. 2015. "Effects of Buffer Gas Composition on Autoignition of Dimethyl Ether" Energies 8, no. 9: 10198-10218. https://doi.org/10.3390/en80910198