Numerical Study of Knocking Combustion in a Heavy-Duty Engine under Plateau Conditions
Abstract
:1. Introduction
2. Experimental Methods
3. Numerical Methodology
4. Numerical Model Setup
5. Validation of Numerical Modeling
6. Numerical Results and Discussions
7. Conclusions
- 1.
- A numerical model was validated with the optical data of spray behavior and the pressure trace measured by a test bench.
- 2.
- Long ignition delay, rapid premixed and low combustion efficiency were observed under the condition of knocking combustion.
- i.
- The decreases in compression pressure and temperature at 4.5 km led to over 4 °CA longer ignition delays than those at 1 and 3 km.
- ii.
- The main combustion durations from CA10 to CA90 at 1, 3, and 4 km were 59.9, 53.5, and 15.8 °CA, respectively, and the durations from CA10 to CA50 were 14.4, 12.6, and 1.6 °CA. Thus, compared to typical diffusion combustion at 1 and 3 km, premixed combustion dominated at 4.5 km.
- iii.
- The combustion efficiency decreased from 90% to 47% when the combustion changed from normal combustion to knocking combustion due to severe spray impingement.
- 3.
- The processes of end-gas ignition, sequential combustion, and pressure oscillation in the knocking combustion were revealed by the numerical modeling results.
- i.
- A deflagration was initiated by the end-gas with the ignitable mixture near the wall due to severe spray impingement.
- ii.
- Instead of typical multiple-ignition, the chemical heat release from the deflagration led to the thermal expansion of the burned zone, which compressed the surrounding unburned mixture to high pressure and high temperature. The deflagration flames propagated in the surrounding unburned mixture along the periphery of the cylinder.
- iii.
- Due to the thermal expansion of end-gas ignition, the pressure wave propagated from the one side to the other side of the cylinder within 0.8 °CA, and the mean propagation velocity of pressure wave was 1364 m/s. A typical reciprocating pressure oscillation was observed.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
Abbreviations
AMR | Adaptive Mesh Refinement |
ATDC | After Top Dead Center |
BTE | Brake Thermal Efficiency |
CA | Crank Angle |
CFD | Computation Fluid Dynamics |
CI | Compression-Ignition |
CNERI | China North Engine Research Institute |
COV | Cycle-to-Cycle Variation |
IM EP | Indicated Mean Effective Pressure |
KI | Knock Intensity |
LES | Large Eddy Simulation |
MP | Monitor Point |
PPRR | Peak Pressure Rise Rate |
PSD | Power Spectral Density |
SI | Spark-Ignition |
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Submodel | Name |
---|---|
Turbulence | LES |
Evaporation | Frossling |
Droplet breakup | KH |
Spray–wall interaction | Bai–Gosman |
Collision | NTC |
Combustion | Four species skeletal oxidation mechanism [17] |
Altitude (km) | 4.5 | 3 | 1 |
---|---|---|---|
Mean pressure @IVC (kPa) | 85 | 154 | 180 |
Mean temperature | 402 | 422 | 422 |
@IVC (K) | 550 | 550 | 550 |
Piston temperature (K) | 450 | 450 | 450 |
Liner temperature (K) Head temperature (K) | 500 | 500 | 500 |
Injection quantity per cycle (mg) | 225 | 225 | 225 |
Altitude (km) | 4.5 | 3 | 1 |
---|---|---|---|
Maximum combustion pressure (MPa) | 6.1 | 8.5 | 9.5 |
Related crank angle of maximum combustion pressure (°CA) | 4.2 | 7.5 | 7.5 |
PPRR (MPa/°CA) | 3.5 | 2.4 | 0.9 |
Related crank angle of PPRR (°CA) | −2.5 | −7.3 | −7.8 |
Maximum combustion temperature (K) | 2350 | 2154 | 2090 |
Total mass of droplets hitting the wall (mg) | 136 | 14.5 | 7.2 |
Maximum of heat release rate (J/°CA) | 3040 | 2078 | 1936 |
Crank angle of maximum of heat release rate (°CA) | −2.5 | −7.3 | −7.7 |
Integrated heat release (J) | 5050 | 8610 | 9769 |
CA10 (°CA ATDC) | −3.1 | −7.3 | −7.7 |
Combustion efficiency | 47% | 81% | 91% |
CA50 (°CA ATDC) | −1.5 | 5.3 | 6.7 |
CA90 (°CA ATDC) | 12.7 | 46.2 | 52.2 |
Ignition delay (°CA) | 10.9 | 6.7 | 6.3 |
Combustion duration (°CA) | 15.8 | 53.5 | 59.9 |
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Li, H.; Zhang, X.; Li, C.; Cao, R.; Zhu, W.; Li, Y.; Liu, F.; Li, Y. Numerical Study of Knocking Combustion in a Heavy-Duty Engine under Plateau Conditions. Energies 2022, 15, 3083. https://doi.org/10.3390/en15093083
Li H, Zhang X, Li C, Cao R, Zhu W, Li Y, Liu F, Li Y. Numerical Study of Knocking Combustion in a Heavy-Duty Engine under Plateau Conditions. Energies. 2022; 15(9):3083. https://doi.org/10.3390/en15093083
Chicago/Turabian StyleLi, Haiying, Xiaoqin Zhang, Chaofan Li, Rulou Cao, Weiqing Zhu, Yaozong Li, Fengchun Liu, and Yufeng Li. 2022. "Numerical Study of Knocking Combustion in a Heavy-Duty Engine under Plateau Conditions" Energies 15, no. 9: 3083. https://doi.org/10.3390/en15093083