scholarly journals Effects of internal/external EGR and combustion phase on gasoline compression ignition at low-load condition

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jingyu Gong ◽  
Binbin Yang ◽  
Leilei Liu ◽  
Yue Liang ◽  
Zhifa Zhang ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Load Condition ◽  
Soot Emission ◽  
Compression Ignition ◽  
Total Heat Loss ◽  
Engine Model ◽  
Low Load ◽  
Combustion Phase ◽  
Test Engine ◽  
Hc Emissions

Abstract A single-cylinder test engine model was built by GT-Power software, and the effects of internal exhaust gas recirculation (i-EGR), external EGR (e-EGR), i-EGR/e-EGR coupling and the crank angle degree at which 50% of total heat loss has taken place (CA50) on combustion and emission characteristics of gasoline compression ignition at low-load condition were analysed. The results show that the ignition delay period with e-EGR was extended slightly with the increased EGR ratio, while that with i-EGR strategy first shortened and then extended, and that the optimised indicated thermal efficiency could be achieved using a small amount of i-EGR. With the same EGR ratio, nitrogen oxide (NO X ) emission is more likely to be suppressed by i-EGR, while soot emission was more deteriorated, and the superior trade-off relationship between carbon monoxide (CO)/hydrocarbon (HC) emissions and NO X emission was attained by the combination of lower i-EGR ratios and CA50 closed to top dead centre. When using i-EGR/e-EGR coupling with total EGR ratio being fixed, the indicated thermal efficiency was decreased by increasing i-EGR ratio, while the lower NO X , CO and HC emissions could be realised, but only with the consequence that soot emission increased.

Experimental investigation of diesel/gasoline dual-fuel premixed compression ignition strategies for high thermal efficiency and high load extension

2017 ◽  
Vol 232 (10) ◽  
pp. 1374-1384 ◽  
Author(s):  
Jeongwoo Lee ◽  
Sanghyun Chu ◽  
Kyoungdoug Min ◽  
Hyunsung Jung ◽  
Hyounghyoun Kim ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Ignition Delay ◽  
Load Condition ◽  
High Load ◽  
Premixed Combustion ◽  
Dual Fuel ◽  
Compression Ignition ◽  
Lean Premixed Combustion ◽  
Diesel Injection ◽  
Low Load

In this study, two different operating strategies of gasoline and diesel dual-fuel premixed compression ignition (PCI) were investigated by using a single cylinder compression ignition engine. Verification of high thermal efficiency potential under the low load condition and the suppression of the maximum in-cylinder pressure rise rate (PRRmax) under the relatively high load condition were considered in this study. Two approaches to implement dual-fuel PCI were considered. The first approach (A-mode PCI) was an early diesel injection with very leaner overall equivalence ratio condition. In this case, a high exhaust gas recirculation (EGR) rate was not needed because lean premixed combustion promised to provide low nitrogen oxides (NOx) and particulate matter (PM) emissions. The second method (B-mode PCI) involved the use of a high EGR rate to moderate dual-fuel combustion with adjusting diesel injection timing. The first operating strategy prolonged the ignition delay via early diesel injection and lean mixture condition; in this manner, a high EGR helped to increase ignition delay. The experimental result showed that the A-mode PCI strategy promised higher gross indicated thermal efficiency (GIE) than that of the B-mode PCI. However, the B-mode PCI strategy provided a lower PRRmax than that of the first case. By applying the A-mode PCI, which was implemented by the early diesel injection with overall lean premixed combustion, a high GIE of 47.8 % could be obtained under low speed and low load condition. In addition, the dual-fuel PCI operating range could be increased using a gross indicated mean effective pressure (gIMEP) of 14 bar at 2000 r/min with a low PRRmax of 7 bar/deg (constraint 10 bar/deg) by applying the B-mode PCI strategy, which split the heat release rate (HRR) peaks to enable smooth combustion.

Engine performance and emission characteristics of a compression ignition engine fuelled with diesel/dimethoxymethane blends

2005 ◽  
Vol 219 (7) ◽  
pp. 905-914 ◽  
Author(s):  
Y Ren ◽  
Z H Huang ◽  
D M Jiang ◽  
L X Liu ◽  
K Zeng ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Mass Fraction ◽  
Volume Fraction ◽  
Engine Performance ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Performance And Emission ◽  
Fuel Blends ◽  
Performance And Emissions ◽  
Combustion Phase

The performance and emissions of a compression ignition engine fuelled with diesel/dimethoxymethane (DMM) blends were studied. The results showed that the engine's thermal efficiency increased and the diesel equivalent brake specific fuel consumption (b.s.f.c.) decreased as the oxygen mass fraction (or DMM mass fraction) of the diesel/DMM blends increased. This change in the diesel/DMM blends was caused by an increased fraction of the premixed combustion phase, an oxygen enrichment, and an improvement in the diffusive combustion phase. A remarkable reduction in the exhaust CO and smoke can be achieved when operating on the diesel/DMM blend. Flat NO x/smoke and thermal efficiency/smoke curves are presented when operating on the diesel/DMM fuel blends, and a simultaneous reduction in both NO x and smoke can be realized at large DMM addition. Thermal efficiency and NO x give the highest value at 2 per cent oxygen mass fraction (or 5 per cent DMM volume fraction) for the combustion of diesel/DMM blends.

Parametric Study to Optimize Gasoline Compression Ignition Operation under Low Load Condition Using CFD

2021 ◽  
Author(s):  
Jihad Badra ◽  
Alma Alhussaini ◽  
Jaeheon Sim ◽  
Yoann Viollet ◽  
Amer Amer
Keyword(s):  
Parametric Study ◽  
Load Condition ◽  
Compression Ignition ◽  
Low Load

scholarly journals Effect of Injection Strategies in Diesel/NG Direct-Injection Engines on the Combustion Process and Emissions under Low-Load Operating Conditions

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 990 ◽  
Author(s):  
Jinze Li ◽  
Longfei Deng ◽  
Jianjun Guo ◽  
Min Zhang ◽  
Zhenyuan Zi ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Direct Injection ◽  
Combustion Process ◽  
Combustion Efficiency ◽  
Operating Conditions ◽  
Diffusion Combustion ◽  
Combustion Mode ◽  
Low Load ◽  
Hc Emissions ◽  
Injection Strategies

The direct injection of natural gas (NG), which is an important research direction in the development of NG engines, has the potential to improve thermal efficiency and emissions. When NG engines operate in low-load conditions, combustion efficiency decreases and hydrocarbon (HC) emissions increase due to lean fuel mixtures and slow flame propagation speeds. The effect of two combustion modes (partially premixed compression ignition (PPCI) and high pressure direct injection (HPDI)) on combustion processes was investigated by CFD (Computational Fluid Dynamics), with a focus on different injection strategies. In the PPCI combustion mode, NG was injected early in the compression stroke and premixed with air, and then the pilot diesel was injected to cause ignition near the top dead center. This combustion mode produced a faster heat release rate, but the HC emissions were higher, and the combustion efficiency was lower. In the HPDI combustion mode, the diesel was injected first and ignited, and then the NG was injected into the flame. This combustion mode resulted in higher emissions of NOx and soot, with a diffusion combustion in the cylinder. HC emissions significantly decreased. Compared with PPCI combustion, HPDI had a higher thermal efficiency.

Experimental study on particle size distribution of gasoline compression ignition (GCI) at low-load condition

Fuel ◽  
2021 ◽  
Vol 294 ◽  
pp. 120502
Author(s):  
Binbin Yang ◽  
Leilei Liu ◽  
Shouke Jia ◽  
Fan Zhang ◽  
Mingfa Yao
Keyword(s):  
Experimental Study ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Load Condition ◽  
Compression Ignition ◽  
Low Load

scholarly journals Effects of injection parameters, boost, and swirl ratio on gasoline compression ignition operation at idle and low-load conditions

2016 ◽  
Vol 18 (8) ◽  
pp. 824-836 ◽  
Author(s):  
Janardhan Kodavasal ◽  
Christopher P Kolodziej ◽  
Stephen A Ciatti ◽  
Sibendu Som
Keyword(s):  
Load Condition ◽  
Injection Pressure ◽  
Operating Conditions ◽  
Compression Ignition ◽  
Swirl Ratio ◽  
Injector Nozzle ◽  
Low Load ◽  
Dynamics Simulations ◽  
Compression Ignition Combustion ◽  
Injection Pressures

In this work, we study the effects of injector nozzle inclusion angle, injection pressure, boost, and swirl ratio on gasoline compression ignition combustion. Closed-cycle computational fluid dynamics simulations using a 1/7th sector mesh representing a single cylinder of a four-cylinder 1.9 L diesel engine, operated in gasoline compression ignition mode with 87 anti-knock index (AKI) gasoline, were performed. Two different operating conditions were studied—the first is representative of idle operation (4 mg fuel/cylinder/cycle, 850 r/min), and the second is representative of a low-load condition (10 mg fuel/cylinder/cycle, 1500 r/min). The mixture preparation and reaction space from the simulations were analyzed to gain insights into the effects of injection pressure, nozzle inclusion angle, boost, and swirl ratio on achieving stable low-load to idle gasoline compression ignition operation. It was found that narrower nozzle inclusion angles allow for more reactivity or propensity to ignition (determined qualitatively by computing constant volume ignition delays) and are suitable over a wider range of injection timings. Under idle conditions, it was found that lower injection pressures helped to reduce overmixing of the fuel, resulting in greater reactivity and ignitability (ease with which ignition can be achieved) of the gasoline. However, under the low-load condition, lower injection pressures did not increase ignitability, and it is hypothesized that this is because of reduced chemical residence time resulting from longer injection durations. Reduced swirl was found to maintain higher in-cylinder temperatures through compression, resulting in better ignitability. It was found that boosting the charge also helped to increase reactivity and advanced ignition timing.

Numerical study on the approach for super-high thermal efficiency in a gasoline homogeneous charge compression ignition lean-burn engine

2019 ◽  
pp. 146808741988924
Author(s):  
Hao Yu ◽  
Wanhua Su
Keyword(s):  
Mechanical Strength ◽  
Thermal Efficiency ◽  
Compression Ignition ◽  
Effective Pressure ◽  
Lean Burn ◽  
Brake Thermal Efficiency ◽  
Indicated Mean Effective Pressure ◽  
Combustion Phase ◽  
Pressure Cycle ◽  
Model Engine

The approach for achieving super-high thermal efficiency in a gasoline homogeneous charge compression ignition lean-burn engine was studied using numerical simulation. A model engine was designed based on the split cycles, including the low-pressure cycle consisted of the turbocharger system and the high-pressure cycle controlled by the variable effective compression ratio ( ε) and the exhaust gas recirculation (EGR). Based on the model engine, load (L) – Φoxy (F) – EGR (E) – ε (E) cooperative control strategy was proposed to optimize the thermal efficiency and its interactive mechanism was clarified. The results revealed that the core of the load (L) – Φoxy (F) – EGR (E) – ε (E) strategy was the simultaneous optimization of the combustion process and the specific heat ratio ( γ) contributing to the piston work maximization. The optimum combustion phase was found in the range of 4°–9° crank angle after top dead center, and highest combustion rate under the rough combustion restriction was also required. Under this precondition, reducing ε to retard the combustion phase appropriately could mitigate the EGR usage to improve the γ. Based on the load (L) – Φoxy (F) – EGR (E) – ε (E) strategy, increasing the load was found to improve the thermal efficiency effectively by reducing the heat transfer loss. The highest brake thermal efficiency of 50% was reached when the gross indicated mean effective pressure was increased to 15 bar under the conventional engine condition. Further increasing the gross indicated mean effective pressure to 35 bar with elevated peak cylinder pressure of 400 bar could improve the brake thermal efficiency to 54% under the enhanced mechanical strength condition. To pursue super-high thermal efficiency, the approach of thermal insulation for the engine was proved to be more effective. It showed the potential to achieve the super-high brake thermal efficiency over 60% and maintain clean combustion by adopting the load (L) – Φoxy (F) – EGR (E) – ε (E) strategy in the model engine with thermal insulation and high mechanical strength.

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