Effect of diesel pre-injection timing on combustion and emission characteristics of compression ignited natural gas engine

Xu, Min; Wei, Cheng; Zhang, Hongfei; An, Tong; Zhang, Shaohua

doi:10.1016/j.enconman.2016.02.054

Cited by 50 publications

(16 citation statements)

References 27 publications

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“…The reason behind this is the earlier start of combustion (SOC) associated with the use of pre-injection in PPDF, where the presence of active radicals from the LTR zone promote the combustion process. The earlier start of that intensified combustion yields higher cylinder pressure values [9]. The effect is more voluminous at high %CH4, as conventional DDF combustion at these conditions exhibits prolonged combustion duration (as demonstrated in Fig.…”

Section: Resultsmentioning

confidence: 84%

Effect of Pilot Pre-Injection on Methane-Diesel Dual Fuel Engine Combustion

Hegab¹,

Shayler²

2017

World Congress on Momentum, Heat and Mass Transfer

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Dual fuelling of diesel engines with natural gas (NG), mainly composed of methane, is considered an attractive approach to reduce the dependence on diesel fuel and provide a more eco-friendly alternative to conventional diesel engines. In this fuelling strategy, most of the engine power output is provided by the NG, while a pilot amount of diesel fuel is used as an ignition source to ignite the NG-air mixture. However, this engine configuration suffers from lower thermal efficiency, slower burning rate, increased engine instability, and higher CO and HC emissions; particularly at part loads. The present work aims at investigating the effect of using pilot pre-injection (i.e. splitting the diesel pilot into a main injection preceded by a pre-injection) on dual fuel engine combustion and performance at part load conditions. The experiments were conducted on a modern automotive direct injection (DI) diesel engine; properly modified to suite dual fuel operation with methane and diesel. The tests were performed at different engine speeds ranging from 1400 to 2000 rpm at 25% of the engine load at the particular speed, with different substitution ratios of methane for diesel fuel (from 20 to 80% on energy basis). The results demonstrated that optimized pilot pre-injection could bring about a change in the combustion mode from the conventional diesel dual fuel (DDF) combustion to a novel two-stage combustion mode; referred to as partially premixed dual fuel (PPDF) combustion. With this strategy, combustion process becomes more intensified yet smoother, with around 17% lower rate of pressure rise (ROPR) and up to 5% improvement in the brake thermal efficiency. PPDF strategy also maintains the engine stability at acceptable levels (even with high substitution ratios) and allows leaner operation at all conditions; indicating lower levels of harmful emissions.

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Section: Resultsmentioning

confidence: 84%

Effect of Pilot Pre-Injection on Methane-Diesel Dual Fuel Engine Combustion

Hegab¹,

Shayler²

2017

World Congress on Momentum, Heat and Mass Transfer

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“…With FM pre-injection, in contrast, the presence of active radicals from the LTR zone promote the combustion process. The earlier start of that intensified combustion yields higher cylinder pressure values [13]. Furthermore, at the increase in %CH4 takes place on the account of the main injection, the main combustion event will start with an auto-ignition of a less amount of the diesel fuel, and hence the maximum ROPR values are much less; the average reduction in maximum ROPR exceeds 8%.…”

Section: Resultsmentioning

confidence: 99%

Influence of Pilot Pre-Injection Mass on Partially Premixed Dual Fuel (PPDF) Engine Combustion

Hegab¹,

Shayler²

2017

World Congress on Momentum, Heat and Mass Transfer

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-The development of advanced techniques of diesel engines brings many novel ideas to dual fuel engines, where the key to combustion mode change is essentially the optimization of the pilot injection strategy. Splitting the diesel pilot into a main injection preceded by a pre-injection could bring about a change in the combustion mode from the conventional diesel dual fuel (DDF) combustion to the novel partially premixed dual fuel (PPDF) combustion; if the pre-injection part of the pilot is optimized for timing and quantity. In diesel engines with split injection, the pre-injection part is set to a certain percentage of the total diesel fuel supplied to the engine at the particular operating condition. This could be challenging to PPDF combustion, where the relative proportions of gaseous fuel and diesel could change at the same power level produced. With high levels of gaseous fuel substitution, the mass of diesel pre-injection could drop substantially and potentially lose its effect. The present work aims at investigating the influence of pilot pre-injection mass on PPDF combustion and performance at part load conditions. A comparative study was conducted on a modern automotive direct injection (DI) diesel engine working on PPDF with methane and diesel, between two pre-injection strategies; namely the fixed ratio (FR) and the fixed mass (FM). The tests were performed at different engine speeds ranging from 1400 to 2000 rpm at 25% of the engine load at the particular speed, with different substitution ratios of methane for diesel fuel (from 20 to 80% on energy basis). Cylinder pressure, rate of pressure rise (ROPR), coefficient of variation of gross IMEP (COVIMEPgross), heat release rate (HRR), combustion phasing (CA50), brake thermal efficiency, total equivalence ratio, and total diesel fuel injected; are all studied and compared for both pilot pre-injection strategies.

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“…In this sense, Dhar et al [15] studied the effect of a pilot injection, coupled with different fuel formulations, to module the shape of the heat release rate and improve the soot-NO x trade-off. Xu et al [16] observed that an early pre-injection could help to increase thermal efficiency and reduce NO x emissions simultaneously on a natural gas fueled engine. Mahr [13] proposed the addition of a late post injection to improve the soot oxidation process.…”

Section: Introductionmentioning

confidence: 99%

Study of new prototype pintle injectors for diesel engine application

Payri

Morena

Battiston

et al. 2016

Energy Conversion and Management

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a b s t r a c tA new prototype common rail injector featuring a complete new nozzle design concept was exhaustively characterized both from the hydraulic and spray formation point of view. A commercial injection rate meter together with a spray momentum test rig were used to determine the flow characteristics at the nozzle exit. A novel high pressure and high temperature chamber (up to 15 MPa and 1000 K) was used to determine liquid length and vapor penetration. Using these tools, three different pintle nozzle designs, with specific features in the outlet section, were studied. The test matrix included a sweep of injection pressure up to 2000 bar and a sweep of ambient temperature up to 950 K. The results obtained show that pintle nozzles offer great potential in terms of fuel mass flux controlled by variable nozzle geometry. Effects in the hydraulic measurements and spray images due to the variable geometry were observed and characterized.

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Effect of diesel pre-injection timing on combustion and emission characteristics of compression ignited natural gas engine

Cited by 50 publications

References 27 publications

Effect of Pilot Pre-Injection on Methane-Diesel Dual Fuel Engine Combustion

Effect of Pilot Pre-Injection on Methane-Diesel Dual Fuel Engine Combustion

Influence of Pilot Pre-Injection Mass on Partially Premixed Dual Fuel (PPDF) Engine Combustion

Study of new prototype pintle injectors for diesel engine application

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