Scavenging of a Firing Two-Stroke Spark-Ignition Engine

Tobis, Bruce J.; Meyer, R; Yang, Jia; Brehob, Diana D.; Anderson, Richard W.

doi:10.4271/940393

Cited by 9 publications

(8 citation statements)

References 31 publications

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“…Experimental scavenging studies can be categorized in multiple ways, for example engine-based studies or model-based ones. [13][14][15][16][17] based on the nature of the test bed; firing 11,[18][19][20][21] or non-firing studies based on the nature of engine operation; visual 13,14,19,20 or non-visual studies based on the observation tools used; dynamic 14,22,23 or static investigations 15,24 depending on whether the piston is moving or not; and sampling [25][26][27][28][29][30][31][32][33][34] or non-sampling studies based on the drawing (or lack thereof) of gas samples from the engine. Rizk 24 provides a good classification of various investigation methods used in experimental scavenging studies.…”

Section: Scavenging Experimentationmentioning

confidence: 99%

“…Previous tracer sampling-based studies. [25][26][27][28][29] have mostly relied on synchronized electromagnetic or camactuated sampling valves to draw cylinder and/or exhaust samples at appropriate times during gas exchange, that is intermittent sampling. The potential challenges with such studies are: (1) to obtain representative composition samples because of the heterogeneity of the scavenging mixture and (2) to obtain sufficient quantities of the samples that they can be analyzed by an emissions analyzer.…”

Section: Scavenging Experimentationmentioning

confidence: 99%

“…An ambient CO 2 concentration of 400 ppm is used for all TRF calculations. Tobis et al 25 used equation (1) in their intermittent sampling study by disabling fuel injection for the cycle for which the pre-combustion CO 2 concentration was to be measured. Thus, avoiding the fuel dilution problem.…”

Section: Scavenging Analysis Using Cylinder Co 2 Data (Quantitative)mentioning

confidence: 99%

“…Species that are used in sampling studies to track burned gases should have negligible concentration before combustion, be generated during combustion, homogenize quickly in the cylinder gases and should be stable enough to be analyzed outside the cylinder (no “after-reactions” 39 ). CO 5 and CO 2 25 are good burned gas tracers for spark-ignited engines. 36 The species representing fresh charge should be such that they are consumed completely during combustion.…”

Section: Scavenging Experimentationmentioning

confidence: 99%

“…The potential challenges with such studies are: (1) to obtain representative composition samples because of the heterogeneity of the scavenging mixture and (2) to obtain sufficient quantities of the samples that they can be analyzed by an emissions analyzer. To overcome this problem, relatively large quantities of samples have to be drawn and averaged over multiple, non-consecutive cycles (every 15th cycle in Tobis et al 25 ) to get representative composition data. Consecutive cycles cannot be sampled because of the time needed by the engine to recover from the large (greater than 20% of total trapped volume) cylinder gas donation.…”

Section: Scavenging Experimentationmentioning

confidence: 99%

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Experimental investigation of scavenging in two-stroke engines using continuous CO₂ sampling

Bajwa

Patterson

Jacobs

2021

Proceedings of the Institution of Mechanical Engineers, Part D:

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In internal combustion engines, the chemical composition of the trapped fuel-air-residual gas mixture controls the nature of combustion, which, in turn, determines the characteristics of the ensuing emissions and work production processes. Therefore, knowledge of the trapped mixture’s composition is critical for reliably predicting and controlling engine performance, emissions, and efficiency. A good index of the overall trapped mixture composition is the trapped equivalence ratio. Unfortunately, in two-stroke engines, it is unfeasible to accurately determine the trapped equivalence ratio using traditional intake flow measurements and exhaust emissions data. This limitation arises from the simultaneous occurrence of intake and exhaust processes in two-stroke engines, which causes: (1) exhaust emissions to be diluted by excess fresh air that was supplied for achieving effective gas exchange, that is trapping inefficiencies and (2) a significant fraction of combustion products to stay back in the cylinder as residual gas, that is scavenging inefficiencies. The current paper presents an experimental study carried out on a cross-scavenged, lean-burn, natural-gas, two-stroke engine to characterize its scavenging performance, thus paving the way for trapped equivalence ratio computation. CO2 is used as a tracer for combustion products, and its concentration is tracked in the combustion chamber and exhaust manifold on a crank-angle-resolved basis using high-speed nondispersive infrared sensors. The changes in cylinder CO2 concentration before and after gas exchange are used to determine the trapped residual fraction and various features of the exhaust CO2“wave” are used to explain the temporal progression of the gas exchange process. The presented results show the effects of changes in engine operation (speed, load, and spark-timing) on the engine’s scavenging efficiency. Speed and load changes are found to have the most pronounced effects, which result from changes in port open duration and phasing of reflected waves in the exhaust.

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Section: Scavenging Experimentationmentioning

confidence: 99%

Section: Scavenging Experimentationmentioning

confidence: 99%

Section: Scavenging Analysis Using Cylinder Co 2 Data (Quantitative)mentioning

confidence: 99%

Section: Scavenging Experimentationmentioning

confidence: 99%

Section: Scavenging Experimentationmentioning

confidence: 99%

See 3 more Smart Citations

Experimental investigation of scavenging in two-stroke engines using continuous CO₂ sampling

Bajwa

Patterson

Jacobs

2021

Proceedings of the Institution of Mechanical Engineers, Part D:

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Formaldehyde Characterization Utilizing In-Cylinder Sampling in a Large Bore Natural Gas Engine

Olsen

Holden

Hutcherson

et al. 2000

Journal of Engineering for Gas Turbines and Power

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This research addresses the growing need to better understand the mechanisms through which engine-out formaldehyde is formed in two-stroke cycle large bore natural gas engines. The investigation is performed using a number of different in-cylinder sampling techniques implemented on a Cooper-Bessemer GMV-4TF four-cylinder two-stroke cycle large bore natural gas engine with a 36-cm (14-in.) bore and a 36-cm (14-in.) stroke. The development and application of various in-cylinder sampling techniques is described. Three different types of valves are utilized, (1) a large sample valve for extracting a significant fraction of the cylinder mass, (2) a fast sample valve for crank angle resolution, and (3) check valves. Formaldehyde in-cylinder sampling data are presented that show formaldehyde mole fractions at different times during the engine cycle and at different locations in the engine cylinder. The test results indicate that the latter part of the expansion process is a critical time for engine-out formaldehyde formation. The data show that significant levels of formaldehyde form during piston and end-gas compression. Additionally, formaldehyde is measured during the combustion process at mole fractions five to ten times higher than engine-out formaldehyde mole fractions. Formaldehyde is nearly completely destroyed during the final part of the combustion process. The test results provide insights that advance the current understanding and help direct future work on formaldehyde formation.

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Trapped equivalence ratio determination in two-stroke engines

Bajwa

Patterson

Jacobs

2022

Proceedings of the Institution of Mechanical Engineers, Part D:

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The chemical composition of the trapped fuel-air-residual gas mixture controls the nature of combustion in internal combustion engines and thus serves as a key determinant of the ensuing emissions and work production processes. A frequently used trapped composition metric for engine control is the trapped equivalence ratio. Unfortunately, in two-stroke engines, it is unfeasible to accurately determine this using traditional intake flow and exhaust emissions measurements because of the simultaneous occurrence of intake and exhaust processes, which causes: (1) exhaust emissions to be diluted by the slippage (short-circuiting) of fresh air through the exhaust ports, i.e., trapping inefficiencies, and (2) high residual combustion product retainment, i.e., scavenging inefficiencies. The current paper supplements scavenging efficiency data obtained in a previous study for a cross-scavenged, natural-gas, two-stroke engine with experimental trapping efficiency data from the same engine, and characterizes the overall gas-exchange (scavenging + trapping) behavior of the engine at two engine loads, three speeds, and three spark timings. The trapping efficiency experiments use natural gas as a tracer for fresh charge and the total gas-exchange data is used to compute the trapped equivalence ratio. The trapping performance of the engine – which improves with speed and load increase, and spark retardation – along with scavenging, volumetric, thermal, and combustion efficiency changes determine the trapped equivalence ratio of the engine. The relationship between trapped equivalence ratio and NOx emissions is presented and the importance of accounting for scavenging and trapping inefficiencies in accurately determining equivalence ratio is discussed.

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Scavenging of a Firing Two-Stroke Spark-Ignition Engine

Cited by 9 publications

References 31 publications

Experimental investigation of scavenging in two-stroke engines using continuous CO₂ sampling

Experimental investigation of scavenging in two-stroke engines using continuous CO₂ sampling

Formaldehyde Characterization Utilizing In-Cylinder Sampling in a Large Bore Natural Gas Engine

Trapped equivalence ratio determination in two-stroke engines

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Scavenging of a Firing Two-Stroke Spark-Ignition Engine

Cited by 9 publications

References 31 publications

Experimental investigation of scavenging in two-stroke engines using continuous CO2 sampling

Experimental investigation of scavenging in two-stroke engines using continuous CO2 sampling

Formaldehyde Characterization Utilizing In-Cylinder Sampling in a Large Bore Natural Gas Engine

Trapped equivalence ratio determination in two-stroke engines

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Product

Resources

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Experimental investigation of scavenging in two-stroke engines using continuous CO₂ sampling

Experimental investigation of scavenging in two-stroke engines using continuous CO₂ sampling