Engine Knock Rating of Natural Gases—Methane Number

Ryan, T. W.; Callahan, Timothy J.; King, Steven R.

doi:10.1115/1.2906773

Cited by 43 publications

(16 citation statements)

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“…Methane number provides an indication of knocking tendency of natural gas in spark-ignited engines, similar to octane number for liquid fuels. Methane numbers are determined from correlations given by Callahan et al [17]. The composition chosen has a methane number of 91.…”

Section: Natural Gas Compositionmentioning

confidence: 99%

Effects of oil and water contamination on natural gas engine combustion processes

Menon

Ganti

Niemeyer

et al. 2017

Journal of Natural Gas Science and Engineering

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Abundant availability and potential for lower emissions are drivers for increased utilization of natural gas in automotive engines for transportation applications. A novel bimodal engine has been developed that allows on-board refueling of natural gas by utilizing the engine as a compressor. Engine compression however, results in altering the initial state of the natural gas. Increase in temperature and addition of oil are two key effects attributed to the onboard refueling process. A secondary effect is the presence of water in the natural gas supply line. This study investigates the effect of upstream conditions of natural gas on three parameters -autoignition temperature, ignition delay, and laminar flame speed. These parameters play key roles in the engine combustion process. Parametric studies are conducted by varying the initial mixture temperature, water, and oil content in the fuel. The studies utilize numerical simulations conducted with detailed chemistry for natural gas with n-heptane used as a surrogate for oil. Water addition to natural gas at 1-5% by volume did not result in any major changes in the combustion processes, other than a slight reduction in laminar flame speeds. Oil addition of 1-5% by volume reduced autoignition temperature by 5-10% and ignition delay by 27-95% depending on the initial temperature. Sensitivity analysis showed that this was likely due to decrease in the sensitivity of two recombination reactions with oil addition. Evolution profiles of key radical species also showed increasing mole fraction of the hydroperoxy radical at lower temperature that likely aids in reducing the ignition delay. Oil addition resulted in a relatively small increase in the laminar flame speed of 1.7% along with an increase in the adiabatic flame temperature. These results help inform the combustion process and performance to be expected from the bimodal engine.

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Section: Natural Gas Compositionmentioning

confidence: 99%

Effects of oil and water contamination on natural gas engine combustion processes

Menon

Ganti

Niemeyer

et al. 2017

Journal of Natural Gas Science and Engineering

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“…Experimental regions are not always so difficult to find. Ryan et al (1993) describe optimum experiments to determine the methane number of natural gases, the methane number being a measurement of knock in an engine analogous to octane number for liquid fuels. The analysis of the range of paraffins from methane to pentane in natural gases defined the experimental region for a five-component mixture experiment, from which calibration curves were derived.…”

Section: Use Of Optimum Designsmentioning

confidence: 99%

The Usefulness of Optimum Experimental Designs

Atkinson

1996

Journal of the Royal Statistical Society Series B: Statistical Methodology

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SUMMARY Optimum experimental designs were originally developed by Kiefer, mainly for response surface models. This survey of recent developments emphasizes potential or actual usefulness. For linear models the construction of exact designs, particularly over irregular design regions, is stressed, as is the blocking of response surface designs. Other important areas include systematic designs that are robust against trend and designs for mixtures with irregular design regions: several industrial examples are mentioned. Both D‐ and c‐optimum designs are found for a non‐linear model of the economic response of cereal production to fertilizer level, the c‐optimum design being for the conditions of maximum economic return. Locally optimum and Bayesian designs are both described. Similar results for generalized linear models lead to designs for the LD95 in a logistic model in which male and female subjects respond differently. Designs with structure in the variance suggest alternatives to the potentially wasteful product designs of Taguchi. Designs for sequential clinical trials to include random balance are presented. The last section outlines some applications, including life testing and models in which time is a factor.

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“…Further, empirical correlations relate the MON equivalent of natural gas to the methane number, as follows MN = 1.624 MON -119.1 (2) Quadratic expressions are also available, relating the concentrations of individual component gases to the Methane number of the fuel [4]. Overall, the concentration of larger hydrocarbons in natural gas has a dominating effect and it significantly reduces the MN.…”

Section: Gasmentioning

confidence: 99%

“…Table 2. Knock ratings of normal paraffins [4] The knock ratings of various single component fuels are shown in Table 2. As seen, methane by itself being a stable molecule improves knock resistance, whereas long chain hydrocarbons like propane and butane inhibit it significantly.…”

Section: Methane Number (Knock Resistance Of Fuels)mentioning

confidence: 99%