Experimental Investigation of Low Temperature Diesel Combustion Processes

Journal of Engineering for Gas Turbines and Power

et al. 2012

Self Cite

This work elucidated which engine operating parameters have the greatest influence on Low temperature diesel combustion (LTC) and emissions. Key parameters were selected and evaluated at low and intermediate speed and load conditions using fractional factorial and Taguchi orthogonal experimental designs. The variations investigated were: about ± 5% in EGR rate, fuel injection quantity and engine speed respectively; and ± we in intake charge temperature. The half-fractional factorial results showed that the interactions among these parameters were negligible for a specific load/speed point. The Taguchi orthogonal method could be used as an efficient DoE tool for studying the multi-parameter 'small-scale transients' that a diesel engine would be likely to encounter when operating in LTC modes. LTC showed the most significant sensitivity to EGR rate variations, where an increase from 60% to 63% in EGR rate doubted THC and CO emissions and reduced combustion stability. LTC was also sensitive to the fuel injection quantity with an increase in injected mass lowering the overall oxygen-fuel ratio and thereby increasing THC and CO emissions. These two parameters influenced the oxygen concentration in the intake charge; which was identified to be a decisive parameter for the LTC combustion and emissions. Intake charge temperature affected the total charge quantity trapped in the cylinder and showed noticeable influence on CO emissions for the low speed intermediate load condition. Variations in engine speed showed a negligible influence on the LTC combustion processes and emissions.

“…2. The combustion processes indicated by the heat release profiles show typical fully premixed two-stage low temperature diesel combustion processes in the test engine [4].…”

Section: Selection Of the Experimental Parameters (Factors)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental Study of Low Temperature Diesel Combustion Sensitivity to Engine Operating Parameters

McTaggart-Cowan

Cong

Journal of Engineering for Gas Turbines and Power

et al. 2012

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“…The energy release rates calculated from the in-cylinder pressure are shown in Figure 7(a) (Figure 7(b), the FOV integrated net luminosity, is discussed later). The energy release rates in Figure 7 demonstrate a negative temperature coefficient (NTC) regime 34 prior to the onset of the main combustion phase. The NTC phase occurs slightly earlier with higher boost pressures.…”

Section: Resultsmentioning

confidence: 99%

The impact of intake pressure on high exhaust gas recirculation low-temperature compression ignition engine combustion using borescopic imaging

Sarangi

International Journal of Engine Research

McTaggart-Cowan

et al. 2020

In diesel engines, high levels of exhaust gas recirculation can be used to achieve low-temperature combustion, resulting in low emission levels of both nitrogen oxides (NO x) and particulate matter. This work studied the effects of varying the intake manifold pressure on in-cylinder combustion processes and engine-out emissions from a light-duty single cylinder diesel engine under conventional and high exhaust gas recirculation low-temperature combustion regimes. The work was conducted at a part-load cruise condition of 1500 r/min and at an indicated mean effective pressure of approximately 600 kPa. Exhaust gas recirculation rates were varied between 0% and 65% at absolute intake pressures of 100–150 kPa. Very low NO x emissions were achieved (<10 ppm, ∼0.05 g/kW h) for intake oxygen mass fractions below about 11%, independent of boost pressure. Smoke emission levels were lower than for non–exhaust gas recirculation combustion at oxygen mass fractions below ∼9%, depending on the boost pressure. High intake pressures reduced fuel consumption by 15% and combustion by-product emissions by 50%–60% compared to low boost. For the low intake boost case, little visible flame was apparent through borescope imaging. At higher boost pressures, intense flame luminosity was observed within the piston bowl early in the expansion stroke. Spatially averaged soot luminosity based on photomultiplier tube data showed that peak soot luminosity was five times greater and occurred 8 °CA earlier for high boost. This work demonstrates how the combination of appropriate boost pressures and exhaust gas recirculation rates can be used to mitigate the emissions and thermal efficiency penalties of high-dilution low-temperature combustion to achieve near-zero NO x operation.

“…This LTHR region is followed by a region of rapid high-temperature heat release (HTHR) corresponding to combustion of the premixed fraction of the charge and then by a significantly slower mixing-limited heat release phase as the in-cylinder charge begins to cool with expansion. As shown in Figure 3, and following the work of Cong et al, 16 we define the start of LTHR (SOL) as the CA where the heat release rate is first positive (corresponding to the minimum value of the integrated heat release curve), and the ignition delay of the low-temperature heat release (IDL), as the duration from start of fuel injection (SOI) to SOL. The duration of the low-temperature phase of combustion (DurL) is then defined as the duration between SOL and the 5% heat release crank angle (CA5).…”

Section: Resultsmentioning

confidence: 99%

Effects of intake-port throttling on combustion behaviour in diesel low-temperature combustion

Sogbesan

International Journal of Engine Research

Davy

2017

Citation: SOGBESAN AbstractThis paper describes the effects of intake-port throttling on diesel low temperature combustion (LTC) at a low and medium load condition. These conditions were known for their characteristically high hydrocarbon (HC) emissions predominantly from over-mixed and under-mixed mixture zones respectively. The investigation was carried out to supplement current findings in literature with valuable information on the formation of HC emissions with increasing swirl levels generated by intake-port throttling. This was achieved through the use of cycle-resolved HC measurements in addition to cycle averaged emissions and in-cylinder pressure-derived metrics. While there was negligible overall effect at the moderately-dilute lowload conditions, increasing swirl has been shown to be beneficial to premixing efficacy under highly dilute conditions with extended ignition delay. This potential advantage was found to be nullified by the swirlinduced confinement of fuel and combustion products to the central region of the cylinder leading to poor late cycle burn rates and increased smoke emissions. HC emissions from the squish and head quench regions were reduced by an increase in swirl ratio.