Browsing by Author "Srinivasan, Kalyan Kumar"

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    Detailed Characterization of Dual Fuel Low Temperature Combustion with Low Carbon Alternative Fuels
    (University of Alabama Libraries, 2024) Narayanan, Abhinandhan; Srinivasan, Kalyan Kumar
    Growing concerns over climate change is primary driver for "net-zero tailpipe" emissions in transportation and power generation applications. In this regard, alternate fuels and novel combustion technologies such as reactivity controlled compression ignition (RCCI) or dual fuel Low Temperature Combustion (DFLTC) have emerged as viable technologies ready for adoption in heavy duty on- and off-road engines to realize high efficiencies and low engine-out emissions. Candidate fuels for RCCI combustion include liquid high-reactivity fuel (HRF) and liquid/gaseous low-reactivity fuel (LRF) combinations such as diesel-gasoline, diesel-ethanol, diesel-natural gas, diesel-propane, etc. Of particular interest is the replacement of fossil diesel with oxymethyl esters (OMEx) in diesel-NG RCCI combustion. Recent research has shown sustainable pathways to produce OMEx with tailored properties, e.g., density and viscosity similar to that of fossil diesel, in large quantities. This enables OMEx to be used as drop-in replacements to diesel fuel in on- and off-road heavy duty transportation engines with minimal modifications to the fuel system.This dissertation focuses on investigating the nature of combustion and emissions signature from POMDME -, P1P -, and B1B -NG RCCI combustion. Since RCCI combustion leverages a high reactivity fuel (HRF) to ignite a premixed low reactivity fuel (LRF)-air mixture, the relative energy fractions of these fuels play a vital role in dictating the combustion evolution and emissions signature. One issue with HRF-NG RCCI combustion, particularly at low engine loads is cyclic combustion variations and the consequently high engine-out hydrocarbon (mostly unburned methane) and carbon-monoxide (CO) emissions. The studies performed at various energy substitution and loads, helped identify pathways to operate the engine at low loads with reduced cyclic variations, low engine-out hydrocarbon and CO and NOx emissions and "zero" measurable soot emissions with little indicated fuel conversion efficiency-penalties. A significant outcome of this experimental program was the establishment of a direct correlation between cycle-to-cycle IMEP variations and cycle-resolved HC measurements obtained with a fast-FID analyzer. Finally, additional experiments were performed with neat P1P at different speed-load conditions to evaluate its potential as a viable drop-in renewable low carbon, non-sooting alternative to diesel in heavy-duty engines.
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    Multiple injection strategies for reducing HC and CO emissions in diesel-methane dual-fuel low temperature combustion
    (Elsevier, 2021) Hariharan, Deivanayagam; Krishnan, Sundar Rajan; Srinivasan, Kalyan Kumar; Sohail, Aamir; University of Alabama Tuscaloosa; University of Michigan System; University of Michigan
    Dual fuel low temperature combustion (LTC), while promising extremely low engine-out emissions of oxides of nitrogen (NOx) and particulate matter (PM), is beset with high unburned hydrocarbon (HC) and carbon monoxide (CO) emissions, especially at low engine loads. In the present work, diesel dual injection is experimentally shown to achieve simultaneous reduction of HC and CO emissions without compromising NOx and PM benefits. The motivation to use a second late diesel injection (typically after top dead center (ATDC)) is to oxidize HC arising from incomplete methane oxidation in dual-fuel combustion initiated by the first early diesel injection (around 310 CAD). Since the second diesel injection occurs during the expansion stroke, the NOx-formation propensity is reduced due to low local temperatures. The experimental matrix consisted of twenty-two distinct operating points on a single cylinder research engine (SCRE) adapted for diesel-ignited methane dual fueling. All the experiments were performed at a constant intake pressure of 1.5 bar and fixed first diesel injection timing at 310 CAD whereas, the second diesel injection timing was varied between 320 and 375 CAD and the injection pressure was varied between 500 and 1500 bar. In addition to reductions in the following emissions: indicated specific hydrocarbons or ISHC (54%, to 13.7 g/kW-hr), ISCO (46%, to 2.7 g/kW-hr), and indicated specific oxides of nitrogen or ISNOx (7%, to 0.31 g/kW-hr) emissions, an 11% increase in indicated fuel conversion efficiency (IFCE), and a 12% increase in combustion efficiency (eta c) were achieved relative to the baseline single injection (at 310 CAD) dual-fuel LTC. Although smoke emissions increased slightly from 0.03 to 0.06 Filter Smoke Number (FSN), they are still considerably lower than for conventional diesel operation.