Research and Publications - Alabama Transportation Institute

Permanent URI for this collection

https://ir.ua.edu/handle/123456789/8238

Browse

Browsing Research and Publications - Alabama Transportation Institute by Author "Clemson University"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    A comprehensive experimental investigation of low-temperature combustion with thick thermal barrier coatings
    (Pergamon, 2021) Yan, Ziming; Gainey, Brian; Gohn, James; Hariharan, Deivanayagam; Saputo, John; Schmidt, Carl; Caliari, Felipe; Sampath, Sanjay; Lawler, Benjamin; Clemson University; University of Alabama Tuscaloosa; State University of New York (SUNY) System; State University of New York (SUNY) Stony Brook
    Thick thermal barrier coatings (TBCs) have a significant potential to increase thermal efficiency by reducing heat transfer losses. However, in conventional combustion modes, the drawbacks associated with charge heating and higher propensity to knock have outweighed the efficiency benefits. Since the advanced low-temperature combustion (LTC) concepts are fundamentally different from the conventional combustion modes, these penalties do not exist in most of LTCs. The current experimental study shows the feasibility and benefits of thick TBCs with advanced LTC enabled by two different fuels: conventional gasoline and wet ethanol 80 (WE80, i.e., 80% ethanol and 20% water by mass). A total of five pistons were tested, including two metal baselines and three TBCcoated pistons with different thicknesses or surface finishes. A load sweep was conducted with each fuel on each piston within the same constraints. The thick TBCs extends the low load limit by about 15% for both gasoline and WE80 cases. A deterioration of the high load limit was not observed, which implies that the charge heating penalty does not occur in LTCs. The combustion efficiency increased for the thicker TBC by up to 2% points, and the fuel conversion efficiency was increased by up to 4.3%. The gasoline cases experience the largest benefits at low load, while the wet ethanol experiences the largest benefits at mid-to-high load. The intake temperature requirement is successfully reduced by 10-15 K. It is also observed that the dense sealing layer results in a significant improvement to UHC emissions. All of the coated pistons survived the 10-20 h of engine operation with no visual failure. (c) 2021 Elsevier Ltd. All rights reserved.
  • Thumbnail Image
    Item
    Experimental Study of the Effect of Start of Injection and Blend Ratio on Single Fuel Reformate RCCI
    (ASME, 2020) Hariharan, Deivanayagam; Gainey, Brian; Yan, Ziming; Mamalis, Sotirios; Lawler, Benjamin; University of Alabama Tuscaloosa; Clemson University; State University of New York (SUNY) System; State University of New York (SUNY) Stony Brook
    A new concept of single fuel reactivity-controlled compression ignition (RCCI) has been proposed through the catalytic partial oxidation (CPOX) reformation of diesel fuel. The reformed fuel mixture is then used as the low reactivity fuel and diesel itself is used as the high reactivity fuel. In this paper, two reformate mixtures from the reformation of diesel were selected for further analysis. Each reformate fuel mixture contained a significant fraction of inert gases (89% and 81%). The effects of the difference in the molar concentrations of the reformate mixtures were studied by experimenting with diesel as the direct injected fuel in RCCI over a varying start of injection timings and different blend ratios (i.e., the fraction of low and high reactivity fuels). The reformate mixture with the lower inert gas concentration had earlier combustion phasing and shorter combustion duration at any given diesel start of injection timing. The higher reactivity separation between reformate mixture and diesel, compared with gasoline and diesel, causes the combustion phasing of reformate-diesel RCCI to be more sensitive to the start of injection timing. The maximum combustion efficiency was found at a CA50 before top dead center (TDC), whereas the maximum thermal efficiency occurs at a CA50 after TDC. The range of energy-based blend ratios in which reformate-diesel RCCI is possible is between 25% and 45%, limited by ringing intensity (RI) at the low limit of blend ratios, and coefficient of variance (COV) of net indicated mean effective pressure (IMEPn) and combustion efficiency at the high limit. Intake boosting becomes necessary due to the oxygen deficiency caused by the low energy density of the reformate mixtures as it displaces intake air.
  • Thumbnail Image
    Item
    Exploring the Effects of Piston Bowl Geometry and Injector Included Angle on Dual-Fuel and Single-Fuel RCCI
    (ASME, 2021) Hariharan, Deivanayagam; Boldaji, Mozhgan Rahimi; Yan, Ziming; Gainey, Brian; Lawler, Benjamin; University of Alabama Tuscaloosa; Clemson University
    Reactivity control compression ignition (RCCI) is a low-temperature combustion technique that has been proposed to meet the current demand for high thermal efficiency and low engine-out emissions. However, its requirement of two separate fuel systems (i.e., a low-reactivity fuel system and a high-reactivity fuel system) has been one of its major challenges in the last decade. This leads to the single-fuel RCCI concept, where the secondary fuel (reformates of diesel) is generated from the primary fuel (diesel) through catalytic partial oxidation reformation. Following the in-depth analysis of the reformate fuel (reformates of diesel) and its benefit as the low-reactivity fuel with diesel, the effects of the start of injection (SOI) timing of diesel and the energy-based blend ratio were also studied in detail. In this study, the effects of piston profile and the injector included angles were experimentally examined using both conventional fuel pairs (gasoline-diesel and natural gas-diesel) and reformate RCCI. A validated computational fluid dynamics (CFD) model was also used for a better understanding of the experimental trends. Comparing a reentrant bowl piston with a shallow bowl piston at a constant compression ratio and SOI, the latter showed better thermal efficiency, regardless of the fuel combination, due to its 10% lower surface area for the heat transfer. Comparing the 150-degree included angle and 60-degree included angle on the shallow bowl piston, the latter showed better combustion efficiency, regardless of the fuel combination, due to its earlier combustion phasing (at constant SOI timing). The effect was particularly prominent on reformate RCCI because of its incredibly high diluent concentration, which retards the combustion further for the 150-deg injector. Later, using convergecfd, seven different injector included angles were studied at a constant SOI. With the change in injector included angle, the region of the cylinder targeted by the fuel spray varies significantly, and it was found to have a significant impact on the combustion efficiency and the engine-out emissions. As the injector included angle changed from 60-deg to 150-deg, the combustion efficiency increased by 15% and the CO, NOx, and HC emissions decreased by 96%, 70%, and 86%, respectively.
  • Thumbnail Image
    Item
    Single-fuel reactivity controlled compression ignition through catalytic partial oxidation reformation of diesel fuel
    (Elsevier, 2019) Hariharan, Deivanayagam; Boldaji, Mozhgan Rahimi; Yan, Ziming; Mamalis, Sotirios; Lawler, Benjamin; State University of New York (SUNY) System; State University of New York (SUNY) Stony Brook; Clemson University; University of Alabama Tuscaloosa
    A single-fuel RCCI concept has been proposed to avoid the need for a secondary fuel system required for conventional RCCI by generating the secondary fuel from the primary fuel through catalytic partial oxidation (CPOX) reformation. In conventional RCCI, gasoline or natural gas can be used as the low-reactivity fuel, and diesel can be used as the high-reactivity fuel. In this study, two reformate mixtures generated by reforming diesel fuel at different operating conditions were used as the low-reactivity fuel, with the parent diesel as the high reactivity fuel. The combustion characteristics of reformate-diesel RCCI were compared with the conventional RCCI. A CFD model was also developed and validated against the experimental results. The model was then used to validate a necessary approximation of the reformate mixture's species concentrations. Compared to conventional RCCI fuel pairs, reformate-diesel RCCI shows marginally better thermal efficiency, approximately 10% better THC emissions, approximately 50% lower NOx emissions, and good controllability. Because the reformate mixture has a high concentration of diluents it displaces a large fraction of intake air and acts similarly to EGR. The combustion behavior of reformate-diesel RCCI is in between that of gasoline-diesel and natural gas-diesel conventional RCCI. From the results, it can be concluded that reformate-diesel RCCI is not overly sensitive to the reformation process itself and the exact species concentrations in the reformate mixture. A small change in the start of injection of diesel, blend ratio, and EGR fraction can be used to compensate for reformate mixture concentration differences.