Tripropylene Glycol Monomethyl Ether Research Articles

Influence of various cleaning solutions on the geometry, roughness, gloss, hardness, and flexural strength of 3D-printed zirconia

This study aimed to investigate the impact of various cleaning solutions on the geometry, roughness, gloss, hardness, and flexural strength of 3D-printed zirconia. Cleaning solutions, including isopropyl alcohol (IPA, 99.9%), ethyl alcohol (EtOH, 99.9%), and tripropylene glycol monomethyl ether (TPM, ≥ 97.5%), were diluted to a concentration of 70% and categorized into six groups: IPA99, EtOH99, TPM97, IPA70, EtOH70, and TPM70. Zirconia discs, printed via digital light processing, were sintered after cleaning. The geometry, roughness, gloss, hardness, and flexural strength were analyzed. Statistical analysis was performed using one-way ANOVA with Tukey’s post hoc test (p < 0.05). The thickness of TPM70 was the highest. The diameter of TPM70 was significantly larger than that of EtOH99 and IPA70 (p < 0.05). The weight of the TPM groups was significantly higher than that of IPA70 (p < 0.05). The roughness Ra of TPM70 was significantly greater than that of IPA99, EtOH99, and EtOH70 (p < 0.05). The differences in surface gloss, hardness, and flexural strength among the different groups were not statistically significant (p > 0.05). Different cleaning solutions did not affect the surface gloss, hardness, and flexural strength of 3D-printed zirconia. High and low concentrations of the same cleaning solution did not affect the surface gloss, hardness, and flexural strength. IPA70, TPM97, and EtOH can be considered viable post-printing cleaning alternatives to the traditional gold standard, IPA99.

Investigation of the effect of ether oxygenated additives on diesel engine performance, combustion, and exhaust emissions - An experimental approach

Conventional energy sources, including diesel and petrol, are decreasing day by day, while their reserves are limited. However, it is difficult to find alternative fuels to replace them. Hence, to fulfill the growing energy demand and reduce environmental emissions, it is vital to find a wide variety of oxygenated compounds to conventional diesel fuels that show low emission potential from transport engines. In this research, we investigated diesel engine performance, combustion, and exhaust emissions with the addition of 10 %, 15 %, 25 %, and 30 % of three different oxygenated blends, including Diethylene Glycol Dimethyl ether (DGM), Di-n-Butyl Ether (DBE), and Tripropylene-Glycol Monomethyl ether (TPGM). This paper presents the brake-specific fuel consumption (BSFC), Brake Thermal Efficiency (BTE), Brake Mean Effective Pressure (BMEP), and Brake Specific Energy Consumption (BSEC) for these fuel blends. The generated emissions of carbon dioxide (CO2), Carbon Monoxide (CO), and nitrogen oxide (NO) were quantified for four different engine speeds of 1500, 1800, 2000, and 2400 rpm for neat (100 %) oxygenated blends. This research also shows the in-cylinder pressure and heat release rate (HRR) of these three oxygenated blends. The outcome of this paper will help future researchers to develop automobiles and vehicles for oxygenated blends with conventional fuels.

Post-processing of a 3D-printed denture base polymer: Impact of a centrifugation method on the surface characteristics, flexural properties, and cytotoxicity

ObjectivesTo investigate the impact of a centrifugation method on the surface characteristics, flexural properties, and cytotoxicity of an additively manufactured denture base polymer. MethodsThe tested specimens were prepared by digital light processing (DLP). A centrifugation method (CENT) was used to remove the residual uncured resin. In addition, the specimens were post-processed with different post-rinsing solutions: isopropanol (IPA), ethanol (EtOH), and tripropylene glycol monomethyl ether (TPM), respectively. A commercial heat-polymerized polymethyl methacrylate was used as a reference (REF). First, the values of surface topography, arithmetical mean height (Sa), and root mean square height (Sq) were measured. Next, flexural strength (FS) and modulus were evaluated. Finally, cytotoxicity was assessed using an extract test. The data were statistically analyzed using a one-way analysis of variance, followed by Tukey's multiple comparison test for post-hoc analysis. ResultsThe Sa value in the CENT group was lower than in the IPA, EtOH, TPM, and REF groups (p < 0.001). Moreover, the CENT group had lower Sq values than other groups (p < 0.001). The centrifugation method showed a higher FS value (80.92 ± 8.65 MPa) than the EtOH (61.71 ± 12.25 MPa, p < 0.001) and TPM (67.01 ± 9.751 MPa, p = 0.027), while affecting IPA (72.26 ± 8.80 MPa, p = 0.268) and REF (71.39 ± 10.44 MPa, p = 0.231). Also, the centrifugation method showed no evident cytotoxic effects. ConclusionsThe surfaces treated with a centrifugation method were relatively smooth. Simultaneously, the flexural strength of denture base polymers was enhanced through centrifugation. Finally, no evident cytotoxic effects could be observed from different post-processing procedures. Clinical significanceThe centrifugation method could optimize surface quality and flexural strength of DLP-printed denture base polymers without compromising cytocompatibility, offering an alternative to conventional rinsing post-processing.

Influence of postwashing process on the elution of residual monomers, degree of conversion, and mechanical properties of a 3D printed crown and bridge materials.

This study aimed to determine the effects of the postwashing method and time on the mechanical properties and biocompatibility of three-dimensional (3D) printed crown and bridge resin. DLP (digital light processing)-printed specimens produced from Nextdent crown & bridge (C&B) resins were washed separately using an ultrasonic bath and rotary washer with TPM (tripropylene glycol monomethyl ether) for 3min, 6min, 10min, 20min, and 1h. Postcuring was applied for 30min to each specimen after the washing process. The flexural strength, Vickers hardness, water sorption and solubility, degree of conversion (DC), elution of residual monomers, and biocompatibility of the specimens were evaluated. The ultrasonic bath showed greater washing efficacy by reducing the residual HEMA (2-hydroxyethyl methacrylate) from 2.0634ppm to 0.1456ppm and reducing the residual TEGDMA (triethylene glycol dimethacrylate) from 1.4862ppm to 0.1484ppm. With prolonged washing, the flexural strength significantly decreased from 129.67±6.66MPa (mean±standard deviation) to 103.17±7.20MPa, while the Vickers hardness increased slightly for the first 6min and then decreased thereafter significantly. The DC was 87.78±1.34% after 3min and then gradually decreased with extended washing time. The cytotoxicity significantly decreases with the increment of the washing time. The washing effect on the elution of residual monomers was better for an ultrasonic bath than for a rotary washer. Extending the washing time reduces the mechanical properties and cytotoxicity of the Nextdent C&B resin.

Influence of postprocessing rinsing solutions and duration on flexural strength of aged and nonaged additively manufactured interim dental material

Statement of problemAdditive manufacturing procedures for fabricating interim restorations include rinsing postprocessing procedures. However, the impact of different rinsing solutions and times on flexural strength is unknown. PurposeThe purpose of this in vitro study was to assess the influence of the rinsing solutions and duration, as well as accelerated aging (thermocycling) procedures, on the flexural strength and Weibull characteristics of an additively manufactured interim dental material. Material and methodsA bar design (25×2×2 mm) file was used to fabricate all the specimens with 3D printing and an interim material (Nextdent C&B MFH). Five groups were created based on the rinsing solution used during the postprocessing procedures: 91% isopropyl alcohol (IPA) (control or IPA-91), 99% IPA (IPA-99 group), bio-ethyl alcohol 100% (BE group), tripropylene glycol monomethyl ether (TPM) 100% (TPM group), and water miscible formula (Resinaway) (RA group). Each group was divided into 4 subgroups depending on the total rinsing time: 5, 6, 7, and 8 minutes (5, 6, 7, and 8 subgroups). Additionally, each subgroup was distributed between nonaged and aged thermocycling procedures (n=10). Flexural strength measurements were made by using a universal testing machine. Two-parameter Weibull distribution values, including the Weibull modulus, scale (m), and shape (0), were calculated. Three-way ANOVA and pairwise multiple comparison Tukey tests were used to analyze the data (α=.05). ResultsThree-way ANOVA showed that the rinsing solution (P<.001), rinsing time (P=.004), and thermocycling procedures (P<.001) were significant predictors of the flexural strength values obtained. The IPA-91 and IPA-99 groups obtained the highest flexural strength, while the RA, TPM, and BE groups obtained the lowest flexural strength. The 7- and 8-minute subgroups obtained the highest flexural strength, while the 5-minute subgroup obtained the lowest flexural strength. The nonaged specimens obtained significantly higher mean flexural strength values than the aged specimens. ConclusionsThe vat-polymerized additively manufactured interim dental material tested with differing rinsing solutions and times demonstrated significant differences in the flexural strength values measured. Accelerated artificial aging procedures significantly decreased the flexural strength of the vat-polymerized interim dental material tested.

Effects of the Washing Time and Washing Solution on the Biocompatibility and Mechanical Properties of 3D Printed Dental Resin Materials.

Three-dimensional (3D) printing technology is highly regarded in the field of dentistry. Three-dimensional printed resin restorations must undergo a washing process to remove residual resin on the surface after they have been manufactured. However, the effect of the use of different washing solutions and washing times on the biocompatibility of the resulting resin restorations is unclear. Therefore, we prepared 3D-printed denture teeth and crown and bridge resin, and then washed them with two washing solutions (isopropyl alcohol and tripropylene glycol monomethyl ether) using different time points (3, 5, 10, 15, 30, 60, and 90 min). After this, the cell viability, cytotoxicity, and status of human gingival fibroblasts were evaluated using confocal laser scanning. We also analyzed the flexural strength, flexural modulus, and surface SEM imaging. Increasing the washing time increased the cell viability and decreased the cytotoxicity (p < 0.001). Confocal laser scanning showed distinct differences in the morphology and number of fibroblasts. Increasing the washing time did not significantly affect the flexural strength and surface, but the flexural modulus of the 90 min washing group was 1.01 ± 0.21 GPa (mean ± standard deviation), which was lower than that of all the other groups and decreased as the washing time increased. This study confirmed that the washing time affected the biocompatibility and mechanical properties of 3D printed dental resins.

Effects of fuel oxygenation and ducted fuel injection on the performance of a mixing-controlled compression-ignition optical engine with a two-orifice fuel injector

This paper describes results from an optical-engine investigation of oxygenated fuel effects on ducted fuel injection (DFI) relative to conventional diesel combustion (CDC). Three fuels were tested: a baseline, non-oxygenated No. 2 emissions certification diesel (denoted CFB), and two blends containing potential renewable oxygenates. The first oxygenated blend contained 25 vol% methyl decanoate in CFB (denoted MD25), and the second contained 25 vol% tri-propylene glycol mono-methyl ether in CFB (denoted T25). Whereas DFI and fuel oxygenation primarily curtail soot emissions, intake-oxygen mole fractions of 21% and 16% were employed to explore the potential additional beneficial impact of dilution on engine-out emissions of nitrogen oxides (NOx). It was found that DFI with an oxygenated fuel can attenuate soot incandescence by ~100X (~10X from DFI and an additional ~10X from fuel oxygenation) relative to CDC with conventional diesel fuel, regardless of dilution level and without large effects on other emissions or efficiency. This breaks the soot/NOx trade-off with dilution, enabling simultaneous reductions in both soot and NOx emissions, even with conventional diesel fuel. Significant cyclic variability in soot incandescence for both CDC and DFI suggests that additional improvements in engine-out soot emissions may be possible via improved control of in-cylinder mixture formation and evolution.

Influence of the Rinsing Postprocessing Procedures on the Manufacturing Accuracy of Vat-Polymerized Dental Model Material.

To evaluate the influence of rinsing solvents, namely isopropyl alcohol (IPA) and tripropylene glycol monomethyl ether (TPM), and rinsing times (5-, 7-, 9-, and 11-minutes) for the postprocessing procedures on the manufacturing accuracy of an additively manufactured dental model resin material. The standard tessellation language (STL file) of the digital design of a bar (15 mm × 4 mm × 3mm) was obtained. A resin dental material (E-Model Light; Envisiontec, Dearborn, MI) and a 3D printer (VIDA HD; Envisiontec) was selected to manufacture all the specimens using the STL file following the recommended printing parameters at a room temperature of 23 °C. Two groups were generated based on the rinsing solvent used on the postprocessing procedures, namely isopropyl alcohol (IPA-group) and tripropylene glycol monomethyl ether (TPM-group). Each group was further divided into 4 subgroups (IPA-1 to IPA-4 and TPM-1 to TPM-4) depending on the rinsing time performed (5-, 7-, 9-, and 11-minutes). Twenty specimens per subgroup were fabricated. The dimensions (length, width, and height) of all the specimens were measured using a low force digital caliper (Absolute Low Force Caliper Series 573; Mitutoyo, Takatsu-ku, Kawasaki, Kanagawa). Each measurement was performed 3 times and the mean value determined. The volume of each specimen was calculated using the formula V = l × w × h. Shapiro-Wilk test revealed that the data were not normally distributed. Data were analyzed using Kruskal-Wallis (α = 0.05), followed by pairwise Mann-Whitney U tests (α = 0.0018). The IPA groups obtained significantly lower trueness and precision values compared with TPM groups (p < 0.0018). Among the IPA groups, IPA-1 subgroup obtained the highest trueness and precision values compared to the rest of the IPA subgroups. The TPM-1 and TPM-2 subgroups obtained the highest trueness and prevision values among the TPM group and among all the groups tested. No significant difference was found between the TMP-1 and TPM-2 subgroups (p > 0.0018). None of the manufacturing workflows tested were able to manufacture a perfect match of the bar virtual design dimensions. TPM solvent group obtained higher trueness and precision values compared to the IPA solvent group. The IPA-1 subgroup that replicated the manufacturer´s recommendations obtained the highest manufacturing accuracy among the IPA subgroup. TPM solvent used in a rinsing ultrasonic bath between 3 and 4 minutes followed by a second ultrasonic clean bath between 2 and 3 minutes of the just printed vat polymerized dental model specimens obtained the highest manufacturing accuracy values.

Combustion characteristics of oxygenated slurry droplets of nano-Al/EtOH and nano-Al/TPGME blends

In this study, two oxygenated slurry fuels were prepared by blending nano-aluminum (Al) particles (5 wt%) with ethanol (EtOH) and tripropylene glycol monomethyl ether (TPGME), respectively. The prepared oxygenated slurries were suspended as droplets on a thermocouple wire, and a laser ignition testing system was used for investigating their combustion characteristics. Snapshots of the combustion process showed that a slurry droplet of nano-Al/EtOH suffered three continuous stages, namely, an ignition delay stage, a droplet combustion stage, and a core combustion stage. In contrast, a slurry droplet of nano-Al/TPGME suffered only the first two stages during its combustion; however, an additional microexplosion phenomenon was also observed. During the droplet combustion stage, nano-Al/EtOH blend displayed higher average burning rate, but lower droplet surface temperature than nano-Al/TPGME blend. Emission spectra indicated the formation of gas-phase intermediate products, namely, Al, AlO, AlO2, and Al2O, via nano-Al oxidation during the combustion of both types of oxygenated slurry fuels. Nano-Al/EtOH and nano-Al/TPGME blends displayed higher emission spectral intensity of AlO and AlO2, respectively. The normalized ignition delay time of nano-Al/EtOH droplets was 41.3% longer than that of nano-Al/TPGME droplets. However, the normalized total combustion time of nano-Al/EtOH droplets was 26.4% shorter than that of nano-Al/TPGME droplets.

High-Speed Imaging of Spray Formation and Combustion in an Optical Engine: Effects of Injector Aging and TPGME as a Fuel Additive

High-speed imaging of fuel sprays and combustion is conducted on a light-duty optical engine to investigate the effects of injector aging, with a focus on soot. The spray behaviors of one new and one aged injector are compared using Mie-scattering. In addition to this, the combustion process of a baseline diesel fuel and a blend with TPGME (tripropylene glycol monomethyl ether) are compared using natural luminosity (NL) imaging. TPGME is an oxygenated additive which can be used to reduce soot emissions. X-ray tomography of the two injectors demonstrates that the aging does not lead to significant geometry differences, nor to formation of dense internal nozzle deposits. Both injectors show similar liquid penetration and spreading angle. However, the aged injector shows a prolonged injection and more fuel dribbling after the injection events, leading to a higher injection quantity. The fuel quantity difference shows a larger impact on the NL at low load than the TPGME additive, indicating that the in-cylinder temperature is more important for soot oxidation than oxygen concentration under these conditions. At medium load, the NL is much less sensitive to small temperature variations, while the TPGME is more effective for soot reduction.

Performance of new and aged injectors with and without fuel additives in a light duty diesel engine

Two sets of diesel injectors are tested in combination with common fuel additives in a multi-cylinder light-duty diesel engine. One set consists of new injectors and the other is aged by over 100,000 km use in a vehicle. Four fuels are tested with these injector sets to investigate the impact of fuel additives on combustion and emission characteristics. The results show that the aged injectors consistently deliver larger quantities of fuel for a given injection strategy, leading to a higher power output and deviating emissions. This is hypothesized to be due to drift in the injector actuating characteristics. The fuels tested are a baseline diesel quality, and blends of this fuel with three additives: a cetane number improver (2-ethylhexyl nitrate), a soot reducer (tripropylene-glycol monomethyl ether), and a flow improver consisting of quaternary ammonium salts. At the selected low and medium load operating conditions, these additives had a smaller effect on the emissions than the injector ageing, the most notable effect being that TPGME reduces the soot emissions even at the oxygen-rich conditions studied here. These studies will be followed by optical investigations of the in-cylinder effects on spray and combustion characteristics.

Studies on the interactional behaviour of binary liquid mixtures of tripropylene glycol monomethyl ether and butyl amines at different temperatures

In the present study densities, ρ, and speeds of sound u, have been measured for the binary mixtures of tripropylene glycol monomethyl ether with butyl amine, dibutyl amine, and tributyl amine across the entire composition range at temperatures T = (288.15, 293.15, 298.15, 303.15, 308.15) K and experimental pressure p = 0.1 MPa. Experimental densities and speeds of sound data has been used to determine excess molar volumes, isentropic compressibility, molar isentropic compressibility KS,m and its excess counterpart excess molar isentropic compressibility. Deviations in intermolecular free length and deviations in acoustic impedance have also been determined. Further we have also calculated the partial molar volumes for binary mixtures at different temperatures. The variation of these determined parameters with temperature and composition has been discussed with a view to understand molecular interactions present in the binary liquid mixtures of alkoxypropanol and butyl amines. The experimental data has also been fitted with Jouyban-Acree model.

Investigations on the interactions in the Binary Mixtures of Tripropylene Glycol Monomethyl Ether (TPGMME) and 1-Heptanol at Different Temperatures

Densities (ρ) and ultrasonic speeds (u) of the binary liquid mixtures of Tripropylene Glycol Monomethyl Ether (TPGMME) and 1-haptanol have been measured as a function of composition at temperature range of 288.15 to 318.15 K and atmospheric pressure. The measurements have been carried out using an Anton Paar density and speed of sound analyser DSA 5000. Thermodynamic properties like excess molar volumes, isentropic compressibility and molar isentropic compressibility have been calculated by using densities and speed of sound data at various temperatures. Value for excess molar volume is positive for (TPGMME) and 1-haptanol over the entire mole fraction range, and increase with increasing temperature.

The oxidation characteristics of furan derivatives and binary TPGME blends under engine relevant conditions

Furan and its derivatives have been receiving attention as next generation alternative fuels, related to advanced bio-oil production. However, the ignition quality of furans allows their use only as an additive to diesel fuel in CI engines, which potentially requires the continued use of a fossil-derived base fuel. This study first adopts tri-propylene glycol mono-methyl ether (TPGME) as a substitute for diesel fuel with addition of furan and furan derivatives, including 2-methylfuran, 2,5-dimethylfuran, and furfural, thereby removing fossil-derived fuels from the mixture. With this motivation, gas-phase ignition characteristics of furans were investigated in a modified CFR motored engine, displaying an absence of low temperature heat release (LTHR), while n-heptane as a reference fuel shows a strong two-stage ignition characteristic under the same condition. The structural impact of furans is represented as global oxidation reactivities that are as follows: furan < 2-methylfuran < 2,5-dimethylfuran < furfural < n-heptane. The ranking of individual furans is supported by bond dissociation energies of each fuel's functional group substituent on the furan-ring. Ignition characteristics of TPGME display a strong low-temperature oxidation reactivity; however, its reactivity rapidly diminishes with increasing amounts of furan, shutting down low-temperature oxidation paths. The structural impact of furan and methyl-substituted furans on reactivity is significantly muted when blended with TPGME, as observed in a motored CFR engine and a constant volume spray combustion chamber.

Species measurements of the particulate matter reducing additive tri–propylene glycol monomethyl ether

NUIG would like to thank Science Foundation Ireland (SFI) for the funding for this work via their Principal Investigator Program through project number 15/IA/3177. The research leading to these results has received funding from the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no. 291049−2G-CSafe.

A Comparison of Methyl Decanoate and Tripropylene Glycol Monomethyl Ether for Soot-Free Combustion in an Optical Direct-Injection Diesel Engine

Oxygenated fuels have beneficial effects for leaner lifted-flame combustion (LLFC), a nonsooting mode of mixing-controlled combustion associated with lift-off length equivalence ratios below approximately 2. A single-cylinder heavy-duty optical compression-ignition engine was used to compare neat methyl decanoate (MD) and T50, a 50/50 blend by volume of tripropylene glycol monomethyl ether (TPGME) and #2 ultralow sulfur emissions-certification diesel fuel (CF). High-speed, simultaneous imaging of natural luminosity (NL) and chemiluminescence (CL) were employed to investigate the ignition, combustion, and soot formation/oxidation processes at two injection pressures and three dilution levels. Additional Mie scattering measurements observed fuel-property effects on the liquid length of the injected spray. Results indicate that both MD and T50 effectively eliminated engine-out smoke emissions by decreasing soot formation and increasing soot oxidation during and after the end of fuel injection. MD further reduced soot emissions by 50–90% compared with T50, because TPGME could not completely compensate for the aromatics in the CF. Despite the low engine-out soot emissions, both fuels produced in-cylinder soot because the equivalence ratio at the lift-off length never reached the nonsooting limit. With respect to the other engine-out emissions, T50 had up to 16% higher nitrogen oxides (NOx) emissions compared with MD, but neither fuel showed the traditional soot-NOx trade-off associated with conventional mixing-controlled combustion. In addition, T50 had up to 15% and 26% lower unburned hydrocarbons (HC) and CO emissions, respectively, compared with MD.

Development of a reduced tri-propylene glycol monomethyl ether–n-hexadecane–poly-aromatic hydrocarbon mechanism and its application for soot prediction

A reduced chemical kinetic mechanism for tri-propylene glycol monomethyl ether has been developed and applied to computational fluid dynamics calculations for predicting combustion and soot formation processes. The reduced tri-propylene glycol monomethyl ether mechanism was combined with a reduced n-hexadecane mechanism and a poly-aromatic hydrocarbon mechanism to investigate the effect of fuel oxygenation on combustion and soot emissions. The final version of the tri-propylene glycol monomethyl ether–n-hexadecane–poly-aromatic hydrocarbon mechanism consists of 144 species and 730 reactions and was validated with experiments in shock tubes as well as in a constant-volume spray combustion vessel from the Engine Combustion Network. The effects of ambient temperature, varying oxygen content in the tested fuels on ignition delay, spray lift-off length and soot formation under diesel-like conditions were analyzed and addressed using multidimensional reacting flow simulations and the reduced mechanism. The results show that the present reduced mechanism gives reliable predictions of the combustion characteristics and soot formation processes. In the constant-volume spray combustion vessel simulations, two important trends were identified. First, increasing the initial temperature in the constant-volume spray combustion vessel shortens the ignition delay and lift-off length and reduces the fuel–air mixing, thereby increasing the soot levels. Second, fuel oxygenation introduces more oxygen into the central region of a fuel jet and reduces residence times of fuel-rich area in active soot-forming regions, thereby reducing soot levels.

Leaner Lifted-Flame Combustion Enabled by the Use of an Oxygenated Fuel in an Optical CI Engine

Leaner lifted-flame combustion (LLFC) is a mixing-controlled combustion strategy for compression-ignition engines that does not produce soot because the equivalence ratio at the lift-off length, Φ(H), is less than or equal to approximately two. In addition to preventing soot formation, LLFC can simultaneously control emissions of nitrogen oxides because it is tolerant to the use of exhaust-gas recirculation for lowering in-cylinder temperatures. LLFC can be achieved through the use of oxygenated fuels and enhanced fuel/charge-gas mixing upstream of the lift-off length. Enhanced mixing can be obtained via higher injection pressures, smaller injector orifice diameters, lower intake-manifold and coolant temperatures, and/or more retarded injection timings. This study focuses on the effects of an oxygenated fuel blend (T50) made up of 50% by volume tri-propylene glycol mono-methyl ether with a #2 ULSD emissions-certification fuel (CFA), compared against baseline testing of the CFA fuel without the oxygenate. Experimental measurements include crank-angle resolved natural luminosity (NL) and chemiluminescence (CL) imaging diagnostics. EGR is simulated by adding nitrogen and carbon dioxide to the intake charge to produce a 16% intake-oxygen mole fraction (XO2), and results are compared against cases with no charge dilution (i.e., 21% XO2). Initial experiments with a two-hole tip achieved soot-free LLFCmore » at low loads with the T50 fuel, 240 MPa injection pressure, 50 °C intake-manifold temperature (IMT), 95 °C coolant temperature, and -5 crank-angle degree (CAD) after top-dead-center (ATDC) start of combustion (SOC) timing. The strategy was extended to more moderate loads by employing a 6-hole injector tip, where lowering the IMT to 30 °C, reducing the coolant temperature to 85 °C, and retarding the SOC timing to +5 CAD ATDC resulted in sustained LLFC at both 21% and 16% XO2 at up to 6.2 bar gross indicated mean effective pressure (gIMEP) with T50. The achievement of LLFC was confirmed by independent soot measurements using a smoke meter, spatially integrated natural luminosity from the NL diagnostics, and laser-induced incandescence for measuring soot volume fraction in the exhaust stream. In contrast to the results with T50, LLFC was not achieved under any of the test conditions with CFA. Combustion was stable under LLFC conditions, with a coefficient of variation of gIMEP less than 1.5%. Nitrogen oxides and hydrocarbon emissions were also lowered by up to 25% each for LLFC with T50 relative to using the same operating conditions with CFA. Combustion noise was similarly reduced by 4-6 dBA, and ringing intensity by 60-80%, for LLFC with T50.« less

Investigation of a tripropylene-glycol monomethyl ether and diesel blend for soot-free combustion in an optical direct-injection diesel engine

Natural luminosity and chemiluminescence imaging diagnostics were employed to investigate if a 50/50 blend by volume of tripropylene-glycol monomethyl ether (TPGME) and ultra-low sulfur #2 diesel certification fuel (CF) could enable leaner-lifted flame combustion (LLFC), a non-sooting mode of mixing-controlled combustion associated with equivalence ratios below approximately 2. The experiments were performed in a single-cylinder heavy-duty optical compression–ignition engine at three injection pressures and three dilution levels. Results indicate that TPGME addition effectively eliminated engine-out smoke emissions by curtailing soot production and/or increasing soot oxidation during and after the end of fuel injection. TPGME greatly reduced soot luminosity when compared with neat CF, but did not enable LLFC because the equivalence ratios at the lift-off length, ϕ(H), never reached the non-sooting limit and incandescence from hot soot within the combustion chambered remained visible. Concerning other engine-out emissions, injection pressure influenced the effects of TPGME addition on NOx emissions. HC and CO emissions were higher compared to the baseline fuel, likely due to the lower net heat of combustion of TPGME and the need to limit fuel-injection duration for valid optical measurements.

Experimental and kinetic modeling study of the shock tube ignition of a large oxygenated fuel: Tri-propylene glycol mono-methyl ether

Tri-propylene glycol monomethyl ether (TPGME) is an important oxygenated fuel additive that can be used to reduce soot in diesel engines. However, a validated chemical kinetic model that incorporates the low- to high-temperature chemistry, needed to simulate ignition in a diesel engine is not available for TPGME. In addition, no fundamental experimental data are available that can be used to validate a TPGME mechanism. In this study, a surrogate chemical kinetic model for TPGME that includes low- and high-temperature chemistry has been developed, and shock tube ignition delay time data has been acquired for its validation at 0.25% TPGME for temperatures in the range of 980–1545K, at pressures of 10 and 20atm, and at equivalence ratios of φ=0.5, 1.0 and 2.0. The predictions from the model have been compared to the experimental measurements with good agreement. Under the experimental conditions investigated in the shock tube, TPGME was found to be consumed by molecular elimination reactions and also H-atom abstraction by Ḣ atoms and by ȮH and HȮ2 radicals. In performing sensitivity analyses it was found that the ignition of TPGME is most sensitive to reactions involving propene. Considering how the sensitivity analyses change with pressure, the most sensitive reactions involved Ḣ atoms at 10atm and HȮ2 radicals at 20atm. With respect to the effect of equivalence ratio, reactions involving Ḣ atoms are relatively more sensitive under fuel-rich conditions while those involving HȮ2 radicals are relatively more sensitive under fuel-lean conditions. Further experimental work is needed to enable validation of the model under low-temperature conditions. TPGME was compared to n-heptane which has similar ignition properties based on Cetane Number. Predictions showed that TPGME has a higher overall reactivity compared to n-heptane. In addition, TPGME is shown to produce significantly less soot precursor species when TPGME predictions are compared to n-heptane.