skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: A parametric study to improve first firing cycle emissions of a gasoline direct injection engine during cold start
A parametric study was carried out for the first firing cycle of a 4-cylinder, 2.0-liter, turbocharged gasoline direct injection (GDI) engine. The primary goal was to see how changes in the fuel injection parameters would affect the GDI engine combustion and emissions for the first four combustion events that constitute the first firing cycle. Experimental studies were carried out with a custom-designed powertrain control system to measure the HC emissions and pressure development for the first firing cycle. The quantitative experimental results were accompanied by simulations of the detailed temporal and spatial fuel concentration profiles using Converge CFD engine simulation software. An alternative calculation method was used to calculate the average combustion equivalence ratio for each of the four cylinders. This method showed that the majority of the cold start HC emissions during the first firing cycle was unburned gasoline and its possible decomposition products, which did not contribute significantly to the combustion and heat release. For the same amount of fuel injected into a cylinder, increased fuel rail pressure resulted in better evaporation and combustion, while slightly increasing the HC emissions during the cold start process. A multiple injection strategy was studied that split the fuel delivery between the intake stroke and the compression stroke with either one or two injections in each of those strokes (two or four injections total). The quadruple injection strategy led to better first cycle combustion, with higher engine IMEP and lower HC emissions. This resulted from a richer fuel mixture in the region near the spark plug due to better fuel evaporation and a better spatial fuel distribution. While increasing fuel rail pressure with either injection strategy failed to significantly lower the HC emissions given the same amount of injected fuel mass, higher rail pressure with the quadruple injection strategy resulted in higher IMEP for the same amount of injected fuel; this may provide the possibility to reduce the total fuel injection mass which may have benefits for both fuel consumption and emissions.  more » « less
Award ID(s):
1650483 2137274
PAR ID:
10398257
Author(s) / Creator(s):
; ; ; ; ; ;
Date Published:
Journal Name:
International Journal of Engine Research
ISSN:
1468-0874
Page Range / eLocation ID:
146808742311533
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. (, ASME ICEF 2020)
    ASME ICEF (Ed.)
    fuel blend consisting of 10% S8 by mass (a Fischer-Tropsch synthetic kerosene), and 90% ULSD (Ultra Low Sulfur Diesel) was investigated for their combustion characteristics and impact on emissions during RCCI (Reactivity Controlled Compression Ignition) combustion in a single cylinder experimental engine utilizing a 65% by mass n-butanol port fuel injection (PFI). RCCI is a dual fuel combustion strategy achieved with the introduction of a PFI fuel of the low-reactive n-butanol, and a direct injection (DI) of a high-reactivity blend (FT-BLEND) into an experimental diesel engine. The combustion analysis and emissions testing were conducted at 1500 RPM at an engine load of 5 bar IMEP (Indicated Mean Effective Pressure), and CA50 of 9° ATDC (After Top Dead Center); CDC (Conventional Diesel Combustion) and RCCI with 65Bu-35ULSD were utilized as the baseline for AHRR (Apparent Heat Release Rate), ringing and emissions comparisons. It was found during a preliminary investigation with a Constant Volume Combustion Chamber (CVCC) that the introduction of 10% by mass S8 into a mixture with 90% ULSD by mass only increased Derived Cetane Number (DCN) by 0.8, yet it was found to have a significant effect on the combustion characteristics of the fuel blend. This led to the change in injection timing necessary for maintaining 65Bu-35F-T BLEND RCCI at a CA50 of 5° ATDC (After Top Dead Center) to be shifted 3° closer to TDC, thus affecting the Ringing Intensity (RI), Pressure Rise Rate, and heat release of the blend all to decrease. CDC was conducted with a primary injection of 14ᵒ BTDC at a rail pressure of 800 bar, all RCCI testing was conducted with 65% PFI of n-butanol by mass and 35% DI, to prevent knock, with a rail pressure of 600 bar and a pilot injection of 60° BTDC for 0.35 ms. 65Bu-35ULSD RCCI was conducted with a primary injection at 6° BTDC with neat ULSD#2, the fuel 65Bu-35F-T BLEND in RCCI had a primary injection at 3° BTDC to maintain CA50 at 9° ATDC. 65Bu-35ULSD RCCI experienced a NOX and soot emissions decrease of 40.8% and 91.44% respectively in comparison to CDC. The fuel 65Bu-35F-T BLEND in RCCI exhibited an additional decrease of NOX and soot of 32.9 and 5.3%, in comparison to 65Bu-35ULSD RCCI for an overall decrease in emissions of 73.7% and 96.71% respectively. Ringing Intensity followed a similar trend with reductions in RI for 65Bu-35ULSD RCCI decreasing only by 6.2% whereas 65Bu-35F-T BLEND had a decrease in RI of 76.6%. Although emissions for both RCCI fuels experienced a decrease in NOX and soot in comparison to CDC, UHC and CO did increase as a result of RCCI. CO emissions for 65Bu-35ULSD RCCI and 65Bu-35F-T BLEND where increased from CDC by a factor of 5 and 4 respectively with UHC emissions rising from CDC by a factor of 3.4. The fuel 65Bu-35F-T BLEND had a higher combustion efficiency than 65Bu-35ULSD in RCCI at 91.2% due to lower CO emissions of the blend. 
    more » « less
  2. ; ; ; (, International Journal of Engine Research)
    A fractal engine simulation (FES) sub-model was integrated into three-dimensional simulations for modeling turbulent combustion for a gasoline direct injection (GDI) engine. The FES model assumes that the effects of turbulence on flame propagation are to wrinkle and stretch the flame, and fractal geometry is used to predict the surface area increase and thus the turbulent burning velocity. Different formulas for the four sequential stages of combustion in SI engines are proposed to account for the changing effects of turbulence throughout the combustion process. However, most prior studies related to the FES model were quasi-dimensional simulations, with few found in multi-dimensional studies, and none under cold start conditions or stratified charges. This paper describes how the model was implemented into multidimensional simulations in CONVERGE CFD, and what the formulas are in the four sequential stages of combustion in SI engines. The capabilities of the FES model for simulating the cold start cases, under the conditions of the dramatically changing engine speed and mixture stratification in a complex engine geometry, are presented in this study. The FES model was able to not only simulate the steady-state cases with constant engine speed, but also predict the in-cylinder pressure traces in all four cylinders for the very first firing cycle with transient engine speed, and gave good agreement with the experimental measurements under these extremely transient conditions. The uncertain maximum fractal dimension was chosen as 2.37 in this research, and a simple linear correlation with engine speed was used to obtain the coefficient used in calculating the kernel formation time which controls the so-called combustion or ignition delay. 
    more » « less
  3. ; ; ; ; ; (, SAE Technical Paper Series)
    The Coal-To-Liquid (CTL) synthetic aviation fuel, Iso-Paraffinic Kerosene (IPK), was studied for ignition delay, combustion delay, pressure trace, pressure rise rate, apparent heat release rate in an experimental single cylinder indirect injection (IDI) compression ignition engine and a constant volume combustion chamber (CVCC). Autoignition characteristics for neat IPK, neat Ultra-Low Sulfur Diesel (ULSD), and a blend of 50%IPK and 50% ULSD were determined in the CVCC and the effects of the autoignition quality of each fuel were determined also in an IDI engine. ULSD was found to have a Derived Cetane Number (DCN) of 47 for the batch used in this experimentation. IPK was found to have a DCN of 25.9 indicating that is has a lower affinity for autoignition, and the blend fell between the two at 37.5. Additionally, it was found that the ignition delay for IPK in the CVCC was 5.3 ms and ULSD was 3.56 ms. This increase in ignition delay allowed the accumulation of fuel in the combustion chamber when running with IPK that resulted in detonation of the premixed air and fuel found to cause high levels of Ringing Intensity (RI) when running neat IPK indicated by the 60% increase in Peak Pressure Rise Rate (PPRR) when compared to ULSD at the same load. An emissions analysis was conducted at 7 bar Indicated Mean Effective Pressure (IMEP) for ULSD and the blend of 50% ULSD and 50% IPK. With the addition of 50% IPK by mass, there was found to be a reduction in the NOx, CO2, with a slight increase in the CO in g/kWh. 
    more » « less
  4. ; ; (, 16th International Conference on Engines & Vehicles)
    Calibration of automotive engines to ensure compliance with emission regulations is a critical phase in product development. Control of engine-out particulate emissions, which directly impact the environment and public health, is particularly important. Detailed physics-based models are typically used to gain a rich understanding of the complex physical phenomena that drive the soot particle formation in an engine cylinder. However, such models often fail to correctly represent the highly dynamic nature of the underlying mechanisms under transient combustion conditions. Moreover, most physics-based models were initially developed for diesel engine applications and their applicability to gasoline engines remains questionable due to differences in flame structure and fuel-wall interactions. Black-box models have been previously proposed to predict engine-out soot emissions, but their lack of physical interpretability is an unsolved drawback. To address these limitations, we present a physics-aware twin-model machine learning framework to predict and analyze engine-out soot mass from a gasoline direct injection (GDI) engine. The framework combines a physics-based model with a bagging-type ensemble learning model that both maintains high accuracy and allows physical interpretation of results without using computationally intensive high-fidelity models. This work shows why a one-model-fits-all approach fails in the case of predicting soot emissions due to clustered co-occurrences of operating conditions that cause non-compliant behavior. We compare the performance of the proposed framework with that of the standalone baseline model and a feed-forward deep neural network. Using WLTP data from a 2.0L naturally aspirated GDI engine, the proposed framework predicts engine-out soot mass with an improvement of 29% in the R2 value and 21% in the root mean squared error from the baseline physics-based model, without compromising physical interpretability. These improvements are significant enough to warrant further framework development with additional engine datasets. 
    more » « less
  5. ; ; ; ; ; (, SAE Transactions)
    SAE (Ed.)
    An investigation of the performance and emissions of a Fischer-Tropsch Coal-to-Liquid (CTL) Iso-Paraffinic Kerosene (IPK) was conducted using a CRDI compression ignition research engine with ULSD as a reference. Due to the low Derived Cetane Number (DCN), of IPK, an extended Ignition Delay (ID), and Combustion Delay (CD) were found for it, through experimentation in a Constant Volume Combustion Chamber (CVCC). Neat IPK was analyzed in a research engine at 4 bar Indicated Mean Effective Pressure (IMEP) at three injection timings: 15°, 20°, and 25° BTDC. Combustion phasing (CA50) was matched with ULSD at 10.8° and 16° BTDC. The IPK DCN was found to be 26, while the ULSD DCN was significantly higher at 47 in a PAC CID 510. In the engine, IPK’s DCN combined with its short physical ignition delay and long chemical ignition delay compared to ULSD, caused extended duration in Low Temperature Heat Release (LTHR) and cool flame formation. It was found in an analysis of the Apparent Heat Release Rate (AHRR) curve for IPK that there were multiple Negative Temperature Coefficient (NTCR) regions before the main combustion event. The High Temperature Heat Release (HTHR) of IPK achieved a greater peak heat release rate compared to ULSD. Pressure rise rate for IPK was observed to increase significantly with increase in injection timing. The peak in-cylinder pressure was also greater for IPK when matching CA50 by varying injection timing. Emissions analysis revealed that IPK produced less NOx, soot, and CO2 compared to ULSD. CO and UHC emissions for IPK increased. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email