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Technical Paper

Autoignition and Combustion of ULSD and JP8 during Cold Starting of a High Speed Diesel Engine

2017-03-28
2017-01-0797
Cold starting problems of diesel engines are caused mainly by the failure of the auto-ignition process or the subsequent combustion of the rest of the charge. The problems include long cranking periods and combustion instability leading to an increase in fuel consumption in addition to the emission of undesirable unburned hydrocarbons which appear in the exhaust as white smoke. The major cause of these problems is the low temperature and pressure of the charge near the end of the compression stroke and/or the poor ignition quality of the fuel. This paper presents the results of an experimental investigation of cold starting of a high speed diesel engine with ULSD (Ultra Low Sulphur Diesel) and JP8 (Jet Propulsion) fuels at ambient temperature (25°C). A detailed analysis is made of the autoignition and combustion of the two fuels in the first few cycles in the cold start transient. In addition, a comparison is made between these processes for the two fuels during idle operation.
Technical Paper

Direct Injection Compression Ignition Engine: Cold Start on Gasoline and Diesel

2017-03-28
2017-01-0699
The superior fuel economy of direct injection internal combustion engines (diesel and gasoline) is related to use of a high compression ratio to auto-ignite the fuel and the overall lean combustible mixture. Two of the major problems in diesel engine emissions are the NOx and soot emissions, which are caused by the heterogeneity of the charge and the properties of the diesel fuel. Conventional Direct Injection Spark Ignition Gasoline engines don't have these problems because of the fuel properties particularly its volatility. However, its efficiency and specific power output are limited by the knock, knock produced preignition and the sporadic preignition phenomenon. The Gasoline Direct Injection Compression Ignition (GDICI) engine combines the superior features of the two engines by increasing the compression ratio and use of gasoline as a fuel.
Journal Article

Development of JP-8 Surrogates and their Validation using Ignition Quality Tester

2014-04-15
2014-01-9077
This paper presents a new approach for the development of six different JP-8 surrogates for application in diesel cycle simulation. The approach involves a step-wise formulation of 2-, 3-, and 4-component surrogates from a list of pure compounds which are selected based on several criteria. A MATLAB code is developed and is used in conjunction with the Ignition Quality Tester (IQT) and HYSYS software in order to formulate optimal surrogates. The first part of the results shows a comparison between the calculated and the measured DCNs for six surrogates. The differences in the properties such as the density, volatility, lower heating value, H/C ratio, molecular weight, and threshold sooting index of the surrogates and the JP-8 are also highlighted. This is followed by the evaluation of the surrogates with respect to the target JP-8 fuel. The evaluation is made in terms of ignition delays and the rate of heat release at three different IQT test temperatures.
Journal Article

Experimental Validation and Combustion Modeling of a JP-8 Surrogate in a Single Cylinder Diesel Engine

2014-04-01
2014-01-1376
This paper presents the results of an experimental investigation on a single cylinder engine to validate a two-component JP-8 surrogate. The two-component surrogate was chosen based on a previous investigation where the key properties, such as DCN, volatility, density, and lower heating value, of the surrogate were matched with those of the target JP-8. The matching of the auto-ignition, combustion, and emission characteristics of the surrogate with JP-8 was investigated in an actual diesel engine environment. The engine tests for the validation of the surrogate were conducted at an engine speed of 1500 rpm, a load of 3 bar, and different injection timings. The results for the cylinder gas pressure, ignition delay period, rate of heat release, and the CO, HC, and NOx emissions showed a good match between the surrogate and the target JP-8. However, the engine-out particulate matter for the surrogate was lower than that for the JP-8 at all tested conditions.
Journal Article

Role of Volatility in the Development of JP-8 Surrogates for Diesel Engine Application

2014-04-01
2014-01-1389
Surrogates for JP-8 have been developed in the high temperature gas phase environment of gas turbines. In diesel engines, the fuel is introduced in the liquid phase where volatility plays a major role in the formation of the combustible mixture and autoignition reactions that occur at relatively lower temperatures. In this paper, the role of volatility on the combustion of JP-8 and five different surrogate fuels was investigated in the constant volume combustion chamber of the Ignition Quality Tester (IQT). IQT is used to determine the derived cetane number (DCN) of diesel engine fuels according to ASTM D6890. The surrogate fuels were formulated such that their DCNs matched that of JP-8, but with different volatilities. Tests were conducted to investigate the effect of volatility on the autoignition and combustion characteristics of the surrogates using a detailed analysis of the rate of heat release immediately after the start of injection.
Technical Paper

Experimental Study for the Effect of Fuel Properties on the Ion Current, Combustion, and Emission in a High Speed Diesel Engine

2014-04-01
2014-01-1263
This paper presents experimental study on the impact of using fuels with different physical and chemical properties in a diesel engine. Research is driven towards finding an alternative or extender to the conventional diesel fuel for compression ignition engines. Such alternative fuels have wide ranges of physical and chemical properties which are not suitable for CI engines. Advanced injection systems and control strategies in modern diesel engines permit operation to be extended to a wider range of fuels. Therefore, experimental investigation to understand the effects of different fuels on engine performance, combustion, and emissions are necessary. The study covers the effect of using different fuels such as JP-8 and Sasol-IPK on a modern automotive diesel engine. The engine used in this study is a 2.0L, 4 cylinders, direct injection diesel engine fitted with piezo-driven injectors.
Technical Paper

Combustion Ionization for Resonance Detection and Mitigation Using Pilot Injection in a Diesel Engine

2014-04-01
2014-01-1360
Advanced injection systems play a major role in reducing engine out emission in modern diesel engines. One interesting technology is the common rail injection system which is becoming more vital in controlling emission due to its flexibility in injection pressure, timing and number of injection events. Many studies have showed the advantages of using such injection parameters to meet the strict emission and improve engine performance. A glow plug/ ion current sensor was used to measure ionization produced during the combustion process. The ion current signal contains many valuable information including combustion phasing, duration and combustion resonance. In prior publications, it was demonstrated the capability of the ion current to control the combustion phasing and the ability to detect combustion resonance. Therefore, the experimental testing was conducted under controlled combustion phasing using the feedback from the ion current sensor.
Technical Paper

Cycle Resolved In-Cylinder NOx and Ion Current Measurements in a Diesel Engine

2013-04-08
2013-01-0555
This paper investigates the relationship between NOx and ion current measured inside the combustion chamber of a heavy duty diesel engine under different operating conditions. Nevertheless, ion current is a local signal, thus it is important to measure NOx concentrations at the same exact location of the ion current probe. A novel technique is developed to simultaneously sample in-cylinder NOx and measure the ion current signal by adapting gas sampling probes for ion sensing. The cycle-resolved traces for the rate of heat release, NO mole fraction and ion current were analyzed to determine the contribution of the premixed combustion and the mixing-diffusion controlled combustion on NO formation and ionization in diesel engines.
Technical Paper

Cycle-by-Cycle Soot Estimation in Diesel Engines

2013-04-08
2013-01-0545
Estimation of soot in real time would help in the development of engine controls during engine production to meet the emissions goals and for on-board diagnostics. This paper presents a new approach to the estimate the soot emissions from the ion current measured inside the cylinder during engine operation. The investigation was carried out on a 4.5L heavy duty, turbocharged diesel engine. The glow plug was modified to act as an ion current probe, in addition to its main function. Algorithms were developed for the ion current signal to estimate the soot formed on a cycle-by-cycle basis. A comparison was made between the estimated soot emissions and measurements made by using an opacity meter under steady state as well as under transient engine operating conditions. In this research, a non-linear multiple regression model (NLMR) was used to estimate soot percentage from the ion current signal.
Journal Article

Ethanol/N-Heptane Dual-Fuel Partially Premixed Combustion Analysis through Formaldehyde PLIF

2012-04-16
2012-01-0685
As a result of recent focus on the control of Low Temperature Combustion (LTC) modes, dual-fuel combustion strategies such as Reactivity Controlled Compression Ignition (RCCI) have been developed. Reactivity stratification of the auto-igniting mixture is thought to be responsible for the increase in allowable engine load compared to other LTC combustion modes such as Homogenous Charge Compression Ignition (HCCI). The current study investigates the effect of ethanol intake fuel injection on in-cylinder formaldehyde formation and stratification within an optically accessible engine operated with n-heptane direct injection using optical measurements and zero-dimensional chemical kinetic models. Images obtained by Planar Laser Induced Fluorescence (PLIF) of formaldehyde using the third harmonic of a pulsed Nd:YAG laser indicate an increase in formaldehyde heterogeneity as measured by the fluorescence signal standard deviation.
Technical Paper

Closed Loop Control Using Ion Current Signal in a Diesel Engine

2012-04-01
2011-01-2433
Signals indicative of in-cylinder combustion have been under investigation for the control of diesel engines to meet stringent emission standards and other production targets in performance and fuel economy. This paper presents the results of an investigation on the use of the ion current signal for the close loop control of a heavy duty four cylinder turbocharged diesel engine equipped with a common rail injection system. A correlation is developed between the start of ion current signal (SIC) and the location of the peak of premixed combustion (LPPC) in the rate of heat release trace. Based on this correlation, a PID closed loop controller is developed to adjust the injection timing for proper combustion phasing under steady and transient engine operating conditions.
Technical Paper

Effect of Using Biodiesel (B-20) and Combustion Phasing on Combustion and Emissions in a HSDI Diesel Engine

2011-04-12
2011-01-1203
The use of biodiesel and its blends with ultra low sulfur diesel (ULSD) is gaining significant importance due to its ability to burn in conventional diesel engines with minor modifications. However the chemical and physical properties of biodiesel are different compared to the conventional ULSD. These differences directly impact the injection, spray formation, auto ignition and combustion processes which in turn affect the engine-out emissions. To understand the effect of fueling with B-20, tests were conducted on a single cylinder 0.42L direct injection research diesel engine. The engine is equipped with a common rail injection system, variable EGR and swirl control systems and was operated at a constant engine speed of 1500 rpm and 3 bar IMEP to simulated turbocharged conditions. Injection timing and duration were adjusted with B-20 at different locations of peak premixed combustions (LPPC) and two different swirl ratios to achieve 3 bar IMEP.
Technical Paper

Simulation of the Effect of Recirculated Gases on Ignition Delay During Cold Starting of a Direct Injection Diesel Engine

2011-04-12
2011-01-0838
Simulations using CFD and chemical kinetics models have been applied to gain a better understanding of the effect of the recirculated gases on the autoignition process during cold starting of a direct injection diesel engine. The cranking gases recirculated (CGR) contain fuel vapor and partial oxidation products which affect the autoignition process in different ways. Some hydrocarbons (HCs) species enhance the reaction rates and reduce ignition delay. Meanwhile other HCs species and the partial oxidation products of the autoignition process have an opposing effect. The simulation covered a wide range of the hydrocarbons and aldehydes concentrations and their effect on the ignition delay in a 1.2L Ford DIATA 4-cylinders, water cooled, turbocharged and intercooled diesel engine. The simulated opposing effects of HCs and HCHO on the ignition delay are validated by experimental results at room temperature.
Technical Paper

Multi Sensing Fuel Injector for Electronically Controlled Diesel Engines

2011-04-12
2011-01-0936
Internal combustion engine control requires feedback signals to the ECU in order to meet the increasingly stringent emissions standards. Reducing the number of on-board sensors needed for proper engine performance would reduce the cost and complexity of the electronic system. This paper presents a new technique to enable one engine element, the fuel injector, to perform multiple sensing tasks in addition to its primary task of delivering the fuel into the cylinder. The injector is instrumented within an electric circuit to produce a signal indicative of the ionization produced from the combustion process in electronically controlled diesel engines. The output of the multi sensing fuel injector (MSFI) system can be used as a feedback signal to the engine control unit (ECU) for injection timing and diagnostics of the injection and combustion processes.
Technical Paper

Comparison between Combustion, Performance and Emission Characteristics of JP-8 and Ultra Low Sulfur Diesel Fuel in a Single Cylinder Diesel Engine

2010-04-12
2010-01-1123
JP-8 is an aviation turbine engine fuel recently introduced for use in military ground vehicle applications and generators which are mostly powered by diesel engines. Many of these engines are designed and developed for commercial use and need to be adapted for military applications. This requires more understanding of the auto- ignition and combustion characteristics of JP-8 under different engine operating conditions. This paper presents the results of a comparative analysis of an engine operation using JP-8 and ultra low sulfur diesel fuel (ULSD). Experiments were conducted on 0.42 liter single cylinder, high speed direct injection (HSDI) diesel engine equipped with a common rail injection system. The results indicate that the distillation properties of fuel have an effect on its vaporization rate. JP-8 evaporated faster and had shorter ignition delay as compared to ULSD. The fuel economy with JP-8 was better than ULSD.
Technical Paper

Effect of Biodiesel and its Blends on Particulate Emissions from HSDI Diesel Engine

2010-04-12
2010-01-0798
The effect of biodiesel on the Particulate emissions is gaining significant attention particularly with the drive for the use of alternative fuels. The particulate matter (PM), especially having a diameter less than 50 nm called the Nanoparticles or Nucleation mode particles (NMPs), has been raising concerns about its effect on human health. To better understand the effect of biodiesel and its blends on particulate emissions, steady state tests were conducted on a small-bore single-cylinder high-speed direct-injection research diesel engine. The engine was fueled with Ultra-Low Sulfur Diesel (ULSD or B-00), a blend of 20% soy-derived biodiesel and 80% ULSD on volumetric basis (B-20), B-40, B-60, B-80 and 100% soy-derived biodiesel (B-100), equipped with a common rail injection system, EGR and swirl control systems at a load of 5 bar IMEP and constant engine speed of 1500 rpm.
Journal Article

Effect of Swirl Ratio and Wall Temperature on Pre-lnjection Chemiluminescence During Starting of an Optical Diesel Engine

2009-11-02
2009-01-2712
Fuel wall impingement commonly occurs in small-bore diesel engines. Particularly during engine starting, when wall temperatures are low, the evaporation rate of fuel film remaining from previous cycles plays a significant role in the autoignition process that is not fully understood. Pre-injection chemiluminescence (PIC), resulting from low-temperature oxidation of evaporating fuel film and residual gases, was measured over 3200 μsec intervals at the end of the compression strokes, but prior to fuel injection during a series of starting sequences in an optical diesel engine. These experiments were conducted to determine the effect of this parameter on combustion phasing and were conducted at initial engine temperatures of 30, 40, 50 and 60°C, at swirl ratios of 2.0 and 4.5 at 1000 RPM. PIC was determined to increase and be highly correlated with combustion phasing during initial cycles of the starting sequence.
Technical Paper

Effect of Different Biodiesel Blends on Autoignition, Combustion, Performance and Engine-Out Emissions in a Single Cylinder HSDI Diesel Engine

2009-04-20
2009-01-0489
The effects of different blends of Soybean Methyl Ester (biodiesel) and ultra low sulfur diesel (ULSD) fuel: B-00 (ULSD), B-20, B-40, B-60, B-80 and B-100 (biodiesel); on autoignition, combustion, performance, and engine out emissions of different species including particulate matter (PM) in the exhaust, were investigated in a single-cylinder, high speed direct injection (HSDI) diesel engine equipped with a common rail injection system. The engine was operated at 1500 rpm under simulated turbocharged conditions at 5 bar IMEP load with varied injection pressures at a medium swirl of 3.77 w ithout EGR. Analysis of test results was done to determine the role of biodiesel percentage in the fuel blend on the basic thermodynamic and combustion processes under fuel injection pressures ranging from 600 bar to 1200 bar.
Technical Paper

Optical and Numerical Investigation of Pre-Injection Reactions and Their Effect on the Starting of a Diesel Engine

2009-04-20
2009-01-0648
Ultraviolet chemiluminescence has been observed in a diesel engine cyclinder during compression, but prior to fuel injection under engine starting conditions. During a portion of the warm-up sequence, the intensity of this emission exhibits a strong correlation to the phasing of the subsequent combustion. Engine exhaust measurements taken from a continuously misfiring, motored engine confirm the generation of formaldehyde (HCHO) in such processes. Fractions of this compound are expected to be recycled as residual to participate in the following combustion cycle. Spectral measurements taken during the compression period prior to fuel injection match the features of Emeleus' cool flame HCHO bands that have been observed during low temperature heat release reactions occurring in lean HCCI combustion. That the signal from the OH* bands is weak implies a buildup of HCHO during compression.
Technical Paper

Experimental Investigation of Single and Two-Stage Ignition in a Diesel Engine

2008-04-14
2008-01-1071
This paper presents an experimental investigation conducted to determine the parameters that control the behavior of autoignition in a small-bore, single-cylinder, optically-accessible diesel engine. Depending on operating conditions, three types of autoignition are observed: a single ignition, a two-stage process where a low temperature heat release (LTHR) or cool flame precedes the main premixed combustion, and a two-stage process where the LTHR or cool flame is separated from the main heat release by an apparent negative temperature coefficient (NTC) region. Experiments were conducted using commercial grade low-sulfur diesel fuel with a common-rail injection system. An intensified CCD camera was used for ultraviolet imaging and spectroscopy of chemiluminescent autoignition reactions under various operating conditions including fuel injection pressures, engine temperatures and equivalence ratios.
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