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Technical Paper

Cycle-to-Cycle Variation Analysis of Two-Colour PLIF Temperature Measurements Calibrated with Laser Induced Grating Spectroscopy in a Firing GDI Engine

2019-04-02
2019-01-0722
In-cylinder temperatures and their cyclic variations strongly influence many aspects of internal combustion engine operation, from chemical reaction rates determining the production of NOx and particulate matter to the tendency for auto-ignition leading to knock in spark ignition engines. Spatially resolved measurements of temperature can provide insights into such processes and enable validation of Computational Fluid Dynamics simulations used to model engine performance and guide engine design. This work uses a combination of Two-Colour Planar Laser Induced Fluorescence (TC-PLIF) and Laser Induced Grating Spectroscopy (LIGS) to measure the in-cylinder temperature distributions of a firing optically accessible spark ignition engine. TC-PLIF performs 2-D temperature measurements using fluorescence emission in two different wavelength bands but requires calibration under conditions of known temperature, pressure and composition.
Technical Paper

Novel Metrics for Validation of PIV and CFD in IC Engines

2019-04-02
2019-01-0716
In-cylinder flow motion has a significant effect on mixture preparation and combustion. Therefore, it is vital that CFD engine simulations are capable of accurately predicting the in-cylinder velocity fields. High-speed planar Particle Image Velocimetry (PIV) experiments have been performed on a single-cylinder GDI optical engine in order to validate CFD simulations for a range of engine conditions. Novel metrics have been developed to quantify the differences between experimental and simulated velocity fields in both alignment and magnitude. The Weighted Relevance Index (WRI) is a variation of the standard Relevance Index that accounts for the local velocity magnitudes to provide a robust comparison of the alignment between two vector fields. Similarly, the Weighted Magnitude Index (WMI) quantifies the differences in the local magnitudes of the two velocity fields.
Journal Article

In-Cylinder Temperature Measurements Using Laser Induced Grating Spectroscopy and Two-Colour PLIF

2017-09-04
2017-24-0045
In-cylinder temperature measurements are vital for the validation of gasoline engine modelling and useful in their own right for explaining differences in engine performance. The underlying chemical reactions in combustion are highly sensitive to temperature and affect emissions of both NOx and particulate matter. The two techniques described here are complementary, and can be used for insights into the quality of mixture preparation by measurement of the in-cylinder temperature distribution during the compression stroke. The influence of fuel composition on in-cylinder mixture temperatures can also be resolved. Laser Induced Grating Spectroscopy (LIGS) provides point temperature measurements with a pressure dependent precision in the range 0.1 to 1.0 % when the gas composition is well characterized and homogeneous; as the pressure increases the precision improves.
Technical Paper

Optical Techniques that can be Applied to Investigate GDI Engine Combustion

2017-09-04
2017-24-0046
The increased efficiency and specific output with Gasoline Direct Injection (GDI) engines are well known, but so too are the higher levels of Particulate Matter emissions compared with Port Fuel Injection (PFI) engines. To minimise Particulate Matter emissions, then it is necessary to understand and control the mixture preparation process, and important insights into GDI engine mixture preparation and combustion can be obtained from optical access engines. Such data is also crucial for validating models that predict flows, sprays and air fuel ratio distributions. The purpose of this paper is to review a number of optical techniques; the interpretation of the results is engine specific so will not be covered here. Mie scattering can be used for semi-quantitative measurements of the fuel spray and this can be followed with Planar Laser Induced Fluorescence (PLIF) for determining the air fuel ratio and temperature distributions.
Technical Paper

Reduction of CO2 Emissions through Lubricant Thermal Management During the Warm Up of Passenger Car Engines

2016-04-05
2016-01-0892
Most major regional automotive markets have stringent legislative targets for vehicle greenhouse gas emissions or fuel economy enforced by fiscal penalties. Large improvements in vehicle efficiency on mandated test cycles have already taken place in some markets through the widespread adoption of technologies such as downsizing or dieselisation. There is now increased focus on approaches which give smaller, but significant incremental efficiency benefits, such as reducing parasitic losses due to engine friction. The reduction in tail pipe CO2 emissions through the reduction of engine friction using lubricants has been reported by many authors. However, opportunities also exist to reduce the lubricant viscosity during warm up by the thermal management of the lubricant mass.
Technical Paper

The Effect of Combustion Knock on the Instantaneous Heat Flux in Spark Ignition Engines

2016-04-05
2016-01-0700
Knocking combustion places a major limit on the performance and efficiency of spark ignition engines. Spontaneous ignition of the unburned air-fuel mixture ahead of the flame front leads to a rapid release of energy, which produces pressure waves that cause the engine structure to vibrate at its natural frequencies and produce an audible ‘pinging’ sound. In extreme cases of knock, increased temperatures and pressures in the cylinder can cause severe engine damage. Damage is thought to be caused by thermal strain effects that are directly related to the heat flux. Since it will be the maximum values that are potentially the most damaging, then the heat flux needs to be measured on a cycle-by-cycle basis. Previous work has correlated heat flux with the pressure fluctuations on an average basis, but the work here shows a correlation on a cycle-by-cycle basis. The in-cylinder pressure and surface temperature were measured using a pressure transducer and eroding-type thermocouple.
Technical Paper

Tribological Behavior of Low Viscosity Lubricants in the Piston to Bore Zone of a Modern Spark Ignition Engine

2014-10-13
2014-01-2859
Most major regional automotive markets have stringent legislative targets for vehicle greenhouse gas emissions or fuel economy enforced by fiscal penalties. Large improvements in vehicle efficiency on mandated test cycles have already taken place in some markets through the widespread adoption of technologies such as downsizing or dieselization. There is now increased focus on approaches which give smaller but significant incremental efficiency benefits such as reducing parasitic losses due to engine friction. Fuel economy improvements which achieve this through the development of advanced engine lubricants are very attractive to vehicle manufacturers due to their favorable cost-benefit ratio. For an engine with components which operate predominantly in the hydrodynamic lubrication regime, the most significant lubricant parameter which can be changed to improve the tribological performance of the system is the lubricant viscosity.
Book

Introduction to Internal Combustion Engines, Fourth Edition

2012-09-30
Now in its fourth edition, this book remains the indispensable guide to internal combustion engines. It serves as valuable reference for both students and professional engineers needing a practical overview of the subject. Thoroughly updated, clear, comprehensive and well-illustrated, with a wealth of worked examples and problems, its combination of theory and applied practice is sure to help you understand internal combustion engines, from thermodynamics and combustion to fluid mechanics and materials science. Co-published by SAE International and Macmillan Press. Topics include: • Thermodynamic Principles • Combustion and Fuels • Spark Ignition Engines • Induction and Exhaust Processes • Turbocharging • Experimental Facilities
Journal Article

Investigation of Combustion Robustness in Catalyst Heating Operation on a Spray Guided DISI Engine, Part II - Measurements of Spray Development, Combustion Imaging and Emissions

2010-04-12
2010-01-0603
In-cylinder spray imaging by Mie scattering has been taken with frame rates up to 27,000 fps, along with high speed video photography of chemiluminescence and soot thermal radiation. Spectroscopic measurements have confirmed the presence of OH*, CH* and C2* emissions lines, and their magnitude relative compared to soot radiation. Filtering for CH* has been used with both the high speed video and a Photo-Multiplier Tube (PMT). The PMT signals have been found to correlate with the rate of heat release derived from in-cylinder pressure measurements. A high power photographic strobe has been used to illuminate the fuel spray. Images show that the fuel spray can strike the ground strap of the spark plug, break up, and a fuel cloud then drifts over and under the strap through the spark plug gap. Tests have conducted at two different spark plug orientations using a single spark strategy.
Technical Paper

Investigation of Combustion Robustness in Catalyst Heating Operation on a Spray Guided DISI Engine, Part 1 - Measurements of Spark Parameters and Combustion

2010-04-12
2010-01-0593
In the catalyst heating operation for a spray guided DISI (Direct Injection Spark Ignition) engine, split injection has been shown to improve combustion stability which is critical for the trade-off between tailpipe emissions and vehicle idle NVH [ 1 ]. The spray guided DISI engine has a multi-hole injector centrally located in the chamber with the spark plug. For catalyst heating operation, the first injection occurs during induction, which forms a relatively well mixed but lean mixture in the cylinder before ignition, and the second injection occurs close to a retarded ignition, which produces a stratified fuel rich mixture in the central region of the combustion chamber. Combustion initialization is found to be sensitive to spark plug protrusion and orientation, injector orientation and 2 nd injection timing relative to ignition [ 1 ].
Technical Paper

Analysis of Combustion and Particulate Emissions when Hydrogen is Aspirated into a Gasoline Direct Injection Engine

2010-04-12
2010-01-0580
A single-cylinder Gasoline Direct Injection Engine (GDI) engine with a centrally mounted spray-guided injection system (150 bar fuel pressure) has been operated with stoichiometric and rich mixtures. The base fuel was 65% iso-octane and 35% toluene; hydrogen was aspirated into a plenum in the induction system, and its equivalence ratios were set to 0, 0.02, 0.05 and 0.1. Ignition timing sweeps were conducted for each operating point. Combustion was speeded up by adding hydrogen as expected. In consequence the MBT ignition advance was reduced, as were cycle-by-cycle variations in combustion. Adding hydrogen led to the expected reduction in IMEP as the engine was operated at a fixed manifold absolute pressure (MAP). An engine model has also been set up using WAVE. Particulate Matter (PM) emissions were measured with a Cambustion DMS500 particle sizer.
Technical Paper

The Influence of Ethanol Blends on Particulate Matter Emissions from Gasoline Direct Injection Engines

2010-04-12
2010-01-0793
Particulate Matter (PM) legislation for gasoline engines and the introduction of gasoline/ethanol blends, make it important to know the effect of fuel composition on PM emissions. Tests have been conducted with fuels of known composition in both a single-cylinder engine and V8 engine with a three-way catalyst. The V8 engine used an unleaded gasoline (PURA) with known composition and distillation characteristics as a base fuel and with 10% by volume ethanol. The single-cylinder engine used a 65% iso-octane - 35% toluene mixture as its base fuel. The engines had essentially the same combustion system, with a centrally mounted 6-hole spray-guided direct injection system. Particle size distributions were recorded and these have also been converted to mass distributions. Filter samples were taken for thermo-gravimetric analysis (TGA) to give composition information. Both engines were operated at 1500 rpm under part load.
Technical Paper

Multi-Component Quantitative PLIF: Robust Engineering Measurements of Cyclic Variation in a Firing Spray-Guided Gasoline Direct Injection Engine

2008-04-14
2008-01-1073
Planar Laser-Induced Fluorescence has been widely accepted and applied to measurements of fuel concentration distributions in IC engines. The need for such measurements has increased with the introduction of Direct Injection (DI) gasoline engines, where it is critical to understand the influence of mixture inhomogeneity on ignition and subsequent combustion, and in particular the implications for cyclic variability. The apparent simplicity of PLIF has led to misunderstanding of the technique when applied to quantitative measurements of fuel distributions. This paper presents a series of engineering methods for optimizing, calibrating and referencing, which together demonstrate a quantitative measure of fuel concentration with an absolute accuracy of 10%. PLIF is widely used with single component fuels as carriers for the fluorescent tracers.
Technical Paper

Burn Rate and Instantaneous Heat Flux Study of Iso-octane, Toluene and Gasoline in a Spray-Guided Direct-Injection Spark-Ignition Engine

2008-04-14
2008-01-0469
The burn rate and the instantaneous in-cylinder heat transfer have been studied experimentally in a spray-guided direct-injection spark-ignition engine with three different fuels: gasoline, iso-octane and toluene. The effects of the ignition timing, air fuel ratio, fuel injection timing and injection strategy (direct injection or port injection) on the burn rate and the in-cylinder heat transfer have been experimentally investigated at a standard mapping point (1500 rpm and 0.521 bar MAP) with the three different fuels. The burn rate analysis was deduced from the in-cylinder pressure measurement. A two-dimensional heat conduction model of the thermocouple was used to calculate the heat flux from the measured surface temperature. An engine thermodynamic simulation code was used to predict the gas-to-wall heat transfer.
Technical Paper

Cold Start Particulate Emissions from a Second Generation DI Gasoline Engine

2007-07-23
2007-01-1931
Spray guided Direct Injection Gasoline Engines are a key enabler to reducing CO2 emissions and improving the fuel economy of light duty vehicles. Particulate emissions from these engines have been shown to be lower than from first generation direct injection gasoline engines, but they may still be significantly higher than port fuel injected engines due to the reduced time available for mixture preparation and increased incidence of fuel impingement on the piston crown and combustion chamber surfaces. These factors are particularly severe in the period following a cold start. Both nuclei and accumulation mode particle size and number concentration were measured using a Cambustion differential mobility spectrometer. These data are reported for different coolant temperature intervals during the warm-up period. The bulk composition was determined using thermo-gravimetric analysis, and PM mass fractions are given for different volatility ranges and for elemental carbon.
Technical Paper

Particulate Emissions from a Gasoline Homogeneous Charge Compression Ignition Engine

2007-04-16
2007-01-0209
Particulate Emissions from Homogeneous Charge Compression Ignition (HCCI) combustion are routinely assumed to be negligible. It is shown here that this is not the case when HCCI combustion is implemented in a direct injection gasoline engine. The conditions needed to sustain HCCI operation were realized using the negative valve overlap method for trapping high levels of residual exhaust gases in the cylinder. Measurements of emitted particle number concentration and electrical mobility diameter were made with a Cambustion DMS500 over the HCCI operating range possible with this hardware. Emissions of oxides of nitrogen, carbon monoxide and unburned hydrocarbons were also measured. These data are presented and compared with similar measurements made under conventional spark ignition (SI) operation in the same engine. Under both SI and HCCI operation, a significant accumulation mode was detected with particle equivalent diameters between 80 and 100 nm.
Technical Paper

Particulate and Hydrocarbon Emissions from a Spray Guided Direct Injection Spark Ignition Engine with Oxygenate Fuel Blends

2007-04-16
2007-01-0472
The blending of oxygenated compounds with gasoline is projected to increase because oxygenate fuels can be produced renewably, and because their high octane rating allows them to be used in substitution of the aromatic fraction in gasoline. Blending oxygenates with gasoline changes the fuels' properties and can have a profound affect on the distillation curve, both of which are known to affect engine-out emissions. In this work, the effect of blending methanol and ethanol with gasoline on unburned hydrocarbon and particulate emissions is experimentally determined in a spray guided direct injection engine. Particulate number concentration and size distribution were measured using a Cambustion DMS500. These data are presented for different air fuel ratios, loads, ignition timings and injection timings. In addition, the ASTM D86 distillation curve was modeled using the binary activity coefficients method for the fuel blends used in the experiments.
Technical Paper

Particulate Matter and Hydrocarbon Emissions Measurements: Comparing First and Second Generation DISI with PFI in Single Cylinder Optical Engines

2006-04-03
2006-01-1263
A Spray Guided Direct Injection (SGDI) engine has been shown to emit less Particulate Matter (PM) than a first generation (wall guided) Direct Injection Spark Ignition (DISI) engine. The reduction is attributed to the reduced incidence of fuel-wall impingement and higher fuel injection pressure. The extent to which this is true was investigated by comparison between single cylinder SGDI and DISI engines. Both engines were also operated with conventional port injection to provide a baseline. Feedgas PM number concentration and size spectra were measured using a Cambustion differential mobility spectrometer for the fuels iso-octane and toluene with a range of Air-Fuel Ratios (AFRs), ignition and injection timings.
Technical Paper

In-Cylinder Temperature Estimation from an Optical Spray-Guided DISI Engine with Color-Ratio Pyrometry (CRP)

2006-04-03
2006-01-1198
Color-ratio pyrometry (CRP) is a technique for estimating the temperature and loading of soot, based on its thermal emission spectrum. This technique is contrasted with conventional two-color pyrometry which requires absolute measurements of the radiation intensity, either at two specific wavelengths or ranges of wavelengths. CRP uses two ratios, obtained by measuring the radiation intensity for three wavelengths or wavelength bands. CRP has been implemented here by using a digital CCD camera, and full details of the calibration are reported. Because of uncertainties in the emissivity of reference sources (such as tungsten ribbon lamps, in which the emissivity depends on temperature and wavelength), then a spectroscopic calibration of the CCD camera has been used. Use of a CCD camera is not straightforward because of internal digital signal processing (DSP), so full details are given of the calibration and technique implementation.
Technical Paper

Cycle-by-Cycle Variations in Exhaust Temperatures Using Thermocouple Compensation Techniques

2006-04-03
2006-01-1197
Exhaust gas temperatures in a 1.4 L, sparked ignition engine have been measured using fine wire thermocouples at different loads and speeds. However the thermocouples are not fast enough to resolve the rapid change in exhaust temperature. This paper discusses a new thermocouple compensation technique to resolve the cycle-by-cycle variations in exhaust temperature by segmentation. Simulation results show that the technique can find the lower time constants during blowdown, reducing the bias from 28 to 4%. Several estimators and model structures have been compared. The best one is the difference equation-least squares technique, which has the combined error between -4.4 to 7.6% at 60 dB signal-to-noise ratio. The compensated temperatures have been compared against combustion parameters on a cycle-by-cycle basis. The results show that the cycle-by-cycle variations of the exhaust temperatures and combustion are correlated.
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