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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.

Particulate emissions from gasoline direct injection (GDI) engines continue to be a topic of substantial research interest. Forthcoming regulation both in the USA and the EU will further reduce their emission and drive innovation. Substantial research effort is spent undertaking experiments to understand, characterize, and research particle number (PN) emissions from engines and vehicles. Recent advances in computing power, data storage, and understanding of artificial intelligence algorithms now mean that these are becoming an important tool in engine research. In this work a random forest (RF) algorithm is used for the prediction of PN emissions from a highly boosted (up to 32 bar BMEP) GDI engine. Particle size, concentration, and the accumulation mode geometric standard deviation (GSD) are all predicted by the model. The results are analysed and an in depth study on parameter importance is carried out.

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.

This study looked into the application of active thermal coatings on the surfaces of the combustion chamber as a method of improving the thermal efficiency of internal combustion engines. The active thermal coating was applied to a production aluminium piston and its performance was compared against a reference aluminium piston on a single-cylinder diesel engine. The two pistons were tested over a wide range of speed/load conditions and the effects of EGR and combustion phasing on engine performance and tailpipe emissions were also investigated. A detailed energy balance approach was employed to study the thermal behaviour of the active thermal coating. In general, improvements in indicated specific fuel consumption were not statistically significant for the coated piston over the whole test matrix. Mean exhaust temperature showed a marginal increase with the coated piston of up to 6 °C.

Knowledge of fuel mass injected in an individual cycle is important for engine performance and modeling. At the moment, such measurements are not possible on engine or in real time. In this article, a new method using Coriolis flow meters (CFMs) and a new, patented, signal processing technique, known as the Prism, are introduced. CFMs are extensively used for flow measurement both in the automotive industry and further afield and, when coupled with the Prism, have the potential to make these challenging high-speed measurements. A rig-based feasibility study was conducted injecting very small quantities of diesel (3 mg) at pressures of up to 1000 bar at simulated engine speeds of up to 4000 rpm. The results show that these small quantities can in principle be measured. The results also reveal a previously unknown behavior of CFMs when measuring very low flow rates at high speed.

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.

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.

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.

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.

Tax concessions promote the use of Liquefied Petroleum Gas (LPG) fuel for automotive use in Europe. Modelling of the LPG evaporation process shows the importance of drawing the liquid from the tank rather than the gas, otherwise the most volatile component (propane) is used more quickly and the composition of the remaining fuel changes. It is shown that the LPG components have similar calorific values to gasoline, however injecting the LPG as a gas into the inlet port causes a loss of volumetric efficiency and peak power. The experimental results showed: The LPG fuels have similar burn rates and optimum ignition timing to gasoline. The Lean Mixture Limit (LML) of the gaseous fuels was weaker than that for gasoline.

A study has been undertaken with a single-cylinder engine, based on the Mitsubishi GDi combustion system, that has the option of either port injection or direct injection. Tests have been undertaken with pure fuel components (methane, iso-octane, toluene and methanol), and a representative gasoline that has also been tested with the addition of 10% methanol and 10% ethanol. The volumetric efficiency depends both on the fuel and its time and place of injection. For stoichiometric operation with unleaded gasoline, changing from port injection to direct injection led to a 9% increase in volumetric efficiency, which was improved by a further 3% when 10% methanol was blended with the gasoline. The improvements in volumetric efficiency will be used to quantify the extent of charge cooling by fuel evaporation, and these will be compared with predictions assuming the maximum possible level of fuel evaporation.

Model M15 gasoline fuels have been created from pure fuel components, to give independent control of volatility, the heavy end content and the aromatic content, in order to understand the effect of the fuel properties on Gasoline Direct Injection (GDI) fuel spray behaviour and the subsequent particulate number emissions. Each fuel was imaged at a range of fuel temperatures in a spray rig and in a motored optical engine, to cover the full range from non-flashing sprays through to flare flashing sprays. The spray axial penetration (and potential piston and liner impingement), and spray evaporation rate were extracted from the images. Firing engine tests with the fuels with the same fuel temperatures were performed and exhaust particulate number spectra captured using a DMS500 Mark II Particle Spectrometer.

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.

To optimize internal combustion engines (ICEs), a good understanding of engine operation is essential. The heat transfer from the working gases to the combustion chamber walls plays an important role, not only for the performance, but also for the emissions of the engine. Besides, thermal management of ICEs is becoming more and more important as an additional tool for optimizing efficiency and emission aftertreatment. In contrast little is known about the convective heat transfer inside the combustion chamber due to the complexity of the working processes. Heat transfer measurements inside the combustion chamber pose a challenge in instrumentation due to the harsh environment. Additionally, the heat loss in a spark ignition (SI) engine shows a high temporal and spatial variation. This poses certain requirements on the heat flux sensor. In this paper we examine the heat transfer in a production SI ICE through the use of Thin Film Gauge (TFG) heat flux sensors.

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.

Modern diesel cars, fitted with state-of-the-art aftertreatment systems, have the capability to emit extremely low levels of pollutant species at the tailpipe. However, diesel aftertreatment systems can represent a significant cost, packaging and maintenance requirement. Reducing engine-out emissions in order to reduce the scale of the aftertreatment system is therefore a high priority research topic. Engine-out emissions from diesel engines are, to a significant degree, dependent on the detail of fuel/air interactions that occur in-cylinder, both during the injection and combustion events and also due to the induced air motion in and around the bowl prior to injection. In this paper the effect of two different piston bowl shapes are investigated.

In light of forthcoming particle number legislation for light-duty passenger vehicles, time-resolved Particle Mass (PM) and Particle Number (PN) emissions over the New European Drive Cycle (NEDC) are reported for four current vehicle technologies; modern diesel, with and without a Diesel Particulate Filter (DPF), Direct Injection Spark Ignition (DISI) gasoline and multi-point Port Fuel Injection (PFI) gasoline. The PN and PM emissions were ordered (highest to lowest) according to: Non-DPF diesel ≻ DISI ≻ PFI ~ DPF diesel. Both the non-DPF diesel and DISI vehicles emitted PN and PM continuously over the NEDC. This is in contrast with both the DPF diesel and PFI vehicles which emitted nearly all their PN and PM during the first 200 seconds. The PFI result is thought to be a consequence of cold-start mixture preparation whilst several possible explanations are offered for the DPF diesel trend.

A Cambustion Differential Mobility Spectrometer (DMS500), Dekati Electrical Low Pressure Impactor (ELPI), TSI Condensation Particle Counter (CPC) and AVL Photo-Acoustic Soot Sensor (PASS) were compared for measurements of emitted Particulate Matter (PM) from a Direct Injection Spark Ignition (DISI) vehicle on the New European Drive Cycle (NEDC) and at steady speed operating points. The exhaust was diluted in a Constant Volume Sampler (CVS) before being measured. Transient size spectral data from the DMS500 and ELPI is presented. PM Number rate and total PM number emissions are presented for the DMS500, ELPI and CPC. The DMS500 and ELPI data are post-processed for PM mass, and presented with data from the PASS. The instrument responses were correlated against each other. Qualitative agreement was generally found between all instruments. The agreement was closer for PM mass measurements than for measurements of PM number.

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.

The first part of the paper is a brief review of the techniques needed for measuring the voltage and current during the ignition process. These techniques have been used in test rigs and an engine to gain insights into the breakdown and subsequent discharge development. New correlations are presented for breakdown voltage as functions of spark plug gap, gas composition, temperature and pressure. The discharge voltage is affected by the flow, so an elevated pressure flow rig was used to look at the effect of flow and pressure on the discharge voltage history, with different stored energies in the ignition coil. This study led to a model for the discharge voltage history, from which it was possible to deduce the flow velocity through the spark plug gap. Finally, these techniques were applied to a single cylinder, 4-valve, pent-roof combustion chamber SI engine, for determining the cycle-by-cycle variations in velocity through the spark plug at the time of ignition.