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The fuel injection process in the port of a firing 4-valve SI engine at part load and 25°C head temperature was observed by a high speed video camera. Fuel was injected when the valve was closed. The reverse blow-down flow when the intake valve opens has been identified as an important factor in the mixture preparation process because it not only alters the thermal environment of the intake port, but also strip-atomizes the liquid film at the vicinity of the intake valve and carries the droplets away from the engine. In a series of “fuel-on” experiments, the fuel injected in the current cycle was observed to influence the fuel delivery to the engine in the subsequent cycles.

The Vauxhall 14-40 was introduced in 1922 and is a good example of contemporary best practice. In its first 20 years Vauxhall had established a strong reputation for sporting performance, and the 14-40 was their first vehicle aimed at the middle classes. The 14-40 has extensive use of aluminum alloy castings, a unitary engine clutch and gear box with a torque tube coupling to the back axle, half elliptic front springs with a beam axle and cantilevered rear leaf springs. The engine was heavily influenced by Ricardo, so as to have low friction levels and a good combustion performance. The engine design will be reviewed in the context of the fuel available in the 1920s. This paper reviews the vehicle technology in the context of its contemporaries, and makes use of contemporary engine performance data for tuning a simple engine model, the results of which are to be used in a vehicle simulation.

The numerous variable valve actuation mechanisms for poppet valves need to be classified, if sensible comparisons are to be made, and one possible taxonomy is presented here. Not all the mechanisms proposed have been tested, but where they have it is usually with gasoline engines. It is well established that controlling the valve events can raise and flatten the torque curve. However, it is difficult to quantify and compare the gains in torque and consequential reduction in fuel consumption, as the results depend very much on the starting point. This is also the case when variable valve actuation is used to reduce engine emissions. Fortunately it is quite easy to realise suitable variable valve timing systems for controlling the valve overlap, and the point of inlet valve closure. The other main application to gasoline engines, is in obtaining load control without throttling.

This work examines the effects of valve timing and back pressure on the engine out enthalpy flow which is critical to the light off of the catalyst. The engine behavior is observed under fast-idle condition using a turbocharged production direct injection spark ignition engine with variable cam phasing that could shift both the intake and exhaust valve timing by 50 deg. crank angle. The back pressure is adjusted by throttling the exhaust. The engine operates at a constant net indicated mean effective pressure of 2 bar. The valve timing effect is largely governed by the residual gas trapped. With increasing valve overlap, the exhaust enthalpy flow increases because of the increase in exhaust temperature due to a slower combustion, and of the increase in air and fuel flow to compensate for the lower efficiency due to the slower combustion. When the back pressure is increased, the engine through flow has to increase to compensate for the larger pumping loss.

Ethanol and acetaldehyde emissions from a direct ignition spark ignition were measured using mass spectrometry. Previous methods focused on eliminating or minimizing interference from exhaust species with identical atomic mass and fragment ions created in ionization process. This paper describes a new technique which exploits the fragment ions from ethanol and acetaldehyde. A survey of mass spectra of all major species of exhaust gas was conducted. It was found that ethanol contributes most ions in mass number 31 and that no other gas species produces ions at this mass number. Acetaldehyde detection suffers more interference. Nevertheless, it was estimated that detection at mass number 43 is possible with 10% error from 2-methylbutane. This new technique was validated in an engine experiment. By running the engine with pure gasoline and E85, the validity of the technique can be checked.

The knock metric for controlled auto-ignition (CAI) engines is assessed by considering the physical processes that establish the pressure wave that contributes to the acoustic radiation of the engine, and by analyzing pressure data from a CAI engine. Data sets from the engine operating with port fuel injection, early direct injection and late direct injection are used to monitor the effect of mixture composition stratification. Thermodynamic analysis shows that the local pressure rise produced by heat release has to be discounted by the work spent in acoustic expansion against the ambient pressure to properly predict the pressure wave amplitude. Based on this analysis, a modified correlation between the pressure wave amplitude and the maximum pressure rise rate (MPRR) is developed by introducing an MPRR offset to account for the expansion work.

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.

A sampling system was developed to measure the evolution of the speciated hydrocarbon emissions from a single-cylinder SI engine in a simulated starting and warm-up procedure. A sequence of exhaust samples was drawn and stored for gas chromatograph analysis. The individual sampling aperture was set at 0.13 s which corresponds to ∼ 1 cycle at 900 rpm. The positions of the apertures (in time) were controlled by a computer and were spaced appropriately to capture the warm-up process. The time resolution was of the order of 1 to 2 cycles (at 900 rpm). Results for four different fuels are reported: n-pentane/iso-octane mixture at volume ratio of 20/80 to study the effect of a light fuel component in the mixture; n-decane/iso-octane mixture at 10/90 to study the effect of a heavy fuel component in the mixture; m-xylene and iso-octane at 25/75 to study the effect of an aromatics in the mixture; and a calibration gasoline.

Throttle ramp rate effects on the in-cylinder fuel/air (F/A) excursion was studied in a production engine. The fuel delivered to the cylinder per cycle was measured in-cylinder by a Fast Response Flame Ionization detector. Intake pressure was ramped from 0.4 to 0.9 bar. Under slow ramp rates (∼1 s ramp time), the Engine Electronic Control (EEC) unit provided the correct compensation for delivering a stoichiometric mixture to the cylinder throughout the transient. At fast ramp rates (a fraction of a second ramps), a lean spike followed by a rich one were observed. Based on the actual fuel injected in each cycle during the transient, a x-τ model using a single set of x and τ values reproduced the cycle-to-cycle in-cylinder F/A response for all the throttle ramp rates.

The heat release characteristics in terms of the maximum pressure rise rate (MPRR) and combustion phasing in a partially premixed compression ignition (PPCI) engine are studied using a calibration gasoline. Early port fuel injection provides a nearly homogeneous charge, into which a secondary fuel pulse is added via direct injection (DI) to provide stratification which is affected by the timing of the start of injection (SOI). As the SOI the DI fuel is retarded from early compression, MPRR first decreases, then increases substantially, and decreases again. The MPRR correlates mostly with the combustion phasing. The SOI timing plays an indirect role. The observation is explained by a bulk heat release process of which the rate increases with temperature rather than by a sequential ignition process. Observations from compression ignition of representative homogeneous charges in a Rapid Compression Machine support this explanation.

The use of direct injection spark ignition (DISI) engines for passenger cars has increased; providing greater specific performance and lower CO₂ emissions. DISI engines, however, produce more particulate matter (PM) emissions than Port-Fuel-Injected (PFI) engines. Forthcoming European exhaust emissions legislation is addressing concerns over health effects of PM emissions. Accordingly, research into PM emission formation has increased. A model developed by Aikawa et al., (2010) for PFI engines correlated PM number emissions with the vapor pressure and the double bond equivalent (DBE) of the components of the fuel. However there was no independent control of these parameters. This study investigates a particulate emissions index for DISI engines.

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.

The initial flame kernel behavior in a SI engine was measured by a spark-plug-fiber-optics probe. From these measurements, the flame kernel may be characterized by an expansion speed and a convection velocity. These quantities were correlated with the bum rate on a cycle-to-cycle basis in an engine configurated with quiescent, swirl, and tumble in-cylinder motion. The expansion speed correlates well with the 0-2 percent mass burn duration for all the configurations. The flame convection velocity depends on the in-cylinder motion in the expected manner. There was, however, only a weak correlation between the 10-90 percent burn duration and the initial flame kernel behavior.

The emission of nanoparticles from combustion engines has been shown to have a poorly understood impact on the atmospheric environment and human health, and legislation tends to err on the side of caution. Researchers have shown that Gasoline Direct Injection (GDI) engines tend to emit large amounts of small-sized particles compared to diesel engines fitted with Diesel Particulate Filters (DPFs). As a result, the particulate number emission level of GDI engines means that they could face some challenges in meeting the likely EU6 emissions requirement. This paper presents size-resolved particle number emissions measurements from a spray-guided GDI engine and evaluates the performance of an Evaporation Tube (ET). The performance of an Evaporation Tube and hot air dilution system with a 7:1 dilution ratio has been studied, as the EU legislation uses these to exclude volatile particles.

To understand the effects of crevices on the engine-out hydrocarbon emissions, a series of engine experiments was carried out with different piston crevice volumes and with simulated head gasket crevices. The engine-out HC level was found to be modestly sensitive to the piston crevice size in both the warmed-up and the cold engines, but more sensitive to the crevice volume in the head gasket region. A substantial decrease in HC in the cold-to-warm-up engine transition was observed and is attributed mostly to the change in port oxidation.

The effects of charge motion and laminar flame speeds on combustion and exhaust temperature have been studied by using an air jet in the intake flow to produce an adjustable swirl or tumble motion, and by replacing the nitrogen in the intake air by argon or CO₂, thereby increasing or decreasing the laminar flame speed. The objective is to examine the "Late Robust Combustion" concept: whether there are opportunities for producing a high exhaust temperature using retarded combustion to facilitate catalyst warm-up, while at the same time, keeping an acceptable cycle-to-cycle torque variation as measured by the coefficient of variation (COV) of the net indicated mean effective pressure (NIMEP). The operating condition of interest is at the fast idle period of a cold start with engine speed at 1400 RPM and NIMEP at 2.6 bar. A fast burn could be produced by appropriate charge motion. The combustion phasing is primarily a function of the spark timing.

A model for the evaporation of a multi-component fuel droplet is presented that takes account of temperature dependent fuel and vapour properties, evolving droplet internal temperature distribution and composition, and enhancement to heat and mass transfer due to droplet motion. The effect on the internal droplet mixing of non-ideal fluid diffusion is accounted for. Activity coefficients for vapour-liquid equilibrium and diffusion coefficients are determined using the UNIFAC method. Both well-mixed droplet evaporation (assuming infinite liquid mass diffusivity) and liquid diffusion-controlled droplet evaporation (iteratively solving the multi-component diffusion equation) have been considered. Well-mixed droplet evaporation may be applicable with slow evaporation, for example early gasoline direct injection; diffusion-controlled droplet evaporation must be considered when faster evaporation is encountered, for example when injection is later, or when the fuel mixture is non-ideal.

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.

The combustion process after auto-ignition is investigated. Depending on the non-uniformity of the end gas, auto-ignition could initiate a flame, produce pressure waves that excite the engine structure (acoustic knock), or result in detonation (normal or developing). For the “acoustic knock” mode, a knock intensity (KI) is defined as the pressure oscillation amplitude. The KI values over different cycles under a fixed operating condition are observed to have a log-normal distribution. When the operating condition is changed (over different values of λ, EGR, and spark timing), the mean (μ) of log (KI/GIMEP) decreases linearly with the correlation-based ignition delay calculated using the knock-point end gas condition of the mean cycle. The standard deviation σ of log(KI/GIMEP) is approximately a constant, at 0.63. The values of μ and σ thus allow a statistical description of knock from the deterministic calculation of the ignition delay using the mean cycle properties

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.