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Journal Article

Innovations In Experimental Techniques For The Development of Fuel Path Control In Diesel Engines

The recent development of diesel engine fuel injection systems has been dominated by how to manage the degrees of freedom that common rail multi-pulse systems now offer. A number of production engines already use four injection events while in research, work based on up to eight injection events has been reported. It is the degrees of freedom that lead to a novel experimental requirements. There is a potentially complex experimental program needed to simply understand how injection parameters influence the combustion process in steady state. Combustion behavior is not a continuum and as both injection and EGR rates are adjusted, distinct combustion modes emerge. Conventional calibration processes are severely challenged in the face of large number of degrees of freedom and as a consequence new development approaches are needed.
Technical Paper

In-Cylinder Pressure Modelling with Artificial Neural Networks

More and more stringent emission regulations require advanced control technologies for combustion engines. This goes along with increased monitoring requirements of engine behaviour. In case of emissions behaviour and fuel consumption the actual combustion efficiency is of highest interest. A key parameter of combustion conditions is the in-cylinder pressure during engine cycle. The measurement and detection is difficult and cost intensive. Hence, modelling of in-cylinder conditions is a promising approach for finding optimum control behaviour. However, on-line controller design requires real-time scenarios which are difficult to model and current modelling approaches are either time consuming or inaccurate. This paper presents a new approach of in-cylinder condition prediction. Rather than reconstructing in-cylinder pressure signals from vibration transferred signals through cylinder heads or rods this approach predicts the conditions.
Journal Article

The Impact of Biodiesel on Particle Number, Size and Mass Emissions from a Euro4 Diesel Vehicle

New European emissions legislation (Euro5) specifies a limit for Particle Number (PN) emissions and therefore drives measurement of PN during vehicle development and homologation. Concurrently, the use of biofuel is increasing in the marketplace, and Euro5 specifies that reference fuel must contain a bio-derived portion. Work was carried out to test the effect of fuels containing different levels of Fatty Acid Methyl Ester (FAME) on particle number, size, mass and composition. Measurements were conducted with a Cambustion Differential Mobility Spectrometer (DMS) to time-resolve sub-micron particles (5-1000nm), and a Horiba Solid Particle Counting System (SPCS) providing PN data from a Euro5-compliant measurement system. To ensure the findings are relevant to the modern automotive business, testing was carried out on a Euro4 compliant passenger car fitted with a high-pressure common-rail diesel engine and using standard homologation procedures.
Technical Paper

Modeling Techniques to Support Fuel Path Control in Medium Duty Diesel Engines

In modern production diesel engine control systems, fuel path control is still largely conducted through a system of tables that set mode, timing and injection quantity and with common rail systems, rail pressure. In the hands of an experienced team, such systems have proved so far able to meet emissions standards, but they lack the analytical underpinning that lead to systematic solutions. In high degree of freedom systems typified by modern fuel injection, there is substantial scope to deploy optimising closed loop strategies during calibration and potentially in the delivered product. In an optimising controller, a digital algorithm will explicitly trade-off conflicting objectives and follow trajectories during transients that continue to meet a defined set of criteria. Such an optimising controller must be based on a model of the system behaviour which is used in real time to investigate the consequences of proposed control actions.
Technical Paper

Modelling the Exhaust Gas Recirculation Mass Flow Rate in Modern Diesel Engines

The intrinsic model accuracy limit of a commonly used Exhaust Gas Recirculation (EGR) mass flow rate model in diesel engine air path control is discussed in this paper. This EGR mass flow rate model is based on the flow of a compressible ideal gas with unchanged specific heat ratio through a restriction cross-area within a duct. A practical identification procedure of the model parameters is proposed based on the analysis of the engine data and model structure. This procedure has several advantages which include simplicity, low computation burden and low engine test cost. It is shown that model tuning requires only an EGR valve sweep test at a few engine steady state operating points.
Technical Paper

Starting and Developing an Engineering Career: The Barriers and Opportunities

There has probably never been such a demand for professionally qualified engineers, and yet both the number and diversity of people entering the profession continue to decline. Worldwide, there are very many initiatives - some generally encouraging interest in the profession, and others targeting specific audiences. The reports speak of local success, but the overall picture remains discouraging. In this paper we focus on the “pipeline” from primary education through to the transition from graduate engineer into an experienced member of engineering staff. We have based the discussion on both the presentations and comments made during a panel discussion held at the 2013 SAE International Congress. The paper is intended as a summary of the points raised during that discussion and, we hope proves to be starting point for further investigation and analysis. Of particular note is the sheer diversity of initiatives, and the pressing need for role models and mentoring.
Technical Paper

More Leaders and Fewer Initiatives: Key Ideas for the Future of Engineering

Panel Discussions held at the SAE World Congress in both 2013 and 2014 observed that a shortage of good quality engineering talent formed a chronic and major challenge. (“Good quality” refers to applicants that would be shortlisted for interview.) While doubts have been expressed in some quarters, the shortage is confirmed by automotive sector employers and the Panel's view was that it was symptomatic of a range of issues, all of which have some bearing on the future of the profession. Initiatives to improve recruitment and retention have had varying degrees of success. Efforts need to be intensified in primary schools where negative perceptions develop and deepen. Schemes like AWIM that operate on a large scale and are designed to supplement school curricula should operate at an international level. Universities represent the entry point into the engineering profession and their role in the recruitment process as well as education and training is crucial.
Technical Paper

Application of Computational Fluid Dynamics to the Study of Conditions Relevant to Autoignition Damage in Engines

The process of autoignition in an internal combustion engine cylinder produces large amplitude high frequency gas pressure waves accompanied by significant increases in gas temperature and velocity, and as a consequence large convective heat fluxes to piston and cylinder surfaces. Extended exposure of these surfaces to autoignition, results in their damage through thermal fatigue, particularly in regions where small clearances between the piston and cylinder or cylinder head, lie in the path of the oscillatory gas pressure waves. The ability to predict spatial and temporal' variations in cylinder gas pressure, temperature and velocity during autoignition and hence obtain reasonable estimates of surface heat flux, makes it possible to assess levels of surface fatigue at critical zones of the piston and cylinder head, and hence improve their tolerance to autoignition.
Technical Paper

Thermal Boundary Layer Modelling in ‘Motored’ Spark Ignition Engines

A newly developed piece-wise method for calculating the effects of near-wall turbulence on the transport of enthalpy and hence the thermal boundary layer temperature profile in “motored” spark ignition engines has been compared with methods that have previously been employed in the development of expressions for the gas-wall interface heat flux. Near-wall temperature profiles resulting from the inclusion of the respective expressions in a “quasi-dimensional” thermodynamic engine simulation have been compared and in one case show considerable differences throughout the compression and expansion strokes of the “motored” engine cycle. However, the corresponding heat fluxes calculated from the simulated temperature profiles all show good agreement with measured results.
Technical Paper

Simulation of Exhaust Unburned Hydrocarbons from a Spark Ignition Engine, Originating from In-Cylinder Crevices

In this paper the effect of in-cylinder crevices formed by the piston cylinder clearance, above the first ring, and the spark plug cavity, on the entrapment of unburned fuel air mixture during the late compression, expansion and exhaust phases of a spark ignition engine cycle, have been simulated using the Computational Fluid Dynamic (CFD) code KIVA II. Two methods of fuelling the engine have been considered, the first involving the carburetion of a homogeneous fuel air mixture, and the second an attempt to simulate the effects of manifold injection of fuel droplets into the cylinder. The simulation is operative over the whole four stroke engine cycle, and shows the efflux of trapped hydrocarbon from crevices during the late expansion and exhaust phases of the engine cycle.
Technical Paper

Optimum knock sensor location through experimental modal analysis of engine cylinder block

The knock sensor is provided on an engine cylinder block to detect abnormal engine combustion (knocking) and to provide feedback to engine control unit (ECU). The ECU then modifies the engine input and avoids knocking. A commonly used knock sensor is an accelerometer that detects cylinder wall vibration and estimates knocking of the engine. Selecting the location of a knock sensor in many cases involves a challenging trial and error approach that depends upon the measurement of the knock signal at many locations on engine structure. However, a cylinder block exhibits many structural resonances. Thus, a large vibration signal at the surface of cylinder block can be either due to knocking of the engine or due to the resonances of the cylinder block structure because of normal excitation forces. Hence, this conventional method does not always yield reliable results.
Technical Paper

A Study on Attenuating Gear Teeth Oscillations at Low Engine Speeds Using Nonlinear Vibration Absorbers

Gear oscillations are one of the most common sources of Noise, Vibration and Harshness (NVH) issues manifested in automotive powertrains. These oscillations are generated mainly due to impacts of the meshing gear teeth over a broad frequency range. To mitigate NVH phenomena, automotive manufacturers traditionally couple linear tuned vibration absorbers to the driveline. Common palliatives used are clutch dampers and dual mass flywheels, which generally suppress vibrations effectively only over narrow frequency bands. Nonlinear Energy Sinks (NESs) are a class of vibration absorbers with essentially nonlinear characteristics that are designed for dissipating vibration energy over broad frequency ranges (due to the employed nonlinearity). The NES does not have a preferential natural frequency; this is rather characterized by the nonlinear stiffness.
Journal Article

Accurate and Continuous Fuel Flow Rate Measurement Prediction for Real Time Application

One of the most critical challenges currently facing the diesel engine industry is how to improve fuel economy under emission regulations. Improvement in fuel economy can be achieved by precisely controlling Air/Fuel ratio and by monitoring fuel consumption in real time. Accurate and repeatable measurements of fuel rate play a critical role in successfully controlling air/fuel ratio and in monitoring fuel consumption. Volumetric and gravimetric measurements are well-known methods for measuring fuel consumption of internal combustion engines. However, these methods are not suitable for obtaining fuel flow rate data used in real-time control/measurement. In this paper, neural networks are used to solve the problem concerning discontinuous data of fuel flow rate measured by using an AVL 733 s fuel meter. The continuous parts of discontinuous fuel flow rate are used to train and validate a neural network, which can then be used to predict the discontinuous parts of the fuel flow rate.
Technical Paper

Effects of Fuel Injection Parameters on Low Temperature Diesel Combustion Stability

Low temperature diesel combustion (LTC) exhibits ultra low NOx and smoke emissions, but currently it has the problems of increased CO and THC emissions, and higher combustion instability compared to conventional diesel combustion. This study evaluated the effects of fuel injection parameters on combustion stability in a single cylinder research diesel engine running at low and intermediate speeds and loads under LTC operating conditions. The LTC operation was achieved using high rates of EGR. In this work, the fuel injection timing and injection pressure were varied to investigate their effects on combustion stability at fixed engine speed and total fuel quantity. The cylinder pressure and THC emissions were measured during the tests. The THC emissions and the coefficient of variability of IMEP (CoV(IMEP)) were used to assess combustion stability. The relationship between these two parameters was also evaluated.
Technical Paper

Model for Drivers' Perception of Vehicle Performance

A driver's preference for one of two different vehicle models that have the same measurable acceleration may be explained by complicated factors such as styling, NVH or ergonomics. If the vehicles have identical appearance but different levels of engine tune, discrimination would probably be due to the measurable difference in performance although other factors cannot be entirely discounted. If however, the assessment is made of vehicles with identical appearance and identical performance then any preference is attributable to an area of human assessment that has been termed subjective performance. This paper discusses the first step in a qualitative approach to the analysis of driver perception of vehicle performance and more specifically investigates subjective performance. The proposed model ascribes distinct components such as induced and perceived performance to the total subjective performance rating.
Technical Paper

The Investigation into a PC-Based Fluidic Fuel Injection System for Passenger Cars

This paper describes a gasoline injection system based on air-assisted fluidic injectors. This injection system was implemented on a research engine and the results of air to fuel ratio (AFR) variations, engine combustion characteristics and exhaust emissions from the fluidic injector unit were compared with those from the baseline solenoid type injector. It was demonstrated that the fluidic system produces 9% to 20% lower HC emissions and 5% to 8% higher IMEP than the baseline injection system. This has confirmed the effectiveness of the use of the air-assisted fluidic injector stages and that the improved mixture preparation fuel presentation are obtained by the fluidic system. However, the cyclic flow stability of the fluidic device needs improvement.
Technical Paper

Measurement of Formula One Car Drag Forces on the Test Track

Coastdown testing is a proven method for determining the drag coefficients for road cars whilst the vehicle is in its normal operating environment. An accurate method of achieving this has been successfully developed at Loughborough University. This paper describes the adaptation and application of these techniques to the special case of a contemporary Formula One racing car. The work was undertaken in conjunction with the Benetton Formula One racing team. The paper outlines the development and application of a suitable mathematical model for this particular type of vehicle. The model includes the aerodynamic, tyre, drivetrain and the un-driven wheel drags and accounts for the change in aerodynamic drag due to ambient wind and changes in vehicle ride height during the coastdown. The test and analysis methods are described.
Technical Paper

Predicting the Onset of End-Gas Autoignition with a Quasi-Dimensional Spark Ignition Engine Model

A predictive, quasi-dimensional simulation of combustion in a spark ignition engine has been coupled with a chemical kinetic model for the low temperature, pre-flame reactions of hydrocarbon fuel and air mixtures. The simulation is capable of predicting the onset of autoignition without prior knowledge of the cylinder pressure history. Near-wall temperature gradients were computed within the framework of the engine cycle simulation by dividing the region into a number of thin mass slices which were assumed to remain adjacent to the combustion chamber surfaces in both the burned and unburned gas. The influence of the near-wall turbulence on the temperature field was accounted for by means of a boundary layer turbulence model developed by the authors. Fluid motion in the bulk gases has been considered by the inclusion of a turbulence model based on k - ε theory while the flame propagation rate was predicted using a fractal flame model.
Technical Paper

International Teaming in Aircraft Design Education

An experiment is described in which students from two universities, one in the UK and one in the USA, worked together in multidisciplinary teams on aircraft design projects to satisfy the “capstone” design course requirements in their respective degree programs. Aeronautical, Mechanical, Industrial, and Systems Engineering students from Virginia Tech and Loughborough University were placed on teams to work on two different airplane designs. The paper describes the evolution of this educational collaboration and the organization of the experiment. It also reviews the program ’s successes and its problems. Recommendations are made for continuation of the program and to guide others who might be interested in pursuing a similar experiment.
Technical Paper

Application of CFD to the Matching of In-Cylinder Fuel Injection and Air Motion in a Four Stroke Gasoline Engine

The in cylinder air motion, fuel air mixing, evaporation, combustion and exhaust emissions have been simulated for a four stroke direct injection gasoline engine using the KIVA II code. A strong controlled tumbling air motion was created in the cylinder, through a combination of a conventional pentroof four valve cylinder head, in conjunction with a piston having a stepped crown and offset combustion bowl. A range of injection strategies were employed to optimise combustion rate and exhaust emission (NOx and unburned hydrocarbons (fuel)), at two operating conditions - one with a stoichiometric air fuel mixture and the other with a lean mixture of 30:1 air/fuel ratio. Injection directed towards the piston bowl with a hollow cone jet, in a single pulse, has shown the best results regarding burned mass fraction and level of unburned HC. Fuel concentration, air motion, combustion characteristics and pollutants level are presented for lean and stoichiometric cases.