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The paper deals with the development of active front-end rectifier model based on dynamic phasors concept. The model addresses the functional modeling level as defined by the multi-layer modeling paradigm and is suitable for accelerated simulation studies of the electric power systems under normal, unbalanced and line fault conditions. The performance and effectiveness of the developed model have been demonstrated by comparison against time-domain models in three-phase and synchronous space-vector representations. The experimental verification of the dynamic phasor model is also reported. The prime purpose of the model is for the simulation studies of more-electric aircraft power architectures at system level; however it can be directly applied for simulation study of any other electrical power system interfacing with active front-end rectifiers.

The more-electric aircraft (MEA) is the major trend for airplanes in the next generation. Comparing with traditional airplanes, a significant increase of on-board electrical and electronic devices in MEAs has been recognized and resulted in new challenges for electrical power system (EPS) designers. The design of EPS essentially involves in extensive simulation work in order to ensure the availability, stability and performance of the EPS under all possible operation conditions. Due to the switching behavior of power electronic devices, it is very time-consuming and even impractical to simulate a large-scale EPS with some non-linear and time-varying models. The functional models in the dq0 frame have shown great performance under balanced conditions but these models become very time-consuming under unbalanced conditions, due to the second harmonics in d and q axes. The dynamic phasor (DP) technique has been proposed to solve that problem.

A Ford 2.4-liter 115PS light-duty diesel engine was modified to allow solenoid control of the oil feed to the piston cooling jets, enabling these to be switched on or off on demand. The influence of the jets on piston temperatures, engine thermal state, gaseous emissions and fuel economy has been investigated. With the jets switched off, piston temperatures were measured to be between 23 and 88°C higher. Across a range of speed-load points, switching off the jets increased engine-out emissions of NOx typically by 3%, and reduced emissions of CO by 5-10%. Changes in HC were of the same order and were reductions at most conditions. Fuel consumption increased at low-speed, high-load conditions and decreased at high-speed, low-load conditions. Applying the results to the NEDC drive cycle suggests active on/off control of the jets could reduce engine-out emissions of CO by 6%, at the expense of a 1% increase in NOx, compared to the case when the jets are on continuously.

Reducing friction in crankshaft bearings during cold engine operation by heating the oil supply to the main gallery has been investigated through experimental investigations and computational modelling. The experimental work was undertaken on a 2.4l DI diesel engine set up with an external heat source to supply hot oil to the gallery. The aim was to raise the film temperature in the main bearings early in the warm up, producing a reduction in oil viscosity and through this, a reduction in friction losses. The effectiveness of this approach depends on the management of heat losses from the oil. Heat transfer along the oil pathway to the bearings, and within the bearings to the journals and shells, reduces the benefit of the upstream heating.

Soot formation and distribution inside the cylinder of a light-duty direct injection diesel engine, have been predicted using Kiva-3v CFD software. Pathlines of soot particles traced from specific in-cylinder locations and crank angle instants have been explored using the results for cylinder charge motion predicted by the Kiva-3v code. Pathlines are determined assuming soot particles are massless and follow charge motion. Coagulation and agglomeration have not been taken into account. High rates of soot formation dominate during and just after the injection. Oxidation becomes dominant after the injection has terminated and throughout the power stroke. Computed soot pathlines show that soot particles formed just below the fuel spray axis during the early injection period are more likely to travel to the cylinder wall boundary layer. Soot particles above the fuel spray have lesser tendency to be conveyed to the cylinder wall.

The effect of compression ratio on sensitivity to changes in start of injection and air-fuel ratio has been investigated on a single-cylinder DI diesel engine at fixed low and medium speeds and loads. Compression ratio was set to 17.9:1 or 13.7:1 by using pistons with different bowl sizes. Injection timing and air-to-fuel ratio were swept around a nominal map point at which gross IMEP and NOx values were matched for the two compression ratios. It was found that CO, HC and ISFC were higher at low compression ratio, but the soot/NOx trade-off improved and this could be exploited to reduce the fuel economy penalty. Sensitivity to inputs is generally similar, but high compression ratio tended to have steeper response gradients. Reducing compression ratio to 13.7 gave rise to a marked degradation of performance at light load, producing high CO emissions and a fall in combustion efficiency. This could be eased by reducing rail pressure, but the advantage in smoke emission was lost.

The largest contribution to engine rubbing friction is made by the piston and piston rings running in the cylinder liner. The magnitude and characteristics of the friction behaviour and the influence on these of factors such as surface roughness, piston design and lubricant properties are of keen interest. Investigating presents experimental challenges, including potential problems of uncontrolled build-to-build variability when component changes are made. These are addressed in the design of a new motored piston and floating liner rig. The design constrains transverse movement of a single liner using cantilevered mounts at the top and bottom. The mounts and two high stiffness strain gauged load cells constrain vertical movement. The outputs of the load cells are processed to extract the force contribution associated with friction. The liner, piston and crankshaft parts were taken from a EuroV-compliant, HPCR diesel engine with a swept capacity of 550cc per cylinder.

Currently the wing box rib assembly process requires the manual location and temporary fixing of components within product specific jig or fixtures for drilling. After drilling and reaming, parts are separated, cleaned, deburred prior to adding sealant, reclaiming and final bolting, but this may significantly increase cost, manufacturing lead-time, reduces flexibility and cannot usually be economically modified for use on other aircraft types. Due to potential increase in demand for the next generation single isle aircraft, existing tooling solutions have to be improved and new technologies have to be developed. This paper describes the development and testing of flexible tooling to provide clamping and support for drilling wing box ribs to mating rib posts within a restricted environment. Results are presented along with a discussion of the problems that may be encountered during clamping trials.

Increases in fuel costs and environmental concerns have in recent years heightened the importance of fuel efficiency as a design consideration in vehicles, especially aircraft. For this reason, a greater understanding of the energy consumption of vehicles is needed, both for design and operational decisions. Exergy, a measure of available work in an imbalance of state, allows systems to be compared on an equal basis with losses and waste being equated to fuel costs. Vehicles and especially aircraft do not operate in steady state as do industrial plants, the traditional subject of exergy analysis. While some analysis of aircraft has been performed in the literature, time-variance has not been addressed, leading to a lack of detail and only very broad conclusions. It is proposed that in order to fully understand aircraft energy use, a fully time-variant analysis must be performed.

The aerospace manufacturing sector is continuously seeking automation due to increased demand for the next generation single-isle aircraft. In order to reduce weight and fuel consumption aircraft manufacturers have increasingly started to use more composites as part of the structure. The manufacture and assembly of composites poses different constraints and challenges compared to the more traditional aircraft build consisting of metal components. In order to overcome these problems and to achieve the desired production rate existing manufacturing technologies have to be improved. New technologies and build concepts have to be developed in order to achieve the rate and ramp up of production and cost saving. This paper investigates how to achieve the rib hole key characteristic (KC) in a composite wing box assembly process. When the rib hole KC is out of tolerances, possibly, the KC can be achieved by imposing it by means of adjustable tooling and fixturing elements.

The development of an analytical model for multilayer stack subjected to temperature change is demonstrated here. Thin continuous layers of materials bonded together deform as a plate due to their differing coefficients of thermal expansion upon subjecting the bonded materials to the change in temperature. Applications of such structures can be found in the electronics industry (the study of warpage issues in printed circuit boards) or in the aerospace industry as (the study of laminated thin sheets used as skin structures for load bearing members such as wings and fuselage). In automotive electronics, critical high-power packages (IGBT, Power FETs) include several layers of widely differing materials (aluminum, solder, copper, ceramics) subjected to wide temperature cyclic ranges. Modeling of such structures by using three-dimensional finite element methods is usually time consuming and may not exactly predict the inter-laminar strains.

This paper considers a wide range of options for the allowing regeneration onto the aircraft bus for possible inclusion in future aircraft power quality specifications. For many loads, such as actuators, the size and weight of power converters could be significantly reduced if the requirement to avoid regeneration was removed from the specifications.

This paper investigates the application of thick film hybrid circuit technology on ceramic substrate in comparison to the main stream substrate FR-4 (Flame Retardant 4) for PCB implementation. The study is based on computer models for these very substrates in order to simulate the propagation of heat through convection and conduction within the material boundaries. In order to simulate electronic components surface mounted, different heat sources are randomly arranged on physical contact to the surface of the material under investigation. The results emphasize and discern the usage of both substrates and its most suitable environment verifying the application towards vehicular integration. Future study may include experimental analysis for simulated data verification and validation of thick film hybrid circuit technology for the automotive industry.

An experimental study has been carried out to examine the influence of ring tan load and piston skirt modifications on piston assembly friction under motored engine conditions for initial temperatures of -20, 0 and 30°C and motoring speeds within the range 400 to 2000 rev/min. The study has been carried out using the block, crankshaft and pistons of a 2.4I, 4 cylinder diesel engine with a bore and stroke of 89.9mm and 94.6mm respectively. The pistons examined are typical of current designs for light duty diesels. A range of ring pack and piston skirt modifications have been tested, in each case as part of a complete piston assembly. The first changes produced reductions in fmep of between 5% and 38%. The reduction was due to improved skirt and ring pack designs in equal measure, each giving improvements of up to 20%. From this baseline eliminating the tan load of the piston rings was projected to give a further reduction in fmep of between 10% and 20%.

An experimental investigation has been carried out to compare the indicated performance and heat release characteristics of a DI diesel engine at compression ratios of 18.4:1 and 15.4:1. The compression ratio was changed by modifying the piston bowl volume; the bore and stroke were unchanged, and the swept volume was nominally 500cc. The engine is a single cylinder variant of modern design which meets Euro 4 emissions requirements. Work output and heat release characteristics for the two compression ratios have been compared at an engine speed of 300 rev/min and test temperatures of 10, -10 and -20°C. A more limited comparison has also been made for higher speeds representative of cold idle at one test temperature (-20°C). The reduction in compression ratio generally produces an increase in peak specific indicated work output at low speeds; this is attributable to a reduction in blowby and heat transfer losses and lower peak rates of heat release increasing cumulative burn.

It is well known that the design of the seal groove assembly in the brake caliper greatly influences the braking performance. The rubber seal performs the dual function of sealing the piston bore and retracting the caliper piston after a brake apply. However, the seal function is affected by the configuration of the seal groove, as well as the friction at the piston/seal and groove/seal interfaces. The material properties of the rubber seal are also important design parameters. Issues such as fluid displacement, piston retraction, piston sliding force, and brake drag are some of the critical brake performance parameters that must be considered in every caliper seal-groove design. Presently, the brake caliper seal groove design is still based on empirical rules established mainly from past experience and its performance is achieved through prototype testing.

This paper presents a theoretical and experimental study of a cylinder deactivation valvetrain system for the integration into an Engine Management System (EMS). A control-oriented lumped parameter model of the deactivation valvetrain system is developed and implemented using Matlab/Simulink, and validated by experimental data. Through simulation and experimental data analysis, the effect of operating conditions on the dynamic response is captured and characterized, over a wide range of operating conditions. The algorithm provides a basis for the calibration of the deactivation hardware. The generic characterization of the dynamic response can simplify the calibration parameters for the implementation in engine management systems.

In recent years, the increasing interest and requirements for improved engine diagnostics and control has led to the implementation of several different sensing and signal processing technologies. In order to optimize the performance and emission of an engine, detailed and specified knowledge of the combustion process inside the engine cylinder is required. In that sense, the torque generated by each combustion event in an IC engine is one of the most important variables related to the combustion process and engine performance. This paper introduces torque estimation techniques in the real-time basis for engine control applications using the measurement of crankshaft speed variation. The torque estimation scheme presented in this paper consists of two entirely different approaches, “Stochastic Analysis” and “Frequency Analysis”.

Compromises inherent with fixed valve lift and event timing have prompted engine designers to consider Variable Valve Actuation (VVA) systems for many decades. In recent years, some relatively basic forms of VVA have been introduced into production engines. Greater performance and driveability expectations of customers, more stringent emission regulations set by government legislators, and the mutual desire for higher fuel economy are increasingly at odds. As a solution, many OEM companies are seriously considering large-scale application of higher function VVA mechanisms in their next generation vehicles. This paper describes the continuing development progress of a mechanical VVA system. Design features and operation of the mechanism are explained. Test results are presented in two sections: motored cylinder head test data focuses on VVA system friction, control system performance, valve lift and component stress.

In the catalytic converter, the thermal conductivity of the insulation material (intumescent mat) placed between the ceramic catalyst and the metal shell is strongly dependent on the temperature, resulting in the solving of non-linear heat conduction equations. In this paper, the analytic solution for the steady heat flow in a cylinder with temperature dependent conductivity is given. Using this analytic solution for the mat and including convection and radiation at the converter skin, an analytical expression for calculating converter skin temperature is obtained. This expression can be easily incorporated in a Fortran code to calculate the temperatures.