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Several new technologies are now emerging to improve adhesive supply and formulation along with surface treatments that have the potential to offer significant improvements to both surface energy and cleanliness [3]. Additionally, the miniaturisation of laboratory techniques into portable equipment offers potential for online surface energy and chemical analysis measurement for use as quality control measures in a production environment. An overview of newly available technology is given here with several devices studied in further detail. Technologies assessed further in this paper are; portable surface contact angle measurement, ambient pressure plasma cleaning, portable FTIR measurement and adhesive mixing equipment. A number of potential applications are outlined for each device based on the operational technique. The practical aspects of implementation and the perceived technology readiness levels for operation, implementation and results are also given.

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.

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.

The assembly and manufacture of aerospace structures, in particular legacy products, relies in many cases on the skill, or rather the craftsmanship, of a human operator. Compounded by low volume rates, the implementation of a fully automated production facility may not be cost effective. A more efficient solution may be a mixture of both manual and automated operations but herein lies an issue of human error when stepping through the build from a manual operation to an automated one. Hence the requirement for an advanced automated assembly system to contain functionality for inline structural quality checking. Machine vision, used most extensively in manufacturing, is an obvious choice, but existing solutions tend to be application specific with a closed software development architecture.

Aircraft manufacturers desire to increase production to keep up with anticipated demand. To achieve this, the aerospace industry requires a significant increase in the manufacturing and assembly performance to reach required output levels. This work therefore introduces the Variation Aware Assembly (VAA) concept and identifies its suitability for implementation into aircraft wing assembly processes. The VAA system concept focuses on achieving assemblies towards the nominal dimensions, as opposed to traditional tooling methods that aim to achieve assemblies anywhere within the tolerance band. It enables control of the variation found in Key Characteristics (KC) that will allow for an increase in the assembly quality and product performance. The concept consists of utilizing metrology data from sources both before and during the assembly process, to precisely position parts using motion controllers.

Diesel engines have traditionally been favoured in heavy-duty applications for their fuel economy, robustness, reliability and relative lack of fuel sensitivity. Recently it has seen a growth in its popularity in light duty applications due particularly to its fuel efficiency. However, as the engine technology and particularly the fuel injection equipment has evolved to meet ever stricter emissions legislation the engines have become more sensitive to deposit formation resulting from changes in fuel quality. This paper reviews bouts of concern over diesel fuel injector deposits, possible causes for the phenomenon and test methods designed to screen fuels to eliminate problems.

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 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.

Electric machines in aerospace applications are subjected to extremely high operating temperatures. This increases coercivity or decreases saturation flux density of the electrical steel resulting in increased core loss. The need for high power density and increased operating speed favours the use of thin gauge Silicon Steel (Si-Fe) and Cobalt Iron (Co-Fe) laminations for aerospace applications. Therefore, the variation in iron loss is studied for three grades of Si-Fe laminations by subjecting them to controlled ageing in laboratory. The analysis is also provided over a range of flux density and frequency to generalize the phenomenon over the operating domain. The results of ageing the laminations are in turn used to predict the degradation in performance of a 1.15 MW, 16-pole 48-slot propulsion machine for aerospace application. The degradation is estimated in terms of variation in iron loss.

A computational model has been developed to support investigations of temperature, heat flow and friction characteristics, particularly in connection with warm-up behaviour. A lumped capacity model of the engine block and head, empirically derived correlations for local heat transfer and friction losses, and oil and coolant circuit descriptions form the core of the model. Validation of the model and illustrative results are reported.

Two methods of determining the rate of heat transfer from the combustion chamber have been investigated. A First Law analysis is shown to be ill-conditioned because of sensitivity to heat release and gas property calculations. An alternative approach equates cycle-averaged chamber heat transfer to the difference between heat rejected to the coolant and gas heat transfer to the exhaust port. This has been examined as a basis for calibrating the Woschni correlation.

Spark plug fouling is a common problem when vehicles are repeatedly operated for very short periods, particularly at low temperatures. This paper describes a test procedure which uses a series of short, high-load drive cycles to assess plug fouling under realistic conditions. The engine is force cooled between drive cycles in order to increase test throughput. Spark plug resistance is shown to be a poor indicator of the effect of fouling on engine performance and the rate of misfiring is given as an alternative measure. An automated technique to detect misfires from engine speed data is described. This has been used to investigate the effect of spark plug type, fuelling level and spark timing on fouling. Spark plugs which are designed to run hotter are found to be more resistant to plug fouling. Isolated adjustments to fuelling level and spark timing calibrations within the range providing acceptable performance have a weak effect on susceptibility to plug fouling.

The cycle-by-cycle variation of heat transferred per cycle (q) to the combustion chamber surfaces of spark ignition engines has been investigated for quasi-steady and transient conditions produced by throttle movements. The heat transfer calculation is by integration of the instantaneous value over the cycle, using the Woschni correlation for the heat transfer coefficient. By examination of the results obtained, a relatively simple correlation has been identified: This holds both for quasi-steady and transient conditions and is on a per cylinder basis. The analysis has been extended to define a heat flux distribution over the surface of the chamber. This is given by: where F(x/L) is a polynomial function, q″ is the heat transfer per cycle per unit area to head and piston crown surfaces and gives the distribution along the liner

Surface-mounted heat flux sensors have been used in the intake port of a fuel injected, spark ignition engine to investigate heat transfer between the surface, the gas flows through the port, and fuel deposited in surface films. The engine is of a four valve per cylinder design, with a bifurcated intake port. For dry-port conditions heat transfer per cycle varies between 0 and 300 J/m2 depending on location, towards the surface at low temperatures and away from the surface at fully-warm conditions. Particular attention has been given to the changes in heat transfer rate associated with fuel deposition. Typically this is of the order of 5 kW/m2 in regions of heavy fuel deposition and varies by a factor of 2 over the period of an engine cycle. During warm-up, as coolant temperature increases from 0 to 90°C, changes in heat transfer associated with fuel deposition typically increase from 300 J/m2 to 1000 J/m2.

The rate of heat rejection to the coolant system of an internal combustion engine depends upon coolant composition, among other factors, because this influences the coolant side heat transfer coefficient. The correlation developed by Taylor and Toong for heat transfer rate has been modified to account for this effect. The modification retains the gas-to-coolant passage thermal resistance implicit in the original correlation. The modified correlation gives predictions in agreement with experimental data. Compared to 100% water, mixtures of 50% ethylene glycol/50% water lower heat rejection rates by typically 5% and up to 25% in the extreme. This depends upon local conditions in the coolant circuit, which can give rise to different heat transfer regimes. Application of the modified correlation is outlined and illustrated.

Previously reported studies of heat transfer between the intake port surface, gas flows in the port, and fuel deposited in surface films have been extended to examine details of the heat flux variations which occur within the engine cycle. The dynamic response characteristics of the surface-mounted heat flux sensors have been determined, and measured heat flux data corrected accordingly to account for these characteristics. Details of the model and data processing technique used are described. Corrected intra-cycle variations of heat transfer to fuel deposited have been derived for engine operating conditions at 1000 RPM covering a range of manifold pressures, fuel supply rates, port surface temperatures, and fuel injection timings. Both pump-grade gasoline and isooctane fuel have been used. The effects of operating conditions on the magnitude and features of the heat flux variations are described.

Surface heat transfer measurements have been taken in the intake port of a single cylinder four valve SI engine running on isooctane fuel. The objective has been to establish how fuel characteristics affect trends in surface heat transfer rates for a range of engine operating conditions. The heat transfer measurements were made using heat flux gauges bonded to the intake port surface in the region where highest rates of fuel deposition occur. The influence on heat transfer rates of the deposited fuel and its subsequent behaviour has been examined by comparing fuel-wetted and dry-surface heat transfer measurements. Heat transfer changes are consistent with trends predicted by convective mass transfer over much of the range of surface temperatures from 20°C to 100°C. Towards the upper temperature limit heat transfer reaches a maximum limited by the rate and distribution of fuel deposition.

A correlation for total gas-side heat transfer rate has been derived from the analysis of engine data for measured heat rejection rate, frictional dissipation, and published data on exhaust port heat transfer. The correlation is related to the form developed by Taylor and Toong, and the analysis draws on this. However, cylinder and exhaust port contributions are separated. Two empirical constants are fixed to best match predicted to measured results for heat rejection to coolant and oil cooler under steady-state conditions, and also for exhaust port heat transfer rates. The separated contributions also defined a correlation for exhaust port heat transfer rate. The description of gas-side heat transfer is suited to needs for the analysis of global thermal behaviour of engines.

Bleeding in engines is essential to mitigate the unmatched air massflow between low and High Pressure (HP) compressors at low speed settings, thus avoiding unstable operation due to surge and phenomena. However, by emerging the More Electric Aircraft (MEA) the engine is equipped with electrical machines on both high and Low Pressure (LP) spools which enables transfer of power electrically from one spool to another and hence provides the opportunity to operate engine core components closer to their optimum design point at off-design conditions. At lower power setting of the engine, HPC speed can be increased by taking power from LP shaft and feeding it to HP shaft which can lead to the removal of the bleeding system which in turn reduces weight and fuel consumption and help to overcome engine instability issues. Fuel consumption can be decreased by decreasing inconsistent thrust with the aircraft mission for flight and ground idle settings.