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This paper aims to assess the feasibility of largeeddy simulation LES as applied to a real engine configuration. Two cases of LES were performed together with a reference Reynoldsaveraged NavierStokes RANS simulation to study their performances in the prediction of the fuel injection and mixing in a highspeed directinjection diesel engine. In addition, sensitivity of the LES results with respect to mesh resolution was investigated, as LES requires a higher mesh density and the filtering process depends on the mesh size. The LES meant that detailed information could be obtained on the fuel spray development and turbulent flow field that was not possible to capture using the RANS modelling approach. It was found that the LES captures flow structures that have a pronounced impact on the prediction of the fuel injection and mixing. Highresolution LES predicted higher liquid and vapour penetration into the cylinder, which is in better agreement with the experimental data obtained at Delphi Diesel Systems than is the RANS prediction. It was also shown that using a finer mesh in LES yields improvements in turbulent flow field prediction, at the same time reducing contribution of the modelled part of the turbulent kinetic energy. Overall, it was proved that LES is a superior alternative to the traditional RANS approach for turbulent twophase flows encountered in diesel fuel injections where flow unsteadiness is prominent. Improved predictions obtained from an advanced LES can subsequently enhance the understanding of the fuel injection process and assist the engine experimentation and design.

A numerical study has been performed to investigate the soot emission from a high-speed single-cylinder direct injection diesel engine. The computational conditions were set to be the same as the test conditions in the experiments where measurements had been performed at two running speeds with two injector protrusions. It was shown that the KIVA CFD code can predict the experimental trend, where at a low-speed running condition a higher smoke reading is reached when increasing the injector protrusion into the piston chamber and, conversely, a lower smoke reading was recorded for the same change in injector protrusion at a high running speed condition. Although computational predictions yielded the same trend as the experimental results, the magnitudes of the smoke emissions were an order of magnitude over those predicted. Evidence of inappropriate air/fuel mixing of the model was seen via rates of heat release analyses, especially in the high-speed conditions. Therefore, efforts to reduce this discrepancy by way of improvements to the KIVA submodels were made. In particular, modifications to the breakup and evaporation models have been made in order better to represent the mixing of the high-speed liquid jets. A gaseous sphere per liquid droplet model was employed to improve the current KIVA model by improving the mass coupling effects, which effectively delays the addition of spray source terms to the gas phase equations. Results of the modified models showed improvements in the vapour dispersion of the atomizing liquid jet, thus affecting the mixing rates and predicted smoke emissions. Further improvements on the momentum coupling will be presented in Part 2 of this work.

This paper presents the application of digital imaging and image processing techniques for the quantitative characterization of diesel sprays. An optically accessible, constant volume chamber was configured to allow direct photographic imaging of diesel sprays, which were generated from a six-hole nozzle in a non-evaporating and pressurized environment. A high-resolution CCD camera and a flash light source were used to capture the images of the sprays. Dedicated image processing software has been developed to quantify a set of macroscopic, characteristic parameters of the sprays including tip penetration, near- and far-field angles. The spray parameters produced using this software are compared with those obtained using manual methods. The results obtained under typical spray conditions demonstrate that the software is capable of producing more accurate, consistent and efficient results than the manual methods. An application of the imaging processing software to the characterization of diesel sprays for a valve covered orifice nozzle is also presented and discussed.

A radiograph of the left hand and wrist was taken in 141 children and young adults with phenylketonuria and hyperphenylalaninaemia. Ten (7.1%) had a bony abnormality and, of these, six (4.3%) showed evidence of reduced bone density. Only one patient had evidence of spiculation of the lower ulnar metaphysis previously described in phenylketonuria. Bone maturity was also assessed in 130 patients by the Tanner-Whitehouse (TW2) method. In 28 patients (21.5%) bone age was less than chronological age by 1 year or more. Bone age delay was greater in younger children on a more restricted diet with a lower intake of natural protein.

Background—Associations between genotype and intellectual outcome in patients with phenylketonuria are complicated because intelligence is influenced by many variables, including environmental factors and other genetic determinants. Intellectual changes with age, both on and after relaxation of diet, vary within the patient population. This study aims to determine whether a significant association exists between genotype and change in intelligence after relaxation of diet. Methods—125 patients with hyperphenylalaninaemia and phenylketonuria whose diet was relaxed after 8 years of age. Verbal, performance, and full scale intelligence quotients at 8, 14, and 18 years were expressed as standard deviation scores (IQ-SDS), and genotype as predicted residual enzyme activity (PRA) of phenylalanine hydroxylase. Results—IQ-SDS at 8, 14, and 18 years were significantly below normal; no association was found between PRA and IQ-SDS. Significant reductions in verbal and full scale IQ-SDS occurred between 8 and 14 years and 8 and 18 years. There was a significant association between PRA and the reduction in verbal, performance, and full scale IQ between these years. Multiple regression analysis of 18 year results, using 8 year results as covariates, supported the association between PRA and IQ-SDS; after adjustment for phenylalanine control, both up to and after the age of 8 years, the full scale IQ-SDS at 14 and 18 years was 0.15 higher for each 10% increase in PRA. Conclusions—Genotype might be useful in predicting the likelihood of intellectual change in patients with hyperphenylalaninaemia and phenylketonuria whose diet is relaxed after the age of 8 years. (Arch Dis Child 2000;82:216‐221)

Tetrahydrobiopterin (BH4) deficiency is a rare cause of hyperphenylalaninaemia (HPA) and usually leads to progressive neurological deterioration despite early dietary control of plasma phenylalanine concentrations. Dihydropteridine reductase (DHPR) deficiency is the most severe cause with respect to a fatal outcome. We report a 7-year-old girl with HPA diagnosed on neonatal Guthrie screening who at the age of 6 months had cytotoxic therapy for an adrenal neuroblastoma which secreted catecholamines. When 4 years old she was found to have DHPR deficiency. Although developmentally retarded and microcephalic she has failed to develop the florid neurological features often associated with the condition.

Trabecular bone mineral content was assessed by quantitative computed tomography in eleven young adults with phenylketonuria who had been treated from early childhood with a diet restricted in natural protein and supplemented with amino acids, minerals and vitamins. There was a significant reduction in the bone mineral content of patients compared with the normal population. Prospective studies are indicated in younger patients to ensure optimum bone mineralisation is achieved by adulthood.

Experimental result are presented for the effect of water injection on fuel economy and ignition delay and on exhaust emissions of smoke, CO, NO and HC for a direct injection diesel engine. Results are given for a range of water/fuel ratios and for three methods of water injection. Compared with fuel injection only, NO is reduced by up to 70% by using water injection in the air inlet or with the fuel. But while the former method increases smoke and CO, the latter method reduces CO and smoke by up to 50% together with small improvements in specific fuel consumption. However due to an increase of HC beyond a water/fuel ratio of 0.6 the NO reduction would be limited to 50% when injecting water with the fuel, though this stituation could be improved by increasing the engine compression ratio. The results obtained by the authors are compared with those available in the literature. Experimental data are presented on droplet size distributions for water, fuel and all spray droplets and there is a change in the state of the water/fuel spray for water/fuel ratios greater than 0.2. Also a previously developed computer model of the diesel combutions process is used to predict the effect of water injection on NO, smoke and fuel economy. The calculations over-estimate some of the trends but show that, in addition to the thermal effect of water injection, water injection affects the rates of air entrainment and fuel/air mixing. In particular, water injected with the fuel is an additional source of injected momentum for fuel/air mixing.

An analytical technique has been optimised for the measurement of the concentrations of diesel exhaust odorants. Application of this technique to combustion bomb studies shows that preflame reactions with diesel fuel produce high concentrations of odorants. The effects of engine variables on exhaust odorant concentrations are presented for direct and indirect injection engines. Analysis of these data shows that diesel exhaust odorants are produced from three sources: (a) the fuel-lean mixture produced during the ignition delay period, (b) fuel emptying from the nozzle sac volume of direct injection engines after injection, (c) a fuel-rich source which becomes significant at high load. The practical measures for control of odorants are outlined.

We report five cases of peptic ulceration in patients with classical phenylketonuria and suggest that there may be a causal relationship between the two conditions.

Fuels of widely varying properties are studied by injection of a single and well defined spray into an experimental diesel engine. Three optical techniques were developed to visualise liquid fuel, fuel vapour, flame, soot and individual droplets and their associated vapour trails. Liquid core length measurements are presented for diesel fuel, toluene, ethanol and sunflower oil. Computer model predictions show that an increase of the fuel mid-boiling point by 40/sup 0/C gives a similar effect on liquid core length to an increase of 0.03mm in the nozzle hole diameter.