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OBJECTIVEThe overall goal of this study was to develop an image-guided spinal stereotactic setup for intraoperative intraspinal microstimulation (ISMS). System requirements were as follows: 1) ability to place implants in various segments of the spinal cord, targeting the gray matter with a < 0.5-mm error; 2) modularity; and 3) compatibility with standard surgical tools.METHODSA spine-mounted stereotactic system was developed, optimized, and tested in pigs. The system consists of a platform supporting a micromanipulator with 6 degrees of freedom. It is modular and flexible in design and can be applied to various regions of the spine. An intraoperative ultrasound imaging technique was also developed and assessed for guidance of electrode alignment prior to and after electrode insertion into the spinal cord. Performance of the ultrasound-guided stereotactic system was assessed both in pigs (1 live and 6 fresh cadaveric pigs) and on the bench using four gelatin-based surrogate spinal cords. Pig experiments were conducted to evaluate the performance of ultrasound imaging in aligning the electrode trajectory using three techniques and under two conditions. Benchtop experiments were performed to assess the performance of ultrasound-guided targeting more directly. These experiments were used to quantify the accuracy of electrode alignment as well as assess the accuracy of the implantation depth and the error in spatial targeting within the gray matter of the spinal cord. As proof of concept, an intraoperative ISMS experiment was also conducted in an additional live pig using the stereotactic system, and the resulting movements and electromyographic responses were recorded.RESULTSThe stereotactic system was quick to set up (< 10 minutes) and provided sufficient stability and range of motion to reach the ISMS targets reliably in the pigs. Transverse ultrasound images with the probe angled at 25°–45° provided acceptable contrast between the gray and white matter of the spinal cord. In pigs, the largest electrode alignment error using ultrasound guidance, relative to the minor axis of the spinal cord, was ≤ 3.57° (upper bound of the 95% confidence interval). The targeting error with ultrasound guidance in bench testing for targets 4 mm deep into the surrogate spinal cords was 0.2 ± 0.02 mm (mean ± standard deviation).CONCLUSIONSThe authors developed and evaluated an ultrasound-guided spinal stereotactic system for precise insertion of intraspinal implants. The system is compatible with existing spinal instrumentation. Intraoperative ultrasound imaging of the spinal cord aids in alignment of the implants before insertion and provides feedback during and after implantation. The ability of ultrasound imaging to distinguish between spinal cord gray and white matter also improves confidence in the localization of targets within the gray matter. This system would be suitable for accurate guidance of intraspinal electrodes and drug or cell injections.

Between 2010 and 2011, an arterial road was constructed within provincially significant wetlands in the South March Highlands (SMH) located in Ottawa, Ontario, Canada. The wetlands and adjacent upland areas were determined to be sensitive habitat for Blanding’s Turtles (Emydoidea blandingii (Holbrook, 1838)) during the approval and permitting process, and a population study was required as part of the road construction project. The study consisted of a 4-year mark–recapture program and a movement study of radio-tagged adult turtles. General findings included the identification of 27 adult males and 55 females and a population estimate of 93 adults (95% Cl: 86–118). A 1:2.32 male to female sex bias was also found. Mean home-range size was 19.06 ha and tagged turtles moved, on average, more per observation in 2013 (191.40 m compared with 89.75 and 123.04 m in 2011 and 2012, respectively). Previously reported differences in movement patterns between males, females, and gravid females were not observed. The SMH Blanding’s Turtle population should be closely monitored because urban development continues in the area, which may further reduce the population size. Understanding the biology of imperiled populations across species’ ranges is necessary to promote conservation and adaptive wildlife management.

Existing methods for predicting heat fluxes and temperatures in internal combustion engines, which take the form of correlations to estimate the heat transfer coefficient on the gas-side of the combustion chamber, are based on methodology developed over the past 50 years, often updated in view of more recent experimental data. The application of these methods to modern diesels engines is questionable because key technologies found in current engines did not exist or were not widely used when those methods were developed. Examples of such technologies include: high-pressure common rail and variable fuel injection strategies including retarded injection for nitrogen oxides emission control; exhaust gas re-circulation; high levels of intake boost pressure provided by a single- or double-stage turbocharger and inter-cooling; multiple valves per cylinder and lower swirl; and advanced engine management systems. This suggests a need for improved predicting tools of thermal conditions, specifically temperature and heat flux profiles in the engine block and cylinder head. In this paper a modified correlation to predict the gas-side heat transfer coefficient in diesel engines is presented. The equation proposed is a simple relationship between Nu and Re calibrated to predict the instantaneous spatially averaged heat transfer coefficient at several operating conditions using air as gas in the model. It was derived from the analysis of experimental data obtained in a modern diesel engine and is supported by a research methodology comprising the application of thermodynamic principles and fundamental equations of heat transfer. The results showed that the new correlation adequately predicted the instantaneous coefficient throughout the operating cycle of a high-speed diesel engine. It also estimated the corresponding cycle-averaged heat transfer coefficient within 10 per cent of the experimental value for the operating conditions considered in the analysis.

Over the last 40 years, several empirical correlations have been developed to estimate heat fluxes from the combustion chambers of internal combustion engines. Some of these expressions are based on correlations to compute the Nusselt number for forced convection in turbulent flow inside circular tubes. The fundamental suitability of this kind of empirical model in representing the highly complex processes of in-cylinder heat transfer is questionable, but in practice the models have steadily improved owing to contributions from numerous investigators. Other correlations have a less theoretical basis than those of the Nusselt number form. Formulae of this type have been obtained from the application of simple statistical techniques to large datasets, taking into account several engine operational parameters and engine types. The resulting correlations provide reasonable estimates but perform poorly when extrapolated or applied to novel concepts. In this paper, the most important correlations are reviewed against the features of a modern diesel engine, and research requirements for future modelling developments are identified and discussed.

A detailed programme of work has been undertaken to quantify the suitability of predictive methods for accurate determination of the levels of boiling heat transfer within an internal combustion (IC) engine cooling gallery simulator. An extensive array of experimental data has been obtained as the basis for the predictive validation. Working on the principle of superposition, the convective component of heat transfer has been represented by the established Dittus-Boelter correlation which has been extensively modified to account for developing boundary layers, surface roughness and nearwall viscous effects. The boiling component has been represented by the Chen model, modified for binary fluids and subcooling. For the IC engine cooling application it is concluded that the application of the Chen approach must be complemented by a convective heat transfer model that accurately represents the complex thermo-fluid situation being experienced within a developing flow.

Simple heat transfer correlations are known to underpredict the single-phase convective heat transfer coefficient when applied to internal combustion (IC) engine cooling passages. The reasons for such underprediction were investigated using a specially designed test rig which was operated under a wide variety of test conditions relevant to IC engine operation. Data from this rig study identified that undeveloped flow (fluid dynamically and thermally), surface roughness and fluid viscosity variation with temperature were the physical reasons responsible for the mismatch. Simple empirical heat transfer models have subsequently been extended to take account of these factors and are shown to give much improved correlation with rig data, and data from an engine study. The implications of this work for predicting engine heat transfer in a three-dimensional computational fluid dynamics environment are discussed.

A steady state test procedure has been developed and implemented on an extensively instrumented production diesel engine to estimate the total energy transfer to coolant over a New European Drive Cycle. The test procedure involved segmenting the drive cycle into 26 operating conditions, each with a corresponding weighting factor. The test program consisted of both the steady state tests and a series of transient tests for comparison. The engine instrumentation consisted of a bespoke measurement device to calculate the rate of heat transfer through the combustion chamber walls. The sensors were located vertically down both the inlet and exhaust sides of one cylinder. It was found that the steady state approximation method estimated the total energy transfer to the coolant to within 10% of the transient tests. Differences in the idle speed condition were found to have the largest effect due to 21.7% of the drive cycle occurring at this condition. The steady state approximation method can therefore be used to sufficiently estimate the drive cycle performance for energy transfer if an exact condition is used for a region where the weighting factor is significant, i.e. greater than 15%. Subsequently it could also be used for other parameters, such as fuel consumption.

A modern high speed four cylinder Diesel engine equipped with high pressure common rail fuel injection equipment has been fitted with extensive instrumentation to allow the heat flux and coolant convective heat transfer coefficient through the cylinder walls to be estimated. The instrumentation was located around the circumference of the cylinder and longitudinally down the cylinder. The engine has been run through the new European drive cycle using a dynamic test stand. From the experimental results it was found that there was a strong correlation between the one dimensional heat flux through the cylinder wall and the engine speed. The changes in heat flux were found to be repeatable over the four repeated ECE sections of the drive cycle. It was also found that the magnitude of heat flux reduced down the length of the cylinder.

A simple model from first principles has been developed to estimate the heat transferred from the piston rings and skirt to the cylinder wall. The model considers the various forms in which heat is transferred from the combustion gases to the containing walls, namely, convection and radiation between the gases and wall surface, and conduction from piston rings and skirt through the oil film. The model also includes frictional heat generation by the rings and skirt as a result of the piston movement. Results presented in this paper show that the heat flux predicted by the model on the thrust side of the bore, at an engine speed of 4000 rpm and engine load of 100% of the limiting torque, was generally of the same order of magnitude as the heat flux estimated from experimental measurements. They also demonstrated that in the process of heat transfer from combustion gases to the cylinder wall, convection and radiation of heat have their greatest influence on the total heat flux in the top section of the cylinder bore and provide a contribution of approximately 25% over the rest of the stroke. However, the distribution of heat flux in the middle and bottom parts of the stroke shows that the main mechanism of heat transfer is conduction from the piston assembly.

In the last 15 years, diesel engines in passenger cars have evolved rapidly. The combination of performance, fuel consumption, emissions and refinement offered by a modern diesel engine makes it the preferred engine choice in many sectors of the market. The enormous progress made has resulted from technological improvements such as low swirl 4-valve per cylinder, direct injection combustion systems complemented by high pressure common rail fuel systems and high levels of turbocharger boost pressure. The durability and output potential of such engines is strongly linked to the operating temperature of certain key components. Accurate temperature predictions are an essential pre-requisite to the continuing evolution, thus placing emphasis on the need for high quality predictive tools. Despite this, existing methods for predicting heat flux and component operating temperatures in diesel engines rest mainly with methodology developed over 50 years ago, often updated in the light of more recent experimental data. It is questionable how well those methods represent modern diesel engines. In order to look at this issue, the authors have undertaken a wide-ranging experimental and analytical study using a highly instrumented modern diesel engine. The engine had 109 thermocouples implanted into the walls of the cylinders and cylinder head to reveal the spatial variation of temperature and heat flux over a wide range of operating conditions. In this paper some of the results of the study are discussed, together with comparisons of experimental data and the existing predictive models. Areas of agreement and discrepancy are highlighted in the context of the operating conditions and engine characteristics, and proposals for improved methodology are discussed.