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Investigations into lubricating oil degradation and engine wear were carried out during the course of this work. Lubricating oil degradation models were studied and verified. This study has resulted in the development of an integrated, miniaturised, automated oil analysis system for the determination of water content, Total Base Number and Total Insoluble Matter for new and used oils. The study on the engine wear and oil degradation was based on two air- cooled Petter AA1, single cylinder engines running on a 1% sulphur diesel fuel and a minimum military specification oil (OMD 75). The results obtained indicated that the combination of engine operating conditions, diesel fuel and lubricating oil used, resulted in the premature loss of oil consumption control due to severe bore polish which was caused by corrosive wear. Oil analysis methods were developed requiring minimal quantities of oil sample in order not to disturb the engine/lubricating oil system integrity. The oil analysis methods developed were automated into a single integrated instrument for the determination of water content, Total Base Number and Total Insoluble Matter for new and used oils using 1gram (or less) of oil sample and with analysis times in the region of three minutes for doing all three analysis. A detailed study into new and used formulated oil chemistry revealed that the measurement of Total Base Number as determined by the Institute of Petroleum standard test methods (IP 177 and IP 276) provided information that were overestimates of the true levels of basicity of the oil. A new technique, based on the same chemistry as the original (IP) method, was developed for the Total Base Number determination with improved end-point detection for not only new oils, but more importantly for used oils as well. Other oil analysis data obtained during this study revealed the need to modernise the existing Industry test methods with regard to chemistry, equipment and functionality, for example Total Acid Number determination. The data obtained from the analysis of the used oil was studied and the rates of change of each of the measured parameters were calculated, based on the Quasi-Continuous Stirred Tank Reactor model. The data obtained from this model was compared to . two previously proposed models which indicated that the QCSTR model is a better model for representing the degradation of lubricating oils in running engines. This work has shown the need for the trapping of oil from the top-ring zone to understand the nature of the degradation and interaction of this oil with that (bulk) oil in the sump in order to successfully model the degradation characteristics of the oil.

A digital computer model of a diesel engine and load is developed which takes into account in cycle calculations the input temperature and pressure, mass of fuel injected, angle of injection, and cylinder temperature and pressure, and gives as outputs the average torque and speed. A typical heat release curve from a practical engine test is used with ignition delay considered constant in time. Results from the program are validated by comparison with data taken from laboratory engine tests. This model is subsequently linearized to obtain the transfer function matrix relating input manifold pressure, mass of fuel injected, and angle of advance to output torque and speed. The design of a feedback controller is then investigated using pole and zero placement techniques, the system inputs and outputs being demanded and achieved torque and speed .

This study is aimed at understanding the effects of changing the upstream nozzle geometry on the development of rectangular free jets. An existing converging rectangular nozzle with an exit aspect ratio of 4 and a circular inlet (AR4 nozzle) has been used as the basic configuration for this work. The study is primarily based on the results of numerical simulations wherein the internal geometry variation is accomplished by changing the inlet aspect ratio (AR,) and the length of the converging section, expressed as a ratio with respect to the length of the nozzle (called 'converging section ratio*, CSR); all the other parameters are kept constant. The results from LDA experiments done on the AR4 nozzle are presented and used as validation data for the CPD simulations. Analyses of the numerical results help in understanding the variation of the jet spreading for different combinations of AR, and CSR. Two parameters are identified for describing the jet development: the cross-over point (XC), defined as the location downstream of the exit where the jet half-velocity-widths (B) along the major and minor axes are equal, and the difference in the half-velocity-widths at 30 nozzle equivalent diameters (Dm) from the exit (AB30), to ascertain the occurrence of axis-switching. For a given AR, XC varies linearly with CSR; the variation of XC is non-linear with AR, for a constant CSR. The A1330 variation is non-linear with both AR, and CSR; the other variable being kept constant. The data obtained from the simulations are further used to propose two parametric models which can be used to predict the occurrence of axis-switching, within the scope of this work. The parametric models are validated and future work is proposed.

Approved for public release, distribution unlimited / Steam leakage from an aircraft carrier catapult is sometimes ingested by the aircraft's engines upon launch which may induce compressor stall. Investigation of the phenomenon known as a "pop stall" is of particular importance as the Navy prepares to field the F35C, the aircraft carrier variant of the joint strike fighter. The single engine design of the F-35C makes this aircraft particularly susceptible to steam-induced stall during catapult launch. The present project examined compressor stall and included steady-state as well as transient measurements in the inlet of a transonic compressor prior to and during a steaminduced stall. Hotwire measurements of the inlet flow field were taken to determine an inlet turbulence intensity of 2-3% during both subsonic as well as transonic compressor operation. A 95% speed line was established from data taken from open throttle to near stall. Hot-film and Kulite pressure data taken near stall showed the existence of a stall precursor which appeared near half rotor speed. Steam was injected into the inlet; however the initial method added mass to the system and did not induce a stall. A decrease in the amplitude of the pressure trace was observed however. A stall was induced by steam ingestion ahead of the existing inlet throttle, with upstream transient measurements taken using both hot-film and Kulite pressure transducers.

CIVINS / This thesis examines the use of Non-intrusive Load Monitoring (NILM) in auxiliary shipboard systems, such as a low pressure air system, to determine the state of equipment in larger connected systems, such as the main propulsion engines. Using data collected on previously installed NILM's at the Naval Surface Warfare Center, Philadelphia DDG-51 Land Based Engineering Site (LBES), major event changes were analyzed and diagnosed using power data collected from the in-service low pressure air compressor (LPAC) and the in-service fuel oil pump. Events investigated include main propulsion engine starts and loadings, gas turbine generators starts, major electrical load shifts, and leak insertions into the low pressure air system. An additional NILM was installed on the General Electric LM2500 Universal Engine Controller (UEC) in order to assist in the diagnosis of various state changes. The UEC provides the appropriate interfaces to monitor and control each LM2500 GTM. The UEC controls the application of starter air, ignition power, and fuel to the engine while also receiving feedback of engine parameters from sensors on the engine. Using the combined data received by the LPAC, fuel oil pump, and UEC, a diagnosis system is derived that can detect major events in the engineering plant described above. / CIVINS / US Navy (USN) author

Most high speed vessels are fitted with powerful high speed engines which are installed in confined spacesa nd, as a consequencec, ausea n extremely high level of noise and vibration. Often structure-borne sound power is transmitted to a sound carrying structure from a source via a number of contact points. In turn, the noise and vibration are propagated in the structure and could possibly cause an undesired noise radiation. In this study, a model for predicting power flow based on the mobility theory has been addressed. The unique parts of the study include the establishment of the relationship of mobility functions with respect to four-pole parameters and the dynamic stiffness coefficients of a coupled machine/mount/foundation system. Also expressions to represent the sound input power, the output power and the transmitted power in relation to mobility functions are clarified. From a detailed analysis of relevant literature, it is shown that no validated models for predicting the propagation of structure-bome noise within the intermediate frequency range of 125 Hz to lkHz exist. As a consequence, a new numerical stress wave model has been developed to bridge this knowledge gap. This innovative approach extends the earlier works of Cremer, Heckl and Ungar in the field of stress wave propagation. Finally, a novel holistic model has been developed to line up the transmission, propagation and radiation predictions of a machine induced noise and vibration in ship's structure to take in account the fluid-structure interaction effect. A number of experiment measurements have been performed to validate the established models. From the comparisons, the prediction models are shown to be credible with an accuracy higher than 95 per cent. The established models are of a generic nature and can be applicable to diverse engineering fields regarding to the predictions of structure-borne noise and vibration transmission, propagation and radiation. Applications of these models to characterize the vibration reduction countermeasures,a s in the case of resilient mounts and squeeze-film damping plates, from a machine are also discussed.

An investigation was carried out to study the process of rotating stall inception in a low hub-tip ratio fan. Such fans are expected, based on an elementary analysis, to stall from the root. However, experimental evidence had led to the belief that the fans stalled from the tip. The effects of streamtube contraction were first studied and this was followed by an experimental investigation on an isolated rotor, with successive build modifications to increase the likelihood of rotating stall inception occurring at the root. A computer based streamline curvature method was used to study the effects of streamtube contraction and streamtube diffusion that commonly occur when a fan is operated at flows below its' design flow rate. The results indicated a reduced expectation for the root to stall first when compared to a simple 2-D flow analysis. Experimental measurements were then carried out to determine how the experimental local characteristics differed from the predicted characteristics. It was apparent that real fluid effects tended to steepen the root characteristic, thus enhancing the stability of the root. The tip characteristics tended to droop and become less stable. The enhancement of the root stability was also seen in the profiles of deviation angle. The axial Velocity contours at the rotor exit supported the conclusion that the root stability enhancement was caused by "centrifuging". To determine the actual radial location of rotating stall inception, an array of hot wires was used to record events during the inception transient. Inception was first detectable at the tip. This tip stalling behaviour persisted for all the build modifications. Measurements of unsteady pressure were also made to study the movement of the overall operating point since it was felt that this could continuously alternate between a pair of closely spaced characteristics. The results indicated that the fan operated along a unique characteristic. The overall conclusion was that a low hub-tip ratio fan shows a strong reluctance to stall at the root due to "centrifuging" of the blade boundary layer. The inception process appears to be dominated by events in the tip region.

An experimental and theoretical study of erosion in centrifugal compressor impellers is presented. An experimental rig using laser anemometry techniques was employed to create a database of particle restitution ratios for a range of materials. This data was unique in that the particle rebound was measured in a quiescent condition where the aerodynamic effects had been minimised, and also parametric factors not previously available were included. These values were incorporated into the existing Particle Trajectory Code developed by Cranfield University and Rolls Royce PLC. The code is used to calculate the trajectories of discrete particles in three dimensional gas turbine geometries, and the ensuing erosion. It was modified to include the effects of the periodic boundary conditions, particle fragmentation, splitter blades, and variations in inlet dust concentration profile. Flowfield calculations were performed on a Rolls Royce GEM-2 and splittered GEM-60 impeller, which both represent the high pressure stage of the axial + centrifugal compression system of GEM engines. A procedure developed by Tourlidakis, for the analysis of steady viscous flow in high speed centrifugal compressors with tip leakage, was used to generate the flowfields. The GEM-2 impeller flowfield was analysed at 1009c speed, and validated with calculations and measurements which had been taken for previous projects. Simulated erosion data under the same conditions was checked using practical results obtained in a Rolls Royce PLC Helicopter Engine Environmental Protection Programme, and good agreement was achieved. In order to provide a qualitative, experimental assessment of erosion, a GEM-60 impeller was coated with four layers of paint of different colours. Two sizes of quartz particle, each at three different vane heights, were then seeded into the impeller while it was run cold at (the maximum) 70% speed. The erosion patterns generated compared well with the results generated by the Particle Trajectory Code.