Dr. Kuldeep Singh | University of Nottingham (original) (raw)

Uploads

Papers by Dr. Kuldeep Singh

Volume 2C: Turbomachinery, 2020

In the case of aero-engine, thin lubricating film servers dual purpose of lubrication and cooling... more In the case of aero-engine, thin lubricating film servers dual purpose of lubrication and cooling. Prediction of dry patches or lubricant starved region in bearing or bearing chambers are required for safe operation of these components. In the present work thin liquid film flow is numerically investigated using the framework of the Eulerian thin film model (ETFM) for conditions which exhibit partial wetting phenomenon. This model includes a parameter that requires adjustment to account for the dynamic contact angle. Two different experimental data sets have been used for comparisons against simulations, which cover a wide range of operating conditions including varying the flow rate, inclination angle, contact angle, and liquid-gas surface tension coefficient. A new expression for the model parameter has been proposed and calibrated based on the simulated cases. This is employed to predict film thickness on a bearing chamber which is subjected to a complex multiphase flow. From this...

Polyethersulfone (PES) composites were developed with carbon fabric (CF). Cold remote nitrogen ox... more Polyethersulfone (PES) composites were developed with carbon fabric (CF). Cold remote nitrogen oxygen plasma (CRNOP) treatment was employed to the CF to incorporate functional groups and promote fiber– matrix adhesion. This study includes the effect of PES melt flow index (MFI) on the wettability of CF and its influence on fretting wear performance. Evaluations of fretting wear properties of composites led to the conclusion that the CRNOP treatment proved beneficial to enhance performance properties significantly. Polymer MFI and treatment to CF proved to be the decisive parameters for controlling performance of composites apart from operating parameters. Perforations on the treated carbon fiber, evidently observed by FESEM, improved the fiber–matrix adhesion, and hence the performance properties. Artificial neuron network (ANN) was used for prediction of the wear behavior of composites.

The conventional forward injection for film cooling with cylindrical holes, where the axial compo... more The conventional forward injection for film cooling with cylindrical holes, where the axial component of the coolant velocity is aligned with mainstream flow direction creates kidney vortices. This results in quick mixing of the coolant with the mainstream. The conventional anti-kidney vortices cooling holes require shaping or branching which adds to the cost and complexity of the system. In this paper, reverse/ backward injection is proposed to improve film cooling. In the case of reverse/backward injection the secondary air is injected such that its axial velocity component is in the reverse direction to that of the mainstream. Film cooling is studied experimentally and numerically on a flat plate with forward and reverse injection. The injection angle of the cooling hole is varied from 30 to 60 in both forward and reverse directions at five blowing ratios ranging from 0.25 to 3.0 at a fixed density ratio of 0.91. The length to diameter ratio of the cooling hole is kept at 5 and the mainstream Reynolds number is maintained at 3.75 Â 10 5. Film cooling effectiveness obtained with the reverse holes is found to be much higher than that of the forward holes. Improvement in the area weighted average values of film cooling effectiveness for blowing ratio, M ¼ 1 is 170%, 78% and 186% for injection angles 30 , 45 and 60 respectively. Coefficient of discharge obtained from reverse injection is found to be smaller than that of forward injection. The film cooling effectiveness in the case of reverse injection is found to be less sensitive to the injection angle.

Film cooling is widely used to protect surfaces exposed to gases at a high temperature in gas tur... more Film cooling is widely used to protect surfaces exposed to gases at a high temperature in gas turbine engines. Film heating is the reverse of film cooling, where hot secondary fluid is injected onto the walls to protect against a relatively cold mainstream. In the literature, the latter has often been used as an experimental analogue of the former, since mainstream flow rates are substantially higher, and it is relatively simpler to heat the smaller stream of secondary fluid for experiments. In this paper, the results obtained from a numerical study of film cooling and film heating over a flat plate through single-slot injection are presented. Since the objective of the work is to evaluate the suitability of film heating as a proxy for film cooling, it was decided to keep computational simple, using two-dimensional simulations. The effect of a density ratio of injectant-to-mainstream in the range of 0.2–5 is studied numerically to cover film heating and film cooling. Numerical simulations were carried out for three blowing ratios, M ¼ 1, 2, and 3 at a fixed mainstream Reynolds number of 1.5 � 10 5 for three injection angles, 30°, 45°, and 60°. Numerical simulations were also carried out for a wide range of momentum flux ratio for film heating and film cooling at an injection angle of 30°. The results show that film heating and film cooling are not equivalent, especially when the density ratio deviates from unity substantially. Based on numerical study, it appears possible to predict film cooling effectiveness from film heating effectiveness for a wide range of density ratios, even though the effectiveness values obtained in regard to film cooling and film heating differ significantly.

In this article, the results obtained from a detailed numerical investigation of 2D film cooling ... more In this article, the results obtained from a detailed numerical investigation of 2D film cooling over a flat plate through single-slot injection are presented. The effects of mainstream Reynolds number, blowing ratio, density ratio, and injection angle on the effectiveness of film cooling were investigated in the present work. Numerical simulations were carried over a wide range of density ratio ranging from 1.1 to 5 at two mainstream Reynolds numbers (8 Â 10 4 and 1.5 Â 10 5), three blowing ratios (ranging from 1 to 3), and six injection angles (ranging from 15 to 90). The results show that at lower injection angles of 15 –45 , maximum film-cooling effectiveness occurs at a particular value of velocity ratio which is found to be independent of mainstream Reynolds number, blowing ratio, and density ratio. Based on a combined effect analysis of blowing ratio, density ratio, and injection angle, a relation was obtained for velocity ratio that gives an optimum film-cooling effectiveness.

—In the present study, the effect of radiative heat transfer on film cooling effectiveness is stu... more —In the present study, the effect of radiative heat transfer on film cooling effectiveness is studied. The experiments were conducted at a density ratio of 0.84, blowing ratio, M = 1, injection angle, α = 30° and mainstream Reynolds no. 2×10 5 with the objective to validate computational methodology. A systematic numerical study is carried out at the temperatures in the range of operating temperature of the modern gas turbines. The results obtained from this study showed that film cooling effectiveness is adversely affected by radiative heat transfer. The maximum 83°C rise in the lateral average temperature was observed due to consideration of radiative heat transfer at the mainstream to secondary fluid density ratio of 4 and blowing ratio of 1.

D Hole diameter, m M Blowing ratio, ρ sec U sec ρ ms U ms , non-dimensional P Hole spacing in lat... more D Hole diameter, m M Blowing ratio, ρ sec U sec ρ ms U ms , non-dimensional P Hole spacing in lateral direction, m Re Reynolds number based on mainstream flow, ρU ms µ t Thickness of test plate, m T Absolute temperature, K TR Temperature ratio, T ms

Cold remote oxygen nitrogen plasma (CRNOP) treatment was used to enhance reactivity of carbon fab... more Cold remote oxygen nitrogen plasma (CRNOP) treatment was used to enhance reactivity of carbon fabric (CF) towards PEEK. The composite with treated fibers exhibited significantly better mechanical properties due to enhanced fiber–matrix adhesion as evidenced from SEM studies. It was of interest to examine the effect of the treatment on erosive wear performance with variation in angle of impingement and under elevated temperatures. The treatment proved successful in imparting wear resistance to the composite as compared to that with untreated CF. Efforts were made to study correlation between mechanical properties and erosive wear behavior at high temperature. Micro-Raman spectroscopy (MRS) was used to analyze the effect CRNOP treatment on CF and also to study stresses introduced during the erosion of CF-PEEK composites at different angles of impingement. Fairly good correlation was observed in wear rate and strain produced on the surfaces of fibers. SEM was used to understand wear mechanisms.

Film cooling is investigated on the corrugated surfaces. Film cooling behavior of corrugated surf... more Film cooling is investigated on the corrugated surfaces. Film cooling behavior of corrugated surface is not similar to flat plate. Effect of blowing ratio and density ratio is profound on corrugated surface. Injection angle plays an important role even for corrugated surface. a b s t r a c t In this paper the procedure to arrive at a suitable film cooling configuration of an aero engine afterburner liner is discussed. Numerical studies are carried out to select (i) locations of film cooling holes, axial pitch, transverse pitch and hole size on corrugated liner. Numerical studies are extended to investigate the influence of various operating parameters such as mainstream Reynolds number, blowing ratio and density. In the numerical study mainstream Reynolds number is varied from 10 Â 10 3 to 4.5 Â 10 5 , blowing ratio is varied from 0.8 to 3 and density ratio is varied from 1.8 to 5. Effect of coolant injection angle is also studied by varying injection from 45° to 90°. Experimental studies are conducted on the corrugated surface to validate the computational methodology. The parameters considered in the experimental study are: the mainstream Reynolds number of 2 Â 10 5 , blowing ratio of 1.8 and density ratio of 0.91. It is found from the current study that the film cooling behavior on a corrugated surface is different from that on flat surfaces. Film cooling effectiveness increases with increase in mainstream Reynolds number upto 3.79 Â 10 5 and thereafter it decreases slightly. Blowing ratio and density ratio have significant impact on the film cooling. Film cooling effectiveness increases with the increase in the blowing ratio even at very high blowing ratios. It is also observed that the film cooling effectiveness drastically decreases as injection angle is increased from 45° to 90°.

A detailed numerical study on the film cooling of a corrugated surface through a single slot has ... more A detailed numerical study on the film cooling of a corrugated surface through a single slot has been presented in this paper. The effects of the blowing ratio, density ratio (DR), and injection angle on the film cooling of the corrugated surface are discussed. Numerical simulations are carried out over a wide range of DRs ranging from 0.2 to 5.0 at a fixed mainstream Reynolds number of 1.5 � 105, three blowing ratios of 1, 2, and 3, and five injection angles ranging from 30° to 90°. Results show that the velocity profile on a corrugated surface is strongly influenced by the injection of the secondary fluid. It is observed that the film cooling effectiveness of the corrugated surface increases monotonically with an increase in the blowing ratio. The density ratio and injection angle also have a strong influence on the film cooling.

Volume 2C: Turbomachinery, 2020