Papers by Quamber Nagpurwala
Numerical Studies on the Effect of Cooling Vent Setting and Solar Radiation on Air Flow and Temperature Distribution in a Passenger Car
SAE Technical Paper Series, 2009
Abstract: Owing to the dynamic life style, considerable time is spent in traveling. Consequently,... more Abstract: Owing to the dynamic life style, considerable time is spent in traveling. Consequently, the demand for thermal comfort of passengers in vehicles has increased. And, to provide thermal comfort, the vehicles are equipped with Heating, Ventilation and ...
Owing to adverse pressure gradient in an axial compressor, the blade surface boundary layers beco... more Owing to adverse pressure gradient in an axial compressor, the blade surface boundary layers become thicker and are prone to separation. Boundary layer suction technique has been widely investigated to reduce the boundary layer growth on compressor blades. However, most of the research is limited to low Mach number compressor cascades. In the present study, aspiration, or blade boundary layer suction, has been numerically investigated on a high inlet Mach number, high deflection linear compressor cascade. The cascade comprised the stator blade mean section of the NASA 37 transonic compressor stage. Aspiration or suction slots were introduced on the blade suction surface and CFD simulations were carried out for two cases of single suction slot at two different chordwise positions and one case with the two suction slots together. Studies were undertaken for two different suction mass flow rates at design and off-design incidence angles. The density based implicit solver of the commerc...
Casing treatment, or incorporation of slotted casing around the rotor, is one of the few techniqu... more Casing treatment, or incorporation of slotted casing around the rotor, is one of the few techniques to delay the inception of flow instability such as rotating stall, thus enhancing the operating range of an axial compressor. However, the improvement in stall margin through casing treatment is accompanied by a penalty of reduction in compressor efficiency. Several studies have been carried out to optimise the casing treatment configurations in terms of global compressor performance parameters, but there is no clear understanding of the flow physics, which brings about the changes in the compressor performance and stalling behaviour. Further, a given casing treatment configuration may not yield the same results for all compressor builds. This paper deals with the numerical studies on the effect of slotted casing treatment, having axial and radial skews of 15° and 45° respectively, on the overall performance and stall margin of a transonic compressor rotor. The steady state CFD simula...
Experimental Investigation on Errors in Wall Static Pressure Measurement-Case of Projected or Recessed Pressure Plugs
Centrifugal compressors are designed for a given operating pressure and mass flow rate. But often... more Centrifugal compressors are designed for a given operating pressure and mass flow rate. But often these machines are required to be run at various off design operating conditions. The need to maintain reasonably high efficiency under off design conditions with acceptable stall margin makes the compressor design more challenging. These requirements call for improvemnet in the flow quality through the impeller by incorporating suitable changes in the vane shape. This paper examines the effect of introducing tangential skew near the trailing end of a high pressure ratio centrifugal compressor impeller. The blade skew was introduced in such a way that the blade angle distribution varied from hub to shroud near the trailing end only. Detailed, steady state, numerical simulations were carried out on the compressor, using a commercially available code, FLUENT. Results of the baseline CFD analysis on the original impeller were validated through comparison with the available experimental dat...
Effect of Chordwise Location of Full Span Gurney Flap on Aerodynamic Performance of a Transonic Axial Compressor Rotor
The present day quest to develop compact gas turbine engines for aero propulsion and power genera... more The present day quest to develop compact gas turbine engines for aero propulsion and power generation requires axial compressors with high blade loading and wider stable operating range. High blade loading gives high pressure ratio per stage and consequently a multistage compressor module with reduced number of stages. Stage pressure ratio can be increased by increasing the rotor tip speed, but this approach is limited by considerations of rotor dynamics and mechanical integrity. Hence, to increase the rotor total pressure ratio, the designers are exploring other options such as new aerofoil shapes with reduced aerodynamic losses and aerofoils with add-on features to increase the fluid deflection across the blade row. In this regard, the use of Gurney flap (GF) on the trailing edge of an aerofoil is found quite promising for enhancing the aerodynamic lift [1]. The published research has established effectiveness of GF not only in aircraft wings [2, 3] but also in wind turbine blades...
Numerical Studies on the Effect of Impeller Cone Angle on Aerodynamic Performance of Mixed Flow Compressors
A centrifugal compressor, with backward swept impeller, was designed for industrial applications ... more A centrifugal compressor, with backward swept impeller, was designed for industrial applications and its performance was evaluated through numerical simulations. The baseline impeller geometry was then modified at the inducer leading edge to impart different forward and back sweeps. The inducer sweep was also associated with lean in the tangential direction. In all, seven impeller configurations were investigated, with inducer leading edge sweep varying from +25° (back sweep) to -20° (forward sweep). CFD simulations have indicated that the pressure ratio at design mass flow rate remained mostly unaffected by sweep, but showed a tendency to increase beyond an inducer back sweep of 20°. Similarly, a forward sweep of 20° gave lowest stall flow rate (highest stall margin). However, with an increase in tip clearance, the impeller with inlet forward sweep of 20° showed an increase in choke and stall mass flow rates. It is concluded that a forward sweep of 20°, with baseline tip clearance ...
Numerical Studies on the Effect of Purge Flow on the Performance and Flow Field of a Gas Turbine with Disc Cavity
Lecture Notes in Mechanical Engineering, 2016
International Journal of Rotating Machinery, 2015
Aspiration in an axial compressor is normally regarded as sucking out the low momentum boundary l... more Aspiration in an axial compressor is normally regarded as sucking out the low momentum boundary layer from blade suction surface, thus lowering the chances of flow separation and consequently that of stall under off-design operation. However, the suction mass flow does not take part in useful work and leads to loss of engine power output. This paper deals with a new concept of natural aspiration to energize blade suction surface boundary layer by injecting some fluid from pressure to suction side through a part span slot on the blade. The energized boundary layer has lesser tendency to separate, thus enhancing stall margin. Numerical simulations were carried out to study the effect of aspiration slot location and geometry on the performance and stall margin of a transonic axial compressor rotor. The computational results without aspiration slot were in fair agreement with the published experimental data. The modified rotor, with part span aspiration, showed ~3.2% improvement in stal...
International Journal of Rotating Machinery, 2016
The increasing trend of high stage pressure ratio with increased aerodynamic loading has led to r... more The increasing trend of high stage pressure ratio with increased aerodynamic loading has led to reduction in stable operating range of centrifugal compressors with stall and surge initiating at relatively higher mass flow rates. The casing treatment technique of stall control is found to be effective in axial compressors, but very limited research work is published on the application of this technique in centrifugal compressors. Present research was aimed to investigate the effect of casing treatment on the performance and stall margin of a high speed, 4 : 1 pressure ratio centrifugal compressor through numerical simulations using ANSYS CFX software. Three casing treatment configurations were developed and incorporated in the shroud over the inducer of the impeller. The predicted performance of baseline compressor (without casing treatment) was in good agreement with published experimental data. The compressor with different inducer casing treatment geometries showed varying levels ...
Numerical Studies on the Effect of Gurney Flap on Aerodynamic Performance and Stall Margin of a Transonic Axial Compressor Rotor
ASME 2014 Gas Turbine India Conference, 2014
Stall Margin Improvement in a Centrifugal Compressor Through Endwall Reshaping
ASME 2012 Gas Turbine India Conference, 2012
Effect of J-Shaped Casing Treatment on Flow Stability and Performance of an Axial Compressor
ASME 2012 Gas Turbine India Conference, 2012
Pressure, velocity, flow direction and mass flow measurements in cascades and turbomachinery testing
Presented is the text of a lecture delivered at the Short Term Advanced Educational Program on Ca... more Presented is the text of a lecture delivered at the Short Term Advanced Educational Program on Cascade Testing of Turbomachinery Blades at Hyderabad during December 7 to 18, 1981. It deals mainly with the pressure probe methods for measurements in 2-D cascades; however some aspects of measurements in rotating turbomachines are also discussed for the sake of completeness. General criteria for the selection of aerodynamic probes are outlined and the merits and demerits of some typical probes used in practice are discussed. Various devices available for the measurement of mass flow rate are also described. Methods for calibration of aerodynamic probes and flow measuring devices are presented and the use of calibration graphs is discussed.
Uploads
Papers by Quamber Nagpurwala