scholarly journals Parameterizing Compact and Extensible Compressor Models Using Orthogonal Distance Minimization

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Xavier Llamas ◽  
Lars Eriksson
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Mean Value ◽  
Low Flow ◽  
Model Parameters ◽  
Engine Model ◽  
Low Load ◽  
Measured Efficiency ◽  
Distance Minimization

A complete and compact control-oriented compressor model consisting of a mass flow submodel and an efficiency submodel is described. The final application of the model is a complete two-stroke mean value engine model (MVEM) which requires simulating the compressor operating at the low-flow and low-pressure ratio area. The model is based on previous research done for automotive-size compressors, and it is shown to be general enough to adapt well to the characteristics of the marine-size compressors. A physics-based efficiency model allows, together with the mass flow model, extrapolating to low-pressure ratios. The complexity of the model makes its parameterization a difficult task; hence, a method to efficiently estimate the 19 model parameters is proposed. The method computes analytic model gradients and uses them to minimize the orthogonal distances between the modeled speed lines (SpLs) and the measured points. The results of the parameter estimation are tested against nine different standard marine-size maps showing good agreement with the measured data. Furthermore, the results also show the importance of estimating the parameters of the mass flow and efficiency submodels at the same time to obtain an accurate model. The extrapolation capabilities to low-load regions are also tested using low-load measurements from an automotive-size compressor. It is shown that the model follows the measured efficiency trend down to low loads.

Three-Stage Low Pressure Compressor Modernization by Means of Optimization Methods

2015 ◽  
Author(s):  
Evgenii Goryachkin ◽  
Grigorii Popov ◽  
Oleg Baturin ◽  
Daria Kolmakova
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Optimization Methods ◽  
Low Pressure ◽  
Optimal Combination ◽  
Pareto Set ◽  
Optimization Task ◽  
Efficiency Increase ◽  
Optimization Parameters ◽  
Pressure Compressor

Low pressure compressor operation has some features. Firstly, the LPC stages work with cold air. For this reason there is transonic or subsonic flow in LPC. Secondly, the flow in LPC has complex spatial structure. Blade geometry of LPC is described by a large number of parameters. For this reason, it is difficult to pick up optimal combination of parameters manually. The solution of this problem is the usage of optimization methods to find the optimal combination of parameters. This approach was tested in this work. The main goal of this work was the LPC modernization for new parameters of gas turbine engine. Set of unimprovable solutions (Pareto set) was obtained as a result of solving optimization task. Pareto set was a compromise between the efficiency increase and the mass flow decrease. Each point from Pareto set had a correspondence with LPC unique geometry represented as an array of optimization parameters. One point of the Pareto set met all the required parameters of modernized LPC. The LPC geometry that guaranteed the efficiency increase by 1,3%, the total pressure ratio increase by 4% and mass flow rate decrease by 11% in comparison with the original LPC was obtained as a result of the investigation.

The Characteristics of Rotating Instabilities in Low Pressure Steam Turbines at Low Volume Flow Operation

2015 ◽  
Author(s):  
Roland Sigg ◽  
Timothy Rice
Keyword(s):  
Renewable Energy Sources ◽  
Low Pressure ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Low Flow ◽  
Small Scale ◽  
Steam Turbines ◽  
Original Design ◽  
Low Load

For flexible operation steam turbines may operate occasionally at low load. Operation away from the original design regime looks set to be an increasing trend mainly due to the presence of intermittently available renewable energy sources in the grid. This paper sets out an approach for considering low flow effects on turbine designs. At low load operating conditions rotating instabilities (RIS) can occur in the rear stages of LP steam turbines. The instabilities are comparable in many ways to rotating stall in compressors. Ideally the turbine blade natural frequencies should be designed to avoid the frequencies generated by the RIS system. The characteristics of RIS systems were experimentally investigated to understand the dependency with both flow coefficient and exhaust configuration. Correlations have been developed to characterize the dynamic pressure amplitudes and the fractional speed of the RIS moving around the wheel. The presented correlation based method is shown calibrated for a specific blade design. Two different test rigs provide the basis for the work presented. A low pressure model steam turbine provided detailed information for key blade/exhaust combinations. A simplified small scale air turbine was used to provide additional input for the behavior with alternative exhaust back wall position. Observations of the characteristic RIS behavior from model turbine tests are set in context with observed changes in the flow field.

Modeling and Simulation of Multistage Microcompressor With Passive Microvalves for Micro Coolers

2016 ◽  
Author(s):  
Shawn T. Le ◽  
Hisham Hegab
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
High Frequency ◽  
Pressure Ratio ◽  
Model Parameters ◽  
Negative Effect ◽  
Frequency Threshold ◽  
Gap Height ◽  
Operation Frequency

A cascaded multistage (2-stage) micro gas compressor in series is investigated through a lump model simulation to determine its feasibility in increasing compressor performance. A dynamic model of the micro gas compressor which consists of a unimorph piezoelectric diaphragm and passive micro check valves is presented and simulated with a Matlab Simulink® tool. Simulation is implemented for a 1 and 2-stage microcompressor design. Finite element analysis (FEA) is used to determine the lump model parameters from the fluid-structure interaction (FSI) between the microvalve and gas flow dynamics. FSI model parameters are extracted and developed as a lump model equation for Simulink® numerical computation. Dynamic simulations confirm that there is an increase in pressure ratio for a multistage microcompressor when compared to a single stage, which is achievable with passive microvalves. However, there are negative effects of using passive microvalves at high frequency. Frequency response results gathered from simulation shows that mass flow rate through the microvalve decreases above the frequency threshold ∼1 kHz for our design. This is in two parts due to a smaller gap height opening of the microvalve plate at high frequency and the reverse flow leakage. Both losses in mass flow rate from the microvalves decrease the total flow rate of the microcompressor above ∼1 kHz. Increasing actuation frequency below the ∼1 kHz threshold increases the flow rate of the microcompressor in the design. Therefore, it is concluded that the maximum flow rate of the microcompressor increases with increasing operation frequency, but becomes limited by the negative effect of the microvalve at a high frequency threshold due to the attenuation of the microvalve gap height. Although flow rate is affected, maximum pressure ratio of the microcompressor is still achievable at various frequency range, assuming the stroke volume of the pump chamber is constant throughout all frequency ranges. Multistage simulations show that the operation frequency ratio between each stage can have some negative effect in achieving the maximum theoretical pressure ratio.

PID-LIKE FLC FOR FOUR CYLINDERS MEAN VALUE GASOLINE ENGINE MODEL IN IDLE MODE

2018 ◽  
Vol 09 (02) ◽  
pp. 114-130
Author(s):  
Mohammed Hassan ◽  
◽  
Muslim Abdali ◽  
Keyword(s):  
Gasoline Engine ◽  
Mean Value ◽  
Idle Mode ◽  
Engine Model ◽  
Four Cylinders

scholarly journals Backflow effects on mass flow gain factor in a centrifugal pump

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042199886
Author(s):  
Wenzhe Kang ◽  
Lingjiu Zhou ◽  
Dianhai Liu ◽  
Zhengwei Wang
Keyword(s):  
Centrifugal Pump ◽  
Mass Flow ◽  
Flow Rate ◽  
Low Frequency ◽  
Gain Factor ◽  
Low Flow ◽  
Cavity Volume ◽  
Cavitating Flows ◽  
Inlet Tube ◽  
Low Flow Rate

Previous researches has shown that inlet backflow may occur in a centrifugal pump when running at low-flow-rate conditions and have nonnegligible effects on cavitation behaviors (e.g. mass flow gain factor) and cavitation stability (e.g. cavitation surge). To analyze the influences of backflow in impeller inlet, comparative studies of cavitating flows are carried out for two typical centrifugal pumps. A series of computational fluid dynamics (CFD) simulations were carried out for the cavitating flows in two pumps, based on the RANS (Reynolds-Averaged Naiver-Stokes) solver with the turbulence model of k- ω shear stress transport and homogeneous multiphase model. The cavity volume in Pump A (with less reversed flow in impeller inlet) decreases with the decreasing of flow rate, while the cavity volume in Pump B (with obvious inlet backflow) reach the minimum values at δ = 0.1285 and then increase as the flow rate decreases. For Pump A, the mass flow gain factors are negative and the absolute values increase with the decrease of cavitation number for all calculation conditions. For Pump B, the mass flow gain factors are negative for most conditions but positive for some conditions with low flow rate coefficients and low cavitation numbers, reaching the minimum value at condition of σ = 0.151 for most cases. The development of backflow in impeller inlet is found to be the essential reason for the great differences. For Pump B, the strong shearing between backflow and main flow lead to the cavitation in inlet tube. The cavity volume in the impeller decreases while that in the inlet tube increases with the decreasing of flow rate, which make the total cavity volume reaches the minimum value at δ = 0.1285 and then the mass flow gain factor become positive. Through the transient calculations for cavitating flows in two pumps, low-frequency fluctuations of pressure and flow rate are found in Pump B at some off-designed conditions (e.g. δ = 0.107, σ = 0.195). The relations among inlet pressure, inlet flow rate, cavity volume, and backflow are analyzed in detail to understand the periodic evolution of low-frequency fluctuations. Backflow is found to be the main reason which cause the positive value of mass flow gain factor at low-flow-rate conditions. Through the transient simulations of cavitating flow, backflow is considered as an important aspect closely related to the hydraulic stability of cavitating pumping system.

Highly Loaded Low-Pressure Turbine: Design, Numerical, and Experimental Analysis

2010 ◽  
Author(s):  
J. T. Schmitz ◽  
S. C. Morris ◽  
R. Ma ◽  
T. C. Corke ◽  
J. P. Clark ◽  
...  
Keyword(s):  
High Speed ◽  
Numerical Solutions ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Free Stream Turbulence ◽  
Low Pressure Turbine ◽  
The Mean ◽  
Highly Loaded

The performance and detailed flow physics of a highly loaded, transonic, low-pressure turbine stage has been investigated numerically and experimentally. The mean rotor Zweifel coefficient was 1.35, with dh/U2 = 2.8, and a total pressure ratio of 1.75. The aerodynamic design was based on recent developments in boundary layer transition modeling. Steady and unsteady numerical solutions were used to design the blade geometry as well as to predict the design and off-design performance. Measurements were acquired in a recently developed, high-speed, rotating turbine facility. The nozzle-vane only and full stage characteristics were measured with varied mass flow, Reynolds number, and free-stream turbulence. The efficiency calculated from torque at the design speed and pressure ratio of the turbine was found to be 90.6%. This compared favorably to the mean line target value of 90.5%. This paper will describe the measurements and numerical solutions in detail for both design and off-design conditions.

Autostoichiometric vapor deposition: Part I. Theory

1995 ◽  
Vol 10 (10) ◽  
pp. 2536-2541 ◽  
Author(s):  
Ren Xu
Keyword(s):  
Mass Flow ◽  
Vapor Deposition ◽  
Flow Analysis ◽  
Quantitative Measure ◽  
Low Pressure ◽  
Potential Candidate ◽  
Organic Complexes ◽  
Reaction Schemes

The possibility of an autostoichiometric vapor deposition is explored. Heterometal-organic complexes such as double alkoxides are potential candidate precursors for such deposition. Two reaction schemes, the hydrolysis-assisted pyrolysis and the hydrolysis-polycondensation of double alkoxides, are identified to be autostoichiometric reactions. A simple low-pressure apparatus is suggested for autostoichiometric vapor deposition. Mass-flow analysis allows for the identification of a nonstoichiometry factor K which can be used as a quantitative measure of the precursor's autostoichiometric capability.

scholarly journals Numerical Analysis of Side-loads Reduction in a Sub-scale Dual-bell Rocket Nozzle

2021 ◽  
Author(s):  
M. Cimini ◽  
E. Martelli ◽  
M. Bernardini
Keyword(s):  
Inflection Point ◽  
Pressure Ratio ◽  
Mean Value ◽  
Detached Eddy Simulation ◽  
Turbulent Structures ◽  
Eddy Simulation ◽  
Separation Shock ◽  
Delayed Detached Eddy Simulation ◽  
Controlled Flow ◽  
Dual Bell

AbstractA calibrated delayed detached eddy simulation of a sub-scale cold-gas dual-bell nozzle flow at high Reynolds number and in sea-level mode is carried out at nozzle pressure ratio NPR = 45.7. In this regime the over-expanded flow exhibits a symmetric and controlled flow separation at the inflection point, that is the junction between the two bells, leading to the generation of a low content of aerodynamic side loads with respect to conventional bell nozzles. The nozzle wall-pressure signature is analyzed in the frequency domain and compared with the experimental data available in the literature for the same geometry and flow conditions. The Fourier spectra in time and space (azimuthal wavenumber) show the presence of a persistent tone associated to the symmetric shock movement. Asymmetric modes are only slightly excited by the shock and the turbulent structures. The low mean value of the side-loads magnitude is in good agreement with the experiments and confirms that the inflection point dampens the aero-acoustic interaction between the separation-shock and the detached shear layer.

Numerical Analysis of Non-Radial Blading in a Low Speed and Low Pressure Turbine for Electric Turbocompounding Applications

2021 ◽  
Author(s):  
Eva Alvarez-Regueiro ◽  
Esperanza Barrera-Medrano ◽  
Ricardo Martinez-Botas ◽  
Srithar Rajoo
Keyword(s):  
Numerical Analysis ◽  
Numerical Simulations ◽  
Thermal Stresses ◽  
Waste Heat ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Blade Angle ◽  
Low Speed

Abstract This paper presents a CFD-based numerical analysis on the potential benefits of non-radial blading turbine for low speed-low pressure applications. Electric turbocompounding is a waste heat recovery technology consisting of a turbine coupled to a generator that transforms the energy left over in the engine exhaust gases, which is typically found at low pressure, into electricity. Turbines designed to operate at low specific speed are ideal for these applications since the peak efficiency occurs at lower pressure ratios than conventional high speed turbines. The baseline design consisted of a vaneless radial fibre turbine, operating at 1.2 pressure ratio and 28,000rpm. Experimental low temperature tests were carried out with the baseline radial blading turbine at nominal, lower and higher pressure ratio operating conditions to validate numerical simulations. The baseline turbine incidence angle effect was studied and positive inlet blade angle impact was assessed in the current paper. Four different turbine rotor designs of 20, 30, 40 and 50° of positive inlet blade angle are presented, with the aim to reduce the losses associated to positive incidence, specially at midspan. The volute domain was included in all CFD calculations to take into account the volute-rotor interactions. The results obtained from numerical simulations of the modified designs were compared with those from the baseline turbine rotor at design and off-design conditions. Total-to-static efficiency improved in all the non-radial blading designs at all operating points considered, by maximum of 1.5% at design conditions and 5% at off-design conditions, particularly at low pressure ratio. As non-radial fibre blading may be susceptible to high centrifugal and thermal stresses, a structural analysis was performed to assess the feasibility of each design. Most of non-radial blading designs showed acceptable levels of stress and deformation.

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