Centrifugal Compressor Map Prediction and Modification

International Journal of Fluid Machinery and Systems, 2012

One centrifugal compressor is applied for refrigeration and its working substance is R134a. The operating points obtained by using similar conversion at different rotation speeds are compared with the numerical results. They keep consistent with each other while the rotation speeds are lower, but the error between them will become large with the increasing of the rotation speed. Then the operating points are obtained when the working substance is air by using two similar conversion methods separately. Based on the comparison, it can be obtained that the result of keeping the specific volume ratio of inlet and outlet is more accurate than the result of maintaining Ma number. Then the test result is compared with the similarity result and the numerical result when the working substance is air. It is obtained that the similarity result is more consistent with the test result better than the numerical result and the trend of efficiency and pressure ratio change with the flow rate is consistent with the test result. In the process of similar conversion, the efficiency η is no useful for similitude design and it has less influence on the conversion result.

Internal Combustion Engines

Simulation of the supercharged internal combustion engines operation cycle is impossible without correct estimation of the supercharger operating parameters. Standard approach is to use specially prepared performance maps of compressor and turbine of the turbocharger, which are based on the experimental (or manufacturer’s) raw data. Centrifugal compressor performance maps interpolation, extrapolation and treatment provides challenging requirements as it is important to get correct simulation under such special conditions as compressor choke, rotating stall and pumping surge. At the same time it’s important to obtain the fast and stable calculations of the engine’s operating cycle. Blitz-PRO – online internal combustion engines operating cycle simulation service – offers supercharger performance maps preprocessing and implementation. It provides three different modes of compressor surge consideration during calculations: 1) full-scale surge mode using Moore-Greitzer approach; 2) mild...

INCAS BULLETIN, 2018

The active control for centrifugal compressor systems consists in using, monitoring and managing the sensors to detect fluid disturbances, the actuators to introduce desired perturbations and a suitable controller to determine the optimal actuator actions using the sensor information. The object of an interesting centrifugal compressor design is to obtain the most air through a given diameter compressor, with a minimum number of stages while maintaining high efficiencies and aerodynamic stability over the operating range. The high efficiency of the axial compressor system decreases dramatically when used in small high-pressure applications, especially due to the large relative tip clearance. In addition, the high centrifugal force, dominating the pressure rise, results in a superior operability and the short axial length of the centrifugal compressor offers rotor-dynamic multiple advantages. These qualities allow the centrifugal compressor system to be used as the last stage of a high-pressure compressor of an aero engine as well as turbo pump assemblies used in liquid-propelled rocket engines.

This is the second part of a study conducted to model the aerothermodynamic impact of suction parameters and gas properties on a multi-stage centrifugal compressor's performance. A new iterative method has been developed in the first part to derive the equivalent performance at various operating conditions. This approach has been validated to predict the compressor map at different suction pressures and temperatures using the design characteristics as reference values. A further case is included in this paper in order to emphasize the validity of the developed approach to obtain the performance characteristics at various gas compositions. The provided example shows that the performance parameters at different gas mixtures can be predicted to within ±1.34%. Furthermore, the conducted optimization in this paper reveals that the proposed method can be applied for the compressor design evaluation corresponding to the expected variation in suction conditions. Moreover, the examined case study demonstrates the effect of gas properties' variation on the operating point and aerodynamic stability of the entire compression system. In order to achieve that, a simple approach has been established to assess the contribution of gas properties' variation to the inefficient and unstable compressor performance based on the available operational data.

Journal of Physics: Conference Series, 2018

Centrifugal compressors (impeller), sometimes termed radial compressors, are a subclass of dynamic axisymmetric turbomachinery device. The idealized compressive dynamic turbo-machine achieves a pressure rise by adding kinetic energy/velocity to a continuous flow of fluid through the rotor or impeller. This kinetic energy is then converted to an increase in potential energy/static pressure by slowing the flow through a diffuser. Small Centrifugal compressor now is commonly used for mini turbojet engine which applications are in rapid drone among others. The usage of small centrifugal compressor in the mini turbojet has several advantages. One of them is that it can give higher pressure ratio than axial compressor (for example common single stage small centrifugal compressor can give 3-4 in pressure ratio at 80000-98000 rpm). The purpose of this paper is to assess the effect of geometry parameters, such as fillet radius, number of splitter and blades, to the pressure ratio. In this paper, typical small centrifugal compressor with diameter of 6.6 cm will be simulated using NUMECA, a CFD software and their results will be discussed to map the effect of each geometry parameter to pressure ratio hence compressor performance. Different geometry parameters are calculated and compared at several boundary conditions and flow setting to explore the trend of pressure ratio evolution with the change of those parameters. Based on the simulation result is indicated that there is similiar effect on the applying spplitter and adding blade number in the impeller configuration to increase the pressure ratio. In another case, adding fillet at the end of impeller hub wall give tendency to reduce compressor pressure ratio.

The design and off-design performance characteristics of single stage centrifugal compressor consisting of 12 vanes impeller interfacing with 11 vanes diffuser have been studied experimentally and numerically. The impeller has been designed and developed with radial exit, 30o inlet blade angle (with tangent), 77 mm diameter and the discharge volute considering constant mean flow velocity. The performance of the compressor at varying capacity (60 to 120 % of design) by controlling the discharge valve and with the variation of rotating speed (15000 to 35000 rpm) by regulating speed of the coupled gas turbine has been conducted at the recently developed test rig. The numerical simulation has been done by adopting viscous Reynolds Average Navier-Stokes (RANS) equations with and without Coriolis Force & Centrifugal Force in rotating reference frame (impeller) and stationary reference frame (casing) respectively utilizing CFD software Fluent 14. The flow around a single vane of impeller interfacing with single vane of diffuser, the rotational periodicity and sliding mesh at the interfacing zone between rotating impeller and stationery diffuser are considered. Non dimensional performance curves derived from experimental and numerical results are presented and compared. The numerical results are found to match very closely with the experimented data near the design point and deviation is observed at the both side of the designed operating point. Non-uniform pressure profiles towards the impeller exit and strong cross flow from blade to blade are detected at low flow operating conditions. Total pressure, static pressure and velocity distributions at design and off design operation obtained from the CFD results are analysed and presented here.

2020

Centrifugal compressors are used widely in various range of aero-engine applications both small and medium-sized. And its performance affects the working state of the engine. So in this thesis I am going to briefly explain how the performance affects the working state using three different solutions. The first is the normal numerical solution using compal, in this solution, working conditions were added to get performance curves which I will discuss later in this thesis. The second solution is the blade to blade solution and the third solution is the computational fluid dynamics (CFD) solution. Computational Fluid Dynamics is usually used in centrifugal compressor design. Computational fluid dynamics provides extensive optimization chances for the compressor design instead of designing the centrifugal compressor. The design process is still an important part of the compressor developments. The wide range of design subjects represents a very not so easy design world for centrifugal compressor designers. So, a few basic information for centrifugal design is still quite important. The impeller is the most useful part of the centrifugal stage. Designing a very efficiency centrifugal impeller with a wide operation range can ensure overall design success. With these three solution how briefly explain how they affect the working state of the centrifugal compressor. Keywords: Centrifugal compressor; Mass flow; Pressure ratio; CFD; Overall performance. Blade to Blade; Compal solution.

International Journal of Mechanical Engineering Education, 1994

This paper describes computer-aided analysis of centrifugal compressors (CAACC), a micro-computer-based, interactive, and menu-driven software package for use as an educational tool by mechanical engineering students studying radial flow compressors. CAACC is written in the Pascal computer language and runs on IBM PC, or compatible, computers. In addition to solving for any unknown variables, the graphical utilities of the package allow the user to display a diagrammatic sketch of the compressor and to draw velocity diagrams at several locations. Furthermore, the program allows the investigation and plotting of the variation of any parameter versus any other parameter. Through this option, the package guides the student in learning the basics of centrifugal compressors by the various performance studies that can be undertaken and graphically displayed. The comprehensive example presented demonstrates the capabilities of the package as a teaching tool.

Both computational and experimental investigations were utilized to study the flow behavior inside the four-stage centrifugal compressor. Computational study was carried out by the commercial code “CFD-RC”. Experimental work was accomplished by the use of a data acquisition system, advanced sensors and “LabView” interface software. Comparisons between computational and experimental outputs were performed. The computational code was validated experimentally and numerically. Compressor map was drawn numerically and experimentally. Surge was unsteadily simulated. Surge predicted at mass flow equal to 0.0093 kg/s for 12,000 rpm with full-domain solution. Using the parallel computational technology, by “HPC” program, is recommended for future work.

Energies, 2015

This is the second part of a study conducted to model the aerothermodynamic impact of suction parameters and gas properties on a multi-stage centrifugal compressor's performance. A new iterative method has been developed in the first part to derive the equivalent performance at various operating conditions. This approach has been validated to predict the compressor map at different suction pressures and temperatures using the design characteristics as reference values. A further case is included in this paper in order to emphasize the validity of the developed approach to obtain the performance characteristics at various gas compositions. The provided example shows that the performance parameters at different gas mixtures can be predicted to within ±1.34%. Furthermore, the conducted optimization in this paper reveals that the proposed method can be applied for the compressor design evaluation corresponding to the expected variation in suction conditions. Moreover, the examined case study demonstrates the effect of gas properties' variation on the operating point and aerodynamic stability of the entire compression system. In order to achieve that, a simple approach has been established to assess the contribution of gas properties' variation to the inefficient and unstable compressor performance based on the available operational data.