Iterative Method to Derive the Equivalent Centrifugal Compressor Performance at Various Operating Conditions: Part I: Modelling of Suction Parameters Impact

This paper introduces a new iterative method to predict the equivalent centrifugal compressor performance at various operating conditions. The presented theoretical analysis and empirical correlations provide a novel approach to derive the entire compressor map corresponding to various suction conditions without a prior knowledge of the detailed geometry. The efficiency model was derived to reflect the impact of physical gas properties, Mach number, and flow and work coefficients. One of the main features of the developed technique is the fact that it considers the variation in the gas properties and stage efficiency which makes it appropriate with hydrocarbons. This method has been tested to predict the performance of two multistage centrifugal compressors and the estimated characteristics are compared with the measured data. The carried comparison revealed a good matching with the actual values, including the stable operation region limits. Furthermore, an optimization study was conducted to investigate the influences of suction conditions on the stage efficiency and surge margin. Moreover, a new sort of presentation has been generated to obtain the equivalent performance characteristics for a constant discharge pressure operation at variable suction pressure and temperature working conditions. A further validation is included in part two of this study in order to evaluate the prediction capability of the derived model at various gas compositions

An Iterative Method to Derive the Equivalent Centrifugal Compressor Performance at Various Operating Conditions: Part II: Modeling of Gas Properties Impact

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

Engineering management of gas turbine power plant co2 for microalgae biofuel production

Fossil fuel accounts for over 80% of the world`s primary energy, particularly in areas of transportation, manufacturing and domestic heating. However, depletion of fossil reserves, frequent threats to the security of fossil fuel supply, coupled with concerns over emissions of greenhouse gases associated with fossil fuel use has motivated research towards developing renewable and sustainable sources for energy fuels. Consequently, the use of microalgae culture to convert CO2 from power plants flue gases into biomass that are readily converted into biofuel offers a window of opportunities to enhance, compliment or replace fossil- fuel-use. Interest in the use of microalgae biomass for biofuel production is high as it affords the potential for power plant CO2 sequestration – (1kg of dry algae biomass uses about 1.83kg CO2). Similarly, its capacity to utilise nutrients from a variety of wastewater, sets it apart from other biomass resources. These outlined benefits all emphasis the need for extended R&D efforts to advance commercial microalgae biofuel production. The paper is aimed at investigating the environmental performance of the microalgae biofuel production process using LCA

Effect of steam addition on the flow field and NOx emissions for Jet-A in an aircraft combustor

The steam injection technology for aircraft engines is gaining rising importance because of the strong limitations imposed by the legislation for NOx reduction in airports. In order to investigate the impact of steam addition on combustion and NOx emissions, an integrated performance-CFD-chemical reactor network (CRN) methodology was developed. The CFD results showed steam addition reduced the high temperature size and the radical pool moved downstream. Then different post-processing techniques are employed and CRN is generated to predict NOx emissions. This network consists of 14 chemical reactor elements and the results were in close agreement with the ICAO databank. The established CRN model was then used for steam addition study and the results showed under air/steam mixture atmosphere, high steam content could push the NOx formation region to the post-flame zone and a large amount of the NOx emission could be reduced when the steam mass fraction is quite high

A preliminary assessment of the initial compression power requirement in CO2 pipeline “Carbon Capture and Storage (CCS) technologies"

CO2 captured from fossil-fueled power generation plants is said to be economically transported via pipelines over long distances. The CO2 must be compressed to pipeline specifications using compressors and pumps that are driven by gas turbine (GT) or other prime movers. This paper presents the evaluation of actual work transfer or required prime power by modeling the governing equations of compression using the Peng–Robinson equation of state (PR-EOS). A computer code was developed to carry out the modeling and subsequent simulation of the compression power requirement. The simulation of prime mover power was carried out for different technology (head per stage) of the compressor ranging from 10-staged compression to double stage compression. The results show that the current technology of the centrifugal compressor could require as much as 23MW of prime mover power to compress 1.5 million tonnes per year of CO2—a projected equivalent CO2 released from a 530MW combined cycle gas turbine (CCGT) power generation plant

A dynamic convergence control scheme for the solution of the radial equilibrium equation in through-flow analyses

One of the most frequently encountered numerical problems in scientific analyses is the solution of non-linear equations. Often the analysis of complex phenomena falls beyond the range of applicability of the numerical methods available in the public domain, and demands the design of dedicated algorithms that will approximate, to a specified precision, the mathematical solution of specific problems. These algorithms can be developed from scratch or through the amalgamation of existing techniques. The accurate solution of the full radial equilibrium equation (REE) in streamline curvature (SLC) through-flow analyses presents such a case. This article discusses the development, validation, and application of an 'intelligent' dynamic convergence control (DCC) algorithm for the fast, accurate, and robust numerical solution of the non-linear equations of motion for two-dimensional flow fields. The algorithm was developed to eliminate the large extent of user intervention, usually required by standard numerical methods. The DCC algorithm was integrated into a turbomachinery design and performance simulation software tool and was tested rigorously, particularly at compressor operating regimes traditionally exhibiting convergence difficulties (i.e. far off-design conditions). Typical error histories and comparisons of simulated results against experimental are presented in this article for a particular case study. For all case studies examined, it was found that the algorithm could successfully 'guide' the solution down to the specified error tolerance, at the expense of a slightly slower iteration process (compared to a conventional Newton-Raphson scheme). This hybrid DCC algorithm can also find use in many other engineering and scientific applications that require the robust solution of mathematical problems by numerical instead of analytical means

Exergetic, exergoeconomic and exergoenvironmental analysis of intercooled gas turbine engine

Exergetic and exergoeconomic and exergoenvironmental analyses have been performed for an advanced aero-derivative intercooled gas turbine engine. The proposed system was modelled using the IPSEpro software package and validated using manufacturer’s published data. The exergoeconomic model evaluates the cost-effectiveness of the gas turbine engine based on the Specific Exergy Costing [SPECO] method. The CO2 emissions per KWh were estimated using a generic combustor model, HEPHAESTUS, developed at Cranfield University. It is well known that the exergetic analysis can determine the magnitudes, locations and types of losses within an energy system. The effect of load and ambient temperature variations on gas turbine performance were investigated for two different configurations. The first system, Case-I, was a simple gas turbine (SCGT) engine, and the second, Case-II, an intercooling gas turbine (ICGT) system. The latter enhances gas turbine efficiency but, at the same time, has an adverse effect on the combustion chamber due to reduced compressed air temperature. It was confirmed that full load and low ambient temperature are preferable due to the low waste exergy. The unit exergy cost rate for both SCGT and ICGT have been calculated as 8.59 and 8.32 US$/GJ respectively. The exergoenvironmental results show the ICGT achieved lower emission levels and is more environmentally friendly than the SCGT

TERA- A Tool for Aero-engine Modelling and Management

One of the distinguishing features of the civil aero-engine market is its high competitiveness. The costs and risks associated with new projects are such that the difference between two apparently equally attractive options could result in success from one and a threat to the survival of the company from the other. To conceive and assess engines with minimum global warming impact and lowest cost of ownership in a variety of emission legislation scenarios, emissions taxation policies, fiscal and Air Traffic Management environments, a Techno-economic and Environmental Risk Assessment (TERA) model is needed. TERA incorporates multi-disciplinary modules for modelling gas turbine and aircraft performance, estimation of engine weight, noise and emissions as well as environment impact and operating economics. The TERA software is integrated with a commercial optimiser and provides a means for cycle studies. It is to be expected that new legislative and fiscal constraints on air travel will demand an extension to the customary range of asset management parameters. In such a business environment there is potential for TERA to develop into a useful tool for aircraft and engine asset management. This paper presents a description of this tool as well as gives some results from scenario studies

Effect of steam addition on gas turbine combustor design and performance

Adding steam influences the combustion process inside the combustor, which should be taken into account during combustor design. The design of combustor has long been the most challenging process. This study integrated the gas turbine performance with the combustor design, and formulated a detailed procedure for single annular combustors with steam addition consideration in particular. To accomplish this, a computer code has been developed based on the design procedures. The design model could provide the combustor geometry and the combustor performance. The inlet parameters for combustor design are obtained and validated through the calculation of gas turbine engine performance provided by our own home code. The model predictions are compared with operational and configuration data from two real engines and show reasonably good accuracy. The influence of steam addition on combustor design is investigated and results showed the variation of geometrical size is highest for components where intense combustion takes place while the design is almost kept the same for components where only pure flow exists. After conforming the feasibility of the combustor design code, we investigated the effects of steam addition on combustor performance. It revealed that steam injection is an effective way to reduce the temperature in the burner while other performance like the total pressure loss would be slightly deteriorated

Installed performance assessment of a boundary layer ingesting distributed propulsion system at design point

Boundary layer ingesting systems have been proposed as a concept with great potential for reducing the fuel consumption of conventional propulsion systems and the overall drag of an aircraft. These studies have indicated that if the aerodynamic and efficiency losses were minimised, the propulsion system demonstrated substantial power consumption benefits in comparison to equivalent propulsion systems operating in free stream flow. Previously assessed analytical methods for BLI simulation have been from an uninstalled perspective. This research will present the formulation of an rapid analytical method for preliminary design studies which evaluates the installed performance of a boundary layer ingesting system. The method uses boundary layer theory and one dimensional gas dynamics to assess the performance of an integrated system. The method was applied to a case study of the distributed propulsor array of a blended wing body aircraft. There was particular focus on assessment how local flow characteristics influence the performance of individual propulsors and the propulsion system as a whole. The application of the model show that the spanwise flow variation has a significant impact on the performance of the array as a whole. A clear optimum design point is identified which minimises the power consumption for an array with a fixed configuration and net propulsive force requirement. In addition, the sensitivity of the system to distortion related losses is determined and a point is identi ed where a conventional free-stream propulsor is the lower power option. Power saving coefficient for the configurations considered is estimated to lie in the region of 15%