Compressor Delivery Research Articles

Comparative Assessment of Fouling Scenarios in an Axial Flow Compressor

Abstract It is commonly accepted that fouling degrades severely axial compressor performance. Deposits build up as operating hours sum up, causing a decrease in the compressor's delivery pressure, efficiency, and flow capacity. Compressor susceptibility to fouling depends on many factors, such as atmospheric conditions, air quality, filtration system, and the size and design of the compressor. The current study identifies four basic operating scenarios which refer to the same compressor, in order to put forward a comparative assessment as to how incoming air quality would affect compressor performance. SOCRATES, an in-house, streamline curvature-based through-flow tool, in conjunction with a detailed, fully customizable fouling empirical model, conceived based on flow physics and relevant experimental data, is used to qualify and quantify compressor degradation with time.

Power regeneration upgrading of vapour compression refrigeration plants

Power Regeneration Technique in Vapour Compression Refrigeration Plants is presented for the purpose of upgrading already existing plants, each characterized by Main Compressor, Evaporator, Condenser and Main Expansion Valve.The Power Regeneration Concept is illustrated and theoretical results deeply discussed in relation to the upgrading of Refrigeration Plants whose Cooling Power being given or whose Main Compressor remain unchanged. Changes in performance and internal variables are deeply analysed for various arrangement options. Experimental results are also given providing the performance improvement of the Refrigeration Plants equipped with Power Regeneration Systems. Cooling Power and COP improvements up to 100% and 80% respectively are expected for a given Main Screw Compressor; while COP increasing up to 70% and Main Compressor Delivery reduced to 50% are evidenced for constant Cooling Power Plants.

Performance Analysis of a Solar-Powered Multi-Effect Refrigeration System

The main objective of the current work is to investigate the thermodynamic performance of a novel solar powered multi-effect refrigeration system. The proposed cycle consists of a solar tower system with a heliostat field and central receiver (CR) that has molten salt as the heat transfer fluid, an absorption refrigeration cycle (ARC), an ejector refrigeration cycle (ERC), and a cascade refrigeration cycle (CRC). Energy and exergy analyses were carried out to measure the thermodynamic performance of the proposed cycle, using Dhahran weather data and operating conditions. The largest contribution to cycle irreversibility was found to be from the CR system (52.5%), followed by the heliostat field (25%). The first and second-law efficiencies improved due to the increase in the following parameters: ejector evaporator temperature, turbine inlet and exit pressures, and cascade evaporator temperature. Parametric analysis showed that the compressor delivery pressure, turbine inlet and exit pressures, hot molten salt outlet temperature, and ejector evaporator temperature significantly affect the refrigeration output.

Experimental investigation on flow unsteadiness during spike stall suppression process in an axial compressor via air injection

Stall recovery process for performance enhancement of an axial compressor has been experimentally carried out using air injection at its rotor blade row tip region. Twelve air injectors had been mounted evenly spaced around the compressor casing upstream the rotor blade row. Instantaneous flow velocities at various radial and circumferential positions were measured simultaneously utilizing hot wire anemometry. These unsteady results, separately presented in frequency and time domains, provided to distinguish stall inception process and consequent flow induced fluctuations. Time-dependent responses of the flow field properties within the compressor passage and progressive alleviation of stall cells are demonstrated during the tip injection process. Blade tip air injection worked effectively and enhanced the compressor stall margin about 9%. This attractive result occurred for the case where the total mass flow rate passing through the air injectors was as small as 0.8% of the compressor main flow rate. In addition, this augmentation in the stall margin was accompanied by increase in the compressor delivery total pressure. Air injection at the blade row tip region caused its beneficial effects to extend throughout the blade whole span, especially while working at the near-stall conditions.

Energy-Saving Multistage Filling of Adsorption Natural Gas Storage System

A theoretical analysis of multistage (cascade) method of filling adsorption methane storage systems is made from the energy saving standpoint. It is demonstrated that multistage filling saves energy for gas compression substantially. The beneficial effect is much less if the compressed gas is filled in a cylinder without an adsorbent. The influence of the number of filling stages and the theoretical maximum of idealized filling with gradual elevation of compressor delivery pressure as the limiting case of multistage filling with an infinite number of stages are shown. The rated minimum energy consumption is 12% of the energy consumed for filling compressed gas in a system containing no adsorbent.

Thermodynamic analysis of a CNG refueling station considering the reciprocating compressor

The reciprocating compressor is the heart of a CNG refueling station with dominating influence on refueling process. The main operating cost of a CNG refueling station arises from the compressor input work. The reciprocating compressor have not been subjected to previous studies which investigated the CNG refueling stations. The main objective of the present work is to apply a thermodynamic analysis for modeling a CNG refueling station, including on-board NGV cylinder, reservoir tanks, connecting pipes and especially reciprocating compressor. Unlike most previous researches, pressure variation of the reservoir tanks during the filling process have been considered which necessary for compressor modeling. The results of the present work have been validated against the previous experimental data and theoretical studies. The additional experimental data, measured by the present authors, is also used to analyze and identify the compressor performance in unsteady conditions. The simulation result of mass flow rate is a good agreement with the experimental values. The results show that variations in the compressor discharge pressure have no effect on the first and intermediate compressor pressure. It has also no effect on the compressor delivery mass flow rate. The energy consumption by the compressor for a cycle (including discharge and charge zones) is found to be 61.86 kWh. The average specific energy consumption to fill a vehicle is found to be 0.250 kWh/kg.

A Preliminary Design Tradeoff Study for an Advanced Propulsion Technology Rotorcraft at Mission Level

This paper aims to present an integrated rotorcraft (RC) multidisciplinary simulation framework, deployed for the comprehensive assessment of combined RC–powerplant systems at mission level. The proposed methodology comprises a wide-range of individual modeling theories applicable to RC performance and flight dynamics, as well as the gas turbine engine performance. The overall methodology has been deployed to conduct a preliminary tradeoff study for a reference simple cycle (SC) and conceptual regenerative twin-engine-light (TEL) and twin-engine-medium (TEM) RC configurations, modeled after the Airbus Helicopters Bo105 and Aérospatiale SA330 models, simulated under the representative mission scenarios. The installed engines corresponding to both reference RC are notionally modified by incorporating a heat exchanger (HE), enabling heat transfer between the exhaust gas and the compressor delivery air to the combustion chamber. This process of preheating the compressor delivery air prior to combustion chamber leads to a lower fuel input requirements compared to the reference SC engine. The benefits arising from the adoption of the on-board HE are first presented by conducting part-load performance analysis against the reference SC engine. The acquired results suggest substantial reduction in specific fuel consumption (SFC) for a major part of the operating power range with respect to both RC configurations. The study is further extended to quantify mission fuel burn (MFB) saving limit by conducting an extensive HE tradeoff analyses at mission level. The optimum fuel burn saving limit resulting from the incorporation of on-board HEs is identified within realistically defined missions, corresponding to modern RC operations. The acquired results from the mission analyses tradeoff study suggest that the suboptimum regenerated RC configurations are capable of achieving significant reduction in MFB, while simultaneously maintaining the respective airworthiness requirements in terms of one-engine-inoperative. The proposed methodology can effectively be regarded as an enabling technology for the comprehensive assessment of conventional and conceptual RC–powerplant systems at mission level.

Intercooled Aero-Gas-Turbine Duct Aerodynamics: Core Air Delivery Ducts

The development of radical new aero engine technologies will be key to delivering the step-changes in aircraft environmental performance required to meet future emissions legislation. Intercooling has the potential for higher overall pressure ratios, enabling reduced fuel consumption, and/or lower compressor delivery air temperatures and therefore reduced NOx. This paper considers the aerodynamics associated with the complex ducting system that would be required to transfer flow from the core engine path to the heat exchanger system. The cycle benefits associated with intercooling could be offset by the pressure losses within this ducting system and/or any detrimental effect the system has on the surrounding components. A suitable branched S-shaped duct system has been numerically developed which diffuses and delivers the flow from the engine core to discrete intercooler modules. A novel swirling duct concept was used to locally open larger spacing between certain duct branches in order to provide engine core access whilst hiding the resultant pressure field from the upstream turbomachinery. The candidate duct system was experimentally evaluated on a bespoke low speed, fully annular isothermal test facility. Aerodynamic measurements demonstrated the ability of the design to meet the stringent aerodynamic and geometric constraints.

Preliminary Experimental Results of Integrated Gasification Fuel Cell Operation Using Hardware Simulation

A newly developed integrated gasification fuel cell (IGFC) hybrid system concept has been tested using the Hybrid Performance (Hyper) project hardware-based simulation facility at the U.S. Department of Energy, National Energy Technology Laboratory. The cathode-loop hardware facility, previously connected to the real-time fuel cell model, was integrated with a real-time model of a gasifier of solid (biomass and fossil) fuel. The fuel cells are operated at the compressor delivery pressure, and they are fueled by an updraft atmospheric gasifier, through the syngas conditioning train for tar removal and syngas compression. The system was brought to steady state; then several perturbations in open loop (variable speed) and closed loop (constant speed) were performed in order to characterize the IGFC behavior. Coupled experiments and computations have shown the feasibility of relatively fast control of the plant as well as a possible mitigation strategy to reduce the thermal stress on the fuel cells as a consequence of load variation and change in gasifier operating conditions. Results also provided an insight into the different features of variable versus constant speed operation of the gas turbine section.

Reduced order state-space modelling of a two-shaft turbofan engine for control and off-design performance analysis

A simplified, low order state-space approach for dynamic modelling of a twin spool turbofan gas turbine engine is proposed and investigated. The governing equations constituting the dynamic model of the engine are derived analytically by considering 1D mass, moment and energy balance equations at intermediate engine stations. Engine subsystems are modelled by using algebraic relationships, neural networks and experimental data collected through rig tests. Simulations are performed at various operation conditions for investigating the off-design and transient behaviour of the engine system. The simulation results are compared with the experimental time series data recorded during engine test runs. The responses of the model are found to be in good agreement with the experimental results for critical engine parameters such as shaft speeds, compressor delivery pressure, turbine inlet temperatures, etc. The proposed model may be extended for use in real-time engine simulation scenarios such as closed loop testing of engine control and condition monitoring systems.

Fault Detection in Multivariate Signals With Applications to Gas Turbines

This paper proposes a fault detection method for multivariate signals. The method assesses whether or not the multivariate autocovariance functions of two independently sampled system signals coincide. If the first signal is known to be sampled from a well-functioning system, then rejection of signal equality is tantamount to concluding that the second signal is sampled from a faulty system. The proposed method is based on the asymptotic properties of the periodogram of multivariate stationary time series and is nonparametric in nature; in particular, there is no need to model the signals under study, an often arduous task. Several natural and synthetic faults were introduced in a Solar Turbines Mercury 50 4.5 MW gas turbine and the resulting compressor delivery pressure and generated electrical power were analyzed. The proposed method capably detected all faults.

Rain Ingestion in Axial Flow Compressors at Part Speed

New experimental work is reported on the effects of water ingestion on the performance of an axial flow compressor. The background to the work is the effect that heavy rain has on an aeroengine compressor when operating in a “descent idle” mode, i.e., when the compressor is operating at part speed and when the aeromechanical effects of water ingestion are more important than the thermodynamic effects. Most of our existing knowledge in this field comes from whole engine tests. The current work provides the first known results from direct measurements on a stand-alone compressor. The influence of droplet size on path trajectory is considered both computationally and experimentally to show that most rain droplets will collide with the first row of rotor blades. The water on the blades is then centrifuged toward the casing where the normal airflow patterns in the vicinity of the rotor tips are disrupted. The result of this disruption is a reduction in compressor delivery pressure and an increase in the torque required to keep the compressor speed constant. Both effects reduce the efficiency of the machine. The behavior of the water in the blade rows is examined in detail, and simple models are proposed to explain the loss of pressure rise and the increase in torque. The measurements were obtained in a low speed compressor, making it possible to study the mechanical (increase in torque) and aerodynamic (reduction in pressure rise) effects of water ingestion without the added complication of thermodynamic effects.

The Effect of Water Injection on Multispool Gas Turbine Behavior

Abstract Background: The injection of water droplets into industrial gas turbines is now commonplace and is central to several proposed advanced cycles. These cycles benefit from the subsequent reduction in compressor work, the increase in turbine work, and (in the case of recuperated cycles) reduction in compressor delivery temperature, which all act to increase the efficiency and power output. An investigation is presented here into the effect such water droplets will have on the operating point and flow characteristics of an aeroderivative gas turbine cycle. Method of Approach: The paper first describes the development of a computer program to study the effects of water injection in multispool industrial gas turbines. The program can operate in two modes: the first uses pre-determined nondimensional wet compressor maps to match the components and is instructive and fast but limited in scope; the second uses the compressor geometries as input and calculates the wet compressor operating conditions as and when required. As a result, it is more computationally demanding, but can cope with a wider range of circumstances. In both cases the compressor characteristics are calculated from a mean-line analysis using suitable loss, deviation and blockage models, coupled with Lagrangian-style droplet evaporation calculations. The program has been applied to a three-spool machine to address issues such as the effects of water injection on power output and overall efficiency, and the off-design nature of the compressor operation. Results: Preliminary results calculated on this basis show similar trends to predictions for single-shaft machines, namely that air mass flow rates and pressure ratios are increased by water injection, and that early stages of the compressor are shifted towards choke and rear stages towards stall. The LP compressor in particular operates at severely off-design conditions. Conclusions: The predicted overall performance of the three-spool machine shows a substantial power boost and a marginal increase in thermal efficiency.

Research on oil-free air scroll compressor with high speed in 30 kW fuel cell

To supply the clean compressed air to a fuel cell system, an oil-free compressor is needed. The working process of the oil-free air scroll compressor and its cooling feature are discussed in this paper. A prototype, delivering 100 m 3/h and having a speed of 5000 rpm, is researched. The water from the fuel cell system is used as the lubricant of the bearings and the moving parts of the compressor. The prototype of the oil-free air scroll compressor has been designed, fabricated and tested, and the performances are satisfactory. Whatever material the scroll parts are constructed of, for example, aluminum alloy or titanium alloy, the trend of the compressor delivery with rotary speed is similar. However, the power consumption varies with the materials and the surface coating of the scroll parts because different materials and surface coating have different friction coefficients.

SCGT/CC: An innovative cycle with advanced environmental and peakload shaving features

An innovative gas turbine cycle is studied, which can offer several advantages from the point of view of environmental friendship and peakload shaving capabilities. The basic idea of SCGT/CC is of cooling down the exhaust to temperatures as low as to allow full condensation of the water vapor; a large part of the exhaust gases is then recirculated to the compressor; the condensed water can be reinjected by means of a pump at compressor delivery. For maximum performance it is convenient not to inject this water flow, but rather to use it for other purposes; however, water injection produces a power boosting effect (at the expense of a small decrease in efficiency) which can be useful for peakload shaving applications. The working gas composition in the GT cycle is that corresponding to stoichiometric combustion, which opens the possibility of applying techniques for CO 2 recycling and general exhaust gas treatment. The cycle guarantees a high level of efficiency, and its adoption should imply minor modifications to existing equipment.

Advanced materials mean advanced engines

In this, the third Finniston Lecture, the recent advances in aero engine technology made possible by interdisciplinary collaboration between materials scientists and design and manufacturing engineers are reviewed. Of crucial importance is the efficient and cost effective design of component geometries with due regard for material properties and manufacturing process capability. The three operating parameters that most directly define the thrust and fuel consumption of an aircraft gas turbine – fan airflow, or diameter, overall pressure ratio, or compressor delivery temperature, and turbine inlet temperature – are in turn largely dependent on these capabilities. As bypass ratios of commercial turbofans increase, the weight of the large diameter components becomes increasingly important. Titanium and composite materials, each with their own advanced manufacturing techniques, allow thrusts of 100000lb to be achieved at acceptable weight. Overall pressure ratio is a major influence in improving fuel consumption. The resulting temperature determines the choice of material – nickel alloy or advanced titanium, and detail design of components in this area is important to make full use of the material capability. High pressure turbine blades represent a most complex design challenge. Nickel alloys have developed to a third generation single crystal standard and ceramics offer a prospect of even higher temperature capability. It is concluded that planning from the start to have dual use application in civil and defence markets is the most cost effective route to further progress.

Advanced materials mean advanced engines

AbstractIn this, the third Finniston Lecture, the recent advances in aero engine technology made possible by interdisciplinary collaboration between materials scientists and design and manufacturing engineers are reviewed. Of crucial importance is the efficient and cost effective design of component geometries with due regard for material properties and manufacturing process capability. The three operating parameters that most directly define the thrust and fuel consumption of an aircraft gas turbine – fan airflow, or diameter, overall pressure ratio, or compressor delivery temperature, and turbine inlet temperature – are in turn largely dependent on these capabilities. As bypass ratios of commercial turbofans increase, the weight of the large diameter components becomes increasingly important. Titanium and composite materials, each with their own advanced manufacturing techniques, allow thrusts of 100 000 lb to be achieved at acceptable weight. Overall pressure ratio is a major influence in improving fue...

Small gas turbine using a second-generation pulse combustor

The design of a second-generation valveless pulse pressure-gain combustor, intended for use as an alternative to the conventional steady-flow combustor of a gas turbine, is described. What are believed to be the first relatively comprehensive test results ever obtained from a pulse-combustor equipped gas turbine are presented for a small gas-generator-type unit. It was shown experimentally that the pulse combustor was able to maintain a small stagnation pressure gain of between 1.1 and 1.6% of the compressor delivery pressure over the entire operating range of the gas turbine. It was also found that the potential net power production of the gas generator was improved, up to a maximum of 40%, substantially over the complete operating range of the very lowpressure-ratio machine as a consequence of using the pulse combustor. The performance improvement was greatest at low rotor speed and least at high rotor speed. Additionally, it was noted that the gas turbine noise level increased due to use of the pulse combustor. Means are suggested for improving the pressure-gain performance of the pulse combustor and reducing the volume it occupies.

Waste energy utilization in heat-exchange gas turbine cycles

One of the ways that can be used to increase the efficiency of a shaft gas turbine engine is by installing heat exchanger in one of the following two configurations: 1. 1. After the low pressure turbine (usual case); 2. 2. After the high pressure turbine (suggested). Analysis of ideal cycles as well as a real cycle for both configurations is done by using a computer program, where the following parameters were studied: heat exchanger effectiveness, turbine efficiency, compressor efficiency, ratio of turbine inlet pressure to compressor delivery pressure ( P 3 P 2 ), and maximum temperature ratio ( T 3 T 1 ). From the sensitivity analysis for both configurations the unusual configuration is inferior to the suggested in terms of the relative effects of compressor and turbine efficiencies on the overall efficiency and turbine inlet pressure on overall thermal efficiency and power output. However, the usual method is superior with respect to the relative effects of the compressor and turbine efficiencies on power output.

Theoretical and Practical Aspects of the Application of Resonant Combustion Chambers in Gas Turbines

This paper discusses theoretical and experimental work carried out to determine the feasibility of a pressure-gain combustion system for gas turbines. Fundamental principles involved in the design of resonant combustors are considered and potential improvements in gas turbine performance are calculated by means of a piston-cylinder analogy. The results indicate that significant improvements in overall thermal efficiency and specific power output can be expected at relatively low pressure ratios but that these improvements become less effective at higher pressure ratios due to the influence of increased compressor delivery temperatures. The results of experimental work on a multiple combustor configuration show that the theoretical performance appears to be attainable and that, subject to further development work, resonant combustion chambers could be utilized to improve gas turbine performance.