Proportional Solenoid Valves (PSV) have been successfully used in the hydraulic industry for many years due to the benefits associated with higher accuracy compared to on/off solenoid valves, and the robustness and cost compared to servo valves. Because the PSV plays an important role in the performance of a hydraulic system, a technique commonly referred to as Condition Monitoring Scheme (CMS) has been used extensively to monitor the progress of faults in the PSV. But before any CMS can be implemented on a system, it needs to be thoroughly tested for its reliability of fault detection since, a failure of the CMS to detect any potential fault can be economically disastrous, and dangerous in terms of the safety of personnel. The motivation of this research was to develop a fault simulator which could reliably and repeatedly induce user defined faults in the PSV and thereby aid in testing the efficacy of the CMS for monitoring such simulated faults.<p>Industry research has revealed that the most common mode of failure in spool valves is an increase in the friction between the spool and valve, due to wear, contamination and dirt, which renders the valve inoperable. In this research, a non-destructive fault simulator was developed which induced artificial friction faults in the PSV. The PSV consisted of two solenoids on the opposite sides of the valve spool by virtue of which, bi-directional position control could be achieved. The PSV with the spool and one of the solenoids was used as the system in which the faults were simulated, and the second solenoid was used an a fault simulator for inducing the desired friction characteristics in the system. <p>The friction characteristics induced in the valve were similar to those in the classical friction curve, i.e., stiction at low velocities and Coulomb and viscous friction at higher velocities. By employing a closed loop position control scheme, one of the solenoids was used to generate a linearly increasing velocity profile by virtue of which the desired friction characteristics could be induced in different velocity regimes. The other solenoid was used to generate the desired friction force. A closed loop force control strategy, which used the feedback from a force transducer, allowed for the accurate control of the friction characteristics. stiction was induced at low velocities by passing the required current in both the solenoids that resulted in no net force on the valve spool. Due to the absence of any driving force the spool was stalled at the desired location, thus achieving the same effect of stiction at low velocities. The coulomb and viscous friction were induced at higher velocities by employing an algorithm which was a function of the spool velocity. Different magnitudes of static, coulomb and viscous friction were induced to achieve the friction characteristics represented by the classical friction curve. Since the change in force characteristics of the valve results in a corresponding change in the current drawn by the position control solenoid, a rudimentary CMS for monitoring the current characteristics is presented. Based on the experimental results and validation using the CMS it was concluded that the fault simulator was able to accurately produce the desired frictional loading on the valve spool and was able to do so with a high degree of repeatability. Proportional Solenoid Valves (PSV) have been successfully used in the hydraulic industry for many years due to the benefits associated with higher accuracy compared to on/off solenoid valves, and the robustness and cost compared to servo valves. Because the PSV plays an important role in the performance of a hydraulic system, a technique commonly referred to as Condition Monitoring Scheme (CMS) has been used extensively to monitor the progress of faults in the PSV. But before any CMS can be implemented on a system, it needs to be thoroughly tested for its reliability of fault detection since, a failure of the CMS to detect any potential fault can be economically disastrous, and dangerous in terms of the safety of personnel. The motivation of this research was to develop a fault simulator which could reliably and repeatedly induce user defined faults in the PSV and thereby aid in testing the efficacy of the CMS for monitoring such simulated faults. Industry research has revealed that the most common mode of failure in spool valves is an increase in the friction between the spool and valve, due to wear, contamination and dirt, which renders the valve inoperable. In this research, a non-destructive fault simulator was developed which induced artificial friction faults in the PSV. The PSV consisted of two solenoids on the opposite sides of the valve spool by virtue of which, bi-directional position control could be achieved.The PSV with the spool and one of the solenoids was used as the system in which the faults were simulated, and the second solenoid was used an a fault simulator for inducing the desired friction characteristics in the system. The friction characteristics induced in the valve were similar to those in the classical friction curve, i.e., stiction at low velocities and Coulomb and viscous friction at higher velocities. By employing a closed loop position control scheme, one of the solenoids was used to generate a linearly increasing velocity profile by virtue of which the desired friction characteristics could be induced in different velocity regimes. The other solenoid was used to generate the desired friction force. A closed loop force control strategy, which used the feedback from a force transducer, allowed for the accurate control of the friction characteristics. stiction was induced at low velocities by passing the required current in both the solenoids that resulted in no net force on the valve spool. Due to the absence of any driving force the spool was stalled at the desired location, thus achieving the same effect of stiction at low velocities. The coulomb and viscous friction were induced at higher velocities by employing an algorithm which was a function of the spool velocity. Different magnitudes of static, coulomb and viscous friction were induced to achieve the friction characteristics represented by the classical friction curve. Since the change in force characteristics of the valve results in a corresponding change in the current drawn by the position control solenoid, a rudimentary CMS for monitoring the current characteristics is presented. Based on the experimental results and validation using the CMS it was concluded that the fault simulator was able to accurately produce the desired frictional loading on the valve spool and was able to do so with a high degree of repeatability.

Proportional Solenoid Valves (PSV) have been successfully used in the hydraulic industry for many years due to the benefits associated with higher accuracy compared to on/off solenoid valves, and the robustness and cost compared to servo valves. Because the PSV plays an important role in the performance of a hydraulic system, a technique commonly referred to as Condition Monitoring Scheme (CMS) has been used extensively to monitor the progress of faults in the PSV. But before any CMS can be implemented on a system, it needs to be thoroughly tested for its reliability of fault detection since, a failure of the CMS to detect any potential fault can be economically disastrous, and dangerous in terms of the safety of personnel. The motivation of this research was to develop a fault simulator which could reliably and repeatedly induce user defined faults in the PSV and thereby aid in testing the efficacy of the CMS for monitoring such simulated faults.<p>Industry research has revealed that the most common mode of failure in spool valves is an increase in the friction between the spool and valve, due to wear, contamination and dirt, which renders the valve inoperable. In this research, a non-destructive fault simulator was developed which induced artificial friction faults in the PSV. The PSV consisted of two solenoids on the opposite sides of the valve spool by virtue of which, bi-directional position control could be achieved. The PSV with the spool and one of the solenoids was used as the system in which the faults were simulated, and the second solenoid was used an a fault simulator for inducing the desired friction characteristics in the system. <p>The friction characteristics induced in the valve were similar to those in the classical friction curve, i.e., stiction at low velocities and Coulomb and viscous friction at higher velocities. By employing a closed loop position control scheme, one of the solenoids was used to generate a linearly increasing velocity profile by virtue of which the desired friction characteristics could be induced in different velocity regimes. The other solenoid was used to generate the desired friction force. A closed loop force control strategy, which used the feedback from a force transducer, allowed for the accurate control of the friction characteristics. stiction was induced at low velocities by passing the required current in both the solenoids that resulted in no net force on the valve spool. Due to the absence of any driving force the spool was stalled at the desired location, thus achieving the same effect of stiction at low velocities. The coulomb and viscous friction were induced at higher velocities by employing an algorithm which was a function of the spool velocity. Different magnitudes of static, coulomb and viscous friction were induced to achieve the friction characteristics represented by the classical friction curve. Since the change in force characteristics of the valve results in a corresponding change in the current drawn by the position control solenoid, a rudimentary CMS for monitoring the current characteristics is presented. Based on the experimental results and validation using the CMS it was concluded that the fault simulator was able to accurately produce the desired frictional loading on the valve spool and was able to do so with a high degree of repeatability. Proportional Solenoid Valves (PSV) have been successfully used in the hydraulic industry for many years due to the benefits associated with higher accuracy compared to on/off solenoid valves, and the robustness and cost compared to servo valves. Because the PSV plays an important role in the performance of a hydraulic system, a technique commonly referred to as Condition Monitoring Scheme (CMS) has been used extensively to monitor the progress of faults in the PSV. But before any CMS can be implemented on a system, it needs to be thoroughly tested for its reliability of fault detection since, a failure of the CMS to detect any potential fault can be economically disastrous, and dangerous in terms of the safety of personnel. The motivation of this research was to develop a fault simulator which could reliably and repeatedly induce user defined faults in the PSV and thereby aid in testing the efficacy of the CMS for monitoring such simulated faults. Industry research has revealed that the most common mode of failure in spool valves is an increase in the friction between the spool and valve, due to wear, contamination and dirt, which renders the valve inoperable. In this research, a non-destructive fault simulator was developed which induced artificial friction faults in the PSV. The PSV consisted of two solenoids on the opposite sides of the valve spool by virtue of which, bi-directional position control could be achieved.The PSV with the spool and one of the solenoids was used as the system in which the faults were simulated, and the second solenoid was used an a fault simulator for inducing the desired friction characteristics in the system. The friction characteristics induced in the valve were similar to those in the classical friction curve, i.e., stiction at low velocities and Coulomb and viscous friction at higher velocities. By employing a closed loop position control scheme, one of the solenoids was used to generate a linearly increasing velocity profile by virtue of which the desired friction characteristics could be induced in different velocity regimes. The other solenoid was used to generate the desired friction force. A closed loop force control strategy, which used the feedback from a force transducer, allowed for the accurate control of the friction characteristics. stiction was induced at low velocities by passing the required current in both the solenoids that resulted in no net force on the valve spool. Due to the absence of any driving force the spool was stalled at the desired location, thus achieving the same effect of stiction at low velocities. The coulomb and viscous friction were induced at higher velocities by employing an algorithm which was a function of the spool velocity. Different magnitudes of static, coulomb and viscous friction were induced to achieve the friction characteristics represented by the classical friction curve. Since the change in force characteristics of the valve results in a corresponding change in the current drawn by the position control solenoid, a rudimentary CMS for monitoring the current characteristics is presented. Based on the experimental results and validation using the CMS it was concluded that the fault simulator was able to accurately produce the desired frictional loading on the valve spool and was able to do so with a high degree of repeatability.

Hybrid solar-Brayton systems utilize both solar thermal energy and supplementary renewable fuels to provide controllable and dispatchable power output, which renders them a promising way to meet the growing energy demand and reduce the carbon footprints. However, existing testing facilities for key components in such hybrid systems often fail to accomplish the testing requirements, hence impeding the improvement of the renewable energy share and the overall efficiency. A novel testing facility is urgently needed in order to thoroughly stimulate and analyze the component characteristics. This research work focuses on the development of a gas turbine simulator as an innovative testing facility for hot, pressurized components in hybrid solar-Brayton systems. The dual-flow choked nozzle based flow control has been proposed, explained, and analyzed in comparison to the single-flow layout. The basic idea of gas turbine simulator has been experimentally implemented and validated on a prototype, verifying its functionality. By incorporating a PLC-based control system, an automated gas turbine simulator has been designed and modified based on the prototype. Its performance with regard to stabilizing boundaries and tracking trajectories has been evaluated by experiments. Based on the experimental results, the gas turbine simulator prototype has proven its ability to establish controllable boundary conditions and migrate operating points for the impinging receiver. Through manual adjustments, excellent quasi-steady state performance has been obtained, with the precision for pressure control reaching ±0.005 bar at ambient temperature and ±0.015 bar at high temperature of 797.1-931.5 °C. The manual operation time has been identified at 23.1 s for establishing the receiver boundaries, and at 70 s for changing operating points. With the help of the proposed control strategy, the automated gas turbine simulator has eliminated the need for manual adjustments, and demonstrated the ability to maintain the safe and convergent operation for the receiver. The performance in boundary condition stabilization has been satisfactory, with enhanced steady-state accuracy comparing to the prototype by virtue of the PID controller. The transient-state fluctuations in pressure control have been effectively restrained within an acceptable region with deviations of ±0.018 bar to ±0.076 bar from the desired 2.400 bar operating pressure. The capability of tracking linear and nonlinear trajectories has also been testified, with the precision level between ±0.023 bar and ±0.037 bar. Finally, in view of the good stability, high precision, and rapid response manifested in the experimental studies, the gas turbine simulator has validated its ability to imitate the steady and transient characteristics of gas turbines on the boundaries of the test section. It also grants the possibilities to conduct control variable studies and wide-range transition studies. The gas turbine simulator is a suitable testing facility for the key components in hybrid solar-Brayton systems. / Hybrid solenergi-Brayton-system använder både solvärmeenergi och kompletterande förnybara bränslen för att ge kontrollerbar och sändbar effekt, vilket gör dem till ett lovande sätt att möta den växande energiefterfrågan och minska koldioxidavtrycken. Men befintliga testanläggningar för nyckelkomponenter i sådana hybridsystem misslyckas ofta med att uppfylla testkraven, vilket hindrar förbättringen av andelen förnybar energi och den totala effektiviteten. En ny testanläggning behövs omgående för att grundligt stimulera och analysera komponentens egenskaper. Detta forskningsarbete fokuserar på utvecklingen av en gasturbinsimulator som en innovativ testanläggning för varma, trycksatta komponenter i hybridsolar-Brayton-system. Den dubbelströms strypta munstycksbaserade flödeskontrollen har föreslagits, förklarats och analyserats i jämförelse med enkelflödeslayouten. Den grundläggande idén med gasturbinsimulator har experimentellt implementerats och validerats på en prototyp, vilket verifierar dess funktionalitet. Genom att införliva ett PLC-baserat styrsystem har en automatiserad gasturbinsimulator designats och modifierats utifrån prototypen. Dess prestanda med avseende på stabilisering av gränser och spårning av banor har utvärderats genom experiment. Baserat på de experimentella resultaten har prototypen av gasturbinsimulatorn bevisat sin förmåga att upprätta kontrollerbara gränsförhållanden och migrera arbetspunkter för den träffande mottagaren. Genom manuella justeringar har man erhållit utmärkt prestanda i nästan konstant tillstånd, med precisionen för tryckkontroll som når ±0,005 bar vid omgivningstemperatur och ±0,015 bar vid hög temperatur på 797,1-931,5 °C. Den manuella drifttiden har identifierats till 23,1 s för att fastställa mottagargränserna och till 70 s för att byta arbetspunkter. Med hjälp av den föreslagna styrstrategin har den automatiserade gasturbinsimulatorn eliminerat behovet av manuella justeringar och visat förmågan att upprätthålla en säker och konvergent drift för mottagaren. Prestandan vid gränstillståndsstabilisering har varit tillfredsställande, med förbättrad steady-state noggrannhet jämfört med prototypen tack vare PID-regulatorn. De transienta tillståndsfluktuationerna i tryckregleringen har effektivt begränsats inom ett acceptabelt område med avvikelser på ±0,018 bar till ±0,076 bar från det önskade 2,400 bar arbetstrycket. Förmågan att spåra linjära och olinjära banor har också vittnats, med precisionsnivån mellan ±0,023 bar och ±0,037 bar. Slutligen, med tanke på den goda stabiliteten, höga precisionen och snabba responsen som manifesteras i de experimentella studierna, har gasturbinsimulatorn validerat sin förmåga att imitera de stabila och transienta egenskaperna hos gasturbiner på gränserna för testsektionen. Det ger också möjlighet att genomföra kontrollvariabelstudier och omfattande övergångsstudier. Gasturbinsimulatorn är en lämplig testanläggning för nyckelkomponenterna i hybridsolar-Brayton-system.