Ion Current Sensor for Gas Turbine Condition Dynamical Monitoring: Modeling and Characterization

This paper aims to thoroughly investigate the potential of ion current measurements in the context of combustion process monitoring in gas turbines. The study is targeted at characterizing the dynamic behavior of a typical ion-current measurement system based on a spark-plug. Starting from the preliminary study published in a previous work, the authors propose a refined model of the electrode (spark plug), based on the Langmuir probe theory, that incorporates the physical surface effects and proposes an optimized design of the conditioning electronics, which exploits a low frequency AC square wave biasing of the electrodes and allows for compensating some relevant parasitic effects. The authors present experimental results obtained in the laboratory, which allow for the evaluation of the validity of the model and the interpreting of the characteristics of the measurement signal. Finally, measurements carried out in the field on an industrial combustor are presented. The results confirm that the charged chemical species density sensed by the proposed measurement system and related to the mean value of the output signal is an indicator of the ‘average’ combustion process conditions in terms e.g., of air/fuel ratio, whereas the high frequency spectral component of the measured signal can give information related to the turbulent regime and to the presence of pressure pulsations. Results obtained with a prototype system demonstrated an achievable resolution of about 5 Pa on the estimated amplitude, even under small biasing voltage (22.5 V) and an estimated bandwidth of 10 kHz.

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Analysis and Research on the Influence Factors of the Spark Plug Ion Current in Spark Ignition Engine

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1070-1072.1831 ◽

2014 ◽

Vol 1070-1072 ◽

pp. 1831-1834

Author(s):

Chang Qing Song ◽

Jun Li ◽

Da Wei Qu

Keyword(s):

Bias Voltage ◽

Combustion Process ◽

Influence Factors ◽

Spark Ignition Engine ◽

Ion Current ◽

Current Signal ◽

Gas Plasma ◽

Spark Plug ◽

Engine Combustion ◽

Analysis System

The spark plug ion current signal carries abundant information about the engine combustion process. Real-time acquisition of the spark plug ion current signal can effectively extract the characteristic parameters, then enhance the power, fuel economy and emissions of the engine. The paper analyzed the influence factors of ion current, designed an acquisition and analysis system of spark plug ion current signal, and mainly studied the influence of spark plug gap and bias voltage on ion current signal in a six-cylinder four-stroke gas engine. The results show that the bias voltage and the spark plug gap have a great impact on the spark plug ion current signal. The ion current signal intensity is directly proportional to the bias voltage applied cross the spark plug, and inversely proportional to the spark plug gap. Results also indicates that the ion current is directly proportional to the mobility and concentration of charged particles in burned gas plasma.

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Optical Investigation of a Partial Fuel Stratification Strategy to Stabilize Overall Lean Operation of a DISI Engine Fueled with Gasoline and E30

Energies ◽

10.3390/en14020396 ◽

2021 ◽

Vol 14 (2) ◽

pp. 396

Author(s):

Cinzia Tornatore ◽

Magnus Sjöberg

Keyword(s):

Volume Fraction ◽

Direct Injection ◽

Combustion Process ◽

Pilot Injection ◽

Optical Investigation ◽

Flame Kernel ◽

Lean Combustion ◽

Fuel Stratification ◽

Spark Plug ◽

Initial Flame

This paper offers new insights into a partial fuel stratification (PFS) combustion strategy that has proven to be effective at stabilizing overall lean combustion in direct injection spark ignition engines. To this aim, high spatial and temporal resolution optical diagnostics were applied in an optically accessible engine working in PFS mode for two fuels and two different durations of pilot injection at the time of spark: 210 µs and 330 µs for E30 (gasoline blended with ethanol by 30% volume fraction) and gasoline, respectively. In both conditions, early injections during the intake stroke were used to generate a well-mixed lean background. The results were compared to rich, stoichiometric and lean well-mixed combustion with different spark timings. In the PFS combustion process, it was possible to detect a non-spherical and highly wrinkled blue flame, coupled with yellow diffusive flames due to the combustion of rich zones near the spark plug. The initial flame spread for both PFS cases was faster compared to any of the well-mixed cases (lean, stoichiometric and rich), suggesting that the flame propagation for PFS is enhanced by both enrichment and enhanced local turbulence caused by the pilot injection. Different spray evolutions for the two pilot injection durations were found to strongly influence the flame kernel inception and propagation. PFS with pilot durations of 210 µs and 330 µs showed some differences in terms of shapes of the flame front and in terms of extension of diffusive flames. Yet, both cases were highly repeatable.

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Comprehensive Thermodynamic Analysis of the Humphrey Cycle for Gas Turbines with Pressure Gain Combustion

Energies ◽

10.3390/en11123521 ◽

2018 ◽

Vol 11 (12) ◽

pp. 3521 ◽

Cited By ~ 5

Author(s):

Panagiotis Stathopoulos

Keyword(s):

Gas Turbine ◽

Gas Turbines ◽

Combustion Process ◽

Ideal Gas ◽

Point Of View ◽

Pressure Gain Combustion ◽

Combustion Technology ◽

Secondary Air ◽

And Performance ◽

The Impact

Conventional gas turbines are approaching their efficiency limits and performance gains are becoming increasingly difficult to achieve. Pressure Gain Combustion (PGC) has emerged as a very promising technology in this respect, due to the higher thermal efficiency of the respective ideal gas turbine thermodynamic cycles. Up to date, only very simplified models of open cycle gas turbines with pressure gain combustion have been considered. However, the integration of a fundamentally different combustion technology will be inherently connected with additional losses. Entropy generation in the combustion process, combustor inlet pressure loss (a central issue for pressure gain combustors), and the impact of PGC on the secondary air system (especially blade cooling) are all very important parameters that have been neglected. The current work uses the Humphrey cycle in an attempt to address all these issues in order to provide gas turbine component designers with benchmark efficiency values for individual components of gas turbines with PGC. The analysis concludes with some recommendations for the best strategy to integrate turbine expanders with PGC combustors. This is done from a purely thermodynamic point of view, again with the goal to deliver design benchmark values for a more realistic interpretation of the cycle.

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Development and Fabrication of Silicon Nitride Components for Ceramic Gas Turbine

Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; IGTI Scholar Award ◽

10.1115/97-gt-067 ◽

1997 ◽

Author(s):

Keisuke Makino ◽

Ken-Ichi Mizuno ◽

Toru Shimamori

Keyword(s):

High Temperature ◽

Silicon Nitride ◽

Gas Turbine ◽

Gas Turbines ◽

Turbine Blades ◽

High Strength ◽

Inlet Temperature ◽

Turbine Inlet Temperature ◽

Spark Plug ◽

Power Turbine

NGK Spark Plug Co., Ltd. has been developing various silicon nitride materials, and the technology for fabricating components for ceramic gas turbines (CGT) using theses materials. We are supplying silicon nitride material components for the project to develop 300 kW class CGT for co-generation in Japan. EC-152 was developed for components that require high strength at high temperature, such as turbine blades and turbine nozzles. In order to adapt the increasing of the turbine inlet temperature (TIT) up to 1,350 °C in accordance with the project goals, we developed two silicon nitride materials with further unproved properties: ST-1 and ST-2. ST-1 has a higher strength than EC-152 and is suitable for first stage turbine blades and power turbine blades. ST-2 has higher oxidation resistance than EC-152 and is suitable for power turbine nozzles. In this paper, we report on the properties of these materials, and present the results of evaluations of these materials when they are actually used for CGT components such as first stage turbine blades and power turbine nozzles.

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Study of High Load Operation Limit Expansion for Gasoline Compression Ignition Engines

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.1805548 ◽

2006 ◽

Vol 128 (2) ◽

pp. 377-387 ◽

Cited By ~ 24

Author(s):

Koudai Yoshizawa ◽

Atsushi Teraji ◽

Hiroshi Miyakubo ◽

Koichi Yamaguchi ◽

Tomonori Urushihara

Keyword(s):

Fuel Injection ◽

Control Method ◽

Combustion Process ◽

High Load ◽

Compression Ignition ◽

Ignition Timing ◽

Timing Control ◽

Load Range ◽

Compression Ignition Engines ◽

Spark Plug

In this research, combustion characteristics of gasoline compression ignition engines have been analyzed numerically and experimentally with the aim of expanding the high load operation limit. The mechanism limiting high load operation under homogeneous charge compression ignition (HCCI) combustion was clarified. It was confirmed that retarding the combustion timing from top dead center (TDC) is an effective way to prevent knocking. However, with retarded combustion, combustion timing is substantially influenced by cycle-to-cycle variation of in-cylinder conditions. Therefore, an ignition timing control method is required to achieve stable retarded combustion. Using numerical analysis, it was found that ignition timing control could be achieved by creating a fuel-rich zone at the center of the cylinder. The fuel-rich zone works as an ignition source to ignite the surrounding fuel-lean zone. In this way, combustion consists of two separate auto-ignitions and is thus called two-step combustion. In the simulation, the high load operation limit was expanded using two-step combustion. An engine system identical to a direct-injection gasoline (DIG) engine was then used to validate two-step combustion experimentally. An air-fuel distribution was created by splitting fuel injection into first and second injections. The spark plug was used to ignite the first combustion. This combustion process might better be called spark-ignited compression ignition combustion (SI-CI combustion). Using the spark plug, stable two-step combustion was achieved, thereby validating a means of expanding the operation limit of gasoline compression ignition engines toward a higher load range.

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Effects of H2 Addition to CNG Blends on Cycle-to-Cycle and Cylinder-to-Cylinder Combustion Variation in an SI Engine

ASME 2012 Internal Combustion Engine Division Spring Technical Conference ◽

10.1115/ices2012-81187 ◽

2012 ◽

Cited By ~ 1

Author(s):

Mirko Baratta ◽

Stefano d’Ambrosio ◽

Daniela Misul ◽

Ezio Spessa

Keyword(s):

Diagnostic Tool ◽

Combustion Process ◽

Experimental Tests ◽

Test Point ◽

Pollutant Emissions ◽

Engine Operation ◽

Pressure Transducers ◽

Rate Analysis ◽

Spark Plug ◽

Wide Range

An experimental investigation and a burning-rate analysis have been performed on a production 1.4 liter CNG (compressed natural gas) engine fueled with methane-hydrogen blends. The engine features a pent-roof combustion chamber, four valves per cylinder and a centrally located spark plug. The experimental tests have been carried out in order to quantify the cycle-to-cycle and the cylinder-to-cylinder combustion variation. Therefore, the engine has been equipped with four dedicated piezoelectric pressure transducers placed on each cylinder and located by the spark plug. At each test point, in-cylinder pressure, fuel consumption, induced air mass flow rate, pressure and temperature at different locations on the engine intake and exhaust systems as well as ‘engine-out’ pollutant emissions have been measured. The signals correlated to the engine operation have been acquired by means of a National Instruments PXI-DAQ system and a home developed software. The acquired data have then been processed through a combustion diagnostic tool resulting from the integration of an original multizone thermodynamic model with a CAD procedure for the evaluation of the burned-gas front geometry. The diagnostic tool allows the burning velocities to be computed. The tests have been performed over a wide range of engine speeds, loads and relative air-fuel ratios (up to the lean operation). For stoichiometric operation, the addition of hydrogen to CNG has produced a bsfc reduction ranging between 2 to 7% and a bsTHC decrease up to the 40%. These benefits have appeared to be even higher for lean mixtures. Moreover, hydrogen has shown to significantly enhance the combustion process, thus leading to a sensibly lower cycle-to-cycle variability. As a matter of fact, hydrogen addition has generally resulted into extended operation up to RAFR = 1.8. Still, a discrepancy in the abovementioned conclusions was observed depending on the engine cylinder considered.

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Laser-Based Measurement of Over Dimensional Freight Rail Shipments

2012 Joint Rail Conference ◽

10.1115/jrc2012-74065 ◽

2012 ◽

Author(s):

Bryan W. Schlake ◽

Brian S. Daniel ◽

Ron Voorheis

Keyword(s):

Measurement System ◽

Human Error ◽

Cost Effective ◽

Measuring System ◽

Prototype System ◽

Reference Target ◽

Potential Benefits ◽

Multiple Measurements ◽

Current Measuring ◽

Time Required

In pursuit of improved safety, Norfolk Southern Corp. (NS) has partnered with Amberg Technologies to explore the potential benefits of a laser-based measurement system for measuring over dimensional freight rail shipments. Shipments that do not fall within a standard geometric envelope, denoted as Plate B in the Association of American Railroads (AAR) Open Top Loading Rules [1], are considered to be over dimensional, or High-Wide Loads (HWLs). Extending beyond the limits of the Plate B diagram, these loads are not permitted in unrestricted interchange service. Instead, they must be measured both at points of origin and at interchange points. For US Class I Railroads, the de facto method for measuring HWLs requires mechanical personnel to either climb on the equipment or use a ladder and physically measure the overall height and width of the load. Using a tape measure, plumb line, and 6-foot level, car inspectors, or carmen, must often make multiple measurements to determine the height or width of a critical point on the load. The summation of these measurements can be subject to mathematical human error. In addition to the inherent limitations with regards to accuracy and efficiency, this method of measurement presents considerable safety challenges. The objective of the project was to develop a portable, cost-effective and accurate measurement system to improve the day-to-day operational process of measuring HWLs and reduce human exposure to railyard hazards. Norfolk Southern worked closely with Amberg Technologies to provide a clear overview of the current measuring methods, requirements, challenges and risks associated with HWLs. Amberg then developed a prototype system (with patent pending) and successful tests have been completed at both a point of origin for NS shipments and at a location where HWLs are received at interchange. The measuring system consists of a tripod mounted laser, a specially designed track reference target (TRT) and software designed specifically for HWL measurements. The system allows car inspectors to take measurements from a safe, strategic location away from the car. As a result, this system eliminates the need to climb on the equipment or a ladder and greatly reduces the amount of time spent on and around live tracks. In addition, initial tests indicate that this technology reduces the labor time required to measure HWLs by as much as one half while improving measurement accuracy. These tests have demonstrated that a laser-based system has the potential to greatly improve the safety, efficiency and accuracy associated with measuring HWLs.

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Investigating Gas Turbine Internal Cooling Using Supercritical CO2 at High Reynolds Numbers for Direct Fired Cycle Applications

10.1115/gt2021-59630 ◽

2021 ◽

Author(s):

Matthew Searle ◽

Arnab Roy ◽

James Black ◽

Doug Straub ◽

Sridharan Ramesh

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Nusselt Number ◽

Gas Turbines ◽

Cfd Simulation ◽

Reynolds Numbers ◽

Navier Stokes ◽

Process Conditions ◽

Internal Cooling ◽

Air Breathing

Abstract In this paper, experimental and numerical investigations of three variants of internal cooling configurations — dimples only, ribs only and ribs with dimples have been explored at process conditions (96°C and 207bar) with sCO2 as the coolant. The designs were chosen based on a review of advanced internal cooling features typically used for air-breathing gas turbines. The experimental study described in this paper utilizes additively manufactured square channels with the cooling features over a range of Reynolds number from 80,000 to 250,000. Nusselt number is calculated in the experiments utilizing the Wilson Plot method and three heat transfer characteristics — augmentation in Nusselt number, friction factor and overall Thermal Performance Factor (TPF) are reported. To explore the effect of surface roughness introduced due to additive manufacturing, two baseline channel flow cases are considered — a conventional smooth tube and an additively manufactured square tube. A companion computational fluid dynamics (CFD) simulation is also performed for the corresponding cooling configurations reported in the experiments using the Reynolds Averaged Navier Stokes (RANS) based turbulence model. Both experimental and computational results show increasing Nusselt number augmentation as higher Reynolds numbers are approached, whereas prior work on internal cooling of air-breathing gas turbines predict a decay in the heat transfer enhancement as Reynolds number increases. Comparing cooling features, it is observed that the “ribs only” and “ribs with dimples” configurations exhibit higher Nusselt number augmentation at all Reynolds numbers compared to the “dimples only” and the “no features” configurations. However, the frictional losses are almost an order of magnitude higher in presence of ribs.

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