The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Lorenzo Ciuchicchi - One of the best experts on this subject based on the ideXlab platform.
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thermo elasto bulk flow model for labyrinth seals in steam turbines
Tribology International, 2018Co-Authors: Filippo Cangioli, Leonardo Nettis, Paolo Pennacchi, Steven Chatterton, Lorenzo CiuchicchiAbstract:Abstract Over the last few decades, the increasing demand on efficiency and performance for steam turbines has resulted in OEMs operating machines near critical conditions of their structural and thermal capabilities. In this paper, a new thermo-elasto bulk-flow model for labyrinth seals has been introduced. The model includes the bulk-flow model for estimating the dynamic coefficients, heat transfer model for evaluating the temperature distribution in the rotating and stationary parts and structural-mechanics model for calculating the radial growth. By considering a staggered labyrinth seal installed in the balancing drum of a steam turbine, different operating conditions, such as the boundary pressure, rotational speed and inlet pre-Swirl Ratio, as well as the stability of the seal are investigated in this study.
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thermo elasto bulk flow model for labyrinth seals in steam turbines
Tribology International, 2018Co-Authors: Filippo Cangioli, Leonardo Nettis, Paolo Pennacchi, Steven Chatterton, Lorenzo CiuchicchiAbstract:Abstract Over the last few decades, the increasing demand on efficiency and performance for steam turbines has resulted in OEMs operating machines near critical conditions of their structural and thermal capabilities. In this paper, a new thermo-elasto bulk-flow model for labyrinth seals has been introduced. The model includes the bulk-flow model for estimating the dynamic coefficients, heat transfer model for evaluating the temperature distribution in the rotating and stationary parts and structural-mechanics model for calculating the radial growth. By considering a staggered labyrinth seal installed in the balancing drum of a steam turbine, different operating conditions, such as the boundary pressure, rotational speed and inlet pre-Swirl Ratio, as well as the stability of the seal are investigated in this study.
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effect of energy equation in one control volume bulk flow model for the prediction of labyrinth seal dynamic coefficients
Mechanical Systems and Signal Processing, 2018Co-Authors: Filippo Cangioli, Paolo Pennacchi, G Vannini, Lorenzo CiuchicchiAbstract:Abstract The influence of sealing components on the rotordynamic stability of turbomachinery has become a key topic because the oil and gas market is increasingly demanding high rotational speeds and high efficiency. This leads the turbomachinery manufacturers to design higher flexibility Ratios and to reduce the clearance of the seals. Accurate prediction of the effective damping of seals is critical to avoid instability problems; in recent years, “negative-Swirl” Swirl brakes have been used to reverse the circumferential direction of the inlet flow, which changes the sign of the cross-coupled stiffness coefficients and generates stabilizing forces. Experimental tests for a teeth-on-stator labyrinth seal were performed by manufacturers with positive and negative pre-Swirl values to investigate the pre-Swirl effect on the cross-coupled stiffness coefficient. Those results are used as a benchmark in this paper. To analyse the rotor-fluid interaction in the seals, the bulk-flow numeric approach is more time efficient than computational fluid dynamics (CFD). Although the accuracy of the coefficients prediction in bulk-flow models is satisfactory for liquid phase application, the accuracy of the results strongly depends on the operating conditions in the case of the gas phase. In this paper, the authors propose an improvement in the state-of-the-art bulk-flow model by introducing the effect of the energy equation in the zeroth-order solution to better characterize real gas properties due to the enthalpy variation along the seal cavities. The consideRation of the energy equation allows for a better estimation of the coefficients in the case of a negative pre-Swirl Ratio, therefore, it extend the prediction fidelity over a wide range of operating conditions. The numeric results are also compared to the state-of-the-art bulk-flow model, which highlights the improvement in the model.
Filippo Cangioli - One of the best experts on this subject based on the ideXlab platform.
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thermo elasto bulk flow model for labyrinth seals in steam turbines
Tribology International, 2018Co-Authors: Filippo Cangioli, Leonardo Nettis, Paolo Pennacchi, Steven Chatterton, Lorenzo CiuchicchiAbstract:Abstract Over the last few decades, the increasing demand on efficiency and performance for steam turbines has resulted in OEMs operating machines near critical conditions of their structural and thermal capabilities. In this paper, a new thermo-elasto bulk-flow model for labyrinth seals has been introduced. The model includes the bulk-flow model for estimating the dynamic coefficients, heat transfer model for evaluating the temperature distribution in the rotating and stationary parts and structural-mechanics model for calculating the radial growth. By considering a staggered labyrinth seal installed in the balancing drum of a steam turbine, different operating conditions, such as the boundary pressure, rotational speed and inlet pre-Swirl Ratio, as well as the stability of the seal are investigated in this study.
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thermo elasto bulk flow model for labyrinth seals in steam turbines
Tribology International, 2018Co-Authors: Filippo Cangioli, Leonardo Nettis, Paolo Pennacchi, Steven Chatterton, Lorenzo CiuchicchiAbstract:Abstract Over the last few decades, the increasing demand on efficiency and performance for steam turbines has resulted in OEMs operating machines near critical conditions of their structural and thermal capabilities. In this paper, a new thermo-elasto bulk-flow model for labyrinth seals has been introduced. The model includes the bulk-flow model for estimating the dynamic coefficients, heat transfer model for evaluating the temperature distribution in the rotating and stationary parts and structural-mechanics model for calculating the radial growth. By considering a staggered labyrinth seal installed in the balancing drum of a steam turbine, different operating conditions, such as the boundary pressure, rotational speed and inlet pre-Swirl Ratio, as well as the stability of the seal are investigated in this study.
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effect of energy equation in one control volume bulk flow model for the prediction of labyrinth seal dynamic coefficients
Mechanical Systems and Signal Processing, 2018Co-Authors: Filippo Cangioli, Paolo Pennacchi, G Vannini, Lorenzo CiuchicchiAbstract:Abstract The influence of sealing components on the rotordynamic stability of turbomachinery has become a key topic because the oil and gas market is increasingly demanding high rotational speeds and high efficiency. This leads the turbomachinery manufacturers to design higher flexibility Ratios and to reduce the clearance of the seals. Accurate prediction of the effective damping of seals is critical to avoid instability problems; in recent years, “negative-Swirl” Swirl brakes have been used to reverse the circumferential direction of the inlet flow, which changes the sign of the cross-coupled stiffness coefficients and generates stabilizing forces. Experimental tests for a teeth-on-stator labyrinth seal were performed by manufacturers with positive and negative pre-Swirl values to investigate the pre-Swirl effect on the cross-coupled stiffness coefficient. Those results are used as a benchmark in this paper. To analyse the rotor-fluid interaction in the seals, the bulk-flow numeric approach is more time efficient than computational fluid dynamics (CFD). Although the accuracy of the coefficients prediction in bulk-flow models is satisfactory for liquid phase application, the accuracy of the results strongly depends on the operating conditions in the case of the gas phase. In this paper, the authors propose an improvement in the state-of-the-art bulk-flow model by introducing the effect of the energy equation in the zeroth-order solution to better characterize real gas properties due to the enthalpy variation along the seal cavities. The consideRation of the energy equation allows for a better estimation of the coefficients in the case of a negative pre-Swirl Ratio, therefore, it extend the prediction fidelity over a wide range of operating conditions. The numeric results are also compared to the state-of-the-art bulk-flow model, which highlights the improvement in the model.
Paolo Pennacchi - One of the best experts on this subject based on the ideXlab platform.
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thermo elasto bulk flow model for labyrinth seals in steam turbines
Tribology International, 2018Co-Authors: Filippo Cangioli, Leonardo Nettis, Paolo Pennacchi, Steven Chatterton, Lorenzo CiuchicchiAbstract:Abstract Over the last few decades, the increasing demand on efficiency and performance for steam turbines has resulted in OEMs operating machines near critical conditions of their structural and thermal capabilities. In this paper, a new thermo-elasto bulk-flow model for labyrinth seals has been introduced. The model includes the bulk-flow model for estimating the dynamic coefficients, heat transfer model for evaluating the temperature distribution in the rotating and stationary parts and structural-mechanics model for calculating the radial growth. By considering a staggered labyrinth seal installed in the balancing drum of a steam turbine, different operating conditions, such as the boundary pressure, rotational speed and inlet pre-Swirl Ratio, as well as the stability of the seal are investigated in this study.
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thermo elasto bulk flow model for labyrinth seals in steam turbines
Tribology International, 2018Co-Authors: Filippo Cangioli, Leonardo Nettis, Paolo Pennacchi, Steven Chatterton, Lorenzo CiuchicchiAbstract:Abstract Over the last few decades, the increasing demand on efficiency and performance for steam turbines has resulted in OEMs operating machines near critical conditions of their structural and thermal capabilities. In this paper, a new thermo-elasto bulk-flow model for labyrinth seals has been introduced. The model includes the bulk-flow model for estimating the dynamic coefficients, heat transfer model for evaluating the temperature distribution in the rotating and stationary parts and structural-mechanics model for calculating the radial growth. By considering a staggered labyrinth seal installed in the balancing drum of a steam turbine, different operating conditions, such as the boundary pressure, rotational speed and inlet pre-Swirl Ratio, as well as the stability of the seal are investigated in this study.
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effect of energy equation in one control volume bulk flow model for the prediction of labyrinth seal dynamic coefficients
Mechanical Systems and Signal Processing, 2018Co-Authors: Filippo Cangioli, Paolo Pennacchi, G Vannini, Lorenzo CiuchicchiAbstract:Abstract The influence of sealing components on the rotordynamic stability of turbomachinery has become a key topic because the oil and gas market is increasingly demanding high rotational speeds and high efficiency. This leads the turbomachinery manufacturers to design higher flexibility Ratios and to reduce the clearance of the seals. Accurate prediction of the effective damping of seals is critical to avoid instability problems; in recent years, “negative-Swirl” Swirl brakes have been used to reverse the circumferential direction of the inlet flow, which changes the sign of the cross-coupled stiffness coefficients and generates stabilizing forces. Experimental tests for a teeth-on-stator labyrinth seal were performed by manufacturers with positive and negative pre-Swirl values to investigate the pre-Swirl effect on the cross-coupled stiffness coefficient. Those results are used as a benchmark in this paper. To analyse the rotor-fluid interaction in the seals, the bulk-flow numeric approach is more time efficient than computational fluid dynamics (CFD). Although the accuracy of the coefficients prediction in bulk-flow models is satisfactory for liquid phase application, the accuracy of the results strongly depends on the operating conditions in the case of the gas phase. In this paper, the authors propose an improvement in the state-of-the-art bulk-flow model by introducing the effect of the energy equation in the zeroth-order solution to better characterize real gas properties due to the enthalpy variation along the seal cavities. The consideRation of the energy equation allows for a better estimation of the coefficients in the case of a negative pre-Swirl Ratio, therefore, it extend the prediction fidelity over a wide range of operating conditions. The numeric results are also compared to the state-of-the-art bulk-flow model, which highlights the improvement in the model.
Heekoo Moon - One of the best experts on this subject based on the ideXlab platform.
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turbine platform cooling and blade suction surface phantom cooling from simulated Swirl purge flow
Journal of Turbomachinery-transactions of The Asme, 2016Co-Authors: Jiyeon Lee, Jechin Han, Luzeng Zhang, Heekoo MoonAbstract:This paper presents the Swirl purge flow on a platform and a modeled land-based turbine rotor blade suction surface. Pressure-sensitive paint (PSP) mass transfer technique provides detailed film-cooling effectiveness distribution on the platform and phantom cooling effectiveness on the blade suction surface. Experiments were conducted in a low-speed wind tunnel facility with a five-blade linear cascade. The inlet Reynolds number based on the chord length is 250,000. Swirl purge flow is simulated by coolant injection through 50 inclined cylindrical holes ahead of the blade leading edge row. Coolant injections from cylindrical holes pass through nozzle endwall and a dolphin nose axisymmetric contour before reaching the platform and blade suction surface. Different “coolant injection angles” and “coolant injection velocity to cascade inlet velocity” result in various Swirl Ratios to simulate real engine conditions. Simulated Swirl purge flow uses coolant injection angles of 30 deg, 45 deg, and 60 deg to produce Swirl Ratios of 0.4, 0.6, and 0.8, respectively. Traditional purge flow has a coolant injection angle of 90 deg to generate Swirl Ratio of 1. Coolant to mainstream mass flow rate (MFR) Ratio is 0.5%, 1.0%, and 1.5% for all the Swirl Ratios. Coolant to mainstream density Ratio maintains at 1.5 to match engine conditions. Most of the Swirl purge and purge coolant approach the platform; however, a small amount of the coolant migrates to the blade suction surface. Swirl Ratio of 0.4 has the highest relative motion between rotor and coolant and severely decreases film cooling and phantom cooling effectiveness. Higher MFR of 1% and 1.5% cases suffers from apparent decrement of the effectiveness while increasing relative motion.
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influence of mainstream turbulence on turbine blade platform cooling from simulated Swirl purge flow
Applied Thermal Engineering, 2016Co-Authors: Jiyeon Lee, Jechin Han, Luzeng Zhang, Heekoo MoonAbstract:Abstract The paper presents the combined effect of mainstream turbulence intensity and Swirl Ratio on the cooling performance of turbine blade platform and suction surface. Pressure sensitive paint (PSP) mass transfer technique provides detailed cooling effectiveness distribution on platform and suction surface. Experiments have been completed in a low speed wind tunnel facility with a five blade linear cascade. The inlet Reynolds number based on the chord length is 250,000. Coolant to mainstream density Ratio maintains at 1.5 to match engine conditions. Detailed mainstream turbulence intensities for test are Tu (%) = 0.72, 3.1, 6, 8.2, and 13. Swirl Ratios (S) of 1 presents without rotation effect but 0.4 simulates high relative motion between rotor and coolant to represent rotation effect. Coolant to mainstream mass flow rate Ratios are MFR (%) = 0.5, 1.0 and 1.5. Results show that elevated mainstream turbulence intensity increases cooling effectiveness in general. Best cooling performance is observed for high mainstream turbulence intensity of 13% cases no matter with or without rotation effect. Rotation effect reduces coolant capability at higher MFR of 1% and 1.5% cases for tested mainstream turbulence intensities.
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turbine platform cooling and blade suction surface phantom cooling from simulated Swirl purge flow
ASME Turbo Expo 2015: Turbine Technical Conference and Exposition, 2015Co-Authors: Jiyeon Lee, Jechin Han, Luzeng Zhang, Heekoo MoonAbstract:The paper presents the Swirl purge flow on platform and a modeled land-based turbine rotor blade suction surface. Pressure sensitive paint (PSP) mass transfer technique provides detailed film cooling effectiveness distribution on platform and phantom cooling effectiveness on blade suction surface. Experiments have completed in a low speed wind tunnel facility with a five blade linear cascade. The inlet Reynolds number based on the chord length is 250,000. Swirl purge flow is simulated by coolant injection through fifty inclined cylindrical holes ahead of the blade leading edge row. Coolant injections from cylindrical holes go through nozzle endwall and a dolphin nose axisymmetric contour before reach platform and blade suction surface. Different “coolant injection angles” and “coolant injection velocity to cascade inlet velocity” results in various Swirl Ratios to simulate real engine conditions. Simulated Swirl purge flow uses coolant injection angles of 30, 45, and 60 degrees to produce Swirl Ratios of 0.4, 0.6, and 0.8, respectively. Traditional purge flow has coolant injection angle of 90 degree to generate Swirl Ratio of 1. Coolant to mainstream mass flow rate Ratio (MFR) is 0.5%, 1.0% and 1.5% for all Swirl Ratios. Coolant to mainstream density Ratio maintains at 1.5 to match engine conditions. Most of the Swirl purge and purge coolant approaches platform, but small amount of the coolant migrates to blade suction surface. Swirl Ratio of 0.4 has highest relative motion between rotor and coolant and severely decreases film cooling and phantom cooling effectiveness. Higher MFR of 1% and 1.5% cases suffer from apparent decrement of the effectiveness while increasing relative motion.Copyright © 2015 by ASME
David L S Hung - One of the best experts on this subject based on the ideXlab platform.
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influence of Swirl Ratio on fuel distribution and cyclic variation under flash boiling conditions in a spark ignition direct injection gasoline engine
Energy Conversion and Management, 2017Co-Authors: Jie Yang, David L S Hung, Xue DongAbstract:Abstract One effective way of suppressing the cycle-to-cycle variation in engine is to design a combustion system that is robust to the root causes of engine variation over the entire engine working process. Flash boiling has been demonstrated as an ideal technique to produce stable fuel spray. But the geneRation of stable intake flow and fuel mixture remains challenging. In this study, to evaluate the capability of enhanced Swirl flow to produce repeatable fuel mixture formation, the fuel distribution inside a single cylinder optical engine under two Swirl Ratios were measured using laser induced fluorescence technique. The Swirl Ratio was regulated by a Swirl control valve installed in one of the intake ports. A 266 nm wavelength laser sheet from a frequency-quadrupled laser was directed into the optical engine through the quartz liner 15 mm below the tip of the spark plug. The fluorescence signal from the polycyclic aromatic hydrocarbon in gasoline was collected by applying a 320–420 nm band pass filter mounted in front of an intensified charge coupled device camera. Test results show that the in-cylinder fuel distribution is strongly influenced by the Swirl Ratio. Specifically, under high Swirl condition, the fuel is mainly concentrated on the left side of the combustion chamber. While under the low Swirl flow, fuel is distributed more randomly over the observing plane. This agrees well with the measurements of the stable flame location. Additionally, the cycle-to-cycle variation of the fuel distribution were analyzed. Results show that well organized fuel mixture with lower cycle-to-cycle variation is achieved by enhanced Swirl flow.
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characterization of the effect of intake air Swirl motion on time resolved in cylinder flow field using quadruple proper orthogonal decomposition
Energy Conversion and Management, 2016Co-Authors: Hanyang Zhuang, David L S HungAbstract:The control of intake air Swirl motion is often used in spark-ignition direct-injection (SIDI) engine to improve its in-cylinder fuel–air mixing process especially under engine idle and low load conditions. In this experimental investigation, a novel technique combining the time-resolved particle image velocimetry (PIV) with quadruple proper orthogonal decomposition (POD) is implemented to analyze the time-resolved in-cylinder velocity measurements in an optically-accessible SIDI engine. The intake air Swirl motion is introduced into the engine cylinder by a control valve installed in one of two air intake ports. Experimental results show that a strong linear correlation exists between the intake flow Swirl Ratio and vorticity flow field in the cylinder. This correlation ensures high data reliability of Swirl motion control and provides a novel basis to directly compare the flow field measurements under different Swirl Ratio conditions. The quadruple proper orthogonal decomposition analysis is then applied to the velocity flow fields to separate the highly dynamic in-cylinder flow characteristics into four distinct categories: (1) dominant flow structure; (2) coherent structure; (3) turbulent structure; and (4) noise structure. The results show that the dominant flow structure varies strongly with Swirl Ratio, and its kinetic energy is also directly related to the Swirl Ratio. The coherent structure captures the large scale flow characteristics, but its kinetic energy is much lower and exhibits larger cycle-to-cycle variations. The turbulent structure contains similar level of kinetic energy at different Swirl Ratios but without much cycle-to-cycle variation. Finally, the noise structure contains very low kinetic energy which only alters the dynamic nature of the flow field slightly. In summary, the effect of Swirl Ratio on in-cylinder flow field is mostly captured by the dominant flow structure and partially captured by the coherent flow structure. The turbulent flow structure can characterize the high-order flow variation. The noise structure can be neglected due to the low energy captured.
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investigation of Swirl Ratio impact on in cylinder flow in an sidi optical engine
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2015Co-Authors: Hanyang Zhuang, David L S Hung, Jie Yang, Shaoxiong TianAbstract:Advanced powertrain technologies have improved engine performance with higher power output, lower exhaust emission, and better controllability. Chief among them is the development of spark-ignition direct-injection (SIDI) engines in which the in-cylinder processes control the air flow motion, fuel-air mixture formation, combustion, and soot formation. Specifically, intake air with strong Swirl motion is usually introduced to form a directional in-cylinder flow field. This approach improves the mixing process of air and fuel as well as the propagation of flame. In this study, the effect of intake air Swirl on in-cylinder flow characteristics was experimentally investigated. High speed particle image velocimetry (PIV) was conducted in an optical SIDI engine to record the flow field on a Swirl plane. The intake air Swirl motion was achieved by adjusting the opening of a Swirl Ratio control valve which was installed in one of the two intake ports in the optical engine. Ten opening angles of the Swirl Ratio control valve were adjusted to produce an intake Swirl Ratio from 0.55 to 5.68. The flow structures at the same crank angle degree, but under different Swirl Ratio, were compared and analyzed using proper orthogonal decomposition (POD). The flow dominant structures and variation structures were interpreted by different POD modes. The first POD mode captured the most dominant flow field structure characteristics; the corresponding mode coefficients showed good linearity with the measured Swirl Ratio at the compression stroke when the flow was Swirling and steady. During the intake stroke, strong intake air motion took place, and the structures and coefficients of the first modes varied along different Swirl Ratio. These modes captured the flow properties affected by the intake Swirl motion. Meanwhile, the second and higher modes captured the variation feature of the flow at various crank angle degrees. In summary, this paper demonstrated a promising approach of using POD to interpret the effectiveness of Swirl control valve on in-cylinder Swirl flow characteristics, providing better understanding for engine intake system design and optimization.Copyright © 2015 by ASME
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cycle to cycle variation analysis of early flame propagation in engine cylinder using proper orthogonal decomposition
Experimental Thermal and Fluid Science, 2014Co-Authors: Hao Chen, David L S Hung, Hanyang ZhuangAbstract:Abstract Experimental investigations on the cycle-to-cycle variations of early flame propagation were conducted at two intake air Swirl Ratio of 0.55 and 5.68 in a single-cylinder spark-ignition direct-injection (SIDI) optical engine. Both the crank-angle resolved flame images through the quartz insert in the piston and the in-cylinder pressure were simultaneously recorded for 250 consecutive cycles. An algorithm based on the cross-correlation of flame pattern was implemented to compute the two-dimensional velocity fields representing an early flame propagation. Afterwards, the proper orthogonal decomposition (POD) was performed to access the cycle-to-cycle variations of flame propagation. During early flame formation, the uncertainty of velocity was evaluated to be less than 5%. The velocity fields of early flame propagation were significantly affected by in-cylinder air flow. Increasing the Swirl Ratio from 0.55 to 5.68 augmented the average early flame propagation speed from 2.1 m/s to 3.2 m/s, and the COV of flame speed was reduced from 49.7% to 25.1%. Good correlations were identified between early flame speed and the pressure-derived results. Similar magnitude of reduction in COV (coefficient of variation) of IMEP (indicated mean efficient pressure) & PP was also found. The coefficients of POD mode 1 were found to represent the flame speed, and the remaining higher POD modes were related to the fluctuation in kinetic energy. The POD coefficients showed good correlations with the pressure-derived results such as CA05 (5% of total heat release) & PP (peak pressure). The weak spiral flow pattern, observed within the flame, was only found in higher POD modes. In summary, using the coefficients and modes of POD, the average and fluctuating parts of early flame propagation can be resolved, thereby providing more quantitative information of the cycle-to-cycle variation during the early combustion process in an engine cylinder.
