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- Comparative Energy-Exergy-Entransy Assessment of Combined Heat and Power Cogeneration in Organic Rankine Cycle Systems
- Kyoung Hoon Kim, Kyoungjin Kim
- Thermodynamic performances of a combined heat and power (CHP) cogeneration system using organic Rankine cycle (ORC) are investigated based on energy, exergy, …
- Thermodynamic performances of a combined heat and power (CHP) cogeneration system using organic Rankine cycle (ORC) are investigated based on energy, exergy, and entransy principles. The present system comprises of an ORC driven by a low-grade heat source and a process heater in a parallel circuit configuration. The entransy balance equations including entransy work, entransy dissipation, and entransy loss are established, which are consistent with those of energy and exergy. Several forms of efficiencies and composition ratios such as exergy destructions, entransy dissipations, and losses are introduced as well. Influences of key system parameters such as source temperature, turbine inlet pressure, and selection of different working fluids on the system performances are analyzed. Present results show that energy, exergy, and entransy performances are greatly influenced by the system parameters and working fluid. In addition, entransy analysis shows different results from energy or exergy analyses, and in some situations, it shows existence of optimal points, which do not occur in energy or exergy analyses. + COLLAPSE
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- Numerical Investigation of Heat Transfer and Flow Characteristics in Pin Arrays Inclined in Alternate Directions
- Hye-bin Kim, Yeong-taek Oh, Kui-soon Kim
- For thermal-structural weakness, the pin-fin arrays have been widely used in the trailing edge of the turbine. In the pin-fin, the heat …
- For thermal-structural weakness, the pin-fin arrays have been widely used in the trailing edge of the turbine. In the pin-fin, the heat transfer is concentrated in the front of the pin, but the backside of the pin has lower heat transfer performance. This high heat load leads to the prominent problems, such as thermal stress and thermal fatigue. This present study numerically investigated the flow characteristics and heat transfer performance of the inclined pin-fin arrays in the alternate directions. The flow field and heat transfer of inclined pin-fin arrays were simulated by using commercial software, ANSYS FLUENT with SST k-ω turbulence model. In the inclined pin-fin arrays, the presence of jet-like flow caused by the counter-rotating vortices enhanced the heat transfer performance of the endwalls and the backside of cylinder and reduced the pressure loss. Moreover, the heat transfer uniformity of all inclined pin-fin arrays was superior to that of general pin-fin arrays. At Re=30000, pin inclination θ=30° increased heat transfer performance by up to 11.9% and decreased friction factor by up to 16.7%, which corresponded to an increase in the thermo-hydraulic performance by up to 18.9% compared to the baseline. This research indicates that pin-fin arrays inclined in the alternate directions had a great potential to improve thermo-hydraulic performance and heat transfer uniformity. + COLLAPSE
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- Numerical Study on Crude Oil Coking and Fouling for Turbulent Multiphase Flows in a Serpentine Pipe
- Seon Myeong Park, Tae Seon Park
- The crude oil coking and fouling in a serpentine pipe are numerically investigated. The serpentine pipe is a sequence of parallel straight …
- The crude oil coking and fouling in a serpentine pipe are numerically investigated. The serpentine pipe is a sequence of parallel straight pipe segments connected by U-shaped bends. The multiphase numerical procedure is constructed within the Eulerian framework based on a continuous liquid phase and dispersed phases of gas and solid. The crude oil is assumed to be composed of six pseudo-components and the simplified reaction is adopted to predict the thermal cracking. The vortical structure due to the centrifugal force is observed at the channel bends. The enhancing effect of heat and mass transfer is reversed as the fluid flows from one bend to the another. Based on the flow structures, and the coke formation are predicted and discussed. + COLLAPSE
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- A Study on the Engine System Analysis Program for an Expander Cycle Liquid Rocket Engine
- Sewon Choi, Insang Moon
- The performance of an expander cycle rocket engine that employs liquid methane as fuel was predicted in this study. The preliminary requirements …
- The performance of an expander cycle rocket engine that employs liquid methane as fuel was predicted in this study. The preliminary requirements of the engine were predetermined, and the specifications of each component were determined by power balance analysis with the given engine requirements. A thrust of 3 tonf was considered, and the cooling scheme was simplified to only use regenerative cooling. The cooling channels were assumed to be one-dimensional axisymmetric. The temperature change of the coolant inside the channels was predicted with heat flux analysis. The properties of the combustion gas were obtained by Chemical Equilibrium Analysis (CEA). Thereafter, a power balancing calculation was performed on the engine with 3 tonf of thrust, and chamber pressure of up to 30 bar could be reached. In addition, a study was conducted on the changes in the engine system according to the pressure ratio of the turbine. + COLLAPSE
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- Comparison of the Semi-empirical Heat Transfer Coefficient for a Liquid Rocket Nozzle with Regenerative Cooling Jacket
- Jongmin Shin, Tae-Seong Roh, Hyoung Jin Lee
- The heat transfer phenomenon of a liquid rocket engine has been studied using various equations for heat transfer coefficients. The heat transfer …
- The heat transfer phenomenon of a liquid rocket engine has been studied using various equations for heat transfer coefficients. The heat transfer coefficient can be calculated using Prandtl-Taylor analogy and Bartz’s empirical equation, and its variations. Through 1D analysis of a liquid rocket engine with a regenerative cooling jacket, the effects of heat transfer coefficients with various semi-empirical equations were analyzed. The difference in heat transfer coefficient affects the heat transfer such as heat flux, gas-side wall temperature, pressure of coolant, and temperature of the coolant. The analysis results were compared to the result by CFD simulation to evaluate the characteristics of semi-empirical equations. The results showed that the heat transfer of a nozzle with regenerative cooling jacket could be simulated well through 1D cooling channel analysis. In addition, the modified Bartz equation showed the best result among various empirical equations. + COLLAPSE
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- Self-Excited Instabilities of Two Interacting Lean-Premixed Flames with Asymmetric Swirl Number
- Jiho Lee, Kyu Tae Kim
- When several swirl-stabilized flames are narrowly spaced in a low-emission gas turbine combustor, neighboring flames will interact. Understanding the response characteristics of …
- When several swirl-stabilized flames are narrowly spaced in a low-emission gas turbine combustor, neighboring flames will interact. Understanding the response characteristics of the interacting flames is essential to control the development of self-excited combustion dynamics. The present study is concerned in particular with the influence of swirl flow parameters – relative rotational direction and swirl number combination – on the system’s thermoacoustic response. Phase-resolved CH* chemiluminescence imaging, OH Planar Laser Induced Fluorescence (PLIF), acoustic pressure, and global heat release rate measurements were performed to study the flame dynamics subjected to co-rotating and counter-rotating swirl arrangements with symmetric and asymmetric swirl number distributions. These parameters were found to exert a remarkable influence on the development of self- excited combustion instability. Our results suggest that counter-rotating swirl configurations, in which adjacent tangential streams flow in the same direction in the interaction region, are more effective to limit the growth of the instability for all swirl number combinations. Instantaneous flame front images reveal that the counter-rotating swirl flame interaction causes the two adjacent flames to stabilize in both the inner and outer shear layers, leading to the formation of the well-known “M” structure. By contrast, the interaction induced by co-rotating swirl flow tends to disturb the flame anchoring at the outer shear layers of each flame, due to the emergence of a large-scale flame front deformation, even under unforced conditions. Impingement of two opposed tangential jets is thought to be linked to the generation of disturbances, which in turn affect stabilization mechanisms and the dynamics of two interacting swirl flames. + COLLAPSE
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- Study on the Performance Characteristics of Interior Ballistics with Configurations and Arrangement of Solid Propellant Grain
- Seok-Hwan Oh, Dongwon Kang, Hyoung Jin Lee, Eun Mi Kim, Tae-Seong Roh
- The effects of interior ballistics(IB) with propellant configurations and arrangements have been studied to decrease maximum pressure in the barrel. In this …
- The effects of interior ballistics(IB) with propellant configurations and arrangements have been studied to decrease maximum pressure in the barrel. In this study, several types of propellant configurations have been used. The in-house 1-D IB code with the Eulerian-Lagrangian approach has been developed for the study. The unsteady compressible IB code using SIMPLE algorithm and SMART scheme has been developed. The ghost-cell extrapolation method has been applied for the moving boundary with the projectile movement. The results showed that the 7- perforated grain type has the highest maximum pressure and the fastest muzzle velocity. However, the weak point of this is the most increased maximum pressure, which may damage the gun barrel. Among the cases with the arrangement of grain types, the combination using the propellant configurations with similar burning surface area have shown that the performance is not varied largely, however the cases using the 7-perforated grain type have revealed different results. The muzzle velocity in the region near the base has shown to be fastest, and the pressure difference between the breech and the base has appeared to be lowest when the 7- perforated grain was used in the combination of propellant types. The cases using the 7-perforated grain configuration in the region near the base are, therefore, more profitable to improve the performance and property of the interior ballistics. + COLLAPSE
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- Insights into Combustion and Thermal Decomposition Behaviour of Electric Solid Propellants
- Kanagaraj Gnanaprakash, Jai-ick Yoh
- Recently, there is a growing interest in the development of electric solid propellants (ESPs) because they offer multiple start/stop operations and variable …
- Recently, there is a growing interest in the development of electric solid propellants (ESPs) because they offer multiple start/stop operations and variable combustion rates at different electrical power. However, the understanding of complex reaction mechanisms involved in decomposition/combustion of these ESPs is still limited. The present study attempts to obtain insights into the thermal decomposition and combustion behaviour of ESPs based on lithium perchlorate (LP) oxidizer and poly vinyl alcohol (PVA) binder, and to further investigate the influence of tungsten (W) at 15% as a metal additive. Different parameters such as heat of reaction, mass loss, and combustion rates are obtained for metallized ESP- M15 and compared with the non-metallized baseline ESP. The heat release and mass loss from the overall decomposition reaction of baseline ESP are obtained as 3729 J/g and 51%, respectively. Addition of W decreases this net heat release by 43% and mass loss by 29% for ESP-M15, when compared to the baseline case. Combustion rates of both ESPs increase considerably with the applied initial voltage in the range of 100-500 V. Furthermore, inclusion of W in ESPs enhances their combustion rates by 4.6 times at 100 V and by 1.3 times at 500 V. This suggests that substantial oxidation of W at actual burning conditions improves the combustion rates of ESPs, whereas such process may not be significant at low temperatures of 30-600 °C in thermal experiments, thus reducing the heat release of metallized formulation relative to the baseline propellant. + COLLAPSE
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- Quantification of Material Explosive Power in Blasting Cap Test
- Ju Won Kim, Wonjae Yoon, Hong Seop Ban, Yehyun Kim, Sejin Kwon
- The blasting cap test is utilized to evaluate the explosion potential of propellants by examining the degree of damage and deformation of …
- The blasting cap test is utilized to evaluate the explosion potential of propellants by examining the degree of damage and deformation of the aluminium tube. The explosion hazard level is divided into three categories: safe, low explosion, and high explosion. However, this qualitative categorization has a limitation that it is not based on an actual measurement of explosion quantities. To overcome this, we carried out quantitative internal pressure measurement by mounting a pressure sensor on the outer drum. It was confirmed that the present blasting cap test configuration can effectively measure the explosive pressure for the distilled water, ammonium nitrate, and explosive composition of ethanol blended hydrogen peroxide. As a result, the blasting cap test method proposed in this study could be helpful in propellant development in terms of quantitatively measuring and comparing the explosive power of propellants. + COLLAPSE
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- Numerical Simulation of Ethylene Fueled Scramjet Combustor with Air Throttling, Part2: Transient Details
- Jeong-Yeol Choi, Jinhyeon Noh, Seung-Min Jeong, Jae-Eun Kim, Vigor Yang
- A high-resolution numerical study is carried out to investigate the transient process of the fuel injection, combustion, and the shock-train formation by …
- A high-resolution numerical study is carried out to investigate the transient process of the fuel injection, combustion, and the shock-train formation by air-throttling in the isolator of an ethylene-fueled direct-connect scramjet combustor. The transient simulation begins with the supersonic air flow development followed by fuel injection. Air-throttling is then applied at the expansion part of the combustor to provide mass addition to block the flow to subsonic speed. The ignition occurs several milliseconds later when the fuel and air are mixed sufficiently. The pressure buildup by the combustion leads to the shock-train formation in the isolator section that advances to the exit of the facility nozzle. Then, the air- throttling is deactivated, the exhaust process begins and the situation before the air-throttling is restored. Present simulation shows the detailed processes in the dual mode scramjet combustor for better understanding of the operation regimes and characteristics. + COLLAPSE
Journal Informaiton
Journal of Propulsion and Energy
Journal of Propulsion and Energy
Journal of Propulsion and Energy
한국추진공학회
Room 502, The Korean Society of Propulsion Engineers, 28, Daehak-ro, Yuseong-gu, Daejeon, Republic of Korea
Tel: 82-42-822-6472 / Fax: 82-42-822-6472 / E-mail: kspe@kspe.org Copyright© Journal of Propulsion and Energy. Powered by APUB
Tel: 82-42-822-6472 / Fax: 82-42-822-6472 / E-mail: kspe@kspe.org Copyright© Journal of Propulsion and Energy. Powered by APUB