Investigation and Improvement of Thermal Efficiency of Hypersonic Scramjet

2014 ◽  
Author(s):  
Mohammad A. Hossain ◽  
Md. Taibur Rahman ◽  
Mohammad Ikthair Hossain Soiket ◽  
Sarzina Hossain
Keyword(s):  
Thermal Efficiency ◽  
Fluid Velocity ◽  
Specific Impulse ◽  
Flow Analysis ◽  
Inlet Temperature ◽  
Extensive Literature ◽  
Temperature Ratio ◽  
Main Research ◽  
Overall Efficiency ◽  
Inlet Conditions

This work is focused on investigation of thermal efficiency of a Hypersonic scramjet engine and propose some improvement of thermal efficiency based on thermodynamic and fluid flow analysis. Thermal management system is one of the main research fields in scramjet design. As it has no moving parts, the total thermal efficiency depends on inlet conditions, conditions of combustor exit and conditions of the engine exit. A combustor exit condition dictates the velocity and temperature after combustion. we concentrate our focus on this section. The first part of the paper, we tried to describe the fundamental exergy relationship for scramjet and we developed the relation of exergy distribution and exergy delivery rate. From an extensive literature review, we have found the relations between fluid velocity, pressure and temperature, which is described in the later part of the paper. Our main focus is to develop a combined relation of thermal efficiency in terms of engine exit velocity, temperature and air-fuel ratio. Different characteristic parameters such as overall efficiency, thermal efficiency, specific impulse have been determined at different inlet temperature ratio or the cycle static temperature ratio (T3/T0) and an optimum inlet temperature ratio is proposed for maximum overall efficiency.

IMPORTANCE OF 3D VEHICLE HEAT EXCHANGER MODELING

2021 ◽  
pp. 1-10
Author(s):  
Michal Schmid ◽  
Fatih Bozkurt ◽  
Petr Pašcenko ◽  
Pavel Petržela
Keyword(s):  
Fluid Flow ◽  
Heat Exchanger ◽  
Fluid Velocity ◽  
Coolant Temperature ◽  
Inlet Temperature ◽  
Vehicle Simulation ◽  
Velocity Magnitude ◽  
Primary Fluid ◽  
The Difference ◽  
Inlet Conditions

Abstract The work demonstrates, via a comprehensive study, the necessity of using a 3D CFD approach for heat exchanger (HTX) modelling within underhood vehicle simulation. The results are presented as the difference between 1D and 3D CFD approaches with a focus on auxiliary fluid (e.g. coolant) temperature prediction as a function of primary fluid (e.g. air) inlet conditions. It has been shown that the 1D approach could significantly underpredict auxiliary fluid inlet temperature due to neglecting the spatial distribution of primary fluid velocity magnitude. The resultant difference in the auxiliary fluid flow HTX inlet temperature is presented and discussed as a function of the Uniformity Index (UI) of the primary fluid flow velocity magnitude. Additionally, the 3D HTX model's importance is demonstrated in an industrial example of full 3D underhood simulation.

scholarly journals Numerical Modelling of a Concentrating Photovoltaic Thermal Collector

2019 ◽  
Vol 16 (2) ◽  
pp. 6482-6501
Author(s):  
M. Valizadeh ◽  
F. Sarhaddi ◽  
F. Sobhnamayan
Keyword(s):  
Ambient Temperature ◽  
Thermal Efficiency ◽  
Fluid Velocity ◽  
Incident Beam ◽  
Inlet Temperature ◽  
Beam Radiation ◽  
Electrical Efficiency ◽  
Current Voltage ◽  
Diameter Pipe ◽  
Efficiency Increase

In this paper, the performance evaluation of a concentrating photovoltaic thermal (CPVT) collector is carried out. By writing energy, balance for the various components of CPVT collector, a set of nonlinear equations is obtained to calculate the temperature of different parts of the system. The electrical parameters of the CPVT collector are calculated by the four-parameter model of current-voltage. The simulation results of the present study are in good accordance with the previous studies data. The results show that with the fluid velocity increase from 0.08 to 0.43 m/s, the electrical efficiency and thermal efficiency increase by 1.05% and 2.2%, respectively. The thermal efficiency is enhanced by 9.4% as the receiver width is increased from 0.06 to 0.2 m. With the increase of diameter pipe from 0.017 to 0.06 m an increase of 2.75% and 3.9% is observed in the thermal and electrical efficiencies, respectively. The thermal efficiency has an ascending/descending trend with the increase of collector length. The increase of fluid inlet temperature from 273.15 to 363.15 K reduces the thermal and electrical efficiencies by 7.3% and 4.05%, respectively. The increase of the incident beam radiation from 300 to 1000 W/m2 enhances the electrical efficiency by 4%, while the thermal efficiency has an ascending/descending trend. The ambient temperature increase causes an increase of 5.1% in thermal efficiency. The effect of receiver width and ambient temperature on electrical efficiency is negligible.

Simulation of HCCI Combustion Characteristics for Low RON Gasoline Surrogate Fuels

2014 ◽  
Vol 694 ◽  
pp. 54-58
Author(s):  
Ling Zhe Zhang ◽  
Ya Kun Sun ◽  
Su Li ◽  
Qing Ping Zheng
Keyword(s):  
Equivalence Ratio ◽  
Chemical Kinetic ◽  
Combustion Characteristics ◽  
Material Strength ◽  
Inlet Temperature ◽  
Compression Ignition Engine ◽  
Chemical Kinetic Model ◽  
Hcci Engine ◽  
Surrogate Fuels ◽  
Inlet Conditions

A reduced chemical kinetic model (103species and 468 reactions) for new low-RON(research octane number) gasoline surrogate fuels has been proposed. Simulations explored for ignition delay time have been compared with experimental data in shock tubes at pressure of 10atm-55 atm and temperatue of 600-1400 K (fuel/air equivalence ratio=0.5,1.0,2.0 and EGR rate=0, 20%). The simulation data presented 15% enlargement compared with experiments showed applicability of the new kinetic mode in this work. A combustion simulation model has been build for HCCI(homogeneous charge compression ignition) engine with Chemkin-pro. The effects of different air inlet temperature, inlet pressure, engine speed and the fuel air equivalence ratio on the combustion characteristics of the fuel were researched. The results indicated the combustion in an HCCI engine worked sufficiently with lean mixtures and low speed. Meanwhile the material strength could be influenced when the inlet conditions changed. This helps to promote the low-RON gasoline surrogate fuel application in the HCCI engine.

Experimental Study to Characterize the Performance of Combined Photovoltaic/Thermal Air Collectors

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Véronique Delisle ◽  
Michaël Kummert
Keyword(s):  
Thermal Efficiency ◽  
Closed Loop ◽  
Multiple Linear Regression Model ◽  
Open Loop ◽  
Electrical Performance ◽  
Back Surface ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Cell Temperature ◽  
Average Temperature

Combined photovoltaic/thermal (PV/T) collectors show great potential for reaching the objective of net-zero energy consumption in buildings, but the number of products on the market is still very limited. One of the reasons for the slow market uptake of PV/T collectors is the absence of standardized methods to characterize their performance. Performance characterization is a challenge for PV/T collectors because of the interaction between the thermal and electrical yield. This study addresses this particular issue for PV/T air collectors used in either closed-loop or open-loop configurations. In particular, it presents the potential of the equivalent cell temperature method to determine the temperature of the PV cells in a PV/T air collector and validates models to predict the thermal performance and cell temperature for this particular type of solar collector. Indoor and outdoor experimental tests were performed on two c-Si unglazed PV/T modules. The indoor part of this procedure provided the thermal diode voltage factor and the open-circuit voltage temperature coefficient, two parameters that are essential in the calculation of the equivalent cell temperature. The outdoor procedure consisted of acquiring simultaneous electrical and thermal measurements at various inlet temperatures and flowrates. For the collector used in a closed-loop configuration, thermal efficiency models using the fluid inlet, outlet, or average temperature in the calculation of the reduced temperature provided similar results. For an open-loop configuration, a thermal efficiency model as a function of the fluid outlet flowrate was found to be more appropriate. Using selection of variable methods, it was found that a multiple linear regression model using the fluid inlet temperature, the irradiance, and the fluid outlet temperature as predictive variables could be used to estimate both the PV module back surface average temperature and the equivalent cell temperature. When using the PV temperature predicted by these models in the electrical efficiency model, both PV temperatures showed similar performance. In collectors where the PV back surface temperature is not accessible for temperature sensors mounting, the equivalent cell temperature provides a valuable alternative to be used as the PV temperature. The PV/T collector thermal and electrical performance in either closed-loop or open-loop configurations was found to be encapsulated with a series of five-plots.

scholarly journals Current Status of Ceramic Gas Turbine (CGT302)

1998 ◽  
Author(s):  
Hirotake Kobayashi ◽  
Tetsuo Tatsumi ◽  
Takashi Nakashima ◽  
Isashi Takehara ◽  
Yoshihiro Ichikawa
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Technology Development ◽  
Development Program ◽  
Point Of View ◽  
Current Status ◽  
Fiscal Year ◽  
Inlet Temperature ◽  
Development Organization ◽  
New Energy

In Japan, from the point of view of energy saving and environmental protection, a 300kW Ceramic Gas Turbine (CGT) Research and Development program started in 1988 and is still continuing as a part of “the New Sunshine Project” promoted by the Ministry of International Trade and Industry (MITT). The final target of the program is to achieve 42% thermal efficiency at 1350°C of turbine inlet temperature (TIT) and to keep NOx emissions below present national regulations. Under contract to the New Energy and Industrial Technology Development Organization (NEDO), Kawasaki Heavy Industries, Ltd. (KHI) has been developing the CGT302 with Kyocera Corporation and Sumitomo Precision Products Co., Ltd. By the end of the fiscal year 1996, the CGT302 achieved 37.0% thermal efficiency at 1280°C of TIT. In 1997, TIT reached 1350°C and a durability operation for 20 hours at 1350°C was conducted successfully. Also fairly low NOx was proved at 1300°C of TIT. In January 1998, the CGT302 has achieved 37.4% thermal efficiency at 1250°C TIT. In this paper, we will describe our approaches to the target performance of the CGT302 and current status.

Thermal Aspects of Using Uranium Mononitride Fuel in a SuperCritical Water-Cooled Reactor at Maximum Heat Flux Conditions

2010 ◽  
Author(s):  
Ashley Milner ◽  
Caleb Pascoe ◽  
Hemal Patel ◽  
Wargha Peiman ◽  
Graham Richards ◽  
...  
Keyword(s):  
Heat Flux ◽  
Supercritical Water ◽  
Thermal Efficiency ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Maximum Heat ◽  
Light Water ◽  
Maximum Heat Flux ◽  
Centerline Temperature ◽  
Uranium Mononitride

Generation IV nuclear reactor technology is increasing in popularity worldwide. One of the six Generation-IV-reactor types are SuperCritical Water-cooled Reactors (SCWRs). The main objective of SCWRs is to increase substantially thermal efficiency of Nuclear Power Plants (NPPs) and thus, to reduce electricity costs. This reactor type is developed from concepts of both Light Water Reactors (LWRs) and supercritical fossil-fired steam generators. The SCWR is similar to a LWR, but operates at a higher pressure and temperature. The coolant used in a SCWR is light water, which has supercritical pressures and temperatures during operation. Typical light water operating parameters for SCWRs are a pressure of 25 MPa, an inlet temperature of 280–350°C, and an outlet temperature up to 625°C. Currently, NPPs have thermal efficiency about of 30–35%, whereas SCW NPPs will operate with thermal efficiencies of 45–50%. Furthermore, since SCWRs have significantly higher water parameters than current water-cooled reactors, they are able to support co-generation of hydrogen. Studies conducted on fuel-channel options for SCWRs have shown that using uranium dioxide (UO2) as a fuel at supercritical-water conditions might be questionable. The industry accepted limit for the fuel centerline temperature is 1850°C and using UO2 would exceed this limit at certain conditions. Because of this problem, there have been other fuel options considered with a higher thermal conductivity. A generic 43-element bundle for an SCWR, using uranium mononitride (UN) as the fuel, is discussed in this paper. The material for the sheath is Inconel-600, because it has a high resistance to corrosion and can adhere to the maximum sheath-temperature design limit of 850°C. For the purpose of this paper, the bundle will be analyzed at its maximum heat flux. This will verify if the fuel centerline temperature does not exceed 1850°C and that the sheath temperature remains below the limit of 850°C.

Space–Time Gradient Method for Unsteady Bladerow Interaction—Part II: Further Validation, Clocking, and Multidisturbance Effect

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
L. He ◽  
J. Yi ◽  
P. Adami ◽  
L. Capone
Keyword(s):  
Case Studies ◽  
Flow Analysis ◽  
Space Time ◽  
Inlet Temperature ◽  
Turbine Stage ◽  
Two Stage ◽  
Transonic Compressor ◽  
Surface Time ◽  
Blade Row ◽  
Speed Up

For efficient and accurate unsteady flow analysis of blade row interactions, a space–time gradient (STG) method has been proposed. The development is aimed at maintaining as many modeling fidelities (the interface treatment in particular) of a direct unsteady time-domain method as possible while still having a significant speed-up. The basic modeling considerations, main method ingredients and some preliminary verification have been presented in Part I of the paper. Here in Part II, further case studies are presented to examine the capability and applicability of the method. Having tested a turbine stage in Part I, here we first consider the applicability and robustness of the method for a three-dimensional (3D) transonic compressor stage under a highly loaded condition with separating boundary layers. The results of the STG solution compare well with the direct unsteady solution while showing a speed up of 25 times. The method is also used to analyze rotor–rotor/stator–stator interferences in a two-stage turbine configuration. Remarkably, for stator–stator and rotor–rotor clocking analyses, the STG method demonstrates a significant further speed-up. Also interestingly, the two-stage case studies suggest clearly measurable clocking dependence of blade surface time-mean temperatures for both stator–stator clocking and rotor–rotor clocking, though only small efficiency variations are shown. Also validated and illustrated is the capacity of the STG method to efficiently evaluate unsteady blade forcing due to the rotor–rotor clocking. Considerable efforts are directed to extending the method to more complex situations with multiple disturbances. Several techniques are adopted to decouple the disturbances in the temporal terms. The developed capabilities have been examined for turbine stage configurations with inlet temperature distortions (hot streaks), and for three blade-row turbine configurations with nonequal blade counts. The results compare well with the corresponding direct unsteady solutions.

scholarly journals Numerical Investigation on the Influence of Hot Streak Temperature Ratio in a High-Pressure Stage of Vaneless Counter-Rotating Turbine

2007 ◽  
Vol 2007 ◽  
pp. 1-14 ◽  
Author(s):  
Zhao Qingjun ◽  
Wang Huishe ◽  
Zhao Xiaolu ◽  
Xu Jianzhong
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Heat Load ◽  
Rotor Blades ◽  
Inlet Temperature ◽  
Combined Effects ◽  
Temperature Ratio ◽  
Flow Angle ◽  
Hot Streak ◽  
Relative Flow

The results of recent studies have shown that combustor exit temperature distortion can cause excessive heat load of high-pressure turbine (HPT) rotor blades. The heating of HPT rotor blades can lead to thermal fatigue and degrade turbine performance. In order to explore the influence of hot streak temperature ratio on the temperature distributions of HPT airfoil surface, three-dimensional multiblade row unsteady Navier-Stokes simulations have been performed in a vaneless counter-rotating turbine (VCRT). The hot streak temperature ratios from 1.0 (without hot streak) to 2.4 were used in these numerical simulations, including 1.0, 1.2, 1.6, 2.0, and 2.4 temperature ratios. The hot streak is circular in shape with a diameter equal to 25%of the span. The center of the hot streak is located at 50%of span and 0%of pitch (the leading edge of the HPT stator vane). The predicted results show that the hot streak is relatively unaffected as it migrates through the HPT stator. The hot streak mixes with the vane wake and convects towards the pressure surface (PS) of the HPT rotor when it moves over the vane surface of the HPT stator. The heat load of the HPT rotor increases with the increase of the hot streak temperature ratio. The existence of the inlet temperature distortion induces a thin layer of cooler air in the HPT rotor, which separates the PS of the HPT rotor from the hotter fluid. The numerical results also indicating the migration characteristics of the hot streak in the HPT rotor are predominated by the combined effects of secondary flow and buoyancy. The combined effects that induce the high-temperature fluid migrate towards the hub on the HPT rotor. The effect of the secondary flow on the hotter fluid increases as the hot streak temperature ratio is increased. The influence of buoyancy is directly proportional to the hot streak temperature ratio. The predicted results show that the increase of the hot streak temperature ratio trends to increase the relative Mach number at the HPT rotor outlet, and decrease the relative flow angle from 25%to 75%span at the HPT rotor outlet. In the other region of the HPT outlet, the relative flow angle increases when the hot streak temperature ratio is increased. The predicted results also indicate that the isentropic efficiency of the VCRT decreases with the increase of the hot streak temperature ratio.

scholarly journals Comparison of Various Fluidized Bed Combustor-Gas Turbine Systems

1985 ◽  
Author(s):  
Arthur P. Fraas
Keyword(s):  
Gas Turbine ◽  
Fluidized Bed ◽  
Thermal Efficiency ◽  
Combustion Efficiency ◽  
Capital Cost ◽  
Inlet Temperature ◽  
Extensive Experience ◽  
Helium Gas ◽  
Steam Plant ◽  
Fluidized Bed Combustor

Pressurizing a fluidized bed combustor with a gas turbine greatly improves both sulfur retention and combustion efficiency. Operating the gas turbine with a high inlet temperature (e.g. 900°C) would yield a thermal efficiency about four points higher than for an atmospheric furnace, but 40 y of experience have failed to solve problems with flyash erosion and deposits. Extensive experience such as that with fluidized bed catalytic cracking units indicates that the gas turbine blade erosion and deposit problems can be handled by dropping the turbine inlet temperature below 400°C where the turbine delivers just enough power to drive the compressor. The resulting thermal efficiency is about half a point higher than for an atmospheric bed, and the capital cost of the FBC-related components is about 40% lower. While a closed-cycle helium gas turbine might be used rather than a steam cycle, the thermal efficiency would be about four points lower and the capital cost of the FBC-related components would be roughly twice that for the corresponding steam plant.

Improvements to an Air Bypass System on a Kawasaki M1A-13X Engine

2004 ◽  
Author(s):  
Suresh R. Vilayanur ◽  
John Battaglioli
Keyword(s):  
Flow Analysis ◽  
Effective Area ◽  
Inlet Temperature ◽  
Flow Area ◽  
Detailed Measurement ◽  
Pressure Drops ◽  
Operating Range ◽  
Flow Losses ◽  
Catalytic Combustor ◽  
Improved Design

A new bypass system using an improved design has been fabricated and tested on a Kawasaki M1A-13X gas turbine engine. The engine and catalytic combustor are currently installed at the City of Santa Clara’s Silicon Valley Power municipal electrical generating stations and connected to the utility grid. The use of a bypass system with a catalytic combustor, incorporating the Xonon Cool Combustion™ technology, on an M1A-13X system increases the low emissions load turndown and ambient operating range without impacting engine efficiency. The increased operating range is achieved because the bypass system provides the required adiabatic combustion temperature (Tad) in the combustor’s post-catalyst burn out zone without changing the turbine inlet temperature. A detailed measurement of the pressure drops, in the old bypass system, revealed that there were large flow losses present, particularly in the re-injection spool piece and the extraction plenum. Since it was determined that the spool had the highest pressure loss, this was the component targeted for improvement. The analysis coupled with detailed measurements on the reinjection piece revealed that the effective area actually varied with flow As the flow changed, so did the flow mechanics inside and exiting the spool piece. Therefore, in order to achieve the design target, the flow area of the spool piece had to be optimized at the predicted capacity flow rate. CFD analysis of the spool piece revealed the regions of losses in the re-injection piece. This analysis along with a one-dimensional flow analysis of the entire system enabled the design of new spool re-injection piece. Once the design was completed, the new bypass system was fabricated and tested. Bypass flow capacity was increased by about 22%. This was achieved by alleviating regions of flow losses and also by using a new “scoop” design for the bypass reinjection tubes. As expected, engine turndown capacity and ambient operating range were improved with the new design.

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