Thermodynamic analysis for a chemically recuperated scramjet

Endothermic hydrocarbon fuel is regarded as an optimal fuel for a scramjet with regenerative cooling,which provides extra cooling through endothermic chemical conversion to avoid the severly limited cooling capacity when conventional fuels are adopted for cooling.Although endothermic cooling is proposed from the view point that the heat sink of a conventional fuel is insufficient,the heat-absorbing through endothermic chemical reaction is actually a chemical recuperation process because the wasted heat dissipated from the engine thermal structure is recovered through the endothermic chemical reaction.Therefore,the working process of a scramjet with endothermic hydrocarbon fuel cooling is a chemical recuperative cycle.To analyze the chemical recuperative cycle of a chemically recuperated scramjet engine,we defined physical and chemical recuperation effectivenesses and heating value increment rate,and derived engine performance parameters with chemical recuperation.The heat value benefits from both physical and chemical recuperations,and it increases with the increase in recuperation effectiveness.The scramjet performance parameters also increase with the increase in chemical recuperation effectiveness.The increase in chemical recuperation effectiveness improves both the performances of the fuel cooling system and the combustion system.The results of analysis prove that the existence of a chemical recuperation process greatly improves the performance of the whole scramjet.

Fluid-Dynamics Analysis and Structural Optimization of a 300 kW MicroGas Turbine Recuperator

Computational Fluid Dynamics(CFD)is used here to reduce pressure loss and improve heat exchange efficiency in the recuperator associated with a gas turbine.First,numerical simulations of the high-temperature and lowtemperature channels are performed and,the calculated results are compared with experimental data(to verify the reliability of the numerical method).Second,the flow field structure of the low-temperature side channel is critically analyzed,leading to the conclusion that the flow velocity distribution in the low-temperature side channel is uneven,and its resistance is significantly higher than that in the high-temperature side.Therefore,five alternate structural schemes are proposed for the optimization of the low-temperature side.In particular,to reduce the flow velocity in the upper channel,the rib length of each channel at the inlet of the low-temperature side region is adjusted.The performances of the 5 schemes are compared,leading to the identification of the configuration able to guarantee a uniform flow rate and minimize the pressure drop.Finally,the heat transfer performance of the optimized recuperator structure is evaluated,and it is shown that the effectiveness of the recuperator is increased by 1.5%.

Structural Modulation of Gut Microbiota in Rats with Allergic Bronchial Asthma Treated with Recuperating Lung Decoction

Objective To investigate whether recuperating lung decoction （RLD） can modulate the composition of gut microbiota in rats during asthma treatment. Methods Fifteen Sprague-Dawley rats were divided randomly and equally into control group, model group, dexamethasone （DEX） group, RLD medium-dose group, and RLD high-dose group. The asthma model was established in all groups, except for the control group. The rats in the DEX and RLD groups were treated orally with DEX and RLD, respectively. The rats in the control and model groups were treated orally with 0.9% saline. The intestinal bacterial communities were compared among groups using 16S rRNA gene amplification and 454 pyrosequencing. Results The microbial flora differed between the control and model groups, but the flora in the RLD groups was similar to that in the control group. No significant differences were observed between the RLD high-dose and medium-dose groups. RLD treatment resulted in an increase in the level beneficial bacteria in the gut, such as Loctobocillus and Bifidobocterium spp. Conclusion Oral administration of RLD increased the number of intestinal lactic acid-producing bacteria, such as Loctobocillus and Bifidobecterium, in asthma model rats.

Optimization of Recuperative System in Rotary Furnace for Minimization of Elemental Loss during Melting

Two rotary furnaces of different construction model were used for the research work. One has no recuperating system and the second one has recuperating system. 60 kg of grey cast iron scrap was charged into each of the furnaces at different time, after preheating the furnaces for 40 minutes. 0.5 kg graphite and 0.2 kg ferrosilicon were charged along with the scrap. The theoretical charge calculations have the composition of the melt as 4.0% carbon and 2.0% silicon. Charges in the furnaces were heated to obtain molten metal suitable for casting at 1350&degC. The content of the furnaces was tapped three times after the attainment of 1350&degC with 15 minutes interval between each tapping. Optical light emission spectrometer was used to analyze the resulting composition of the tapped samples. For type A furnace (without recuperation), sample A has its carbon and silicon contents reduced compared to expected value by 25.5% and 10.8%, sample B reduced by 29% and 13.4% and sample C reduced by 32% and 17.0% respectively. In Type B furnace (with recuperation), sample D has its carbon and silicon contents reduced by 12.2% and 7.3%, Sample E reduced by 13.0% and 8.0% and sample F reduced by 13.9% and 8.9% respectively.

Control of the Electric Vehicles Power Chain with Electromagnetic Switches Reducing the Energy Consumption

Among the factors slowing down the production of the electric vehicles in big series, we mention the problem of weak autonomy directly bound to the weak storage capacity of the batteries. In this context, this paper describes a strategy of power chain vector control reducing the consumption and integrating a system of energy recuperation. Besides, this power chain is conceived by an analytic approach optimizing the autonomy and reducing the production cost of electric vehicle. The choice of the static converter to electromagnetic switches is a determining factor for the reliability of the global system and the reduction of the consumption. This choice poses a problem of adaptation of this low-frequency converter type to the global system that will be treated in this paper.

Evaluating the Energy Efficiency Performance of a Micro Combustor with and without Heat Recuperation

Micro-combustion research works are motivated by development of portable, autonomous power generators such as the micro TPV with improvement in energy density over batteries. Heat recuperation is a technique which contributes to better energy efficiency performance by recovering heat from the exhaust gas. In this paper, a numerical simulation is carried out to study the impact of incorporating recuperation on the performance of micro modular combustor system. The simulation results have been validated by experiments;achieving close agreement between simulated and experi-mental data. It was observed that the mean wall temperature, radiation power and emitter efficiency markedly improved with the incorporation of a heat recuperator. In addition, 25.8% enhancement of total radiation power and 30.6% emitter efficiency could be realized when the hydrogen air equivalence ratio was 0.9.

Refrigerator Coupling to a Water-Heater and Heating Floor to Save Energy and to Reduce Carbon Emissions

With an aim of rationing use of energy, energy safety, and to reduce carbon emission, our interest was geared towards the refrigerators and all the refrigerating machines. Indeed the heat yielded by the exchanger condenser can be developed for the water heating, floors heating etc. After an encouraging theoretical study, two prototypes were produced in order to validate the theoretical results. A first refrigerator was coupled with a water-heater and another with a heating floor. The water temperature reached, in one day, is of 60℃;which makes it possible to predict better results with a continuously used refrigerator. In the same way for the heating floor coupled with the second refrigerator, the temperature reached high values because the surface is reduced;however for the heating floors the standard fixes the temperature between 28℃ and 30℃.

Modeling of Sectional and Multi-stage Thermoelectric Modules as Waste Heat Recuperators

The results of computer simulation of segmented and cascaded thermoelectric generator modules are presented. That use of Bi2Te3-based materials as cold sections and PbTe-based materials as hot sections for two-section modules in the temperature range 303-773 K, allows to multiply their efficiency by 1.28 as compared to single-section ones. Cascade structures are characterized by better efficiency and lesser output power compared with the sectional, although construction investigated modules are designed to the equal areas.

Ankan Brand Energy Recuperator

At the 40th Eureka World Invention Fair held in Brussels in 1991, the Ankan recuperator, a health product produced by the Sino-foreign funded Ankan Health Product Corporation, Ltd. in Tianjin, drew large crowd who suffered hypertension headaches, skin diseases and arthritis. One city council member joked, "I’ll try it once at the risk of my life." Surprised, within 30 minutes after being treated by the Ankan energy recuperator, the old man suffering from chronic neuritis raised his right arm. The pain was gone and an ulcer on the arm was basically healed. Many suffering from bronchitis, pulmonary emphasema, arthritis, shoulder pain and paralysis were cured. After inspection by the appraisal commission,

Dual Pressure versus Hybrid Recuperation in an Integrated Solid Oxide Fuel Cell Cycle--Steam Cycle

A SOFC （solid oxide fuel cell） cycle running on natural gas was integrated with a ST （steam turbine） cycle. The fuel is desulfurized and pre-reformed before entering the SOFC. A burner was used to combust the remaining fuel after the SOFC stacks. The off-gases from the burner were used to produce steam in a HRSG （heat recovery steam generator）. The bottoming steam cycle was modeled with two configurations： （1） a simple single pressure level and （2） a dual pressure level with both a reheat and a pre-heater. The SOFC stacks in the present SOFC-ST hybrid cycles were not pressurized. The dual pressure configuration steam cycle combined with SOFC cycle （SOFC-ST） was new and has not been studied previously. In each of the configuration, a hybrid recuperator was used to recovery the remaining energy of the off-gases after the HRSG. Thus, four different plants system setups were compared to each other to reveal the most superior concept with respect to plant efficiency and power. It was found that in order to increase the plant efficiency considerably, it was enough to use a single pressure with a hybrid recuperator instead of a dual pressure Rankine cycle.

Study of Microturbine Models in Islanded and Grid-Connected Mode

Modeling and simulation of two different microturbine （MT） models to analyze load following performance as distributed energy resource （DER） have been presented in this paper. The first model consists of speed governor, acceleration control, and temperature control blocks while the other is GAST model. The system comprises a synchronous generator and a MT coupled to it. Simulations are carried out in islanded and grid-connected mode to observe the system response when supplying variable loads. The load following characteristics is observed and validated for this MT-synchronous generator model in Matlab-Simulink environment. This is applicable with combined heat power （CHP） generators both with general fuel as well as bio-fuels. The use of bio-fuels is very much promising for generating green power preventing green house gas emissions for fighting against global warming.

Numerical Study on Local Flow and Heat Transfer Characteristics of Supercritical CO_(2) in PCHE with Sinusoidal Channels

Local heat transfer and flow characteristics,which is crucial to the overall performance of supercritical CO_(2) recuperators,is rarely examined in details in reported studies.In this paper,the local heat transfer and flow characteristics of supercritical CO_(2) in sinusoidal channel printed circuit heat exchangers are numerically investigated under the working conditions of recuperators.Based on the simplified physical model constituted by10 pitches,the variations of Re,heat flux,Nu,secondary flow and other relevant parameters along the flow direction are analyzed firstly.Comparison is further made between the high and low temperature recuperators(HTR and LTR).It's observed that the local heat transfer and flow characteristics vary greatly from the inlet to the outlet,especially in the LTR.Differences of 127.5% and 61.7% can be observed on the cold side of the LTR for Re and heat transfer coefficient h, respectively.Results indicate that the temperature difference and heat transfer coefficient h should not be regarded as constant and the distribution of h should be carefully considered in the design of the LTR.The complicated interactions among the varying thermophysical properties,buoyancy and the periodically changed centrifugal force are believed to be the key that shapes the flow fields.Furthermore,the changes of the wavy angle θ are found to have greater influence than the changes of mass flow rate in reshaping the flow field when θ>25°.Though gravity direction strongly affects the local heat transfer and flow characteristics,it's also found that the effects on the overall thermal-hydraulic performance are relatively minor.Yet the installation direction that yields a_y=g should better be avoided for the sinusoidal channel printed circuit heat exchanger.

Heat Recuperation for the Self-Condensing CO_(2)Transcritical Power Cycle

The supercritical CO_(2)Brayton cycle has potential to be used in electricity generation occasions with its advantages of high efficiency and compact structure.Focusing on a so-called self-condensing CO_(2)transcritical power cycle,a model was established and four different layouts of heat recuperation process were analyzed,a without-recuperation cycle,a post-recuperation cycle,a pre-recuperation cycle and a re-recuperation cycle.The results showed that the internal normal cycle's share of the whole cycle increases with increasing the cooling pressure and decreasing the final cooled temperature.Heat load in the supercritical heater decreases with increasing the cooling pressure.From perspective of performance,the re-recuperation cycle and the pre-recuperation cycle have similar thermal efficiency which is much higher than other two layouts.Both thermal efficiency and net power output have a maximum value with the cooling pressure,except in the condition with the final cooled temperature of 31℃.Considering both the complexity and the economy,the pre-recuperation cycle is more applicable than the other options.Under 35℃of the final cooled temperature,the thermal efficiency of the pre-recuperation cycle reaches the peak 0.34 with the cooling pressure of 8.4 MPa and the maximum net power output is 2355.24 kW at 8.2 MPa of the cooling pressure.

Performance assessment of simple and modified cycle turboshaft gas turbines

This paper focuses on investigations encompassing comparative assessment of gasturbine cycle options.More specifically,investigation was caried out of technical performanceof turboshaft engine cycles based on existing simple cycle(SC)and its projected modifiedcycles for civil helicopter application.Technically,thermal efficiency,specific fuel consump-tion,and power output are of paramount importance to the overall performance of gas urbineengines.In course of carrying out this research,turbomatch software established at CranfieldUniversity based on gas turbine theory was applied to conduct simulation of a simple cycle(baseline)two-spool helicopter turboshaft engine model with free power turbine.Similarly,some modified gas urbine cycle configurations incoporating unconventional components,such as engine cycle with low pressure compressor(LPC)zero-staged,recuperated enginecycle,and intercooled/recuperated(ICR)engine cycle,were also simulated.In doing so,designpoint(DP)and off-design point(OD)performances of the engine models were established.Thepercentage changes in performance parameters of the modified cycle engines over the simplecycle were evaluated and it was found that to a large extent,the modified engine cycles withunconventional components exhibit better performances in terms of thermal efficiency andspecific fuel consumption than the traditional simple cycle engine.This research made use ofpublic domain open source references.

Performance of small-scale aero-derivative industrial gas turbines derived from helicopter engines

This paper considers comparative assessment of simple and advanced cycle small-scale aero-derivative industrial gas turbines derived from helicopter engines.More particularly,investigation was made of technical performance of the small-scale aero-derivative engine cycles based on existing and projected cycles for applications in industrial power generation,combined heat and power concept,rotating equipment driving,and/or allied processes.The investigation was done by carrying out preliminary design and performance simulation of a simple cycle(baseline)two-spool small-scale aero-derivative turboshaft engine model,and some advanced counterpart aero-derivative configurations.The advanced configurations consist of recuperated and intercooled/recuperated engine cycles of same nominal power rating of 1.567 MW.The baseline model was derived from the conversion of an existing helicopter engine model.In doing so,design point and off-design point performances of the engine models were established.In comparing their performances,it was observed that to a large extent,the advanced engine cycles showed superior performance in terms of thermal efficiency,and specific fuel consumption.In numerical terms,thermal efficiencies of recuperated engine cycle,and intercooled/recuperated engine cycles,over the simple cycle at DP increased by 13.5%,and 14.5%respectively,whereas specific fuel consumption of these cycles over simple cycle at DP decreased by 12.5%,and 13%respectively.This research relied on open access public literature for data.

Slope Processes, Mass Movement and Soil Erosion： A Review

Soil erosion and land degradation are global problems and pose major issues in many countries. Both soil erosion and mass movement are two forms of land degradation and humans play important roles in these geomorphological processes. This paper reviews slope processes associated with mass movement and soil erosion and contributory factors, including physical and human agents. Acting together, these cause diverse geomorphological features. Slope processes are illustrated by reference to case studies from Brazil and UK. The causes and impacts of erosion are discussed, along with appropriate remedial bioengineering methods and the potential of the measures to prevent these types of environmental degradation. Although there are several agents of erosion, water is the most important one. Cultivation can promote soil erosion, due to ploughing and harvesting, which moves soil down slopes. Soil erosion and mass movement data would inform the viability of soil conservation practices. Integrated management of drainage basins offers a Dromising way forward for effective soil conservation and soil remedial bioengineering in Brazil and UK.

High-density circulating fluidized bed gasifier for advanced IGCC/IGFC-Advantages and challenges

Coal-fired Integrated Gasification Combined Cycle （IGCC） and Integrated coal Gasification Fuel-cell Com- bined cycle （IGFC） are being developed as high-efficiency electric power generation technology. However, the highest theoretical gross thermal efficiency of the conventional IGCC]IGFC is still below 52~. In order to obtain higher power generation efficiency, an advanced IGCC （A-IGCC） or advanced IGFC （A-IGFC） sys- tem making use of the exergy recuperation concept by recycling waste heat from gas turbine or fuel cells for steam gasification of coal and biomass was proposed in our laboratory, Corresponding to this system, a novel high-density triple-bed combined circulating fluidized bed （TBCFB） gasifier, composed of a downer pyrolyzer, a bubbling fluidized bed char gasifier, and a riser combustor, was proposed to replace traditional gasifiers such as the entrained flow bed gasifier. The new system is expected to more effectively utilize the waste heat from gas turbines or fuel cells and the heat produced by the combustion of the unreacted char in the riser combustor for pyrolysis and gasification of coal and biomass. In this short review, the advantages and future challenges in the development of high-density TBCFB gasifier are presented and discussed.

Thermochemical Recuperation for Stirling Engines by Diesel Steam Reforming: Thermodynamic Analysis

Thermochemical exhaust heat recovery is a prospective way to improve the thermal performance of Stirling engines. Based on Aspen HYSYS software, the simulation model of a Stirling engine combustor with a thermochemical recuperation(TCR) reformer was established to calculate the performance of the TCR system. The reforming temperature, fuel distribution ratio, steam-to-carbon ratio(S/C), and reforming pressure were changed to evaluate their effects on the reforming process and system efficiency. With increased reforming temperature, the equilibrium fuel conversion rate and heat recovery amount in the reformer gradually increase. The maximum combustor efficiency is achieved at the temperature of 600℃ and the fuel distribution ratio of 40%. With the S/C ratio increased from 1 to 2.5, the heat recovery rate and combustor efficiency increase significantly. The results show that the increase of fuel distribution ratio and S/C ratio leads to decreased reforming temperature, and external heat is needed to meet the heat balance for steam reforming. At a given reforming temperature and S/C ratio, increased reforming pressure results in decreased equilibrium fuel conversion rate and reforming reaction heat. At 5 MPa reforming pressure and 550℃ reforming temperature, the efficiency of the Stirling engine combustor is 92.7%, proving that the thermochemical recovery system can be applied to the Stirling engine under high pressure conditions.

Creep life assessment of aero-engine recuperator based on continuum damage mechanics approach

The creep life of an aeroengine recuperator is investigated in terms of continuum damage mechanics by using finite element simulations.The effects of the manifold wall thickness and creep properties of brazing filler metal on the operating life of the recuperator are analyzed.Results show that the crack initiates from the brazing filler metal located on the outer surface of the manifold with the wall thickness of 2 mm and propagates throughout the whole region of the brazing filler metal when the creep time reaches 34900 h.The creep life of the recuperator meets the requirement of 40000 h continuous operation when the wall thickness increases to 3.5 mm,but its total weight increases by 15%.Decreasing the minimum creep strain rate with the enhancement of the creep strength of the brazing filler metal presents an obvious effect on the creep life of the recuperator.At the same stress level,the creep rupture time of the recuperator is enhanced by 13 times if the mismatch between the minimum creep rate of the filler and base metal is reduced by 20%.

A separate-type autothermal CH_(4) dry reforming system with exergy recuperation

Currently,CO_(2) conversion and utilization have become a key to mitigate the global warming.In this study,a novel separate-type autothermal dry reforming of methane(S-ATDRM)system is proposed and simulated,in which the methane dry reforming combined with methane partial oxidation is performed in a circulating fluidized bed with exergy recuperation to eliminate the negative effect of the products of CH_(4) partial oxidation on the DRM reaction and further improve the CO_(2) conversion efficiency.The results demonstrate that this S-ATDRM system can achieve an exergy efficiency of 84.7%,and about 1055.7 kW of exergy can be recuperated from the process for crude syngas cooling and reapplied for pre-heating of feedstocks of CO_(2),O2 and CH_(4).It is found that the largest exergy destruction in this system occurs in the partial oxidation reactor,which occupies ca.45.6%of the whole exergy loss.Comparing with the conventional ATDRM system,although the exergy of S-ATDRM system is decreased by approximately 0.3%,the CO_(2) conversion is substantially increased by about 11.3%.