Chemically Recuperated Gas Turbine Research Articles

Multi-objective optimization of steam methane reformer in micro chemically recuperated gas turbine

A kinetic theory, known as the Langmuir–Hinshelwood–Hougen–Watson adsorption model, is applied to describe the steam methane reforming (SMR) in a 500 kW scale micro chemically recuperated gas turbine (CRGT) cycle. The response surface models of important performance parameters, including the methane conversion, carbon monoxide selectivity, and chemically recuperated heat as a function of the temperature, pressure, steam-to-carbon ratio, and contact time are numerically obtained based on the cases selected by the central composite design. The factors affecting the SMR performance are analyzed, and the reformer performance is optimized using both the desirability function combined with the response surface methodology and the second generation non-dominated sorting genetic algorithm. Finally, performance of the optimized reformer and electrical efficiency of the micro CRGT cycle with the reformer are evaluated. Results reveal that the efficiency of the micro CRGT is 40.70%, which is much higher than the typical high-efficiency micro gas trubine without reformer.

Performance evaluation of a combined power generation system integrated with thermochemical exhaust heat recuperation based on steam methane reforming

The present paper applies the thermodynamic analysis with the determining the efficiency of a combined cycle power plant with a chemically recuperated gas turbine. Thermochemical recuperation of exhaust heat after a gas turbine is realized via the steam methane reforming process. The main concept of combined cycle power plant (CCPP) with chemically recuperated gas turbine (CRGT) is based on the use of exhaust heat for endothermic reforming of the original hydrocarbon fuel in a reformer and for steam generation for a steam cycle. To understand the effect of operating variables such as temperature, pressure, and steam-to-methane ratio on the overall efficiency, the energy and mass balances were compiled. The energy flows were represented by a Sankey diagram. The results of the thermodynamic analysis show that efficiency of CCPP with CRGT is significantly higher (4–7%) than efficiency of CCPP with a conventional gas turbine without TCR. Maximum efficiency of CCPP with CRGT of 0.6412 is observed at inlet temperature of working gas of 1600 °C, pressure of 23 bar for a steam-to-methane ratio of 3.0. In the temperature of inlet working gas below 1200 °C the increase in the efficiency of CCPP with TCR is less than 2%.

Ammonia-fired chemically recuperated gas turbine: Thermodynamic analysis of cycle and recuperation system

Ammonia is one of the prospective alternatives to hydrocarbon fuels. Currently, there are projects for developing of ammonia fired gas turbines up to 40 MW. The addition of thermochemical exhaust gas heat recuperation systems to ammonia-fired gas turbines could be a promising way to increase their efficiency. In this paper, the concept of an ammonia-fired chemically recuperated gas turbine (CRGT) is thermodynamically analyzed. Gas turbine with thermochemical recuperation by ammonia decomposition is analyzed via Aspen HYSYS for a wide range of operating parameters: turbine inlet temperature of 700–1300 °C, the pressure of 6–21 bar. The thermochemical exhaust heat recuperation system is recovering the exhaust heat in a reformer (for the endothermic reaction of ammonia decomposition), a heater (to preheat ammonia to the temperature of the decomposition reaction), and a regasifier (for regasification of liquid ammonia). The thermochemical exhaust heat recuperation system makes it possible to recover up to 43% of exhaust heat. The maximum efficiency of CRGT is observed at 9 bar for Tin = 700 °C; 12 bar at Tin = 800 °C; 15 bar at Tin = 900 °C; 18 bar at Tin = 1000 °C. In the temperature range above Tin > 1000 °C, when the pressure rises above 15 bar, the efficiency does not increase significantly.

Efficiency of chemically recuperated gas turbine fired with methane: Effect of operating parameters

Previously, a set of optimistic studies have been published to show the efficiency of chemically recuperated gas turbines (CRGT) based on steam methane reforming. The thermodynamic efficiency of such turbines is depending not only on temperature and pressure in a cycle but also on temperature, pressure and steam-to-methane ratio in a recuperation system. In this paper, the effect of operational parameters (temperature, pressure, steam-to-methane ratio) on the efficiency of CRGT was determined. Exhaust heat recuperation in CRGT is taking place due to methane reforming, steam-methane mixture heating, and steam generation. A thermodynamic enthalpy of steam methane reforming process was determined via Gibbs free energy minimization method. The thermodynamic analysis of CRGT was performed in Aspen HYSYS. The efficiency of CRGT was determined for a wide range of operational parameters (gas turbine inlet temperature of 800–1500 °C, pressure of 5–25 bar, steam-to-methane ratio of 1...3). Based on the analysis it was confirmed that the efficiency of CRGT and thermochemical exhaust heat recuperation system is increasing with an increase in temperature. An increase in temperature and steam-to-methane ratio leads to an increase in a share of recuperated heat in a reformer. The heat recuperation rate is up to 0.63 for a high-temperature gas turbine and a steam-to-methane ratio of 3. The efficiency of CRGT is up to 49% for gas turbines with inlet gas temperature of 1500 °C which is an available level in modern gas turbines from Mitsubishi, Siemens, Alstom, etc.

Low CO2 emissions chemically recuperated gas turbines fed by renewable methanol

Steam reforming of the fuel in chemically recuperated gas turbine (CRGT) plants allows performing a heat recovery of the gas turbine exhausts, boosting the plant performance. Power-to-liquids technologies are a very interesting solution for storing the excess of renewable electricity into liquid fuels. Among the renewable fuels, methanol is well-known as a hydrogen carrier and an energy feedstock. Indeed, methanol can be stored, transported, and used in an easier way than hydrogen.In this paper a CRGT fed by renewable methanol produced in power-to-liquids plant through the CO2 hydrogenation process was studied. The hydrogen needed to synthesize methanol is produced in an alkaline electrolyser, while the CO2 is captured from the CRGT exhausts. The opportunity of introducing an organic Rankine cycle (ORC) to enhance the energy production was also investigated. Dedicated simulation models of the single sections and of the overall system were developed through the commercial software Aspen Plus.The overall system was sized to generate about 350 kg/h of methanol, resulting in a power production in the order of 600–750 kW. The study demonstrated that the integrated system based on a CRGT plant fed by renewable methanol can effectively store RES surplus and produce electricity with very low CO2 emissions. The overall system shows a power-to-power efficiency of about 0.23 that can be slightly increased with the introduction of an ORC system to better exploit the heat released by the CRGT.

Syngas production with thermo-chemically recuperated gas expansion systems: An exergy analysis and energy integration study

In spite of the large degree of energy integration in the modern syngas production units, the highly endothermic reactions of steam methane reforming and the combined steam and power generation still require a huge amount of energy that is typically supplied by an expensive natural gas-fired furnace at very high temperatures. Since normally only half of the energy supplied by the furnace is used to carry out the reforming reactions, the remaining heat recovery must be performed in a separate convection train (HRCT). Additionally, the high temperature effluent of the secondary reformer is generally cooled down by producing low temperature steam, increasing the process irreversibility and the losses associated to the excessive amount of condensate. Thus, in this paper, the advantages of introducing a chemically recuperated gas turbine (CRGT) concept to simultaneously carry out the endothermic chemical reactions and recover the exergy available from the autothermal reformer effluent are discussed. In this way, higher temperatures and higher conversions can be attained with lower driving forces. The power required by the air compression as well as other ancillary systems (e.g. air separation unit, carbon capture system, boiler feedwater pumps and recompressor) can also be supplied, while the exergy of the exhaust gases from the turbine is used more efficiently than in typical steam generation systems. Thus, more compact and integrated syngas production plants can be envisaged. Moreover, by introducing more advanced cogeneration features such as air enrichment, process gas reheating and incremental levels of pressures in the reaction-driven components, energy savings together with drastically reduced atmospheric CO2 emissions and irreversibility can be achieved in the frontend syngas production section. As a result, the average specific exergy destruction and exergy fuel consumption of the proposed CRGT-based configurations are, respectively, 12.0% and 2.7% lower, whereas the specific atmospheric CO2 emissions are cut down up to 25%, when compared to the conventional syngas production process.

Transient performances of the gas turbine recuperating waste heat through hydrogen rich fuels

Operational rules and control strategies of the chemically recuperated gas turbine (CRGT) in the marine propulsion are investigated in this paper. The Minimization of Gibbs free energy method is used to calculate the diesel-steam reforming reaction which products synthetic hydrogen rich fuels, and a universal model of the chemical regenerator which is easily applied to different application environments is created. The hydrogen production and hydrogen molar fraction are investigated to verify that the CRGT improve the combustion performances under low working conditions. Off-design calculations are performed to derive proper operational rules, and transient calculations are performed to investigate the best control strategies for the systems. The modelling approach of the chemical regenerator can be generally used in the chemically recuperated gas turbine. The elaborate operational rules can greatly improve the thermal efficiencies under every working condition. The system using synchronous control strategies have better regulation speed and operation stability than that using asynchronous control strategies.

Experimental Research on Low-Temperature Methane Steam Reforming Technology in a Chemically Recuperated Gas Turbine

Under the operating parameters of a chemically recuperated gas turbine (CRGT), the low-temperature methane steam reforming test bench is designed and built; systematic experimental studies about fuel steam reforming are conducted. Four different reforming forms are employed, including catalyst-only reforming, plasma-only reforming, piecewise synergistic reforming, and parallel synergistic reforming. A better reforming form for CRGT was determined by analyzing the effect of methane space velocity, steam-to-carbon ratio of fuel reforming (S/C), wall temperature, and plasma input power. All of the above factors had an effect on the reforming performance, but a direct and significant effect separately on effective carbon recovery rate, total enthalpy increasing rate, methane conversion, and fuel heating value increasing rate. The effective carbon recovery rate was taken as the chief indicator for choosing the right operating conditions, determining a best methane space velocity of 680 mL/(gcat·h). With the increase of S/C, total enthalpy increasing rate had a significant improvement; wall temperature had a positive effect on reforming, especially in synergistic catalysis. The effect of input power was linked with wall temperature in parallel synergistic reforming, with a greater effect at a higher temperature. Combining the experimental results with the theory analysis, parallel synergistic reforming is best, with a methane conversion of 51.23% and total enthalpy increasing rate of 25.73% at a wall temperature of 500 °C, an input power of 84.53 W, and an S/C value of 2.

Research of Methane Reforming and Combustion Characteristics in Chemically Recuperated Gas Turbine

In this study, the methane steam reforming test bed is designed and built under the parameters of a chemically recuperated gas turbine (CRGT); relevant experimental research about fuel reforming is also conducted. Three kinds of reforming are used, including catalyst reforming, plasma reforming, and apposition synergy reforming. Methane conversion and fuel calorific value increase rate are discussed, and the performance of synergy is best. Synergy reforming is an effective measure to improve disadvantages of the plasma and catalyst reaction process. In addition, combustion characteristics are compared and analyzed using reformed gas in a diffusion flame. The flame is shortened and becomes narrow due to the inflammability of H2, and the maximum temperature of flame drops almost 500 K because of the water steam in reformed gas. Ultralow NOx emission is calculated in a jet flame, which is the key advantage of CRGT.

Effect of Dual Fuel Nozzle Structures on Combustion Flow Field in CRGT Combustor

Three different structures of a new dual fuel nozzle design concept (inner swirl nozzle, double swirl nozzle, and outer swirl nozzle) were developed for the chemically recuperated gas turbine (CRGT) combustor. The combustion flow fields in the combustor with the three nozzles were investigated, respectively, based on the FLUENT simulation. The realizable <svg style="vertical-align:-0.13794pt;width:8.6750002px;" id="M1" height="12.4375" version="1.1" viewBox="0 0 8.6750002 12.4375" width="8.6750002" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,12.162)"><path id="x1D458" d="M480 416q0 -21 -18 -41q-9 -11 -17 -7q-20 9 -42 9q-62 0 -140 -78q23 -69 88 -192q17 -31 27 -42t20 -11q16 0 62 46l17 -20q-64 -92 -119 -92q-35 0 -70 66q-41 73 -84 187q-36 -30 -62 -61q-27 -115 -35 -172q-41 -8 -78 -20l-6 6l140 612q7 28 0.5 34t-37.5 7l-34 1&#xA;l5 26q38 4 74 13.5t57 17t25 7.5q12 0 4 -32l-104 -443h2q35 38 97 93q39 35 65.5 56t62 41.5t58.5 20.5q19 0 30.5 -10t11.5 -22z" /></g> </svg>-<svg style="vertical-align:-0.13794pt;width:7.0999999px;" id="M2" height="7.9499998" version="1.1" viewBox="0 0 7.0999999 7.9499998" width="7.0999999" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,7.675)"><path id="x1D700" d="M387 375q0 -16 -17 -31t-29 -15q-9 0 -12 13q-13 74 -80 74q-36 0 -61 -24.5t-25 -56.5t24 -51.5t68 -19.5q33 0 47 2l2 -7l-32 -42q-20 2 -54 2q-45 0 -74 -21.5t-29 -60.5q0 -41 28 -65.5t73 -24.5q78 0 145 67l17 -23q-33 -47 -84.5 -75t-111.5 -28q-70 0 -114.5 35.5&#xA;t-44.5 92.5q0 46 38 78t95 45v2q-35 10 -54.5 33t-19.5 52q0 55 53 88.5t122 33.5q67 0 98.5 -23.5t31.5 -49.5z" /></g> </svg> model and PDF model were adopted, respectively, for the turbulence flow and nonpremixed reformed gas combustion. The obtained results using these models showed good agreement with experimental results in original oil combustor. The effects of different dual fuel nozzle structures on the flow field, fuel concentration distribution, and temperature distribution in the combustor were simulated and analyzed. Results suggest that the double swirl nozzle and outer swirl nozzle can form a better flow field with obvious central recirculation zone (CRZ), shorten fuel and air mixing distance, and obtain a more uniform outlet temperature distribution, in comparison with the inner swirl nozzle. However, compared with double swirl nozzle, the outer swirl nozzle can result in a better combustion flow field with the high temperature region in the CRZ, which is important to stabilize the flame.

CFD Modeling of Exhaust Heat Recovery Using Methane Steam Reforming in Steam Reformer of Chemically Recuperated Gas Turbine

To ensure the maximum exhaust heat recovery in different working conditions in Steam Reformer (SR) of Chemically Recuperated Gas Turbine (CRGT), this paper studied the influence of steam to carbon ratio (S/C), reformer inlet temperature, and total mass flow rate in catalytic bed on the reactant conversion, product selectivity, heat recovery rate and fuel calorific value increasing rate by numerical simulation. It’s noted that the working parameters are given based on the chemically recuperated test bench. The model considered catalytic bed as porous media region using Fluent, including fluid flow, heat transfer and chemical reactions on reformer. Chemical reaction rates were implemented in C language and were used as a User-Defined Function (UDF) in Fluent. As a result, in single stage SR, namely the insulating tubular reactor, the reactant temperature and concentration continually decline along the axial position, especially in the inlet decline significantly. The higher inlet temperature is better for reactant conversion and heat recovery rate. When steam mass flow is fixed, the higher S/C is, the lower heat recovery rate is. In a certain total mass flow rate, the length L of reaction zone has no significant influence on the reactant conversion, product selectivity, heat recovery rate and the fuel calorific value increasing rate. When the length L is fixed, as total mass flow rate increases, methane conversion and fuel calorific value increasing rate reduce, while, heat recovery rate increases. The proposed research confirms optimal fuel mass flow and S/C in reformer under certain working conditions, and provides the basis for operation and regulation of Chemically Recuperated Test Bench.

Use of Low/Mid-Temperature Solar Heat for Thermochemical Upgrading of Energy, Part I: Application to a Novel Chemically-Recuperated Gas-Turbine Power Generation (SOLRGT) System

This paper is the first part of a study presenting the concept of indirect thermochemical upgrading of low/mid temperature solar heat, and demonstration of its integration into a high efficiency novel hybrid power generation system. The proposed system consists of an intercooled chemically recuperated gas turbine (SOLRGT) cycle, in which the solar thermal energy collected at about 220 °C is first transformed into the latent heat of vapor supplied to a reformer and then via the reforming reactions to the produced syngas chemical exergy. The produced syngas is burned to provide high temperature working fluid to a gas turbine. The solar-driven steam production helps to improve both the chemical and thermal recuperation in the system. Using well established technologies including steam reforming and low/mid temperature solar heat collection, the hybrid system exhibits promising performance: the net solar-to-electricity efficiency, based on the gross solar thermal energy incident on the collector, was predicted to be 25–30%, and up to 38% when the solar share is reduced. In comparison to a conventional CRGT system, 20% of fossil fuel saving is feasible with the solar thermal share of 22%, and the system overall efficiency reaches 51.2% to 53.6% when the solar thermal share is increased from 11 to 28.8%. The overall efficiency is about 5.6%-points higher than that of a comparable intercooled CRGT system without solar assist. Production of NOx is near zero, and the reduction of fossil fuel use results in a commensurate ∼20% reduction of CO2 emissions. Comparison of the fuel-based efficiencies of the SOLRGT and a conventional commercial Combined Cycle (CC) shows that the efficiency of SOLRGT becomes higher than that of CC when the solar thermal fraction Xsol is above ∼14%, and since the SOLRGT system thus uses up to 12% less fossil fuel than the CC (within the parameter range of this study), it commensurately reduces CO2 emissions and saves depletable fossil fuel. An economic analysis of SOLRGT shows that the generated electricity cost by the system is about 0.06 $/kWh, and the payback period about 10.7 years (including 2 years of construction). The second part of the study is a separate paper (Part II) describing an advancement of this system guided by the exergy analysis of SOLRGT.

Use of Low/Mid-Temperature Solar Heat for Thermochemical Upgrading of Energy, Part II: A Novel Zero-Emissions Design (ZE-SOLRGT) of the Solar Chemically-Recuperated Gas-Turbine Power Generation System (SOLRGT) guided by its Exergy Analysis

This paper adds an exergy analysis of the novel SOLRGT solar-assisted power generation system proposed and described in detail in Part I of this study (Zhang and Lior, 2012, “Use of Low/Mid-Temperature Solar Heat for Thermochemical Upgrading of Energy, Part I: Application to a Novel Chemically-Recuperated Gas-Turbine Power Generation (SOLRGT) System,” ASME J. Eng. Gas Turbines Power, Accepted. SOLRGT is an intercooled chemically recuperated gas turbine cycle, in which solar thermal energy collected at about 220 °C is first transformed into the latent heat of water vapor supplied to a reformer, and then via the reforming reactions to the produced syngas chemical exergy. This integration of this concept of indirect thermochemical upgrading of low/mid temperature solar heat has resulted in a high efficiency novel hybrid power generation system. In Part I it was shown that the solar-driven steam production helps improve both the chemical and thermal recuperation in the system, with both processes contributing to the overall efficiency improvement of about 5.6%-points above that of a comparable intercooled CRGT system without solar assist, and nearly 20% reduction of CO2 emissions. An economic analysis of SOLRGT predicted that the generated electricity cost by the system is about 0.06 $/kWh, and the payback period about 10.7 years (including two years of construction). The exergy analysis of SOLRGT in this (Part II) paper identified that the main potentials for efficiency improvement is in the combustion, the turbine and compressors, and in the flue gas due to its large water vapor content. Guided by this, an improved solar-assisted zero-emissions power generation system configuration with oxy-fuel combustion and CO2 capture, ZE-SOLRGT, is hereby proposed, in which the exergy losses associated with combustion and heat dumping to the environment are reduced significantly. The analysis predicts that this novel system with an 18% solar heat input share has a thermal efficiency of 50.7% and exergy efficiency of 53%, with ∼100% CO2 capture.

Proposal and analysis of a dual-purpose system integrating a chemically recuperated gas turbine cycle with thermal seawater desalination

A novel cogeneration system is proposed for power generation and seawater desalination. It combines the CRGT (chemically recuperated gas turbine) with the MED-TVC (multi-effect thermal vapor compression desalination) system. The CRGT contains a MSR (methane-steam reformer). The produced syngas includes plenty of steam and hydrogen, so the working medium flow increases and NO x emissions can achieve 1 ppm low. However, the water consumption is large, ∼23 t/d water per MW power output. To solve this problem and produce water for sale, MED-TVC is introduced, driven by exhaust heat. Such a dual-purpose plant was analyzed to investigate its performance and parameter selection, and compared with four conventional cogeneration systems with the same methane input. Some main results are following: In the base case of the CRGT with a TIT of 1308 °C and a compression ratio of 15, the MED-TVC with 9 effects, the specific work output, performance ratio and CRGT-consumed water ratio are 491.5 kJ/kg, 11.3 and 18.2%, respectively. Compared with the backpressure ST (steam turbine)/CC (combined cycle) plus MED/MSF (multistage flash), the CRGT + MED has better thermal performance, lower product cost and shorter payback period, which indicates the CRGT + MED dual-purpose system is a feasible and attractive choice for power and water cogeneration.

155 ジメチルエーテルを燃料とした化学再生ガスタービン : マイクロコージェネレーションシステムの熱的性能解析による運転特性評価(エンジンシステム/動力エネルギシステム,一般講演)

155 ジメチルエーテルを燃料とした化学再生ガスタービン : マイクロコージェネレーションシステムの熱的性能解析による運転特性評価(エンジンシステム/動力エネルギシステム,一般講演)

G0800-2-2 ジメチルエーテルを燃料とした化学再生ガスタービンシステムの熱的性能解析による運転特性評価(動力エネルギーシステム部門一般講演(2))

Dimethyl ether (DME), which is attracting fuel as a clean and manageable fuel, is considered to apply to Chemically Recuperated Gas Turbine (CRGT) system. CRGT system is improved by reforming the fuel mixed with steam for the hydrogen-rich gas by recovering the exhaust heat of gas turbine. In this study, to construct the optimum CRGT system, a thermal performance analysis of the CRGT system fueled by DME was performed. And then dependence of the several parameters on the reformed gas LHV and the generator output was obtained.

E107 30kW発電試験によるDME化学再生ガスタービンの性能評価(OS-4 省エネルギー・小型分散電源・コジェネ技術,一般講演,地球温暖化防止と動力エネルギー技術)

Chemically Recuperated Gas Turbine (CRGT) is an advanced GT cycle that can increase power generation efficiency by recovering the exhaust heat with endothermic reaction of steam reforming. The CRGT fueled by Dimethyl Ether (DME) was demonstrated using 30kW Micro GT (MGT) as a project funded by METI from 2003 to 2007 and accomplished both 10% reduction of fuel consumption compared with steam injected GT cycle, which is similar proven technology, and NO_x emission level of less than 10ppm. Alternative fuel nozzle had concentric double pipe, one of which was designed to burn DME directly with diffusive combustion, and the other was premixed combustion of low-BTU reformed gas. The reformer, which was designed to fit into the MGT and consisted of 96 SS316-tubes filled with Pt catalyst and alumina balls, top and bottom headers and rectangular duct, recovered 15.3kW heat from exhaust gas and increase fuel heating value by 7.9%. This report provides not only these results but also a lot of useful information including concise specification, designing process and verification test of each mechanical and electrical component, and relevant issues and solutions as well.

Numerical Analysis for Chemical Recuperated Gas Turbine System (CRGT) Fuelled by Bio-Ethanol

Chemically recuperated Gas Turbine (CRGT) that recovers exhaust heat by endothermic reaction converting fuel to reforming gas is one of candidates for effective utilization of ethanol from biomass fermentation. Bio-ethanol can easily be applied to steam reforming process for hydrogen-rich gas production, because the moisture in bio-ethanol is included about 80% after the fermentation process. The chemical composition in reformer was evaluated according to chemical equilibrium equations. This numerical analysis reports a performance comparison with simple cycle gas turbine. Thermochemical recuperation in the ethanol was allowed to achieve a significant change in power output, and the maximum increase in thermal efficiency was 16% compared with simple cycle at 8.0 in steam/fuel molar ratio and 600 deg. C in reforming temperature.

Cascade utilization of chemical energy of natural gas in an improved CRGT cycle

In this paper three advanced power systems: the chemically recuperated gas turbine (CRGT) cycle, the steam injected gas turbine (STIG) cycle and the combined cycle (CC), are investigated and compared by means of exergy analysis. Making use of the energy level concept, cascaded use of the chemical exergy of natural gas in a CRGT cycle is clarified, and its performance of the utilization of chemical energy is evaluated. Based on this evaluation, a new CRGT cycle is designed to convert the exergy of natural gas more efficiently into electrical power. As a result, the exergy efficiency of the new CRGT cycle is about 55%, which is 8 percentage points higher than that of the reference CRGT cycle. The analysis gave a better interpretation of the inefficiencies of the CRGT cycle and suggested improvement options. This new approach can be used to design innovative energy systems.

A new approach of cascade utilization of the chemical energy of fuel*

Abstract The indirect release of chemical energy of fuel is investigated, and a new machine is proposed to identify the cascade utilization of chemical energy of fuel more clearly. Based on the concept of energy level, the internal phenomenon of the indirect chemical energy release is disclosed, and the equations of energy level describing the utilization of chemical energy and thermal energy during the indirect chemical energy release process are obtained. From theoretical analysis, we find that the superiority of the indirect chemical energy release of fuel comes from the cascade utilization of the fuel's chemical energy. Moreover, the cascade utilization of chemical energy is verified by the investigation of CRGT(chemically recuperated gas turbine). As a result, the thermal exergy obtained from the chemical energy release of fuel increases by 2%-3%. The results obtained here may help a deeper understanding of indirect chemical energy release of fuel and provide a theoretical basis for the synthesis of ...