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The porous media combustion technology is an effective solution to stable combustion and clean utilization of low heating value gas. For observing the combustion characteristics of porous media burners under various back pressures, investigating flame stability and figuring out the distribution laws of combustion gas flow and resistance loss, so as to achieve an optimized design and efficient operation of the devices, a bench of foamed ceramics porous media combustion devices was thus set up to test the cold-state resistance and hot-state combustion characteristic of burners in working conditions without back pressures and with two different back pressures. The following results are achieved from this experimental study. (1) The strong thermal reflux of porous media can preheat the premixed air effectively, so the flame can be kept stable easily, the combustion equivalent ratio of porous media burners is lower than that of traditional burners, and its pollutant content of flue gas is much lower than the national standard value. (2) The friction coefficient of foamed ceramics decreases with the increase of air flow rate, and its decreasing rate slows down gradually. (3) When the flow rate of air is low, viscosity is the dominant flow resistance, and the friction coefficient is in an inverse relation with the flow rate. (4) As the flow rate of air increases, inertia is the dominant flow resistance, and the friction coefficient is mainly influenced by the roughness and cracks of foamed ceramics. (5) After the introduction of secondary air, the minimum equivalent ratio of porous media burners gets much lower and its range of equivalent ratio is much larger than that of traditional burners.

The exhaust gas temperature of SOFC is as high as 600–1000 °C and contains combustible components that can be reused. In this paper, an experimental system was set up to study the combustion characteristics of SOFC simulated exhaust gas in a porous medium burner, the combustion of SOFC exhaust gas under different equivalence ratio, the effects of hydrogen concentration and water vapor fraction in the anode exhaust gas and the stable combustion limits of the burners had been analyzed. Results showed that: equivalence ratio and adiabatic flame temperature had a significant effect on the combustion, when the adiabatic flame temperature of mixed gas below 440 °C, or the water vapor content in the anode gas was greater than 85%, the flame couldn’t be stably burned; On the condition of the fuel utilization rate of 60% and the equivalence ratio of 0.40, the burner could burn stably with the inlet airflow velocity from 0.16 to 0.24m/s; The combustion stability limit of the exhaust gas burner varied with the utilization ratio of the stack, with increasing of fuel utilization ratio, the equivalence ratio of lifting and flashback limit was changing, and the adiabatic flame temperature of stable combustion limit had been studied.

Scientific analyses and the provision of practical ways of improving the hydraulic reliability of urban high-pressure gas networks are essential for the safe and stable supply of natural gas by a supplier. A reasonable estimation of the actual obtainable flow for each consumer in the event of a failure is key to the quantitative analysis of hydraulic reliability, which is not an easy task for a loop network. Based on an analysis of the hydraulic characteristics of a loop network, this paper discusses the limitations of existing methods and presents a feasible method for determining the actual nodal flow in a high-pressure gas network loop. This method adopts a process whereby the hydraulic regimes are first analysed according to the designed nodal flow. Next, the nodal pressures are checked, and the actual nodal flow is gradually rectified. Finally, the hydraulic regimes are repeatedly analysed according to the rectified flow until each nodal pressure and each nodal flow satisfy the nodal pressure equations. Moreover, a detailed procedure for a hydraulic reliability analysis of a loop network is presented, and its feasibility is confirmed with an example. The example results show that the network system hydraulic reliability is only 0.879 using the proposed method when pipe 2 fails, whereas the reliability would become 1.0 if using the existing method. The factors affecting the reliability are discussed exhaustively from the aspects of the network system and the consumer, and a number of measures are suggested for improving the hydraulic reliability.

This paper presents theoretical and experiment analysis of a hybrid residential hot water (HRHW) supplying system with domestic solar water heater (DSWH) and gas instantaneous water heater (GIWH) in shanghai. Mathematical model of the system has been established and its validity was tested by experiments. Economic analysis has been conducted for the HRHW system and traditional gas water heater systems through simulation along with Shanghai weather condition considering the influence of different minimum temperature rise (MTR) of GIWH. The economic comparison results show that the HRHW supplying system has greater economic benefits than gas water heater with a payback period of 7.2 years, and minimum temperature rise (MRT) of GIWH has low impacts on the supplementary gas consumption for the case in shanghai. For other region, operation of the HRHW system needs precise simulation according to the local meteorological conditions.

The economic benefit gained from a combined cooling heating and power (CCHP) system depends on many factors. It is essential to optimize the system configuration and operational scheme as early in the design stage as possible. In this paper, a sizing optimization model (SOM) focused on the minimum annual total cost ( ATC ) and an operational optimization model (OOM) focused on the minimum annual energy charge ( AEC ) were established. The former was used to determine the optimal capacity of a CCHP system, whereas the latter was used to provide the optimal schemes. Both the SOM and OOM contain large numbers of hourly linear programming (LP) models, and the solution processes of both models proved to be quite time-consuming when the conventional iterative method was used. In this study, a piecewise elimination method was proposed for hourly LP models, and a graphical method in which the iteration was converted to an algebraic matrix was introduced to greatly improve the computational efficiency. The results demonstrated that the calculation time was reduced from 84.496 s for the conventional solution to 0.017 s for the graphical method in the OOM. The CCHP system SOM contains an OOM, and the calculation time was only 0.41 s when using the graphical method, whereas the conventional iterative method took 2367 s. The impact of gas price upon the optimal operational schemes and the equipment capacity was discussed for a building application in Shanghai. The improved efficiency of the calculation method could be helpful to compare different schemes and to perform sensitivity analyses.

In this paper, the flame stability of partially premixed combustion for pipeline natural gas (PNG) and liquefied natural gas (LNG) interchangeability was investigated. A wide range of primary air ratio was considered and the characteristics of yellow flame and lifted flame were emphasized. The effect of gas flame speed (Sn), flame inner core height (h), gas flow rate (Lg), air flow rate (La), port thermal intensity (qp) and burner head temperature were discussed. Experiments showed that flame speed and flame inner cone height were mainly affected by gas components and lifted flame was influenced by flame speed and burner head temperature. When gases were interchanged, the flame speed and lifted flame could not be simply predicted by Wobbe index. When gas wobbe index increased, more chances yellow flame would appear and the gases with similar wobbe indexes have similar performance of yellow flame characteristics.

Almost all of finished household biogas plants in China incorporated medium-temperature fermentation and no auxiliary heating were integrated. Accordingly the production efficiency was quite poor due to lack of reasonable thermal support. Meanwhile solar-collector became more and more popular accompanied with decreasing cost resulting from mass production. A solar-assisted biogas system was put forward and experimentally investigated in this paper. The initiative was to combine popularly-available house biogas plant with solar-collector at a reasonable cost, therefore to maintain year-round operation of biogas plant and to produce enough amount of biogas in winter for daily use. The recorded data in a pilot project revealed that additional electricity consumed accounted to only 7.2% of biogas produced, suggesting an economically feasible approach.

Stray current corrosion (SCC) is the most severe form of electrochemical corrosion to buried metallic structure. With the development of rail transportation and gas industry, the SCC of buried gas pipelines is becoming more serious in china. In this paper, principle and characteristic of Stray Current (SC) resulting from rail transit system were introduced. Presently available SC testing methods, equipment, and determination standards in china were summarized. For an underground gas pipeline located in the neighboring area and parallel to the rail transit in Shanghai, pipe-to-soil potential, potential gradient of soil, current within pipeline were measured during different operation time of rail transit with a self-made SC monitoring system based upon virtual instrument. Result shows that pipe-to-soil potential fluctuation of the tested gas pipeline is 200 mV, current within pipeline and potential gradient of soil is 100 mA, and 62 mV/m respectively, which is consistent with the operation of rail transit, serious corrosion of the buried gas pipeline may occur. Through theoretical Analysis, several protective measures were introduced.

In China, the imported Liquefied Natural Gas (LNG) has been steadily increased in past years, with its constituents different from those of traditional pipeline natural gases (PNG) to various extents. In this paper several natural gases to be delivered to Guangdong provinces in China were selected as test gases to measure performance response of 17 sets of domestic gas cookers. Heat input rating, CO and NO x emission, and thermal efficiency was measured according to related national standards. American Gas Association indexes and Weaver indexes were used to predict combustion stability and emission under different gas constituents. Experiment results were compared with prediction to analyze the applicability of the two well-established indexes systems. It was concluded that Wobbe Index can predict heat input rating quite accurately, and CO and NO x emissions can be remained with reasonable limits for the changing constituents discussed. For combustion stability prediction, judgment criteria should be adjusted as follows: Weaver lifting index from J L ≥ 0.64 to J L ≥ 0.95, Weaver incomplete combustion index from J I ≤ 0.05 to J I ≤ 0.04, and AGA lifting index from I L ≤ 1.10 to I L ≤ 1.05.