Effects of different combustion modes on the thermal efficiency and emissions of a diesel pilot-ignited natural gas engine under low-medium loads

Research on dual-fuel(DF)engines has become increasingly important as engine manufacturers seek to reduce carbon dioxide emissions.There are significant advantages of using diesel pilot-ignited natural gas engines as DF engines.However,different combustion modes exist due to variations in the formation of the mixture.This research used a simulation model and numerical simulations to explore the combustion characteristics of high-pressure direct injection(HPDI),partially premixed compression ignition(PPCI),and double pilot injection premixed compression ignition(DPPCI)combustion modes under a low-medium load.The results revealed that the DPPCI combustion mode provides higher gross indicated thermal efficiency and more acceptable total hydrocarbon(THC)emission levels than the other modes.Due to its relatively good performance,an experimental study was conducted on the DPPCI mode engine to evaluate the impact of the diesel dual-injection strategy on the combustion process.In the DPPCI mode,a delay in the second pilot ignition injection time increased THC emissions(a maximum value of 4.27g/(kW·h)),decreased the emission of nitrogen oxides(a maximum value of 7.64 g/(kW·h)),increased and then subsequently decreased the gross indicated thermal efficiency values,which reached 50.4%under low-medium loads.

Influence of the Ambient Temperature on the Efficiency of Gas Turbines

In hot and arid regions like the Saharan area,effective methods for cooling and humidifying intake air are essential.This study explores the utilization of a water trickle cooler as a promising solution to meet this objective.In particular,the HASSI MESSAOUD area is considered as a testbed.The water trickle cooler is chosen for its adaptability to arid conditions.Modeling results demonstrate its effectiveness in conditioning air before it enters the compressor.The cooling system achieves a significant temperature reduction of 6 to 8 degrees Celsius,enhancing mass flow rate dynamics by 3 percent compared to standard cases without cooling.Moreover,the cooling system contributes to a remarkable 10 percent reduction in power consumption of gas turbines and a notable 10 percent increase in turbine efficiency.These findings highlight the potential of water trickle coolers in improving the performance and efficiency of gas turbine systems in hot and dry climates.

Application of Supercritical CO2 Gas Turbine for the Fossil Fired Thermal Plant

A supercritical CO2 gas turbine cycle can produce power at high efficiency and the gas turbine is compact compared with the steam turbine. Therefore, it is very advantageous power cycle for the medium temperature range less than 650 ℃. The purpose of this paper is to show how it can be effectively applied not only to the nuclear power but also to the fossil fired power plant. A design of 300 MWe plant has been carried out, where thermal energy of flue gas leaving a CO2 heater is utilized effectively by means of economizer and a high cycle thermal efficiency of 43.4 % has been achieved. Since the temperature and the pressure difference of the CO2 heater are very high, the structural design becomes very difficult. It is revealed that this problem can be effectively solved by introducing a double expansion turbine cycle. The component designs of the CO2 heater, the economizer, supercritical CO2 turbines, compressors and the recuperators are given and it is shown that these components have good performances and compact sizes.

Evaluation of the Influence of Ambient Temperature on the Performance of the Trans-Amadi Gas Turbine Plant

This paper examines the effects of ambient temperature on the Trans-Amadi gas turbine power station Phase II. The investigation took thirteen (13) months (January 2012 to January 2013) during which plant data were monitored and operational Logsheets like turbine logsheets, plant—auxiliaries’ logsheets and generator logsheets were studied. The gas turbine (GT) that was under investigation was GT-2: MS5001 Nuovopignone with designed installed capacity of 25.0 Megawatts (MW). The result of the study shows that a 1℃ rise of the ambient temperature is responsible for the following: 0% - 0.12% decrease in the power output, 0% - 0.12% increase in the power differential, 0% - 1.17% decrease in the thermal efficiency, 0% - 27.18% increase in the heat rate and 0% - 3.57% increase in the specific fuel consumption. An ambient temperature of 30℃ is found to yield minimal fuel consumption.

Influence of quantum degeneracy on the performance of a gas Stirling engine cycle

Based on the state equation of an ideal quantum gas, the regenerative loss of a Stirling engine cycle working with an ideal quantum gas is calculated. Thermal efficiency of the cycle is derived. Furthermore, under the condition of quantum degeneracy, several special thermal efficiencies are discussed. Ratios of thermal efficiencies versus the temperature ratio and volume ratio of the cycle are made. It is found that the thermal efficiency of the cycle not only depends on high and low temperatures but also on maximum and minimum volumes. In a classical gas state the thermal efficiency of the cycle is equal to that of the Carnot cycle. In an ideal quantum gas state the thermal efficiency of the cycle is smaller than that of the Carnot cycle. This will be significant for deeper understanding of the gas Stirling engine cycle.

Comparison of thermal neutron detection ef f iciency of 6Li scintillation glass and 3He gas proportional tube

We report on a comparison study of the 3He gas proportional tube and the 6Li incorporated scintillation glasses on thermal neutron detection efficiency. Both 3He and 6Li are used commonly for thermal neutron detection because of their high neutron capture absorption coefficient. By using a neutron source 252Cf and a paraffin moderator in an alignment system, we can get a small beam of thermal neutrons. A flash ADC is used to measure the thermal neutron spectrum of each detector, and the detected number of events is determined from the spectrum, then we can calculate the detection efficiency of different detectors. Meanwhile, the experiment has been modeled with GEANT4 to validate the results against the Monte Carlo simulation.

Performance,combustion,and emission characteristics of on a diesel engine fuelled with hydrogen compressed natural gas and Kusum seed biodiesel

Renewable fuels have many advantages over fossil fuels because they are biodegradable and sustainable,and help mitigate social and environmental problems.The objective of the present study is to evaluate the performance,combustion,and emission characteristics of a compression–ignition engine using hydrogen compressed natural gas(HCNG)-enriched Kusum seed biodiesel blend(KSOBD20).The flow rate of HCNG was set at 5 L/min,10 L/min,and 15 L/min,and the injection pressure was varied in the range of 180 bar to 240 bar.Brake thermal efficiency(BTE)and brake-specific fuel consumption(BSFC)were improved when HCNG was added to the KSOBD20.Combustion characteristics,namely,cylinder pressure(CP)and net heat release rate(NHRR),were also improved.Emissions of carbon monoxide(CO),hydrocarbons(HC),and smoke were also reduced,with the exception of nitrogen oxides(NO_(x)).The higher injection pressure(240 bar)had a positive effect on the operating characteristics.At an injection pressure of 240 bar,for KSOB20+15 L/min HCNG,the highest BTE and the lowest BSFC were found to be 32.09%and 0.227 kg/kWh,respectively.Also,the CP and NHRR were 69.34 bar and 66.04 J/°.CO,HC,and smoke levels were finally reduced to 0.013%,47×10^(-6)and 9%,respectively,with NO_(x)levels at 1623×10^(-6).For optimum results in terms of engine characteristics,the fuel combination KSOBD20+15 L/min HCNG at FIP 240 bar is recommended.

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.

Distributed Gas Ignition Using Injection Strategy for High Efficiency and Clean Combustion Under Lean Condition

Jet ignition is an efficient way to achieve lean burn of the engine and a promising strategy to meet the stringent emission regulations in the future.This paper presents a distributed gas ignition(DGI)combustion concept and realizes a DGI combustion mode using a newly designed DGI igniter.The igniter integrates a fuel injector and a spark plug to achieve minimum volume and easy installation.As the mixture preparation within the jet chamber is essential for the performance of the igniter,different jet chamber injection strategies were tested with varying excess air-fuel ratio ranging from 1.4 to 2.0.By addressing the dual injection strategy,the ignition delay and combustion duration were improved evidently.Compared with the single injection strategy,dual injection strategy improves the flexibility when preparing the mixture inside the jet chamber and therefore retains more fuel.The increased energy density of the jet chamber helps to generate more energetic jets under dual injection strategy,resulting in the improvement of ignition and combustion performance with lean burn.A higher thermal efficiency and a leaner limit of the engine are attained with dual injection than that with single injection.Dual injection exhibits its potential in reducing CO and THC emissions to an acceptable level with leaner mixture.Based on dual injection strategy,the maximum indicated thermal efficiency of 45%is achieved.

Life cycle evaluation of an intercooled gas turbine plant used in conjunction with renewable energy

The life cycle estimation of power plants is important for gas turbine operators.With the introduction of wind energy into the grid,gas turbine operators now operate their plants in Load–Following modes as back-ups to the renewable energy sources which include wind,solar,etc.The motive behind this study is to look at how much life is consumed when an intercooled power plant with 100 MW power output is used in conjunction with wind energy.This operation causes fluctuations because the wind energy is unpredictable and overtime causes adverse effects on the life of the plant–The High Pressure Turbine Blades.Such fluctuations give rise to low cycle fatigue and creep failure of the blades depending on the operating regime used.A performance based model that is capable of estimating the life consumed of an intercooled power plant has been developed.The model has the capability of estimating the life consumed based on seasonal power demands and operations.An in-depth comparison was undertaken on the life consumed during the seasons of operation and arrives at the conclusion that during summer,the creep and low cycle life is consumed higher than the rest periods.A comparison was also made to determine the life consumed between Load–Following and stop/start operating scenarios.It was also observed that daily creep life consumption in summer was higher than the winter period in-spite of having lower average daily operating hours in a Start–Stop operating scenario.

Performance Characteristics of n-Butanol-Diesel Fuel Blend Fired in a Turbo-Charged Compression Ignition Engine

In this study, n-butanol-diesel blends were burned in a turbo-charged, direct injection diesel engine where the brake thermal efficiency, (BTE) or brake specific fuel consumption, (BSFC) was compared with that of ethanol-diesel or methanol-diesel blends in another study by other authors. The test blends used were B5, B10 and B20 (where B5 is 5% n-butanol by volume and 95% diesel fuel-DF). In this study, the BTE was higher and the BSFC improved more than in the other study. Because of improved BTE with increasing brake mean effective pressure, BMEP, the BSFC reduced, however the increased shared volume of n-butanol in DF increased BSFC. Adding n-butanol in DF slightly derated the torque, brake power output with increasing speed, and caused a fall in exhaust gas temperatures, (EGT) which improves the volumetric efficiency and reduces compression work. Therefore, a small-shared volume of n-butanol in DF fired in a turbo-charged diesel engine performs better in terms of BTE and BSFC than that of ethanol or methanol blending in DF.

电磁灶热效率测量不确定度研究

为了提升测试精度,测试电磁灶热效率时需要评定不确定度。系统分析了电磁灶产品热效率测试的影响因素,主要影响因素为水质量的测量和水温的测量,分析了负载锅的主要指标和影响测试精度的原因,并提出了提升测试精度的措施。分别采用GUM法和MCM法评定电磁灶热效率的测量不确定度。GUM法评定结果为:电磁灶热效率测量结果为86.93%,95%包含概率下的对称包含区间为[86.65%,87.21%];自适应MCM法计算为:热效率测量结果为86.93%,95%包含概率下的对称包含区间为[86.65%,87.21%]。对两种方法得到的结果进行了比较验证,两种方法得到的结果基本一致。与GUM法相比,MCM法评定不确定度过程更加简单,大大降低了计算工作量。

家用燃气灶热效率测量及不确定度评定

按照GB16410-2007家用燃气灶热效率的测量原理和方法,对测量结果进行了不确定度评定,分析了各输入量对评定结果的影响情况。作为对比,分析了标准状态改变和按旧国标测量时的热效率不确定度。结果表明:铝锅修正系数、上下限锅正投影面积、试验气标态低热值和水的温升对家用灶热效率测量结果影响较大,影响程度依次降低。折算系数、测量时间和实验水量的测量不确定度可忽略不计。标准状态的改变对热效率测量结果不确定度评定的影响很小。相比旧国标,新国标测量结果具有更大的不确定度。

Conjugate Heat Transfer Investigation on the Cooling Performance of Air Cooled Turbine Blade with Thermal Barrier Coating

A hot wind tunnel of annular cascade test rig is established for measuring temperature distribution on a real gas turbine blade surface with infrared camera.Besides,conjugate heat transfer numerical simulation is performed to obtain cooling efficiency distribution on both blade substrate surface and coating surface for comparison.The effect of thermal barrier coating on the overall cooling performance for blades is compared under varied mass flow rate of coolant,and spatial difference is also discussed.Results indicate that the cooling efficiency in the leading edge and trailing edge areas of the blade is the lowest.The cooling performance is not only influenced by the internal cooling structures layout inside the blade but also by the flow condition of the mainstream in the external cascade path.Thermal barrier effects of the coating vary at different regions of the blade surface,where higher internal cooling performance exists,more effective the thermal barrier will be,which means the thermal protection effect of coatings is remarkable in these regions.At the designed mass flow ratio condition,the cooling efficiency on the pressure side varies by 0.13 for the coating surface and substrate surface,while this value is 0.09 on the suction side.

燃气灶热效率测量不确定度的分析

测量不确定度的计算是《检测和校准实验室认可准则》(ISO/IEC 17025:2005)的明确要求,成为对实验室认可的重要内容。以燃气灶热效率测试为例,根据多年测试经验,对燃气灶热效率测试过程中的不确定度进行分析,从而提高实验室的燃气灶热效率测量不确定度评定水平。