05/02681 Temperature and air-fuel ratio dependent specific heat ratio functions for lean burned and unburned mixture

The factors affecting knock resistance of fuels, including hydrogen (H2), ethane (C2H6), propane (C3H8), normal butane (n-C4H10), and iso-butane (i-C4H10), were determined using modeling and engine operation tests with spark-ignition gas engines. The results of zero-dimensional detailed chemical kinetic computations indicated that H2 had the longest ignition delay time of these gaseous fuels. Thus, H2 possessed the lowest ignitability. The results of engine operation tests indicated that H2 was the fuel most likely to result in knocking. The use of H2 as the fuel produced a temperature profile of the unburned gas compressed by the piston and flame front that was higher than that of the other fuels due to the high-specific heat ratio and burning velocity of H2. The relation between knock resistance and secondary fuel ratio in methane-based fuel blends also was investigated using methane (CH4) as the primary component, and H2, C2H6, C3H8, n-C4H10, or i-C4H10 as the secondary components. When the secondary fuel ratio was small, the CH4/H2 blend possessed the lowest knocking tendency. But as the secondary fuel ratio increased, the CH4/H2 mixture possessed a greater tendency to knock than CH4/C2H6 due to the high-specific heat ratio and burning velocity of H2. These results indicate that the knocking that can occur with gaseous fuels is not only dependent on the ignitability of the fuel but it also the specific heat ratio and burning velocity.

Download Full-text

Factors Determining Anti-Knocking Properties of Gaseous Fuels in Spark Ignition Gas Engines

Volume 1: Large Bore Engines; Fuels; Advanced Combustion ◽

10.1115/icef2015-1079 ◽

2015 ◽

Author(s):

Hiroki Tanaka ◽

Kazunobu Kobayashi ◽

Takahiro Sako ◽

Kazunari Kuwahara ◽

Hiroshi Kawanabe ◽

...

Keyword(s):

Specific Heat ◽

Burning Velocity ◽

Spark Ignition ◽

Primary Component ◽

Engine Operation ◽

Specific Heat Ratio ◽

Gaseous Fuels ◽

Fuel Ratio ◽

Secondary Fuel ◽

High Specific Heat

The factors affecting knock resistance of fuels, including hydrogen (H2), ethane (C2H6), propane (C3H8), normal butane (n-C4H10), and iso-butane (i-C4H10), were determined using modeling and engine operation tests with spark-ignition gas engines. The results of zero-dimensional detailed chemical kinetic computations indicated that H2 had the longest ignition delay time of these gaseous fuels. Thus, H2 possessed the lowest ignitability. Results of engine operation tests indicated that H2 was the fuel most likely to result in knocking. The use of H2 as the fuel produced a temperature profile of the unburned gas compressed by the piston and flame front that was higher than that of the other fuels due to the high specific heat ratio and burning velocity of H2. The relation between knock resistance and secondary fuel ratio in methane-based fuel blends also was investigated using methane (CH4) as the primary component, and H2, C2H6, C3H8, n-C4H10, or i-C4H10 as the secondary components. When the secondary fuel ratio was small, the CH4/H2 blend possessed the lowest knocking tendency. But as the secondary fuel ratio increased, the CH4/H2 mixture possessed a greater tendency to knock than did CH4/C2H6 due to the high specific heat ratio and burning velocity of H2. These results indicate that the knocking that can occur with gaseous fuels is not only dependent on the ignitability of the fuel, but it also the specific heat ratio and burning velocity.

Download Full-text

Specific heat ratio effects of compressible Rayleigh—Taylor instability studied by discrete Boltzmann method

Frontiers of Physics ◽

10.1007/s11467-021-1096-3 ◽

2021 ◽

Vol 16 (5) ◽

Author(s):

Lu Chen ◽

Huilin Lai ◽

Chuandong Lin ◽

Demei Li

Keyword(s):

Specific Heat ◽

Taylor Instability ◽

Specific Heat Ratio ◽

Rayleigh Taylor Instability ◽

Boltzmann Method

Download Full-text

Analysis of the Impact of Specific Heat Ratio on Two-Dimensional Low Maher Number Nozzle Design

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.590.546 ◽

2014 ◽

Vol 590 ◽

pp. 546-550

Author(s):

Zhi Qiang Fan ◽

Hai Bo Yang ◽

Fei Zhao ◽

Rong Zhu ◽

Dong Bai Sun

Keyword(s):

Specific Heat ◽

Supersonic Nozzle ◽

Two Dimensional ◽

Nozzle Design ◽

Scheme Design ◽

Specific Heat Ratio ◽

Nozzle Contour ◽

Ratio Change ◽

Change Impact ◽

The Impact

The practical requirements of the project the nozzle entrance temperature is high, the gas specific heat ratio varies greatly, so it must consider the specific heat ratio change impact on two-dimensional nozzle contour design. Divided into consideration specific heat ratio change and not consider two kinds of scheme design of 1.4Ma nozzle profile and build the model using the arc line method, numerical simulation is carried out through the CFD software Fluent, analysis of two kinds of design scheme comparison. The results show that, in the supersonic nozzle at low Maher numbers, two schemes of nozzle design profile similarity, parameters change little flow tube, export the Maher number and the flow quality can meet the design requirements, proof of specific heat ratio has little effect on the design results in the design of the nozzle under the condition of low Maher number.

Download Full-text

Modelling and Simulation of Transient Performance of the Semi-Closed O2/CO2 Gas Turbine Cycle for CO2-Capture

Volume 3: Turbo Expo 2003 ◽

10.1115/gt2003-38068 ◽

2003 ◽

Cited By ~ 8

Author(s):

Ragnhild E. Ulfsnes ◽

Olav Bolland ◽

Kristin Jordal

Keyword(s):

Water Vapor ◽

Specific Heat ◽

Gas Turbine ◽

Transient Behavior ◽

Cycle Performance ◽

Working Fluid ◽

Transient Event ◽

Co2 Gas ◽

Specific Heat Ratio ◽

Gas Turbine Cycle

One of the concepts proposed for capture of CO2 in power production from gaseous fossil fuels is the semi-closed O2/CO2 gas turbine cycle. The semi-closed O2/CO2 gas turbine cycle has a near to stoichiometric combustion with oxygen, producing CO2 and water vapor as the combustion products. The water vapor is condensed and removed from the process, the remaining gas, primarily CO2, is mainly recycled to keep turbine inlet temperature at a permissible level. A model for predicting transient behavior of the semi-closed O2/CO2 gas turbine cycle is presented. The model is implemented in the simulation tool gPROMS (Process System Enterprise Ltd.), and simulations are performed to investigate two different issues. The first issue is to see how different cycle performance variables interact during transient behavior; the second is to investigate how cycle calculations are affected when including the gas constant and the specific heat ratio in compressor characteristics. The simulations show that the near to stoichiometric combustion and the working fluid recycle introduce a high interaction between the different cycle components and variables. This makes it very difficult to analytically predict the cycle performance during a transient event, i.e. simulations are necessary. It is also found that, except for the shaft speed calculation, the introduction of gas constant and specific heat ratio dependence on the compressor performance map will have only a minor influence on the process performance.

Download Full-text