scholarly journals Improvement of Combustion Process of Spark-Ignited Aviation Wankel Engine

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2292 ◽  
Author(s):  
Lev Finkelberg ◽  
Alexander Kostuchenkov ◽  
Andrei Zelentsov ◽  
Vladimir Minin
Keyword(s):  
Cross Sections ◽  
High Performance ◽  
Laminar Flame ◽  
Combustion Process ◽  
Working Fluid ◽  
Piston Engine ◽  
Computational Region ◽  
Rotor Design ◽  
Wankel Engine ◽  
The Mathematical Model

This paper deals with the creation of modern high-performance aircraft power units based on the Wankel rotary piston engine. One of the main problems of Wankel engines is high specific fuel consumption. This paper solves the problem of improving the efficiency of this type of engine. The mathematical model of non-stationary processes of transfer of momentum, energy, mass, and the concentration of reacting substances in the estimated volume provides for the determination of local gas parameters in the entire computational region, which are presented as a sum of averaged and pulsation components. The k-ζ-f model is used as the turbulence model; the combustion is described by the coherent flame model (CFM) based on the concept of laminar flame propagation. As a result of the calculation, we obtained the values of temperature, pressure, and velocity of the working fluid in the working chamber cross-sections of a rotary–piston engine. Various options of the rotor recess shape are considered. Based on the data obtained, the rotor design was improved. The offered shape of the rotor recess has reduced emissions of both nitrogen oxides and carbon dioxide.

Syngas Laminar Flame Speed Computation and its Application to Gaseous Fueled Spark Ignited Engines Performance Prediction

2016 ◽  
Author(s):  
Hui Xu ◽  
Leon A. LaPointe ◽  
Robin J. Bremmer
Keyword(s):  
Natural Gas ◽  
Chemical Kinetics ◽  
Laminar Flame ◽  
Combustion Process ◽  
Engine Performance ◽  
Ambient Conditions ◽  
Piston Engine ◽  
Natural Gas Engines ◽  
Gaseous Fuels ◽  
Engine Combustion

Gaseous fueled spark ignited (SI) engines are often developed using pipeline quality natural gas as the fuel. However, natural gas engines are occasionally expected by customers to accommodate different fuel compositions when deployed in the field. Depending on the source or production processing of the fuel and the ambient conditions, gaseous fuels can have different levels of heavy hydrocarbons and/or significant levels of diluents when compared to natural gas. In recent years, there are increasing interests in using synthesis gas (syngas) from renewable sources in gaseous fueled spark ignition engines. This work investigated syngas compositions from different production processes and describes a methodology to predict engine performance using syngas. Syngas composition variations can provide different laminar flame speeds (LFS), which can result in changes in combustion burn rate, heat release rate and knock likelihood, if the engine combustion process is not optimized appropriately. It is challenging to obtain LFS data at the high pressure and temperature conditions that are characteristic of the piston engine combustion process. It has proven to be effective to employ a chemical kinetics solver using an appropriate chemical kinetics mechanism to obtain LFS values under piston engine combustion conditions. Alternative chemical kinetics mechanisms were investigated to identify one which best characterized combustion performance relative to detailed rig and engine measurements. With this appropriate chemical kinetics mechanism, LFS results are now used to guide natural gas engine combustion tuning when using syngas as a fuel. Engine performance is predicted in terms of NOx emissions and knock likelihood using the in-house developed methodology.

scholarly journals Coal-Fired Magnetohydrodynamic Power Plant With Zero-CO2 Atmospheric Emission

1997 ◽  
Author(s):  
E. Iantovski ◽  
R. Lhomme ◽  
Ph. Mathieu
Keyword(s):  
Power Plant ◽  
High Performance ◽  
Combustion Process ◽  
The Other ◽  
Working Fluid ◽  
Atmospheric Emission ◽  
Mhd Generator ◽  
Energy Consuming ◽  
The One ◽  
Cycle Efficiency

In this system, an MHD generator is used instead of a gas turbine. The cycle efficiency is reaching 50%. The system is based on a cycle using CO2 as the working fluid and oxygen as oxidant. The fuel is pulverized coal. All the pollutants, including the CO2 produced in the combustion process, are fully removed and diposed of. This highly pressurized excess CO2 is easily separated from the working fluid without any costly and energy consuming device and, being in liquid state, is ready for transportation and disposal or possibly reuse in other applications. The most important parameter determining the cycle efficiency is shown to be the isentropic effectiveness of the MHD expander. This latter is depending, on the one hand, on the design of the channel and on the other hand, on the conductivity of the gases which can be optimized with respect to the cycle parameters. In conclusion, the assets of the proposed system are high performance and no pollutant releases. As a consequence, MHD generators may be considered as viable options for coal-firing and possible competitors of advanced coal-based plants. One of the spin-off of this study is the possible revival of existing MHD facilities.

scholarly journals Research on the Operating Characteristics of Hydraulic Free-Piston Engines: A Systematic Review and Meta-Analysis

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3530
Author(s):  
Fukang Ma ◽  
Shuanlu Zhang ◽  
Zhenfeng Zhao ◽  
Yifang Wang
Keyword(s):  
Systematic Review ◽  
High Efficiency ◽  
Meta Analysis ◽  
Combustion Process ◽  
Research Progress ◽  
Future Research ◽  
Operating Characteristics ◽  
Piston Engine ◽  
Free Piston ◽  
Free Piston Engine

The hydraulic free-piston engine (HFPE) is a kind of hybrid-powered machine which combines the reciprocating piston-type internal combustion engine and the plunger pump as a whole. In recent years, the HFPE has been investigated by a number of research groups worldwide due to its potential advantages of high efficiency, energy savings, reduced emissions and multi-fuel operation. Therefore, our study aimed to assess the operating characteristics, core questions and research progress of HFPEs via a systematic review and meta-analysis. We included operational control, starting characteristics, misfire characteristics, in-cylinder working processes and operating stability. We conducted the literature search using electronic databases. The research on HFPEs has mainly concentrated on four kinds of free-piston engine, according to piston arrangement form: single piston, dual pistons, opposed pistons and four-cylinder complex configuration. HFPE research in China is mainly conducted in Zhejiang University, Tianjin University, Jilin University and the Beijing Institute of Technology. In addition, in China, research has mainly focused on the in-cylinder combustion process while a piston is free by considering in-cylinder combustion machinery and piston dynamics. Regarding future research, it is very important that we solve the instabilities brought about by chance fluctuations in the combustion process, which will involve the hydraulic system’s efficiency, the cyclical variation, the method of predicting instability and the recovery after instability.

Influence of Tooth Errors and Truing Principles of Grinding Wheel Abrasion for Machining Arc Enveloping Worm

2013 ◽  
Vol 652-654 ◽  
pp. 2153-2158
Author(s):  
Wu Ji Jiang ◽  
Jing Wei
Keyword(s):  
Mathematical Model ◽  
Case Studies ◽  
High Precision ◽  
High Performance ◽  
New Method ◽  
Grinding Wheel ◽  
Grinding Process ◽  
The Mathematical Model

Controlling the tooth errors induced by the variation of diameter of grinding wheel is the key problem in the process of ZC1 worm grinding. In this paper, the influence of tooth errors by d1, m and z1 as the grinding wheel diameter changes are analyzed based on the mathematical model of the grinding process. A new mathematical model and truing principle for the grinding wheel of ZC1 worm is presented. The shape grinding wheel truing of ZC1 worm is carried out according to the model. The validity and feasibility of the mathematical model is proved by case studies. The mathematical model presented in this paper provides a new method for reducing the tooth errors of ZC1 worm and it can meet the high-performance and high-precision requirements of ZC1 worm grinding.

Communication Principle of Literature Database Based on Spatial and Temporal Segmentation Technology

2014 ◽  
Vol 543-547 ◽  
pp. 2418-2421
Author(s):  
Yong Wang
Keyword(s):  
High Performance ◽  
Database System ◽  
Lake Area ◽  
Temporal Segmentation ◽  
New Town ◽  
Database Construction ◽  
Poyang Lake Area ◽  
The Mathematical Model ◽  
And Storage ◽  
Computer Resources

In this paper we introduce cross tree and block mathematical principles into the design of database system, divide the time sequence and storage space of computer database system, establish the mathematical model and algorithm of computer resources database system, and design the test database system. In this paper, we use high performance interface of Display Port, by way of coupling to communicate on two port control, and use RHEL 6.2 Linux virtual machine to do simulation experiment on process of database system. Through the simulation we find the API which is called by Read, Close, Mmap, Stat, Fstat is similar. It is consistent with the actual situation, and verifies the reliability of the program. Finally, we apply the database system to the network database construction of sports literature resources in the new town of Poyang Lake area. It reaches the effect that sport resources are shared by all. It provides technical support for the application of computer database system.

Influence of Imperfections in the Working Media on Diesel Engine Indicator Process: Part 2 — Results

1998 ◽  
Author(s):  
Stanislav N. Danov ◽  
Ashwani K. Gupta
Keyword(s):  
Mathematical Model ◽  
Diesel Engine ◽  
High Pressures ◽  
Combustion Process ◽  
Ideal Gas ◽  
Working Medium ◽  
High Pressures And Temperatures ◽  
Specific Heat Capacities ◽  
Working Media ◽  
The Mathematical Model

Abstract In the companion Part 1 of this two-part series paper several improvements to the mathematical model of the energy conversion processes, taking place in a diesel engine cylinder, have been proposed. Analytical mathematical dependencies between thermal parameters (pressure, temperature, volume) and caloric parameters (internal energy, enthalpy, specific heat capacities) have been obtained. These equations have been used to provide an improved mathematical model of diesel engine indicator process. The model is based on the first law of thermodynamics, by taking into account imperfections in the working media which appear when working under high pressures and temperatures. The numerical solution of the simultaneous differential equations is obtained by Runge-Kutta type method. The results show that there are significant differences between the values calculated by equations for ideal gas and real gas under conditions of high pressures and temperatures. These equations are then used to solve the desired practical problem in two different two-stroke turbo-charged engines (8DKRN 74/160 and Sulzer-RLB66). The numerical experiments show that if the pressure is above 8 to 9 MPa, the working medium imperfections must be taken into consideration. The mathematical model presented here can also be used to model combustion process of other thermal engines, such as advanced gas turbine engines and rockets.

The High Performance Toroidal Engine Concept (HiPerTEC)

2011 ◽  
Author(s):  
Karl V. Hoose ◽  
Eric E. Shorey
Keyword(s):  
High Performance ◽  
Combustion Process ◽  
Thermodynamic Cycle ◽  
Unmanned Vehicles ◽  
Advanced Materials ◽  
Specific Power ◽  
Operating Characteristics ◽  
Free Piston ◽  
Engine Design ◽  
Swept Volume

The traditional reciprocating I.C. engine has evolved to a point where significant improvements in thermal efficiency and specific power are not expected. Modifications to existing engines may prove to be difficult and expensive while resulting in only marginal gains. In addition, most modifications result in added components that often increase cost and decrease reliability of the system as a whole. For applications requiring major advances in performance, such as unmanned vehicles, meeting mission requirements will likely stem from a revolutionary rather than an evolutionary engine design. The slider crank mechanism is a major impediment to the traditional reciprocating I.C. engine. Although this mechanism has been used for the past 100 years, it is very wasteful of the available energy supplied by the combustion process, where piston-liner interactions from this arrangement accounts for 50–70% of the total friction losses in this engine design. Eliminating the slider crank could significantly reduce friction losses and provide additional benefits that can increase fuel conversion efficiency. The HiPerTEC engine is an opposed, free-piston engine arranged in a toroidal configuration with two counter reciprocating sets of pistons. The counter reciprocating masses eliminate the vibration found in linear free-piston engines. The HiPerTEC employs a unique shared volume configuration where the swept volume is twice the physical cylinder volume. This attribute offers a significant increase in specific power, while the free-piston characteristics provide for substantial gains in thermodynamic cycle efficiency. An eight cylinder/chamber arrangement offers balanced operation in both two and four-stroke cycle modes to allow for a wide operating envelope. The final HiPerTEC configuration will require advanced materials to address lubrication and cooling requirements. This paper discusses the HiPerTEC design, operating characteristics, development progress to date, and the challenges that lie ahead.

CO and H2O Time-Histories in Shock-Heated Blends of Methane and Ethane for Assessment of a Chemical Kinetics Model

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
O. Mathieu ◽  
C. R. Mulvihill ◽  
E. L. Petersen ◽  
Y. Zhang ◽  
H. J. Curran
Keyword(s):  
Chemical Kinetics ◽  
Laminar Flame ◽  
Combustion Process ◽  
Time History ◽  
Good Marker ◽  
Ignition Delay Times ◽  
Depletion Rate ◽  
Time Histories ◽  
Main Components ◽  
Detailed Kinetics

Methane and ethane are the two main components of natural gas and typically constitute more than 95% of it. In this study, a mixture of 90% CH4/10% C2H6 diluted in 99% Ar was studied at fuel lean (equiv. ratio = 0.5) conditions, for pressures around 1, 4, and 10 atm. Using laser absorption diagnostics, the time histories of CO and H2O were recorded between 1400 and 1800 K. Water is a final product from combustion, and its formation is a good marker of the completion of the combustion process. Carbon monoxide is an intermediate combustion species, a good marker of incomplete/inefficient combustion, as well as a regulated pollutant for the gas turbine industry. Measurements such as these species time histories are important for validating and assessing chemical kinetics models beyond just ignition delay times and laminar flame speeds. Time-history profiles for these two molecules were compared to a state-of-the-art detailed kinetics mechanism as well as to the well-established GRI 3.0 mechanism. Results show that the H2O profile is accurately reproduced by both models. However, discrepancies are observed for the CO profiles. Under the conditions of this study, the CO profiles typically increase rapidly after an induction time, reach a maximum, and then decrease. This maximum CO mole fraction is often largely over-predicted by the models, whereas the depletion rate of CO past this peak is often over-estimated for pressures above 1 atm.

CO and H2O Time-Histories in Shock-Heated Blends of Methane and Ethane for Assessment of a Chemical Kinetics Model

2017 ◽  
Author(s):  
O. Mathieu ◽  
C. Mulvihill ◽  
E. L. Petersen ◽  
Y. Zhang ◽  
H. J. Curran
Keyword(s):  
Gas Turbine ◽  
Chemical Kinetics ◽  
Laminar Flame ◽  
Combustion Process ◽  
Practical Interest ◽  
Time History ◽  
Good Marker ◽  
Ignition Delay Times ◽  
Time Histories ◽  
Detailed Kinetics

Methane and ethane are the two main components of natural gas and typically constitute more than 95% of it. In this study, a mixture of 90% CH4 /10% C2H6 diluted in 99% Ar was studied at fuel lean (ϕ = 0.5) conditions, for pressures around 1, 4, and 10 atm. Using laser absorption diagnostics, the time histories of CO and H2O were recorded between 1400 and 1800 K. Water is a final product from hydrocarbon combustion, and following its formation is a good marker of the completion of the combustion process. Carbon monoxide is an intermediate combustion species, a good marker of incomplete/inefficient combustion, as well as a regulated pollutant for the gas turbine industry. Measurements such as these species time histories are important for validating and assessing chemical kinetics models beyond just ignition delay times and laminar flame speeds. Time-history profiles for these two molecules measured herein were compared to a modern, state-of-the-art detailed kinetics mechanism as well as to the well-established GRI 3.0 mechanism. Results show that the H2O profile is accurately reproduced by both models. However, discrepancies are observed for the CO profiles. Under the conditions of this study, the measured CO profiles typically increase rapidly after an induction time, reach a maximum and then decrease. This maximum CO mole fraction is often largely over-predicted by the models, whereas the depletion rate of CO past this peak is often over-estimated by the models for pressures above 1 atm. This study demonstrates the need to improve on the accuracy of the HCCO reactions involved in CO formation for pressures of practical interest for the gas turbine industry.

Analysis of Incylinder Pressure and Temperature Variation in a Four-Stroke S. I. Engine Using Wiebe’s Combustion Model

2014 ◽  
Vol 984-985 ◽  
pp. 957-961
Author(s):  
Vijayashree ◽  
P. Tamil Porai ◽  
N.V. Mahalakshmi ◽  
V. Ganesan
Keyword(s):  
Heat Release ◽  
Combustion Process ◽  
Pressure Variation ◽  
Spark Ignition Engine ◽  
Working Fluid ◽  
Combustion Model ◽  
Cylinder Pressure ◽  
Crank Angle ◽  
Experimental Values ◽  
Release Model

This paper presents the modeling of in-cylinder pressure variation of a four-stroke single cylinder spark ignition engine. It uses instantaneous properties of working fluid, viz., gasoline to calculate heat release rates, needed to quantify combustion development. Cylinder pressure variation with respect to either volume or crank angle gives valuable information about the combustion process. The analysis of the pressure – volume or pressure-theta data of a engine cycle is a classical tool for engine studies. This paper aims at demonstrating the modeling of pressure variation as a function of crank angle as well as volume with the help of MATLAB program developed for this purpose. Towards this end, Woschni heat release model is used for the combustion process. The important parameter, viz., peak pressure for different compression ratios are used in the analysis. Predicted results are compared with experimental values obtained for a typical compression ratio of 8.3.

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