Modeling and Analysis of the Nonlinear Dynamics of a Thermal Pulse Combustor

2006 ◽  
Author(s):  
Subhashis Datta ◽  
Achintya Mukhopadhyay ◽  
Dipankar Sanyal
Keyword(s):  
Nonlinear Dynamics ◽  
Modeling And Analysis ◽  
Thermal Pulse ◽  
Pulse Combustor

An investigation of nonlinear dynamics of a thermal pulse combustor

2009 ◽  
Vol 13 (1) ◽  
pp. 17-38 ◽  
Author(s):  
S. Datta † ◽  
S. Mondal ◽  
A. Mukhopadhyay ◽  
D. Sanyal ◽  
S. Sen
Keyword(s):  
Nonlinear Dynamics ◽  
Thermal Pulse ◽  
Pulse Combustor

scholarly journals Modeling and Analysis of a Generic Internal Cargo Airdrop System for a Tandem Helicopter

2021 ◽  
Vol 11 (11) ◽  
pp. 5109
Author(s):  
Guozhi Li ◽  
Yihua Cao ◽  
Maosheng Wang
Keyword(s):  
Nonlinear Dynamics ◽  
Flight Dynamics ◽  
Simulation Method ◽  
Rotational Dynamics ◽  
Discretization Method ◽  
Modeling And Analysis ◽  
Flight Velocity ◽  
Vector Mechanics ◽  
Good Attitude

This article describes the results of modeling and analysis of a generic internal cargo system using a discretization method of the vector mechanics. The model can be easily incorporated into a tandem helicopter model and is intended for use of simulation and investigating the problems of flight dynamics, control, etc., both in flight operation loading a cargo and flight operation in the process of airdrops. The model is derived by considering the main descriptions of the cargo, including the linear and rotational dynamics, the kinematics, and the forces and moments acting on the helicopter. A simulation method embedded with a numerical trim algorithm is developed for the complete coupling helicopter/cargo nonlinear dynamics system. The simulation application of the model is illustrated, including the case of flight operation loading a cargo by considering three mass configurations of 3000, 4500, and 6000 kg, and the case of flight operation in the process of airdrops at velocities of 0, 40, 80, 120, and 160 knots. Stabilities of the helicopter in the process of airdrops are also analyzed. The major conclusions drawn are: (i) the tandem helicopter has a good attitude maintaining ability in the whole flight velocity envelope when it conducts a flight operation loading a cargo; (ii) in the process of airdrops, the increase in flight velocity will constantly decrease the helicopter pitching attitude and increases the total airdrop time and decreases the backward moving velocity of the cargo, and helicopter flying at a velocity between 80 and 120 knots might be acceptable; (iii) the stabilities of both the longitudinal and lateral periodic modes are continuing to decrease during the backward movement of the cargo.

Effects of Tailpipe Friction on the Nonlinear Dynamics of a Thermal Pulse Combustor

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Achintya Mukhopadhyay ◽  
Subhashis Datta ◽  
Dipankar Sanyal
Keyword(s):  
Time Series ◽  
Friction Factor ◽  
Time Series Data ◽  
Threshold Value ◽  
Series Data ◽  
Combustion Dynamics ◽  
Thermal Pulse ◽  
Pulse Combustor ◽  
Steady Combustion ◽  
Peak Pressures

The effect of tailpipe friction on the combustion dynamics inside a thermal pulse combustor has been investigated using a nonlinear model consisting of four coupled first order ordinary differential equations. The dynamics of the system is represented through time series plots, time-delay phase plots, and Poincaré maps. The results indicate that as the tailpipe friction factor is lowered, the system undergoes a transition from steady combustion through oscillating combustion to an intermittent combustion with chaotic characteristics before extinction. The time series data are shown to be useful indicator for early detection of extinction. In one approach (thresholding), the occurrence of local peak pressures below a predefined threshold value is identified as an event and the number of events (event count) and largest number of successive cycles with such events (event duration) are recorded as the friction factor is lowered. In another approach, the statistical moments (kurtosis) of the data are used. Number of kurtosis peaks above a prescribed value and variance of the kurtosis values are recorded for decreasing values of friction factor. All these numbers sharply increase as the system approaches extinction.

Use of Temporal Irreversibility of Symbolic Time Series for Early Detection of Extinction in Thermal Pulse Combustors

2006 ◽  
Author(s):  
Subhashis Datta ◽  
Achintya Mukhopadhyay ◽  
Dipankar Sanyal
Keyword(s):  
Time Series ◽  
Fourth Order ◽  
Time Series Data ◽  
Order System ◽  
Series Data ◽  
Thermal Pulse ◽  
Pulse Combustor ◽  
The Difference ◽  
Symbol Sequences ◽  
System Approaches

A nonlinear fourth-order dynamic model of a thermal pulse combustor has been developed. In this work, the time series data generated by solution of the fourth order system is converted into a set of symbols based on the values of pressure variables. The key step to symbolization involves transformation of the original values to a stream of discretised symbols by partitioning the range of observed values into a finite number of regions and then assigning a symbol to each measurement based on the region in which it falls. Once all the measured values are symbolized, a symbol sequence vector consisting of L successive temporal observations is defined and its relative frequency is determined. In this work, the relative frequencies of different symbol sequences are computed by scanning the time series data in forward and reverse directions. The difference between the relative frequencies obtained in forward and reverse scanning is termed as "irreversibility" of the process. It is observed that for given alphabet and word sizes, the "irreversibility" increases as the system approaches extinction. The effects of different choices of alphabet and word sizes are also considered.

Effects of inlet conditions on dynamics of a thermal pulse combustor

2012 ◽  
Vol 16 (1) ◽  
pp. 59-74 ◽  
Author(s):  
Sirshendu Mondal ◽  
Achintya Mukhopadhyay ◽  
Swarnendu Sen
Keyword(s):  
Thermal Pulse ◽  
Pulse Combustor ◽  
Inlet Conditions

Dynamic Characterization of a Laboratory-Scale Thermal Pulse Combustor

2012 ◽  
Author(s):  
Sirshendu Mondal ◽  
Achintya Mukhopadhyay ◽  
Swarnendu Sen
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Singular Spectrum Analysis ◽  
Laboratory Scale ◽  
Series Data ◽  
Air Flow Rate ◽  
Fuel Flow Rate ◽  
Thermal Pulse ◽  
Fuel Flow ◽  
Pulse Combustor

Pulse combustors are widely applied for heating, drying and even propulsion applications because of their higher efficiency, higher heat transfer rates and lower emission than steady combustors. However, fundamentals of this pulse combustor remain till date largely unexplored. Experiments are conducted on a laboratory-scale thermal pulse combustor. The set-up consists of an upstream section, the combustor and the tailpipe. The optical signal from the flame is measured with a photomultiplier tube and pressure fluctuations are measured using a dynamic pressure transducer. The time series data reconstructed with SSA (Singular Spectrum Analysis) reveals that at a given air flow rate as the fuel flow rate is reduced, three distinct regimes are observed: strongly pulsating, weakly pulsating and non-pulsating. Nonlinear analysis suggests the existence of quasiperiodic orbits for the pulsating cases. The phase difference between pressure and heat release rate fluctuations confirm sustained instability for the pulsating cases. The characteristic frequency is found to decrease with decrease in fuel flow rate and increase in tailpipe length for a given air flow rate. Different orientation of fuel inlet has been implemented to achieve pulsating combustion under lean fuel conditions.

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