CFD Analyses of Combustor-Diffuser System of Marine Gas Turbine Engine

2017 ◽  
Author(s):  
Srinivasan Karuppannan ◽  
Vaibhav Murlidhar Sondur ◽  
Gullapalli Sivaramakrishna ◽  
Raju D. Navindgi ◽  
N. Muthuveerappan
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Reverse Flow ◽  
Flow Behavior ◽  
Gas Turbine Engine ◽  
Pressure Recovery ◽  
Optimum Pressure ◽  
Turbine Engine ◽  
Annular Diffuser ◽  
Duct Geometry

Reverse flow can annular combustor configuration becomes the inevitable option for industrial and marine gas turbine engine, due to its advantages over other configurations. The complexity associated with can annular configuration is optimum design of annular diffuser, as its flow field is dominated by downstream blockage created by transition duct geometry. In the present study, flow behavior in the annular diffuser has been analyzed by simulating realistic downstream combustor liner and transition duct geometry. Flow analysis has been carried out using ANSYS Fluent and turbulence has been modeled using Realizable k-ε model. The diffuser is designed based on G* method, for optimum pressure recovery. Six diffuser configurations have been analyzed by varying the inner wall profile. The effect of parameters on flow field within diffuser and dump region has been studied. Also, the static pressure recovery and total pressure loss coefficient of diffuser is calculated and compared. The results show that the profile of the inner wall and the dump region needs to be tailored to get optimum performance from diffuser.

Finite-Element Analysis of Turbulent Flow in Annular Exhaust Diffusers of Gas Turbine Engines

1991 ◽  
Vol 113 (1) ◽  
pp. 104-110 ◽  
Author(s):  
E. A. Baskharone
Keyword(s):  
Finite Element ◽  
Flow Field ◽  
Turbulent Flow ◽  
Gas Turbine ◽  
Gas Turbine Engine ◽  
Element Formulation ◽  
Predictive Tool ◽  
Integration Algorithm ◽  
Element Discretization ◽  
Turbine Engine

A finite-element model of the turbulent flow field in the annular exhaust diffuser of a gas turbine engine is developed. The analysis is based on a modified version of the Petrov-Galerkin weighted residual method, coupled with a highly accurate biquadratic finite element of the Lagrangian type. The elemental weight functions in the finite-element formulation are so defined to ensure upwinding of the convection terms in the flow-governing equations while reverting to the conventional Galerkin’s definition for all other terms. This approach is equivalent to altering the integration algorithm as the convection terms in the element equations are derived, with the exception that the latter technique is tailored for low-order elements of the linear and bilinear types. Numerical results of the current analysis indicate that spurious pressure modes associated with this type of inertia-dominated flow are alleviated while the false numerical diffusion in the finite-element equations is simultaneously minimized. Turbulence of the flow field is modeled using the two-layer algebraic turbulence closure of Baldwin and Lomax, and the eddy viscosity calculations are performed at variably spaced points which are different from those in the finite-element discretization model. This enhances the accuracy in computing the wall shear stress and the inner/outer layer interface location. The computational model is verified using a set of experimental data at design and off-design operation modes of the exhaust diffuser in a commercial gas turbine engine. Assessment of the results in this case is favorable and, as such, provides evidence of the model capability as an accurate predictive tool in the diffuser detailed design phase.

Jet Perforations for Gas Turbine Applications

2017 ◽  
Author(s):  
Anisha Varughese ◽  
P. Lakshmi ◽  
Srilekha Rajarshi Pasula Valmiki ◽  
Abdur Rasheed ◽  
Vinayak Malhotra
Keyword(s):  
Gas Turbine ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Gas Turbine Engine ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Engineering Systems ◽  
Turbine Engine ◽  
Physical Insight ◽  
Jet Characteristics

Gas turbine engines operate under varying conditions. Subsequently, thrust varies under diverse conditions. Owing to combustion the exhaust runs full. The flow jets have been in utilization for engineering systems, present work investigates the merits of jet perforations for gas turbine engine applications. Controlling thrust when device is running is not an option in the present world. This led us to do the study on the flow of jet through various perforated shapes. At present, thorough experiments are carried out for flow analysis of diverse jet perforations and related flow optimization for better performance. Experiments are carried out on a scaled cascade tunnel. The perforations are of circle, square, triangle and ellipse in shape. The physical insight from this work would be very informative and useful for gas turbine engine operations. Systematic experiments are carried out to fundamentally understand flow behavior with different perforations at the exit. Gas turbine engines have revolutionized the propulsion systems. The very idea of generating large amount of thrust from a small volume has always intrigued scientific community about the effectiveness of operations. Though, the engine works, however, effectiveness have always been questioned and worked upon. Results significantly state that jet perforations do modify the flow jet characteristics. The results show the increase in velocity by 6.2% on using the circular perforation. For the circular perforation wall jet, velocity increases by 14.7% with respect to reference jet i.e. jet without perforation.

Gas-Dynamics Design of Reversible Turbine for Marine Gas Turbine Engine

2017 ◽  
Author(s):  
Xiying Niu ◽  
Feng Lin ◽  
Weishun Li ◽  
Chen Liang ◽  
Shunwang Yu ◽  
...  
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Gas Dynamics ◽  
Gas Turbine Engine ◽  
Operating Conditions ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Turbine Engine ◽  
Power Turbine ◽  
Full Speed

Gas turbine engines are widely used as the marine main power system. However, they can’t reverse like diesel engine. If the reversal is realized, other ways must be adopted, for example, controllable pitch propeller (CPP) and reversible gearing. Although CPP has widespread use, the actuator installation inside the hub of the propeller lead to the decrease in efficiency, and it takes one minute to switch “full speed ahead” to “full speed astern”. In addition, some devices need to be added for the reversible gearing, and it takes five minutes to switch from “full speed ahead” “to “full speed astern”. Based on the gas turbine engine itself, a reversible gas turbine engine is proposed, which can rotate positively or reversely. Most important of all, reversible gas turbine engine can realize operating states of “full speed ahead”, “full speed astern“ and “stop propeller”. And, it just takes half of one minute to switch “full speed ahead” to “full speed astern”. Since reversible gas turbine engines have compensating advantages, and especially in recent years computational fluid dynamics (CFD) technology and turbine gas-dynamics design level develop rapidly, reversible gas turbine engines will be a good direction for ship astern. In this paper, the power turbine of a marine gas turbine engine was redesigned by three dimensional shape modification, and the flow field is analyzed using CFD, in order to redesign into a reverse turbine. The last stage vanes and blades of this power turbine were changed to double-layer structure. That is, the outer one is reversible turbine, while the inner is the ahead one. Note that their rotational directions are opposite. In order to realize switching between rotation ahead and rotation astern, switching devices were designed, which locate in the duct between the low pressure turbine and power turbine. Moreover, In order to reduce the blade windage loss caused by the reversible turbine during working ahead, baffle plates were used before and after the reversible rotor blades. This paper mainly studied how to increase the efficiency of the reversible turbine stage, the torque change under different operating conditions, rotational speed and rotational directions, and flow field under typical operating conditions. A perfect profile is expected to provide for reversible power turbine, and it can decrease the blade windage loss, and increase the efficiency of the whole gas turbine engine. Overall, the efficiency of the newly designed reversible turbine is up to 85.7%, and the output power is more than 10 MW, which can meet requirements of no less than 30% power of rated condition. Most importantly, the shaft is not over torque under all ahead and astern conditions. Detailed results about these are presented and discussed in the paper.

scholarly journals An Air Jet Distortion Generation System

2014 ◽  
Vol 2014 ◽  
pp. 1-17
Author(s):  
M. Sivapragasam ◽  
S. Ramamurthy ◽  
M. D. Deshpande ◽  
P. White
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Total Pressure ◽  
Gas Turbine Engine ◽  
Test Facility ◽  
Generation System ◽  
Turbine Engine ◽  
Air Jet ◽  
Engine Testing ◽  
Distortion Parameters

An air jet distortion generation system is developed to simulate the distorted flow field ahead of gas turbine engines in ground test facility. The flow field of a system of four jets arranged circumferentially and issuing into a confined counterflow was studied experimentally and numerically. The total pressure distortion parameters were evaluated at the Aerodynamic Interface Plane (AIP) for several values of mass flow ratios. Since the total pressure loss distribution at theAIPis characteristically “V” shaped, the number of jets was increased to obtain total pressure distributions as required for gas turbine engine testing. With this understanding, a methodology has been developed to generate a target total pressure distortion pattern at theAIP. Turbulent flow computations are used to iteratively progress towards the target distribution. This methodology was demonstrated for a distortion flow pattern typical of use in gas turbine engine testing using twenty jets, which is a smaller number than reported in the literature. The procedure converges with a root-mean-square error of 3.836% and is able to reproduce the target pattern and other distortion parameters.

scholarly journals Approximately Calculating Optimum Pressure Ratios for Various Gas Turbine Cycles

1976 ◽  
Author(s):  
I. J. Ushiyama ◽  
N. Matsumoto
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Gas Turbine Engine ◽  
Point Of View ◽  
Numerical Calculations ◽  
Optimum Pressure ◽  
Turbine Engine ◽  
Specific Output

In designing the gas turbine engine, it is important to know the rough relationship between the specific output, thermal efficiency, and pressure ratios before setting about calculating the practical cycle. In general, the specific output and the thermal efficiency have their maximum values at certain pressure ratios. The pressure ratios for these maximum values, however, differ in the case of the specific output from the thermal efficiency even in the same type of gas turbine. This paper presents the equations for the optimum pressure ratios of the specific output and thermal efficiency which are obtained for seven types of single-shaft gas turbines. Furthermore, a change in the forms of the curves is made clear by the numerical calculations for the specific output and thermal efficiency near the range of optimum pressure ratios. From the results of this paper, the optimum pressure ratios for every type of single-shaft gas turbine can be easily determined from the thermodynamical point of view.

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