Performance of a Turboshaft Engine for Helicopter Applications Operating at Variable Shaft Speed

2012 ◽  
Author(s):  
Gianluigi Alberto Misté ◽  
Ernesto Benini
Keyword(s):  
Steady State ◽  
Engine Performance ◽  
Engine Fuel ◽  
Main Rotor ◽  
Steady State Condition ◽  
Power Turbine ◽  
Steady State Model ◽  
Optimization Routine ◽  
Turboshaft Engine ◽  
The Impact

An off-design steady state model of a generic turboshaft engine has been implemented to assess the influence of variable free power turbine (FPT) rotational speed on overall engine performance, with particular emphasis on helicopter applications. To this purpose, three off-design flight conditions were simulated and engine performance obtained with different FTP rotational speeds were compared. In this way, the impact on engine performance of a particular speed requested from the main helicopter rotor could be evaluated. Furthermore, an optimization routine was developed to find the optimal FPT speed which minimizes the engine specific fuel consumption (SFC) for each off-design steady state condition. The usual running line obtained with constant design FPT speed is compared with the optimized one. The results of the simulations are presented and discussed in detail. As a final simulation, the main rotor speed Ω required to minimize the engine fuel mass flow was estimated taking into account the different requirements of the main rotor and the turboshaft engine.

Life Prediction of Power Turbine Components for High Exhaust Back Pressure Applications: Part I — Disks

2015 ◽  
Author(s):  
Dipankar Dua ◽  
Brahmaji Vasantharao
Keyword(s):  
Steady State ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Life Prediction ◽  
Creep Damage ◽  
Back Pressure ◽  
System Level ◽  
Cyclic Life ◽  
Power Turbine ◽  
The Impact

Industrial and aeroderivative gas turbines when used in CHP and CCPP applications typically experience an increased exhaust back pressure due to pressure losses from the downstream balance-of-plant systems. This increased back pressure on the power turbine results not only in decreased thermodynamic performance but also changes power turbine secondary flow characteristics thus impacting lives of rotating and stationary components of the power turbine. This Paper discusses the Impact to Fatigue and Creep life of free power turbine disks subjected to high back pressure applications using Siemens Energy approach. Steady State and Transient stress fields have been calculated using finite element method. New Lifing Correlation [1] Criteria has been used to estimate Predicted Safe Cyclic Life (PSCL) of the disks. Walker Strain Initiation model [1] is utilized to predict cycles to crack initiation and a fracture mechanics based approach is used to estimate propagation life. Hyperbolic Tangent Model [2] has been used to estimate creep damage of the disks. Steady state and transient temperature fields in the disks are highly dependent on the secondary air flows and cavity dynamics thus directly impacting the Predicted Safe Cyclic Life and Overall Creep Damage. A System-level power turbine secondary flow analyses was carried out with and without high back pressure. In addition, numerical simulations were performed to understand the cavity flow dynamics. These results have been used to perform a sensitivity study on disk temperature distribution and understand the impact of various back pressure levels on turbine disk lives. The Steady Sate and Transient Thermal predictions were validated using full-scale engine test and have been found to correlate well with the test results. The Life Prediction Study shows that the impact on PSCL and Overall Creep damage for high back pressure applications meets the product design standards.

scholarly journals The Effect of Compressor Rotor Tip Crops on Turboshaft Engine Performance

1992 ◽  
Author(s):  
Peter C. Frith
Keyword(s):  
Experimental Study ◽  
Engine Performance ◽  
Tip Clearance ◽  
Stability Margins ◽  
Compressor Rotor ◽  
Power Turbine ◽  
Normal Production ◽  
Turboshaft Engine ◽  
Engine Condition ◽  
Steady State Performance

The results from an experimental study into the effect of compressor rotor tip clearance changes on the steady-state performance and stability margins of a free-power turbine turboshaft engine are presented and discussed. This work was directed at the development of methods to diagnose engine condition from gas path measurements. It was found that the normal production suite of engine instrumentation was able to measure the deterioration in engine performance due to the implanted compressor degradation and the resultant deviations in the measured parameters from their respective nominal baselines do provide useful indicators of engine condition.

The Effects of Intake Plenum Volume on the Performance of a Small Naturally Aspirated Restricted Engine

2009 ◽  
Author(s):  
Leonard J. Hamilton ◽  
Jim S. Cowart ◽  
Jasen E. Lee ◽  
Ryan E. Amorosso
Keyword(s):  
Steady State ◽  
Performance Metrics ◽  
Full Range ◽  
Engine Performance ◽  
Absolute Pressure ◽  
Cylinder Pressure ◽  
Formula Sae ◽  
Indicated Mean Effective Pressure ◽  
Competition Rules ◽  
The Impact

Intake tuning is a widely recognized method for optimizing the performance of a naturally aspirated engine for motorsports applications. Wave resonance and Helmholtz theories are useful for predicting the impact of intake runner length on engine performance. However, there is very little information in the literature regarding the effects of intake plenum volume. The goal of this study was to determine the effects of intake plenum volume on steady state and transient engine performance for a restricted naturally aspirated engine for Formula SAE (FSAE) vehicle use. Testing was conducted on a four cylinder 600 cc motorcycle engine fitted with a 20 mm restrictor in compliance with FSAE competition rules. Plenum sizes were varied from 2 to 10 times engine displacement (1.2 to 6.0 L) and engine speeds were varied from 3,000 to 12,500 RPM. Performance metrics including volumetric efficiency, torque and power were recorded at steady state conditions. Experimental results showed that engine performance increased modestly as plenum volume was increased from 2 to 8 times engine displacement (4.8L). Increasing plenum volume beyond 4.8L resulted in significant improvement in performance parameters. Overall, peak power was shown to increase from 54 kW to 63 kW over the range of plenums tested. Additionally, transient engine performance was evaluated using extremely fast (60 msec) throttle opening times for the full range of plenum sizes tested. In-cylinder pressure was used to calculate cycle-resolved gross indicated mean effective pressure (IMEPg) development during these transients. Interestingly, the cases with the largest plenum sizes only took 1 – 2 extra cycles (30–60 msec) to achieve maximum IMEPg levels when compared to the smaller volumes. In fact the differences were so minor that it would be doubtful that a driver would notice the lag. Additional metrics included time for the plenums to fill and an analysis of manifold absolute pressure (MAP) and peak in-cylinder pressure development during and after the throttle transient. Plenums below 4.8L completely filled even before the transient was completed.

The Predicted and Measured Effects of Increasing Back Pressure on the Performance of a Turboshaft Engine

2010 ◽  
Author(s):  
Marco S. Attia ◽  
Richard W. Eustace ◽  
Shane C. Favaloro
Keyword(s):  
Power Output ◽  
Engine Performance ◽  
Sensitivity Study ◽  
Test Facility ◽  
Inlet Temperature ◽  
Static Test ◽  
Tail Pipe ◽  
Fuel Flow ◽  
Power Turbine ◽  
Turboshaft Engine

This paper presents a comparison between the predicted effect of an increase in backpressure on a turboshaft helicopter engine and the actual results measured in an experimental test program. A generic engine performance program was used to perform a sensitivity study to identify the effect of increases in power turbine exit pressure (backpressure) on other engine performance parameters. The analysis showed that as the backpressure increases the engine increases fuel flow to produce a constant shaft torque (or horsepower), until the maximum power turbine entry temperature is reached. Once this occurs, fuel flow can no longer increase and thus further increases in backpressure cause a decrease in output torque. These predicted results are then compared with the actual effect as measured on a T55-GA-714A engine in a static test facility. The tests involved replacing the standard engine tail pipe with one of three shorter stub ducts which increased the backpressure by employing straight and convergent flow passages instead of the divergent passage on the standard tail pipe. The test-cell data identified that the stub ducts increase specific fuel consumption by between 0.016 and 0.039 lb/hr/hp, while the turbine inlet temperature increased by up to 108 deg F. This temperature increase means that the power output will become turbine temperature limited at a lower ambient temperature than would otherwise occur. Results showed that when temperature limiting exists the power output will be reduced by between 115 and 400 SHP depending on the choice of stub duct.

A New Sensor Diagnostic Technique Applied to a Micro Gas Turbine Rig

2012 ◽  
Author(s):  
Andrea Tipa ◽  
Alessandro Sorce ◽  
Matteo Pascenti ◽  
Alberto Traverso
Keyword(s):  
Steady State ◽  
Statistical Model ◽  
Gas Turbine ◽  
Measurement Errors ◽  
Combined Cycle ◽  
Model Approximation ◽  
Operating Life ◽  
Steady State Condition ◽  
Micro Gas Turbine ◽  
The Impact

This paper describes the development and testing of a new algorithm to identify faulty sensors, based on a statistical model using quantitative statistical process history. Two different mathematical models were used and the results were analyzed to highlight the impact of model approximation and random error. Furthermore, a case study was developed based on a real micro gas turbine facility, located at the University of Genoa. The diagnostic sensor algorithm aims at early detection of measurement errors such as drift, bias, and accuracy degradation (increase of noise). The process description is assured by a database containing the measurements selected under steady state condition and without faults during the operating life of the plant. Using an invertible statistical model and a combinatorial approach, the algorithm is able to identify sensor fault. This algorithm could be applied to plants in which historical data are available and quasi steady state conditions are common (e.g. Nuclear, Coal Fired, Combined Cycle).

STEADY STATE AND DYNAMIC MODELING OF AN INDIRECT DISTRICT HEATING SYSTEM

2010 ◽  
Vol 18 (01) ◽  
pp. 61-75 ◽  
Author(s):  
L. LI ◽  
M. ZAHEERUDDIN ◽  
SUNG-HWAN CHO ◽  
SANG-HOON JUNG
Keyword(s):  
Steady State ◽  
Dynamic Model ◽  
District Heating ◽  
Heating System ◽  
Dynamic Responses ◽  
District Heating System ◽  
Steady State Model ◽  
Heated Floor ◽  
The Impact ◽  
Important System

An indirect district heating system (IDHS) with heated floor area of 851 031 m2 and ten heat exchange stations was modeled in this study. An aggregated steady state model for the system was developed to study the impact of important system parameters. A dynamic model of the IDHS was developed based on energy balance principles. The dynamic model consists of sub-system models such as boiler, pipe network, heat exchanger, terminal heater and zone models. Simulation results of the dynamic responses show that the overall efficiency of the IDHS system is 78.7%, and the two highest heat loss components are the boiler heat losses and the secondary water makeup loss.

An Investigation in Improving the Exhaust Management Process on Miller Cycle and Turbocompounding

2012 ◽  
Author(s):  
Thomas M. Lavertu ◽  
Roy J. Primus ◽  
Omowoleola C. Akinyemi
Keyword(s):  
Waste Heat ◽  
Process Variations ◽  
Exhaust Valve ◽  
Engine Fuel ◽  
Miller Cycle ◽  
Expansion Process ◽  
Combustion Gases ◽  
Power Turbine ◽  
Valve Opening ◽  
The Impact

A reduction in diesel engine fuel consumption at a constant emissions level can be achieved by various means. A power turbine as a means of waste heat recovery (i.e., turbocompounding) and altered intake valve closure timing (Miller cycle) are two such mechanisms. Each of these technologies act as a means of improving the expansion process of the combustion gases, requiring reduced fueling for the same work extraction. When these embodiments are typically implemented, the timing of the exhaust valve opening is maintained. However, optimization of the timing of the exhaust valve opening presents the potential for further improvement in the expansion process. Variations in the exhaust valve opening timing will be investigated for Miller and turbocompounding cycles as well as the combination of the two features. Results will be shown to quantify the impact these variations have in system efficiency. Second law analysis will be used to show how these variations in engine configurations impact individual loss mechanisms. Finally, comparisons will be made to show the relative differences between Miller cycle and turbocompounding with and without optimization of the exhaust valve timing.

scholarly journals Gaussian Process Model-Based Performance Uncertainty Quantification of a Typical Turboshaft Engine

2021 ◽  
Vol 11 (18) ◽  
pp. 8333
Author(s):  
Xuejun Liu ◽  
Hailong Tang ◽  
Xin Zhang ◽  
Min Chen
Keyword(s):  
Gaussian Process ◽  
Uncertainty Quantification ◽  
Process Model ◽  
Engine Performance ◽  
Latin Hypercube Sampling ◽  
Sampling Errors ◽  
Gaussian Process Model ◽  
Turboshaft Engine ◽  
The Impact ◽  
Performance Uncertainty

The gas turbine engine is a widely used thermodynamic system for aircraft. The demand for quantifying the uncertainty of engine performance is increasing due to the expectation of reliable engine performance design. In this paper, a fast, accurate, and robust uncertainty quantification method is proposed to investigate the impact of component performance uncertainty on the performance of a classical turboshaft engine. The Gaussian process model is firstly utilized to accurately approximate the relationships between inputs and outputs of the engine performance simulation model. Latin hypercube sampling is subsequently employed to perform uncertainty analysis of the engine performance. The accuracy, robustness, and convergence rate of the proposed method are validated by comparing with the Monte Carlo sampling method. Two main scenarios are investigated, where uncertain parameters are considered to be mutually independent and partially correlated, respectively. Finally, the variance-based sensitivity analysis is used to determine the main contributors to the engine performance uncertainty. Both approximation and sampling errors are explained in the uncertainty quantification to give more accurate results. The final results yield new insights about the engine performance uncertainty and the important component performance parameters.

Impact of Compressor Surge on Performance and Emissions of a Marine Diesel Engine

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Nikolaos-Alexandros Vrettakos
Keyword(s):  
Steady State ◽  
Diesel Engine ◽  
Engine Performance ◽  
Marine Diesel Engine ◽  
Performance Parameters ◽  
Test Bed ◽  
Engine Operation ◽  
Compressor Surge ◽  
Marine Diesel ◽  
The Impact

The operation during compressor surge of a medium speed marine diesel engine was examined on a test bed. The compressor of the engine's turbocharger was forced to operate beyond the surge line, by injecting compressed air at the engine intake manifold, downstream of the compressor during steady-state engine operation. While the compressor was surging, detailed measurements of turbocharger and engine performance parameters were conducted. The measurements included the use of constant temperature anemometry for the accurate measurement of air velocity fluctuations at the compressor inlet during the surge cycles. Measurements also covered engine performance parameters such as in-cylinder pressure and the impact of compressor surge on the composition of the exhaust gas emitted from the engine. The measurements describe in detail the response of a marine diesel engine to variations caused by compressor surge. The results show that both turbocharger and engine performance are affected by compressor surge and fast Fourier transform (FFT) analysis proved that they oscillate at the same main frequency. Also, prolonged steady-state operation of the engine with this form of compressor surge led to a non-negligible increase of NOx emissions.

Coupled Thermo-Flowing 3D Steady State Model of Friction Stir Welding Process

2013 ◽  
Vol 470 ◽  
pp. 325-329 ◽  
Author(s):  
Jun Hua Cui ◽  
Wei Xu ◽  
Zheng Hua Guo
Keyword(s):  
Steady State ◽  
Friction Stir Welding ◽  
Welding Process ◽  
State Model ◽  
Analysis Software ◽  
Friction Stir ◽  
Steady State Model ◽  
Model Of Friction ◽  
Energy Equations ◽  
The Impact

The coupled thermo-flowing 3D steady-state model of friction stir welding model is established based on fluid mechanics. With analyzing the impact of pin shoulder and pin on heat producing, the model considers the influence of pin on the heat producing processing. The model applies viscoplastic constitutive equations to describe the material, and turbulence model to simulate the material flowing behavior. With the additional turbulence kinetic energy equations and flow boundary condition equations, the model is established. With Comsol Multiphysics finite analysis software, a process simulation was carried out, and the results reflect that the model can reveal the steady state characteristics of thermo and material flowing behavior of friction stir welding.

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