Investigation of low emission combustors using hydrogen lean direct injection

One of the key technology challenges for the use of hydrogen in gas turbine engines is the performance of the combustion system, in particular the fuel injectors. Tests were conducted to measure the nitrogen oxide (NOx) emissions and combustion performance at inlet conditions of 588 to 811 K, 0.4 to 1.4 MPa, and equivalence ratios up to 0.48. All the injectors were based on Lean Direct Injection (LDI) technology with multiple injection points and quick mixing. One challenge to hydrogen-based premixing combustion systems is flashback since hydrogen has a reaction rate over 7 times that of Jet-A

Acoustic characteristics of the flow over different shapes of nozzle chevrons,

The objective of this paper is to present a comparison between different types of chevrons and their influence on the acoustic power level radiated by the flow over them. The comparison was performed using a two-dimensional simulation of the flow over four different shapes of chevrons resulting propagation of the acoustic waves for each shape. Acoustic characteristics were revealed studying the main flow parameters (pressure, velocity, kinetic energy) in order to be able to discover the most efficient shape of chevron regarding the acoustic power level emitted

Analysis for a wing nacelle configuration

The paper presents CFD results for a wing-nacelle configuration, in order to be testedagainst an analytic solution considering nacelles as chord discontinuities

Advanced Trailing Edge Blowing Concepts for Fan Noise Control

This study documents trailing edge blowing research performed to reduce rotor / stator interaction noise in turbofan engines. The existing technique of filling every velocity deficit requires a large amount of air and is therefore impractical. The purpose of this research is to investigate new blowing configurations in order to achieve noise reduction with lesser amounts of air. Using the new configurations air is not injected into every fan blade, but is instead varied circumferentially. For example, blowing air may be applied to alternating fan blades. This type of blowing configuration both reduces the amount of air used and changes the spectral shape of the tonal interaction noise. The original tones at the blade passing frequency and its harmonics are reduced and new tones are introduced between them. This change in the tonal spectral shape increases the performance of acoustic liners used in conjunction with trailing edge blowing

Acoustic investigation on nozzles with different types of six lobed chevrons

This paper deals with a few aspects of the notion of chevron and the process that helps reducing the noise pollution. Based on the gas dynamic and geometrical parameters of a single flow jet engine a model of CFD data processing is made. In this process the influence of chevrons on acoustic wave intensity produced by the jet can be observed. A series of tests on six lobed triangular chevrons are discussed in order to settle the influence of the geometrical parameters on the flow and on the jet acoustics. Finally the paper presents the contribution of chevrons in noise pollution reduction

Application of a Performance-Improvement Method for Small-Size Axial Flow Turbines

As a main component of most gas-turbine engines, the axial flow turbines have been in a process of continuous improvement, reaching high efficiencies and reliability. A well-known drawback of these systems is the rapid decrease in performance when operating at lower than nominal conditions. Thus, a novel performance-enhancement method for axial turbines operating at partial loads has been previously proposed and numerically characterized. In this paper, one applies the aforementioned method for a smaller size axial flow turbine, part of a gas-generator assembly for a microjet engine, to determine, by the use of CFD analysis, the influence of the system at different partial regimes across the working line. A logical scheme based on iterative steps and multiple numerical simulations is also used to determine the engine response to the injection of compressor bleed air into the turbine passages. The results show, as determined in the previous study, that the generated power can be increased for all partial regimes, with the influence being more noticeable at higher regimes, leading to a reduction in fuel consumption in order to achieve the same regimes

Acoustic control study of turbofan nozzles with triangular chevrons

This paper has a small part dealing with the notion of chevron and the process that helps reducing the noise pollution. Based on the gas dynamics and the geometrical parameters of the turbofan jet engine a model of CFD data processing is created. In this process the influence of chevrons on acoustic wave intensity produced by the jet is observed by analyzing this process. A series of tests have been made on 10 si 20 lobed chevrons. The combination between them and the 7 resulting cases have been studied, namely the triangular chevrons in order to settle the influence of the geometrical parameters on the flow and on the jet acoustics. Finally the contribution of the chevrons in noise pollution reduction has been highlighted

Impact of Using Chevrons Nozzle on the Acoustics and Performances of a Micro Turbojet Engine

This paper presents a study regarding the noise reduction of the turbojet engine, in particular the jet noise of a micro turbojet engine. The results of the measurement campaign are presented followed by a performances analysis which is based on the measured data by the test bench. Within the tests, beside the baseline nozzle other two nozzles with chevrons were tested and evaluated. First type of nozzle is foreseen with eight triangular chevrons, the length of the chevrons being L = 10 percentages from the equivalent diameter and an immersion angle of I = 0 deg. For the second nozzle the length and the immersion angle were maintained, only the chevrons number were increased at 16. The micro turbojet engine has been tested at four different regimes of speed. The engine performances were monitored by measuring the fuel flow, the temperature in front of the turbine, the intake air flow, the compression ratio, the propulsion force and the temperature before the compressor. In addition, during the testing, the vibrations were measured on axial and radial direction which indicate a normal functioning of the engine during the chevron nozzles testing. Regarding the noise, it was concluded that at low regimes the noise doesn’t presents any reduction when using the chevron nozzles, while at high regimes an overall noise reduction of 2–3 dB(A) was achieved. Regarding the engine performances, a decrease in the temperature in front of the turbine, compression ratio and the intake air and fuel flow was achieved and also a drop of few percent of the propulsion force

Enhancing Air Traffic Management and Reducing Noise Impact: A Novel Approach Integrating Băneasa Airport with Otopeni RO Airport

Over the years, Bucharest’s Henri Coandă International Airport has registered a constant and high increase in air traffic, in terms of both passengers and aircraft movements. This paper presents a traffic diversion solution for the Otopeni RO airport, which aims to alleviate air traffic congestion by redirecting a proportion of the planes to the nearby airport at Băneasa. The primary challenge faced by diversion to Băneasa Airport is the proximity of residential areas to the runway at distances of less than 300 m, resulting in significant noise pollution issues. At Otopeni Airport, the main operators use aircraft equipped with CFM 56 turbo engines; therefore, this study begins with an evaluation of the noise directivity of a CFM aircraft engine via measurement. The data thus collected enabled the identification of the dominant frequencies in the acoustic spectrum of the engine noise. A resonant screen solution has been proposed as a solution for Băneasa Airport, emphasizing the importance of implementing solutions to address the noise pollution faced by those living near Băneasa Airport, due to its proximity to the residential area. Various configurations of perforated metal sheets with different perforation patterns were compared to the test performance of solid sheets to optimize noise absorption. Using the impedance tube tests to achieve the highest absorption coefficient, it was determined that the optimal distance between the perforated metal sheets and the resonant screen was 30 mm. Based on the CFM 56 turbo engine noise directivity and the impedance tube tests, a multitude of numerical simulations were conducted using the IMMI software (IMMI 2011). The simulations were performed for two scenarios with and without an acoustic barrier, accounting for the typical configuration of two engines on an aircraft. The results indicate a reduction of 15 dBA with the implementation of a 4-m-high acoustic barrier, in the case of a CFM 56 engine operating at full throttle while the aircraft is on the ground. Through numerical simulations, the optimized resonant screen demonstrated its potential to significantly reduce noise levels, thereby enhancing the overall acoustic environment and quality of life for the communities surrounding Băneasa Airport. The identified findings could serve as a basis for further research and the implementation of innovative solutions to manage air traffic and reduce the impact of aircraft noise in surrounding areas

Axial Turbine Performance Enhancement by Specific Fluid Injection

Extensively used in modern gas turbine engines in various applications, ranging from aerospace, marine and terrestrial propulsion to power generation and gas pumping, the axial flow turbines have been continuously updated and are now capable of high performances and reliability. One drawback that has not yet been resolved is the poor performance of the axial turbines at lower- than-nominal regimes. To solve these shortcomings, a new method to improve the performances at partial regimes by specific fluid injection is proposed in this paper. The influence of the injection system is determined by conducting a numerical analyze, studying the influence of different parameters (i.e., number, dimensions and position of the of injection orifices) on the overall performances of the turbine. The study is completed on a single stage 1300 KW turbine with the injection system being applied to different power settings across the working line. The results show that the power generated by the turbine can be enhanced by as much as 30% for different configurations of the injection system (i.e., high number of small size orifices) and different partial regimes