Turboshaft Engine Research Articles

Study on erosion wear characteristics of aero-compressor blades considering distortion degree

A Tabakoff model of a certain type of turboshaft engine compressor blade was established, and the effects of no, mild, moderate, and severe distortions on blade erosion pattern were obtained. Based on particle velocimetry and erosive wear experiments, the Tabakoff model parameters (k12, V1, V2, V3, and θ0) were obtained. The effect of four distortion degrees on blade erosion pattern and erosion rate was studied. With an increase in the distortion degree, the erosion area of the rotor blade pressure surface is found to move toward the leading edge and blade tip. The erosion area of the stator blade suction surface moves toward the leading edge and blade root, whereas that of the pressure surface moves toward the blade root.

Формування математичної моделі турбовального двигуна

The subject of the study is the process of forming a mathematical model (MM) of a turboshaft gas turbine engine and a twin-engine helicopter power plant, which provides the determination of parameters of the working process in steady and transient operating modes for use in the estimation of dynamic characteristics, in the analysis and synthesis of engine and helicopter automatic control systems. The goal is to substantiate the structure and methodology of MM formation intended for use in real and accelerated time scale systems. Tasks: implementation of the previously proposed MM structure taking into account the turboshaft engine performances, development of a methodology for determining the MM coefficients based on known information about the static and dynamic properties of the engine, and formation of the MM structure of a two-engine helicopter power plant. For this, the methods of the theory of airjet engines and the theory of linear dynamic systems are used. The following results were obtained: the structure of a multimode high-speed MM of a turboshaft engine and a two-engine power plant was formed and tested. The scientific and practical novelty of the obtained results is as follows: the structure of the multimode linearized MM of the turboshaft engine is formed, which consists of static and dynamic submodels implemented in corrected parameters; the modeling technique was worked out on a simplified model, compiled considering expert information about the static and dynamic properties of the engine in the considered operation area. Formulas were obtained that relate the coefficients of the linear dynamic model to the values of the time constants of the rotors and the sensitivities obtained from the static characteristics; transient characteristics of the engine based on changes in fuel consumption and load power are determined, which correspond to physical knowledge about the engine; the modeling methodology and MM structure of a two-engine power plant were formed, which is distinguished by the combination of individual static and linear dynamic models of two engines with a single nonlinear dynamic model of the helicopter rotor; a simplified MM load necessary for testing the MM of the engine installation is proposed, which provides the calculation of the power consumed by the rotor, depending on the angular position of the blades.

Ринок та перспективи газотурбінних двигунів для важких транспортних гелікоптерів

The subject of this study is the current state of the market and prospects for the development of heavy transport helicopters and their power plants. This article provides a classification of helicopters and a segment of medium-heavy and heavy helicopters with gas turbine engines. The field of application of such helicopters is briefly described. The purpose of this article is to evaluate the activities of Element JSC in the field of developing electronic control systems for gas turbine engines for heavy class helicopters. Such systems for Element JSC, in particular, are RDTs-2500 and RDTs-450M-117B units for TV3-117VMA-SBM-1B series turboshaft engines, created by Motor Sich JSC. Objective: To provide information on the main types of heavy helicopters manufactured and operated today, as well as a description of the gas turbine engines installed on these helicopters. The field of application of such helicopters is briefly described. The segment of heavy helicopters with gas turbine engines is the largest in terms of money on the world market of civil helicopters, and the forecast of deliveries of such helicopters for the next 5-7 years is given. Most helicopter models are not completely new developments, but have been improved over many years. Characteristic design features of heavy helicopters with gas turbine engines, features of the arrangement of units and equipment are given. The main structural and structural features of gas turbine engines of various manufacturers and the types of helicopters on which they are installed are given. Brief information on Russian and Ukrainian gas turbine engines - VK-2500 and TV3-117VMA-SBM-1B is provided separately. The results. Despite the active development of eVTOL technologies in the sector of small rotorcrafts, the development and improvement of gas turbine engines continues. Heavy helicopters of both traditional and non-traditional designs are being developed. Conclusions. Modernization of the design and "remotorization" of the Mi-8 helicopter is a good opportunity for "Motor-Sich Helicopters", but it needs its own developments. Many promising Ukrainian developments were canceled due to the war. Analysis of the technical characteristics of TVaD for heavy helicopters shows that domestic engines are almost in no way inferior to their European and American competitors. Promising TVaD of SE "Ivchenko-Progress" AI-130 with a capacity of 3,000 hp. can become an even more attractive proposition.

Turbo-shaft engine adaptive neural network control based on nonlinear state space equation

Intelligent Adaptive Control (AC) has remarkable advantages in the control system design of aero-engine which has strong nonlinearity and uncertainty. Inspired by the Nonlinear Autoregressive Moving Average (NARMA)-L2 adaptive control, a novel Nonlinear State Space Equation (NSSE) based Adaptive neural network Control (NSSE-AC) method is proposed for the turbo-shaft engine control system design. The proposed NSSE model is derived from a special neural network with an extra layer, and the rotor speed of the gas turbine is taken as the main state variable which makes the NSSE model be able to capture the system dynamic better than the NARMA-L2 model. A hybrid Recursive Least-Square and Levenberg-Marquardt (RLS-LM) algorithm is advanced to perform the online learning of the neural network, which further enhances both the accuracy of the NSSE model and the performance of the adaptive controller. The feedback correction is also utilized in the NSSE-AC system to eliminate the steady-state tracking error. Simulation results show that, compared with the NARMA-L2 model, the NSSE model of the turbo-shaft engine is more accurate. The maximum modeling error is decreased from 5.92% to 0.97% when the LM algorithm is introduced to optimize the neural network parameters. The NSSE-AC method can not only achieve a better main control loop performance than the traditional controller but also limit all the constraint parameters efficiently with quick and accurate switching responses even if component degradation exists. Thus, the effectiveness of the NSSE-AC method is validated.

Assessment of hydrogen gas turbine-fuel cell powerplant for rotorcraft

Conventional turboshaft engines are high power density movers suffering from low efficiency at part power operation and producing significant emissions. This paper presents a design exploration and feasibility assessment of a hybrid hydrogen-fueled powerplant for Urban Air Mobility (UAM) rotorcraft. A multi-disciplinary approach is devised comprising models for rotorcraft performance, tank and subsystems sizing and engine performance. The respective trade-offs between payload-range and mission level performance are quantified for kerosene-fueled and hybrid hydrogen tilt-rotor variants. The effects of gas turbine scaling and fuel cell pressurization are evaluated for different hybridization degrees. Gas turbine scaling with hybridization (towards the fuel cell) results in up to 21% benefit in energy consumption relative to the non-scaled case with the benefits being more pronounced at high hybridization degrees. Pressurizing the fuel cell has shown significant potential as cell efficiency can increase up to 10% when pressurized to 6 bar which translates to a 6% increase in overall efficiency. The results indicate that current fuel cells (1 kW/kg) combined with current hydrogen tank technology severely limit the payload-range capability of the tilt-rotor. However, for advanced fuel cell technology (2.5 kW/kg) and low ranges, hybrid powerplant show the potential to reduce energy consumption and reduce emissions footprint.

Effect of Self-Recirculating Casing Treatment on the Aerodynamic Performance of Ultra-High-Pressure-Ratio Centrifugal Compressors

The motivation to design a more efficient and compact aircraft engine leads to a continuous increase in overall pressure ratio and decrease in the stage number in compressors. Compared to the traditional multi-stage compressor, a single-stage ultra-high-pressure-ratio centrifugal compressor with a pressure ratio higher than 10.0 can significantly improve the engine’s power-to-weight ratio and fuel economy with a reduced structure complexity. Thus, it has great potential to be adopted in the compression system of advanced aero engines, such as turboshaft engines, in the future. However, the highly narrow Stable Flow Range (SFR) of ultra-high-pressure-ratio centrifugal compressors is a severe restriction for engineering applications. This research focuses on the aerodynamic performance of a ultra-high-pressure-ratio centrifugal compressor, and three-dimensional simulation is employed to investigate the effect of Self-Recirculating Casing Treatment (SRCT) on the performance and stability of the centrifugal compressor. Firstly, the parametric model of SRCT is established to investigate the effect of geometry parameters (rear slot distance and rear slot width) on the aerodynamic performance of the centrifugal compressor. It is concluded that SRCT improves the compressor’s SFR but deteriorates its efficiency. Also, a non-linear and non-monotone relationship exists between the SFR and rear slot distance or width. Then, the flow mechanism behind the effect of SRCT is explored in detail. By introducing the SRCT, an additional flow path is provided across the blade along the circumferential direction, and the behavior of the shock wave and tip leakage flow is significantly changed, resulting in the obviously different loading distribution along the streamwise direction. As a result, the mixing and flow separation loss are enhanced in the impeller flow passage to deteriorate the efficiency. On the other hand, the blockage effect caused by the mixing of slot recirculation and mainstream flow near the impeller inlet increases the axial velocity and reduces the incidence angle below the 90% spanwise section, which is considered to effectively stabilize the impeller flow field and enhance the stability.

Off Design Performance Analysis of a Turbo Shaft Engine

The off-design performance of a gas turbine engine is strongly influenced by the characteristics of individual components. It involves the interplay of a large number of variables and would require a detailed computer code. In this paper, an effort is made to predict the influence of performance characteristics of individual components on the off-design performance of the engine. For this purpose, a computer code is developed with necessary iterations and convergence criteria. Parameters are estimated with respect to speeds ranging from 39500 rpm to 50500 rpm for a typical turbo-shaft engine with free power turbine. The effect of altitude on these parameters up to 6 km is also studied. Variation of specific heat and enthalpy with respect to temperature and fuel to air ratio is considered to estimate the performance calculations more accurately and to simulate a real engine behavior as close as possible.

Challenges in Aero-Engine Joint Venture Design Development Certification and Technology Transfer Process in India

The development in the field of gas turbine engine from first generation to fifth generation is evident from the history. The ever changing requirement has driven continuous development in the area and has led the designers to struggle for best propelling machine to fly. In the global scenario it is evident that for keeping up with the pace of advancements in the gas turbine engine field, expertise is required for each subsystem/module. Major design houses of the world are now adopting an approach of developing expertise in a specialized area of aero engine development. Having developed the expertise in a specialized area, the complex aero engine can be developed through the joint venture route. In a country like India this new development philosophy through joint venture has been adopted in the recent past for many of the aero engine components. The critical issue for such a product to enter into the armed forces is certification and its associated manufacturing quality standards. This paper highlights the basic issues and challenges associated in a typical Indian Joint Venture for design development and Certification of aero engines and system. The paper also highlights the possible approach which can be adopted based on the real experience of certification process for a turbo shaft engine joint venture program recently undertaken in India between HAL and an OEM abroad.

Causes and Remedies of High Jet Pipe Temperature in Turbo Shaft Engines : Case Studies

Jet Pipe Temperature (JPT) is a representation of Turbine Entry Temperature (TET) and is one of the most critical parameters in a gas turbine engine. Excessive turbine temperatures result in decreased life or catastrophic failure of the engine. This paper presents some case studies analyzing the causes of such high JPT in a turbo shaft engine in association with helicopter operation, effect of high JPT on engine performance and life and highlights the precautions and preventions to be adopted from engine point of view.

Qualification of Compressor Impeller for Aero-Engine Application

This paper presents the approach for qualification of indigenously developed compressor impeller for aero engine application. Indigenisation is understood to be the most important tool for effective technical empowerment of a developing nation. Indigenisation philosophy is adopted by several countries in various fields such as power, infrastructure, aerospace, military equipments and etc. Indigenous development fills the technical, financial and time frame gap between imports and ab-initio design and development. Hence, for a healthy technical growth of any developing nation, Indigenous development activities should go along with ab-initio design activities. Indigenous development has become an integral process of activities of Defence sectors due to its potential benefits. Indian defence imports stands at staggering 65 % of the total defence acquisition. In order to make the best use of indigenization opportunities in the defence sector, conservative figures would suggest an amount more than 100,000 crores. This gives an indication of the potential and benefits of indigenous development in defence sectors.
 In this paper a methodology for indigenous development of a military turboshaft engine compressor impeller is discussed. This activity has enabled uninterrupted supply of the component and a substantial Foreign Exchange savings. This paper specifies the various tests conducted over the forging. It also brings out the results of cyclic spin test on the component for 22500 cycles as life substantiation, 15% and 22% over speed test as structural integrity substantiation and 150 hours type test on engine for quality and assembly substantiation.
 This indigenous development procedure described in this paper can be readily extended to suitable critical aero engine component.

Reliability Analysis of a Turboshaft Engine

This paper brings out estimation of Average Service Life (ASL) and Mean Life of a turboshaft engine powering a single engined helicopter. This has been carried out through reliability analysis over defect investigation, repair and overhaul data for a period of 5 years. The implication of ASL and Mean life are deliberated. Critical areas for availability improvement for different operators are also highlighted in the paper.

Exergetic, sustainability and environmental assessments of a turboshaft engine used on helicopter

Exergetic, sustainability and environmental assessments of a turboshaft engine used on helicopter

Experimental Analysis on the Operating Line of Two Gas Turbine Engines by Testing with Different Exhaust Nozzle Geometries

This paper presents a special analysis study about the gas turbine operating line, and an overall description of a gas turbines project, based on experimental data from two particular applications, in order to convert two different types of aero engines into the same engine configuration. The experimental works were carried out with the aim of converting an Ivchenko AI-20K turboprop and a Rolls-Royce Viper 632-41 turbojet into free turbine turboshaft engines, to be used in marine propulsion, and also to obtain an experimental database to be used in other gas turbine applications. In order to carry out the experimental work, the engines were tested in turbojet configuration, to simulate the free turbine load by using jet nozzles with different geometries of the outlet cross-section. Following the engines’ tests, a series of measured data were obtained, through which it was possible to experimentally determine the operating line of some engine components such as the compressor, turbine, and exhaust jet nozzle. This paper is comprehensive and useful through its scientific and technical guidelines, the operation curves coming in handy in the thermodynamic analysis and testing methodology for researchers dealing with similar applications.

Study on the water ingestion performance of compressor with inlet particle separator

Abstract For an aero turbo-shaft engine, rain water enters the intake protection device and the morphology of water droplets after hitting the wall will affect the internal flow of the compressor. In this paper, Sommerfeld number was used to determine the shape of water droplets after they hit the wall. The flow field and characteristics of the compressor with inlet particle separator under different water ingestion conditions were studied with considering the impact of water film and droplets splashing near the wall. The results show that the entry of water droplets deteriorates the internal flow field of the compression component, and the water film affects the flow state of the airflow near the wall. Compared to the effect of the splashing factor, the viscous resistance effect of water film near the wall on the airflow and boundary layer can cause a significant reduction in the characteristics and stability of the compressor.

Influence of SiO2 and Al2O3 particles on erosion wear of aero-compressor blades

When helicopters take off and land in areas such as plateaus and deserts, both SiO2 and Al2O3 particles in the external environment can cause erosion wear on compressor blades, compromising helicopter safety during operation. The aim of this study is a model of a pre-1.5-stage compressor from a turboshaft engine. The experimental schemes of SiO2 and Al2O3 particle velocimetry and Ti–6Al–4V alloy erosion wear were designed to construct a Tabakoff erosion wear model. The influence of particle density and hardness on the erosion rate was deduced. The trajectories and velocities of the two types of particles were analyzed using the gas-solid two-phase flow method. The erosion pattern of the blade was investigated to determine the influence of the two-particle on the erosion rate of the blade. The results showed that Al2O3 particles produced more energy than SiO2 particles and had a higher ability to erosion materials. The maximum impact angle of both the SiO2 and Al2O3 particles on the Ti–6Al–4V alloy was 30°, and the erosion rate of Al2O3 particles at this angle was 66% higher than that of the SiO2 particles. The erosion patterns of the compressor guide, rotor, and stator blades did not vary with the particle material; however, the erosion rate caused by the Al2O3 particles on the blade was larger than that of the SiO2 particles. The maximum erosion rate on the compressor occurred at 98.5% span of the leading edge of the rotor blade, and the erosion rate generated by the Al2O3 particles at this position was 114% higher than that of the SiO2 particles. This research can provide a theoretical reference for anti-erosion protection designs and vibration characteristic analysis of aero-engine compressor blades.

An efficient intelligent energy management strategy based on deep reinforcement learning for hybrid electric flying car

Hybrid electric flying cars hold clear potential to support high mobility and environmentally friendly transportation. For hybrid electric flying cars, overall performance and efficiency highly depend on the coordination of the electrical and fuel systems under ground and air dual-mode. However, the huge differences in the scale and fluctuation characteristics of energy demand between ground driving and air flight modes make the efficient control of energy flow more complex. Thus, designing a power coordinated control strategy for hybrid electric flying cars is a challenging technical problem. This paper proposed a deep reinforcement learning-based energy management strategy (EMS) for a series hybrid electric flying car. A mathematical model of the series hybrid electric flying car driven by the distributed hybrid electric propulsion system (HEPS) which mainly consists of battery packs, twin turboshaft engine and generator sets (TGSs), 16 rotor-motors, and 4 wheel-motors is established. Subsequently, a Double Deep Q Network (DDQN)-based EMS considering ground and air dual driving mode is proposed. A simplified method for the number of control variables is designed to improve exploration efficiency and accelerate the convergence speed. In addition, the frequent engine on/off problem is also taken into account. Finally, DDQN-based and dynamic programming (DP)-based EMSs are applied to investigate the power flow distribution for two completely different hypothetical driving scenarios, namely search and rescue (SAR) scenarios and urban air mobility (UAM) scenarios. The results demonstrate the effectiveness of the DDQN-based EMS and its capacity of reducing the computation time.

An adaptive matching control method of multiple turboshaft engines

In order to overcome the problem that the conventional multi-engine matching control method never balance the service lives of engines and transmission system synchronously while engines have individual differences and performance degradations, an adaptive matching control method of multiple turboshaft engines is proposed and designed. Firstly, based on the deep neural network (DNN), the onboard adaptive model is established to simulate the coupling dynamics of multiple engines. It can automatically trace engine output torques, discharge temperatures of gas turbine and rotational speeds of compressor. Then, the numerical optimization problem of multi-engine matching is built to obtain the optimal discharge temperatures of gas turbine online. It is featured with a multi-objective function that integrates the maximum deviations of engine output torques, discharge temperatures of gas turbine and the relative rotational speeds of compressor. Finally, the optimal discharge temperatures of gas turbine are input to the conventional matching strategy to accomplish the adaptive matching control. The results demonstrate that compared with the conventional matching strategy, when the number of turboshaft engine is three, the adaptive matching control method can dramatically decrease the maximum matching error of compressor speeds and engine output torques by more than 40% and 60% individually with the maximum deviation of the discharge temperatures of gas turbine no more than 3%. It proves to be conducive to balancing the service lives of multiple engines and transmission system.

Study of a Regional Turboprop Aircraft with Electrically Assisted Turboshaft

Hybrid-Electric Propulsion (HEP) could be part of the solution to decrease emissions associated with regional commercial aviation. This study presents results for the aircraft level fuel reduction potential of a regional turboprop concept with an HEP architecture and Entry-Into-Service (EIS) in 2035+. The configuration specifically tackles the elaborated challenges of introducing an additional electrical energy source to the configuration by employing a twofold electrical assistance to a turboshaft engine in combination with an innovative thermal management concept. Relevant components and disciplines were modeled and incorporated into an integrated aircraft design environment. The behavior and interaction of the HEP architecture with the aircraft was thoroughly investigated. A best-performing configuration was derived and compared with a conventional reference configuration following a State-of-the-Art (SoA) reference aircraft approach. For a typical mission with 200 nmi range, a block fuel reduction of 9.6% was found. However, the assumed battery performance characteristics limited the reduction potential and led to a fuel burn increase for the 600 nmi design mission. Furthermore, sourcing the non-propulsive subsystems directly from the on-board battery was detrimental. The innovative Thermal Management System (TMS) located in the propeller slipstream showed a synergistic effect with the investigated configuration.

Vibration reduction design for a shared bearing bore of a turboshaft engine

The traditional dynamic analysis of the finite element structure is mostly focused on the mode analysis. In the paper, the finite element method is combined with the power flow analysis to analyze and optimize the vibration transmission characteristics of the shared bearing bore, so that the vibration energy transmitted to the mounting flange is minimized. The analysis shows that the elastic ring and the outer case play an important role in vibration transmission and reduction. An optimization model is established to improve the vibration reduction rate of the shared bearing bore. The results show that the optimization can effectively improve the vibration reduction rate of the shared bearing bore, approximately 15 % reduction of peak response is achieved.

The hybrid concept of turboshaft engine working according to Humphrey cycle dedicated to variety power demand – CFD analysis

The paper presents a new concept of the turbine engine in the area of pressure gain combustion (PGE). The engine works according to Humphrey’s cycle. Minor modification in construction has allowed power generation of 500 kW, 700 kW, 1000 kW, and 1800 kW. The concept successfully resolved the challenges related to the temporary opening and closing of the combustion chamber. The presented valve timing system has ensured effective gas flow and what stands behind it, an effective process of conversion of a high-pressure gas impulse into mechanical energy. Rotating combustion chambers enabled the application of an effective sealing system. The concept characterizes simple construction and potentially low power-to-weight coefficient. The CFD numerical analysis of the presented engine concept showed very promising effective efficiency and low specific fuel consumption.