Improvement of Turboshaft Restart Time Through an Experimental and Numerical Investigation

2020 ◽  
Author(s):  
Antoine Ferrand ◽  
Marc Bellenoue ◽  
Yves Bertin ◽  
Patrick Marconi
Keyword(s):  
Electric Motor ◽  
Thermodynamic Model ◽  
Sleep Mode ◽  
Test Rig ◽  
Gas Generator ◽  
Time Saving ◽  
Idle Speed ◽  
Flight Mode ◽  
Nominal Load ◽  
Turboshaft Engine

Abstract Inflight shutdown of one engine for twin-engine helicopters have proven beneficial for fuel consumption. A new flight mode is then considered, in which one engine is put into sleep mode (the gas generator is kept at a stabilized, sub-idle speed by means of an electric motor, with no combustion), while the second engine runs almost at nominal load. The ability to restart the engine in sleep mode is then critical for safety reasons. Indeed, the certification of this flight mode involves ensuring a close-to-zero failure rate for in-flight restarts as well as a fast restart capability of the shutdown engine. In this paper, the focus is made on improving the restart time of the shutdown turboshaft engine. Fast restart capability is necessary for flight management reasons. Indeed, in case of a failure of the engine operating close to nominal load while the other one is in sleep mode, there is no more power available and the helicopter can lose up to 15–20 meters per second during autorotation. The restart time becomes a critical parameter to limit the loss of altitude. In the configuration studied, the fast restart is achieved thanks to the electric motor designed to deliver a high torque to the gas generator shaft. This electric motor is powered by an additional battery, more powerful than the conventional one dedicated for standard restarts. The aim of the paper is to assess the potential restart time saving using an approach combining test rig data analysis and numerical results generated by a thermodynamic model able to simulate at very low rotational speed. A gas turbine engine starting process is composed of two main phases: the light-up phase and the acceleration phase. It is important to understand the detailed phenomenology of these two phases as well as the various sub-systems involved, first to highlight the influencing parameters of both phases and then to establish an exhaustive listing of the possible time optimizations. From the test rig campaign, conducted at Safran Helicopter Engines on a high power free turbine turboshaft engine, we are able to accurately break down the phases of the start-up sequence, which helps us to identify what steps of the sequence worth shortening. With the engine performance thermodynamic model, we can then use the information gathered from the test rig analysis to further predict how to save time and to give guidelines for developing new control strategies. The results of this study show that a fast restart going from sleep mode to max power speed can be up to 60% faster than a conventional restart going from sleep mode to idle speed. This is significantly faster, especially if one takes into account the higher final speed targeted by the fast restart.

Improvement of Turboshaft Restart Time Through an Experimental and Numerical Investigation

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Antoine Ferrand ◽  
Marc Bellenoue ◽  
Yves Bertin ◽  
Patrick Marconi
Keyword(s):  
Data Analysis ◽  
Thermodynamic Model ◽  
Critical Parameter ◽  
Sleep Mode ◽  
Test Rig ◽  
Time Saving ◽  
Idle Speed ◽  
Flight Mode ◽  
Startup Process ◽  
Influencing Parameters

Abstract Inflight shutdown of one engine for twin-engine helicopters has proven beneficial for fuel consumption. A new flight mode is then considered, in which one engine is put into sleep mode while the second engine runs at nominal load. The ability to restart the engine in sleep mode is then critical for safety reasons. Indeed, the certification of this flight mode involves ensuring a close-to-zero failure rate for in-flight restarts and a fast restart capability of the shutdown engine (focus of this paper). Fast restart capability is necessary in case of a failure of the operating engine. Indeed, there is no more power available, and the helicopter can lose up to 15–20 meters per second during autorotation. The restart time becomes a critical parameter to limit the loss of altitude. The aim of the paper is to assess the potential restart time saving using an approach combining test rig data analysis and numerical results generated by a thermodynamic model able to simulate at low rotational speed. It is important to understand the detailed phenomenology of the startup process and the various subsystems involved, first to highlight the influencing parameters and then to establish an exhaustive listing of the possible time optimizations. The results of this study show that a fast restart going from sleep mode to max power speed can be up to 60% faster than a conventional restart going from sleep mode to idle speed, which is significantly faster.

High Fidelity Modeling of the Acceleration of a Turboshaft Engine During a Restart

2018 ◽  
Author(s):  
Antoine Ferrand ◽  
Marc Bellenoue ◽  
Yves Bertin ◽  
Radu Cirligeanu ◽  
Patrick Marconi ◽  
...  
Keyword(s):  
Initial Conditions ◽  
Combustion Efficiency ◽  
High Fidelity ◽  
Gas Generator ◽  
Idle Speed ◽  
Flight Mode ◽  
System States ◽  
Secondary Air ◽  
Turboshaft Engine ◽  
High Level

In order to decrease the fuel consumption, a new flight mode is being considered for twin-engine helicopters, in which one engine is put into sleeping mode (a mode in which the gas generator is kept at a stabilized, sub-idle speed by means of an electric motor, with no combustion), while the remaining engine operates at nominal load. The restart of the engine in sleeping mode is therefore deemed critical for safety reasons. This efficient new flight mode has raised the interest in the modeling of the restart of a turboshaft engine. In this context, the initial conditions of the simulations are better known relative to a ground start, in particular the air flow through the gas generator is constant, the fuel and oil system states are known and temperatures of the casings are equal to ambient. During the restart phase of the engine, the gas generator speed is kept at constant speed until the light-up is detected by a rise in inter-turbine temperature, then the starter torque increases, accelerating the engine towards idle speed. In this paper, the modeling of the acceleration of the gas generator from light-up to idle and above idle speeds is presented. Details on the light-up process are not addressed here. The study is based on the high-fidelity aero-thermodynamic restart model that is currently being developed for a 2000 horse power, free turbine turboshaft. In this case, the term high-fidelity refers not only to the modeling of the flow path components but it also includes all the subsystems, secondary air flows and controls with a high level of detail. The physical phenomena governing the acceleration of the turboshaft engine following a restart — mainly the transient evolution of the combustion efficiency and the power loss by heat soakage — are discussed in this paper and modeling solutions are presented. The results of the simulations are compared to engine test data, highlighting that the studied phenomena have an impact on the acceleration of the turboshaft engine and that the model is able to correctly predict acceleration trends.

Cascade Research on a Small, Axial, High-Work, Cooled Turbine

1975 ◽  
Author(s):  
H. F. Due ◽  
A. E. Easterling ◽  
C. Rogo
Keyword(s):  
Flow Coefficient ◽  
Experimental Program ◽  
Inlet Temperature ◽  
Gas Generator ◽  
Cold Flow ◽  
Cooling Flow ◽  
Mechanical Constraints ◽  
Turboshaft Engine ◽  
Turbine Design ◽  
Design Power

This paper presents the results of an experimental cascade investigation of the aerodynamic performance of a 1.524-cm (0.6-in.) blade height, low aspect ratio, highly loaded, cooled turbine. The experimental program was performed with a cold flow annual sector cascade with various geometric and aerodynamic perturbations. The perturbation included nozzle endwall contour, inlet turbulence and velocity distortion, stator and rotor solidity, rotor loading and nozzle cooling flow and point of injection. The turbine design evolved through a parametric analysis considering a turboshaft engine configuration required to have a 750-hr life at design power output and satisfy realistic mechanical constraints. The gas generator turbine configuration selected for investigation was a single-stage turbine with a turbine inlet temperature of 1316 C (2400 F) and an actual work output of 418.68 kJ/kg, (180 Btu/lb). The baseline turbine was sized for a stage work coefficient of 5.0 at the hub radius and an average flow coefficient of 0.675 for a best mechanical-aerothermodynamic compromise to meet realistic engine constraints.

The Co-Turboshaft: A Novel Gas Turbine Powerplant for Heavy Equipment

1979 ◽  
Author(s):  
D. A. J. Millar ◽  
M. S. Chappell ◽  
R. Okelah
Keyword(s):  
Gas Turbine ◽  
Control Strategies ◽  
Output Shaft ◽  
Speed Ratio ◽  
Inlet Temperature ◽  
Gas Generator ◽  
Turbine Engine ◽  
Engine Torque ◽  
Performance Effects ◽  
Turboshaft Engine

A major advantage of the two-shaft gas turbine as a prime mover is the steep torque-speed characteristic, so that the stall torque is typically twice the design torque. The co-turboshaft engine has a torque-speed curve which can be more than twice as steep as the conventional engine, so that only a rudimentary transmission would be required for normal operations. The co-turboshaft gas turbine engine has a co-rotating compressor case which is geared, together with the free power turbine, to the output shaft. As load increases and output shaft speed decreases, the effective gas generator speed increases, with no increase in rotor speed, and the power output rises. The engine has a torque-speed curve with up to four times the slope of a conventional free shaft turbine engine torque curve. This paper reviews results of testing a compressor with a co-rotating casing, and presents the results of simulating a typical engine using a hybrid computer to predict engine steady state performance. Effects of different design choices of compressor casing speed ratio are shown on engine torque, power and turbine inlet temperature characteristics. Control strategies for some possible applications, such as off-road vehicles and construction equipment, are discussed in relation to their likely duty cycles.

Thermodynamic and Mechanical Design Concept for Micro-Turbojet to Micro-Turboshaft Engine Conversion

2020 ◽  
Author(s):  
Christoph Öttl ◽  
Reinhard Willinger
Keyword(s):  
Mechanical Design ◽  
Thermodynamic Cycle ◽  
Design Concept ◽  
Specific Power ◽  
Gas Generator ◽  
Cycle Simulation ◽  
Turbojet Engine ◽  
Specific Power Output ◽  
Power Turbine ◽  
Turboshaft Engine

Abstract In this work, a design concept for micro-turbojet to micro-turboshaft engine conversion is presented. This is motivated by a lack of available micro-turboshaft engines which is shown in the market survey conducted. Thus, the presented concept deals with the conversion of an existing micro-turbojet engine to a micro-turboshaft engine for a specific power output. The conversion is shown using the micro-turbojet engine OLYMPUS HP from AMT Netherlands. Furthermore, the simultaneously developed analytical preliminary design of the additional single-stage power turbine is shown besides a thermodynamic cycle simulation. This has been done to obtain the unknown gas generator outlet condition which is similar to the power turbine’s inlet condition. Within the cycle calculation, occurring losses due to the small dimensions have also been considered. During the design process, different combinations of work coefficient and mean diameter of the power turbine were investigated to minimize the required gear box ratio for a given rotor speed in terms of weight minimization. To keep losses in the power turbine low, the preliminary blade row has finally been improved using CFD calculations.

scholarly journals Experimental Investigation of the Seamless Gearshift Mechanism Using an Electric Motor and a Planetary Gear-Set

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6705
Author(s):  
Sun Je Kim ◽  
Kyung-Soo Kim
Keyword(s):  
Experimental Investigation ◽  
Electric Motor ◽  
Test Bench ◽  
Planetary Gear ◽  
Test Rig ◽  
Limited Size ◽  
Gear Shift ◽  
Operating Concept ◽  
Expected Performance ◽  
Vehicle Technology

Vehicle transmission which has discrete gear-stages inevitably produces torque drop during shifting gears. This torque drop should be minimized because it may lead to uncomfortable driving feeling and degradation of acceleration performance. In accordance with the spread of electric-powered vehicle technology, this study proposes novel transmission architecture to eliminate torque drop during shifting gears by using one electric motor and verifies its operating concept through experiments with a test-bench. The proposed transmission, called CGST (clutchless geared smart transmission) can synchronize the gear-shaft to be engaged for the next gear-stage with the output shaft by using a planetary gear-set and an electric motor. The CGST has a dual input gear-box with even and odd gear-stages on different input shafts, and the planetary gear-set and the electric motor control the speeds of each input shafts to smoothly engage the next gear-stage. This idea was verified by the simplified test-rig in this study. Three distinct scenarios for gear-shift including starting from engine idling, odd to even gear-shift, and even to odd gear-shift were conducted in the experiment. The shifting performance of the CGST was evaluated by comparing it with the results of the manual transmission (MT). As a result, the CGST shows only 24% of torque drop of the MT, and torque oscillation followed after gear-shifting is reduced by 26%. Although the developed test bench was of limited size, the possibility and expected performance of the CGST have been confirmed as the solution for seamless transmission.

Electric Motor Emulator Versus Rotating Test Rig

2012 ◽  
Vol 7 (3) ◽  
pp. 22-27
Author(s):  
Horst Hammerer ◽  
Dieter Strauss
Keyword(s):  
Electric Motor ◽  
Test Rig

The V.P.I. Gas Turbine and Turbomachinery Research Laboratory

1977 ◽  
Author(s):  
W. F. O’Brien ◽  
R. R. Jones ◽  
H. L. Moses ◽  
J. F. Sparks
Keyword(s):  
Gas Turbine ◽  
Research Laboratory ◽  
High Speed ◽  
Test Cell ◽  
Gas Generator ◽  
Related Research ◽  
Coupled Mode ◽  
Governing System ◽  
Turboshaft Engine

A recently completed facility for high-speed turbomachinery and gas turbine related research is described. A test cell houses a 3000 hp turboshaft engine which is capable of driving research rotors in a direct-coupled mode at speeds to 17,000 rpm. Gearboxes provide for reverse drive and speeds from 8000 to 24,000 rpm. An automatic governing system controls gas generator and load speeds, and provides overspeed protection. Research instrumentation includes on-rotor telemetry equipment for transmission of data from research rotors.

scholarly journals Steady-State and Transient Performance Simulation of a Turboshaft Engine With Free Power Turbine

1999 ◽  
Author(s):  
Changduk Kong ◽  
Jayoung Ki ◽  
Kwangwoong Koh
Keyword(s):  
Steady State ◽  
Performance Analysis ◽  
Analysis Program ◽  
Transient Performance ◽  
Gas Generator ◽  
Performance Simulation ◽  
Performance Requirements ◽  
Power Turbine ◽  
Turboshaft Engine ◽  
Steady State Performance

Steady-state and transient performance analysis programs for 200kw-class small turboshaft engine with free power turbine were developed. An existing turbojet engine was used for the gas generator of the developed turboshaft engine, and it was modified to satisfy performance requirements of this turboshaft engine. To verify the availability of steady-state performance program for this engine: the program was applied to the same type gas turbine test unit, and the analysis results were compared to experimental results. The developed transient performance analysis program using the CMF (Constant Mass flow) method was utilized to analysis in the cases of fuel step increase and the ramp increase.

Simulation of the Transient Response of a Helicopter Turboshaft Engine to Hot-Gas Ingestion

2008 ◽  
Author(s):  
Gu¨lru Koc¸er ◽  
Og˘uz Uzol ◽  
I˙lkay Yavrucuk
Keyword(s):  
Transient Response ◽  
Algebraic Equations ◽  
Gas Generator ◽  
Simulation Code ◽  
Exhaust Gases ◽  
Transient Behaviour ◽  
Hot Gas ◽  
Speed Governor ◽  
Linear Algebraic Equations ◽  
Turboshaft Engine

Hot-Gas Ingestion (HGI) to the engines can potentially occur when a rotorcraft or a VTOL/STOVL fixed-wing aircraft is operating in close proximity to the ground. Especially for helicopters, due to the rotor downwash hot exhaust gases get recirculated into the engine inlet. Similar conditions may also occur due to the ingestion of hot exhaust gases from rocket launchers or gun fire. In this study, we present the results of a simulation of the transient response of a helicopter turboshaft engine to HGI. Specifically for this study we will present the results for the T800-LHT-800 turboshaft engine. The simulations are performed using an in-house generic simulation code based on an aerothermal model, which consists of the governing equations representing the aero-thermodynamic process of each engine component. The algorithm is composed of a set of differential equations and a set of non-linear algebraic equations which are solved numerically in a sequence. A simple proportional control algorithm is also incorporated into the simulation code, which acts as a simple speed governor. Simulation results show that the code has the potential to correctly capture the transient behaviour of a turboshaft engine under various HGI conditions, such as the reduction in the gas generator speed and the power levels as well as the decrease in the compressor surge margin. The code can also be used for developing engine control algorithms as well as health monitoring systems.

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