SINGLE PASSAGE CFD ANALYSIS FOR NON-RADIAL FIBRE ELEMENT OF LOW PRESSURE TURBINE

2015 ◽  
Vol 76 (5) ◽  
Author(s):  
Bin Ahmad ◽  
Abdul Fattah ◽  
Bin Mamat, A. M. I.
Keyword(s):  
Combustion Engine ◽  
Flow Direction ◽  
Mechanical Energy ◽  
Pressure Ratio ◽  
Velocity Ratio ◽  
Low Pressure ◽  
Field Analysis ◽  
Electric Generator ◽  
Low Pressure Turbine ◽  
Exhaust Energy

Low Pressure Turbine (LPT) is a mixed-flow low pressure turbine meant for extracting energy from the exhaust of internal combustion engine. It converts the expanded exhaust energy into mechanical energy to drive an electric generator. The current available design of the LPT is only able to recover the exhaust energy efficiently with a pressure ratio range of 1.04 to 1.30. However, the performance efficiency deteriorates significantly when the pressure ratio exceeds 1.25. In the previous studies, flow field analysis has shown that the entropy is largely generated at the exit due to bigger vorticity. This vorticity can be minimized by optimizing the exit flow direction. This can be done by adjusting the exit camberline which reduces the deflection angle of the flow. This will effect exit flow of the fluid; subsequently reduces the exit loss as stipulated in the 1-Dimensional analysis of the turbine. Results have shown that the overall efficiency of the turbine has been improved as much as 7% at pressure ratios of 1.20. Its swallowing capacity is not largely affected at this point and its velocity ratio has shifted slightly from its design point of 0.70 to 0.65.

scholarly journals Computational performance of a-100 kW low pressure turbine to recover gas turbine exhaust energy

2019 ◽  
Vol 13 (2) ◽  
pp. 4777-4793
Author(s):  
A. A. Ahmad Zahidin ◽  
A. M. I. Mamat ◽  
A. Romagnoli
Keyword(s):  
Power Output ◽  
Pressure Ratio ◽  
Velocity Ratio ◽  
Low Pressure ◽  
Scaling Factor ◽  
Ic Engine ◽  
Low Pressure Turbine ◽  
Computational Performance ◽  
Exhaust Heat ◽  
Exhaust Energy

Low Pressure Turbine (LPT) was designed to recover exhaust energy from Internal Combustion (IC) engine. The LPT is located downstream retrieved exhaust heat energy from combustion after flowing through the high pressure turbine (HPT). The work output obtained from the exhaust energy is used to drive an electric generator with power output of 1.0kW. These was not done by commercial turbine as the low efficiency resulted when operated. The main purpose of this project is to develop a scaling model for LPT with power output up to 100kW. An existing LPT that was designed with output of 1.0 kW used as guideline to upscale the turbine. Scaling factor was obtained by comparing the baseline with power output. The turbine performance was analysed by using a commercial Computational Fluid Dynamic (CFD) ANSYS CFX. The study found that the scaling factor f, of 10 can be used to produce a 100kW at passage. Thus, the geometrical parameter will be scaled accordingly. The rotational speed is reduced from 50,000 rpm to 5,000 rpm. The CFD analysis found that 81% of total-static efficiency, ht-s at velocity ratio VR, of 0.68 and the Pressure Ratio PR, of 1.12 producing power of 119.88 kW which nearest with the design point which is at 100 kW. Despite the LPT swallowing capacity is increased by 50 times, the LPT is still limited by the operational choking Pressure Ratio, PR limitation which is 1.4.                                                   

A High Performance Low Pressure Ratio Turbine for Engine Electric Turbocompounding

2011 ◽  
Author(s):  
Aman M. I. Mamat ◽  
Muhamad H. Padzillah ◽  
Alessandro Romagnoli ◽  
Ricardo F. Martinez-Botas
Keyword(s):  
High Performance ◽  
Gasoline Engine ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Design Procedure ◽  
Low Pressure ◽  
Operating Conditions ◽  
Exhaust Gases ◽  
Electric Generator ◽  
Turbine Design

In order to enhance energy extraction from the exhaust gases of a highly boosted downsized engine, an electric turbo-compounding unit can be fitted downstream of the main turbocharger. The extra energy made available to the vehicle can be used to feed batteries which can supply energy to electric units like superchargers, start and stop systems or other electric units. The current research focuses on the design of a turbine for a 1.0 litre gasoline engine which aims to reduce the CO2 emissions of a “cost-effective, ultra-efficient gasoline engine in small and large family car segment”. A 1-D engine simulation showed that a 3% improvement in brake specific fuel consumption (BSFC) can be expected with the use of an electric turbocompounding. However, the low pressure available to the exhaust gases expanded in the main turbocharger and the constant rotational speed required by the electric motor, motivated to design a new turbine which gives a high performance at lower pressures. Accordingly, a new turbine design was developed to recover energy of discharged exhaust gases at low pressure ratios (1.05–1.3) and to drive a small electric generator with a maximum power output of 1.0 kW. The design operating conditions were fixed at 50,000 rpm with a pressure ratio of 1.1. Commercially available turbines are not suitable for this purpose due to the very low efficiencies experienced when operating in these pressure ranges. The low pressure turbine design was carried out through a conventional non-dimensional mixed-flow turbine design method. The design procedure started with the establishment of 2-D configurations and was followed by the 3-D radial fibre blade design. A vane-less turbine volute was designed based on the knowledge of the rotor inlet flow direction and the magnitude of the absolute speed. The overall dimensions of the volute design were defined by the area-to-radius ratios at each respective volute circumferential azimuth angle. Subsequently, a comprehensive steady-state turbine performance analysis was performed by mean of Computational Fluid Dynamics (CFD) and it was found that a maximum of 76% of total-static efficiency ηt-s can be achieved at design speed.

Highly Loaded Low-Pressure Turbine: Design, Numerical, and Experimental Analysis

2010 ◽  
Author(s):  
J. T. Schmitz ◽  
S. C. Morris ◽  
R. Ma ◽  
T. C. Corke ◽  
J. P. Clark ◽  
...  
Keyword(s):  
High Speed ◽  
Numerical Solutions ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Free Stream Turbulence ◽  
Low Pressure Turbine ◽  
The Mean ◽  
Highly Loaded

The performance and detailed flow physics of a highly loaded, transonic, low-pressure turbine stage has been investigated numerically and experimentally. The mean rotor Zweifel coefficient was 1.35, with dh/U2 = 2.8, and a total pressure ratio of 1.75. The aerodynamic design was based on recent developments in boundary layer transition modeling. Steady and unsteady numerical solutions were used to design the blade geometry as well as to predict the design and off-design performance. Measurements were acquired in a recently developed, high-speed, rotating turbine facility. The nozzle-vane only and full stage characteristics were measured with varied mass flow, Reynolds number, and free-stream turbulence. The efficiency calculated from torque at the design speed and pressure ratio of the turbine was found to be 90.6%. This compared favorably to the mean line target value of 90.5%. This paper will describe the measurements and numerical solutions in detail for both design and off-design conditions.

The Impact of Blade Loading and Unsteady Pressure Bifurcations on Low-Pressure Turbine Flutter Boundaries

2015 ◽  
Author(s):  
Joshua J. Waite ◽  
Robert E. Kielb
Keyword(s):  
Mode Shape ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Forced Response ◽  
Blade Loading ◽  
Unsteady Pressure ◽  
Aerodynamic Damping ◽  
Low Pressure Turbine ◽  
Reduced Frequency ◽  
The Impact

The three major aeroelastic issues in the turbomachinery blades of jet engines and power turbines are forced response, non-synchronous vibrations, and flutter. Flutter primarily affects high-aspect ratio blades found in the fan, fore high-pressure compressor stages, and aft low-pressure turbine (LPT) stages as low natural frequencies and high axial velocities create smaller reduced frequencies. Often with LPT flutter analyses, physical insights are lost in the exhaustive quest for determining whether the aerodynamic damping is positive or negative. This paper underlines some well known causes of low-pressure turbine flutter in addition to one novel catalyst. In particular, an emphasis is placed on revealing how local aerodynamic damping contributions change as a function of unsteady (e.g. mode shape, reduced frequency) and steady (e.g. blade torque, pressure ratio) parameters. To this end, frequency domain RANS CFD analyses are used as computational wind tunnels to investigate how aerodynamic loading variations affect flutter boundaries. Preliminary results show clear trends between the aerodynamic work influence coefficients and variations in exit Mach number and back pressure, especially for torsional mode shapes affecting the passage throat. Additionally, visualizations of qualitative bifurcations in the unsteady pressure phases around the airfoil shed light on how local damping contributions evolve with steady loading. Final results indicate a sharp drop in aeroelastic stability near specific regions of the pressure ratio indicating a strong correlation between blade loading and flutter. Passage throat shock behavior is shown to be a controlling factor near the trailing edge, and like critical reduced frequency, this phenomenon is shown to be highly dependent on the vibratory mode shape.

Thermodynamic Analysis on Optimum Pressure Ratio Split of Intercooled Recuperated Turbofan Engines

2018 ◽  
Author(s):  
Hualei Li ◽  
Zhiyong Tan
Keyword(s):  
Thermodynamic Analysis ◽  
Explicit Solution ◽  
Waste Heat ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Optimum Pressure ◽  
Solution Function ◽  
Turbofan Engines ◽  
Low Pressure Turbine ◽  
High Pressure Compressor

Intercooled recuperated turbofan engines with high bypass ratio are becoming a research focus in recent years due to its advantages of relatively better fuel economy, lower emission and noise characteristic. The re-heater can recover waste heat in the exhaust gas downstream of the low pressure turbine to reduce the specific fuel consumption, and the intercooler can improve compression ability of the compressors with sufficient temperature difference between the high pressure compressor and the low pressure turbine. An optimal pressure ratio split is often sought to maximize the effect of the intercooler on improving the compression ability of the compressors. To determine an optimal pressure ratio split, different combinations of pressure ratio between high and low pressure spools must be calculated, and this requires huge amount of work with the traditional method to achieve the suitable cycle selections. In this paper, theoretic thermodynamic analysis is carried out to derive an explicit solution of the optimum pressure ratio split for maximizing the efficiency of the whole compression path. The effects of different variables on the optimum pressure ratio split are investigated according to the correlated variables in the solution function. A comparison calculation is also made to validate the effectiveness and accuracy of the explicit solution. The results show that the optimum pressure ratio split can be achieved with the derived solution function, which will significantly simplify the process of the cycle parameter selection.

Aerodynamic Test Results of Controlled Pressure Ratio Engine (COPE) Dual Spool Air Turbine Rotating Rig

2000 ◽  
Author(s):  
Brian D. Keith ◽  
Dipan K. Basu ◽  
Charles Stevens
Keyword(s):  
High Pressure ◽  
Air Force ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Fourth Generation ◽  
Flow Function ◽  
High Pressure Turbine ◽  
Low Pressure Turbine ◽  
Specific Thrust ◽  
Air Force Base

The Controlled Pressure Ratio Engine (COPE) is a fourth generation variable cycle engine combining the attributes of a high temperature turbojet (high dry specific thrust and low Max power SFC) with those of a turbofan (low specific thrust and low part power SFC). Variation in turbine flow function is achieved by the Controlled Area Turbine (CAT) Nozzle concept, which utilizes an innovative cam driven scheme to achieve desired flow function changes while minimizing loss in aerodynamic performance. The single stage high pressure turbine is coupled with a two stage vaneless counter-rotating low pressure turbine. The COPE Turbine System Aero/Heat Transfer Design Validation Program, jointly conducted by GE Aircraft Engines and Allison Advanced Development Company under the direction of the Air Force Research Laboratory at Wright-Patterson Air Force Base, has succeeded in demonstrating advanced turbine technologies that will be utilized on the XTE76, XTE77, and Joint Strike Fighter engines. The various phases of this program evaluated variable area nozzle performance, high pressure turbine performance under the influence of varying flow function, and dual spool testing of the vaneless, counter-rotating low pressure turbine. Evaluation of the three phases demonstrated the aerodynamic capability of these turbine technologies, meeting pre-test predictions in overall and component efficiencies.

Reynolds Number Effects on the Performance of a Turbofan Engine

1989 ◽  
Author(s):  
Masao Kozu ◽  
Satoshi Yashima
Keyword(s):  
Reynolds Number ◽  
Gas Flow ◽  
Pressure Ratio ◽  
Engine Performance ◽  
Low Pressure ◽  
Aerodynamic Characteristics ◽  
Turbofan Engine ◽  
Low Pressure Turbine ◽  
Reynolds Number Effects ◽  
The Difference

Reynolds Number effects on the matching performance of a small twin-spool turbofan engine were investigated through the altitude tests of the F3-30 engine which was developed to power the Japan Air Self Defence Force’s T-4 intermediate trainer. Analyzing the test results made it clear that the change of the aerodynamic characteristics of the low pressure turbine due to Reynolds Number effects is as significant as these of fan and compressor, and it caused the difference between the predicted and measured engine performance at high altitudes. Correlation factors on the Reynolds Number for each of the component characteristics (pressure ratio, airflow and efficiency of fan and compressor, and gas flow and efficiency of low pressure turbine) were obtained, and simulation of the engine performance using these factors coincided well with the test data which were obtained from the altitude tests of the F3-30 at Arnold Engineering Development Center of U. S. Air Force.

Boundary Layer Control on a Low Pressure Turbine Blade by Means of Pulsed Blowing

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Marion Mack ◽  
Reinhard Niehuis ◽  
Andreas Fiala ◽  
Yavuz Guendogdu
Keyword(s):  
Boundary Layer ◽  
Pressure Ratio ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Moderate Amount ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Unsteady Inflow ◽  
Inflow Conditions ◽  
Highly Loaded

The current work investigates the performance benefits of pulsed blowing with frequencies up to 10 kHz on a highly loaded low pressure turbine (LPT) blade. The influence of blowing position and frequency on the boundary layer and losses are investigated. Pressure profile distribution measurements and midspan wake traverses are used to assess the effects on the boundary layer under a wide range of Reynolds numbers from 50,000 to 200,000 at a cascade exit Mach number of 0.6 under steady as well as periodically unsteady inflow conditions. High-frequency blowing at sufficient amplitudes is achieved with the use of fluidic oscillators. The integral loss coefficient calculated from wake traverses is used to assess the optimum pressure ratio driving the fluidic oscillators. The results show that pulsed blowing with fluidic oscillators can significantly reduce the profile losses of the highly loaded LPT blade T161 with a moderate amount of air used in a wide range of Reynolds numbers under both steady and unsteady inflow conditions.

Experimental Investigation of the Effects of Waveform Tip Injection in a Low Pressure Turbine Cascade

2012 ◽  
Author(s):  
Bayram Mercan ◽  
Eda Doğan ◽  
Yashar Ostovan ◽  
Oğuz Uzol
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Flow Direction ◽  
Low Pressure ◽  
Total Pressure Loss ◽  
Wake Flow ◽  
Injection Technique ◽  
Low Pressure Turbine ◽  
Passage Vortex ◽  
Tip Injection

This paper presents the results of an experimental study that investigates the effects of uniform/waveform tip injection along the camberline on the total pressure loss and wake flow characteristics downstream of a row of Low Pressure Turbine (LPT) blades. The experiments are performed in a low speed cascade facility. This injection technique involves spanwise jets at the tip that are issued from a series of holes along the camber line normal to the freestream flow direction. The injection mass flow rate from each hole is individually controlled using computer driven solenoid valves and therefore the flow injection geometrical pattern at the tip can be adjusted to any desired waveform shape, and can be uniform as well as waveform along the camber. Measurements involve Kiel probe traverses for different injection scenarios 0.5 axial chords downstream of the blades as well as Time-Resolved Particle Image Velocimetry (Tr-PIV) measurements at different spanwise locations. Results show that tip injection significantly reduces the total pressure loss levels created by the leakage vortex. Highest overall loss reduction occurs in the case of reversed-triangular injection. The least effective waveform is triangular injection. Loss levels do not seem to get reduced significantly in the passage vortex zone. Velocity, vorticity and turbulence fields created by the passage and leakage vortices get influenced by tip injection. There is significant reduction in the extent of the low momentum zone of the leakage vortex with injection. This effect is much less pronounced for the passage vortex. On the other hand, complex flow patterns are observed within the passage vortex, especially in the case of reversed-triangular injection, such as a possible embedded vortical structure along the passage vortex core, which creates double peaks in the velocity and turbulent kinetic energy fields and complex patterns in Reynolds shear stress.

Numerical and Experimental Investigation of Unsteady Flow Interaction in a Low-Pressure Multistage Turbine

2000 ◽  
Vol 122 (4) ◽  
pp. 628-633 ◽  
Author(s):  
Wolfgang Ho¨hn ◽  
Klaus Heinig
Keyword(s):  
Unsteady Flow ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Grid Method ◽  
Low Pressure ◽  
Navier Stokes ◽  
Viscous Boundary Layer ◽  
Low Pressure Turbine ◽  
Flow Interaction ◽  
Multistage Turbine

This paper presents results of unsteady viscous flow calculations and corresponding cold flow experiments of a three-stage low-pressure turbine. The investigation emphasizes the study of unsteady flow interaction. A time-accurate Reynolds-averaged Navier–Stokes solver is applied for the computations. Turbulence is modeled using the Spalart–Allmaras one-equation turbulence model and the influence of modern transition models on the unsteady flow predictions is investigated. The integration of the governing equations in time is performed with a four-stage Runge–Kutta scheme, which is accelerated by a two-grid method in the viscous boundary layer around the blades. At the inlet and outlet, nonreflecting boundary conditions are used. The quasi-three-dimensional calculations are conducted on a stream surface around midspan, allowing a varying stream tube thickness. In order to study the unsteady flow interaction, a three-stage low-pressure turbine rig of a modern commercial jet engine is built up. In addition to the design point, the Reynolds number, the wheel speed, and the pressure ratio are also varied in the tests. The numerical method is able to capture important unsteady effects found in the experiments, i.e., unsteady transition as well as the blade row interaction. In particular, the flow field with respect to time-averaged and unsteady quantities such as surface pressure, entropy, and skin friction is compared with the experiments conducted in the cold air flow test rig. [S0889-504X(00)02004-3]

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