Applications of an Interactive Balancing Procedure for Gas Turbines and Other Turbomachinery

Least squares balancing methods have been applied for many years to reduce vibration levels of turbomachinery. This approach yields an optimal configuration of balancing weights to reduce a given cost function. However, in many situations, the cost function is not well-defined by the problem, and a more interactive method of determining the effects of balance weight placement is desirable. An interactive balancing procedure is outlined and implemented in an Excel spreadsheet. The usefulness of this interactive approach is highlighted in balancing case studies of a GE LM5000 gas turbine and an industrial fan. In each case study, attention is given to practical aspects of balancing such as sensor placement and balancing limitations.

High Power, High Pitch Velocity Gear Box Failures in Oil Production Fields

This Paper describes continuation of efforts to improve the low reliability of the high power, high pitch velocity gear boxes. These gear boxes are located in oil and gas production facilities (OAGPF) and serve to transmit the power from gas turbine drivers to large, two or three case turbo compressor trains. Life expectancy of these gear boxes did not meet predicted life expectancy of typical high speed, high energy gear boxes. This paper deals with various modifications of these gear boxes which were necessary to improve very low, initial 34% reliability. The series of modifications improved gear boxes life expectancies, however they never reached desired goal that is at least 10 years of continuous service without gear elements failures.

Turbo Gas Power Plants Performance Evaluation for Putting Into Commercial Operation

In order to evaluate the performance of new turbo gas power plants for putting in commercial operation, it was necessary to supervise, test and, if so the case, to approve the works of commissioning, operational and acceptance of all equipments and systems that constitute the power plant. All this was done with the aim of guaranteeing the satisfactory operation of these elements to accomplish the function for which they were developed. These activities were conducted at the request of the customer to confirm and observe that the evidence of the tests was carried out according to the specifications and international regulations. The putting into commercial operation activities were done in collaboration with the supplier and manufacturer of equipment, the client and the institution responsible for certification and approval of the plant. All this in a logical and chronological order for the sequence of commissioning tests, operation and acceptance. Commissioning tests were carried out on-site at normal operating conditions, according to the design and operation needs of each power plant of a group of 14. Once the commissioning tests were completely executed and in a satisfactory manner, operational tests of the plants were developed. This was done by considering that they must operate reliable, stable, safe and automatically, satisfying at least, one hundred hours of continuous operation at full load. After evaluating the operational capacity of the machine, it was necessary to determinate the quality of the plant by carrying out a performance test. Finally, it was verified if every unit fulfills the technical requirements established in terms of heat capacity of the machine, noise levels and emissions. As a result of this process, it is guaranteed to the customer that the turbo gas power plants, their systems and equipments, satisfy the requirements, specifications and conditions in agreement with the supplier and manufacturers referring to the putting into commercial operation of the plant.

Alstom GT11N2 M Expansion Turbine Design Modification and Operation Experience

This paper summarizes the development steps and measures taken for the upgrade of the GT11N2 Turbine. The main targets to be achieved were specified as follows: - GT power increase; - GT gross efficiency increase; - Flexible operation with respect to power output and service interval length. All 4 turbine stages were re-designed in order to optimize their aerodynamic performance and minimize cooling air consumption. Turbine aerodynamic efficiency improvement was achieved by means of: - Turbine stage-to-stage loading optimization; - 3D airfoil profiling; - Replacement of the damping bolt of blade 4 by a full shroud; - Stator/rotor sealing optimization. On top of that, cooling air consumption was reduced by means of cooling system optimization for Vane 1, Blade 1, Vane 2, Blade2 and SHS/A. This allowed an increase of TIT (inlet turbine mixed temperature) keeping the hot gas temperature at the turbine inlet unchanged, which is important for meeting lifetime and emission targets. One of the key requirements for this Turbine Upgrade was to use exclusively validated design approaches and design features as available from existing and proven Alstom Gas Turbines ([1], [2], [3]) in order to minimize development- and implementation risks. Manufacturing of the new turbine parts was completed in an exceptionally short time, thanks to a dedicated R&D Logistic and Manufacturing support/process, an efficient NCR (Non Conformance Report) process, early supplier involvement and a very close/open work with suppliers. The first prototype of this turbine was implemented in a GT11N2 customer engine. Performance validation runs, performed in May 2008 confirmed that the design targets for power and efficiency were fully met. The validation of the turbine parts lifetime is still ongoing.

Aerodynamic Design and Numerical Investigation on Overall Performance of a Micro Radial Turbine With Millimeter-Scale

For millimeter-scale microturbines, the principal challenge is to achieve a design scheme to meet the aerothermodynamics, geometry restriction, structural strength and component functionality requirements while in consideration of the applicable materials, realizable manufacturing and installation technology. This paper mainly presents numerical investigations on the aerothermodynamic design, geometrical design and overall performance prediction of a millimeter-scale radial turbine with rotor diameter of 10mm. Four kinds of turbine rotor profiles were designed, and they were compared with one another in order to select the suitable profile for the micro radial turbine. The leaving velocity loss in micro gas turbines was found to be a large source of inefficiency. The approach of refining the geometric structure of rotor blades and the profile of diffuser were adopted to reduce the exit Mach number thus improving the total-static efficiency. Different from general gas turbines, micro gas turbines are operated in low Reynolds numbers, 104∼105, which has significant effect on flow separation, heat transfer and laminar to turbulent flow transition. Based on the selected rotor profile, several micro gas turbine configurations with different tip clearances of 0.1mm, 0.2mm and 0.3mm, respectively; two different isothermal wall conditions; and two laminar-turbulent transition models were investigated to understand the particular influence of low Reynolds number. These influences on the overall performance of the micro gas turbine were analyzed in details. The results indicate that these configurations should be included and emphasized during the design process of the millimeter-scale micro radial turbines.

Heat Transfer on a Turbocharger Under Constant Load Points

The processes occurring in turbo machinery applications are frequently treated as adiabatic. However, in a turbocharger significant heat transfer occurs, leading to a deficit of turbocharger performance. The overall objective of this experimental work is to improve the understanding of the heat transfer process taking place in a turbocharger when installed on an internal combustion engine. In order to do this, beyond the standard set of measurements needed to define the turbo operating point, a large number of thermocouples were installed on the turbocharger. The tests results allow the quantification of the temperatures within the turbocharger and revealed that a nonuniform temperature distribution exists on the compressor and turbine casings. This is partly attributed to the proximity of the turbocharger to the engine. This process plays a role on the deterioration of the compressor efficiency when compared to the corresponding adiabatic efficiency. A correlation that allows the calculation of the compressor exit temperature is proposed. The method uses the surface temperature of the bearing housing; it was validated against experimental data with deviations no larger than 3%. A simplified 1-dimensional heat transfer model was also developed and compared with experimental measurements. The algorithms calculate the heat transferred through the turbocharger, from the hot end to the cold end by means of lump masses. The compressor performance deterioration from the adiabatic map is predicted.

Research and Development of Minitype Twin-Bladed Air Turbine

In order to improve the machining efficiency of ultra-precision and micro fabrication technology, a high speed spindle is essential for the minitype tools widely applied in systems such as PCB drilling machines, micro fabrication machines, dental handpieces, etc. To realize the high speed performance, the air driven turbine is verified to be more feasible than the electromagnetic actuator. Furthermore, the operational efficiency and quality of the high speed spindle are significantly influenced by the turbine blades and the bearings respectively. Through detailed configurational studies and performance analyses on diverse minitype turbine blades, we have derived the efficiency- and quality-influential parameters. And based on optimization results, we have developed a novel type of twin bladed air turbine (TB-air turbine), which consists of two parallel blades with an angular offset. The offseted twin blades can efficiently and smoothly transform pneumatic energy into rotational energy. Therefore, steady driving force and less dynamic unbalance are able to be easily achieved for reducing nervous disturbances such as vibration, noise, and wear. By applying finite element analytical method, the operational performances and quality of the new developed twin bladed air turbine such as rotational speed, torque, vibration and noise were analyzed for comprehending influences of the design parameters and the operational parameters. While the inlet angle, the blade shape and its geometric parameters are the dominant design parameters; the inlet pressure and mass flow rate, and the outlet pressure are the main operational parameters. Through the turbine blades, the pneumatic energy will be transformed into operational energy in form of the flow field and the pressure distribution and the energy loss in form of turbulence. Also by integrating knowledge of production technology, a neat design of the turbine blades suitable for automatic manufacturing process is developed. And furthermore, through an elaborate layout of the flow guiding, a minimum rotational runout can be effectively achieved without any complicate and costly dynamic balancing process. Consequently, it has significantly depressed the stream noise and raised the operation lifetime of bearings. According to our experimental verification, the vibration and the stream noise of our TB-air turbines are 60% and 50% lower than traditional counterparts respectively. Our developed minitype spindle with novel TB-air turbine can efficiently realize high speed rotation with high torque, less vibration and less noise.

Coanda Surface Geometry Optimization for Multi-Directional Co-Flow Fluidic Thrust Vectoring

The performance of Co-flow fluidic thrust vectoring is a function of secondary flow characteristics and the fluidic nozzle geometry. In terms of nozzle geometry, wall shape and the secondary slot aspect ratio are the main parameters that control the vector angle. The present study aims to find a high quality wall shape to achieve the best thrust vectoring performance, which is characterized by the maximum thrust deflection angle with respect to the injected secondary air. A 3D computational fluid dynamics (CFD) model is employed to investigate the flow characteristics in thrust vectoring system. This model is validated using experimental data collected from the deflection of exhaust gases of a small jet-engine integrated with a multi-directional fluidic nozzle. The nozzle geometry is defined by the collar radius and its cutoff angle. In order to find the best value of these two parameters, Quasi-Newton optimization method is utilized for a constant relative jet momentum rate, a constant secondary slot height and insignificant step size. In this method, the performance index is described as a function of thrust deflection angle. Optimization parameters (wall geometric parameters) are estimated in the direction of gradient, with an appropriate step length, in every iteration process. A good guess of initial optimization parameters could lead to a rapid convergence towards an optimal geometry and hence maximum thrust deflection angle. Examination over a range of geometric parameters around the optimum point reveals that this method promises the best performance of the system and has potential to be employed for all the other affective factors.

Optimization of the Part-Load Control Strategy for a Two-Shaft Microturbine With Intercooling, Reheat and Recuperation

Microturbines have become popular among small-scale distributed energy systems. This paper focuses on a two-shaft arrangement where high efficiency is obtained through intercooling, reheat and recuperation. An optimized method for controlling the part-load performance via variable speed control of the generator shaft in addition to the turbine inlet temperature reduction is presented. The studied methods to reduce the power output were variable speed control of the generator shaft in combination with independent turbine inlet temperature control of both turbines. Optimization was performed by using a differential evolutionary algorithm to find a sufficient number of points at steadily reducing power settings to determine the optimal control curves for the three control parameters. In the microturbine model the operating values of the engine were obtained by solving the system of nonlinear equations formed by the governing relations. As a result an optimal part-load control method was found which provides better part-load efficiency than any of the studied control methods alone or in simple combinations could have provided. The optimal control strategy and the relative change of part-load electric efficiency were shown to be fairly independent of the design-point specifications for the turbomachinery and recuperator.

Feasibility Study of a Recuperated Turboshaft-Engine Based on a Micro-Gasturbine

The present paper shows the current state of a feasibility study of the University of Applied Sciences Esslingen. The intention of this study is the conversion of a model-turbine into a turboshaft-engine for variable applications, with as few as possible modifications. The shaft power of the engine is estimated on 20 kW at least. It is intended to use a recuperator to augment its efficiency. After a general introduction possible applications are discussed and the previous design-process is explained: Subsequent to the concept-phase cycle parameters were calculated and the power turbine was designed and manufactured. At present turbine tests are running. The recuperator is of counter flow type. To shorten the flow path it is mounted directly around the combustor. Currently different variations are being designed which will be optimised. The pressure loss within the exhaust manifold between power turbine and recuperator has already been reduced by simulations and tests. This will be minimised through application of a genetic optimisation software.