There are two major reasons reverse engineering is used:
- create replacement parts to maintain the function of older machines;
- improve the function of existing machines while meeting all existing constraints.
Reverse engineering is extremely important in turbomachinery for replacement parts in turbines or compressors which have been operating for many years. Documentation, reports and drawings for a significant amount of these machines is not available due to a variety of reasons, therefore keeping these important machines running is a challenge. One of the options to deal with this issue is to buy the modern analogue of the machine, which is not always feasible due to economic constraints or that there is no replacement available. Reverse engineering of the worn out parts might be the best option in the majority of cases.
In any case, the process to recovery original geometry of the object is the first and major step for all reverse engineering projects, whether you want just replacing/replicate parts or proceed with an upgrade to the machine.
Basic Steps to Any Reverse Engineering Project
Any reverse engineering process consist of the following phases:
- Data collection: The object needs to be taken apart and studied. Starting in ancient times, items were disassembles and careful hand measurements were taken to replicate items. Today, we employ advanced laser scanning tool and 3D modeling techniques to record the required information in addition to any existing documentation, drawings or reports which exists.
- Data processing: Once you have the data, it needs to be converted to useful information. Computers are essential for this stage as it can involve the processing of billions of coordinates of data converting this information into 2D drawings or 3D models by utilizing CAD systems.
- Data modeling: This step was not available in beginning of reverse engineering. People just tried to replicate and manufacture a similar object based on the available data. Nowadays, engineers can utilize digital modelling, which represents all details of the geometrical and operational conditions of the object through a range of operation regimes. Typically, performance analysis and structural evaluation are done at this stage, by utilizing thermo/aerodynamic analytical tool, including 3D CFD and FEA approaches.
- Improvement/redesign of the object: If required, this is the step where innovations can be created to improve the effectiveness of the object based on the collected data about the object’s geometry and operation.
- Manufacturing: After the part is been modeled and meets the design requirements, the object can be manufactured to replace a worn out part, or to provide increased functionality.
Reverse Engineering in Today’s World
It very common to find the situations where reverse engineering is necessary for parts replacement, particularly with turbomachinery – steam or gas turbines, compressors and pumps. Many of these machines have been in operation for many years and experienced damaging effects of use over that time – like water droplets and solid particles erosion, corrosion, foreign objects, and unexpected operating conditions. Besides these expected needed repairs, some other reasons for reverse engineering might arise from a components part failure, as well as part alterations needed due to previous overhauls and re-rates.
All the conditions mentioned above require not only recovering the original geometry but also an understanding of the unit’s history, material properties and current operating conditions.
This article focuses on reverse engineering objects which have experienced significant change in their geometry due to the challenges of long term operation and their shape could not be directly recovered by traditional methods – like direct measurement or laser scanning. Pictures below are examples of such objects – steam turbines blading with significant damage of the airfoils with different causes such as mechanical, water/solid particle erosion, and deposit.
In the situations shown above, recovering the original geometry may be impossible if an engineer only has the undamaged portion of original part to work with. Which means that relying on undamaged portion of an original part it may be impossible to recover the needed portion due to significant level of damage.
Looking at the eroded turbine blading in Figure 1, recovering these airfoils with sufficient accuracy based on only a scan of the original part, would be very difficult, if not impossible, considering that 1/3 to ½ of the needed profile is wiped out by erosion.
In order to recover the full airfoil shape for turbines / compressors / or pumps blading, the information about flow conditions – angles, velocities, pressure, temperature – is required to recreate the airfoils profiles and a complete 3D blade.
In many cases with significant blading damage, the information obtained from aero/thermodynamic analysis is the only source of the information available for a designer and the only possible way to recover turbomachinery blading. In fact, in such a situation, the new variant of the airfoils is developed based on aero/thermodynamic information and by considering the remaining portion of the part, which would be the most accurate representation of the original variant. A structural evaluation should also be performed for any recovered part to ensure blading structural reliability in addition to the aero/thermodynamic study.
All of these engineering steps require employment of dedicated engineering design and analysis tools, which can perform:
- – Accurate modelling of the turbo machinery flow path,
- – 1D/2D aero/thermodynamic analysis and in some cases 3D CFD,
- – Profiling and 3D staking of the blading,
- – Structural evaluation, including 3D FEA tools.
SoftInWay’s team offers a comprehensive set of turbomachinery design and analysis tools within the integrated AxSTREAM® platform, which covers many steps, required for reverse engineering activities.
In Figure 6 below, a process diagram shows how AxSTREAM® products are used for reverse engineering.
After data collection, most of the geometry recovering steps are processed by AxSTREAM® modules:
- – AxSLICE™ to process original geometry data, available from the scanned cloud of points.
- – AxSTREAM® solver to perform 1D/2D aero/thermodynamic
- – AxSTREAM® profiler to recover profile shape and 3D airfoil stacking.
- – AxSTRESS™ for structural evaluation and 3D design.
- – AxCFD™ for detailed aerodynamic analysis and performance evaluation.
Geometry recovered in this way is now ready to be used to develop detailed 3D CAD models and 2D drawings for further technological and/or manufacturing processing.
As an example of such capabilities, Figure 7 demonstrates the reverse engineering process for the 1000 mm last stage of 200 MW steam turbine with significantly damaged blades due to water erosion.
It is possible to recognize and extract the profile angles with a specialized tool – AxSLICE™, obtain slices on the desired number of sections and insert the extracted geometric data to an AxSTREAM® project.
The AxSTREAM® platform can provide seamless reverse engineering process for all components of complex turbomachinery.
Meet an Expert!
Dr. Boris Frolov has over 35 years of experience in steam/gas turbines design, analysis and testing. Earning his PhD in turbine stages optimization with controlled reaction, he is an expert in steam turbines aerodynamics and long buckets aeromechanics. Dr. Frolov has over 50 publications and 7 registered patents and he shares this vast knowledge as a lecturer in steam turbines, gas dynamics and thermodynamics for students studying power engineering sciences. [:]