Micro-turbines for Extending Electric Car Range

The concept of using gas turbines to power a car is not new. In fact, for many decades now, various car manufacturers have experimented with the idea of using either axial or radial gas turbines as the main propulsion of concept vehicles. In the 50’s and 60’s it was Fiat and Chrysler who introduced such concept cars. In those cases, the gas turbine was directly powering the wheels for propulsion. Toyota followed the same concept in the 80’s (Figure 1) [2]. Their concept car utilized a radial turbine in order to propel the vehicle using an advanced electronically controlled transmission system.

Figure 1
Figure 1: Toyota GTV engine [3].
The main advantage of a gas turbine compared with conventional reciprocating (or even rotary) car engines is the fact that it has a much higher power-to-weight ratio. This means that for the same engine weight, a gas turbine is able to deliver much higher power output. This is why aviation was one of the biggest adopters of this technology.

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Different Criteria Options in Turbomachinery Design Software

When people design turbomachines, whether it be a turbine, compressor, blower or fan, they need to find the optimal design based on their criterion under certain constraints.

With AxSTREAM®, people are given several options for their design criteria, which provides flexibility. With that being said, we often get asked what their differences are and here is a brief explanation addressing just that.

The design criteria menu includes power, internal total-to-static efficiency, internal total-to-total efficiency, polytropic efficiency, diagram total-to-static efficiency, and diagram total-to-total efficiency as shown in Figure 1

Figure 1 - Design Criteria Options in AxSTREAM Preliminary Design
Figure 1 – Design Criteria Options in AxSTREAM® Preliminary Design

Power and efficiency are related, but not always the same thing, especially when the boundary conditions are not fixed as design parameters. In AxSTREAM’s Preliminary Design Module, the user can set boundary conditions such as pressure at inlet and outlet, inlet total temperature, etc., as a range instead of a specific value. Along with other parameters, the solver generates hundreds or even thousands of solutions within the range.

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Top 5 Best Practices for Selecting Software for Your Next Turbomachinery Design Project

The airport was bustling with people. The boards were a mixture of delayed and on-time flights. My flight to San Diego for the EUEC Conference was one of the delayed. This happens when you travel as much as I do, so I found a quiet spot to get a few hours of work in while I waited. In the café at JFK, I overheard a conversation between two other detained travelers discussing what they wish they knew before purchasing software tools and/or hiring external consulting companies.

Their pain points were identical to the pain points I’ve encountered in my decade plus years at SoftInWay meeting with design engineers, engineering managers, CxOs, and other non-technical people in my industry (simulation software and R&D of turbomachinery). Over the years, I have used the knowledge gained in my experience to help guide people in making big decisions such as purchasing turbomachinery design software or hiring consultants on a new project and I wanted to share with the blog community as well.

Here are the top 5 Best Practices I suggest everyone use before embarking on their next big software purchase or hiring consultants for their design project.

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A Small Review with a Big Context

This being my last post for 2017, I wanted to do a short review of what we have been discussing this year. During the beginning of the year, I decided to focus on the 3D analyses and capabilities that were implemented in our AxCFD and AxSTRESS modules for fluid and structural dynamics. With that in mind, my posts were tailored towards such, highlighting the importance of the right turbulence modelling for correct flow prediction. Among other topics, we studied the key factors that lead to resonance, the importance of not neglecting the energy transfer between fluid and structure, and the great advantage that increasing computing capacity offers to engineers in order to understand turbomachinery in depth. However, no matter how great the benefits are, the approximations and errors from CFD can still lead to high uncertainty. Together, we identified the most important factors, from boundary conditions all the way to mesh generation and simulation of cooling flows, and we put an emphasis on the necessary development of uncertainty quantification models. This 3D module related topic finished with an extensive article on fatigue in turbomachinery which plays a crucial role in the failure of the machine, and was the cause for many accidents in the past.

AxCFD
SoftInWay’s AxCFD Module

The second part of my posts focused on different industries that rely on turbomachinery as we tried to identify the challenges that they face. Being fascinated by the space industry along with the increasing interest of the global market for launching more rockets for different purposes, I started this chapter with the description of a liquid rocket propulsion system and how this can be designed or optimized using the AxSTREAM platform. Moving a step closer to earth, next I focused on the aerospace industry and the necessity for robust aircraft engines that are optimized, highly efficient, and absolutely safe. One of the articles that I enjoyed the most referred to helicopters and the constant threats that could affect the engine performance, the overall operation and the safety of the passengers. Dust, salt and ice are only a few of the elements that could affect the operation of the rotating components of the helicopter engine, which allows us understand how delicate this sophisticated and versatile aircraft is.
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Gas Turbine Cooling – Enhance Current Advances with SoftInWay

The development of turbine cooling is a process that requires continuous improvements and upgrades. A gas turbine engine is a thermal device and so it is composed of a range of major and minor cooling and heating systems. Turbine cooling is just a small part of the total engine system cooling challenges (combustor system cooling, heat exchangers, casings, bores, compressor and turbine disks, bearings and gears etc.). However, effective turbine cooling consists of the greatest economic factor when it comes to engine development and repair costs, representing up to 30% of the total cost.

As a thermodynamic Brayton cycle, the performance of the gas turbine engine is influenced by the turbine inlet temperature, and the raise of this temperature can lead to better performance and more efficient machines. Current advancements in the development of cooling systems allows most modern gas turbines to operate in temperatures much higher than the material melting point. Of course nothing would have been possible without the parallel development of advanced materials for structural components as well as advances in computing resources and consequently in aerodynamic design, prognostic and health monitoring systems and lifing processes. In particular, as far as the lifing of the machine is concerned, the high pressure (HP) turbine containing the most advanced high temperature alloys and associated processing methods, as well as the combustor which represents the key components that have limited life and tend to strictly dictate the cycles of operation and the allowable time on the wing.

Turbine Cooling Scheme Designed in AxSTREAM NET
Figure 1. Turbine Cooling Scheme Designed in AxSTREAM NET

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Design of Inlet Guide Vane (IGV) for Centrifugal Compressors

All centrifugal compressor designers want to achieve the highest efficiency as well as wide operating range. With this in mind, the inlet guide vane (IGV) is a convenient and economic option for various applications.

IGVs are a series of blades circumferentially arranged at the inlet of compressor, driven electronically or pneumatically.By adjusting the orientation of IGVs, the air flow enters the impeller at a different direction therefore changing the flow behavior while affecting the passing mass flow rate (throttling). This can effectively reduce the power consumption to increase the compressor’s overall efficiency while avoiding surge to provide a better off design working range.

The designer needs to optimize blade profile and positioning of the IGV for efficient operation of a compressor, which can be a tedious job if one does not have a handy tool. Figure 1 shows an example of IGV working on different angles.

Example IGV Characteristic Curve
Figure 1. Example IGV Characteristic Curve

In AxSTREAM, people are able to add IGV component before the centrifugal compressor impeller which can provide different ways to edit its profile such as: Read More

Heat Balance Analysis of Thermal Energy Storage

A primary challenge of meeting the increased demand in energy is that energy supply and accessibility isn’t consistent throughout different geographical areas. Availability of energy sources is considered extremely critical in clean/renewable energy applications such as wind and solar where energy source is quite scarce and unreliable. Thermal energy storage in particular is often being looked into with the universal rise of energy demand from every part of the world. With the help of energy storage technology, it allows any excess of thermal energy to be stored and used at a later time/date where it’s needed.

Energy Storage
Source: http://www.climatetechwiki.org/sites/climatetechwiki.org/files/images/extra/storage.jpg

Thermal energy storage can be achieved with widely diverse technologies, including molten salt application. By heating the salt and storing it in insulated containers, users can pump out the salt to release the heat stored when the energy is needed. For example, with solar application the molten salt stores the excess heat that is produced during the day and releases it at night to produce electricity.
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