Chapter 3
How Conventional Gas Turbines Work
Gas turbines are among the most important machines ever developed for modern civilization. They generate electricity for millions of homes, propel commercial aircraft across continents, power naval vessels, and drive countless industrial processes. Their ability to convert the chemical energy stored in fuel into mechanical power and electricity has made them indispensable for more than seventy years. Although engineers have continuously improved their performance, the fundamental operating principle of gas turbines has remained largely unchanged since the middle of the twentieth century. Understanding how these machines work provides the foundation for appreciating why the compressor-free hydrogen turbine developed by researchers at the Karlsruhe Institute of Technology (KIT) represents such a revolutionary advancement.
At its core, a gas turbine is an energy conversion machine. It transforms the energy stored in fuel into rotational mechanical energy and, ultimately, electrical energy. This transformation occurs through a carefully coordinated sequence of air compression, fuel combustion, and expansion of hot gases. Every component within the turbine has a specific role, and each stage depends on the successful operation of the previous one.
The operation begins with air entering the front of the turbine through an intake system. Unlike internal combustion engines found in automobiles, which operate in repeated cycles, gas turbines function continuously. Air flows into the machine without interruption, allowing a constant supply of oxygen for combustion. Large filters remove dust, debris, and other contaminants that could damage the turbine blades or reduce efficiency.
Once the air enters the turbine, it reaches one of the most critical components—the compressor. The compressor is responsible for increasing the pressure of the incoming air before it enters the combustion chamber. Modern gas turbines use axial compressors consisting of multiple rows of rotating and stationary blades. As air passes through these stages, its pressure gradually increases while its volume decreases. Depending on the turbine’s design, the compressor may increase air pressure by twenty to forty times its original atmospheric pressure.
Compressing air requires enormous amounts of energy. The rotating compressor is directly connected to the turbine by a central shaft, meaning that part of the turbine’s mechanical output must be used simply to keep the compressor operating. In many industrial gas turbines, approximately half of the energy produced by the turbine is consumed internally to compress the incoming air. This represents one of the largest inherent efficiency losses in conventional turbine systems.
The reason for compressing air is rooted in the principles of thermodynamics. High-pressure air allows fuel to burn more efficiently and at much higher temperatures. Increased pressure also enables the expanding combustion gases to perform more work as they pass through the turbine blades. Without compression, combustion would be weaker, and the turbine would generate significantly less power. For decades, engineers accepted this energy penalty because no practical alternative existed.
After compression, the high-pressure air enters the combustion chamber, where fuel is injected through precisely engineered nozzles. The fuel mixes with the compressed air in carefully controlled proportions to create an efficient combustible mixture. An ignition system initiates combustion during startup, but once the turbine reaches normal operating conditions, the continuous flow of fuel and air sustains the flame without further assistance.
Inside the combustion chamber, chemical energy stored in the fuel is released as heat. Temperatures can exceed 1,500 degrees Celsius, creating an extremely hot, high-pressure stream of gases. These gases expand rapidly as they move toward the turbine section. Modern combustion chambers must withstand extraordinary thermal stresses while maintaining stable combustion under constantly changing operating conditions. Advanced cooling systems and heat-resistant materials are essential to prevent damage to these components.
The hot gases then enter the turbine itself. The turbine consists of multiple stages of specially designed blades mounted on a rotating shaft. As the expanding gases flow over the blades, they transfer their energy by causing the shaft to rotate at extremely high speeds, often exceeding 10,000 revolutions per minute in industrial systems and much higher in aircraft engines. The faster the gases expand, the greater the mechanical energy transferred to the rotating shaft.
Part of this rotational energy is immediately redirected back to the compressor through the common shaft. This mechanical connection allows the compressor to continue drawing in fresh air and maintaining the continuous combustion process. The remaining energy becomes useful output. In power plants, the rotating shaft drives an electrical generator that converts mechanical energy into electricity through electromagnetic induction. In aircraft engines, much of the energy produces thrust by accelerating exhaust gases out of the engine at high speed.
The electrical generator attached to a gas turbine operates according to one of the most fundamental principles of physics. As the turbine shaft rotates, it spins powerful magnets inside coils of wire or rotates wire coils within a magnetic field. The changing magnetic field induces an electric current, producing the electricity that flows through transmission lines to homes, businesses, hospitals, and industries. This process can occur continuously for months with proper maintenance, making gas turbines highly reliable sources of power.
Gas turbines can operate using a variety of fuels. Traditionally, natural gas has been the preferred fuel because it burns cleanly compared to coal and produces relatively low emissions. Other fuels include diesel, kerosene, biofuels, and synthetic fuels. Increasingly, engineers are adapting gas turbines to burn hydrogen, either alone or blended with natural gas, as part of efforts to reduce carbon emissions. Each fuel requires careful adjustments to combustion systems because different fuels ignite, burn, and release heat at different rates.
One of the greatest strengths of gas turbines is their flexibility. They can start relatively quickly compared to coal-fired power plants and can rapidly adjust their output to match changing electricity demand. This makes them particularly valuable for supporting renewable energy systems. When clouds reduce solar power generation or winds suddenly weaken, gas turbines can increase electricity production within minutes, helping stabilize the electrical grid.
Combined-cycle power plants further improve gas turbine efficiency by utilizing waste heat that would otherwise be lost. After leaving the turbine, the hot exhaust gases still contain significant thermal energy. Instead of releasing this heat directly into the atmosphere, combined-cycle plants use it to produce steam, which drives a separate steam turbine connected to another electrical generator. This approach can increase overall plant efficiency from approximately 35–40 percent for a simple gas turbine to more than 60 percent for advanced combined-cycle facilities.
Despite these impressive achievements, conventional gas turbines still face important limitations. The compressor remains the largest single consumer of internally generated power. Engineers estimate that approximately half of the turbine’s mechanical energy may be required to operate the compressor alone. This means only the remaining portion is available for producing electricity or propulsion. Reducing or eliminating this energy loss has long been considered one of the most desirable goals in turbine engineering.
Another limitation involves the large number of moving components within conventional turbines. Compressors contain numerous rotating blades, bearings, seals, and shafts that operate under extreme temperatures and mechanical stresses. Over time, these parts experience wear, requiring regular inspections, maintenance, and replacement. The complexity of compressor systems also increases manufacturing costs and contributes to the overall weight and size of the turbine.
Environmental concerns present another challenge. Although natural gas turbines emit less carbon dioxide than coal-fired power plants, they still contribute to greenhouse gas emissions when burning fossil fuels. As countries pursue net-zero carbon goals, cleaner alternatives are becoming increasingly important. Hydrogen offers one such alternative because its combustion produces primarily water vapor rather than carbon dioxide. However, simply replacing natural gas with hydrogen does not eliminate the efficiency losses associated with mechanical compression.
This is where the breakthrough achieved by the Karlsruhe Institute of Technology becomes particularly significant. Rather than accepting the compressor as an unavoidable component, KIT researchers developed a turbine that creates the required pressure inside the combustion chamber itself. Through a process known as pressure-gain combustion, carefully controlled detonation waves generate the pressure that conventional turbines obtain through mechanical compression. By removing the compressor, the new design has the potential to reduce energy losses dramatically, simplify mechanical systems, and improve overall efficiency.
The concept represents one of the most fundamental changes in gas turbine design in decades. Instead of consuming a large fraction of its own power to compress air, the turbine allows the combustion process itself to generate the necessary pressure. This innovation could enable future turbines to produce more electricity from the same amount of hydrogen fuel while reducing maintenance requirements and mechanical complexity.
Understanding the operation of conventional gas turbines highlights why this new technology has attracted worldwide attention. The compressor has always been viewed as an essential component, yet it also represents one of the greatest barriers to achieving higher efficiency. Eliminating it was once considered nearly impossible. The success of the KIT research team demonstrates that long-standing engineering assumptions can be challenged through scientific innovation, opening new pathways toward cleaner, more efficient power generation.
In the next chapter, we will examine the remarkable breakthrough achieved by the Karlsruhe Institute of Technology in greater detail. We will explore how years of research led to the world’s first successful compressor-free hydrogen turbine capable of generating electricity and why this achievement may influence the future of power plants, industrial energy systems, and even aviation.
