Abstract
In the early 1940s the first practically usable helicopters rose into the sky. Their importance was quickly recognised both by the military and civilian decision makers. A good summary of their most important advantage is the next quotation: “If you are in trouble anywhere in theworld, an airplane can fly over and drop flowers, but a helicopter can land and save your life.” (Igor Sikorsky, 1947) Just after their appearance it immediately became an urgent problem to replace the relatively low-power and heavy piston engines, forwhich the much lighter and more powerful turboshaft engines offered a good alternative. Significant improvement of helicopter engines, which has embodied mainly in power to weight ratio, thermal cycle efficiency, specific fuel consumption, together with reliability and maintainability, of course, has influenced the technicaltactical parameters of helicopters. In this paper I introduce the evolution of helicopter turboshaft engines, the most important manufacturers and engine types. Through statistical analysis I display what kind of performance parameters the helicopter turboshaft engines had in the past and have in the present days.
Highlights
In the early 1940s the first practically usable helicopters rose into the sky
The flight altitude of an average fighter reached 12 km, the special reconnaissance planes could even reach 14 to 15 km. Good example for this process is one of the most well-known fighter plane of World War II, the Messerschmitt Bf 109, which went through numerous development phases
[3] This gas turbine engine is considered to be the ancestor of the shaft power producing gas turbines
Summary
These problems were already well-known even before World War II, airplanes that time did not yet approached these limits. The real reason is that generally higher shaft power needs larger geometric dimensions, which results in better component efficiencies (compressor, combustor, turbine efficiencies, for example due to the relative smaller blade tip clearances) This is even more true if the maximum air consumption is at least 30 kg/s or so like in turbofans. Even the largest engines in this category are small comparing them, for example, to turbofans This fact predetermines the relatively week values of their specific parameters, like specific fuel consumption, specific net work output and specific power, which are important quality indicators. Summarizing the essence of this statistics, usually we can find the following turboshaft engine data: shaft power: 200–3700 kW compressor pressure ratio: 7:1–16:1 mass flow rate: 2–15 kg/s turbine inlet temperature: 1100–1500 K specific fuel consumption: 0.25–0.5 kg/kWh thermal efficiency: 17–32%
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