Helicopter Mission Analysis for a Regenerated Turboshaft

Abstract

The aim of the study presented in this paper, is to compare helicopters employing simple cycle turboshaft engines, with helicopters employing novel regenerated turboshafts. Two existing helicopter configurations, a Twin Engine Light and a Twin Engine Medium are compared against regenerated configurations. The reference installed engines of both helicopters are notionally optimized by incorporating a heat exchanger, which enables heat transfer between the exhaust gas and the compressor delivery air to the combustion chamber. This process leads to a lower fuel input requirement as well as higher overall thermal efficiency compared to the reference simple cycle engine. The benefits arising from the adoption of the heat exchanger for both configurations are firstly presented by conducting part-load performance analysis for each optimized engine against its reference simple cycle engine. The obtained results suggest substantial reduction in specific fuel consumption for a major part of the operating power range with respect to both helicopter configurations. The results also demonstrate that the heat exchanger effectiveness is a critical parameter in achieving further reductions in specific fuel consumption. The study is further extended to investigate mission fuel burn saving limits for both helicopter configurations under the simulated part-load performance conditions by conducting a heat exchanger tradeoff study. The weight estimation correlation for the heat exchanger is adopted from the previously reported studies of similar fashion and is simulated accordingly for both helicopter configurations. A multi-disciplinary simulation tool with an integrated range of capabilities applicable to helicopter performance evaluation and mission analysis is adopted to simulate various types of missions, targeting wide range of helicopter operations. The results of the mission analysis suggest that the regenerated counterpart configurations are capable of achieving significant reductions in mission fuel burn. However, the level of gain from mission fuel burn savings is dependent on the selected helicopter mission profile, the recuperator design effectiveness as well as the overall evaluation criteria. The results also conclude that while the amount of benefit is dependent on various parameters, there is always an optimum “saving” region for each mission that justifies the need for regeneration.

Energy and Exergy Analysis on a Waste Heat Recovery Module for Helicopters

“…The exhaust gas of a conventional turboshaft carries and dissipates a big amount of heat into the environment [11]. In this module, a PGU is installed after the turboshaft through an evaporator, where part of the exhaust heat will exchange to the organic working fluid and convert into steam under equal pressure (point 2 to 3).…”

“…The exhaust gas of turboshaft engines does not provide power, so it can be used as the heat source of a recuperator, which can preheat compressor discharge air before it enters the combustion chamber [10], [11]. Zhang et al [12] compared the tubular and primary surface recuperators of turboshaft engines by calculating their efficiencies of converting the exhaust heat.…”

Greener Helicopters

“…Variable-speed power turbine technology, which can mitigate severe engine power turbine efficiency decrements at reduced RPM, enabling the rotor to slow down and improve rotor propulsive efficiency by 2-3%, continues to be explored (Welch et al, 2012). A recent study employing heat exchangers and regeneration reported a 35% reduction in mission fuel burn and CO 2 is possible, but results in a two to three times increase in NO x (Fakhre et al, 2013).…”