EU-funded scientists developed a novel 320 kW (429 hp) diesel engine for light helicopters as an alternative to conventional turboshaft engines. The technology demonstrated substantial reductions in fuel consumption and emissions.
Helicopters conventionally employ a turboshaft engine that has a much better power-to-weight ratio compared to diesel engines. However, engine efficiency decreases dramatically with increasing altitude and it requires a large and heavy reduction gear to reduce main rotor speed to desired revolutions-per-minute. The EU-funded project “Diesel engine matching the ideal light platform of the helicopter” (DELILAH) developed a lightweight, high-power diesel engine that can also operate on biofuel.
The technical challenge has been to obtain the power-to-weight ratio taking into account helicopter requirements such as reliability and TBO [time between overhaul]. An optimal diesel engine has been chosen by selection procedure where ratings criteria will be based on performance, weight, size, fuel economy, emissions, multi-fuel capability, reliability, noise, technology, costs, integration, cooling, and drag.
… The engine weight is the crux of the project. The engine configuration has been selected from among several types of engines (in-line, V, opposed-piston, radial, Wankel) and cycle types (two-stroke or four-stroke). The V-8 engine has been defined as the optimal configuration.
The team conducted a multi-criteria analysis to develop the engine with the desired characteristics.Scientists focused on optimizing the design of a turbocharged diesel engine with self-ignition and an electronic control system. Their goal was to achieve substantial reductions in the emission of toxic substances, carbon dioxide (CO2) and noise.
To realize such an engine, the team employed extensive modeling to solve problems related to engine configuration design and integration with the rotorcraft. Scientists analysed the high-dimensional, dynamic, multi-body mechanical system and the adaptive control system to address issues related to vibration, noise, oscillations, engine control and response.
Comparison of flight scenarios demonstrated that the DELILAH optimal turbocharged diesel engine for light helicopters could potentially reduce fuel consumption by 50%. As a result, CO2 emissions were halved with 20x less carbon monoxide production and 229x less soot than conventional turboshaft engines.
The results are fully in line with the environmental impact reductions laid out by the Advisory Council for Aviation Research and Innovation in Europe (ACARE) for the year 2020. The engine is compatible with the use of alternative fuels such as 100% biofuel (B100), reducing dependence on fossil fuels and thus reducing greenhouse gas emissions.