Design and Test of a 10 kW Supersonic Organic Rankine Cycle (ORC) Turbine Generator
Design and test of a 10kW ORC supersonic
turbine generator
OverviewResearchers at Leibniz University Hannover designed and tested a 10 kW supersonic turbine generator as part of an Organic Rankine Cycle (ORC) system. The goal was to recover waste heat from a 12.8-liter diesel engine and convert it into electrical energy using ethanol as the working fluid. The project focused on compact design, high efficiency, and adaptability for automotive and industrial waste-heat recovery.Purpose and Objectives• To improve overall engine efficiency by recovering exhaust heat through an ORC system.• To develop a compact, high-speed turbine-generator unit optimized for low mass flow and high-pressure ratio conditions.• To validate computational fluid dynamics (CFD) models through experimental testing on a dedicated ORC test bench.• To demonstrate variable operation using partial admission control for consistent efficiency across multiple load points.System Description• The ORC cycle uses ethanol (with 5 percent water added for corrosion resistance) as the working fluid.• The ethanol is pressurized, heated, vaporized, and expanded in a turbine to generate power before being condensed and recirculated.• The turbine-generator is a single-stage axial impulse design with supersonic flow expansion.• A compact titanium rotor is directly coupled to a high-speed generator via a shared shaft.• The working fluid enters through a set of Laval nozzles that accelerate the vapor to supersonic speeds before expansion in the rotor.Operating Conditions• Exhaust gas source: diesel engine exhaust at 615 K (342°C).• Working fluid inlet temperature: approximately 539 K (266°C).• Turbine inlet pressure: 40 bar.• Turbine outlet pressure: 0.81 bar.• Mass flow rate: 0.045 kilograms per second.• Rotational speed range: 60,000 to 110,000 RPM.Turbine Design Highlights• Single-stage axial impulse turbine with supersonic expansion.• Eight stator passages designed as Laval nozzles.• Thirty-three rotor blades optimized for impulse flow.• Variable partial admission of 20 to 80 percent to adjust mass flow and efficiency.• Titanium blisk rotor for reduced mass and improved dynamic balance.• Integrated aerodynamic sealing and nitrogen purge system to prevent ethanol contamination.Partial Admission Regulation• Partial admission allows only a fraction of the turbine circumference to be supplied with flow.• It provides adaptable mass flow control and high efficiency under varying load conditions.• Typical configurations include 20 percent, 40 percent, 60 percent, and 80 percent admission.• This technique extends the high-efficiency operating range while maintaining compact size.Test Facility and Methodology• The turbine-generator unit was tested on a dedicated ORC test bench at the University of Hannover.• The bench allows for testing of different working fluids and component configurations.• Measurements include inlet/outlet temperature, pressure, and mass flow.• The generator output was recorded using a precision high-frequency power analyzer.• The setup included bypass control for startup safety and steady-state testing under variable load conditions.Numerical Simulation• CFD simulations were conducted using ANSYS CFX with the SST turbulence model.• Real-gas properties of ethanol-water mixture were modeled using the Aungier-Redlich-Kwong equation of state.• Grid independence studies confirmed accuracy with less than 0.2 percent efficiency deviation.• Simulations predicted supersonic flow regions with Mach numbers exceeding 3 in the stator section.• Empirical models were used to account for losses associated with partial admission.Key Experimental Results• Excellent correlation between experimental and CFD results, with mass flow deviation below 2 percent.• Maximum measured turbine power output: 8 kW at 30 bar inlet pressure with 40 percent admission.• Estimated maximum power output: 19 kW at 80 percent partial admission.• Aerodynamic efficiency ranged between 43.1 and 57 percent depending on operating conditions.• The deviation between measured and predicted efficiency was within ±3.3 percent.• Stable and reliable operation demonstrated at rotational speeds up to 110,000 RPM.Technical Innovations• First demonstration of a compact supersonic ORC turbine generator with adjustable partial admission.• High pressure ratio of up to 49:1 achieved in a single turbine stage.• Use of ethanol-water mixture improved corrosion resistance without performance loss.• Direct coupling of turbine and generator reduced weight and increased reliability.• Aerodynamic face seal with nitrogen purge ensured contamination-free operation.• Validation of numerical simulation techniques for future supersonic ORC turbine development.Conclusions• The project successfully developed and validated a compact 10 kW supersonic turbine-generator suitable for automotive waste-heat recovery.• Experimental results confirmed that the design can achieve over 55 percent turbine efficiency and excellent correlation with CFD predictions.• Variable partial admission proved to be a powerful method for adapting efficiency to variable flow conditions.• The prototype demonstrated the potential for lightweight, cost-effective ORC systems in both mobile and stationary power recovery applications.• The system design can be scaled up or down for a wide range of power levels, from small 1 kW laboratory units to 20 kW commercial prototypes.Future Outlook• Further testing planned for integration into full vehicle-scale ORC waste-heat recovery systems.• Exploration of alternative fluids and advanced sealing techniques.• Potential adaptation for renewable energy use, including geothermal and concentrated solar power.• Continuous refinement of CFD and empirical modeling for supersonic ORC turbines.SummaryThis work demonstrates that a compact supersonic impulse turbine can effectively convert low• to medium-grade waste heat into electricity with high efficiency. The 10 kW ORC turbine-generator unit marks a significant milestone in developing scalable and efficient waste heat recovery systems for automotive and industrial applications.Article Reviewed: J R Seume et al 2017 J. Phys.: Conf. Ser. 821 012023
INFINITY TURBINE LLC We specialize in designs, plans, licensing, consulting, design services, and surplus spare parts. We no longer manufacture turbines or CO2 systems. More Info...
TEL: +1-608-238-6001 (Chicago Time Zone ) USA
Email: greg@infinityturbine.com
The Six-Year Wall:
Why AI Data Centers
Can't Get Power—
And Who Just Cracked the Problem Hyperscalers are racing to deploy gigawatts of AI compute, but the grid can't keep up and large gas turbines are backordered half a decade out. Infinity Turbine's Cluster Mesh Supercritical CO₂ system offers a radical alternative: modular, silent, trailer-deployable prime power that scales the way software does... More Info
Data Center 40 MW to 100 MW Using IT1000 Supercritical CO2 Gas Turbine Generator Silent Prime Power 1 MW (natural gas, solar thermal, thermal battery heat) ... More Info
Developing Rack Prime Power DC for AI Server Racks Sidecar 48V to 800V DC plus DC buffer for hyperscalers... More Info
The Shift from AC to DC Power Production for AI Data Centers AI data centers are pushing electrical infrastructure to its limits. The traditional AC power chain is no longer optimal for GPU-driven workloads. A DC-native architecture using Infinity Turbine’s Cluster Mesh system offers a path to higher efficiency, lower costs, and scalable modular power—potentially saving tens of millions per year at hyperscale... More Info
SMR and Cluster Mesh Supercritical CO2 Power System for Data Centers and AI Pairing Cluster Mesh Supercritical CO2 Power System with Small Modular Reactors enables hyperscalers to convert high-grade nuclear heat into ultra-efficient, dispatchable power with a compact, modular footprint tailored for AI-scale demand. More Info
ORC and Products Index Infinity Turbine ORC Index... More Info
________________________________________________________________________________
CONTACT TEL: +1-608-238-6001 (Chicago Time Zone USA) Email: greg@infinityturbine.com
(Standard Web Page) | PDF