Energy Advancement Leadership Conference GEMI, UH Engines with no gaseous emission Fazle Hussain, Valery Zimin and Dhoorjaty Pradeep [email protected] Institute of Fluid Dynamics and Turbulence University of Houston Motivation • Improved performance from inherently high-efficiency cycles • Carnot cycle: impractically high compression ratios for even realistic temperature ranges Two cycles with Carnot efficiency: • Stirling cycle (isochoric heat regeneration/isothermal expansion and compression) : also impractical due to very high pressures • Ericsson cycle (isobaric heat regeneration/isothermal expansion and compression) : modest pressure ratios deliver high efficiency; e.g. 87.5% with 2400 K. Alleviating Pollution • Hydrocarbon combustion H20 + CO2 • Chief problem: NOx • Solution: combustion with pure Oxygen Advantages: • No NOx • Temperature restricted by materials alone • Handling of exhausts far easier (a) lower mass flow rate (b) fewer chemical components Cost: • Energy for air separation (not very large) Key features Applications: local power plants, large vehicles, ships Environment: no NOx & CO, CO2 sequestration Thermodynamics: Ericsson cycle, near-Carnot efficiency, high-temp combustion Technology: • separation of N2 and O2 from air, ceramic expansion chamber & heat regenerator • variable torque without gearbox Economics: low construction and maintenance costs, use of low-grade fuels Ericsson cycle p(bar) 100 (1 2) Isothermal compression with water spray injection 3 2 T=300K 50 T=2400K ) g k/ m( v 3 6 3. 5 4 2 7. 0 9 1 4 3. 1 1 7 6. 5 0 1 4 05 K0 0 4 2 = T 4 K0 0 3 = T 3 2 001 ) r a b( p 0 5.67 11.34 90.72 45.36 3 v( m /kg) (2 3) Isobaric expansion in heat regenerator: compressed gas heated by counter-flowing exhaust (3 4) Isothermal expansion achieved by proper timing of fuel injection during combustion in the expansion chamber (4 1) Isobaric compression in heat regenerator due to cooling of the exhaust flow Power plant schematics CH4 , gas 1kg/sec N2 , gas 15kg/sec Air 19kg/sec CO 2 ,liquid 2.75/kg/sec O 2 , gas 4kg/sec Oxygen plant CO2 Engine Liquifyer H2O, liquid 2.25kg/sec CO 2 ,liquid 2.75/kg/sec H2O Less than 0.1% Mass balance is shown for 1kg/sec flux of fuel (CH4) Two emisionless-engine designs: • Vortex Engine: for low-grade fuels (e.g. biomass) • Rotary Engine: for high-grade fuels (e.g. natural gas) Vortex engine for low-grade fuels • Steady-flow combustion engine • Centrifugal forces support pressure difference • Density stratification suppresses turbulence, decreasing thermodynamic irreversibility • No moving parts in high-temp zone ceramics possible • High efficiency direct-contact radiative heat transfer between counter-flowing fluids at different pressures • Intense flow driven by centrifugal convection • Continuous removal of slag from combustion zone • Efficient energy conversion using MHD generator Key components of rotary engine • • • • • • Air separator Isothermal liquid ring compressor Ceramic heat exchanger & expander High-temp isothermal combustor CO2 liquefier Water-spray cooler Liquid-ring compressor 5 6 4 1 - casing 2 – water ring 7 3 – expanding cavity 4 – low pressure 3 8 2 9 10 1 5 – intake port 6 – intake manifold 7 – collapsing cavity 8 – high pressuure 11 9 – stationary collector 10 – exhaust port 11 - exhaust manifold New combustor/expander 1 2 1 - stationary core 3 4 2 - ceramic lining of core 3 – rotor 4 - ceramic lining of rotor 5 5 - sliding vane 6 - stationary cam. 6 Expander operation Back end Front end Beginning of Exhaust Beginning of Intake same time same time End of Expansion End of Exhaust Innovative heat exchanger High-temperature part Key features: • Use of high conductivity ceramics • Designed for only compressive loading on the ceramic components Energy balance • Power from combustion of 1kg/s CH4 at 87.5% thermodynamic efficiency: 43.75 MW • Amount of O2 consumed: 4 kg/s • Power consumed by N2 – O2 separator: 4 MW • Losses due to leakage in expander (estimated at 0.6%): 0.26MW • Loss due to heat flux through ceramic layers of expander (1.1%): 0.48MW • Losses due to leakage in compressor (estimated at 1.2%): 0.53 MW • Power consumed by CO2 liquefier (with recuperation) 0.15 MW • Estimated losses in heat regenerator: 1.8 MW • Other losses (frictional, incomplete combustion…): 0.85 MW • Total available work: 35.68 MW • Energy density of CH4 combustion: 50 MW • Overall plant efficiency: 71.4 % Experimental 10 kW set-up Cool water Rejected water Temperature measurements and control Water pump 2 Electro motor 3 1 Electro motor/ generator Rotary expander Heat exchanger Compressor Electric measurements and control U, V, P, rpm,... 4 CO2 liquifyer Flow measurement & control liquid CO2 Oxygen Methane Carbon Dioxide Summary 1. Use of the Ericsson cycle provides high thermodynamic efficiency 2. Isothermal combustion occurring in this cycle is the most thermodynamically beneficial way to heat the working fluid 3. Cooling by a water spray provides effective isothermal compression 4. Separation of O2 and N2 (from air by an energy-efficient O2 plant) and release of N2 to atmosphere before combustion ensures no NOx in the engine exhaust 5. Use of CO2 as the working fluid allows us to exhaust liquefied CO2. This feature drives down the cost of CO2 separation and permits CO2 sequestration. 6. Use of ceramic tiles (for the inner surface of the combustion chamber and other high-temperature zones of the engine) that makes the engine feasible. 7. The high temperature of combustion and multiple returns of combustion products to the combustion zone prevents CO pollution.